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PubMed1995

Advanced Crew Escape Suit.

Design of the S1032 Launch Entry Suit (LES) began following the Challenger loss and NASA's decision to incorporate a Shuttle crew escape system. The LES (see Figure 1) has successfully supported Shuttle missions since NASA's Return to Flight with STS-26 in September 1988. In 1990, engineers began developing the S1035 Advanced Crew Escape Suit (ACES) to serve as a replacement for the LES. The ACES was designed to be a simplified, lightweight, low-bulk pressure suit which aided self donning/doffing, provided improved comfort, and enhanced overall performance to reduce crew member stress and fatigue. Favorable crew member evaluations of a prototype led to full-scale development and qualification of the S1035 ACES between 1990 and 1992. Production of the S1035 ACES began in February 1993, with the first unit delivered to NASA in May 1994. The S1035 ACES first flew aboard STS-68 in August 1994 and will become the primary crew escape suit when the S1032 LES ends its service life in late 1995. The primary goal of the S1035 development program was to provide improved performance over that of the S1032 to minimize the stress and fatigue typically experienced by crew members. To achieve this, five fundamental design objectives were established, resulting in various material/configuration changes.

Astronauts↗

PubMed2002

[+Gz protection of the on board oxygen generating system (OBOGS) and anti-G equipment].

OBJECTIVE: To investigate the +Gz protection of the on board oxygen generating system (OBOGS) and anti-G equipment. METHOD: Physical and physiological tests of the OBOGS and anti-G equipment were accomplished using human centrifuge. +Gz tolerance of ten male subjects with or without the anti-G suit, pressure breathing for G (PBG) and OBOGS were determined. RESULT: The performance of the OBOGS and anti-G equipment fulfilled the requirements. The +Gz protections of the anti-G suit, PBG, and anti-G system were 2.08 G, 1.92 G, and 3.92 G, respectively. CONCLUSION: The +Gz protection of the OBOGS and anti-G equipment satisfy the performance requirements of high performance aircraft.

Acceleration↗

PubMed1993

Perfusion of the visual cortex during pressure breathing at different high-G stress profiles.

The effects of pressure breathing for G protection (PBG) on perfusion of the visual cortex were studied in a subject during various high-G stress profiles. Blood flow velocity was measured in the posterior cerebral artery using a transcranial Doppler (TCD) ultrasound instrument. The G profiles examined included gradual and rapid onset rates. Mean cerebral blood flow velocity (MCBFV) declined with increasing +Gz with G-suit protection alone. The MCBFV increased in direct proportion with increase in +Gz acceleration with PBG. The mediating mechanisms for the effects of PBG may include improved gaseous exchange, the diminished sympathicoadrenal discharges, and cardiopulmonary reflexes. A role for TCD in further research is indicated.

Adult↗

PubMed1975

[The use of the "anti-G-suit" during operations in the sitting position as a treatment of postural hypotension.(author's transl)].

The use of the "Anti-G-Suit" in patients with postural hypotension is described. Acute falls in the blood pressure during operations in the sitting position can be successfully treated with the aid of an external counterpressure garment reaching from ankles to xiphoid process. The mean increase in systolic blood pressure was about 60% in hypotensive and 17% in normotensive control patients. A reciprocal relation between pre-treatment blood pressure and its increase after use of the "G-Suit" was noticed. In contrast to previous practice, we were able to operate on all hypotensive patients in poor condition. The effect of external counterpressure on the lower part of the body can be explained by increase of peripheral resistance and decrease of vascular flow, resulting in better venous return, displacement of the circulating blood above the diaphragm and augmentation of systolic blood pressure.

Gravity Suits↗

PubMed1996

Implementation of a computer-controlled life support system in the acceleration research environment.

Electronic control of the G-valve and pressure breathing regulator is being implemented in some advanced life support systems used in aircrew protection. This technological improvement, however, has not reached its full potential in the research environment. A computer-controlled life support system interface providing programmable schedules for G-suit inflation and positive pressure breathing during +Gz (PBG) was developed. Output pressures from a G-valve and pressure breathing regulator (Carleton Technologies) were controlled by a Macintosh computer running LabVIEW software. Required pressures were determined as functions of single or multiple control inputs (i.e. +Gz level, a pressure signal, time, etc.). Subject safety was ensured via hardware limitations and status checks incorporated into the software. Experiments conducted at +1 Gz and at various +Gz levels evaluated the computer software-life support hardware interface. Open-loop algorithms allowed independent control of multiple regulators using simple (single input) and complex (multiple input with adaptive loop) control structures. The system provided accurate and reproducible G-suit and mask pressures. Time of inflation, peak pressure attained, and deflation rate were effectively controlled at all +Gz levels. The ability to alter the pressure schedules independent of +Gz or time allowed comprehensive control over all parameters necessary to conduct acceleration research involving advanced life support systems.

Aerospace Medicine↗

PubMedDate not supplied

[Possibility of the development of decompression sickness during testing of G suits].

This paper presents the results of 1179 altitude chamber tests of special suits performed by 193 subjects. The probability of altitude decompression disease observed during 29 experiments (2.5%) in 26 test subjects (13.4%) is calculated. The safety of decompression tables is evaluated as applied to the pressure 14-43 kPa after oxygen breathing for 0.25-2 hrs at sea level or for 1-6 hrs at 40 kPa.

Accidents↗

PubMed1992

The effect of an anti-G suit on cardiovascular responses to exercise in persons with paraplegia.

The purpose of this study was to determine whether external pressure on legs and abdomen could prevent venous blood pooling in persons with paraplegia and thus positively affect their cardiovascular responses to arm exercise. To investigate this, five male subjects with paraplegia (P), with complete lesions between T6 and T12, and five male control subjects who were wheelchair bound (C) (due to a chronic lower extremity disability), performed submaximal arm-cranking exercise at 20%, 40%, and 60% of their maximal power output (Wmax), with and without an antigravity (anti-G) suit inflated to 52 mm Hg (1 psi). For P, higher preexercise systolic pressure (127 vs 117 mm Hg) was seen with the anti-G suit. At 40 and 60% Wmax, significantly lower heart rates (at 40% = 5.7%; at 60% = 10.6%) at similar cardiac outputs were seen for P with an anti-G suit. Although not significant, P also demonstrated higher stroke volumes at 40% (4.8%) and 60% (5.0%) Wmax with external pressure. For C, no differences in preexercise blood pressure or cardiovascular responses at all three exercise levels were seen with or without the anti-G suit. These data suggest that an inflated anti-G suit is able to prevent venous blood pooling and offers hemodynamic benefits in persons with paraplegia during submaximal arm-cranking exercise. In addition, this study reports a possible alternative to hosiery or functional neuromuscular stimulation that could be applied to all subjects with spinal cord injuries regardless of type or duration of the lesion or of muscle-atrophy.

Adult↗

PubMed1992

Determination of a pressure breathing schedule for improving +Gz tolerance.

A base of empirical data for developing optimal pressure breathing during +Gz (PBG) schedules is lacking. Relaxed +Gz-intensity tolerance with PBG was measured during gradual +Gz-onset rate centrifuge profiles using standard lightbar criteria. Constant PBG levels ranging from 18-73 mm Hg were randomly assigned. G-suit pressure followed the standard or an increased inflation schedule. Nine subjects wore a jerkin, CSU-15/P G-suit, and TLSS helmet and mask. With mean mask cavity pressures of 0, 18, 38, 60, and 73 mm Hg, corresponding +Gz-tolerances (mean +/- S.E.M.) were: 5.3 +/- 0.2, 5.8 +/- 0.1, 6.6 +/- 0.2, 7.3 +/- 0.3, and 7.5 +/- 0.3 Gz (linear correlation, r = 0.994). Increased G-suit pressure did not change the +Gz-tolerance improvement with PBG. The inverse of individual subject regression slopes ranged from 22.6 to 58.1 mm Hg/+Gz. Considering additional factors and adequate +Gz protection for all subjects while relaxed, the proposed schedule would apply 42 mm Hg PBG/+Gz beginning at +3.3 Gz with a maximum pressure of at least 73 mm Hg.

Adult↗

PubMed1983

Combining techniques to enhance protection against high sustained accelerative forces.

Five volunteer subjects were tested for acceleration tolerance under eight different experimental conditions representing relaxed and unprotected tolerance and tolerance with all possible combinations of the Anti-G suit, the M-1 maneuver, and supination in a PALE seat. The individual and combined effects of the various acceleration protective techniques were examined as they related to various models for acceleration protection, and the data revealed no statistically significant deviations from a simple additive model. The apparent net additivity was interpreted as resulting from a combination of additive, synergistic, and overlapping mechanisms.

Acceleration↗

PubMed1983

External cardiopulmonary resuscitation augmented by the military antishock trousers.

The external pressure suit (MAST) is beneficial in hypovolemic shock by preventing lower extremity venous pooling. Previous data from this laboratory demonstrated that internal cardiac massage is significantly improved when combined with MAST. This study was designed to see if external massage (EM) could be similarly augmented by this device. Twenty anesthetized pigs underwent left thoracotomy and placement of a left atrial catheter for pressure determination and microsphere injection. A flow probe was placed around the aorta for measurement of cardiac output, axillary artery catheters were placed for blood pressure determination and microsphere sampling, and central venous pressure was monitored. Hemodynamic collection of microsphere injections was performed during resting conditions, during EM alone after electrically induced ventricular fibrillation, and during EM after inflation of the MAST suit. Significant increases in mean arterial pressure, systolic arterial pressure, and diastolic pressure were noted with EM and MAST suit inflation over EM alone. Left atrial pressure doubled during EM and MAST suit inflation. Cardiac output was not augmented by the inflation of the MAST. Myocardial blood flow and brain blood flow increased during EM and MAST, but renal blood flow decreased. These data suggest that unlike internal massage, cardiac output during EM and MAST is not improved by increased venous return and flow during EM may be due to a different mechanism than direct cardiac compression.

Animals↗

PubMed1976

[Anti-G-suit-a facility of Neuroanaesthesia at operations in the sitting position].

The Anti-G-Suit- an over-all-air-pressure-garment over legs and bowel up to the xiphoid is proposed as a successful method to encounter acute postural decrease of blood pressure in neurosurgical patients. Increase of peripheral resistance and displacement of the circulating blood volume above the diaphragm enhance blood pressure which has fallen by the depressive effect on the vasomotor centre and the negative inotrope effect of narcotics.

Anesthesia↗

PubMedDate not supplied

[Relation between the probability of development of altitude-decompression disorders and the duration of pre-exposure to a hypobaric atmosphere].

Healthy volunteers, aged 21-47 years, were kept in an altitude chamber. Before decompression to a residual pressure of 293.3 GPa the test subjects were consecutively exposed to 1120 GPa for 2 hrs and then to 733.3 GPa for 24, 18 or 12 hrs. At 293.3 GPa the test subjects performed a moderate workload for 6 hrs. It has been concluded that prior to the use of a space suit with the working pressure 0.3 kgf/cm2 (293.3 GPa) the time of exposure to a hypobaric normoxic (29-30% O2) atmosphere with the total barometric pressure 733.3 GPa should not be less than 18 hrs and it should preferably be 24 hrs. In this situation decompression safety of 6-hr extravehicular activity can be predicted with a high probability.

Adaptation, Physiological↗

PubMed1982

Cardiac performance testing by volume loading and lower-extremity compression.

Cardiac performance was tested with a combination of volume loading and lower-extremity compression by an anti-g suit in 11 patients scheduled for aortic operations. The mean response of cardiac output (CO) to volume loading and anti-g suit compression was flat, despite a significant rise in pulmonary capillary wedge pressure (PCWP). Right to left intrapulmonary shunt was unchanged by the testing procedure. The low mean wedge pressure reemphasizes the need for preoperative insertion of a Swan-Ganz catheter and for measurement of PCWP and Co to provide optimal fluid treatment to each patient who undergoes an aortic reconstructive operation.

Aged↗

PubMed1994

Prevention of venous air embolism in paediatric neurosurgical procedures performed in the sitting position by combined use of MAST suit and PEEP.

We studied 60 children undergoing neurosurgical procedures in the sitting position. Routine monitoring included ECG, pulse oximetry, invasive arterial pressure, in particular mean arterial pressure (MAP), and right atrial pressure (RAP). Children were allocated to two groups. In group B lower body positive pressure and positive end-expiratory pressure (PEEP) were used for preventing venous air embolism (VAE). In this group, antishock trousers (MAST suit) were adjusted in supine children. After induction of anaesthesia, different positions were studied: supine and sitting before MAST suit inflation, sitting with MAST suit inflated up to a pressure of 40 mmHg in the lower compartments and 30 mmHg in the abdominal compartment, and finally a combination of lower body positive pressure and PEEP of 8-10 cm H2O. In group A no MAST suit or PEEP was used. Continuous monitoring of end-tidal carbon dioxide pressure throughout (PE'CO2) was used to detect VAE. In order to evaluate the transmission of pressures from the right atrium to the veins at the base of the skull, jugular bulb venous pressure (JBVP) was measured in 20 patients by retrograde catheterization. The incidence of VAE was compared in the two groups. On placing children into the sitting position, a significant decrease in RAP and JBVP was noted without significant changes in MAP in the two groups. Inflation of the MAST suit induced a dramatic increase in RAP and JBVP, reinforced by addition of PEEP. There was a strong positive relationship between RAP and JBVP. There were no deleterious side effects or differences between the two groups in peroperative blood product requirements or surgical general conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1988

[Influence of the redistribution of liquid volumes on atrial natriuretic factor].

Several studies evidence that volume or pressure increase stimulates atrial natriuretic factor (ANF) secretion by atrial cardiocyte stretch. In order to study the relationship between plasma renin activity (PRA) and ANF plasma level in experimental weightlessness, six healthy male subjects were submitted to antigravity (anti-g) suit inflation which shifts fluid in the thoracic region. Firstly, blood samples were taken at rest after 15 mn in supine position, secondly after 25 mn in upright position with and without anti-g suit. During the tilt test, plasma ANF decreased from 35 +/- 4.1 to 28 +/- 6.6 pg/ml (p less than 0.05) without anti-g suit and rose to 38 +/- 4.1 pg/ml (p less than 0.05) with anti-g suit. This demonstrates the stimulating effect of weightlessness on the ANF release. During the same tilt test PRA increased from 2.69 +/- 0.29 to 4.76 +/- 0.83 ng/ml/h that evidences the perfusion pressure fall on the intrarenal baroreceptors. Anti-g suit inflation abolished this PRA response to the orthostatism, since PRA increase was only 3.23 +/- 0.79 ng/ml/h (p less than 0.05). ACTH and aldosterone levels do not change significantly. These results demonstrate that ANF and PRA which have opposite effects on aldosterone release and Na excretion, change in opposite sens during fluid shifts, to produce antinatriuresis in upright position, or natriuresis in experimental weightlessness.

Adrenocorticotropic Hormone↗

PubMed2002

[New possibilities of the use of space technologies in the treatment of children with injuries of the central nervous system].

The computerized stabilography was used to study the role of the visual analyzer (VA) in vertical posture acquisition and specifics of posture implementation by patients with craniocerebral injury (CCI) wearing suit Adele for dynamic proprioception correction (SDPC). Results of the investigation revealed a decreased vertical stability (VS) of CCI patients and a greater reliance on VA, which may be a compensatory instrument. Following the SDPC course, vertical stability was improved and the VA role in posture acquisition normalized suggesting alteration of the interanalyzer interaction in CCI patients owing to the treatment of proprioception impulsation.

Accidental Falls↗

PubMed1997

Pilot performance of the anti-G straining maneuver: respiratory demands and breathing system effects.

INTRODUCTION: The anti-G straining maneuver (AGSM) is still an important part of pilot protection for G-induced loss of consciousness. The specific requirements for and the effects of breathing systems on the performance of the AGSM are essential elements to designing compatible breathing systems. METHODS: Subject pools of 27 and 34 naval aviators were recruited and used to measure the inhalatory and exhalatory flow requirements for the AGSM and the breathing system effects of mask cavity pressure during AGSM performance on the Naval Air Warfare Center Dynamic Flight Simulator at acceleration levels up to 8 Gz. RESULTS: The mean peak inhalatory flow was 125.5 L.min-1 (n = 135, SD = 42.1) with a maximum value of 274 L.min-1. The mean peak exhalatory flow was 154.4 L.min-1 (n = 135, SD = 49.6) with a maximum value of 308 L.min-1. For the effects of the breathing system on AGSM performance, inhalatory mask cavity pressures were not above 30 mmHg with the majority less than 10 mmHg. Exhalatory mask cavity pressures did not exceed 60 mmHg but predominated in the 20-30 mmHg range. In comparison to accepted guidelines, 67-77% of inhalatory mask cavity pressures were below and 91% of the exhalatory mask cavity pressures were above the Air Standardization and Coordination Committee (ASCC) limit of +/- 14 mmHg. CONCLUSIONS: The difference in the peak inhalatory and exhalatory flows measured during this study and clinically can be attributed to different test conditions and performer techniques. The reduction in inhalatory flow with increasing G is consistent with the increase in breathing difficulty due to the G load and the inflation of the anti-G suit. However, exhalatory mechanics appear unaffected by the G load and the inflation of the anti-G suit. Since 23-33% of the inhalatory mask cavity pressures were above this ASCC limit, improvements in regulator performance are still needed. For exhalatory effects of the breathing system, the main contributor is the mask valve. While no pilot suffered unconsciousness or expressed complaints with the breathing systems used, these exposures were of short duration. The additional work of breathing during a combat engagement may further compromise the pilot's ability to retain consciousness with the AGSM.

Aerospace Medicine↗

PubMed2000

Is MAST in the past? The pros and cons of MAST usage in the field.

Initially, MAST was viewed as a panacea for hypovolemic trauma patients. Through decades of study, this has not panned out. However, MAST seems to stabilize and decrease bleeding in pelvic and long-bone fractures of the lower extremities. It also appears useful in anaphylaxis and in non-traumatic intra-abdominal hemorrhage. The suit has proven deleterious to trauma victims with moderate hypotension (systolic BP 50-90 mm Hg) who face only a short ride to a hospital, especially those with thoracic injuries. Its role in patients with severe hypotension or long prehospital transport times remains unclear. In severely hypotensive patients, the improvement in BP and oxygenation to the heart and brain may override any negative effects of continued hemorrhage. We must wait for further studies to resolve these issues.

Accidents, Traffic↗