Critical care medicine
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Critical care medicine · Sep 1984
Airway pressure as a measure of gas exchange during high-frequency jet ventilation.
Airway pressure during high-frequency jet ventilation (HFJV) reflects safety, ventilator performance, and gas exchange. The value of airway pressure as a monitoring and control variable for predicting the effectiveness of gas exchange was examined in 2 studies using healthy dogs. In the first study, HFJV was delivered to the airway via an extra lumen in the wall of an endotracheal tube, at a frequency of 150 cycle/min and 30% inspiratory time. ⋯ The airway pressure difference correlated strongly with efficiency of gas exchange for both CO2 elimination and oxygenation. Mean and end-expiratory pressures showed little influence over moderate ranges, but use of 15 cm H2O of PEEP decreased efficiency of both CO2 elimination and oxygenation, presumably due to increased dead space because of lung overdistension. We conclude that the airway pressure difference, measured as far distal in the airway as is safe and practical, can be useful for monitoring and controlling HFJV.
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Six mongrel dogs, each serving as its own control, underwent ventilatory trials on high-frequency positive-pressure ventilation (HFPPV) and high-frequency oscillation (HFO), before and after oleic acid-induced lung injury. Central and distal airway pressures were compared to simultaneous measurements of oxygen transport and shunt fraction. Airway pressure differences were more pronounced with HFO. ⋯ Shunt fraction increased with decreased oxygen transport after lung injury in both models; however, the increase was less pronounced with HFO, which maintained a greater pressure gradient. The distal increase in airway pressures may be important in maintaining critical closing volumes in the diseased lung. By creating a pressure gradient, high-frequency ventilation by either jet or oscillator may improve functional residual capacity and oxygenation.
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It is suspected, but still unproven, that the increased capillary permeability which accompanies sepsis and contributes to the development of pulmonary edema (PE) involves systemic as well as pulmonary capillaries. We investigated the relationship between the colloid osmotic pressure of serum (COPS) and edema fluid (COPE) in 16 septic and 19 nonseptic patients with severe generalized edema. COPS values of septic and nonseptic patients were not significantly different (14.6 +/- 2.1 and 15.8 +/- 3.4 torr, respectively). ⋯ Thus, 16/17 determinations in septic patients had a ratio greater than .1, while 17/22 determinations in nonseptic patients showed a ratio less than .1. PE was present in 8/16 septic patients but in only 2/19 nonseptic patients. These data suggest that the increase in capillary permeability during sepsis is generalized.
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The ability to recognize symptoms, to make priority decisions, to dispatch suitable ambulance transport and inform the crews, and finally, to initiate first aid via the caller is essential for optimum care of severely injured or ill patients outside the hospital. In Sweden, a special job-related course trains dispatch-center personnel to think in terms of symptoms and evolution of the victim's status, and to assess the level of seriousness.