Effect of pressure suit inflation on pulmonary capillary blood volume.
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Aerospace Medicine↗
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Influence of pressure suit inflation on pulmonary diffusing capacity in man.
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Cell Respiration↗
Massive hemorrhage in a previously undiagnosed abdominal pregnancy presenting for elective Cesarean delivery.
PURPOSE: To report a case of previously undiagnosed abdominal pregnancy diagnosed at the time of Cesarean section for persistent oblique lie. Delivery of the fetus was followed by near catastrophic hemorrhage. The management of massive hemorrhage in the context of the obstetric patient is discussed. CLINICAL FEATURES: A 32-yr-old, ASA 1 primigravida was scheduled for elective Cesarean delivery at 38 weeks gestation under general anesthesia for a persistent oblique lie. On opening the abdomen, the extra-uterine position of the fetus became obvious. Delivery of the fetus was accompanied by torrential hemorrhage. A portion of the placenta was non-resectable and, following surgery, the patient was sent to the intensive care unit. The patient continued to lose blood and was returned to the operating room soon after. The abdomen was packed with large swabs and the wound left open. The hemorrhage continued and the application of military anti-shock trousers (MAST suit) helped stem the loss. A total of 36 U of red cells, 20 U of fresh frozen plasma, 7 U of platelets and 10 U of cryoprecipitate were transfused perioperatively. Both the baby and the mother survived. CONCLUSION: Massive hemorrhage in obstetric patients is a major test for the anesthetic and obstetric teams. As our experience shows, a multidisciplinary team based approach helped manage this crisis. Obstetric patients are often young and have great physiological reserve. In this case we feel that the MAST suit significantly contributed to the positive outcome.
Adult↗
Bee-sting anaphylaxis: the use of medical antishock trousers.
There is a large population of unprotected individuals who are susceptible to Hymenoptera-induced anaphylaxis. Medical antishock trousers (the MAST suit) can play an important role in field treatment of anaphylactic shock. Upon application, both blood pressure and cerebral perfusion are preserved despite clinically profound vasodilation. The MAST suit mechanically increases peripheral resistance, analogous to the vasoconstrictive effects of adrenaline. In the two cases presented, the MAST suit reversed significant hypotension caused by Hymenoptera envenomation. Both patients recovered fully. Based on the suit's effectiveness in bee-sting anaphylaxis, it would seem that extended indications exist for using the MAST suit in other forms of low-resistance shock.
Adolescent↗
Clinical use of the "G-suit".
The "G-suit," a device for combating hypovolemic shock with external pneumatic counterpressure, represents an application of an old idea to a relatively common medical problem. Its simplicity of use and quick therapeutic effect buys time for the patient with hypovolemic shock, whether the suit is applied in the prehospital or emergency department setting.
Emergency Medical Services↗
Influence of G-suit abdominal bladder inflation on gas exchange during +GZ stress.
Available data relating duration of +GZ stress to blood gas exchange status is limited. Furthermore, studies focusing on pulmonary gas exchange during +GZ stress when abdominal restriction is imposed have yielded conflicting results. To examine the time course of blood gas changes occurring during exposure to +GZ stress in dogs and the influence of G-suit abdominal bladder inflation on this time course, seven spontaneously breathing pentobarbital-anesthetized adult mongrel dogs were exposed to 60 s of up to +5 GZ stress with and without G-suit abdominal bladder inflation. Arterial and mixed venous blood were sampled for blood gas analysis during the first and last 20 s of the exposure and at 3 min postexposure. Little change in blood gas status was seen at +3 GZ regardless of G-suit status. However, with G-suit inflation, arterial PO2 fell by a mean of 14.7 Torr during the first 20 s at +4 Gz (P less than 0.01, t test) and 20.6 Torr at +5 GZ (P less than 0.01). It continued to fall an additional 10 Torr during the next 40 s at both +4 and +5 GZ. Arterial PO2 was still 5-10 Torr below control values (P less than 0.05) 3 min postexposure. A second series of experiments paralleling the first focused on blood gas status during repeated exposure to acceleration. Blood gas status was assessed in five dogs during the late 20 s of two 60-s exposures separated by 3 min at 0 GZ. No significant differences between the initial and repeated exposures were detected. The data indicate that G-suit abdominal bladder inflation promotes increased venous admixture.
Acceleration↗
Accommodation of females in the high-G environment: the USAF Female Acceleration Tolerance Enhancement (FATE) Project.
BACKGROUND: In 1993, the U.S. Secretary of Defense opened combat aircraft assignments to women. To verify the adequacy of acceleration (+Gz) protection for female high-G aircrew, USAF investigators conducted fit tests of standard and developmental G-protective equipment and determined the effectiveness of a unique laboratory modification (AL Mod) of the standard (CSU-13B/P) anti-G suit during gender-comparative centrifuge evaluations. METHODS: Investigators determined relaxed +Gz tolerance and straining endurance to +4.5 to +7 Gz and +5 to +9 Gz simulated aerial combat maneuver (SACM) centrifuge profiles (4.5-7 SACM: 8 females and 10 males; and 5-9 SACM: 6 females and 8 males, respectively). Additionally, in the 5-9 SACM study, between and within gender SACM endurance differences were assessed before and after female subjects' use of the AL Mod. Ten female subjects also were fit tested in extended coverage, developmental G-protective equipment. RESULTS: There was no gender difference in 4.5-7 SACM endurance. Male 5-9 SACM endurance exceeded that of females in the unmodified CSU-13B/P (p < 0.05), but gender parity was achieved when females wore the AL Mod. Fit modifications of developmental G-protective equipment were not required, but smaller sizes of the standard CSU-13B/P and a developmental anti-G suit were indicated and developed. CONCLUSION: In properly fitted anti-G suits, gender parity in SACM endurance is achievable; however, full accommodation of female aircrew in the high-G environment will require the AL Mod and/or smaller sized anti-G suits.
Acceleration↗
External counterpressure and the MAST suit: current and future roles.
External counterpressure devices, such as the MAST suit, may be lifesaving not only in acute hypovolemia secondary to abdominal, pelvic and lower extremity trauma, but in a number of other shock states as well. Expanded use of the MAST suit may well include not only supra-diaphragmatic injuries, but diverrse entities such as pericardial tamponade, tension pneumothorax, and leaking aortic aneurysm, and as an adjunct to cardiopulmonary resuscitation. The limited adverse effects of the MAST suit, in conjunction with its rapidly favorable and rapidly reversible hemodynamic effect, make it an important tool not only in prehospital care and in the emergency department, but in a wide variety of hospital circumstances. For this reason emergency physicians must not only be aware of uses of the MAST suit themselves, but should be prepared to disseminate this information to the general medical community.
Aortic Rupture↗
[Antigravity suit used for neurosurgical operations in sitting position].
The aviator's antigravity suit (G-suit) was used for 40 operations on neurosurgical patients operated on in sitting position. The G-suit was filled with air to 0.2 atmosphere (20 kPa) pressure in 26 cases, and 0.3 atm. (30 kPa) in 14 cases. In all cases G-suit filling was followed by central venous pressure rise and mean arterial pressure rise. Venous air embolism was found in 5 (12.5%) patients. No other complications connected with the use of G-suit were observed.
Adolescent↗
The antigravity suit (G-suit) in surgery; control of blood pressure in the sitting position and in hypotensive anesthesia.
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Anesthesia↗
Respiratory function following application of MAST trousers.
To determine whether counterpressure suits such as the medical anti-shock trousers (MAST) reduce functional ventilation, 25 consecutive patients who received MAST support were reviewed retrospectively. The indications for use of MAST were systolic pressure below 80 mm Hg or clinical signs and pressure below 100 mm Hg. In the five patients with head injuries severe acidosis developed, with a mean pH of 7.19. The other groups had only mild acidosis. Although counterpressure suits have been shown to affect mechanical pulmonary function, alveolar ventilation is not significantly impaired.
Craniocerebral Trauma↗
Hemodynamics of miniature swine during +Gz stress with and without anti-G support.
Nine unanesthetized, chronically instrumented, female miniature swine (MS) (avg wt, 39.7 kg) were exposed to head-to-tail inertial load (+Gz) levels of +3, +5, and +7 Gz for 60 s, with and without anti-G-suit inflation. Venous flow (VF) was measured by an electromagnetic flow sensor around the inferior thoracic vena cava at the diaphragm. Central venous pressure (CVP), abdominal venous pressure (AVP), eye-level blood pressure (ELBP), and esophageal pressure (EP) were also measured before, during, and after +Gz. There was a progressive significant decrease from control of both ELBP (P less than 0.001) and VF (P less than 0.05) during the three +Gz exposures, both with and without G-suit inflation. Without G-suit inflation, most of the MS were unable to tolerate +5 and +7 Gz. Although VF was significantly (P less than 0.02) improved by G-suit inflation during +Gz there was no significant difference in VF between the three +Gz levels, with or without G-suit inflation. The MS does a spontaneous straining maneuver (cyclic Valsalva) during +Gz with G-suit support. Using EP as a trigger, the data were grouped as strain or no strain (relaxation). A continuous AVP-to-CVP gradient existed during G-suit inflation, which increased dramatically during no strain with increasing +Gz, and was associated with an increase in VF. Thus, the majority of VF occurred during relaxation between strains, even though relaxation time was shortened as +Gz increased. Although ELBP is obviously dependent on cardiac output and venous return, the progressive reduction in ELBP with increased +Gz loads was not significantly related to changes in VF at the diaphragm which was maintained, although at a reduced rate, by the AVP-to-CVP gradient during G-suit inflation.
Acceleration↗
ICP changes following application of the MAST suit.
The MAST suit is used primarily in the field to raise arterial pressure in patients with hemorrhagic shock. By 'squeezing' blood back to the heart and compressing arteries, the suit acts to transfuse the patient as well as to compress bleeding sites. Because of the sudden increase in venous return with abdominal compression, its use has been questioned after closed head injury, cardiac tamponade, and/or tension pneumothorax. A study was devised to evaluate the MAST suit in dogs following hemorrhage and hemorrhage with the creation of a tension pneumothorax, cardiac tamponade, and mass intracranial lesion. Pulmonary artery, central venous, systemic arterial, and intracranial pressures were monitored in control dogs before and after hemorrhage and application of the MAST suit. Following hemorrhage, the inflated MAST suit raised systolic arterial pressure as well as central venous, pulmonary artery, and intracranial pressures. The rise in intracranial pressure mirrored the rise in venous pressure and never reached potentially harmful levels in the hemorrhaged animals and animals with a mass intracranial lesion. In the animals with cardiac tamponade and tension pneumothorax, inflation of the abdominal portion of the MAST suit produced a marked rise in central venous and intracranial pressures. This was altered by either relieving the lesion or reducing the pressure of the abdominal portion of the MAST suit.
Animals↗
[Hypobaric nitrogen-oxygen atmosphere as a method of preventing altitude decompression sickness].
It has been shown experimentally that the development of altitude decompression disease at 250 and 180 mm Hg can be prevented by preliminary desaturation in the nitrogen-oxygen hypobaric atmosphere (60% N2 and 40% O2 at 550 mm Hg). This has been demonstrated in 38 experiments on 21 test subjects. The use of this atmosphere in space cabin prevents the development of decompression disease upon a decrease of the cabin pressure to 250 mm Hg and upon extravehicular activity in a space suit with 180--200 mm Hg.
Adult↗
Extended-coverage-bladder G-suits can provide improved G-tolerance and high Gz foot pain.
METHOD: An extended coverage bladder (ECB) G-suit was evaluated on the DCIEM centrifuge against the current service G-suit (CSU-15/P) in two separate series of experiments. The ECB G-suit covered approximately 85% of the lower body measuring from the umbilicus and all five bladders completely encircled each leg and the lower trunk. The CSU-15/P G-suit covered approximately 30% of the lower body and its five bladders were located only over the frontal aspect of each leg and the lower trunk. The first series of experiments involved five subjects from the highly experienced DCIEM A-team. A standard gradual onset rate (GOR) run was used and suit testing order was counterbalanced across subjects. RESULTS: The test condition G-tolerances are listed as mean +/- SEM; relaxed uninflated tolerances were 4.0 +/- 0.14 for the CSU-15/P suit vs. 4.1 +/- 0.09 for the ECB suit (ns, single tailed, paired t-test) while relaxed inflated tolerances were 4.7 +/- 0.19 for the CSU-15/P suit and 5.5 +/- 0.37 for the ECB suit (p = 0.02, single tailed, paired t-test). The straining tolerances were 8.1 +/- 0.44 for the CSU-15/P suit and 9.0 +/- 0.56 for the ECB suit (p = 0.01, single tailed, paired t-test). The second series involved nine subjects for the following three G-suit conditions; CSU-15/P, ECB with inflation limiters, and ECB with inflation limiters and foot bladders. Relaxed uninflated tolerances were 4.0 +/- 0.13, 4.0 +/- 0.08, and 3.9 +/- 0.10 (ns) while straining inflated tolerances were 9.4 +/- 0.48, 10.1 +/- 0.38 and 10.6 +/- 0.42, respectively (p = 0.01 between all three straining conditions, ANOVA with Scheffé F-test). The ECB G-suit with inflation limiters eliminated abdominal pain and discomfort. CONCLUSION: The ECB G-suit provides improved G-tolerance for both inflated relaxed and straining exposures. Foot bladders eliminated high Gz foot pain and improved straining G-tolerance by about half a Gz. The efficacy of ECB G-suits should be evaluated when used in conjunction with positive pressure breathing. While the ultimate G-suit has yet to be conceived and will no doubt be part of an integrated life support system, ECB G-suits are a step in the right direction in the evolution of life support garmentry.
Abdominal Pain↗
Conservative treatment using compression suits for second and third degree burns in children.
The use of compression suits since December 1976 has shown, that even in cases with hypertrophic scarring after deep second- and third-degree burns good late results can be obtained. Thirty-five patients were re-examined 18 to 20 months after the compression suits were introduced and the results were analysed.
Acute Disease↗
Cardiovascular effects of varying G-suit pressure and coverage during +1 Gz positive pressure breathing.
With the continued evolution of anti-G suits, used to counter the cardiovascular dysfunction arising from +1 Gz hypoxia protection positive pressure breathing (PPB), it was hypothesized that full-coverage anti-G-suits would offer equal protection while using lower inflation pressures than the traditional 4:1 ratio. Nine experienced subjects were exposed to 2 min of 70 mm Hg PPB while wearing either the COMBAT EDGE (CE) and Tactical Life Support System (TLSS) garments with the G-suit inflated to 4 x breathing pressure, and the Advanced Tactical Anti-G-Suit (ATAGS) at 4, 3, 2, and 1 x the breathing pressure. All subjects were measured with impedance cardiography (IC), and six were measured simultaneously with both IC and the Cardioscint nuclear probe. IC-estimated stroke volume, relative left ventricular (LV) end-diastolic volume, LV ejection fraction, and peak filling rate were depressed most in the CE and ATAGS 1 conditions (p < 0.001). Heart rate and mean arterial blood pressure changes were highest and lowest, respectively, using the CE and ATAGS 1 garments (p < 0.001). There were no differences in these variables between the TLSS and ATAGS 2-4 conditions. Thus, protection against the PPB-induced fall in LV preload and cardiovascular function may still be adequately afforded by lower G-suit inflation pressures when using full-coverage anti-G suits during PPB intended for high altitude-protection.
Blood Pressure↗
[Human calorimetry in sealed hermetic enclosures].
The paper gives the results of an experimental assessment of personal biocalorimeter and calorimetric garment. The paper is addressed to biologists, physiologists and physicians investigating heat exchange and thermal regulation of the human body as well as to thephysicists developing calorimetric theories and methods. It presents theoretical concepts underlying direct calorimetry of a suited man and contains a block-diagram of the biocalorimeter that was used to examine energy parameters of the human body, including metabolic rate, heat production, heat release and heat balance. The data obtained were statistically treated and heat effects were characterized by empiric expressions. It was for the first time in medical practice that the personal calorimeter and calorimetric garment made it possible to accumulate information on the thermal state of the human body. This information helps to diagnose the health condition of man, to standardise environmental parameters in aviation, space and such like suits and to automatize their maintenance in experimental and real life situations.
Body Temperature Regulation↗