Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Gravity Suits”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13Linked to original sources
PubMed1983

Clinical evaluation of the antishock trouser: retrospective analysis of five years of experience.

A retrospective study of five years of experience in using pneumatic antishock trousers was undertaken to provide data for analysis of clinical response and complications associated with use of the suit. Of 1,120 patients who received pneumatic antishock trousers, 821 (73.3%) survived more than 24 hours, and their response and clinical course were analyzed. Response was not uniform: most exhibited blood pressure response, and some showed changes in only pulse rate or evidence of improved tissue perfusion. Different responses were noted for different shock etiologies. Of all the potential complications theoretically possible, a prevalence of only 4% for ischemic skin changes (none requiring grafting) and 0.97% for renal perfusion failure were noted. The pneumatic antishock trouser is thought to be beneficial and safe.

Acute Kidney Injury↗
PubMed2005

The postexercise increase in the threshold for cutaneous vasodilation and sweating is not observed with extended recovery.

The following study was conducted to evaluate the hypothesis that an increase in the postexercise onset threshold for cutaneous vasodilation (Th(VD)) and sweating (Th(SW)) would not be observed upon the restoration of baseline mean arterial pressure (MAP). Subjects remained either seated resting for 15 min or performed 15 min of treadmill running at 70% VO2peak followed by either 20- (short) or 60-min (extended) recovery. At the end of each recovery protocol (20 and 60 min) a water perfusion suit was then used to increase mean skin temperature until Th(VD) and Th(SW) was noted. Exercise resulted in an increase in Th(VD) and Th(SW) of 0.24 +/- 0.03 and 0.24 +/- 0.02 degrees C, respectively, above no-exercise for the short recovery (p < 0.05). No increase was measured for the extended recovery. Postexercise MAP was significantly reduced prior to whole-body warming for the short recovery whereas no reduction was measured for the extended recovery. The increase in Th(VD) and Th(SW), measured during the early stages of recovery, is reversed with the reestablishment of baseline MAP.

Adult↗
PubMed1978

Explosive decompression of subjects up to a 20,000-m altitude using a two-pressure flying suit.

The RSAF two-pressure flying suit system to protect the pilot at high altitude has been tested from different medical safety aspects. To secure adequate alveolar oxygen pressure, the suit admits up to 70 mm Hg (9.3 kPa) positive pressure breathing by counter-pressure against the thorax and by a 3.2 times higher pressure in the anti-G suit. After 1 h of oxygen breathing, subjects were exposed to explosive decompression from an altitude of 9,000 m to 17,500 or 20,000 m in 0.5 s in a hypobaric chamber. No symptoms of decompression sickness or of alveolar rupture with gas embolism to the central nervous system were seen. Pulmonary X-rays after the test did not reveal any signs of lung rupture with extrapulmonary gas leakage. With the precordial Doppler ultrasound technique, intracardial gas bubbles (silent bubbles) could be detected only in one subject after explosive decompression to a 20,000-m altitude in the 10 experiments.

Adult↗
PubMedDate not supplied

[Evaluation of +Gz tolerance following simulation of 8-hr flight].

Tolerance of +Gz (head-pelvis) centrifugation of pilots was evaluated following simulation of a long flight on single-seat fighter. The experiment involved 5 test-subjects who were exposed to +Gz before and after simulated 8-hr flight with a growth gradient of 0.1 u/s without anti-g suits and muscles relaxed; in addition, limiting tolerance of intricate profile +Gz loads of 2.0 to 9.0 units with a growth gradient of 1.0 u/s of test-subjects in anti-g suits (AGS) with a change-over pressure valve in the peak mode using muscle straining and breathing maneuvers. To counteract the negative effects of extended flight, various seat configurations: with a back inclination at 30 degrees to the +Gz vector and changeable geometry with a back inclination at 55 degrees to the vector. The other counter-measures applied were cool air shower, suit ventilation, physical exercises, lower body massage with AGS, electrostimulation of the back and lumber region, profiling of the supporting and soft parts of the seat, and 30-s exposure to +5 Gz. Hemodynamic and respiration parameters as well as body temperature were measured in the course of 8 hrs of flight and during and shortly after centrifugation. According to the results of the investigation, seat inclination at 55 degrees to the +Gz vector and tested system of countermeasures prevent degradation of tolerance of large (9 u.) loads following 8-hr flight simulation with the use of the modern anti-g gear,

Acceleration↗
PubMed1986

Contributions of aeromedical research to flight and biomedical science.

Pilot and plane capabilities to withstand high-Gz combat maneuvers are tactically important. Sustained 10-15 Gz capabilities of current and future planes outstrip safe physiologic limits in spite of the combined use of World War II-vintage straining maneuvers and relatively ineffective anti-G suits to prevent losses of vision and consciousness. However, the extreme arterial pressure increases needed to maintain cerebral blood flow (e.g. 400 mm Hg at heart level during exposures to 13.5 G when sitting upright) carry risks of anatomic damage to the circulatory system and rupture of air-containing, essentially unprotectable, lungs. These could be minimized, and incapacitating losses of consciousness avoided, by use of horizontal positions designed to eliminate heart-to-head hydrostatic gradients. Development of a prone-position cockpit with a counterweighted, forward-looking head support plus optical-electronically aided all-directional visibility is the most physiologic, safest, and surest way to achieve this goal.

Acceleration↗
PubMed1990

Physiologic correlates of protection afforded by anti-G suits.

A new uniform-pressure pneumatic anti-G suit (UPS) was compared with the standard CSU-13B/P anti-G suit, using measurements of: blood lactate, heart rate changes, and segmented lower-body blood pooling (by impedance plethysmography). Subjects were exposed to a series of gradual-onset-rate (GOR) runs (0.1 G.s-1), rapid-onset-rate (ROR) runs (6 G.s-1), and simulated aerial combat maneuvers (SACM) on the USAF School of Aerospace Medicine human-use centrifuge. All measured parameters and subjective reports indicated that increased protection was afforded by the UPS. The impedance plethysmography measurements indicated that prevention of blood pooling in all lower-body segments is the predominant mechanism whereby uniform pressure permits significantly longer times-to-fatigue during SACMs.

Adult↗
PubMed1986

A conceptual model for predicting pilot group G tolerance for tactical fighter aircraft.

A static model based on eye-heart vertical distance has been developed which predicts group mean G tolerances relative to the application of any of the following anti-G methods and/or physiologic responses: a) anti-G suit, b) reclined seat, c) anti-G straining maneuver (AGSM), d) positive pressure breathing (PPB), e) gradual onset of G, f) isometric muscular contraction, and g) leg elevation. This model was validated with published data. A variation of this model (derived equation) predicts the amount of AGSM (in mm Hg) required, in combination with any of the anti-G methods/responses at any G level. This calculated effort of AGSM can be equated to level of fatigue and performance decrements. A level of 50 mm Hg or an increase of 2 G in the upright seat was the maximum AGSM recommended for routine use as an anti-G method for operational fighter pilots.

Aircraft↗
PubMed1990

Atrial natriuretic factor and central venous pressure during intermittent and continuous lower-body positive pressure in healthy humans.

In eight healthy volunteers undergoing 16 experiments in a cross-over design central venous pressure (CVP) and atrial natriuretic factor (ANF) in central venous plasma were measured during a 30 min control period followed by three separated periods of 10 min lower-body positive pressure (LBPP) or 90 min continuous LBPP induced by inflation of a military anti-G suit to evaluate the effect of short repeated and of extended increases in right atrial pressure on plasma ANF levels. CVP increased significantly during each of three separate periods of intermittent LBPP, and 15 min after application of continuous LBPP (P less than 0.025 for all). Blood pressure and heart rate did not change. During intermittent LBPP plasma ANF levels increased 10 min after the first inflation of the MAGT-suit (P = 0.013), but not after the second or third inflation. During continuous LBPP plasma ANF remained unchanged until 90 min after application of LBPP where a significant rise was observed (P = 0.023). The data demonstrate that the ANF response to short-term increases in right atrial pressure, as small as 2.5 mmHg, is maximal within 10 min and that repeated pressure stimuli may decrease ANF release. Sustained increases in right atrial pressure are not associated with increases in plasma ANF until long after initiation of the pressure stimulus suggesting rapid receptor-binding of ANF and that the ANF receptors might be saturated during continuously elevated ANF levels.

Adult↗
PubMed1981

A comparison of three liquid-ventilation cooling garments during treadmill exercise.

Tests were performed on five male subjects to compare the heat transfer performance and physiological effects of three different cooling garments when used under a sealed, impermeable garment which simulated a space suit. The mean exercise metabolic rate while walking at 0.9 m/s (2 mph) was 464 +/- 33 W. An equilibrium condition was never reached during the uncooled suited control runs and the subjects lost a mean of 1.12 +/- 0.15 kg (2.5 +/- 0.3 lb)--approximately 2% of body weight--during exercise. The mean weight loss was 0.35 +/- 0.10 kg (0.8 +/- 0.2 lb) with an Apollo-type garment; 0.26 +/- 0.11 kg (0.57 +/- 0.24 lb) with the full-body cooling patch (garment 2); and 0.52 +/- 0.12 kg (1.15 +/- 0.26 lb) with the partial-coverage cooling patch (garment 3). Impedance plethysmography data showed an increase in leg blood flow when the working muscles were not cooled by liquid flow (garment 3), and the arm blood flow remained unchanged whether or not there was liquid cooling to the arms.

Adult↗
PubMed1988

Effect of lower-body positive pressure on postural fluid shifts in men.

To quantify the effect of 60 mm Hg lower-body positive pressure (LBPP) on orthostatic blood-volume shifts, the mass densities (+/- 0.1 g.1-1) of antecubital venous blood and plasma were measured in five men (27-42 years) during combined tilt table/antigravity suit inflation and deflation experiments. The densities of erythrocytes, whole-body blood, and of the shifted fluid were computed and the magnitude of fluid and protein shifts were calculated during head-up tilt (60 degrees) with and without application of LBPP. During 30-min head-up tilt with LBPP, blood density (BD) and plasma density (PD) increased by 1.6 +/- 0.3 g.1-1, and by 0.8 +/- 0.2 g.1-1 (+/- SD) (N = 9), respectively. In the subsequent period of tilt without LBPP, BD and PD increased further to + 3.6 +/- 0.9 g.1-1, and to + 2.0 +/- 0.7 g.1-1 (N = 7), compared to supine control. The density increases in both periods were significant (p less than 0.05). Erythrocyte density remained unaltered with changes in body position and pressure suit inflation/deflation. Calculated shifted-fluid densities (FD) during tilt with LBPP (1006.0 +/- 1.1 g.1-1, N = 9), and for subsequent tilt after deflation (1002.8 +/- 4.1 g.1-1, N = 7) were different from each other (p less than 0.03). The plasma volume decreased by 6.0 +/- 1.2% in the tilt-LBPP period, and by an additional 6.4 +/- 2.7% of the supine control level in the subsequent postdeflation tilt period. The corresponding blood volume changes were 3.7 +/- 0.7% (p less than 0.01), and 3.5 +/- 2.1% (p less than 0.05), respectively. Thus, about half of the postural hemo-concentration occurring during passive head-up tilt was prevented by application of 60 mm Hg LBPP.

Adult↗
PubMed1989

Effects of dipyridamole on the cardiovascular response to +Gz stress in miniature swine.

Eight conscious female miniature swine experienced acceleration levels of 3, 5, and 7 +Gz before and after infusion of dipyridamole (1-2 mg.kg-1). Each animal was instrumented to measure ECG, heart level arterial pressure (AP), eye level arterial pressure (ELBP), left arterial pressure (LAP), heart rate (HR), and regional tissue blood flows. Each was also fitted with an abdominal anti-G suit which automatically inflated. Dipyridamole infusion had no direct effect on HR or LAP but AP was significantly reduced. All cardiovascular responses to +Gz were qualitatively similar before and after dipyridamole. Tachycardia always occurred. AP and CNS blood flow were maintained better prior to dipyridamole and AP always fell in proportion to acceleration intensity. +Gz was generally associated with increased blood flow to respiratory muscles and heart, decreased blood flow throughout the viscera and to the eyes. ELBP paralleled AP, but was always lower in direct proportion to the +Gz level. We conclude that dipyridamole reduces arterial pressure thus compromising the ability of the animal to sustain cerebral perfusion pressure (ELBP) during +Gz.

Animals↗
PubMed1994

U.S. Air Force positive-pressure breathing anti-G system (PBG): subjective health effects and acceptance by pilots.

Current high-performance fighter aircraft subject pilots to acceleration forces that can adversely effect performance and induce unconsciousness during flight. The main strategies to help the fighter pilot sustain +Gz include a pressurized anti-G garment (G-suit), the anti-G straining maneuver, and centrifuge training to optimize this effective, but very fatiguing, maneuver. To improve anti-G support for aircrew, a positive-pressure breathing anti-G system (PBG) has been developed in the COMBAT EDGE program. In order to determine if any acute adverse health effects are occurring from the use of PBG, a survey of 241 (F-15 and F-16) pilots (49 using PBG and 192 using standard methods) was conducted. Questions were asked regarding acute health effects and the impact of PBG on mission accomplishment. With the exception of dry cough, no significant increases in adverse events were found, and acceptance in the F-16 was much greater than in the F-15.

Adult↗
PubMed1980

Aspects of the management of shock.

Shock is a state of systemic imbalance between supply and demand for oxygenated blood. We discuss here management of shock states not primarily of cardiac origin. Inadequacy or maldistribution of blood volume is important in the pathogenesis of most forms of shock. The Military Anti-Shock Trouser (MAST) suit assists the redistribution of blood from the periphery to the central circulation. Normal saline and Ringer's lactate solution may be used interchangeably for acute volume replacement. Colloid replacement requires smaller volumes but carries a higher risk of pulmonary edema, whereas crystalloid replacement requires larger volumes and leads to more systemic edema. Myocardial injury may contribute notably to the transition from reversible to irreversible shock. Naloxone, lidocaine, and indomethacin have improved survival in animal models of endotoxin shock, but proof of efficacy in humans is lacking. A role for corticosteroid administration in shock remains to be defined. Effective antibiotic therapy is the best treatment for septic shock; antisera against endotoxic antigens may develop as important adjunctive therapy.

Animals↗
PubMed1980

Hemodynamic effects of extreme positive pressure breathing using a two-pressure flying suit.

The central hemodynamics during extreme positve pressure breathing (PPB) with 4.0-9.3 kPa breathing pressures using a two-pressure flying suit was studied with the thermodilution technique. Pressures measured simultaneously in right atrium, pulmonary artery, and systemic circulation increased in proportion to, but somewhat less than, the breathing pressures. A decreased transmural right atrial and pulmonary arterial pressure was found during PPB to be most pronounced during simultaneous counterpressure to the thorax. Stroke volume (SV) as well as cardiac output (CO) decreased successively during PPB, mostly during PPB with more than 4 kPa. Simultaneous counterpressure to the thorax added further hemodynamic effects. During recovery after PPB, a marked compensatory increase in SV and CO was registered. An increased systemic blood pressure and heart frequency was found at all levels of PPB, suggesting that PPB may be of value to increase G tolerance.

Adult↗
PubMed2003

Cerebral blood flow during acceleration in flight measured with SPECT.

INTRODUCTION: Positive pressure breathing for G-protection (PBG) reduces the need for fighter pilots to use the fatiguing anti-G straining maneuver (AGSM) so that they can better endure high acceleration (+Gz). The aim of the study was to determine the differences in cerebral blood flow during flight with an extended-coverage anti-G suit (ECGS) with AGSM or with PBG. METHODS: Subjects were eight male members of the Finnish Air Force. Each was studied in the laboratory at +1 Gz and then during two identical flights in the back seat of the BAe Hawk Mk 51 jet trainer at +6 Gz, first with AGSM and second with PBG (24 mmHg). Regional cerebral blood flow (rCBF) was measured by injecting (99 m) Tc-ECD for deposition at +6 Gz, then scanning the subject in the laboratory an hour later using single photon emission computed tomography (SPECT). RESULT: The rCBF was 30% below baseline for both the AGSM and PBG. CONCLUSIONS: PBG maintained CBF at +6 Gz without the need for the fatiguing AGSM.

Adult↗
PubMed1979

Physiological effect of high, sustained +Gz forces on man.

Two studies were conducted to evaluate physiological responses and possible tolerance to high sustained +Gz forces at the USAF School of Aerospace Medicine, using the 20-ft (6.10 m) radius Human Centrifuge. In the first study (A), 14 human volunteer subjects--fully protected with an anti-G suit and performing the M-1 or L-1 straining maneuver--were exposed to +Gz forces. These forces began at +6.5 Gz, and increased weekly in 0.5 G increments to +9.0 Gz, for a duration of 45 sec at each level. Physiological performance was based mostly on the subjects' ability to maintain clear vision during the 45 sec exposure. Of the 14 subjects, 9 were able to maintain vision and remain at the +9 Gz level for 45 sec. In the second study (B), 12 human volunteer subjects--also protected with anti-G suits and using the straining maneuvers--were exposed to levels of +1, 3, 6, and 8 Gz, for 60 sec at each level. Extensive physiologic parameters were recorded in order to detect objective criteria which could be used as determinants for a medical tolerance endpoint to the particular level of +Gz stress. In both studies, the reasons for stopping the runs at levels exceeding +7.5 Gz included: fatigue, cardiac arrhythmias, blackout, and one occurrence of ventricular tachycardia. Other physiological responses to the sustained +Gz stress (such as heart rate, arterial blood pressure, central venous blood pressure, arterial oxygen saturation, gastric pressure, and ankle venous pressure) did not furnish specific information that could be used as "physiological tolerance limit" criteria.

Acceleration↗
PubMed1999

[Integrated protection capability afforded by a new type capstan anti-G equipment and anti-G straining maneuver].

Objective. To investigate the integrated protection capability afforded by a new type capstan anti-G equipment and anti-G straining maneuver, as a result we discussed the feasibility of protection for 8 G 10 s (rapid onset runs at 2 G/s) acceleration using an associated precept with the above both anti-G measures. Method. This study was accomplished using the human centrifuge with rapid onset at 2 G/s. First, we determined the relaxed +Gz tolerance of nine male aviation students, and then determined theirs most + Gz tolerance while thereinto the five aviation students using a new type capstan anti-G suit (NKH) + a new type anti-G valve (NKT) + L-1 anti-G straining maneuver (L-1) and the other four aviation students using a new type capstan counterpressure suit (NDC) + the new type anti-G valve (NKT) + L-1. Result. The most +Gz tolerance of five students was 8.80 +/- 0.27 G while using NKH + NKT + L-1 and was higher than their relaxed +Gz tolerance at 4.60 +/- 0.42 G (P< 0.01) and that the most +Gz tolerance of four students was 8.75 +/- 0.50 G while using NDC + NKT + L-1 and was higher than their relaxed +Gz tolerance at 4.50 +/- 0.46 G (P< 0.01). Conclusion. Pilot will be capable against the 8 G 10 s (rapid onset runs at 2 G/s) effectively using the new type capstan anti +/- G equipment and anti +/- G straining maneuver, and the provided precept has availability.

Acceleration↗
PubMedDate not supplied

Countermeasure of the negative effects of weightlessness on physical systems in long-term space flights.

The system of countermeasure of microgravity effects has been developed in Russia that allowed to perform safely long-term space flights. This system that includes different means and methods such as special regimens of physical exercises, axial loading ("Pingiun") and antigravity suits, low body negative pressure device (LBNP, "Chibis") and "cuffs" and others has been used with certain variations at certain stages of flight in 27 successfully accomplished space flights that lasted from 60 to 439 days. The pre-, in- and postflight studies performed in 57 crew members of these flights have shown that the system of countermeasure is effective in preventing or diminishing to a great extent almost all the negative effects of weightlessness in flights of a year and more duration and that the intensity and duration of changes recorded in different body systems after flights do not correlate significantly to flight durations, correlating strongly to the volume and intensity of physical exercises used during flight and especially during concluding stage of it.

Aerospace Medicine↗