The Science Journal of the American Association for Respiratory Care

2012 OPEN FORUM Abstracts

RELIABILITY OF NASAL CANULA SAMPLING TO DETECT ETCO2 IN THE PRESENCE OF CPAP.

Anamaria Booker, Trista Kallis, Elsie Collado-Koman, John W. Newhart, Richard M. Ford; Respiratory Care, UC San Diego Med Ctr, San Diego, CA

Background: EtCO2 monitoring has become an essential tool in monitoring post-operative patients at risk of developing respiratory depression due to over sedation. Many of these patients have been diagnosed with obstructive sleep apnea pre-operatively and are placed on CPAP using a nasal or face mask after surgery. Our study investigated the reliability of respired CO2 via a sampling cannula in an environment of continuous flow and leaks. Method: Testing was done on healthy subjects. The Carefusion EtCO2 nasal cannula was tested on eight males and eleven females ages 23-53. A 3 minute baseline EtCO2 was determined for each participant. Each participant placed a nasal CPAP mask over the EtCO2 nasal cannula and readings observed on a CPAP of 5 cm H20 for 3 minutes following another 3 minutes trial on a CPAP of 10 cm H20. Subjects were instructed to breathe through their nose. During each three minute trial we documented an average of the lowest and highest EtCO2 readings on each pressure. We then followed the same method using a full-face mask CPAP documenting the average EtCO2 both at 5cm H20 and 10cm H20. Results: Nasal masks on 10 cmH2O had the highest variability (10%) from baseline, followed by full face masks at 10 cmH2O (7%) then nasal masks at 5 cmH2O (5%) and full face masks at 5 cmH2O (4%). Discussion: Based on our testing we feel EtCO2 measurement via a sampling cannula is a valid means of monitoring patients receiving CPAP via nasal or full face mask. The baseline variability may be affected by wash out of respired CO2 at the cannula sampling port and the physiologic impact of CPAP levels. However our intent was to determine if CO2 could be detected for the purpose of monitoring respiratory rate and detection of apnea. Our preliminary results indicate such capabilities are possible. Further testing will be done to compare side stream and mainstream types of monitor, higher pressures, controlled leaks, longer periods of time and comparison of mouth breathers and nose breathers. Sponsored Research - None