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DEFINING DIASTOLIC-PRESSURE READINGS
370
16-year-old girl, who has fibrocystic disease of the pancreas and associated chronic chest infection. Amitriptyline was increased from 10 mg. nocte to 30 mg. daily over a period of two weeks, at which point she was thought to be having slightly increased difficulty in coughing up sputum; the dosage of amitriptyline was not, therefore, increased any further. She remained on her routine antibiotics, pancreatin preparation, and detergent (tyloxapol) inhalations, and was not receiving any bronchodilators. Since the use of monamine-oxidase inhibitors is contraindicated in patients using or likely to be requiring sympathomimetic drugs, the spectrum of suitable antidepressants available is somewhat narrowed. Amitriptyline with its attendant tranquillising effect may well be the drug of choice in the treatment of depression in asthmatics, and it is also prescribed for enuresis in children, some of whom are asthmatic. I should be interested to know if any of your readers has suspected increased sputum viscosity in such patients on amitriptyline or other iminodibenzyl derivative. Monyhull Hospital, RITA M. BAILLIE. Birmingham 30.
SPONTANEOUS BRUISING
SIR,-In the summary of their article Dr. Hirsh and his colleagues (July 1, p. 18) state: " Spontaneous bruising is commonly seen in clinical practice; in most cases no cause is found." It has been our experience here that on careful questioning salicylate self-administration, even in small doses, is very common in cases of spontaneous bruising. Complete cessation of salicylate intake has resulted, in most cases, in permanent
disappearance of bruising.
Nicosia, Cyprus.
STELIOS H. NICOLAIDES.
BODY DECOMPRESSION IN HEART-FAILURE SIR,-In his article (July 29, p. 241) Dr. Potanin provides good evidence that lower-body decompression may be of value in the emergency treatment of pulmonary oedema. He fails, however, to refer to the extensive bibliography which has accumulated on the use of this technique in the normal subject since 1964. The information available suggests that the circulatory disturbance is sufficiently severe to counsel caution in the application of the method to patients with cardiac
insufficiency. It is not absolutely clear from the article how much of the body was exposed to the negative pressure and in what posture the patients were studied, but we assume that they were in the sitting or semirecumbent posture and that both abdomen and legs were exposed to the reduced pressure. Exposure of the parts of the body below the waist to a pressure of 60 mm. Hg below ambient, with the subject supine, causes pooling of 700-1000 ml. of blood in the legs.1-3 With a pressure of -30 mm.Hg the volume pooled would be 400-700 ml. Several workers1 45 have described the effects of this manoeuvre on various aspects of cardiovascular function; with only one exception 6 studies of the effects of lower-body negative pressure have been conducted with the subjects supine. The effect is graded. Although there is little change in mean arterial blood-pressure with any level of negative pressure unless it is too prolonged, cardiac output and stroke volume fall significantly.5 At -80 mm. Hg the changes are dramatic and cardiac output may fall from 6’6 to 3’6 litres per minute, the heart-rate may rise from 69 to 107 beats per minute, and the stroke volume may fall from 89 to 29 ml. 1. Brown, E., Goei, J. S., Greenfield, A. D. M., Plassaras, G. C. J. Physiol., Lond. 1966, 183, 607. 2. Murray, R. H., Krog, J., Carlson, L. D., Bowers, J. A. Aerospace Med.
1967, 38, 243. 3. Fentem, P. H. in Symposium on Problems of Manned Flight in Space. Proceedings of Biology in Space, NATO summer school, 1967.
Unpublished. 4. Gilbert, C. A., Stevens, P. M. J. appl. Physiol. 1966, 21, 1265. 5. Stevens, P. M., Lamb, L. E. Am. J. Cardiol. 1965, 16, 505. 6. Shaw, D. B., Cinkotai, F., Thomson, M. L. Aerospace Med. 1966, 154.
When even more of the body is exposed to negative pressure -that is, the parts below the xiphisternum-the circulatory disturbance can be even more severe.With a pressure of 60 mm. Hg there is an abrupt fall in arterial pressure during the first few seconds, sufficient in some subjects to impair vision and produce a feeling of impending loss of consciousness. When the suction continues arterial pressure shows some recovery but the mean pressure remains 10-15 mm. Hg below the resting level. It seems probable that up to 2 litres of blood will pool in the abdomen and lower limbs exposed to suction at - 60 mm. Hg, or about 1.2 litres at - 30 mm. Hg. Although Dr. Potanin used only small pressures he exposed more of the body than he need to negative pressure and probably did so with the patient in the sitting position, which adds the stress of gravity to the effects already described. A domestic vacuum cleaner is capable of reducing the pressure in a well-sealed system such as the Heyn’s suit to -100 mm. Hg, and such pressures are used briefly during labour by patients left to control their own suits.8On this account a warning about the effects of pressures greater than 30 mm. Hg below ambient is not out of place. -
The reduction in venous return to the atrium is quick and striking with lower-body decompression. The effects of allowing the blood pooled in the abdomen and legs to return to the central circulation are equally striking and potentially dangerous for patients in heart-failure. Following infra-xiphisternal suction for a minute at60 mm. Hg we have seen a rise in central venous pressure in healthy subjects to a value 5 mm. Hg above the resting level, at which it remained for more than a minute. If the suction is prolonged the reduction in the effective circulatory blood-volume induced by the pooling will, in healthy subjects, cause fluid retention and an increase in plasma volume, and has been used for this purpose to prevent circulatory deconditioning in states of simulated weightlessness.9Any fluid retention may further aggravate the danger on the release of suction.
These observations lead us to make several recommendations the use of lower-body negative pressure for the treatment of pulmonary cedema. Only the parts below the waist need be exposed to the negative pressure. The reduction in the effective circulatory blood-volume will be adequate, a congested liver would not be rendered more painful, and any impairment of respiratory mechanics will be reduced. The standard Heyn’s suit as used in obstetric practice exposes only the abdomen to the reduced pressure and we would not regard it as particularly suitable for this application. Care must be taken in the selection and maintenance of the pressure used. Finally, as Dr. Potanin rightly says, this can be regarded only as an interim emergency measure; it may pose even greater problems than tourniquets when the time comes for release. Within these limitations it seems to be a perfectly safe technique for the investigation 10 and possible treatment of patients. on
We are being supported in our investigations of the effects of lower-body negative pressure by a grant to Prof. A. D. M. Greenfield
from the British Heart Foundation. St. Mary’s Hospital, and Department of Physiology, St. Mary’s Hospital Medical School,
London W.2.
DEFINING DIASTOLIC-PRESSURE READINGS SIR,-May I beg that the method of recording the diastolic blood-pressure should always be stated ? At least two different points are taken as the diastolic-pressure reading: one the change in intensity, and the other the cessation, of sound. It is patently absurd that the results in a supposedly serious scientific article should have such an ill-defined basis. W. ANTONY BALL. Petworth, Sussex. Ardill, B. L., Bannister, R. G., Fentem, P. H., Greenfield, A. D. MJ. Physiol., Lond. 180, 23-24P. 8. Wolfard, M. Pulse, Jan. 28, 1967. 9. Lamb, L. E., Stevens, P. M. Aerospace Med. 1965, 36, 1145. 10. Bannister, R. G., Ardill, B. L., Fentem, P. H. Brain (in the press). 7.
37,
B. L. ARDILL R. BANNISTER P. H. FENTEM.
16-year-old girl, who has fibrocystic disease of the pancreas and associated chronic chest infection. Amitriptyline was increased from 10 mg. nocte to 30 mg. daily over a period of two weeks, at which point she was thought to be having slightly increased difficulty in coughing up sputum; the dosage of amitriptyline was not, therefore, increased any further. She remained on her routine antibiotics, pancreatin preparation, and detergent (tyloxapol) inhalations, and was not receiving any bronchodilators. Since the use of monamine-oxidase inhibitors is contraindicated in patients using or likely to be requiring sympathomimetic drugs, the spectrum of suitable antidepressants available is somewhat narrowed. Amitriptyline with its attendant tranquillising effect may well be the drug of choice in the treatment of depression in asthmatics, and it is also prescribed for enuresis in children, some of whom are asthmatic. I should be interested to know if any of your readers has suspected increased sputum viscosity in such patients on amitriptyline or other iminodibenzyl derivative. Monyhull Hospital, RITA M. BAILLIE. Birmingham 30.
SPONTANEOUS BRUISING
SIR,-In the summary of their article Dr. Hirsh and his colleagues (July 1, p. 18) state: " Spontaneous bruising is commonly seen in clinical practice; in most cases no cause is found." It has been our experience here that on careful questioning salicylate self-administration, even in small doses, is very common in cases of spontaneous bruising. Complete cessation of salicylate intake has resulted, in most cases, in permanent
disappearance of bruising.
Nicosia, Cyprus.
STELIOS H. NICOLAIDES.
BODY DECOMPRESSION IN HEART-FAILURE SIR,-In his article (July 29, p. 241) Dr. Potanin provides good evidence that lower-body decompression may be of value in the emergency treatment of pulmonary oedema. He fails, however, to refer to the extensive bibliography which has accumulated on the use of this technique in the normal subject since 1964. The information available suggests that the circulatory disturbance is sufficiently severe to counsel caution in the application of the method to patients with cardiac
insufficiency. It is not absolutely clear from the article how much of the body was exposed to the negative pressure and in what posture the patients were studied, but we assume that they were in the sitting or semirecumbent posture and that both abdomen and legs were exposed to the reduced pressure. Exposure of the parts of the body below the waist to a pressure of 60 mm. Hg below ambient, with the subject supine, causes pooling of 700-1000 ml. of blood in the legs.1-3 With a pressure of -30 mm.Hg the volume pooled would be 400-700 ml. Several workers1 45 have described the effects of this manoeuvre on various aspects of cardiovascular function; with only one exception 6 studies of the effects of lower-body negative pressure have been conducted with the subjects supine. The effect is graded. Although there is little change in mean arterial blood-pressure with any level of negative pressure unless it is too prolonged, cardiac output and stroke volume fall significantly.5 At -80 mm. Hg the changes are dramatic and cardiac output may fall from 6’6 to 3’6 litres per minute, the heart-rate may rise from 69 to 107 beats per minute, and the stroke volume may fall from 89 to 29 ml. 1. Brown, E., Goei, J. S., Greenfield, A. D. M., Plassaras, G. C. J. Physiol., Lond. 1966, 183, 607. 2. Murray, R. H., Krog, J., Carlson, L. D., Bowers, J. A. Aerospace Med.
1967, 38, 243. 3. Fentem, P. H. in Symposium on Problems of Manned Flight in Space. Proceedings of Biology in Space, NATO summer school, 1967.
Unpublished. 4. Gilbert, C. A., Stevens, P. M. J. appl. Physiol. 1966, 21, 1265. 5. Stevens, P. M., Lamb, L. E. Am. J. Cardiol. 1965, 16, 505. 6. Shaw, D. B., Cinkotai, F., Thomson, M. L. Aerospace Med. 1966, 154.
When even more of the body is exposed to negative pressure -that is, the parts below the xiphisternum-the circulatory disturbance can be even more severe.With a pressure of 60 mm. Hg there is an abrupt fall in arterial pressure during the first few seconds, sufficient in some subjects to impair vision and produce a feeling of impending loss of consciousness. When the suction continues arterial pressure shows some recovery but the mean pressure remains 10-15 mm. Hg below the resting level. It seems probable that up to 2 litres of blood will pool in the abdomen and lower limbs exposed to suction at - 60 mm. Hg, or about 1.2 litres at - 30 mm. Hg. Although Dr. Potanin used only small pressures he exposed more of the body than he need to negative pressure and probably did so with the patient in the sitting position, which adds the stress of gravity to the effects already described. A domestic vacuum cleaner is capable of reducing the pressure in a well-sealed system such as the Heyn’s suit to -100 mm. Hg, and such pressures are used briefly during labour by patients left to control their own suits.8On this account a warning about the effects of pressures greater than 30 mm. Hg below ambient is not out of place. -
The reduction in venous return to the atrium is quick and striking with lower-body decompression. The effects of allowing the blood pooled in the abdomen and legs to return to the central circulation are equally striking and potentially dangerous for patients in heart-failure. Following infra-xiphisternal suction for a minute at60 mm. Hg we have seen a rise in central venous pressure in healthy subjects to a value 5 mm. Hg above the resting level, at which it remained for more than a minute. If the suction is prolonged the reduction in the effective circulatory blood-volume induced by the pooling will, in healthy subjects, cause fluid retention and an increase in plasma volume, and has been used for this purpose to prevent circulatory deconditioning in states of simulated weightlessness.9Any fluid retention may further aggravate the danger on the release of suction.
These observations lead us to make several recommendations the use of lower-body negative pressure for the treatment of pulmonary cedema. Only the parts below the waist need be exposed to the negative pressure. The reduction in the effective circulatory blood-volume will be adequate, a congested liver would not be rendered more painful, and any impairment of respiratory mechanics will be reduced. The standard Heyn’s suit as used in obstetric practice exposes only the abdomen to the reduced pressure and we would not regard it as particularly suitable for this application. Care must be taken in the selection and maintenance of the pressure used. Finally, as Dr. Potanin rightly says, this can be regarded only as an interim emergency measure; it may pose even greater problems than tourniquets when the time comes for release. Within these limitations it seems to be a perfectly safe technique for the investigation 10 and possible treatment of patients. on
We are being supported in our investigations of the effects of lower-body negative pressure by a grant to Prof. A. D. M. Greenfield
from the British Heart Foundation. St. Mary’s Hospital, and Department of Physiology, St. Mary’s Hospital Medical School,
London W.2.
DEFINING DIASTOLIC-PRESSURE READINGS SIR,-May I beg that the method of recording the diastolic blood-pressure should always be stated ? At least two different points are taken as the diastolic-pressure reading: one the change in intensity, and the other the cessation, of sound. It is patently absurd that the results in a supposedly serious scientific article should have such an ill-defined basis. W. ANTONY BALL. Petworth, Sussex. Ardill, B. L., Bannister, R. G., Fentem, P. H., Greenfield, A. D. MJ. Physiol., Lond. 180, 23-24P. 8. Wolfard, M. Pulse, Jan. 28, 1967. 9. Lamb, L. E., Stevens, P. M. Aerospace Med. 1965, 36, 1145. 10. Bannister, R. G., Ardill, B. L., Fentem, P. H. Brain (in the press). 7.
37,
B. L. ARDILL R. BANNISTER P. H. FENTEM.