Hemodynamic effects of high-frequency oscillatory ventilation in acute respiratory distress syndrome
© BioMed Central Ltd. 2007
Published: 22 March 2007
High-frequency oscillatory ventilation (HFOV) is a promising ventilatory modality for ARDS patients having refractory hypoxemia despite standard ARDS ventilation. Hemodynamic alterations while switching the patient from volume-controlled ventilation (VCV) to HFOV are not yet well studied.
To evaluate immediate (within 3 hours) hemodynamic effects of HFOV in ARDS patients with septic shock needing vasopressor support.
Patients having a PO2/FiO2 ratio ≤150, PEEP >12 cm and FiO2 requirement ≥0.7 on VCV (6 ml/kg) were switched to HFOV. The initial continuous distending pressure (CDP) of HFOV was 5 cm above the mean airway pressure during VCV. Other HFOV settings were FiO2 1, bias flow 30 l/min, amplitude 70 cm and frequency 7 Hz. The CDP was adjusted to maintain oxygen saturation >88%. Fluid bolus before switching to HFOV was avoided. All the patients were sedated and paralysed during the study period. A drop in the mean arterial pressure (MAP) ≤65 mm or cardiac index (CI) ≤2.5 l/min/m2 were treated with escalation of inotrope if required. Hemodynamic monitoring was done with the Flotrac-Vigileo monitoring system.
Switching of an ARDS patient from VCV to HFOV does not impart significant hemodynamic instabilities and can be safely done.