Carbon dioxide clearance using bubble CPAP with superimposed high
frequency oscillations in a premature infant lung model with abnormal
lung mechanics
Abstract
Background: High frequency (HF) oscillatory ventilation has been shown
to improve CO2 clearance in premature infants. In a previous in vitro
lung model with normal lung mechanics we demonstrated significantly
improved CO2 washout by HF oscillation of bubble CPAP (BCPAP).
Objective: To examine CO2 clearance in a premature infant lung model
with abnormal lung mechanics via measurement of end-tidal CO2 levels
(EtCO2) while connected to HF oscillated BCPAP. Design/Methods: A 40mL
premature infant lung model with either: normal lung mechanics (NLM):
compliance 1.0 mL/cmH2O, airway resistance 56 cmH2O/(L/s); or abnormal
lung mechanics (ALM): compliance 0.5 mL/cmH2O, airway resistance 136
cmH2O/(L/s), was connected to BCPAP with HF oscillation at either
4,6,8,10 or 12 Hz. EtCO2 was measured at BCPAPs of 4,6 and 8 cmH2O and
respiratory rates (RR) of 40,60 and 80 breaths/min and 6mL tidal volume.
Results: HF oscillation decreased EtCO2 levels at all BCPAPs, RRs, and
oscillation frequencies for both lung models. Overall mean±SD EtCO2
levels decreased (p<0.001) from non-oscillated baseline by
19.3±10.2% for NLM vs. 14.1±8.8% for ALM. CO2 clearance improved for
both lung models (p<0.001) as a function of oscillation
frequency and RR with greatest effectiveness at 40-60 breaths/min and HF
at 8-12 Hz. Conclusions: In this in-vitro premature infant lung model,
HF oscillation of BCPAP was associated with improved CO2 clearance as
compared to non-oscillated BCPAP for both NLM and ALM. The significant
improvement in CO2 clearance in an abnormal lung environment is an
important step towards clinical testing of this novel respiratory
support modality.