Assessment of neonatal ventilation during high-frequency oscillatory ventilation

OBJECTIVE: To determine alterations in high-frequency oscillatory ventilation (HFOV) performance during clinical ventilator management. DESIGN: Clinical investigation. SETTING: Two level III intensive care nurseries in Wilmington, Delaware, and Philadelphia, Pennsylvania. PATIENTS: Thirty infants 1.49 ± 1.01 kg with respiratory distress receiving HFOV. INTERVENTIONS: Due to the demonstrated benchtop load sensitivity of the HFOV (SensorMedics 3100), we hypothesized that measured tidal volume (Vt/kg) and high-frequency minute ventilation (HFMV) would vary inversely with respiratory rate adjustments and that ventilator performance will be affected with endotracheal tube (ETT) suctioning. Both Vt/kg and HFMV were recorded using a novel hot-wire anemometry technique at the time of ETT suctioning or changes in ventilator settings. MEASUREMENTS AND MAIN RESULTS: During HFOV it was found that Vt/kg = 2.52 ± 0.68 mL/kg and HFMV = 69 ± 45 ([mL/kg] × Hz); effective ventilation was observed in the range of HFMV = 29-113 ([mL/kg] × Hz). HFMV decreased with an increase in breathing frequency. Although there was a significant increase in the mean Vt/kg after suctioning events, there was no difference in Vt/kg or HFMV after disconnection of the ETT alone. There were significant alterations in HFOV performance as a result of clinical adjustments in respiratory rate and suctioning. In addition, we found that measured Vt during clinically effective HFOV is at least equivalent to expected deadspace. CONCLUSIONS: Measurement of tidal volume and HFMV may be clinically important in optimizing HFOV performance both during ETT suctioning and adjustments to breathing frequency.