1. Switched on to TENS (OBSTETRICS)
Published in: Your Pregnancy, April/May 2005
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SWITCHED ON TO TENS THE INS AND OUTS OF TRANSCUTANEOUS ELECTRICAL NERVE STIMULATION (TENS) PAIN RELIEF

Treatment with TENS consists of attaching pads to your back. A low voltage electric current is passed across these pads and this stimulates your body to produce its own natural pain-relieving substances. It takes about 30 minutes before an effect is felt. The pain relief achieved is usually assessed as moderate, and is sometimes inconsistent. For some women it is of considerable value. As labour progresses the intensity of the electrical stimulation can be increased to cope with the increased pain of contractions, but frequently stronger pain relief may be required.

IS IT SAFE?
TENS is non-invasive and has few side effects when compared with drug therapy. The most common complaint is an allergic-type skin reaction (about 2% of patients) and this is almost always due to the material of the electrodes, the conductive gel or the tape used to hold the electrodes in place.

WHAT DOES IT LOOK LIKE?
TENS units consist of a small machine with controls (about the size of a cell phone), connected by wires to electrode pads placed appropriately to alleviate various types of pain. Some units are battery-operated and small enough to carry in hand or in a pocket.

HOW DOES IT WORK?
Most TENS units operate in two modes, a burst or pulse mode for chronic or low-level pain, and a constant mode for acute, short-lived pain (such as a labour contraction). When turned on, the TENS unit delivers a tingly, buzzing sensation to the area under the electrodes. It is thought that this sensation works in two ways to alleviate labour pain: it causes your body to release natural pain killers called endorphins, and it acts as a gateway, blocking deeper pain messages from traveling to your brain.

DOES IT WORK?
TENS will not completely eradicate labour pain in the way that an epidural does. Like water therapy, relaxation and breathing techniques and medicated pain relief, TENS can lessen the pain and make it easier to tolerate. Used in combination with other methods, it is even more likely to help. TENS can be helpful to get through the early labour until the point when you may or may not consider having an epidural.

2. Transcutaneous Electrical Nerve Stimulation (OBSTETRICS)
Published in: Exercises in Pregnancy and Childbirth
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This chapter introduces the concepts of Transcutaneous Electrical Nerve Stimulation (TENS). It describes the advantages of TENS and its use during labour and discusses the criteria relevant when selecting a particular unit.
Transcutaneous electrical nerve stimulation (TENS or TNS) has been used as a particular method of pain relief for many years and is widely used today, particularly for chronic pain and pain associated with terminal illness. More recently it has been used for more, acute pain and found to be of advantage (Woolf 1999). In 1983 Spembly manufactured a TENS unit especially designed for use in labour. This was the first unit of its type in the UK and is called the Obstetric TENS (see Figure 7.1). Since then, other manufacturers have adapted existing models with varying degrees of success. Criteria for selection of an effective unit appear later in the chapter.
TENS is a low-frequency current applied to the skin via pairs of electrodes. These can be placed over the painful area or over the nerve routes supplying the area of pain. The current produces a tingling sensation, the intensity (strength) of which can be altered by the individual. The pulsed low-frequency modality encourages the release of cerebrospinal endogenous opiates (endorphins and encephalins) which are the body’s own natural pain-relieving agents and these raise the individual’s pain threshold (Thompson 1989). The obstetric model differs in that it has a high-frequency modality which, when activated, brings in a continuous high-frequency current to boost the low-frequency current to give added pain relief. It is thought that this higher frequency current works in the pain-gate theory and lessens the pain impulses received by the brain (Wall, 1985). The high-frequency modality is brought into play by pressing a patient-demand switch and stopped by pressing it once more.

ADVANTAGES OF TENS IN LABOUR

  • Self-regulated/self-administered
  • Releases the body’s own pain-relieving agents
  • Non-invasive, drug-free
  • No drowsiness – user remains alert and co-operative
  • No known side effects
  • Allows freedom of movement and any position
  • Does not alter the course of labour
  • Can be stopped at any time
  • Can be used in conjunction with any other forms of pain relief.

There are no side effects from TENS and no depression of respiration (Woolf 1999) – a pacemaker in situ being its only contradiction to it's use. It is safe, non-invasive therapy which, if required, can be used in conjunction with other forms of pain relief as labour progresses. TENS does not give a pain-free labour and this fact must be stressed to the woman and her partner. However, for the woman who wishes to be in control of her pain relief it is a useful addition to other analgesia. The general feeling among midwives is that TENS users who choose to have additional analgesia require lower doses than those who are not using TENS.

This is supported by Kaplan et al (1998) who described TENS as being an effective non-pharmacological and non-invasive adjuvant pain relief modality for use in labour and delivery. They claimed that not only did the use of TENS reduce the amount of analgesic drugs, but also slightly reduced the duration of the first stage of labour. However Carroll et al (1997) claimed that randomized controlled trials provided no compelling evidence for TENS having an analgesic effect during labour. TENS can be used during suturing and to relieve after pains as well as during labour itself. TENS works best for women who apply it early in labour as it takes about 40 minutes for the endorphins to be maximally released (Salar et al 1981). It can help the woman to cope in the early latent phase before labour is fully established. It has been shown that the levels of pain and distress-related thoughts during the latent phase of labour were predictive of the length of labour and obstetric outcomes (Wuitchik et al 1989). If a woman is going to have labour induced, it is suggested that she activates the TENS unit on the low-frequency mode 30-40 minutes before the procedure is commenced. When she feels in need of further pain relief, she can activate the high-frequency mode at the start of the contraction and use for the duration of the contraction, returning to the low-frequency mode at the end.

ELECTRODES
For labour, four electrodes, which are of sufficient length to cover the nerve roots supplying the uterus and cervix (T10 – L1) and the birth canal and pelvic floor (S2 – S4), are required. The recommended size of the electrodes is 10cm x 4cm, and they can be of different materials. The original and most economical electrodes are made of carbon-impregnated rubber, which needs a coupling medium of gel under the complete surface to ensure continuous contact with the skin. More recently, the disposable electrodes have been introduced which are applied to a wet skin and are self-adherent. A third type (supplied with hire units) has a very sticky self-adhesive surface and in theory can be re-used a few times, but in practice this is not recommended for reasons of hygiene and because the electrodes become less adhesive.

SITING THE ELECTRODES
The woman should sit on the edge of the bed, whilst her partner stands behind on the other side of the bed. She should have her arms relaxed by her side and her back exposed down to the gluteal cleft.
The area from the level of the bra strap down to the gluteal cleft should be washed and dried to remove any natural skin grease that could impede the electrical current. The electrodes are attached to the leads making sure no metal is exposed. To site the upper two electrodes, the T10 vertebra is palpated. The easiest way of locating this is to feel for the inferior angle of the scapula with the little fingers of each hand, then reach across to the spine at the same level with the thumbs.
The vertebra palpated by the thumbs will be T7, count the three vertebrae down to find T10. (A good guide is the lower border of the bra clips in most women). The upper borders of one set of electrodes should be fixed at the level of T10 about 2cm either side of the thoracic spine (approx 5cm apart), with the leads hanging downwards. If the re-usable carbon electrodes are being used, they should be thoroughly covered with the conducting gel supplied and held in place with a piece of Mefix, large enough to cover both electrodes.
The top of the second pair of electrodes is placed at the level of the sacral dimples (S2) with the lower borders reaching down to just above the gluteal cleft. The leads should point upwards. The electrodes should not be placed on the abdomen as there may be a slight chance of interference on the fetal monitor if a scalp electrode is in use. It has been reported that interference has been noted occasionally when both sets of electrodes are placed dorsally, but this has been with older monitors and disappears when the intensity of the TENS is reduced.

With both sets of electrodes in place and checked and the unit switched off, the plug end of each lead is inserted into the sockets on the top of the TENS unit. The woman should know which electrodes are attached to which control so she can increase the intensity of each channel independently.
A much better effect is achieved of the woman is in complete control of the unit from the start. Once the electrodes are in place, the TENS unit can be clipped on to her clothes and she can remain active or adopt any position she wishes.
The intensity (strength) of the two channels can be increased as required using the relevant intensity control). The frequency of the pulses, which is a personal choice, can also be varied by altering the rate control. The frequency of the pulses, which is a personal choice, can also be varied by altering the rate control. This does not affect the intensity of the output, only the rate of the pulses.
The manufacturers of the Spembly TENS unit advise an initial frequency of 7 on the dial, then further adjustment to meet the personal needs of each individual. However, some TENS units have a pre-set unalterable frequency. Ideally women and their partners should be introduced to the TENS unit during the antenatal classes.
Then if they are interested in trying or applying it, a group or individual session can be arranged where the women can experience its sensation on their back sand their partners practice siting the electrodes. The sensation on the back is usually preferred to that on the forearm and women like to feel it before going to the expense of hiring a unit.

TENS HIRE
Unless a delivery suite has sufficient units to allow women to take one home just prior t their expected delivery date, hiring their own is often preferred. He hired units will include the easy-to-apply, self-adhesive electrodes which do not require gel.
There will be two pairs for use in labour and generally, depending on the company, an additional pair for practice in the two weeks prior to birth. Various companies supply units for hire and costs depend on the package offered. Hire contracts vary between four and six weeks with nearly all companies offering a free extension period as long as they are notified in advance.
The more expensive hire charges include a demonstration video, spare batteries and prepaid return packaging. Obstetric TENS units are for use in labour only and should not be used for anything else. Their use is contraindicated before 37 weeks of pregnancy because of the slight risk of preterm labour. Some delivery suites hire out their own units, but this can be an onerous undertaking.
A new battery and electrodes are needed for each user and the unit should be checked after its return to the labour suite before being re-issued.

CRITERIA FOR SELECTION OF A TENS UNIT
Midwives and health visitors should be aware of the different models on the market before giving out literature to couples. The cheapest deal is not necessarily the best option. Crothers (1992) tried out two different units during her own labour and decided that certain criteria were important.
She was a member of the working party of The Association of Chartered Physiotherapists in Obstetrics and Gynecology (now Women’s Health) who devised the following criteria for the sustainability of TENS equipment for use in labour:

  • Sufficient intensity/amplitude to relieve pain
  • Scope to alter the frequency
  • Both pulsed and continuous mode
  • Additional amplitude with continuous mode
  • Simple and easy to apply and operate
  • Correct instructions for placing the electrodes
  • Press/release booster button, not press/hold
  • Electrodes to measure a minimum of 10cm x 4 cm
  • Separate intensity control for each pair of electrodes
  • Durable electrodes, leads and attachments
  • Transmission gel must be suitable for adequate conduction with carbon electrodes

All units should conform to safety standard BS 5724.

TENS FOR POST-CAESAREAN DELIVERY
Following caesarean section, where the mother is not offered self-administered pain relief via Cardiff pump or an epidural, TENS may be used for post-operative pain relief. It has been found that women who used TENS after caesarean births required less narcotic analgesia and so were better able to cope with their babies (Hollinger 1986). The electrodes are usually placed above a Pfannenstiel incision towards the outer sides of the abdomen as this is where most pain is felt.
One set of electrodes only may be applied, or a second pair may be placed either side of the first and second lumbar vertebrae. The low-frequency mode is all that necessary at rest, but, if the mother needs to cough or move about, the high-frequency can be used as during contractions.
The UKCC’s advice with regard to midwives using TENS is contained in the following Registrar’s Letter 8/1991:
“The Council has accepted the recommendation and its Midwifery Committee that midwives may, on their own responsibility, manage pain relief in labour by the use of transcutaneous nerve stimulation (TNS) provided that:
1. they have received adequate and appropriate instruction, which is a matter to be determined by agreed local policy and
2. safety standards conform to those laid down by the Department of Health Medical Devices Directorate in England, or equivalent body in Scotland, Wales or Northern Ireland. The current standard for all medical equipment is set out in British Standard specification BS 5724 Part 1 1989”.

REFERENCES
Carroll D, Tramer M, McQuay H et al 1997 Transcutaneous electrical nerve stimulation in labour pain: a systematic review. British Journal of Obstetrics and Gynaecology (2):169-175
Crothers E 1992 TENS in labour. Journal of the Association of Chartered Physiotherapists in Obstetrics and Gynaecology 70:26
Hollinger J L 1986 Transcutaneous electric nerve stimulation after caesarean birth. Physical Therapy 66:36
Kaplan B, Rabinerson D, Lirie S et al 1998 Transcutaneous electric nerve stimulation (TENS) for adjuvant pain-relief during labour and delivery. International Journal of Gynaecology and Obstetrics 60(3):251-255
Salar G, Job I, Mingrino S et al 1981 Effect of trancutaneous electrotherapy on CSF beta endorphin content in patients without pain problems. Pain 10:169-172
Thompson J W 1989 Pharmacology of Transcutaneous Electrical Nerve Stimulation (TENS). Journal of the Intractable Pain Society of Great Britain and Ireland 7:33-40
Wall P D 1985 The discovery of transcutaneous electrical nerve stimulation. Physiotherapy 71:348-350
Woolf C J 1999 Trancutaneous and implanted nerve stimulation. In: Wall P D, Melzack R (eds) Textbook of pain. Churchill Livingstone, Edinburgh
Wuitchik M, Bakal D, Lipshitz J 1989 The clinical significance pain and cognitive activity in latent labour. Obstetrics and Gynaecology 73:35-42

Further reading
Wall, P D Melzack R, (eds) 1990 Textbook of Pain. Churchill Livingstone, Edinburgh.

3. PAIN RELIEF: A practical guide to obstetric TENS machines (OBSTETRICS)
Published in: British Journal of Midwifery
September 2000, Vol 8, No 9
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By Sally Price Sally Price RM
BSc NNEB is
Practice Development
Midwife at North Bristol
NHS Trust

Most midwives working in today’s maternity services will be familiar with Transcutaneous Electrical Nerve Stimulation (TENS) as a form of pain management in labour. Many maternity units provide this facility, but it is also likely that women may hire a TENS machine to use before they are admitted to hospital or for a home birth. Midwives may encounter a range of TENS machines, each with their own distinctive features. This article will examine some of the TENS machines currently available for hire and discuss the implications for practice.

BACKGROUND
The TENS machine has been described as a portable hand-held box containing a battery-powered generator which transmits electrical pulses. A low voltage electrical current is transmitted to the skin using surface electrodes covered in contact gel, resulting in a tingling sensation (Hawkins 1994). By positioning the surface electrodes at T10-L1 and S2-S4 levels of the spinal cord, stimulation can be provided to address the pain of both the pain of both the first and second stages of labour.
Women are able to modify the level of electrical pulses to suit their own requirements. A boost button is available to increase both the intensity and frequency of the stimulation during a contraction.
TENS machines are believed to work in two ways:
- Based on Melzack and Wall’s gate theory of pain (1988), TENS is thought to stimulate nerve pathways, decreasing the ability of transmission cells to carry messages of pain to the brain
- TENS stimulate the release of endorphins from the brain which have a pain-relieving action.

The main advantages of TENS machines are that women are firmly in control, able to move freely and remain mobile, and can use other forms of pain relief in addition to TENS if necessary. Critics would argue that there is no evidence to support the use of TENS as an effective form of pain relief. Indeed, a systematic review of randomized controlled trials suggests that it has no significant effect on pain in labour (Carroll et al, 1997).
However, as Coates (2000) rightly points out, this ignores the views of women who use TENS. A study of over 10 000 women evaluating their views after experiencing TENS in labour, found favourable reports of satisfaction, with 91% of respondents stating that they would use TENS again (Johnson, 1997). Perhaps it would be more appropriate to view TENS not as a form of pain-relief, but as a method for women to self-manage their pain.

HIRING A TENS MACHINE
For women who choose to manage their pain with TENS, the optimal time to commence use is in early labour, before hospital admission. This early use will promote the cumulative effect of endorphins, building up the body’s pain tolerance levels. Women will require easy access to a TENS machine to gain maximum benefit. Many women choose to borrow or hire a machine from their local maternity unit from about 37 weeks of pregnancy. In some areas this service may be so popular that demand out-strips availability. This may result in women hiring TENS machines from other sources.
The Obstetric TENS TENS machine is available to hire direct from Spembly Medical, at a cost of £26.99 for 5 weeks. The hire period can be extended at no extra cost if the baby is overdue.

The hired machine is supplied with four self-adhering electrodes, although should maternity units wish to purchase this machine, reusable rubber electrodes are available. The TENS TENS machine is dual channeled, allowing each pair of electrodes to be individually adjusted in terms of frequency and power, in response to the site and degree of pain. A separate boost button is available to give a 10% lift in power for extra pain relief during a contraction.

BabiTENS by Rehablicare UK Ltd is available to hire direct, or through Boots at a cost of £27.50 for a month. It is available from 3 weeks before the EDD, and should the baby not be born within the hire period, this can be extended free of charge. BabiTENS has four self-adhesive electrode pads, and a hand-held boost button, separate to the pocket-sized generator box. The rate control or frequency of the pulse can be adjusted, giving a faster or slower pulse. The width control, which operates the duration of the pulse, can also be adjusted to give an increased area of deeper stimulation. The instruction leaflet for users is comprehensible. Particularly useful is the table that indicates some possible causes and solutions to potential problems.
The freedom TENS unit by Shire Design is available to hire from Lloyd’s Pharmacy at a cost of £27.50 for 6 weeks. The hire package includes the TENS hand-held unit, two self-adhesive transvertebral electrodes, instructions for use and an information video. The Freedom unit has an interesting feature, making it different to the other types of machines, by having one integral control panel. It is small and comfortable to hold in the hand, avoiding the need for a separate generator box and boost button. Women may view this as advantageous, since there is less equipment for them to manage. By having only two transvertebral pads, the pulse rate cannot differ from the T10-L1 and S2-S4 levels. Very tall women may find two pads are not sufficient to achieve the coverage they require.

IMPLICATIONS FOR MIDWIVES
Midwives may, on their own responsibility, manage pain relief in labour by the use of TENS, providing they have received adequate instruction, and safety standards conform to those laid down by the Department of Health (UKCC, 1991).
All TENS machines should conform to British standard 5724. If midwives are to advise women appropriately, it is important that they familiarise themselves not only with the evidence base on the use and effectiveness of TENS machines, but also the different types available. This is particularly important in areas where women are hiring TENS machines of a type that the midwife is unfamiliar with.
Midwives should advise women intending to use TENS in labour to become thoroughly accustomed to both the application of the electrode pads and the operation of the machine itself.
What is perhaps more relevant is for midwives to inform women of the need to ensure that electrodes are correctly applied. Incorrect application may reduce the effectiveness of the TENS machine (Coates, 1998). Each of the hire services mentioned above provide written information, with Freedom and TENS supplying a video, but this may not be a substitute for the professional expertise of the midwife.
Should midwives have concerns about the safety of a particular TENS machine, either one that the client has hired, or one provided by the maternity unit, they should immediately advise discontinuation of use. If possible, the midwife may offer a substitute machine.

CONCLUSION
TENS are widely available and commonly used by women in labour. This article examines three types of TENS machine offered for hire, but midwives may wish to research what is available within their own areas of practice. Given the variety of machines, it is essential that midwives become familiar with different types and their functions, if they are to give appropriate advice, and assist women to use TENS machines to their maximum effect.

REFERENCES
Carroll D, More RA, Tramer MR et al (1997) Transcutaneous electrical nerve stimulation does not relieve labour pain: updated systematic review. Contemp Rev Obstet Gynecol 9(3): 195-205
Coates T (2000) MIDIRS comments (TENS). MIDIRS Midwifery Database, London
Coates T (1998) Transcutaneous electrical nerve stimulation: TENS. Practical guidance on application. Practis Midwife 1 (11): 12-14
Hawkins J (1994) Use of TENS for pain relief in labour. Br J Midwifery 2(10): 487-90
Johnson MI (1997) Transcutaneous electrical nerve stimulation in pain management. Br J Midwifery 5(7): 400-5
Melzack R, Wall PD (1988) The challenge of Pain. 2nd edn. Penguin Books, London
UKCC (1991) Registrars letter. Amendment – Transcutaneous nerve stimulation

4. Use of TENS for pain relief in labour (OBSTETRICS)
Published in: British Journal of Midwifery,
October 1994, Vol 2, No 10
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By Joyce Hawkins
Joyce Hawkins is Midwifery Sister at Glan Clwyd Hospital, Clwyd, North Wales.

This article examines the effectiveness of transcutaneous electrical nerve stimulation Machines (TENS) in relieving labour pains, and describes two case studies where the machines were used.

For the past 3 years, I have been the co-ordinator of a scheme, run by Glan Clwyd Hospital, Clwyd, North Wales, which loans transcutaneous electrical nerve stimulation (TENS) machines to pregnant women, free of charge. The machines are non-invasive, easy to use and provide an effective method of pain management which can be discontinued quickly if necessary.
The TENS unit consists of a portable hand-held box containing a battery-powered generator which transmits electrical impulses. A low-voltage electrical current is transmitted to the skin using surface electrodes which are first covered with contact gel. This results in a ‘buzzing’ or ‘tingling’ sensation. The labouring women may vary the intensity of the electrical impulse transmitted by the TENS machine and the frequency of stimulation, thus increasing or decreasing the sensation as she wishes.
The concept of using TENS or electrical impulses as a form of analgesia is not new. The use was first recorded some 2000 years ago by the Roman physician Scribonium Largas. He applied electric eels to haemorrhoids, arthritic joints, headaches and the feet of gout sufferers.

Further research allowed clinicians to advance their knowledge and by the 20th century, electrical equipment such as the cardiac pacemaker was in use. The development of electronics enabled scholars to research its use for pain relief. As Wall (1978) states:

"The development of modern electronics made it possible to search the spinal cord for the cells which were receiving the nerve impulses delivered by the sensory peripheral afferent fibres which had detected injury"

It was this research that allowed Melzack and Wall to formulate the Gate Control Theory in 1985. The theory can be broken down into four main points:
1. Nerve impulses from injured tissue excite dorsal horn neurons, which are called transmission cells.
2. Transmission cells carry the messages to reflex circuits and the brain.
3. Stimulation of low threshold, sensory nerve fibres excite the inhibitory interneurones which decreases the messages being transmitted by the transmission cells.
4. Stimulation of the long descending nerve pathways further excites the inhibitors interneurones and the messages of the transmission cells are again limited (Melzack and Wall, 1988).
TENS is believed to work by closing the gate and reducing the amount of pain felt. It is also believed to stimulate the release of the body’s natural narcotics, endorphins. Sweet (1992) defined endorphins as one of a group of opiate-like peptides produced naturally by the body, which modulate the transmission of pain preceptors interneurones, thereby raising the pain threshold to produce sedation and euphoria.

RELIEF OF LABOUR PAIN BY TENS
Bevis (1989) concludes that the correct positioning of the TENS unit, by either the midwife or the woman’s partner is critical. The pads should be place in a position that allows the electrical impulses to travel to the point at which transmission cells receive the pain messages from the tissues. The nerve supply of the uterus passes the two thoracic nerves (T11 and T12) via the paracervical plexus, which is responsible for transmitting the pain of cervical dilation.
During the latter part of the first stage of labour, T10 and the first lumbar nerve L1 are also involved with the sacral nerves S2, S3 and S4 which accept the impulses form the pudendal nerve caused by the stretching of the pelvic floor (Bevis, 1989). The first pair of electrodes should thus be placed between T10 and L1, with the remaining pair being placed 3cm apart on either side of the spine.

MIDWIVES’ RESPONSIBILITIES
The safety of any form of analgesia is of prime importance to the woman and midwife. In 1991, the UKCC ruled that midwives could use TENS machines to relieve pain in labour, on their own responsibility. This should be in accordance with the Midwives Rules (1991, UKCC) which were updated in 1994. These state:

"A practicing midwife shall not on her own responsibility, administer any medicine which includes analgesia, unless in the course of her training, or as a midwife, she has been thoroughly instructed in its use and is familiar with its dosage or application."

All midwives at Glan Clwyd Hospital are trained in the use of TENS and each year the company updates them on any new developments. Two case studies will be described. Both cases demonstrate the effectiveness of TENS as no other analgesia was used.

CASE STUDY 1
Aprimigravida contacted me when she was only 26 weeks pregnant. She had read about the use of TENS in labour from the bounty antenatal pack which was given to her by her community midwife. She was eager to see and try the machine and wanted to book one early enough to be sure that she got what she termed “The Magic Box”. I entered her name, address and telephone number in the TENS booking book and asked her to contact me again at 38 weeks gestation to arrange a demonstration collection. A hospital confinement was booked. The pregnancy continued normally, receiving care shared between consultant unit, a community midwife and the family practitioner. At 38 weeks gestation, I was contacted and arranged a visit to collect the machine and to give them instructions on how to use it. We discussed the birth plan and talked about what she wanted in labour.
Flexibility in communications between the midwife and the couple was important, while not opposing any intervention deemed necessary during labour if there was a problem. Labour started spontaneously at 40 weeks, which was not the expected date. The main symptom was excruciating backache which seemed to be present all the time. The TENS pads were applied using the contact gel. It was found that sitting in a big armchair padded with cushions, pressing the boost button when the backache reached its peak, gave very good relief. The boost dial only went to four, the maximum being 10. After 4 hours, the backache became much easier. The contractions were every 2-10 minutes, but were not felt abdominally. It became easier for her to walk around.
After a further hour at home a show was evident. She called the delivery suite, where the nurse advised her to make her way to the hospital. A vaginal examination revealed the cervix to be fully dilated. The membranes were left intact as requested, since it was hoped they would rupture spontaneously. Intermittent auscultation with a Pinard’s stethoscope had been documented on the birth plan. Cardiotocography was not used. One hour after admission, a healthy boy was delivered spontaneously, Apgar 9/10, birth-weight 3.5 kg. There was a small 2° perineal tear which was sutured with Dexon after infiltrating the perineum with 5ml of 1% lignocaine local anaesthetic.
What part had TENS played? The response was encouraging. The choice of analgesia had worked well. It had given adequate pain relief especially early in the first stage of labour when the back pain seemed to be constant. It had given security, a longer period of time in the woman’s own home, control over the intensity of the contractions, and mobility. Although too early to think of future labours, the choice would be the same. It has been completely satisfactory.

CASE STUDY 2
I was asked to demonstrate and advise on the use of a TENS machine. It was worth trying as this was the woman’s fourth pregnancy, and she had tried most other forms of analgesia. During her first labour, which had lasted 16 hours, her pain was mercifully relieved by epidural anaesthesia.
For the birth of her second baby, she had tried an intramuscular injection of pethidine in an attempt to achieve complete euphoria; other expectations were of a short labour. The labour lasted 11 hours, without the desired effect. This was accompanied by a jerking feeling when going to sleep, strange dreams and labour pains.
For labour number three, she chose meptazinol 150mg with promethazine 25mg. This dosage was repeated 4 hours later. The total duration of the labour was 9 hours. Each confinement had been booked for a consultant obstetric unit and all three babies were born normally. So, on reflection, of all three labours a good explanation was given antenatally on choice of analgesia, and an informed choice had been made. Anxiety was expressed regarding the use of opiates and the effect they would have on the baby’s respiratory system. The lack of mobility was the only criticism of the epidural.
Our free loan scheme of TENS appealed very much. A preference was expressed for the community midwife to give instructions on its use. A ‘domino’ delivery was arranged.
Labour started at 41 weeks gestation. The community midwife was called and remained throughout the labour and delivery. The TENS machine was applied immediately, with contractions 1-15. Four hours passed before admission to hospital when, on vaginal examination, the cervix was 8cm dilated. One and a half hours later, a normal delivery resulted in the birth of a live boy weighing 4.23kg. The perineum was intact although the baby was the heaviest of the four. Previous deliveries had required perineal repair.
We discussed at length why she thought the TENS machine had been so good. Again, security, mobility and control were mentioned. She also stated that the controls kept her very busy getting the frequency ‘just right’.

KEY POINTS
- TENS offers another form of analgesia, which is drug-free.
- It gives women increased confidence in their own ability to cope with labour, by giving them complete control over the situation.
- The woman has longer in her own surroundings, which ensures greater relaxation as well as increasing her mobility.

CONCLUSION
Not all women have used TENS alone for pain relief in labour. Some women have complemented its use with Entonox or one of the intramuscular opiates of their choice, perhaps just for the latter part of the first stage of labour, this worked well.
It is important to have success stories of women who have benefited totally throughout their labour using only TENS, to relate to other women considering its use. It is also important to have good liaison with community midwives, so that the woman and her partner do not receive conflicting advice.
A central point and a familiar name are crucial for contact and collection. Our present system works well for this very popular form of analgesia. I have been a practicing midwife for 25 years and have experienced many changes in the types of analgesia used for labour.
My experience is that TENS is by far the most popular at the present time.

REFERENCES
Bevis R (1989) Pain Relief and Comfort in Labour: In: Miles Textbook for Midwives. Edinburgh Churchill Livingstone, London: 177-91
Melzack R (1987) Low back pain during labour. Am J Obstet Gynecol 155: 901-5
Melzack R, Wall PD (1965) Pain mechanism: a new theory. Science 150 (3699): 971-9
Melzack R, Wall PD (1988) The Challenge of Pain 2nd edn. Penguin Books, London
Simkin P, Dickinson K (1986) Non-pharmacological use of drugs in labour. In: Chalmers I, Enkin M, eds. Effective Care Pregnancy and Childbirth 2 Oxford University Press: 893-5
Sweet WH (1980) Pain: a general discussion. In: Bonica JJ, ed. Addiction of Pain. Raven Press, New York: 379-80
Wall PD (1978) The Gate Control Theory of Pain Mechanism. In: Textbook of Pain 2nd edn. Churchill Livingstone, Edinburgh: 165-93
Wall PD (1985) Discovery of TENS. Physiotherapy 71(8): 348-50
UKCC (1994) Code of Professional Conduct for Nurses, Midwives and Health Visitors. UKCC, London

5. Transcutaneous Electrical Nerve Stimulation in Pain Management (OBSTETRICS)
Published in: British Journal of Midwifery
July 1997, Vol 5, No 7
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By Mark I Johnson
Mark I Johnson is Senior Lecturer in Human Physiology, Faculty of Health and Social Care,
Leeds Metropolitan University.

Abstract
Transcutaneous nerve stimulation (TENS) is an analgesic technique used in clinics worldwide. However, its potential value for pain control in labour is often overlooked. The purpose of this study was to evaluate patients’ views after experience with TENS in labour.
A questionnaire (12 multiple choice questions) was distributed to 17 896 parturients in the UK who had used TENS to manage labour pain. The questionnaire was completed and returned by post within the 2 weeks following delivery by 10 077 women.
The survey was analysed using descriptive statistics and it was found that 71% of the 10 077 respondents reported ‘excellent’ or ‘good’ relief of labour pain by TENS and 91% would use TENS again in the future. However, 81% of parturients who completed the questionnaire reported receiving additional analgesics during labour and it is therefore impossible to determine whether analgesic effects were directly due to TENS alone.
Of the 14% of respondents who completed labour without additional analgesia 1187 (83%) reported ‘excellent’ or ‘good’ pain relief. Although one must be cautious in the interpretation of the results of a postal survey, the favourable reports of satisfaction while using TENS supports a possible role for TENS as an adjuvant in the management of labour pain.

Trancutaneous electrical nerve stimulation (TENS) is a non-invasive, non-pharmacological analgesic method, with potential advantages for pain control in labour (Woolf and Thompson, 1994). Obstetric use of TENS was pioneered by Augustinsson et al (1977) who reported that labour pain was reduced in 88% of 147 women when applied to lumbar areas of the spinal cord, areas corresponding to the input of nociceptive afferents associated with first and second stages of labour (T10-L1 and S2-S4 respectively).
Although reports claim that TENS can markedly reduce labour pain the majority of studies have not been conducted under placebo-controlled conditions (Bundsen et al, 1978; Kubista et al, 1978; Robson, 1979; Stewart, 1979; Miller Jones, 1980; Vinceti et al, 1982; Grim and Morey, 1985; Davies, 1989). In contrast, the results of placebo-controlled studies have failed to find significant reductions in labour pain during TENS (Nesheim, 1981; Merry, 1983; Harrison et al, 1986; Thomas et al, 1988). This has led to resistance in the use of obstetric TENS by the medical fraternity, although midwives, physiotherapists and patients continue to promote its value. Moreover, many manufacturers market TENS units which provide a dual channel output allowing simultaneous stimulation at T10-L1 and S2-S4 sites and a ‘boost’ control for contraction pain which will switch the pattern and intensity of stimulation from a low intensity/low frequency (burst mode) stimulation to a high intensity/high frequency (continuous mode) stimulation.
The purpose of the study was to assess the views of a large number of patients after experience with TENS in labour. Although the study was unable to investigate putative analgesic effects of TENS, it would provide useful information on patient satisfaction with TENS.

METHODS
The survey was performed over a 2-year period during which ‘TENS and labour’ multiple choice questionnaire (12 closed questions – see Tables 1, 2 and 3) was distributed in collaboration with Spembly Medical to 17 896 parturients living in the UK. All women had independently approached Spembly Medical for the hire of the TENS unit at a cost of £30.00 per month. The women were instructed to complete the questionnaire within 1 week following childbirth.
The use of obstetric TENS during delivery was supervised by a health-care professional.

FINDINGS
Of the 17 896 women who received the questionnaire, 10 077 returned a completed questionnaire with the hired TENS unit within 2 weeks following delivery (56.3% response rate). Non-respondents either returned the hired unit without the questionnaire or with an uncompleted questionnaire. The results of the questionnaire are summarized in Tables 1, 2 and 3. Of the women who returned the questionnaire 6733 were primiparas, 2506 were multiparas and the number of previous births were not known in 838 women (Table 1). Over 40% of respondents reported that they received no further instructions on the application of TENS from health-care professionals and had to rely on the guidelines given in the Rental Plan Users Guide. Back pain was reported by 6276 of 10 075 respondents (62%) although the severity of this pain was not recorded. It was not possible to distinguish the relative effects of TENS on first and second stage labour pain.

Out of the 10 077 (91%) paturients who replied to the questionnaire, 9160 said they would use TENS again in labour (Table 2). TENS was reported to provide ‘excellent’ or ‘good’ relief of pain by 7122 (71%) respondents and ‘poor’ relief by 648 (6%). However, 8645 (86%) of parturients who replied to the questionnaire reported that they had received additional analgesics (entonox, pethidine, epidural) during labour. Hence, it was not possible to attribute the positive reports of pain relief to TENS alone. Nevertheless, 1432 (14%) of partutrients who replied to the questionnaire completed labour without additional analgesia and 1187 (83%) of these women reported ‘excellent’ or ‘good’ pain relief (Table 2).
Only 936 (9%) respondents were not confident in TENS efficacy before labour, and of these 580 (62%) reported ‘excellent’ or ‘good’ pain relief and 818 (87%) would use TENS for labour again. Only 39% of parturients reported that they administered TENS within the first hour of labour and 52% reported that they did not administer TENS continuously throughout labour (Table 3).

DISCUSSION
This survey has found that 9160 out of 10 077 (91%) parturients who replied to the questionnaire would use TENS again to manage labour pain. These results are consistent with those of Davies (1989).
The finding that 7122 out of 10 077 (71%) parturients reported ‘excellent’ or ‘good’ relief of labour pain with TENS should be viewed with caution, as 86% of these patients received additional analgesics. However, of the 1432 parturients who received TENS without additional analgesics, a similar proportion reported ‘excellent’ or ‘good’ relief (83%). This suggests that some degree of pain relief occurred during TENS administration, although whether this was due to true analgesic effects or to a placebo response cannot be determined. The percentage of women requiring additional analgesia is similar to that found by Harrison et al (1986) who reported that 88% of primigravidae receiving active TENS required additional analgesia during labour. Previous studies have failed to find any significant differences in either pain report or analgesic requirements of parturients receiving active vs. placebo TENS (Nesheim, 1981; Harrison et al, 1986; Thomas et al, 1988). However, these studies found that women were more satisfied with the active TENS treatment than with the placebo TENS.

Despite the apparently positive findings it is important to apply caution in the interpretation of the results. The rate of return of questionnaires was 56.3% and it would be interesting to examine the views of the non-respondents. All women made a financial investment for the hire of the TENS unit which may have influenced the patients retrospective view of treatment outcome. It is impossible to determine the contribution of TENS to the pain relief experienced during labour because of the lack of placebo control. Psychological variables and placebo response could be major factors which may have influenced the patients report of pain relief. This is supported by a number of controlled studies which have failed to find significant changes in pain relief during labour between active TENS and placebo TENS (Nesheim, 1981; Merry, 1983; Harrison et al, 1986; Thomas et al, 1988). Although many workers have claimed that TENS relieves labour pain, the majority of studies were either uncontrolled (Augustinsson et al, 1977; Bundsen et al, 1978; Kubista et al, 1978; Robson, 1979; Stewart, 1979; Grim Morey, 1985; Davies, 1989) or were controlled but lacked a placebo group (Miller Jones, 1980; Vincenti et al, 1982; Bundsen et al, 1981; 1982). Thus, due to the conflicting nature of the literature it is important that further double-blind placebo-controlled studies are performed.
All women in the present study had prior knowledge of TENS effects and were motivated to use TENS during labour, Of the parturients who replied to the questionnaire, 9132 (91%) had confidence in the analgesic efficacy of TENS before use and this high level of expectancy may have had a marked effect on treatment outcome. However, of the 936 respondents who were non-confident in TENS effects before labour 580 (62%) reported ‘good’ or ‘excellent’ pain relief and 818 (87%) would use TENS again. Furthermore, previous studies have failed to find relationships between prior expectations of the effects of TENS and the outcome of treatment in populations of chronic pain patients (Johansson et al, 1980; 1981; Reynolds, 1983; Johnson et al, 1993).

KEY POINTS
- A survey was conducted to investigate the experiences of over 10 000 women using transcutaneous electrical nerve stimulation (TENS) for labour.
- A total of 71% of respondents reported ‘excellent’ or ‘good’ pain relief with TENS and 91% reported that they would use TENS again in the future.
- The favourable reports of satisfaction support a role for TENS in the management of labour pain.

CONCLUSION
In conclusion, the favourable reports of TENS effects in the present study by a large number of parturients support a role for TENS as an adjuvant in the management of labour pain. Although placebo-controlled studies suggest that the effects of TENS during labour may be partly do to placebo, it is apparently from this study that many parturients find comfort in TENS use. As TENS is safe to both mother and newborn (Bundsen and Ericson, 1982) and uncontrolled studies suggest that it may reduce analgesic intake (Miller Jones, 1980), it seems that its use should not be precluded. Furthermore, TENS can be administered by the parturient without a health-care professional and may be particularly advantageous before labour and during the journey to the hospital, when medical intervention and additional analgesics may not be available. The need for more placebo-controlled studies to examine obstetric use of TENS remains.

I wish to thank Mr Mark Gilliland of Spembly Medical for his help in the design and distribution of the questionnaire. I also wish to thank Professor JW Thompson and Professor CH Ashton for their assistance in preparing the manuscript.

REFERENCES
Augustinsson LE, Bohlin P, Bundsen P et al (1977) Pain relief during delivery by transcutaneous nerve stimulation. Pain 4: 59-65
Bundsen P, Carlsson CA, Frossman L, Tyreman NO (1978) Pain relief during labour by transcutaneous electrical nerve stimulation. Prakt Anaesth 13: 20-8
Bundsen P, Peterson L, Selstam U (1981) Pain relief in labour by transcutaneous electrical nerve stimulation. A prospective matched study. Acta Obstet Gynecol Scand 60: 459-68
Bundsen P, Ericson K (1982) Pain relief in labour by transcutaneous electrical nerve stimulation. Safety aspects. Acta Obstet Gynecol Scand 61: 1-5
Bundsen P, Ericson K, Peterson L-K, Thiringer K (1982) Pain relief in labour by transcutaneous electrical nerve stimulation. Testing a modified stimulation techniques and evaluation of the neurological and biochemical condition of the newborn infant. Acta Obstet Gynecol Scand 61: 129-36
Davies R (1989) An evaluation of transcutaneous nerve stimulation for the relief of pain in labour. J Assoc Chartered Physiotherapists Obstet Gynecol 65: 2-7
Grim LC, Morey SH (1985) Transcutaneous electrical nerve stimulation for relief of parturition pain. A clinical report. Phys Ther 65: 337
Harrison RF, Woods T, Shore M et al (1986) Pain relief in labour using transcutaneous electrical nerve stimulation (TENS). A TENS/TENS placebo controlled study in two party groups. Br J Obstet Gynaecol 93: 739-46
Johansson F, Almay BGL, Knorring L von, Terenius L (1980) Predictors for the outcome of treatment with high frequency transcutaneous electrical nerve stimulation in patients with chronic pain conditions. Pain 9: 55-61
Johansson F, Almay BGL, Knorning L von (1981) Personality factors related to the outcome of treatment with transcutaneous nerve stimulation. Psychiatria Clin 14: 96-104
Johnson MI, Ashton CH, Thompson JW (1993) A prospective investigation into factors related to patient response to transcutaneous electrical nerve stimulation (TENS): the importance of cortical responsitivity. Eur J Pain 14: 1-9
Kubista E, Kucera H, Riss, P (1978) The effect of transcutaneous nerve stimulation on labour pain. Geburtschilfe Frauenheilkd 38: 1079-84
Merry AF (1983) Use of transcutaneous electrical nerve stimulation in labour. NZ Med J 96: 695-6
Miller Jones CMH (1980) Transcutaneous nerve stimulation in labour. Anaesthesia 35: 372-5 Nesheim BI (1981) The use of transcutaneous electrical nerve stimulation for pain relief during labour. Acta Obstetricia et Gynecologica Scandinavica 60: 13-16
Reynolds AC, Abram SE, Anderson RA et al (1983) Chronic pain therapy with transcutaneous electrical nerve stimulation: predictive value of questionnaires. Arch Phys Med Rehabil 64: 311-13
Robson JE (1979) Transcutaneous electrical nerve stimulation for pain relief in labour. Anaesthesia 34: 357-60
Stewart P (1979) Transcutaneous electrical nerve stimulation as a method of analgesia in labour. Anaesthesia 34: 361-4
Thomas IL, Tyle V, Webster J. Neilson A (1988) An evaluation of transcutaneous electrical nerve stimulation for pain relief in labour. Aust NZ J Obstet Gynaecol 28: 182-9
Vincenti E, Cervillen A, Mega M et a (1982) Comparative study between patients treated with transcutaneous electric stimulation and controls during labour. Clin Exp Obstet Gynaecol 9: 95-7
Woolf CJ, Thompson JW (1994) Stimulation fibre-induced analgesia: transcutaneous electrical nerve stimulation (TENS) and vibration. In: Wall PD, Melzack R, eds. The Textbook of Pain. Churchill Livingstone, London: 1191-1208

6. Pain Relief in Labour: An Overview (OBSTETRICS)
Published in: British Journal of Midwifery
October 1994, Vol 2, No 10
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By Sue Moore
Sue Moore is a Midwife Teacher at Birmingham and Solihull College of Nursing and Midwifery, Birmingham.

This article provides an overview of some of the physiological and psychological factors associated with pain relief in labour, together with some of the issues that midwives should acknowledge when supporting the woman in labour.

Childbirth may readily be described as one of the most momentous events in any woman’s life. The process of labour and childbirth is, however, both physically and emotionally demanding. As every midwife knows, for the majority of women one of the most significant aspects of this process is the apprehension and anxiety evoked by the prospect of pain in labour. In fact, labour pain has been identified as one of the most intense pain experiences (Melzack and Wall 1988).
The midwife’ role is crucial for informing and guiding women throughout pregnancy and labour; as well as sharing their joy, she will provide support, reassurance, and help in coping with any distress. The skills and sensitivity necessary for fulfilling this role are developed through an appreciation and understanding of the processes involved in pain perception and labour. It must be acknowledged that maternal distress is associated not only with labour but also with the pain experienced by many women in the puerperium, as well as with many of the ‘discomforts’ associated with pregnancy.
However, this article will consider primarily pain relief in labour and the factors associated with it.
It is important, initially, to reflect on the attitudes and beliefs that underpin every individual’s experience and expectation surrounding pain-relieving techniques.
Attitudes and beliefs relating to pain relief in labour have changed through the ages. In the Middle Ages, attitudes were often founded on the Christian belief that a woman should accept pain in labour as a consequence of her sin in the Garden of Eden. Reinforcement of such doctrine by the church and physicians of the time led to a widespread view that purification of sin was anonymous with pain in labour. A midwife attempting to relieve a woman’s distress, often using herbal remedies, could have been condemned to death as a witch. It was not until the famed use of chloroform by Queen Victoria that pain relief in childbirth became more acceptable within society. There is a current view which perceives labour pain as an experience that is both unwanted and necessary (Melzack and Wall, 1988):

‘Despite the obvious progress in our knowledge, many people who suffer cancer pain, postoperative pain, labour pain and various forms of chronic pain, are inadequately treated. We are appalled by the needless pain that plagues so many people…every human being has a right to freedom from pain.’

However, it has been demonstrated that a totally pain-free labour may not be associated with a wholly satisfying experience of the birth process (Morgan et al, 1982). This particular study, despite its methodological problems, may suggest that for many women, giving birth following a totally pain-free labour could result in some dissatisfaction with the whole experience. There are, of course, many potential explanations for their negative feeling. Nevertheless, it illustrates an area that no midwife should underestimate when evaluating the effectiveness of pain-relieving methods, i.e. the birth experience itself, and therefore potentially, the woman’s adjustment to motherhood. In turn, this may begin to reflect the complexities associated with pain perception in labour.

PHYSIOLOGY OF PAIN
One of the more obvious complexities associated with pain in labour is the variation between individual perceptions of pain. Pain has been described by Mersky (1986) as:

‘…an unpleasant sensory experience associated with actual or potential tissue damage, or described in terms of such damage’.
Such a definition goes only a short way to providing a full explanation for pain in labour. However, it does highlight that there are both physiological and emotional components to the pain experience.
Physiological explanations of pain transmission would appear, at first sight, to provide an inadequate explanation of the varying phenomena associated with the pain perception. Traditionally such explanations have focused on the specificity theory. However, pain is a subjective experience and the idea that a specific pain centre exists in a specific area of the brain has long been discredited. Melzack and Wall’s gate control theory of pain modulation (1965) would appear to provide an explanation which acknowledges the subjective component of pain perception.
‘Pain is a subjective experience, as each individual has a unique range of anatomical, physiological, social and psychological identities. These identities can be applied to the gate control theory to explain the subjective nature of pain perception’ (Clancy and McVicar, 1992).

This ‘gating’ mechanism occurs within the spinal cord’s dorsal horn grey matter in an area known as the substantia gelatinosa.
The gate control theory suggests that sensory information, such as pain, can only travel through to the brain when the ‘gate’ is open; the closing of the ‘gate’ is the basis of many forms of pain relief. The gate is operated by neurotransmitters which in turn excite ascending nerve fibres. Closing the gate is initiated by inhibitory neurotransmitters and endogenous chemicals. The gate theory provides an explanation not only for the psychological aspects of pain relief in labour, but also for many of the methods now familiar to midwifery practice such as transcutaneous nerve stimulation, massage, etc.

PSYCHOLOGICAL FACTORS
Many factors have been shown to influence individual perception of pain. Cultural background, for example, has a significant effect on pain perception threshold, giving rise to some amazing feats such as Indian fakirs who walk on hot coals or appear to impale their bodies with knives or hooks, apparently with no feeling of pain or signs of injury. However, as Melzack and Wall (1988) point out, care must be taken when asserting that variations in pain are due to variation in an individual’s pain threshold. Four thresholds have been demonstrated experimentally (Table 1). It is therefore suggested that it is the encouraged pain tolerance threshold that is utilized by women in labour, who are encouraged to do so by those supporting them.
Other factors that provide probable explanations for variation in individual pain experience has been identified, e.g. distraction of attention, level of anxiety, feelings of control, and the effect of suggestion (as demonstrated by placebos).
Midwives may recognize those women who will not want to use drugs in labour as well as others who will request an epidural from the very onset of labour. The use of stereotypes feature in the common attempt to explain psychological consistencies in behaviour between individuals. In midwifery practice, such stereotyping has resulted in women being labeled as the ‘well-educated, middle-class National Childbirth Trust (NCT) type’ or the ‘uneducated, working-class type’ Green et al, 1990). However, individual differences relating t personality traits, types and characteristics have long been identified psychologically.
As a result of psychotherapeutic practice, Raphael-Leff (1986) suggests that individual differences may provide some useful explanations for a woman’s expectation of the childbearing experience. This psychodynamic explanation proposes that women possess certain conscious and unconscious attitudes or ‘orientations’ towards pregnancy, labour and motherhood, and consequently perceive labour as either a ‘natural event’ or a ‘depleting, medical event’. The ‘facilitator’ is therefore the woman who will want no intervention in labour and the “regulator’ is the woman who perceives a need to experience a ‘civilised’ birth and will need analgesics in labour. It is considered that an understanding of psychological processes will enable midwives to identify those factors common to women in pregnancy, which will, in turn, assist them in recognizing and acknowledging the individual needs of women in labour.
Niven (1994) suggest that midwives may not always give value to the psychological coping strategies adopted by certain groups of women particularly those adopting what may be known as ‘fanciful NCT-type techniques’. It is believed that midwives are aware of the strategies adopted by women in labour as identified in this study; such strategies include relaxation, distraction, imagery, reversal of effect, breathing techniques, internalization of pain and certain other idiosyncratic strategies.
Niven also demonstrated that midwives consistently underestimate the intensity of pain experienced by women in labour. In turn, Rajan (1993) suggests that professionals are not good at recognising or responding to women’s pain in labour. Medical staff, for instance, commonly ‘believed that pain relief was effective while women reported it as unsatisfactory.’ Rajan’s secondary analysis of the data gathered by the National Birthday Trust (NBT) survey further suggests that 6-7% of all professional groups, i.e. midwives, obstetricians and anaesthetists, judged pain relief to be ineffective when women in fact believed it to effective. There would consequently appear to be some discrepancy between a woman’s experience of pain in labour and the perceptions of those caring for her. It is suggested, therefore, that a better understanding of women’s experiences during labour and the psychological processes associated with pain perception are necessary.

PHARMACOLOGICAL METHODS OF PAIN RELIEF
Midwives will be familiar with the methods of analgesia most frequently used by women in the UK. Approximately 60% of women use Entonox in labour, a further 37% use pethidine and 18% have an epidural anaesthetic. Diamorphine and meptazinol were used by a further 2.1% and 1.8% respectively (Chamberlain et al, 1993).
Pethidine is a controlled drug which the midwife is able to prescribe and is therefore more readily available to women in labour. Its disadvantages include maternal confusion and loss of control, as well as its prolonged effects on the newborn such as respiratory depression, poor sucking and other possible effects which hinder the establishment of successful breastfeeding.
Although epidural anaesthesia is the most effective method of pain relief, it is not without its problems. MacArthur et al (1991) identify some of the potential problems, such as long-term backache. Despite the potential problems, epidural anaesthesia is used most frequently by women who have been in labour for more than 16 hours. However, the facilities for epidural anaesthesia are still significantly limited, being available in only 63.3% of maternity units (Chamberlain et al, 1993).
In the future, techniques that allow a woman greater mobility in labour may be used; this would not only promote relaxation but would also be helpful in increasing relaxation and pelvic dimensions, thereby facilitating pain relief through effecting the physiological processes of labour.

THE MIDWIFE AND PAIN RELIEF
When assessing any woman’s pain in labour it must be remembered that the amount of pain is not merely a result of increasing sensory stimulation from uterine contractions and cervical dilation, but is an experience influenced by:

'…a complex interaction of psychological and physiological mechanisms which may serve to exacerbate or modulate the effects of noxious stimulation' (Melzack and Wall, 1988).
An important factor that cannot be ignored is the influence that a midwife will have on the woman’s labour experience and level of pain perception. It is proposed that the interaction between a labouring woman, together with her partner in labour, and her midwife is one of the most significant factors influencing pain relief. This interaction involves many skills, including communication, caring, empathy, compassion and understanding, i.e. the skills of being ‘with woman’, and thus reduces anxiety in the labouring woman and increases her feeling of being in control. Melzack and Wall describe pain as:

‘…one of the most challenging problems in medicine and biology…part of the problem lies with health professionals who have failed to keep up with the advances in our field.’

Midwives must rise to such a challenge, not only by updating their knowledge, but also by adding to the body of knowledge in an area which is, at present, sparse in research.

KEY POINTS
- Labour is one of the most intense forms of pain that can be experienced.
- Attitudes and beliefs relating to pain relief in labour have developed and changed over time.
- A totally pain-free labour may not be desirable for all women.
- The midwife’s skill in relieving pain associated with childbirth develops through an understanding of the physiological and psychological processes associated with pain perception.
- Physiological understanding includes a knowledge of not only the anatomical pathways involved in pain transmission but also the mechanisms of pain modulation.
- Psychological factors associated with pain perception focus on the focus on the subjectivity of pain experiences.
- Professionals caring for women in labour are not always good at recognizing or responding to individual pain experience.
- Midwives, by their presence, are themselves representative of one of the most effective means of pain relief in labour.

REFERENCES
Clancy J, McVicar A (1992) Subjectivity of pain. 1: 8-12
Chamberlain G, Wraight A, Steer P (1993) Pain and its Relief in Childbirth: The Results of a National Survey conducted by the National Birthday Trust, Churchill Livingstone, London.
Green JM, Kitzinger JV, Coupland VA (1990) Stereotypes of childbearing women: a look at some evidence. Midwifery 6(3): 125-32
MacArthur C, Lewis M, Knox EG (1991) Health After Childbirth. HMSO, London
Melzack R, Wall P (1988) The Challenge of Pain. Penguin Books, London.
Merskey H, ed (1986) Classification of chronic pain, descriptions of chronic pain syndrome and definitions of pain terms. In: Melzack R, Wall P (1988)
Morgan B, Bulpitt CJ, Clifton P, Lewis PJ (1982) Analgesia and satisfaction in childbirth (the Queen Charlottes’s 1,000 Mother survey). Lancet ii: 808-10
Niven C (1994) Coping with labour pain: the midwife’s role. In: Robinson S, Thompson A Midwife, Research and Childbirth, Chapman and Hall, London 3: 91-119
Rajan L (1993) Perceptions of pain and pain relief in labour: the gulf between experience and observation. Midwifery 9 (3): 136-45
Raphael-Leff J (1986) Facilitators and regulators: conscious and unconscious processes in pregnancy and motherhood. Br J Med Psychol 59: 43-55

7. An Evaluation of TENS for the Relief of Pain in Labour (OBSTETRICS)
Published in: The Association of Chartered Physiotherapists in Obstetrics and Gynaecology
Journal No. 65, Summer 1989

By Rosalind Davies, MCSP
Senior Obstetric Physiotherapist
Birmingham Maternity Hospital
Queen Elizabeth Medical Centre, Edgbaston, Birmingham

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