How Do Oscillatory Amplitude Changes in High Frequency Oscillatory Ventilation Affect PaCO₂ and PaO₂?

Abstract 100

Introduction: A multiparameter intra-arterial sensor (MPIAS) now allows continuous arterial blood gas (ABG) monitoring during high frequency oscillatory ventilation (HFOV). Our early HFOV strategy increases mean airway pressure until FiO₂ <30%. This signals optimal alveolar recruitment, lung volume and increased lung compliance.

Subjects: 11 preterm infants: median birth weight 1150g; gestation 28 wk

Methods: Continuous MPIAS ABG data were collected during 28 changes in the amplitude of oscillation during HFOV and stratified according to FiO₂ (table). The changes were either clinically determined or part of a random sequence. For each amplitude change, the maximum change (from baseline) in PaCO₂ and PaO₂ over the following 30 mins, was determined.

Table 1 No caption available.

Results: All increases in amplitude resulted in an instant fall in PaCO₂ completed in 30 mins. Decreases in amplitude resulted in a similar PaCO₂ rise. Changes in amplitude did not affect PaO₂ where FiO₂ was >40% but had clear effects when FiO₂ was <30% (P<0.001).

Conclusions: These findings may optimise use of amplitude changes during HFOV and may be due to increased lung compliance at optimal lung volume.