RT Journal Article
SR Electronic
T1 Carbon Dioxide Elimination and Gas Displacement Vary With Piston Position During High-Frequency Oscillatory Ventilation
JF Respiratory Care
FD American Association for Respiratory Care
SP 361
OP 366
VO 50
IS 3
A1 Donna S Hamel
A1 Andrew L Katz
A1 Damian M Craig
A1 John D Davies
A1 Ira M Cheifetz
YR 2005
UL http://rc.rcjournal.com/content/50/3/361.abstract
AB INTRODUCTION: Alterations in gas displacement in pediatric patients ventilated with the Sensor Medics 3100A high-frequency oscillator are most commonly manipulated by adjusting the amplitude, frequency, and percent inspiratory time. The piston-position-and-displacement indicator is commonly centered and subsequently not adjusted. That practice may limit the clinician's ability to optimize carbon dioxide elimination. We hypothesized that varying the piston position would alter gas displacement and carbon dioxide elimination. METHODS: We conducted an observational study in a tertiary pediatric intensive care unit and a correlated bench study. In the clinical study, 24 patients were ventilated with a SensorMedics 3100A high-frequency oscillator. Transcutaneously measured carbon dioxide (P tCO2) values were documented with the piston-position-and-displacement indicator in left, center, and right positions. In the bench study the oscillator was set and maintained at: mean airway pressure 15 cm H2O, inspiratory time 33% of respiratory-cycle time, bias flow 20 L/min. A pneumotachometer attached to a respiratory mechanics monitor was placed between the ventilator circuit and a test lung. Data were collected with the piston-position-and-displacement indicator at the left, center, and right positions with frequencies of 4–14 Hz and amplitudes of 25–55 cm H2O. Data were collected over a 3-minute time period for each combination of frequency, amplitude, and piston-position-and-displacement-indicator position. We compared the data with repeated-measures analysis of variance. Pairwise comparisons were performed with a 2-tailed Student's t test with Bonferroni correction. RESULTS: Among the 24 patients P tCO2 was significantly associated with the position of the piston (p < 0.007). In the bench study, gas displacement was higher when the piston-position-and-displacement indicator was positioned to the left (than when at the center position) 91.7% of the time (p < 0.0001). When the piston-position-and-displacement indicator was positioned to the right (as compared to the center position), gas displacement was lower 75% of the time (p < 0.0001). CONCLUSION: Adjusting the oscillator piston alters the volume of gas displaced and provides an additional means for titrating carbon dioxide elimination.