Normocapnic High-frequency Oscillatory Ventilation Affects Differently Extrapulmonary and Pulmonary Forms of Acute Respiratory Distress Syndrome in Adults

J. PACHL, K. ROUBÍK¹, P. WALDAUF, M. FRIC, V. ZÁBRODSKÝ

University Department of Anesthesiology and Critical Care Medicine, Third Faculty of Medicine, Charles University, and ¹Faculty of Biomedical Engineering, Czech Technical University, Prague, Czech Republic

Received February 28, 2005
Accepted March 4, 2005
On-line available April 26, 2005


Summary
The recently reported differences between pulmonary and extrapulmonary acute respiratory distress syndromes (ARDSp, ARDSexp) 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 ARDSexp 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 ARDSexp. Six hours after normocapnic HFOV introduction, there was no significant increase in PaO2/FIO2 in ARDSp group (from 12947 to 13350 Torr), but a significant improvement was found in ARDSexp (from 114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/FIO2 during HFOV was 2.0±0.6 kPa in ARDSp and 2.8±0.6 kPa in ARDSexp (p<0.01). HFOV recruits and thus it is more effective in ARDSexp. ARDSexp patients require higher CDP levels than ARDSp patients. The testing period for positive effect of HFOV is recommended not to be longer than 24 hours.


Key words
High-frequency ventilation • High-frequency oscillation • ARDS • Hypoxemic index • Mechanical ventilation