EXTERNAL HIGH-FREQUENCY OSCILLATION IN NORMAL SUBJECTS AND IN PATIENTS WITH ACUTE RESPIRATORY-FAILURE

External high frequency oscillation was performed on 20 healthy volunt eers using a cuirass-based system, the Hayek Oscillator. Five-min peri ods of oscillation were carried out on each subject at frequencies of 1, 2, 3, 4 and 5 Hz. Effective ventilation was measured in terms of th e fall in alveolar partial pressure of carbon dioxide immediately afte r oscillation. The optimum frequency for oscillation was 1-3 Hz but mo st of tile subjects were adequately ventilated over a wide range of fr equencies. Thus, the Hayek Oscillator is capable of adequately ventila ting normal subjects by means of chest wall oscillation. We also compa red external high frequency oscillation with intermittent positive pre ssure ventilation in five patients with respiratory failure. Using the same inspired oxygen fraction, the external high frequency oscillatio n replaced intermittent positive pressure ventilation for a 30-min per iod. External high frequency oscillation improved oxygenation by 16% a nd reduced the arterial carbon dioxide by 6%. These preliminary findin gs suggest that normal subjects and intensive care unit patients can b e adequately ventilated by means of external high frequency oscillatio n.