Effect of changes in oscillatory amplitude on Paco(2) and Pao(2) during high frequency oscillatory ventilation

Aims-To describe the relation between oscillatory amplitude changes and art erial blood gas (ABG) changes in preterm infants receiving high frequency o scillatory ventilation, using a multiparameter intra-arterial sensor (MPIAS ). Methods-Continuous MPIAS ABG data were collected after amplitude changes an d stratified according to FIO2: high (> 0.4) or low (< 0.3). For each ampli tude change, the maximum change (from baseline) in Paco(2) and Pao(2) over the following 30 minutes was determined. In total, 64 oscillatory amplitude changes were measured in 21 infants (median birth weight 1040 g; gestation 27 weeks). Results-All. amplitude increases produced Paco(2) falls (median -0.98 and - 1.13 kPa for high and low FIO2 groups respectively). All amplitude decrease s produced Paco(2) rises (median +0.94 and +1.24 kPa for high and low FIO2 groups respectively). About 95% of the change in Paco(2) was completed in 3 0 minutes. Amplitude changes did not affect Pao(2) when FIO2 > 0.4. When FI O2 < 0.3, amplitude increases produced a Pao(2) rise (median = +1.1 kPa; P < 0.001) and amplitude decreases a fall (median = -1.2 kPa; P < 0.001). Conclusions-After oscillatory amplitude changes, the speed but not the magn itude of the Paco(2) change is predictable, and a rapid Pao(2) change accom panies the Paco(2) change in infants with mild lung disease and a low FIO2.