Multifrequency Oscillatory Ventilation in the Premature Lung Effects on Gas Exchange, Mechanics, and Ventilation Distribution

Background: Despite the theoretical benefits of high-frequency oscillatory ventilation (HFOV) in preterm infants, systematic reviews of randomized clinical trials do not confirm improved outcomes. The authors hypothesized that oscillating a premature lung with multiple frequencies simultaneously would improve gas exchange compared with traditional single-frequency oscillatory ventilation (SFOV). The goal of this study was to develop a novel method for HFOV, termed multifrequency oscillatory ventilation (MFOV), which relies on a broadband flow waveform more suitable for the heterogeneous mechanics of the immature lung. Methods: Thirteen intubated preterm lambs were randomly assigned to either SFOV or MFOV for 1 h, followed by crossover to the alternative regimen for 1 h. The SFOV waveform consisted of a pure sinusoidal flow at 5 Hz, whereas the customized MFOV waveform consisted of a 5-Hz fundamental with additional energy at 10 and 15 Hz. Per standardized protocol, mean pressure at airway opening and inspired oxygen fraction were adjusted as needed, and root mean square of the delivered oscillatory volume waveform (V-rms) was adjusted at 15-min intervals. A ventilatory cost function for SFOV and MFOV was defined as, where Wt denotes body weight. Results: Averaged over all time points, MFOV resulted in significantly lower V-C (246.9 6.0 vs. 363.5 +/- 15.9 ml(2) mmHg kg(-1)) and (12.8 +/- 0.3 vs. 14.1 +/- 0.5 cm H2O) compared with SFOV, suggesting more efficient gas exchange and enhanced lung recruitment at lower mean airway pressures. Conclusion: Oscillation with simultaneous multiple frequencies may be a more efficient ventilator modality in premature lungs compared with traditional single-frequency HFOV.