Pneumatic anti-shock garment--does it have a future?
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A total of 100 accident and emergency (A&E) departments in the UK responded to a questionnaire about their use of the pneumatic anti-shock garment (PASG). Less than one in 10 departments used PASG in their prehospital care system, less than one in five departments used PASG during in-patient care, and there was wide variation in PASG usage in those situations for which their use is recommended by the Advanced Trauma Life Support (ATLS) course. (+info)
Changes in respiratory resistance to low dose carbachol inhalation and to pneumatic trouser inflation are correlated.
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Inflation of the leg compartments of pneumatic trousers increases thoracic blood volume. The resultant response in respiratory impedence was investigated in nine normal volunteers, and compared with the response to increasing doses of inhaled carbachol. Respiratory impedance was measured by the forced oscillation technique (4-32 Hz), and respiratory resistance at zero frequency (R0) was extrapolated from linear regression analysis of resistive impedance versus frequency. The mean increase in R0 was 31% after inhalation of 125 micrograms carbachol, and 21% after inflation of pneumatic trousers. The percentage changes in R0 following pneumatic trouser inflation highly correlated those induced by inhalation of 125 micrograms carbachol (r = 0.98) Our data demonstrate that, even in normal subjects, pneumatic trouser inflation causes an increase in respiratory resistance, which can be predicted by the response to a low dose of carbachol. These results support the assumption that cholinergic agents might not only be bronchoconstrictors but also vasodilators of the bronchial vessels. At a low dose, the vasodilating action of carbachol could be the major factor involved in the respiratory response. (+info)
A preliminary study of cardiopulmonary resuscitation by circumferential compression of the chest with use of a pneumatic vest.
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BACKGROUND: More than 300,000 people die each year of cardiac arrest. Studies have shown that raising vascular pressures during cardiopulmonary resuscitation (CPR) can improve survival and that vascular pressures can be raised by increasing intrathoracic pressure. METHODS: To produce periodic increases in intrathoracic pressure, we developed a pneumatically cycled circumferential thoracic vest system and compared the results of the use of this system in CPR (vest CPR) with those of manual CPR. In phase 1 of the study, aortic and right-atrial pressures were measured during both vest CPR (60 inflations per minute) and manual CPR in 15 patients in whom a mean (+/- SD) of 42 +/- 16 minutes of initial manual CPR had been unsuccessful. Vest CPR was also carried out on 14 other patients in whom pressure measurements were not made. In phase 2 of the study, short-term survival was assessed in 34 additional patients randomly assigned to undergo vest CPR (17 patients) or continued manual CPR (17 patients) after initial manual CPR (duration, 11 +/- 4 minutes) had been unsuccessful. RESULTS: In phase 1 of the study, vest CPR increased the peak aortic pressure from 78 +/- 26 mm Hg to 138 +/- 28 mm Hg (P < 0.001) and the coronary perfusion pressure from 15 +/- 8 mm Hg to 23 +/- 11 mm Hg (P < 0.003). Despite prolonged unsuccessful manual CPR, spontaneous circulation returned with vest CPR in 4 of the 29 patients. In phase 2 of the study, spontaneous circulation returned in 8 of the 17 patients who underwent vest CPR as compared with only 3 of the 17 patients who received continued manual CPR (P = 0.14). More patients in the vest-CPR group than in the manual-CPR group were alive 6 hours after attempted resuscitation (6 of 17 vs. 1 of 17) and 24 hours after attempted resuscitation (3 of 17 vs. 1 of 17), but none survived to leave the hospital. CONCLUSIONS: In this preliminary study, vest CPR, despite its late application, successfully increased aortic pressure and coronary perfusion pressure, and there was an insignificant trend toward a greater likelihood of the return of spontaneous circulation with vest CPR than with continued manual CPR. The effect of vest CPR on survival, however, is currently unknown and will require further study. (+info)
Oxygen consumption and delivery relationship in brain-dead organ donors.
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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. (+info)
Sequential mechanical and pharmacological thromboprophylaxis in the surgery of hip fractures. A pilot study.
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Two hundred and thirty-eight patients with femoral neck fractures were entered into a randomised pilot study comparing the use of sequential treatment by 'Flowtron DVT' garments in the perioperative period followed by Enoxaparin (Clexane-Rhone-Poulenc Rorer), and Enoxaparin alone. One hundred and ninety-three patients were excluded indicating the difficulty of achieving pure comparisons in this population. The remaining 44 were randomised: 21 received Enoxaparin from the time of admission, and 23 had sequential treatment. There was no statistically significant difference in the incidence of thromboembolism. Patient preference did not indicate a favoured treatment subjectively. The operation field was drier in the sequential group, although this did not reach significance. Sequential treatment was not shown to be better or worse than treatment with Enoxaparin, but the trends favoured sequential treatment rather than drug treatment alone. The technique allows the operation to be carried out without the problems produced by low dose heparins and mobilisation is not hindered by compression garments. (+info)
Reflex responses to regional venous pooling during lower body negative pressure in humans.
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Lower body negative pressure is frequently used to simulate orthostasis. Prior data suggest that venous pooling in abdominal or pelvic regions may have major hemodynamic consequences. Therefore, we developed a simple paradigm for assessing regional contributions to venous pooling during lower body negative pressure. Sixteen healthy men and women underwent graded lower body negative pressure protocols to 60 mmHg while wearing medical anti-shock trousers to prevent venous pooling under three randomized conditions: 1) no trouser inflation (control), 2) only the trouser legs inflated, and 3) the trouser legs and abdominopelvic region inflated. Without trouser inflation, heart rate increased 28 +/- 4 beats/min, mean arterial pressure fell -3 +/- 2 mmHg, and forearm vascular resistance increased 51 +/- 9 units at 60 mmHg lower body negative pressure. With inflation of either the trouser legs or the trouser legs and abdominopelvic region, heart rate and mean arterial pressure did not change during lower body negative pressure. By contrast, although the forearm vasoconstrictor response to lower body negative pressure was attenuated by inflation of the trouser legs (delta forearm vascular resistance 33 +/- 10 units, P < 0.05 vs. control), attenuation was greater with the inflation of the trouser legs and abdominopelvic region (delta forearm vascular resistance 16 +/- 5 units, P < 0.05 vs. control and trouser legs-only inflation). Thus the hemodynamic consequences of pooling in the abdominal and pelvic regions during lower body negative pressure appear to be less than in the legs in healthy individuals. (+info)
Effects of positive pressure on both femoral venous and arterial blood velocities and the cutaneous microcirculation of the forefoot.
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OBJECTIVE: The balance between the apparent beneficial effect and the risk of arterial ischaemia resulting from an external uniform compression is unclear. The purpose of this study was to determine the effects of a positive uniform compression on the lower limb circulation until a critical threshold was reached. METHODS: We used Doppler ultrasound to measure femoral venous and arterial blood velocities. The effects of positive pressure on cutaneous microcirculation were evaluated by laser Doppler flux (LDF), transcutaneous oxygen pressure (tcpO2) and transcutaneous carbon dioxide pressure (tcpCO2) on the forefoot of 17 healthy subjects. RESULTS: The results are expressed as median [lowest observed value-highest observed value]. Whereas the arterial femoral velocity (A.F.V.) decreased from 0.21 [0.08-0.36] to 0.17 [0.08-0.28] m s-1 for an external pressure as low as 10 mmHg (p < 0.001), the venous femoral velocity (V.F.V.) decreased from 0.13 [0.06-0.40] to 0.09 [0.05-0.34] m s-1 at 20 mmHg (p < 0.001). An increase of tcpCO2 from 39.8 [29.9-53.7] to 40.2 [30.0-55.5] mmHg (p < 0.05) and a decrease of LDF from 8.7 [3.1-25.9] to 5.5 [2.3-21.1] A.U. (p < 0.001) occurred at 10 mmHg. However, tcpO2 decreased only from 76.7 [40.2-91.2] to 64.6 [18.9-85.2] mmHg when the splint pressure reached 60 mmHg (p < 0.05). The observed parameters (LDF, tcpO2, V.F.V. and A.F.V.) decreased further (except for tcpCO2 which increased) up to the end of the study as the applied pressure was increased. CONCLUSION: Positive pressure on the full leg provided no significant beneficial effect on femoral venous blood velocity. Whereas we showed that for an external uniform pressure as low as 10 mmHg, significant impairments in both arterial inflow of the lower limb and microcirculation of the forefoot appeared in recumbent healthy young subjects. (+info)