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 217 records · Page 12Linked to original sources
PubMed1991

A case of hemidiaphragmatic paralysis after an anti-G suit failure.

This paper reports a case of left hemidiaphragmatic paralysis in an instructor pilot and his later recuperation. This incident was provoked by a failure in the anti-G suit, which remained inflated after the aircraft completed the maneuver that had originated the inflation. The spontaneous recuperation of both the respiratory functional test and the neurophysiological pattern are consistent with a Type II Seddon's axonotmesis of the phrenic nerve. Considering the short time of regeneration (6 months), this lesion must have involved the distal portion of the phrenic nerve.

Adult↗
PubMed1987

Probability of oxygen toxicity using an 8 psi space suit.

Breathing oxygen at high partial pressure is toxic to all systems of the body. However, the effect a of a high PO2 on the pulmonary and erythropoietic systems pose the greatest threat to the EVA astronaut utilizing a single gas space suit system. Oxygen toxicity has been studied extensively, and a review of the literature suggests that continuous exposure to a PO2 of 8 psi can be tolerated indefinitely and should not present the astronaut with a problem for the Extravehicular Activity (EVA) scenarios projected for Space Station. However, the cause of the decrease in circulating red blood cell mass, which has been shown to accompany exposure to microgravity as well as hyperoxemia, is not as well defined when both conditions are simultaneously present.

Decompression↗
PubMed1993

Overhead and forward reach capability during exposure to +1 to +6 Gx loads.

The lack of reach performance data obtained under space-flight conditions has led to questions regarding the operational impact of higher G loads on crew performance. This investigation studied the effect of increasing G loads on reach capability. Ten subjects were exposed in a stepwise fashion to increasing accelerations resulting in G loads of from +1 to +6 Gx in the Brooks AFB centrifuge. Four subjects wore the pre-Challenger Launch Entry Helmet (LEH) ensemble and six the current Launch Entry Suit (LES). The subjects performed standardized reach sweeps at each G level. These sweeps were recorded on videotape and subsequently analyzed using a 3-dimensional motion analysis system. Significant differences in forward and overhead reach were determined using the General Linear Models (GLM) procedure of the Statistical Analysis System (SAS) program. The results from this study suggest that purposeful movement can be realistically performed in the LEH at the 5 G level and in the LES up to the 4 G level.

Gravitation↗
PubMed2003

Pressure breathing in fighter aircraft for G accelerations and loss of cabin pressurization at altitude--a brief review.

PURPOSE: The purpose of this brief review is to outline the past and present use of pressure breathing, not by patients but by fighter pilots. SOURCE: Of the historical and recent references quoted, most are from aviation-medicine journals that are not often readily available to anesthesiologists. PRINCIPAL FINDINGS: Pressure breathing at moderate levels of airway pressure gave World War II fighter pilots a tactical altitude advantage. With today's fast and highly maneuverable jet fighters, very much higher airway pressures of the order of 8.0 kPa (identical with 60 mmHg) are used. They are used in conjunction with a counterpressure thoracic vest and an anti-G suit for the abdomen and lower body. Pressurization is activated automatically in response to +Gz accelerations, and to a potentially catastrophic loss of cabin pressurization at altitude. During +Gz accelerations, pressure breathing has been shown to maintain cerebral perfusion by raising the systemic arterial pressure, so increasing the level of G-tolerance that is afforded by the use of anti-G suits and seat tilt-back angles alone. This leaves the pilot less reliant on rigorous, and potentially distracting, straining maneuvers. With loss of cabin pressurization at altitude, pressure breathing of 100% oxygen at high airway pressures enables the pilot's alveolar PO(2) to be maintained at a safe level during emergency descent. CONCLUSION: Introduced in military aviation, pressure breathing for G-tolerance and pressure breathing for altitude presented as concepts that may be of general physiological interest to many anesthesiologists.

Acceleration↗
PubMedDate not supplied

Unconsciousness in flight and its prevention.

The physiological mechanism underlying two of the most potent causes of loss of consciousness in flight, viz. hypoxic hypoxia and exposure to rapid onset of high +GZ accelerations have been explored in this paper, using principally experimental work conducted at the Royal Air Force Institute of Aviation Medicine. The influence of the composition of the gas breathed before and after sudden decompression of the pressure cabin of an aircraft at high altitude has been described together with the physiological basis of the present standards for preventing disturbances of performance due to hypoxia following rapid decompression. The value and limitations of pressure breathing with oxygen at high pressures in preventing hypoxia on exposure to altitudes above 40,000 feet have been discussed together with the series of partial pressure suits used in the Royal Air Force. The mechanisms and occurrence of G-induced loss of consciousness in pilots of combat aircraft have been reviewed. The increasing likelihood of loss of consciousness due to G in new very agile combat aircraft is considered together with the limitations of the standard methods of enhancing G tolerance. The adoption and development of pressure breathing together with chest counterpressure and extended-cover G trousers which provide excellent protection against high levels of acceleration is described.

Acceleration↗
PubMed1994

[Intra-abdominal pressure].

The abdominal pressure is a hydrostatic one, which can be measured in the bladder, the rectum and the stomach. In physiologic conditions, the abdominal pressure is variable, with peaks as high as 100 to 200 mmHg at the time of defecation, cough. The increase in abdominal pressure elicited by abdominal distension or compression acts directly on the abdominal compartment, indirectly on the thoracic compartment, and modifies the circulation and the ventilation. Venous return is decreased as the inferior vena cava is compressed. The systemic resistances are also increased as the abdominal vessels are compressed. Therefore the circulation is mainly distributed to the superior part of the body. Although the cardiac output is decreased, the usual haemodynamic parameters remain in the normal range: arterial pressure is increased, heart rate is unchanged, central venous pressure is increased, cardiac failure is unusual. The abdominal distension is also responsible for a restrictive respiratory syndrome, mainly due to the ascension of the diaphragm. The compression of the abdominal content explains renal effects and the decreased diuresis. A sustained increase in abdominal pressure occurs in several clinical conditions. During coelioscopy, abdominal pressure is a under control and the cardiovascular effects are minor. Insufflation with CO2 carries the risk of hypercapnia, gas embolism and pneumothorax. During abdominal tamponade, anuria is directly related to the level of pressures. At an abdominal pressure over 25 mmHg, anuria is common and decompression becomes essential. The G suit increases arterial pressure either by elevating vascular resistances or increasing blood content in the upper part of the body. Therefore cardiac tolerance can be decreased especially in cardiac patients. The adverse effects of abdominal pressure can also be observed in case of peritoneal dialysis and ascites. The risk of regurgitation associated with an increased abdominal pressure must also be kept in mind. The abdominal pressure plays an important role in anaesthesia as well as in surgery. Therefore its measurement, which is easy, should become a routine.

Abdomen↗
PubMed1981

Hemodynamic effects of Medical Anti-Shock Trousers (MAST garment).

Despite widespread use of the Medical Anti-Shock Trousers (MAST) little is known about the exact mechanism by which they increase arterial pressure. It is assumed that an autotransfusion occurs. To examine this question, blood pressure, heart rate, forearm blood flow, cardiac output, and stroke volume were measured in ten healthy adults, supine and during 60 degree headup tilt with MAST garment pressures of 409 and 100 mm Hg. Supine, the garment produced no net 'autotransfusion,' but raised blood pressure (27%) by increasing peripheral resistance (48%) with decreased stroke volume and cardiac output (18%). During headup tilt without the MAST device, venous pooling in the legs decreased stroke volume (52%), cardiac output (30%), and increased total peripheral resistance (40%). Application of the garment during tilt shifted this blood centrally, producing increased stroke volume (52%), cardiac output (30%), and increased total peripheral resistance (40%). Application of the garment during tilt shifted this blood centrally, producing increased stroke volume (14%). In supine normovolemic subjects, the garment raised pressure almost exclusively by increased systemic afterload. Forearm vascular resistance did not change and the increased pressure augmented flow to the arm, i.e., to noncompressed tissue. With increased venous pooling during tilt, the MAST garment acted as a 'G-suit' and caused a central shift of blood volume. These findings could explain: 1) why fluid replacement is not always adequate to maintain pressure when deflating the trousers; 2) why the trousers should not be used if one wishes to avoid increasing afterload (e.g., certain patients with acute myocardial infarction). We conclude that the MAST garment acts as a local, effective, nonpharmacologic vasoconstrictor and should be used when such an effect is clinically appropriate.

Adolescent↗
PubMed1993

Guidelines for a research and development (R&D) program for high sustained G.

This article is a contribution to the workshop on "Operational Requirements in the Prevention of G-Induced Loss of Consciousness (G-LOC) in High Performance Aircraft"; it focuses on the "operational" side of the requirements to prevent G-LOC. There are two types of requirements for prevention of G-LOC; a) pre-G-LOC detection devices that monitor physiologic changes of the pilot before G-LOC occurs, and b) the more generic personal G protection systems that increase G tolerance. Recently there have been major advances in G-protection research and development (R&D) systems (soon to become operational) that significantly improve G-level and G-duration tolerances. We do not know the extent of the impact of these new systems on G-LOC, but it could be substantial. These near-term operational anti-G systems are: 1. Positive pressure breathing (PPB) systems assisted by chest counterpressure that are activated by an increase in G levels; i.e., the higher G level, the greater the pressures applied to the aircrew member (Morgan et al., 1992). This PPB system is known as PBG. PBG has been flight tested with the standard operational anti-G suit. This test program known as Combat Edge significantly reduces pilot fatigue and extends G-duration tolerance. In limited operational testing of F-16 and F-15 aircraft, PBG has received substantial pilot acceptance. 2. An improved anti-G suit that provides uniform pressure of the lower body that includes the operational anti-G suit abdominal bladder. This new anti-G suit concept increases both G-level and G-duration tolerances (Krutz et al., 1990; Morgan et al., 1992). Flight tested as the Advanced Tactical Anti-G Suit (ATAGS), it is comfortable and preferred by pilots over the standard operational anti-G suit. 3. The combination of Combat Edge and ATAGS, the most advanced anti-G system in the final stages of development (Morgan et al., 1992). This anti-G equipment has been tested in the laboratory on the centrifuge. Experimental subjects are able to tolerate 8 to 9G "relaxed" or with a minimal anti-G straining maneuver (AGSM) (Morgan, 1992). Accleration scientists believe that once these systems become operational on high performance aircraft that the incidence of G-LOC will be significantly reduced, particularly G-LOC associated with fatigue.

Aerospace Medicine↗
PubMedDate not supplied

[Evaluation of the effectiveness of antishock suits at the early stages of the treatment of patients with traumatic shock].

The efficacy of the early use of antishock overalls (ASO) as part of intensive care for traumatic shock is assessed in the clinical study performed in 15 patients with severe mechanical trauma complicated with shock. Hemodynamic parameters were compared in groups where ASO was and was not used as part of antishock procedures. High efficacy of ASO use for stabilization of hemodynamic parameters in patients with severe trauma complicated with shock has been demonstrated and the advisability of its use in the complex of intensive care procedures in traumatic shock at prehospital stage has been proved.

Gravity Suits↗
PubMed2003

[The sitting position in neurosurgical anaesthesia: a survey of French practice].

INTRODUCTION: It remains a French and international controversy about the use of the sitting position in neurosurgery. The aim of this study was to evaluate the frequency of sitting position use, perioperative monitoring and procedures for air embolism detection and treatment. STUDY DESIGN: National postal survey. PATIENTS AND METHODS: The survey was sent in may 2000 to the anaesthesiologists in 53 french public neurosurgical centers. Responses were collected during 9 months. RESULTS: Among the 44 centers (83%), 33 (75%) used the sitting position. In 20 centers (61%) it was limited for the surgical procedures for which the surgeon was unable to operate in other position. Perioperative monitoring for air embolism was: capnography (100%), Swan-Ganz catheter (21%), precordial Doppler ultrasonography (15%) and transoesophageal echocardiography (6%). Only 12 centers (36%) used 2 or more techniques of detection for perioperative air embolism. In the 25 centers (76%) of those, which used the sitting position systematic pre-operative identification of patent foramen ovale by contrast echocardiography was performed. Prevention procedures of air embolism were: plasma volume expansion (94%), antigravity suit (61%), mechanical ventilation with positive end-expiratory pressure (42%), and abdominal compression (24%). No protocol of air embolism prophylaxis was used in 18 centers. CONCLUSION: The survey concerned 83% of the centers. The number of centers using the sitting position was larger than in other countries like United Kingdom, Germany and Japan. Despite its lack of sensitivity capnography was universally practised. Preoperative contrast echocardiography for patent foramen ovale detection was not considered as necessary in all centers. Expert recommendations may be required.

Blood Gas Analysis↗
PubMed1985

The use of plastic face mask and silicone gloves and boots as alternative to compression suits for treating hypertrophic scars.

Prevention and treatment of hypertrophic scars and contractures is usually obtained by the use of compression suits. The compression hood for the burned face is unaesthetical and often refused by the child. A better compression can be obtained by the use of a clear transparent plastic mask. It offers a better view and looks better, thus increasing the cooperation of the patient. Compression gloves and stockings are difficult to adapt to. It is easier to make mittens and boots out of silicone. These two techniques meet the criteria of efficiency: early application of compression, good tolerance, splint support, individually moulded splints for optimum pressure and cooperation.

Burns↗
PubMed1994

Preinflation before acceleration on tolerance to simulated Space Shuttle reentry G profiles in dehydrated subjects.

This study was conducted to determine if preinflation of a standard five-bladder anti-g suit 10 minutes before exposure to a centrifuge simulation of a Space Shuttle reentry would provide significantly better protection against orthostasis than the standard symptomatic inflation regimen. This study differed significantly from prior studies: The rate of g onset was slower, peak g was lower, duration of exposure was longer, and the subjects were dehydrated to mimic conditions observed in astronauts immediately postflight. Preinflation demonstrated physiological advantages as determined by arterial blood pressure and heart rate changes in seven healthy male, experienced centrifuge subjects.

Acceleration↗
PubMed1988

Hemorrhage in major pelvic fractures.

Significant hemorrhage following major pelvic fractures should always be expected. Early recognition of such fractures during the resuscitation of any multiply injured patient is essential before instituting measures that might combat blood loss. In the majority of patients, simple resuscitative measures, including employment of the pneumatic antishock garment, will suffice. With certain types of fracture geography, the early application of external fixation devices may also play an important role. Increasingly popular has been the technique of diagnostic angiography and therapeutic embolization, applicable to approximately 3 per cent of all pelvic fracture patients. With exsanguinating hemorrhage, even the best equipped and most sophisticated major trauma centers can be taxed. The decision whether a patient should be taken directly to the operating room or to the angiography suite remains one of the most difficult for even the most highly skilled trauma surgeon. Patients with rapidly expanding or free rupture of pelvic hematomas noted at the time of celiotomy, or those with large open wounds, usually leave no recourse but to attempt direct operative control, to include even the most morbid option of a life-saving hemipelvectomy or corpectomy. More often, however, once other sources of surgically correctable hemorrhage are controlled or ruled out, diagnostic angiography followed by therapeutic embolization is a mainstay in the modern-day management of pelvic fracture hemorrhage.

Embolization, Therapeutic↗
PubMed1991

Thoracocardiography. Part 2: Noninvasive measurement of changes in stroke volume; comparisons to impedance cardiograph.

The thoracocardiograph (TCG) displays cardiac oscillations transmitted to the external surface of the thorax through inductive plethysmographic transducers placed transversely around the thorax near or about the xiphoid process. Such signals, with the appearance of ventricular volume curves, were used to compute changes of stroke volume (SV) and cardiac output (CO) in normal subjects. Their values were compared with changes of SV and CO measured with the impedance cardiograph (IC). Increases of SV and CO were produced with subcutaneous terbutaline and there was excellent agreement between TCG and IC values, best from TCG transducers placed at the xiphoid process and 3 cm caudal to it, although TCG locations 6 cm caudad and 3 cm cephalad to the xiphoid were also satisfactory. Since the site 3 cm caudad to the xiphoid process is known to anatomically transect solely a segment of the left ventricle, it was designated the TCG-Reference location. Both TCG and IC derived SV were not altered during postural shifts about a horizontal axis. Neither TCG nor IC showed the expected large decreases of SV from supine posture to head-up tilt. With baseline TCG and IC measurements in 60 degrees head-up tilt. MAST suit application increased CO measured with TCG but not with IC. Neither TCG nor IC revealed alteration of CO with nasal CPAP up to 10 cm H2O despite a rise in functional residual capacity (FRC) level of 870 ml. This investigation indicates that TCG has promise as a near continuous, noninvasive monitor of SV and CO in normal subjects if postural axis is fixed and does not require highly trained personnel or labor-intensiveness for its operation.

Adult↗
PubMed1994

The influence of the AGSM, PBG, and anti-G suit inflation on thoracic hemodynamics during +Gz in swine.

With the advent of pressure breathing for +Gz (head-to-foot inertial loading) protection (PBG) and the development of improved extended coverage anti-G suits (ECGS) it has become important to expand our knowledge of the cardiopulmonary physiologic interrelationships of pressure breathing, anti-G suit protection, and the anti-G straining maneuver (AGSM). Although high levels of pressure breathing have been previously investigated, there was continuing concern within the aeromedical community regarding the introduction of COMBAT EDGE, a PBG system. Some of the concerns were: barotrauma, pneumothorax, air embolism, excessive transmural vascular pressures, possible cardiac valvular damage, and possible overdilation of the right ventricle from a surge in venous return following +Gz. This study describes the experimental preparation and results of a hemodynamic investigation to address some of these concerns using chronically instrumented miniature swine (MS).

Animals↗
PubMed1992

Comparison of current Shuttle and pre-Challenger flight suit reach capability during launch accelerations.

The Challenger accident prompted the creation of a crew escape system which replaced the former Launch Entry Helmet (LEH) ensemble with the current Launch Entry Suit (LES). However, questions were raised regarding the impact of this change on crew reach capability. Our study addressed the question of reach capability and its effect on realistic ground-based training for Space Shuttle missions. Eleven subjects performed reach sweeps in both the LEH and LES suits during 1 and 3 Gx acceleration trials in the Brooks AFB, TX, centrifuge. These reach sweeps were recorded on videotape and subsequently analyzed using a three-dimensional motion analysis system. The ANOVA procedure of the Statistical Analysis System (SAS) program was used to evaluate differences in forward and overhead reach. The results showed that the LES provided less reach capability than its predecessor, the LEH. This study also demonstrated that, since there was no substantial difference between 1 and 3 Gx reach sweeps in the LES, realistic Shuttle launch training may be accomplished in ground-based simulators.

Acceleration↗
PubMed1992

Delayed orthostatic intolerance.

In seven patients who presented with lightheadedness, fatigue, "weakness," and sometimes syncope, blood pressure was found not to fall after standing for 3 to 4 minutes but to fall severely, frequently with syncope or presyncopal symptoms, after 13 to 30 minutes when measured every minute with an automatic device. This delayed orthostatic hypotension could be corrected with inflation of a pressure suit to 45 mm Hg. Its mechanism was further investigated with measurements of plasma catecholamines, plasma cortisol and aldosterone responses to corticotropin, and the effects of norepinephrine infusions on blood pressure and venous contractility. There was normal or excessive orthostatic norepinephrine release in all patients, evidence of impaired venous innervation in the legs in some, and various disorders in the other patients. Since therapeutic improvement in the orthostatic hypotension greatly reduced the symptoms, we concluded that orthostatic hypotension occurring after more than 10 minutes of standing is a potentially debilitating and often correctable disorder.

Adrenal Cortex Function Tests↗
PubMed1992

Maximum intra-thoracic pressure with anti-G straining maneuvers and positive pressure breathing during +Gz.

Positive pressure breathing during +Gz (PBG) and anti-G straining maneuvers (AGSM) each improve +Gz tolerance by increasing blood pressure through increases in intra-thoracic pressure, but the maximal intra-thoracic pressure from their combined effect is not known. Six subjects performed the following: 1) maximal AGSM at +1 Gz; 2) assisted PBG (constant 60 mm Hg) at +Gz; 3) submaximal AGSM at +Gz (enough to maintain peripheral vision); 4) maximal AGSM at +Gz; and 5) combined PBG and maximal AGSM at +Gz. They wore TLSS mask/helmet ensemble, CSU-15/P G-suit, and TLSS-style jerkin. Intra-thoracic pressure was measured with a catheter-tip pressure transducer in the esophagus (Pes). The change in gastric pressure was also measured (delta Pga). For both Pes and delta Pga, there were no significant differences among experimental conditions (1), (4) and (5), as above. Group mean Pes and delta Pga in these three conditions were 139 and 197 mm Hg, respectively. The similar results between maximal AGSM, and maximal AGSM and PBG are explained by limited support from the thoracic counter-pressure garment, and the characteristics of the respiratory system.

Blood Pressure↗