Normocapnic high-frequency oscillatory ventilation affects differently extrapulmonary and pulmonary forms of acute respiratory distress syndrome in adults

The recently reported differences between pulmonary and extrapulmonary acute respiratory distress syndromes (ARDS(P), ARDS(exp)) are the main reasons of scientific discussion on potential differences in the effects of current ventilatory strategies. The aim of this study is to assess whether the presence of ARDSP or ARDS,,P can differently affect the beneficial effects of high-frequency oscillatory ventilation (HFOV) upon physiological and clinical parameters. Thirty adults fulfilling the ARDS criteria were indicated for HFOV in case of failure of conventional ventilation strategy. According to the ARDS type, each patient was included either in the group of patients with ARDSP or ARDS,,P. Six hours after normocapnic HFOV introduction, there was no significant increase in PaO2/F1O2 in ARDS(P) group (from 129 +/- 47 to 133 +/- 50 Torr), but a significant improvement was found in ARDS,,p (from 1 14 54 to 200 65 Torr, p < 0.01). Despite the insignificant difference in the latest mean airway pressure (MAP) on conventional mechanical ventilation (CMV) between both groups, initial optimal continuous distension pressure (CDP) for the best PaO2/F1O2 during HFOV was 2.0 +/- 0.6 kPa in ARDS(P) and 2.8 +/- 0.6 kPa in ARDS(exp) (p < 0.01). HFOV recruits and thus it is more effective in ARDS(exp). ARDS(exp) patients require higher CDP levels than ARDS(p) patients. The testing period for positive effect of HFOV is recommended not to be longer than 24 hours.