RT Journal Article
SR Electronic
T1 Effects of Condensate in the Exhalation Limb of Neonatal Circuits on Airway Pressure During Bubble Continuous Positive Airway Pressure
JF Respiratory Care
FD American Association for Respiratory Care
SP respcare.02322
DO 10.4187/respcare.02322
A1 Tiffany M Youngquist
A1 C Peter Richardson
A1 Robert M DiBlasi
YR 2013
UL http://rc.rcjournal.com/content/early/2013/03/12/respcare.02322.abstract
AB Background Bubble continuous positive airway pressure (B-CPAP) is frequently used in spontaneously breathing infants with lung disease. Often, the B-CPAP systems lack pressure alarms and pressure release valves. We observed a large volume of condensate in the exhalation limb of a patient circuit and conducted a series of experiments to test the hypothesis that accumulated condensate could affect delivered pressures. Methods An anatomically accurate nasal airway model of a preterm infant was attached to a spontaneously breathing lung model. A Fisher & Paykel B-CPAP system was attached to the nasal airway with bi-nasal short prongs and the rate of fluid condensation was measured. Next, tracheal pressures were monitored digitally to detect changes in airway pressure related to condensate accumulation. Measurements were obtained with volumes of 0, 5, 10, 15, and 20 mL of water in the exhalation limb at flow rates of 4, 6, 8, and 10 L/min. Measurements with 20 mL in the exhalation limb were recorded with and without an F&P pop-off valve in the circuit. Results The rate of condensate accumulation was 3.8 mL/hour. At volumes of ≥10 mL, noticeable alterations in the airway pressure waveforms and significant increases in mean tracheal pressure were observed. The pop-off valve effectively attenuated peak tracheal pressures but only decreased mean pressures by 0.5-1.5 cmH2O. Discussion/Conclusion Condensate in the exhalation limb of the patient circuit during B-CPAP can significantly increase pressure delivered to the patient. The back and forth movement of this fluid causes oscillations in airway pressure that are much greater than the oscillations created by gas bubbling out the exhalation tube into the water bath. We recommend continuously monitoring pressure at the nasal airway interface, placing an adjustable pop-off valve in the circuit set to 5 cmH2O above desired mean pressure, and emptying fluid from the exhalation limb every 2-3 hours.