Combined high-frequency ventilation for management of terminal respiratory failure: a new technique. 
Seven patients with severe adult respiratory distress syndrome (ARDS) developed terminal respiratory failure and severe hypoxemia (PaO2 below 50 mm Hg) with death imminent despite maximal ventilatory support with intermittent positive-pressure ventilation (IPPV) and positive end-expiratory pressure (PEEP).  High-frequency positive-pressure ventilation (HFPPV) was used in these patients for one day at a rate of 250 breaths/min, with slight improvement of PaO2 to a mean of 80 mm Hg.  High-frequency oscillatory (HFO) ventilation was used during the second day at a rate of 2000 breaths/min; this provided adequate oxygenation with a mean PaO2 of 244 mm Hg.  Nonetheless, during HFO there was progressive CO2 retention and respiratory acidosis (mean PCO2 67 mm Hg).  On the third study day, all seven patients were ventilated with combined high-frequency ventilation (CHFV) for a period from 5-21 days.  CHFV is based on the administration of HFPPV simultaneously with HFO and provided adequate oxygenation by accelerated gas diffusion and CO2 elimination by convection.  PaO2 was maintained during CHFV at a mean of 280 mm Hg.  CO2 elimination was adequate with a mean PaCO2 of 32 mm Hg.  Cardiac output also was adequately maintained during CHFV.  Moreover, CHFV was well tolerated in our patients, allowing them to communicate with their families and nurses.  CHFV successfully treated the hypoxemia of respiratory failure in all the patients.  However, five patients (71%) died of cardiac arrest as a result of multisystem failure despite adequate oxygenation (PaO2 above 80 mm Hg).