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Nine medical centers collaborated in a prospective randomized study to evaluate prolonged extracorporeal membrane oxygenation (ECMO) as a therapy for severe acute respiratory failure (ARF). Ninety adult patients were selected by common criteria of arterial hypoxemia and treated with either conventional mechanical ventilation (48 patients) or mechanical ventilation supplemented with partial venoarterial bypass (42 patients). Four patients in each group survived. The majority of patients suffered acute bacterial or viral pneumonia (57%). All nine patients with pulmonary embolism and six patients with posttraumatic acute respiratory failure died. The majority of patients died of progressive reduction of transpulmonary gas exchange and decreased compliance due to diffuse pulmonary inflammation, necrosis, and fibrosis. We conclude that ECMO can support respiratory gas exchange but did not increase the probability of long-term survival in patients with severe ARF.

Treatment of respiratory insufficiency using continuous positive pressure ventilation (CPPV) with positive end-expiratory pressure (PEEP) is often associated with high airway pressures and large tidal volumes resulting in parenchymal damage and an exacerbation of ventilation/perfusion mismatch. High-frequency jet ventilation and high-frequency oscillation purportedly provide adequate ventilation and might preclude these harmful side effects. Few data exist comparing these methods in a model of respiratory insufficiency. Respiratory insufficiency was produced in three groups of six rabbits by 15 pulmonary lavages with saline (35 ml kg-1) to remove surfactant, following which ventilation for the subsequent 5 hr was as follows: group I, CPPV with a frequency of 60 bpm, and a minute volume of 400 ml min-1 kg-1; group II, oscillatory ventilation with a loudspeaker system delivering a tidal volume of 6-8 ml at a frequency of 5 Hz; and group III, jet ventilation with volumes of 6-8 ml at a frequency of 5 Hz. All groups were ventilated with a PEEP of 10 cm H2O and a FiO2 of 1.0. Arterial blood samples were taken every hour. All three methods provided adequate oxygenation without important differences. The arterial pCO2 rose in all three groups owing to the seriousness of the respiratory insufficiency created. This rise was the highest with oscillatory ventilation. Three of the six rabbits deteriorated after 3 hr of jet ventilation and died with elevated pCO2S with pO2S with bloody edema coming out of the trachea. Because of this apparent damaging effect of jet ventilation and because oscillatory ventilation achieved the same gas exchange but at lower airway pressures as compared to jet ventilation and CPPV, it is thought that oscillatory ventilation is superior over both jet ventilation and CPPV for application in respiratory insufficiency.