Chest
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Fifteen patients in the early stages of the adult respiratory distress syndrome with severe hypoxemia who were capable of maintaining adequate spontaneous ventilation were treated with continuous positive airway pressure (CPAP). The optimal level of CPAP was adjusted for each patient to achieve the highest oxygenation with the least adverse hemodynamic effects. ⋯ The improvement in pulmonary status was achieved with no significant changes in cardiac output or the arterial-mixed venous oxygen content difference. Early application of an adjusted level of positive end-expiratory pressure using CPAP in patients with adequate levels of fluid is an effective and safe method of treating selected groups of patients in the early stages of the adult respiratory distress syndrome.
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The mechanical work on the lung required during spontaneous breathing with positive end-expiratory pressure (PEEP) was compared with different methods of continuous positive airway pressure (CPAP) in nine young healthy athletes (surfers) at levels of 5, 10, 15, and 20 cm H2O. At the level of 20 cm H2O, PEEP increased the mean total work per minute by 116 percent and the total work per liter by 121 percent. The percent increase rose linearly with the level of PEEP. ⋯ Use of PEEP did not increase the functional residual capacity (FRC) in these spontaneously breathing subjects. In contrast, CPAP resulted in a rise in FRC proportional to the level of CPAP. This suggests that CPAP must be applied in a manner that maintains Paw constant to provide optimal assistance to ventilation.