Medical Antishock Trousers Research Articles

The Effect of Short-Term Exposure to Lower Body Positive Pressure on Motor Signal Processing, Reaction Times, and Cardiovascular Parameters in Healthy Volunteers Using Medical Anti-shock Trousers.

Microgravity, as experienced during spaceflight has notable effects on the cognition and cardiovascular systems. However, its effect on motor signal processing is not known. Inthis study, we planned to study the effect of microgravity simulation with a lower body positive pressure of 50 mmHg on motor signal processing, reaction times, and cardiovascular parameters. Thirty healthy human volunteers participated in this investigation, and continuous ECG and non-invasive blood pressure were measured at baseline, during, and after a lower body positive pressure of 50 mmHg.Bereitschafts potential was recorded at 0 mmHg and 50 mmHg pressure values in a lower body positive pressure (LBPP) suit.Parameters recorded during the pressure change of 0 mmHg to 50 mmHg were RR interval, heart rate, systolic blood pressure, diastolic blood pressure, stroke volume, cardiac output, and peripheral vascular resistance. Heart rate variability (HRV) was calculated from RR intervals during resting and pressure of 50mmof Hg.We also compared simple and choice reaction times for visual and auditory stimuli during 50 mmHg LBPP exposure with baseline recording. We found a significant increase in systolic blood pressure, stroke volume, and cardiac output from baseline at 50 mmHg of LBPP. We found a significant change in amplitude and area of Bereitschaft potential at the C4 site at 50 mmHg of LBPP. We found a significant change in low-frequency power (LF)as compared to the baseline in HRV. Simple reaction time (visual & auditory) and auditory choice reaction time were improved at 50 mmHg of LBPP. Motor signal processing and reaction time were improved during 50 mmHg of lower body positive pressure exposure.

The hydrostatic pressure indifference point underestimates orthostatic redistribution of blood in humans

The hydrostatic indifference point (HIP; where venous pressure is unaffected by posture) is located at the level of the diaphragm and is believed to indicate the orthostatic redistribution of blood, but it remains unknown whether HIP coincides with the indifference point for blood volume (VIP). During graded (± 20°) head-up (HUT) and head-down tilt (HDT) in 12 male volunteers, we determined HIP from central venous pressure and VIP from redistribution of both blood, using ultrasound imaging of the inferior caval vein (VIPui), and fluid volume, by regional electrical admittance (VIPadm). Furthermore, we evaluated whether inflation of medical antishock trousers (to 70 mmHg) affected HIP and VIP. Leaving cardiovascular variables unaffected by tilt, HIP was located 7 ± 4 cm (mean ± SD) below the 4th intercostal space (IC-4) during HUT and was similar (7 ± 3 cm) during HDT and higher (P < 0.0001) than both VIPui (HUT: 22 ± 16 cm; HDT: 13 ± 7 cm) and VIPadm (HUT: 29 ± 9 cm; HDT: 20 ± 9 cm below IC-4). During HUT antishock trousers elevated both HIP and VIPui [to 3 ± 5 cm (P = 0.028) and 17 ± 7 cm below IC-4 (P = 0.051), respectively], while VIPadm remained unaffected. By simultaneous recording of pressure and filling of the inferior caval vein as well as fluid distribution, we found HIP located corresponding to the diaphragm while VIP was placed low in the abdomen, and that medical antishock trousers elevated both HIP and VIP. The low indifference point for volume shows that the gravitational influence on distribution of blood is more profound than indicated by the indifference point for venous pressure.

Cardiac variation of inferior vena cava: new concept in the evaluation of intravascular blood volume.

Evaluation of the intravascular blood volume is an important assessment in emergency and critical care medicine. Measurement of the inferior vena cava (IVC) respiratory variation by ultrasound echography is useful, but it entails subjective problems. We have hypothesized that IVC cardiac variation is also correlated with intravascular blood volume and analyzed it automatically using computer software of two kinds, later comparing the results. Snakes, software to track boundaries by curve line continuity, and template matching software were incorporated into a computer with an ultrasound machine to track the short-axis view of IVC automatically and analyze it with approximation by ellipse. Eight healthy volunteers with temporary mild hypovolemia underwent echography before and after passive leg raising and while wearing medical anti-shock trousers. IVC cardiac variation was visually decreased by both leg raising and medical anti-shock trousers. The collapse index (maximum-minimum/maximum) of area during three cardiac beats was decreased showing a good relationship to fluid load simulations; 0.24±0.03 at baseline versus 0.11±0.01 with leg raising and 0.12±0.01 with medical anti-shock trousers. In conclusion, IVC cardiac variation has the potential to provide an evaluation of water volume. It presents some advantages in mechanical analysis over respiratory variation. At the very least, we need to exercise some caution with cardiac variation when evaluating respiratory variation.

Hemodynamic effects of positive end-expiratory pressure during abdominal hyperpression: A preliminary study in healthy volunteers

PurposeAn increase in abdominal pressure induces an increase in left ventricular afterload under clinical conditions. We tested the hypothesis that positive end-expiratory pressure (PEEP) could reverse the hemodynamic consequences of abdominal hyperpression by opposing the increase in left ventricular afterload. Materials and methodsEight healthy volunteers were investigated during 3 experimental conditions: (1) baseline, (2) increase in abdominal pressure by means of medical antishock trousers (MAST) inflation, and (3) addition of PEEP +10 cm H2O. Heart loading conditions and left ventricular systolic and diastolic function were assessed by transthoracic echocardiography. ResultsThe application of PEEP significantly reduced the prior increase in end-systolic wall stress: 45 ± 11 vs 55 ± 14 kdyn/cm2, P < .05. Medical antishock trousers inflation significantly altered the deceleration time of mitral E wave: 199 ± 23 vs 156 ± 38 milliseconds, P < .05. Left ventricular preload and global systolic performance were unaffected by MAST and PEEP applications. ConclusionsThe increase in left ventricular afterload induced by MAST inflation can be efficiently reduced by the use of a moderate PEEP. Potential clinical applications in the abdominal compartment syndrome or in the setting of laparoscopic surgery should be developed.

Strip of the Month: February 2011

Strip of the Month: February 2011

Noninvasive Assessment of Cardiac Index in Healthy Volunteers: A Comparison Between Thoracic Impedance Cardiography and Doppler Echocardiography

Thoracic bioimpedance cardiography (ICG) has been proposed as a noninvasive, continuous, operator-independent, and cost-effective method for cardiac output monitoring. In the present study, we compared cardiac index (CI) measurements with ICG (Niccomo device) and transthoracic Doppler echocardiography in resting healthy volunteers undergoing hemodynamic load challenge. Twenty-five healthy volunteers (7 men and 18 women, mean age 36 +/- 6 yr, body surface area 1.75 +/- 0.17 m(2)) were investigated during three experimental conditions: baseline, positive end-expiratory pressure + 10 cm H(2)O and lower body positive pressure by means of medical antishock trousers inflated to 30 cm H(2)O in the abdominal compartment. ICG signal quality was >89% over all sets of measurements. A weak but significant relationship was observed between CI(TTE) and CI(ICG) (r = 0.36; P = 0.002). Agreement between both techniques was 0.94 L x min(-1) x m(-2) (95% CI: 0.77-1.11), limits of agreement were -0.47 to 2.35 L x min(-1) x m(-2), and percentage error was 53%. No statistically significant relationships were found between percent changes in CI(TTE) and CI(ICG) after applications of positive end-expiratory pressure + 10 cm H(2)O (r = 0.21; P = 0.31) and medical antishock trousers (r = 0.22; P = 0.30). Poor correlation and lack of agreement between absolute values of CI measured by ICG and transthoracic Doppler echocardiography were found in resting healthy volunteers. The Niccomo device was also unreliable for monitoring changes in CI during hemodynamic load challenge.

The interaction of central command and the exercise pressor reflex in mediating baroreflex resetting during exercise in humans

Central command and the exercise pressor reflex can independently reset the carotid baroreflex (CBR) during exercise. The present investigation assessed the interactive relationship between these two neural mechanisms in mediating baroreflex resetting during exercise. Six men performed static leg exercise at 20% maximal voluntary contraction under four conditions: control, no perturbation; neuromuscular blockade (NMB) induced by administration of the neuromuscular blocking agent Norcuron (central command activation); MAST, application of medical antishock trousers inflated to 100 mmHg (exercise pressor reflex activation); and Combo, NMB plus MAST (concomitant central command and exercise pressor reflex activation). With regard to CBR control of heart rate (HR), both NMB and Combo conditions resulted in a further resetting of the carotid-cardiac stimulus-response curve compared to control conditions, suggesting that CBR-HR resetting is predominately mediated by central command. In contrast, it appears that CBR control of blood pressure can be mediated by signals from either central command or the exercise pressor reflex, since both NMB and MAST conditions equally augmented the resetting of the carotid-vasomotor stimulus-response curve. With regard to the regulation of both HR and blood pressure, the extent of CBR resetting was greater during the Combo condition than during overactivation of either central command or the exercise pressor reflex alone. Therefore, we suggest that central command and the exercise pressor reflex interact such that signals from one input facilitate signals from the other, resulting in an enhanced resetting of the baroreflex during exercise.

Effects of exercise pressor reflex activation on carotid baroreflex function during exercise in humans.

1. This investigation was designed to determine the contribution of the exercise pressor reflex to the resetting of the carotid baroreflex during exercise. 2. Ten subjects performed 3.5 min of static one-legged exercise (20 % maximal voluntary contraction) and 7 min dynamic cycling (20 % maximal oxygen uptake) under two conditions: control (no intervention) and with the application of medical anti-shock (MAS) trousers inflated to 100 mmHg (to activate the exercise pressor reflex). Carotid baroreflex function was determined at rest and during exercise using a rapid neck pressure/neck suction technique. 3. During exercise, the application of MAS trousers (MAS condition) increased mean arterial pressure (MAP), plasma noradrenaline concentration (dynamic exercise only) and perceived exertion (dynamic exercise only) when compared to control (P < 0.05). No effect of the MAS condition was evident at rest. The MAS condition had no effect on heart rate (HR), plasma lactate and adrenaline concentrations or oxygen uptake at rest and during exercise. The carotid baroreflex stimulus-response curve was reset upward on the response arm and rightward to a higher operating pressure by control exercise without alterations in gain. Activation of the exercise pressor reflex by MAS trousers further reset carotid baroreflex control of MAP, as indicated by the upward and rightward relocation of the curve. However, carotid baroreflex control of HR was only shifted rightward to higher operating pressures by MAS trousers. The sensitivity of the carotid baroreflex was unaltered by exercise pressor reflex activation. 4. These findings suggest that during dynamic and static exercise the exercise pressor reflex is capable of actively resetting carotid baroreflex control of mean arterial pressure; however, it would appear only to modulate carotid baroreflex control of heart rate.

Echocardiographic Evaluation of Left Ventricular Function in Critically Ill Patients: Dynamic Loading Challenge Using Medical Antishock Trousers

We hypothesized that a dynamic left ventricular (LV) evaluation during a loading challenge might enhance diagnostic capabilities of routine transesophageal echocardiography in critically ill patients and selection of therapeutic options against circulatory failure, particularly the choice between volume expansion and vasoactive agent infusion. Prospective clinical study in a group of 26 patients requiring hemodynamic support by vasoactive infusion because of low systemic arterial pressure (< 90 mm Hg by invasive monitoring) during mechanical ventilation. University hospital ICU. Patients required respiratory support for an episode of acute respiratory failure of various causes or for an episode of coma. They were studied by transesophageal echocardiography during mechanical ventilation in the controlled mode, before and during a loading challenge made using the legs compartment of medical antishock trousers inflated at 80 mm Hg. A short-axis view of the left ventricle was obtained by a transgastric approach, and end-diastolic and end-systolic areas were measured. LV stroke area (LVSA) and LV fractional area contraction (LVFAC) were calculated. Changes in LV echocardiographic measurements permitted separation of the patients into two groups. In nine patients (group 1), LVSA, used as an index of stroke output, was significantly increased during the challenge, together with a significant increase in LV end-diastolic area, suggesting preload improvement by the challenge. Conversely, in 17 patients (group 2), LVSA was significantly reduced by the challenge, together with a significant decrease in LVFAC, suggesting a negative effect of increased afterload by the challenge. Study of the changes in LV dimensions during loading challenge in hemodynamically unstable patients was used to evaluate the balance between the adequacy of preload and the ability of the heart to pump against an increased load, and might thus guide hemodynamic support.

Deep Venous Thrombosis in the Pediatric Trauma Population: An Unusual Event: Report of Three Cases

The incidence of deep venous thrombosis (DVT) in the pediatric population has been reported to be lower than in adults. Pediatric trauma patients have predisposing risk factors for DVT similar to those in the general trauma population. We reviewed the records of 2746 children under 16 years of age admitted to our Level I pediatric trauma service from 1989 to 1997. Only three cases of DVT were documented, all adolescents. DVT was located in the upper (n = 1) and lower (n = 1) extremity venous system. One patient presented with pulmonary embolism alone without identifiable DVT. Risk factors found were venous system manipulations, including atriocaval shunt, subclavian central line, and hyperinflated medical antishock trousers garment. Therapy consisted of heparin followed by warfarin anticoagulation. A vena cava filter was inserted in one patient for whom systemic anticoagulation was contraindicated. No DVT was seen in 1123 closed head injury patients or 29 spinal cord injury patients without associated risk factors. The thrombotic risk in pediatric trauma patients is low. Routine screening or prophylaxis is not indicated except for patients who are likely to remain immobile for an extended period of time and require prolonged rehabilitation, have venous manipulations, or present with clinical symptoms. Hematologic evaluation in patients with diagnosed DVT is necessary to identify individual risk factors.

Abdominal haemorrhage — a preventable cause of death after field stabilization?

The causes of preventable death vary in different operational settings, and the topic has not previously been explored in a fully developed central European rescue system. The factors associated with potentially preventable death were studied in a retrospective study of 430 fatal traffic accident victims (1980–96) in Lörrach County, Germany. Mission protocols could be retrieved for detailed analysis in 239 of the cases. These were studied in order to identify factors associated with preventable death. At the scene of the accident, 38% of the patients died without cardiopulmonary resuscitation (CPR) and 18% after CPR. Four patients died after a certain delay without CPR before reaching hospital. A total of 43% of the victims were admitted to hospital, 5% had received prehospital CPR and the remaining 38% had not. In a subgroup representing the experience of a single emergency physician 60 fatalities were studied. Of these, 27 (45%) patients died within the hospital; almost half of these cases (13/27) had been conscious at some time after the accident and of these, seven (7/13) died from intra-abdominal bleeding within 4 h after admission. The same cause of death was found in 3 of the 14 comatose patients. Pleural drainage was carried out in four patients and unrecognized pneumothoraces or spinal injuries did not occur. Tracheal intubation was employed in 24/27. Medical antishock trousers (MAST) were not available. The data indicate that intra-abdominal haemorrhage is an underestimated cause of death in a comprehensive rescue system, possibly as a consequence of field stabilization. The use of MAST may be a relevant therapeutic option to prevent these fatalities. The method offers the possibility of intra-abdominal compression and haemostasis after tracheal intubation has been performed. Previous controlled studies on MAST may have been biased by faulty methodology (e.g. absence of tracheal intubation) and inappropriate indications (e.g. other causes of shock). The value of MAST in comprehensive rescue systems should therefore be reassessed. The difficulties in identifying factors leading to preventable death in a retrospective analysis, are discussed and it is recommended that a permanent prospective quality control be performed in all cases of fatal accidents in order to ensure the continued improvement of prehospital emergency medical systems.

Delayed diagnosis of vascular injuries during lumbar discectomy

We report an accidental perforation of the left iliac artery and vein during lumbar discectomy in the kneeling position. During the surgical procedure, a brief and transient hypotension occurred, although the surgeon did not observe any abnormal bleeding in the operating field. In the recovery room, arterial blood pressure decreased, and tachycardia, pallor, and abdominal pain occurred. Retroperitoneal bleeding was suspected. Immediate fluid rescucitation was initiated, anesthesia was continued, and red blood cells were ordered. The use of medical antishock trousers enabled temporization until vascular surgeons were ready. An emergent laparotomy was performed to repair vascular injuries. The delayed symptoms, use of medical antishock trousers, and implications for anesthetists are discussed.

Medical anti-shock trousers (pneumatic anti-shock garments) for circulatory support in patients with trauma.

Medical antishock trousers (MAST) have been used to increase venous return to the heart until definitive care could be given. This, combined with compression of blood vessels, is believed to cause the movement of blood from the lower body to the brain, heart and lungs. However, the equipment is expensive, and may have adverse effects. To quantify the effect on mortality and morbidity of the use of medical anti-shock trousers (MAST)/ pneumatic anti-shock garments (PASG) in patients following trauma. Trials were identified by searches of the Cochrane Injuries Group Trials Register, the Cochrane Controlled Trials Register, MEDLINE, EMBASE, BIDS ISI Service and Science Citation Index. References in relevant papers identified were followed up. A citation analysis of references to randomised controlled trials was conducted using the Science Citation Index. Authors of identified trials were contacted and asked about any other trials that may have been conducted, whether published or unpublished. Randomised and quasi-randomised trials of MAST/PASG in patients following trauma (excluding fractures of the extremities in which MAST/PASG may be used as a splint). Data were extracted independently by two reviewers. Data were collected on mortality, duration of hospitalisation and ICU stay, and quality of allocation concealment. Two trials were identified that met the inclusion criteria. These trials included 1202 randomised patients in total; however, data for only 1075 of these were available. The relative risk of death with MAST was 1.13 (95% CI 0.97 to 1.32). Duration of hospitalisation and of intensive care unit stay was longer in the MAST treated group. The weighted mean difference in the length of intensive care unit stay was 1.7 days (95% CI 0.33 to 2.98). There is no evidence to suggest that MAST/PASG application reduces mortality, length of hospitalisation or length of ICU stay in trauma patients and it is possible that it may increase these. These data do not support the continued use of MAST/PASG in the situation described. However, it should be recognised that, due to the poor quality of the trials, conclusions should be drawn with caution.

Hemodynamic effects of medical antishock trousers during mechanical ventilation.

To compare the hemodynamic effects of medical antishock trousers (MAST) inflation in mechanically ventilated patients with normal and poor left ventricular function. Twelve patients requiring respiratory support were divided into two groups according to baseline transesophageal echocardiography (TEE) measurements: normal left ventricular dimensions and fractional area of contraction (FAC=61 +/- 5%) (n=7) and dilated cardiomyopathy with reduced FAC (21 +/- 1%) (n=5). All patients were studied when two successive levels of load (mild load by inflation of the leg compartment of MAST at 50 cmH2O and high load by adding the abdominal compartment of MAST inflated at 30 cmH2O) were applied. Global left ventricular systolic function was assessed on the TEE transgastric short-axis view. End-systolic wall stress (ESWS) was used as an indicator of left ventricular afterload. Total respiratory, lung and chest wall compliances were reduced by 48%, 51% and 27% respectively at the high load level (P < 0.05). Whereas no hemodynamic changes occurred at mild load, the high load level produced an increase in left ventricular afterload as evidenced by concomitant increases in diastolic arterial blood pressure (66 +/- 6 to 79 +/- 6 mmHg, P < 0.05) and ESWS (69 +/- 12 to 74 +/- 12 Kdyn x cm(-2) x m(-2), P < 0.05). In patients with dilated cardiomyopathy, this increase in afterload impaired the left ventricular systolic function and end-systolic area increased (19.0 +/- 2.5 to 21.4 +/- 2.9 cm2 x m(-2), P < 0.05) while FAC decreased (22 +/- 2 to 16 +/- 2%, P < 0.05). Left ventricular end-diastolic area remained unchanged during the study in both groups. MAST inflation impairs respiratory mechanics and global left ventricular systolic function in cardiac patients without changes in left ventricular preload.

Oxygen consumption and delivery relationship in brain-dead organ donors

The oxygen delivery (DO2) and consumption (VO2) relationship in brain-dead organ donors is unknown. Therefore, in a prospective study, we determined the DO2/VO2 relationship in 21 consecutive brain-dead patients. Patients were allocated to one of two groups, according to plasma lactate concentration: normal (group NL, n = 11) or high (> 2.5 mmol litre-1) (group HL, n = 10). VO2 was measured independently, using indirect calorimetry, under control conditions, during low DO2 challenge with PEEP administration, and high DO2 challenge with inflation of medical antishock trousers and volume expansion or blood transfusion, as required. Under control conditions, there were no significant differences between groups NL and HL in haemodynamic or oxygenation variables, both groups having a low VO2 (mean 114 (SD 21) ml min-1 m-2). In group HL there was a different DO2/VO2 relationship pattern, with a dependent VO2 only. The mean slope of the DO2/VO2 relationship was significantly higher in group HL than in group NL (0.12 (0.09) vs 0.04 (0.07), P < 0.05). We conclude that brain death was associated with a low VO2, and patients in group HL exhibited DO2/VO2 dependency which was not observed in patients in group NL.

Ventilatory Effects of Medical Antishock Trousers in Healthy Volunteers

The ventilatory effects of medical antishock trousers (MAST) were investigated using 10 healthy volunteers. Use of the MAST (60-80 mm Hg) decreased forced expiratory volume (-8% +/- 4%, p less than 0.01), vital capacity (-8% +/- 5%, p less than 0.01), and functional residual capacity (-12% +/- 6%, p less than 0.01) and induced a significant decrease in tidal volume (-30% +/- 17%, p less than 0.05), but minute ventilation was unmodified because of a concomitant increase in respiratory rate (+17% +/- 8%, p less than 0.001). The MAST modified the breathing pattern: the abdominal contribution to ventilation was markedly decreased (-57% +/- 22%, p less than 0.001), suggesting a decrease in the diaphragmatic contribution to ventilation. The MAST increased both the end-expiratory (+131% +/- 115%, p less than 0.01) and inspiratory variation (delta Pgas: +42% +/- 40%, p less than 0.05) of gastric pressure, whereas the end-expiratory and inspiratory variation of esophageal pressure remained unchanged. Because of a higher delta Pgas, the dynamic compliance of the abdominal compartment markedly fell (-77% +/- 10%, p less than 0.001). Transdiaphragmatic pressure (Pdi: +28% +/- 30%, p less than 0.05) significantly increased and the pressure-time index of the diaphragm significantly increased (+32% +/- 32%, p less than 0.05) after inflation of the MAST, suggesting an increase in the diaphragmatic cost of breathing. Inspiratory activity of the parasternal intercostal muscles significantly increased after the MAST was inflated. Computerized tomography showed that the MAST induced a cephalad shift of the diaphragm, which reduced pulmonary height.(ABSTRACT TRUNCATED AT 250 WORDS)

High versus low inflation pressures of medical anti-shock trousers (MAST) in severe hemorrhagic hypovolemia: Barriot P, Riou B, Viars P JEUR 1:117–120 1989

High versus low inflation pressures of medical anti-shock trousers (MAST) in severe hemorrhagic hypovolemia: Barriot P, Riou B, Viars P JEUR 1:117–120 1989

Central haemodynamic changes during lower body positive pressure in patients with congestive cardiac failure

Fifteen patients with moderately severe and severe chronic congestive heart failure were studied to determine the central haemodynamic results of short term increases in lower body positive pressure. Central haemodynamic variables were determined by Swan-Ganz thermodilution catheterisation and arterial cannulation. Graded increases in lower body positive pressure were applied to supine patients using Medical Anti-Shock Trousers (MAST). Increasing lower body positive pressure by 25 mm Hg and 55 mm Hg caused increases in mean right atrial pressure (6.0 to 13.2 to 17.9 mm Hg; p less than 0.001 and p less than 0.0001 respectively) and mean pulmonary artery pressure (26.8 to 35.5 to 41.3 mm Hg; p less than 0.05 and p less than 0.01 respectively). No significant changes were seen in left heart filling pressures or in pulmonary vascular resistance. Furthermore, there were no significant increases in indices of cardiac work (cardiac index, left ventricular stroke work index, right ventricular stroke work index or cardiac power output) despite the increased right heart filling pressures. These results show that in patients with longstanding severe congestive heart failure, short term increases in cardiac return may increase right heart pressures but do not appear to cause either beneficial or detrimental changes in left heart haemodynamic indices.

Medical Anti-Shock Trousers: Blind Faith, Poor Judgment and Patient Jeopardy

The oft-repeated historic development of the pneumatic lower body compression suit (MAST, PASG) for the presumed treatment of hypotension has been well-documented by McSwain(l). While the experimental and anecdotal clinical observations of Crile, Gardner, Wangenstein and Kaplan are interesting, they are not prospective, controlled, randomized clinical trials in humans(2,3,4,5). In the early 1970s, the EMS community was ripe for the bandwagon reflex to grasp at any and all gimmicks and gadgets which became available, regardless of a lack of evidence regarding their safety or danger to patients. Inventions such as the esophageal obturator airway, various darts, MAST, external cardiac bumpers, percutaneous trachea obturators, and many others simultaneously were thrust upon the unsuspecting and unprotected patient community. Some of these innovations may have been beneficial but others were dangerous. Contending that some intervention in a “life threatening, good Samaritan situation” was better than no interventional treatment or “stabilization” at all, the paramedics' blind faith in these modalities persisted. The Medical Device Amendment of 1976 (6), which requires safety and efficacy for devices, similar to that long in effect for new drugs, had not yet been enacted into law to require premarketing clearance of new medical devices. Building on blind faith and premature recommendations regarding in the unproven concept of MAST, the EMS community exercised poor judgment in recommending to state legislators that this unproven device be “required equipment” on board ambulances. Furthermore, this small cadre of “special interest groups” lobbied to have the MAST mandated as essential equipment in trauma centers(7,8). Although the minutes of the trauma planning meetings do not reflect the debate at the American College of Surgeons Committee on Trauma, numerous voices of advised constraint, said “go slow” on including the MAST as part of the ATLS course and the ACS optimal resources document.

Medical Anti-Shock Trousers: Pneumatic Anti-Shock Garment: Does it Work?

The use of the Pneumatic Anti-Shock Garment (PASG) has created much controversy in prehospital care. It is interesting that such an inexpensive device and technique has created so much controversy regarding effectiveness when expensive devices and techniques, such as coronary artery bypass, carotid endarteroectomy, and laser angioplasty have been questioned as to effectiveness, but have not created as much controversy.Where do we stand on the PASG today? One well-done, randomized, prospective study has been reported as several different papers. In reality, these reports originate from only one study (1-5). This is compared to more than 200 other studies, many of which have been randomized, prospective studies in animals using the same quality as the randomized, prospective study done on humans. Such studies have the advantage of having better isolation of the specific condition being studied. It does not seem appropriate to base the clinical use or non-use on just one study. All studies should be reviewed and placed in context when attempting to identify the role the PASG has in patient care.