Airway humidification during high-frequency percussive ventilation.
BACKGROUND
We were concerned about the risk of inadequate humidification during high-frequency percussive ventilation (HFPV).


METHODS
We studied 5 humidifiers during HFPV with a lung model, at bias gas flows of 10 L/min, 30 L/min, and 50 L/min, and compared the results to those from a comparator ventilator/humidifier setup and to the minimum temperature (30 degrees C) and humidity (30 mg/L) [corrected] recommended by the American Association for Respiratory Care, at both regular room temperature and a high ambient temperature. Temperature was measured at the humidifier outflow point and at the artificial carina. Humidity was measured at the artificial carina.


RESULTS
Of the 7 HFPV/humidifier combinations, 2 (the MR850 at a bias flow of 50 L/min, and the ConchaTherm Hi-Flow with VDR nebulizer) provided a carinal temperature equivalent to the comparator setup at room temperature, whereas one HFPV/humidifier combination (the ConchaTherm Hi-Flow with modified programming, at bias flows of 30 L/min and 50 L/min) provided a higher carinal temperature. At high ambient temperature, all of the setups delivered lower carinal temperature than the comparator setup. Only 2 setups (the ConchaTherm with modified programming at a bias flow of 50 L/min, and the ConchaTherm Hi-Flow with VDR nebulizer) provided carinal humidification equivalent to the comparator setup, without regard to ambient temperature; the other humidifiers were less effective. The ConchaTherm with modified programming, and the ConchaTherm with the VDR nebulizer provided the most consistent humidification.


CONCLUSIONS
HFPV's distinctive gas-flow mechanism may impair gas heating and humidification, so all humidification systems should be tested with HFPV prior to clinical use.
Allan
Patrick F
PF
Pulmonary Service, Landstuhl Regional Medical Center, Germany. patrick.allan@amedd.army.mil
Hollingsworth
Michael J
MJ
Maniere
Gordon C
GC
Rakofsky
Anthony K
AK
Chung
Kevin K
KK
Naworol
Gregory A
GA
Ward
John A
JA
Perello
Michelle
M
Morris
Michael J
MJ
D004867:Equipment Design; D006612:High-Frequency Ventilation / Q000295:instrumentation*; D006813:Humidity; D016014:Linear Models; D013696:Temperature