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PubMed1993

Prehospital care.

To improve patient outcome and reduce time at the scene, treatment protocols for specific injuries and rapid transport should be established with individual systems. These standards should be based on such parameters as history, mechanism of injury, physiologic status of the patient on arrival, triage criteria, and predicted transport times. Ensuring airway patency and stability is a vital function that must be rapidly and carefully performed. Any patient at risk for neck or back trauma needs to be immobilized quickly using a rigid cervical collar with head immobilizer and long backboard. Initiation of IV fluids is acceptable if this skill can be accomplished within several minutes and does not significantly postpone transport. When prolonged or delayed transport times are encountered, aeromedical evacuation should be considered. Medical direction by a qualified physician with an interest in prehospital care and emergency medical services is an essential component in any successful system. The medical director should be strategically involved with protocol development, training and continuing education, and continuous quality improvement. Intensive supervised training in trauma management for EMTs and paramedics will help to reduce the amount of time spent at the scene of an accident. Emergency medical services have certainly come a long way over the past century. Indeed, more research is necessary in order to confirm, perfect, or dispute the many traditional theories that have been a part of prehospital technology. As the field of emergency medicine continues to develop and expand, so too will the specialty of prehospital medicine. Napoleon would be proud!

Aircraft↗
PubMed1993

[Prevention of thrombosis in surgery of the extremities. Physical methods in thrombosis prevention].

Physical therapy procedures for the prophylaxis of thrombosis are part of basic medical therapy. Their effect has been documented by numerous individual observations, even though no prospective studies are available. Since the inconvenience to the patient is minor, they should be implemented in all surgical patients. In the case of patients at risk of thrombosis such as in orthopedic surgery, the effect of such procedures is not sufficient. In this case physical therapy procedures can only supplement the medical prophylaxis of thrombosis. The effectiveness of technically more complex physical procedures has been documented in small studies, but due to the high technical and personnel costs, the application is restricted.

Bandages↗
PubMedDate not supplied

Thromboembolic prophylaxis in moderate-risk patients undergoing elective abdominal surgery: decision and cost-effectiveness analyses.

We conducted a retrospective, literature-based decision analysis to compare the cost-effectiveness of conventional low-dose heparin, dalteparin, and intermittent pneumatic compression (IPC) as thromboembolic prophylaxis to a no-prophylaxis option in patients at moderate risk of developing thromboembolic complications after major elective abdominal surgery. The analysis was conducted through an institutional perspective. Probability and incidence rate data were summarized from the literature. Cost data were obtained from the Detroit Medical Center's cost accounting systems and from national diagnosis-related group estimates. Mortality and complications avoided were the main outcome measures on which cost-effectiveness was based. Overall costs associated with conventional low-dose heparin, dalteparin, intermittent pneumatic compression, and no prophylaxis were $84, $122, $102, and $112, respectively in the primary analysis, which included costs of labor. Corresponding cost-effectiveness ratios in terms of costs/complication-free patient were $86, $124, $103, and $118, respectively. Compared with no prophylaxis, incremental cost-effectiveness analysis in terms of cost/mortality avoided involved savings of $6087 and $3125 with conventional low-dose heparin and IPC, respectively, and expenses of $2857 with dalteparin. A secondary analysis excluding costs of labor showed similar results. The results of the study consistently showed conventional low-dose heparin to provide the most cost-effective thromboembolic prophylaxis of the methods considered in terms of reducing both morbidity and mortality in the patient population studied.

Cost-Benefit Analysis↗
PubMed1996

Pneumatic compression or aspirin prophylaxis against thromboembolism in total hip arthroplasty.

We prospectively studied the use of either aspirin or intermittent pneumatic compression (IPC) as prophylaxis against thromboembolism after 330 consecutive total hip arthroplasties. Duplex ultrasonography of the veins of both lower extremities and ventilation-perfusion lung scans were done preoperatively and 7 to 14 days postoperatively. Eight patients in the IPC group (5%) had asymptomatic deep vein thrombosis; there were no symptomatic thrombi. In the aspirin group, 10 patients (7%) had asymptomatic deep vein thrombosis and two patients (1%) had symptomatic deep vein thrombosis. This difference was not statistically significant. There were no fatal pulmonary emboli in either group. In the IPC group, only one patient had symptomatic pulmonary embolism and 20 patients (22 hips [12%]) had asymptomatic pulmonary embolism. In the aspirin group, two patients (1%) had symptomatic pulmonary embolism and 26 patients (18%) had asymptomatic pulmonary embolism. This difference in asymptomatic pulmonary embolism between the two groups was statistically significant. Both groups had a low incidence of deep vein thrombosis, as shown by Duplex ultrasonography, but IPC was more effective than aspirin in preventing asymptomatic pulmonary embolism after total hip arthroplasty.

Adult↗
PubMed1997

Arm arterial occlusion cuffs as a means of alleviating high +Gz-associated arm pain.

In an aircraft used under sustained high +Gz conditions, if the stick and throttle are positioned such that the pilot's hands are 20 cm or more below heart level, the consequent rise in forearm venous pressure (FVP) may give rise to arm pain, which is exacerbated by positive pressure breathing for G protection (PBG). This study examined the use of arm arterial occlusion cuffs (AAOC) as a means of pain alleviation. Six subjects were exposed on a human centrifuge to a simple acceleration profile of +7 Gz for 15 s, (onset rate 1 G.s-1), and to a complex profile of +4.8 Gz for 10 s followed by +7 Gz for 10 s, repeated 3 times. Subjects wore full coverage anti-G trousers, used PBG (+2 Gz out-in and 10 mm Hg/G), and performed runs with and without inflation of AAOC, during which invasive measurement of FVP was made. During the simple acceleration profile without AAOC, FVP rose to a mean peak of 209 mm Hg and arm pain was severe. With inflation of the AAOC, FVP rise was curtailed at a mean peak of 158 mm Hg and pain was absent. However, during sequential +7 Gz plateaus of the complex profile, AAOC inflation was associated with serially increasing FVP, which was significantly higher than that without AAOC inflation (p < 0.05 and p < 0.001 for second and third plateaus, respectively), giving rise to immediate and severe arm pain. Therefore, the use of arm arterial occlusion as a means of alleviating arm pain is unsuccessful.

Acceleration↗
PubMed1998

Improved anti-G protection boosts sortie generation ability.

BACKGROUND: There is a need for evaluation of new G protection equipment. HYPOTHESIS: There is no difference between the two anti-G ensembles on affecting subjects' ability to tolerate multiple simulated aerial combat sorties. METHODS: There were 15 subjects wearing the standard CSU-13 B/P anti-G ensemble (STD) or COMBAT EDGE/ATAGS (CE/ATAGS) ensemble who were exposed to 3 centrifuge-based simulated air combat sorties during a 2-h period. Each sortie consisted of four different G-profiles: 1) a gradual onset profile; 2) simulated air combat maneuver consisting of +4.5 to +7 Gz plateaus (4.5-7 SACM); 3) simulated air combat maneuver derived from actual fighter maneuvers with peaks up to +9 Gz (TACM); 4) simulated air combat maneuver consisting of +5.0 to +9.0 Gz plateaus (5-9 SACM). Each sortie was separated by a 20-min rest period. We measured heart rate, peripheral light loss (PLL), subjective effort level, subjective fatigue level, and reported recovery time. RESULTS: There were no incidents of unintended G-induced loss of consciousness (G-LOC) with CE/ATAGS. There were four incidents of unintended G-LOC with STD. At the end of the third sortie, with CE/ATAGS, mean heart rate was lower during the 4.5-7 SACM (p < 0.001) and the TACM (p < 0.001); PLL was less during all three rapid onset profiles (p < 0.01); subjects reported less effort during the 4.5-7 SACM (p < 0.001), the TACM and the 5-9 SACM (p < 0.01); reported fatigue was significantly lower (p < 0.001); and reported recovery times were nearly halved (p < 0.01). CONCLUSION: CE/ATAGS provided significantly greater G-protection than the standard anti-G ensemble. There was no G-LOC with CE/ATAGS. This greater protection should be of significant operational value in enhancing sortie generation capability by increasing fighter aircrew G-tolerance and decreasing aircrew fatigue.

Adult↗
PubMed1998

Female exposure to high G: performance of simulated flight after 24 hours of sleep deprivation.

BACKGROUND: Ground-based research has investigated the loss of cognitive function in the extreme conditions of G-induced loss of consciousness, however, little is known about pilots' abilities to maintain cognitive performance throughout prolonged conscious exposure in the high-G environment. The effects of fatigue and G layoff on performance during exposure to high G are mostly unknown for the female population. METHODS: This research was conducted on the centrifuge Dynamic Environment Simulator. Active-duty personnel (8 male and 8 female) were trained to fly the F-16 simulation while 30 performance measures were recorded. Performance was re-evaluated after 24 h of sleep deprivation. RESULTS: Neither male nor female overall performance was affected significantly by sleep status, although individual tasks showed sensitivity; call-sign reaction time was longer by 33%, and missile survival was less likely. Also, when sleep deprived, perceived effort and physical demand were higher while perceived performance was lower. No differences in performance were found in either gender due to lay-off, although some physiologic deconditioning was apparent. Women commanded and endured the same amount of G load as men, however, on average they could not perform the tracking task quite as well. CONCLUSIONS: Sleep deprivation (24 h) produced sensations of fatigue and frustration, but overall performance was not reduced. The ability of personnel to complete a complex defensive maneuver was reduced when they were sleep deprived. The women that we tested apparently could not optimize the tracking task as well as their male counterparts when Gz was in the simulation. None of these results were sufficient to suggest that women should not be allowed to compete for flying assignments in high-performance aircraft.

Aerospace Medicine↗
PubMed1998

Meta-analysis of effectiveness of intermittent pneumatic compression devices with a comparison of thigh-high to knee-high sleeves.

This meta-analysis used all original articles from 1966 to June 1996 that fit the preset inclusion criteria to examine the clinical effectiveness of intermittent pneumatic compression (IPC) devices in preventing deep vein thrombosis (DVT) and pulmonary embolism and to compare the results of knee-high sleeves to thigh-high sleeves. IPC devices decreased the relative risk of DVT by 62 per cent when compared with placebo, 47 per cent compared with graduated compression stockings, and 48 per cent compared with mini-dose heparin. IPC devices significantly decreased the relative risk of DVT compared with placebo in high-risk patients such as neurosurgery and major orthopedic surgery patients and in modest risk patients such as general surgery patients. In major orthopedic surgery patients, the incidence of DVT was similar for IPC- and warfarin-treated patients; however, IPC was significantly better than warfarin at decreasing the incidence of calf only DVT, whereas warfarin seemed to be better at decreasing proximal DVT. IPC devices are effective in decreasing the incidence of DVT in patients at moderate to high risk and are probably more efficacious than graduated compression stockings or mini-dose heparin; however, IPC devices are not protective against pulmonary embolism. The data directly comparing the various methods of compression (knee-high versus thigh-high sleeves and graded-sequential versus uniform compression) are sparse and conflicting.

Bandages↗
PubMed1998

Venoconstrictive thigh cuffs impede fluid shifts during simulated microgravity.

BACKGROUND: This study determined the efficacy of venoconstrictive thigh cuffs, inflated to 50 mmHg, on impeding fluid redistributions during simulated microgravity. METHODS: There were 10 healthy male subjects who were exposed to a 2-h tilt protocol which started in the standing position, and was followed by 30 min supine, 30 min standing, 30 min supine, 30 min of -12 degrees head down tilt (HDT, to simulate microgravity), 15 min of HDT with venoconstrictive thigh cuffs inflated, a further 10 min of HDT, 5 min supine, and 10 min standing. To increase the sensitivity of the techniques in an Earth-based model, 12 degrees HDT was used to simulate microgravity effects on body fluid shifts. Volume changes were measured with anthropometric sleeve plethysmography. RESULTS: Transition to the various tilt positions resulted in concomitant decrements in leg volume (Stand [STD] to Supine [SUP], -3.0%; SUP to HDT, -2.0%). Inflation of the venoconstrictive thigh cuffs to 50 mmHg, during simulated microgravity, resulted in a significant 3.0% increase in leg volume from that seen in HDT (p < 0.01). No significant changes in systemic cardiovascular parameters were noted during cuff inflation. CONCLUSIONS: We conclude that venoconstrictive thigh cuffs, inflated to 50 mmHg for 15 min during 12 degrees HDT, can create a more Earth-like fluid distribution. Cuffs could potentially be used to ameliorate the symptoms of cephalad edema seen with space adaptation syndrome and to potentiate existing fluid volume countermeasure protocols.

Adult↗
PubMed1998

The effect of a pressure garment on post-surgical drainage and seroma formation in breast cancer patients.

BACKGROUND: The treatment of choice for cancer of the breast are mastectomy and axillary clearance or wide excision with axillary clearance. The most common complication following such a procedure is seroma formation. Various methods have been used to prevent it. However, the use of a pressure garment in this context has not been fully evaluated in the current literature. RESULTS: In a randomised trial comparing patients with a pressure garment with those without one, we have found no improvement in post-operative drainage with the use of a pressure garment. There were more complications in the group without the pressure garment (19%) compared with those with the garment (15.7%). The only seroma occurred in those patients not using the garment. The use of the pressure garment appeared to increase the duration of use of the drain (6.8 vs 6.1 days), these differences in the two groups was not significant. One of the patients in the pressure garment group was unable to tolerate the warmth and discontinued wearing the garment in the third post-operative day. This gave a rejection rate of 5%. CONCLUSION: The use of a pressure garment does not reduce the post-operative drainage, however, the complication rate appears to be higher when the pressure garment is not being used.

Breast Neoplasms↗
PubMed2005

Effects of gravity and blood volume shifts on cardiogenic oscillations in respired gas.

During the cardiac cycle, cardiogenic oscillations of expired gas (x) concentrations (COS([x])) are generated. At the same time, there are heart-synchronous cardiogenic oscillations of airway flow (COS(flow)), where inflow occurs during systole. We hypothesized that both phenomena, although primarily generated by the heartbeat, would react differently to the cephalad blood shift caused by inflation of an anti-gravity (anti-G) suit and to changes in gravity. Twelve seated subjects performed a rebreathing-breath-holding-expiration maneuver with a gas mixture containing O2 and He at normal (1 G) and moderately increased gravity (2 G); an anti-G suit was inflated to 85 mmHg in each condition. When the anti-G suit was inflated, COS(flow) amplitude increased (P = 0.0028) at 1 G to 186% of the control value without inflation (1-G control) and at 2 G to 203% of the control value without inflation (2-G control). In contrast, the amplitude of COS of the concentration of the blood-soluble gas O2 (COS([O2/He])), an index of the differences in pulmonary perfusion between lung units, declined to 75% of the 1-G control value and to 74% of the 2-G control value (P = 0.0030). There were no significant changes in COS(flow) or COS([O2/He]) amplitudes with gravity. We conclude that the heart-synchronous mechanical agitation of the lungs, as expressed by COS(flow), is highly dependent on peripheral-to-central blood shifts. In contrast, COS([blood-soluble gas]) appears relatively independent of this mechanical agitation and seems to be determined mainly by differences in intrapulmonary perfusion.

Adaptation, Physiological↗
PubMed2002

Inter- and intraregional ventilation inhomogeneity in hypergravity and after pressurization of an anti-G suit.

This study assessed the effects of increased gravity in the head-to-foot direction (+G(z)) and anti-G suit (AGS) pressurization on functional residual capacity (FRC), the volume of trapped gas (V(TG)), and ventilation distribution by using inert- gas washout. Normalized phase III slope (Sn(III)) analysis was used to determine the effects on inter- and intraregional ventilation inhomogeneity. Twelve men performed multiple-breath washouts of SF(6) and He in a human centrifuge at +1 to +3 G(z) wearing an AGS pressurized to 0, 6, or 12 kPa. Hypergravity produced moderately increased FRC, V(TG), and overall and inter- and intraregional inhomogeneities. In normogravity, AGS pressurization resulted in reduced FRC and increased V(TG), overall, and inter- and intraregional inhomogeneities. Inflation of the AGS to 12 kPa at +3 G(z) reduced FRC markedly and caused marked gas trapping and intraregional inhomogeneity, whereas interregional inhomogeneity decreased. In conclusion, increased +G(z) impairs ventilation distribution not only between widely separated lung regions, but also within small lung units. Pressurizing an AGS in hypergravity causes extensive gas trapping accompanied by reduced interregional inhomogeneity and, apparently, results in greater intraregional inhomogeneity.

Adult↗
PubMed2002

Work and fatigue characteristics of unsuited and suited humans during isolated isokinetic joint motions.

The effects of a pressurized suit on human performance were investigated. The suit is known as an Extra-Vehicular Mobility Unit (EMU) and is worn by astronauts while working outside their spacecraft in a low earth orbit. Isolated isokinetic joint torques of three female and three male subjects (all experienced users of the suit in 1G gravity) were measured while working at 100% and 80% of their maximum voluntary torque (MVT, which is synonymous with maximum voluntary contraction (MVC)). It was found that the average decrease in the total amount of work (the sum of the work in each repetition until fatigue) done when the subjects were wearing the EMU were 48% and 41% while working at 100% and 80% MVT, respectively. There is a clear relationship between the MVT and the time and amount of work done until fatigue. Here, the time to fatigue is defined as the ending time of the repetition for which the computed work done during that repetition dropped below 50% of the work done during the first repetition. In general the stronger joints took longer to fatigue and did more work than the weaker joints. It was found that the EMU decreases the work output at the wrist and shoulder joints the most, due to the EMU joint geometry. The EMU also decreased the joint range of motion. The average total amount of work done by the test subjects increased by 5.2% (20.4%) for the unsuited (suited) case, when the test subjects decreased the level of effort from 100% to 80% MVT. Also, the average time to fatigue increased by 9.2% (25.6%) for the unsuited (suited) case, when the test subjects decreased the level of effort from 100% to 80% MVT. It was also found that the experimentally measured torque decay could be predicted by a logarithmic equation. The absolute average errors in the predictions were found to be 18.3% and 18.9% for the unsuited and suited subjects, respectively, when working at 100% MVT, and 22.5% and 18.8% for the unsuited and suited subjects, respectively, when working at 80% MVT. These results could be very useful in the design of future EMU suits and the planning of Extra-Vehicular Activity (EVA) for the future International Space Station assembly operations.

Female↗
PubMed2002

Mechanisms of microgravity induced orthostatic intolerance: implications for effective countermeasures.

The development of orthostatic hypotension and instability immediately after return from spaceflight has been a significant operational problem to astronauts for more than four decades. Significant reductions in stroke volume and peripheral vascular resistance contribute to ineffective maintenance of systemic arterial blood pressure during standing after spaceflight despite compensatory elevations in heart rate. The primary mechanism underlying reduced stroke volume appears to be a reduction in preload associated with reduced circulating blood volume, although cardiac atrophy might also contribute. Space flight and ground based experiments have demonstrated that an inability to provide adequate peripheral vasoconstriction in astronauts that become presyncopal may be associated with several mechanisms including reduced sympathetic nerve activity, arterial smooth muscle atrophy and/or hyporeactivity, hypersensitivity of beta-adrenergic receptors, etc. In addition, an inability to provide adequate tachycardia in presyncopal subjects may be associated with reduced carotid-cardiac baroreflex sensitivity. Based on the current knowledge and understanding of cardiovascular mechanisms that are altered during exposure to microgravity, a major focus of future research should be directed to the systematic evaluation of potential countermeasures that specifically target and restore the function of these mechanisms. Based on a preliminary systematic evaluation presented in this review, acute physical exercise designed to elicit maximal effort, G-suit inflation, artificial gravity, and specific pharmacological interventions, alone or in combination, have shown promise as successful countermeasures that provide protection against post-flight orthostatic intolerance.

Aerospace Medicine↗