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Postural hypotension and the anti-gravity suit.
An air force anti-gravity suit, as used by fighter pilots to prevent loss of consciousness, has been successfully employed to treat severe postural hypotension in a patient with Shy-Drager syndrome. The definition of postural hypotension is reviewed, and reference is made to the previous use of the anti-gravity suit in the treatment of this condition.
Effect of a pulsating anti-gravity suit on peak exercise performance in individual with spinal cord injuries.
The aim of this study was to examine effects of a pulsating pressure anti-gravity suit on the peak values of oxygen uptake (VO2) and power during maximal arm exercise in spinal-cord-injured (SCI) individuals. Five well-trained SCI men (with lesions at levels between T6 and L1) and seven well-trained able-bodied men (ABC) performed two incremental (10 W x min(-1)) arm-cranking tests. During one test the pressure in the anti-G suit pulsated between 4.7 kPa (35 mmHg) and 9.3 kPa (70 mmHg) every 2 s (PPG+), during the other test (PPG-) all the subjects wore the anti-G suit in a deflated state. Tests were performed in a counter-balanced order. Peak VO2 in SCI was 1 ml x kg(-1) x min(-1) lower during PPG+ compared to PPG- (P = 0.05). Peak power and peak heart rate were not significantly different during PPG+ compared to PPG-. These results would suggest that no increase in work capacity can be obtained with a pulsating pressure anti-gravity suit in either SCI or ABC.
Renin stimulation by passive tilting: the influence of an anti-gravity suit on postural changes in plasma renin activity, plasma noradrenaline concentration and kidney function in normal man.
Plasma renin activity (PRA), plasma noradrenaline concentration, heart rate, blood pressure, and clearances of para-aminohippurate and inulin were measured in twelve normal subjects (clearances in only three subjects) before and after 40 min of 60 degrees upright tilting. The tilting experiments were repeated after inflation of an anti-gravity suit to 60 mmHg on the lower extremities. Inflation of the anti-gravity suit caused an abolition of the postural PRA increase, a marked reduction of the postural increases in plasma noradrenaline and heart rate, and elimination of the decreases in pulse pressure, inulin and para-aminohippurate clearances and sodium excretion. The results suggest a decisive role of the sympathetic nervous system for postural renin increase, probably mainly activated by stretch receptors in the low-pressure cardiopulmoanry area.
The gravity suit: a useful device in complicated urologic hemorrhage.
External counterpressure with a gravity suit was used to control intractable postoperative bleeding in 4 urologic patients. Two patients had coagulation defects, and 2 had been unsuccessfully reexplored prior to application of the G-suit. The bleeding was controlled with preservation and restoration of vital signs in each case. In 3 cases external counterpressure may have been lifesaving.
The gravity suit: a major advance in management of gynecologic blood loss.
We have used the gravity suit (G-suit) to stabilize patients in shock as a result of ruptured ectopic pregnancies. Four patients presenting in shock were carefully studied with serial vital signs, fluid replacement, and blood loss before and after application of the G-suit. These studies were continued through surgery and the removal of the G-suit. The G-suit improved vital signs, increased peripheral organ and limb perfusion, and decreased blood loss in all cases.
An experimental microcomputer controlled system for synchronized pulsating anti-gravity suit.
An experimental system to deliver synchronized external pressure pulsations to the lower body is described in this technical note. The system is designed using a microcomputer with a real time interface and an electro-pneumatic subsystem capable of delivering pressure pulses to a modified anti-G suit at a fast rate. It is versatile, containing many options for synchronizing, phasing and sequencing of the pressure pulsations and controlling the pressure level in the suit bladders. Details of its software and hardware are described along with the results of initial testing in a Dynamic Flight Simulator on human volunteers.
[Dynamic proprioceptive correction in the rehabilitation of patients with a late residual stage of stroke].
Space gravity suit has been used for over 20 years in Russian space stations to prevent harmful consequences of being in zero gravity (osteoporosis, muscle atrophies, etc.). The space suit is designed in such a way that it enables to create a payload on muscles, temporarily out of function, which is adequate to the natural one. Stroke patients with motor defect of hemiparesis are quite limited in their movement. To develop walking and self-serving skills we conducted 2-hour sessions of treatment using space gravity suit. Neuro-physiological and psychological methods confirm the positive effect of treatment. The predictors of positive effect of treatment were also observed. Our experience has shown that the method is simple to use, very effective and can be applied in both clinics and home conditions.
[Maximal exercise in spinal cord injured subjects: effects of an antigravity suit].
Paraplegics have low aerobic capacity because of the spinal cord injury. Their functional muscle mass is reduced and usually untrained. They have to use upperbody muscles for displacements and daily activities. Sympathic nervous system injury is responsible of vasomotricity disturbances in leg vessels and possible abdominal vessels, proportionally to level injury. If cord injury level is higher than T5, then sympathic cardiac efferences may be damaged. Underbody muscles atrophy and vasomotricity disturbances contribute to phlebostasis. This stasis may decrease venous return, preload and stroke volume (Starling). To maintain appropriate cardiac output, tachycardia is necessary, especially during exercise. Low stroke volume, all the more since it is associated with cardio-acceleration disturbances, may reduce cardiac output reserve, and so constitutes a limiting factor for adaptation to exercise. The aim of this study was to verify if use of an underlesional pressure suit may increase cardiac output reserve because of lower venous stasis, and increase performance. We studied 10 able-bodied and 14 traumatic paraplegic subjects. Able-bodied subjects were 37 +/- 6 years old, wellbeing, not especially trained with upperbody muscles: there were 2 women and 8 men. Paraplegics were 27 +/- 7 years old, wellbeing except paraplegia, five of them practiced sport regularly (athletism or basket for disabled), and the others just daily propelled their wheelchair; there were 5 women and 9 men. For 8 of them, cord injury levels were located below T7, between T1 and T6 for the others. The age disability varied from 6 months to 2 years for 9 of them, it was approximately five years for 4 of them, and 20 years for one. We used a maximal triangular arm crank exercise with an electro-magnetic ergocycle Gauthier frame. After five minutes warm up, it was proceeded in one minute successive stages until maximal oxygen consumption is raised. VO2, VCO2, RER were measured by direct method with an Ergostar analyser every 30 seconds. Heart rate was registered continuously using a cardio-frequence-meter Baumann, and ECG was observed on a Cardiovit electro-cardiograph. Each subject reached maximal exercises on different days: one without any contention, and the other one with abdomen and legs contention using an antigravity suit, inflated to 45-50 mm Hg for legs and 30-40 mm Hg for abdomen. The able-bodied subjects VO2 peak was 24 +/- 5.8 mL min-1 kg-1, without any change on peak VO2 and on cardiac frequency when pressure suit was used. Results were different for paraplegics: peak VO2 was significantly higher (21.5 +/- 6.5 mL min-1 kg-1 without contention and 23.8 +/- 6.3 mL min-1 kg-1 with contention), heart rate was significantly lower at all stages of exercise with antigravity suit and comfort was better during exercise and rest. In our study, contention contributed to increase paraplegics's performances, but responses depend also on spinal cord level, injury age, spasticity. Therefore, testing paraplegics using an antigravity suit may be useful to determine if neurovegetative disturbances significantly modify their cardiac adaptation and capability. If gravity suit is efficient, contention tights might be prescribed, with respect to subject's legs measurements. But, because these tights are very difficult to put on, their efficiency has to be proved before, the motivation of the subject is essential too.
Application of USAF G-suit technology for clinical orthostatic hypotension: a case study.
INTRODUCTION: The purpose of this study was to determine the effectiveness of a USAF anti-gravity suit (G-suit) on the stability of a patient with chronic orthostatic hypotension. METHODS: A 37-yr-old female with a history of insulin-dependent diabetes mellitus (IDDM) and symptomatic orthostasis was evaluated and the results were compared with those of non-diabetic controls, matched for age, height, and weight. Cardiac vagal tone was assessed by determination of standard deviation of 100 R-R intervals (R-R SD). We assessed the carotid-cardiac baroreflex response by plotting R-R intervals (ms) at each of eight neck pressure steps with their respective carotid distending pressures (mm Hg). Heart rate and blood pressure were recorded in response to the Valsalva maneuver (VM) performed at an expiratory pressure of 30 mmHg to assess integrated baroreflex responses. Blood pressures and heart rate were measured during three 5-min stand tests to assess orthostatic responses: a) without G-suit; b) with noninflated G-suit; and c) with inflated G-suit (50 mm Hg). RESULTS: The IDDM patient had minimal baseline cardiac vagal tone (R-R SD = 8.5 ms) compared with the average response of a control group of 24 subjects with orthostatic stability (R-R SD = 67.2 +/- 7.1 ms). Carotid-cardiac baroreflex response was virtually non-existent in the IDDM patient (Gain = 0.06 ms.mm Hg-1) compared to the control subjects (4.4 +/- 0.8 ms.mm Hg-1). VM responses corroborated the lack of cardiac baroreflex response in the IDDM patient, while blood pressure changes during the VM were similar to those of the controls. Upon standing, the IDDM patient demonstrated severe orthostatic hypotension (90 mm Hg SBP) and tachycardia without the G-suit. The G-suit, with and without pressure, reduced hypotension and tachycardia during standing. CONCLUSION: These results demonstrate successful application of Air Force technology as a useful alternative to pharmacologic intervention in the treatment of a patient with autonomic dysfunction leading to supine hypertension and orthostatic hypotension.
Spontaneous rupture of the liver in pregnancy: a report of eight cases.
Seven cases of ruptured subcapsular hematoma and one case of ruptured hepatoma are reported. Six of the patients died, four following an unsuccessful operation. One patient survived following an operation, and another patient survived without surgical intervention. Both survivors were treated with a gravity suit to control internal hemorrhage.
The effect of an anti-G suit on the maximal performance of individuals with paraplegia.
The purpose of this study was to examine whether lower body positive pressure (LBPP) could improve maximal performance in paraplegic subjects (P). LBPP may diminish venous blood pooling (VBP) below the lesion and, therefore, support the redistribution of blood during exercise. Twelve male P subjects with complete spinal cord-lesions between T6 and T12, and 13 male able-bodied control subjects (C), performed maximal arm-cranking exercise with and without LBPP (52 mmHg) by means of an anti-gravity suit. P and C subjects had a significantly lower maximal heart rate (HRmax) with LBPP than without (P: 176 +/- 10 vs 184 +/- 7 b.min-1; C: 174 +/- 8 vs 177 +/- 8 b.min-1), whereas maximal power output (Wmax) and oxygen uptake (VO2max) remained unchanged. This suggests that LBPP provides P and C with central hemodynamic benefits. These benefits, however, did not result in improvements in Wmax or VO2max, probably due to other limitations in the complex and closely linked oxygen uptake process. During submaximal exercise the circulatory benefits were more pronounced in P than in C, probably due to the decrease of the VBP by LBPP. The results of this study suggest that LBPP appears to offer both P and C groups a central hemodynamic benefit without improving maximal performance.
Blood redistribution and circulatory responses to submaximal arm exercise in persons with spinal cord injury.
The purpose of this study was to evaluate responses to submaximal arm exercise (20%, 40%, and 60% of peak power output) using four conditions to support the circulatory redistribution in persons with spinal cord injury (SCI). Five males with tetraplegia (TP) and four males with paraplegia (PR) exercised 1) sitting, 2) supine, and 3) sitting with the addition of a) an anti-gravity suit (anti-G), b) elastic stockings and abdominal binder, and c) functional electrical stimulation of the leg muscles. Compared to sitting, the following significant changes were observed: in the supine position, heart rate (HR) decreased (PR: 104 vs 118 b/min, TP: 76 vs 92 b/min) and stroke volume (SV) increased (PR: 132 vs 116 ml, TP: 96 vs 83 ml). The anti-G suit induced a decrease in heart rate (PR: 104 vs 118 b/min, TP: 87 vs 92 b/min) and a decrease in oxygen uptake (VO2) in PR. Stockings only affected TP, i.e. a decrease in heart rate with 5 b/min and an increase in stroke volume with 13 ml/beat. Functional electrical stimulation produced an increase in VO2 (PR: 1.00 vs 0.95 l/min, TP: 0.68 vs 0.53 l/min) and a rise in stroke volume in TP. Results indicate that the methods employed to support the circulatory redistribution have different working mechanisms and, in addition, that the effects are different for TP and PR probably because of differences in active muscle mass, sympathetic impairment and blood pressure values.
Limits to maximal performance in individuals with spinal cord injury.
The purpose of this study was to examine the effect of four conditions that might improve oxygen transport and/or utilization during maximal exercise performance in individuals with spinal cord injury (SCI). Five males with tetraplegia (TP) and four males with paraplegia (PR) performed maximal arm cranking exercise in the following positions: 1) sitting; 2) supine; and 3) sitting with the addition of a) anti-gravity suit (anit-G), b) elastic stockings and abdominal binder, and c) functional electrical stimulation (FES) of the paralysed leg muscles. Peak power output (PO peak), peak oxygen uptake (VO2peak), peak heart rate (HR peak) and maximal systolic blood pressure were significantly lower in TP compared to PR for all conditions. A significant decrease in HR peak for PR, and a significant increase in VO2peak/kg for TP was seen during the supine compared to sitting condition. Respiratory exchange ratio (R) decreased significantly during the FES compared to the sitting condition in TP. No other changes were observed for any of the other conditions in either group. Improvements in central circulation previously reported during submaximal exercise for these four conditions did not result in a concomitant rise in maximal exercise performance. The results of this study suggest that the limitation in VO2peak for individuals with SCI is located peripherally (small active muscle mass) rather than centrally (heart or lungs).
Disabling postural hypotension complicating diabetic autonomic neuropathy.
A 35-year-old Type 1 diabetic man with severe disabling postural hypotension was studied for physiological abnormalities, precipitating factors, and effect of current treatment. A 24-h blood pressure profile indicated a diurnal variation in systolic blood pressure with the lowest values recorded between 0100 and 0600 h, during which the patient often lost consciousness on standing (mean standing systolic pressure 78 mmHg at night vs 105 mmHg in the afternoon, p less than 0.001). Food induced a profound fall in systolic pressure, both while supine and while standing erect. The systolic pressure fall during euglycaemia was 49 mmHg vs 3 mmHg during hypoglycaemia. Plasma noradrenaline and adrenaline levels were low during euglycaemia, but increased during hypoglycaemia. Therapeutic manoeuvres aimed at increasing heart rate (by atrial tachypacing) and reducing the peripheral pooling of blood (vasoconstricting drugs and gravity suit), together with the somatostatin analogue octreotide, proved ineffective. These observations demonstrate the phenomenon of post-prandial exacerbation of postural hypotension in a Type 1 diabetic patient, and indicate that despite failure of conventional methods of treatment, hypoglycaemia increased plasma catecholamines and was effective in abolishing the blood pressure fall on standing.
Physiology of wheelchair racing in athletes with spinal cord injury.
Wheelchair racing is one of the most popular sporting activities of individuals with spinal cord injury. Athletes with this impairment have unique changes in metabolic, cardiorespiratory, neuromuscular and thermoregulatory systems, which reduce their overall physiological capacity compared with able-bodied individuals or individuals with other types of impairments. This review on spinal cord injury: presents the International Stoke Mandeville Games Federation classification of wheelchair athletes; describes methods commonly used to characterise anaerobic and aerobic fitness; presents the findings of physiological studies that have evaluated wheelchair racing performance; identifies the risks associated with temperature regulation when competing in wheelchair races; and discusses special conditions that can influence wheelchair racing performance. Currently there is limited research that has examined the relationship between sprint or distance wheelchair racing performance and the anaerobic and aerobic components of physical fitness. Although the descriptive evidence indicates that the profiles of these athletes reflect their training and participation in these specific events, the association between their physiological profiles and real or simulated racing performance is unclear. The generally accepted concept that high values of aerobic and anaerobic power are strongly correlated with endurance and sprint racing performance, respectively, are not necessarily true in this population. Athletes with spinal cord injury have an impaired thermoregulatory capacity, because the compromised autonomic and somatic nervous system functions disrupt control of skin blood flow and sweating below the level of the lesion. As a result, they may be more susceptible to hyperthermia during distance wheelchair racing performance. Wheelchair athletes should follow recommendations advocated for able-bodied individuals to minimise their risks of heat stress during competition. Many athletes with quadriplegia voluntarily induce autonomic dysreflexia (commonly known as boosting) during distance racing events to improve performance. Experimental evidence indicates that boosting can improve performance time by 10% in elite wheelchair marathon racers during simulated racing, as a result of increased oxygen utilisation in the boosted state. However, since boosting can be dangerous to health, the International Paralympic Committee has banned athletes from voluntarily inducing it during competition. The use of anti-gravity suits to increase lower-body positive pressure can increase the peak oxygen uptake, cardiac output and stroke volume. However, the use of abdominal binders does not influence these physiological responses. An effect of either of these techniques on wheelchair racing performance has not been demonstrated.
[Prediction of G-load (Gz) tolerance based on various functional tests].
The purpose of the present study was to analyze and sum up the data on the methods of predicting g-tolerance (+Gz) utilizing various functional tests within the program of medical flight certification. The study involved 478 fighter pilots who were examined at the Central Military Scientific/Research Aviation Hospital. The age of examinates varied from 25 to 50 years (35 yr. on the average). Along with healthy subjects there were also pilots with the history of vascular-autonomous instability, anamnesis of syncope, myocardiodystrophy, myocardiac and atherosclerotic cardiosclerosis, and some other disorders. As a result, a correlation was established between the tolerance of lower body negative pressure at -50 mm Hg and standing tests. No link was noted between tolerance of the subjects to moderate hypoxia (H = 5,000 m for 30 minutes) and +Gz-loads at 3 and 5 units for 30 seconds. Neither was there evidence of correlation between tolerance of standing tests including their modifications and g-loads. Pearson association coefficient ra = 0.01. Comparison of the tolerance to +Gz at 3, 5, and 6 units without the anti-gravity suit and static loads at 120, 160, 200, and 240 kg/s during 30 seconds each gave an agreement of 67%. However, the statoergometry test revealed a poor tolerance of static loads only in 17.2% out of 29 pilots with low g-loads tolerance. Hence, the association coefficient appeared to be equal to 0.06 denying any predictive link. This absence of reliable predictive correlation between the tests in use was extenuated by different physiological mechanisms of adaptation.
DONNING AND DOFFING THE "PHASE B" APOLLO PROTOTYPE SPACE SUIT DURING ZERO GRAVITY . TECHN DOCUM REP NO. AMRL-TDR-64-32.
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