462
heart disease, and we may begin to see an increase in, say, renal failure. Depending on how the human lifespan is engineered by evolution, radical gerontology may, and some would say must, eventually run into limits of the same kind. As we get the better of malignant tumolirs we will have to concentrate on heart and vessels-or in the reverse order. When we achieve both, we may have to convert oncology and cardiology units to renal units. And when we begin to address lifespan setting mechanisms we may need to shift all these interventions to a higher age range. The pace of such changes is likely to be manageable, but there is no harm in thinking about them and preparing a range of options. 1. Weindruch
R, Walford RL. The retardation of aging and disease by dietary restriction. Springfield, Illinois: CC Thomas, 1988. 2. Olshansky SJ, Cames BA, Cassel C. In search of Methuselah: estimating the upper limits of longevity. Science 1990; 250: 634-40. 3. Putter A. Die Ältesten menschen. Naturwissenschaften 1921; 9: 875-80. 4. Fries JF. Aging, natural death, and the compression of morbidity. N Engl J Med 1980; 303: 130-35.
TENS for chronic low-back pain The use of electrical stimulation for pain relief has a long history, but modem stimulators were developed as a result of the gate control theory and were first studied in man in 1967.1 For transcutaneous electrical stimulation (TENS),2,3 the patient carries a small, portable, battery-powered stimulator which is connected via wires to electrodes. The electrodes are self-adhesive or applied to the skin with adhesive tape with an intervening layer of conductive gel. Dualoutput machines allow two sites to be stimulated simultaneously. The stimulator produces a pulsatile output, which can be of different wave-forms and delivered either continuously or in bursts. The patient can alter the output by adjusting the current intensity and pulse frequency and width to produce a tingling sensation. TENS has been tried in numerous conditions, although how it works is unclear. The technique has been used most for chronic pain/,3often for low-back pain. Does it help? Several trials have indicated benefit from TENS in 30-50% patients with chronic low-back pain, benefit often outlasts the period of stimulation.4-9 However, many of these studies were uncontrolled, the patients had different underlying conditions, and follow-up was often short. TENS has also been compared with other forms of treatment. High-intensity TENS seems to be as effective as acupuncture and distant ice-massage,l1 and more effective than conventional massage.12 Deyo and colleagues13 lately compared TENS, sham TENS, a programme of exercises and TENS, and exercises and sham TENS in 145 patients. After a month’s treatment, TENS had produced no clinically or statistically significant effect on pain, function, or back flexion. Exercise was
nerve
modestly beneficial for two months.
The researchers concluded that TENS is no more effective than placebo for patients with chronic back pain and that it added nothing to exercise alone. Deyo et al acknowledged that their results could have been due to successful blinding that included a credible placebo and strong suggestion, but they discounted several factors that might have contributed to these negative conclusions-eg, inadequate statistical power to detect important differences; inclusion of patients unlikely to respond to therapy; measures of outcome too unresponsive to detect clinically important differences; and inadequacy in the manner of the intervention to produce efficacy. Other possible factors were recruitment of the patients by newspaper advertisement, which probably attracts an atypical sample of back-pain sufferers; the requirement that they attend twice weekly appointments; the short duration of therapy; and that two types of TENS were used. The bewildering variety of TENS procedures illustrates the general confusion surrounding this technique. Studies have used stimulation that is
subliminal,14 comfortable,4 mildly uncomfortable,15 tolerable,12 intense,16 produces a sensation of vibrationor tingling,17 or is sufficient to produce muscle contractions.18 In many trials, high-frequency low-intensity stimulation has been used, although low-frequency high-intensity ("acupuncture-like") stimulation may sometimes be more effective.19 Burst stimulation does not appear to be any better than conventional stimulation. 20 Electrodes are usually placed on or around the region of maximum pain or near the nerves innervating that area. Trigger points associated with musculoskeletal pain often correlate with acupuncture points,21 and some,22 but not all,1s workers believe that these are important for effective TENS, and reduction in trigger-point sensitivity may not be required.23 In practice, most therapists use trial and error.
The most effective durations for each session and for the course of TENS treatment have not been established. In the study of Wynn Parry and Girgis,9 TENS was given by a trained physiotherapist for a minimum of eight hours daily for two weeks; many of their 101 inpatients with chronic back pain, 72% of whom had not improved with surgery, were able to return to work, and TENS proved to be the single most useful treatment. TENS is a very safe procedure, with few contraindications (eg, patients with pacemakers, pregnancy, use over the carotid sinus) and with side-effects largely limited to skin irritation under the electrodes, which can be diminished by use of non-irritant gels. The patient needs to attend hospital for instruction in the technique. Despite the expense ([80-[120 for the unit alone), if a small percentage of patients can lead a useful life, return to work, control
463
their
own
expensive
therapy
at
home, and avoid further
treatment, this represents excellent value
for money. TENS has
placebo effect as powerful as other pain-relieving methods, especially at the start of treatment/4 about 30% patients being helped by sham stimulation. This figure is probably less than that for patients helped by true TENS,2s and true stimulation mayb or may not provide longer benefit than placebo. The impossibility of achieving good controlled trials has been recognised ;26 apart from subliminal stimulation, which is as successful as sham stimulation,14 devices that induce tingling sensations cannot be compared with devices giving no electrical output. What is important is that TENS can produce some relief in over 30 % patients with intractable back pain. This is an impressive therapeutic result, a
achieved at little risk. It therefore seems sensible to offer an adequate, supervised course of TENS to paients with chronic low back pain. Moreover, it may well be irrelevant to subject TENS to further trials. 1. Wall PD, Sweet WH. Temporary abolition of pain in man. Science 1967; 155: 108-09. 2. Mannheimer JS, Lampe GN. Clinical transcutaneous electrical nerve stimulation. Philadelphia: FA Davis, 1984. 3. Gersh MR, Wolf SL. Application of transcutaneous electrical nerve stimulation in the management of patients with pain: state-of-the-art update. Phys Ther 1985; 65: 314-22. 4. Indeck W, Printy A. Skin application of electrical impulses for relief of pain in chronic orthopaedic conditions. Minn Med 1975; 58: 305-09. 5. Ersek RA. Low-back pain: prompt relief with transcutaneous neurostimulation. Orthop Rev 1976; 5: 27-31. 6. Long DM, Campbell JN, Gucer G. Transcutaneous electrical stimulation for relief of chronic pain. Adv Pain Res Ther 1979; 3: 593-99. 7. Bates JAV, Nathan PW. Transcutaneous electrical nerve stimulation for chronic pain. Anaesthesia 1988; 35: 817-22. 8. Fried T, Johnson R, McCracken W. Transcutaneous electrical nerve stimulation: its role in the control of chronic pain. Arch Phys Med Rehabil 1984; 65: 228-31. 9. Wynn Parry CB, Girgis F. The assessment and management of the failed back, Part II. Int Disabil Stud 1988; 10: 25-28. 10. Fox EJ, Melzack R. Transcutaneous electrical stimulation and acupuncture: comparison of treatment for low-back pain. Pain 1976; 2: 141-48. 11. Melzack R, Jeans ME, Stratford JG, Monks RC. Ice massage and transcutaneous electrical stimulation: comparison of treatment for low-back pain. Pain 1980; 9: 209-17. 12. Melzack R, Vetere P, Finch L. Transcutaneous electrical nerve stimulation for low back pain. A comparison of TENS and massage for pain and range of motion. Phys Ther 1983; 63: 489-93. 13. Deyo RA, Walsh NE, Martin DC, Schoenfeld LS, Ramamurthy S. A controlled trial of transcutaneous electrical nerve stimulation (TENS) and exercise for chronic low back pain. N Engl JMed 1990; 322: 1627-34. 14. Lehmann TR, Russell DW, Spratt KF, Colby H, Liu YK, Fairchild ML, Christensen S. Efficacy of electroacupuncture and TENS in the rehabilitation of chronic low back pain patients. Pain 1986; 26: 277-90. 15. Wolf SL, Gersh MR, Rao VR. Examination of electrode placements and stimulating parameters in treating chronic pain with conventional transcutaneous electrical nerve stimulation (TENS). Pain 1981; 11: 37-47. 16. Melzack R. Prolonged relief of pain by brief, intense transcutanous somatic stimulation. Pain 1975; 1: 357-73. 17. Linzer M, Long DM. Transcutaneous neural stimulation for relief of pain IEEE Trans Biomed Eng 1976; 23: 341-45. 18. Santiesteban AJ. The role of physical agents in the treatment of spine pain. Clin Orthop 1983; 179: 24-30. 19 Enksson MBE, Sjolund BH, Nielzén S. Long term results of penpheral conditioning stimulation as an analgesic measure in chronic pain. Pain 1979; 6: 335-47.
20. Field GM. Spanswick CC, Hunter ME, Main CJ. A comparison of two modes of transcutaneous electrical nerve stimulation in chronic back pain. Pain 1990; 5 (suppl): S231. 21. Melzack R, Stillwell DM, Fox EJ. Trigger points and acupuncture points for pain: correlations and implications. Pain 1977; 3: 3-23. 22. Berlant SR. Method of determining optimal stimulation sites for transcutaneous electrical nerve stimulation. Phys Ther 1984; 64: 924-28. 23. Graff-Radford SB, Reeves JL, Baker RL, Chiu D. Effects of transcutaneous electrical nerve stimulation on myofascial pain and trigger point sensitivity. Pain 1989; 37: 1-5. 24. Evans FJ. The placebo response in pain reduction. Adv Neurol 1974; 4: 289-96. 25. Thorsteinsson G, Stonnington HH, Stillwell GK, Elveback LR. Transcutaneous electrical stimulation: a double-blind trial of its efficacy for pain. Arch Phys Med Rehabil 1977; 58: 8-13. 26. Deyo RA, Walsh NE, Schoenfeld LS, Ramamurthy S. Can trials of physical treatments be blinded? The example of transcutaneous electrical nerve stimulation for chronic pain. Am J Phys Med Rehabil 1990; 69: 6-10.
To ventilate
or
not
Should ventilators be used to treat acute exacerbations of chronic lung disease? The difficulties of weaning such patients off ventilation are widely recognised. Intensive care beds may be occupied for many weeks, and patients may even require a long-term tracheostomy, with or without mechanical ventilation via this route, when they return horned To deny this therapy often condemns the patient to a premature death during the acute illness. Although knowledge of the previous forced expiratory volume in 1 second (FEV1), arterial blood gases, exercise capacity, and quality of life may be helpful, this is not always the case2and such data are often unavailable at the time hard decisions have to be made. The approach in the UK tends to be more conservative than that in the USA, for example, where many of these patients are intubated and ventilated. The work of Brochard et aP suggests that this dilemma may be receding. These researchers describe a method of inspiratory pressure support ventilation with a face mask that they have used during acute exacerbations of chronic airflow obstruction. The system provides a constant but adjustable positive pressure during inspiration; it is triggered by the patient’s respiratory effort and stops when the inspiratory flow rate falls below a threshold value. This treatment improved the p02, pCOz, and pH and reduced diaphragmatic activity. Intubation was avoided in most patients. By comparison with a matched group of control patients who had been managed conventionally in the intensive care unit during the preceding two years, duration of stay in the unit was reduced and the survival rate was the same. Although inspiratory pressure support ventilation has become popular in intensive care units as a method of weaning patients from conventional ventilation,44 this method cannot be recommended unless facilities for intubation are immediately available should the technique not prove successful. The inspiratory phase can be terminated only when the flow rate through the ventilator falls. An air leak around the face or nasal mask, for example, may prevent the ventilator from
heart disease, and we may begin to see an increase in, say, renal failure. Depending on how the human lifespan is engineered by evolution, radical gerontology may, and some would say must, eventually run into limits of the same kind. As we get the better of malignant tumolirs we will have to concentrate on heart and vessels-or in the reverse order. When we achieve both, we may have to convert oncology and cardiology units to renal units. And when we begin to address lifespan setting mechanisms we may need to shift all these interventions to a higher age range. The pace of such changes is likely to be manageable, but there is no harm in thinking about them and preparing a range of options. 1. Weindruch
R, Walford RL. The retardation of aging and disease by dietary restriction. Springfield, Illinois: CC Thomas, 1988. 2. Olshansky SJ, Cames BA, Cassel C. In search of Methuselah: estimating the upper limits of longevity. Science 1990; 250: 634-40. 3. Putter A. Die Ältesten menschen. Naturwissenschaften 1921; 9: 875-80. 4. Fries JF. Aging, natural death, and the compression of morbidity. N Engl J Med 1980; 303: 130-35.
TENS for chronic low-back pain The use of electrical stimulation for pain relief has a long history, but modem stimulators were developed as a result of the gate control theory and were first studied in man in 1967.1 For transcutaneous electrical stimulation (TENS),2,3 the patient carries a small, portable, battery-powered stimulator which is connected via wires to electrodes. The electrodes are self-adhesive or applied to the skin with adhesive tape with an intervening layer of conductive gel. Dualoutput machines allow two sites to be stimulated simultaneously. The stimulator produces a pulsatile output, which can be of different wave-forms and delivered either continuously or in bursts. The patient can alter the output by adjusting the current intensity and pulse frequency and width to produce a tingling sensation. TENS has been tried in numerous conditions, although how it works is unclear. The technique has been used most for chronic pain/,3often for low-back pain. Does it help? Several trials have indicated benefit from TENS in 30-50% patients with chronic low-back pain, benefit often outlasts the period of stimulation.4-9 However, many of these studies were uncontrolled, the patients had different underlying conditions, and follow-up was often short. TENS has also been compared with other forms of treatment. High-intensity TENS seems to be as effective as acupuncture and distant ice-massage,l1 and more effective than conventional massage.12 Deyo and colleagues13 lately compared TENS, sham TENS, a programme of exercises and TENS, and exercises and sham TENS in 145 patients. After a month’s treatment, TENS had produced no clinically or statistically significant effect on pain, function, or back flexion. Exercise was
nerve
modestly beneficial for two months.
The researchers concluded that TENS is no more effective than placebo for patients with chronic back pain and that it added nothing to exercise alone. Deyo et al acknowledged that their results could have been due to successful blinding that included a credible placebo and strong suggestion, but they discounted several factors that might have contributed to these negative conclusions-eg, inadequate statistical power to detect important differences; inclusion of patients unlikely to respond to therapy; measures of outcome too unresponsive to detect clinically important differences; and inadequacy in the manner of the intervention to produce efficacy. Other possible factors were recruitment of the patients by newspaper advertisement, which probably attracts an atypical sample of back-pain sufferers; the requirement that they attend twice weekly appointments; the short duration of therapy; and that two types of TENS were used. The bewildering variety of TENS procedures illustrates the general confusion surrounding this technique. Studies have used stimulation that is
subliminal,14 comfortable,4 mildly uncomfortable,15 tolerable,12 intense,16 produces a sensation of vibrationor tingling,17 or is sufficient to produce muscle contractions.18 In many trials, high-frequency low-intensity stimulation has been used, although low-frequency high-intensity ("acupuncture-like") stimulation may sometimes be more effective.19 Burst stimulation does not appear to be any better than conventional stimulation. 20 Electrodes are usually placed on or around the region of maximum pain or near the nerves innervating that area. Trigger points associated with musculoskeletal pain often correlate with acupuncture points,21 and some,22 but not all,1s workers believe that these are important for effective TENS, and reduction in trigger-point sensitivity may not be required.23 In practice, most therapists use trial and error.
The most effective durations for each session and for the course of TENS treatment have not been established. In the study of Wynn Parry and Girgis,9 TENS was given by a trained physiotherapist for a minimum of eight hours daily for two weeks; many of their 101 inpatients with chronic back pain, 72% of whom had not improved with surgery, were able to return to work, and TENS proved to be the single most useful treatment. TENS is a very safe procedure, with few contraindications (eg, patients with pacemakers, pregnancy, use over the carotid sinus) and with side-effects largely limited to skin irritation under the electrodes, which can be diminished by use of non-irritant gels. The patient needs to attend hospital for instruction in the technique. Despite the expense ([80-[120 for the unit alone), if a small percentage of patients can lead a useful life, return to work, control
463
their
own
expensive
therapy
at
home, and avoid further
treatment, this represents excellent value
for money. TENS has
placebo effect as powerful as other pain-relieving methods, especially at the start of treatment/4 about 30% patients being helped by sham stimulation. This figure is probably less than that for patients helped by true TENS,2s and true stimulation mayb or may not provide longer benefit than placebo. The impossibility of achieving good controlled trials has been recognised ;26 apart from subliminal stimulation, which is as successful as sham stimulation,14 devices that induce tingling sensations cannot be compared with devices giving no electrical output. What is important is that TENS can produce some relief in over 30 % patients with intractable back pain. This is an impressive therapeutic result, a
achieved at little risk. It therefore seems sensible to offer an adequate, supervised course of TENS to paients with chronic low back pain. Moreover, it may well be irrelevant to subject TENS to further trials. 1. Wall PD, Sweet WH. Temporary abolition of pain in man. Science 1967; 155: 108-09. 2. Mannheimer JS, Lampe GN. Clinical transcutaneous electrical nerve stimulation. Philadelphia: FA Davis, 1984. 3. Gersh MR, Wolf SL. Application of transcutaneous electrical nerve stimulation in the management of patients with pain: state-of-the-art update. Phys Ther 1985; 65: 314-22. 4. Indeck W, Printy A. Skin application of electrical impulses for relief of pain in chronic orthopaedic conditions. Minn Med 1975; 58: 305-09. 5. Ersek RA. Low-back pain: prompt relief with transcutaneous neurostimulation. Orthop Rev 1976; 5: 27-31. 6. Long DM, Campbell JN, Gucer G. Transcutaneous electrical stimulation for relief of chronic pain. Adv Pain Res Ther 1979; 3: 593-99. 7. Bates JAV, Nathan PW. Transcutaneous electrical nerve stimulation for chronic pain. Anaesthesia 1988; 35: 817-22. 8. Fried T, Johnson R, McCracken W. Transcutaneous electrical nerve stimulation: its role in the control of chronic pain. Arch Phys Med Rehabil 1984; 65: 228-31. 9. Wynn Parry CB, Girgis F. The assessment and management of the failed back, Part II. Int Disabil Stud 1988; 10: 25-28. 10. Fox EJ, Melzack R. Transcutaneous electrical stimulation and acupuncture: comparison of treatment for low-back pain. Pain 1976; 2: 141-48. 11. Melzack R, Jeans ME, Stratford JG, Monks RC. Ice massage and transcutaneous electrical stimulation: comparison of treatment for low-back pain. Pain 1980; 9: 209-17. 12. Melzack R, Vetere P, Finch L. Transcutaneous electrical nerve stimulation for low back pain. A comparison of TENS and massage for pain and range of motion. Phys Ther 1983; 63: 489-93. 13. Deyo RA, Walsh NE, Martin DC, Schoenfeld LS, Ramamurthy S. A controlled trial of transcutaneous electrical nerve stimulation (TENS) and exercise for chronic low back pain. N Engl JMed 1990; 322: 1627-34. 14. Lehmann TR, Russell DW, Spratt KF, Colby H, Liu YK, Fairchild ML, Christensen S. Efficacy of electroacupuncture and TENS in the rehabilitation of chronic low back pain patients. Pain 1986; 26: 277-90. 15. Wolf SL, Gersh MR, Rao VR. Examination of electrode placements and stimulating parameters in treating chronic pain with conventional transcutaneous electrical nerve stimulation (TENS). Pain 1981; 11: 37-47. 16. Melzack R. Prolonged relief of pain by brief, intense transcutanous somatic stimulation. Pain 1975; 1: 357-73. 17. Linzer M, Long DM. Transcutaneous neural stimulation for relief of pain IEEE Trans Biomed Eng 1976; 23: 341-45. 18. Santiesteban AJ. The role of physical agents in the treatment of spine pain. Clin Orthop 1983; 179: 24-30. 19 Enksson MBE, Sjolund BH, Nielzén S. Long term results of penpheral conditioning stimulation as an analgesic measure in chronic pain. Pain 1979; 6: 335-47.
20. Field GM. Spanswick CC, Hunter ME, Main CJ. A comparison of two modes of transcutaneous electrical nerve stimulation in chronic back pain. Pain 1990; 5 (suppl): S231. 21. Melzack R, Stillwell DM, Fox EJ. Trigger points and acupuncture points for pain: correlations and implications. Pain 1977; 3: 3-23. 22. Berlant SR. Method of determining optimal stimulation sites for transcutaneous electrical nerve stimulation. Phys Ther 1984; 64: 924-28. 23. Graff-Radford SB, Reeves JL, Baker RL, Chiu D. Effects of transcutaneous electrical nerve stimulation on myofascial pain and trigger point sensitivity. Pain 1989; 37: 1-5. 24. Evans FJ. The placebo response in pain reduction. Adv Neurol 1974; 4: 289-96. 25. Thorsteinsson G, Stonnington HH, Stillwell GK, Elveback LR. Transcutaneous electrical stimulation: a double-blind trial of its efficacy for pain. Arch Phys Med Rehabil 1977; 58: 8-13. 26. Deyo RA, Walsh NE, Schoenfeld LS, Ramamurthy S. Can trials of physical treatments be blinded? The example of transcutaneous electrical nerve stimulation for chronic pain. Am J Phys Med Rehabil 1990; 69: 6-10.
To ventilate
or
not
Should ventilators be used to treat acute exacerbations of chronic lung disease? The difficulties of weaning such patients off ventilation are widely recognised. Intensive care beds may be occupied for many weeks, and patients may even require a long-term tracheostomy, with or without mechanical ventilation via this route, when they return horned To deny this therapy often condemns the patient to a premature death during the acute illness. Although knowledge of the previous forced expiratory volume in 1 second (FEV1), arterial blood gases, exercise capacity, and quality of life may be helpful, this is not always the case2and such data are often unavailable at the time hard decisions have to be made. The approach in the UK tends to be more conservative than that in the USA, for example, where many of these patients are intubated and ventilated. The work of Brochard et aP suggests that this dilemma may be receding. These researchers describe a method of inspiratory pressure support ventilation with a face mask that they have used during acute exacerbations of chronic airflow obstruction. The system provides a constant but adjustable positive pressure during inspiration; it is triggered by the patient’s respiratory effort and stops when the inspiratory flow rate falls below a threshold value. This treatment improved the p02, pCOz, and pH and reduced diaphragmatic activity. Intubation was avoided in most patients. By comparison with a matched group of control patients who had been managed conventionally in the intensive care unit during the preceding two years, duration of stay in the unit was reduced and the survival rate was the same. Although inspiratory pressure support ventilation has become popular in intensive care units as a method of weaning patients from conventional ventilation,44 this method cannot be recommended unless facilities for intubation are immediately available should the technique not prove successful. The inspiratory phase can be terminated only when the flow rate through the ventilator falls. An air leak around the face or nasal mask, for example, may prevent the ventilator from
