2005 OPEN FORUM Abstracts
TRANSCUTANEOUS PCO2 MONITORING IN A VENTILATOR WEANING UNIT
R. Dalbec, R.R.T., S. Batool, M.D., Y. Levin, M.D., A. Riendeau, R.R.T., R.N., D.C. Johnson, M.D. Spaulding Rehabilitation Hospital, Boston, MA.
Background: Patients with respiratory failure are at risk for worse hypercapnia when off the ventilator, as well as during bronchoscopies. End-tidal PCO2 (PetCO2) may not correlate well with arterial PCO2 (PaCO2) in patients with severe lung disease. With the availability of an easy to use device to measure transcutaneous PCO2 (PtcCO2), we wanted to evaluate the utility of monitoring PtcCO2 in patients in our ventilator weaning program.
Methods: PtcCO2 was measured using a CO-OXSYS monitor (Aspen Medical Products, http://www.aspenmp.com/) during ABG draws, bronchoscopies performed on ventilated patients, trach mask trials, and during initial nights off the ventilator in patients in our ventilator weaning program. PetCO2 was measured during tidal breathing and with prolonged exhalation using a NICO monitor (Novametrix Medical System, Inc., Wallingford, CT). Data was collected using a Pocket-Logger (Pace Scientific, www.pace-sci.com), which allows computer download, display, and analysis of results. Results from patients who consented to allow use of their data are included. Bronchoscopy was performed via tracheostomy tube under conscious sedation using fentanyl and midazolam, while the patient was on the ventilator using pressure control mode. Trach mask trials were performed as tolerated by the patient up to the duration specified by the physician.
Results: There was very good correlation between PaCO2 and PtcCO2 with PaCO2-PtcCO2 of -1.6 ± 4.5 (mean ± std dev) and ½PaCO2-PtcCO2½of 3.5 ± 3.2 (n=23). There was more variation of PetCO2 with PaCO2-PetCO2 of 8.0 ± 6.0 with tidal breathing and 4.1 ± 7.0 with prolonged exhalation (n= 21).
n PtcCO2 (baseline) Peak-baseline n (%) > 10 rise
bronchocopy 52 44 ± 7 11.0 ± 5.8 27 (52)
trach mask period 10 47 ± 7 5.3 ± 7.0 2 (20)
1st night off ventilator 9 50 ± 7 10.4 ± 9.3 4 (44)
PtcCO2 often rose during bronchoscopy, and influenced the physician to change ventilator settings in 40% of the bronchoscopies. Some patients had significant changes in PtcCO2 during trach mask and overnight off the ventilator periods.
Conclusions: PtcCO2 correlates very well with PaCO2. PtcCO2 often increases during bronchoscopy while on the ventilator, and monitoring PtcCO2 assists ventilator adjustments. Monitoring PtcCO2 is also helpful to assess patients during initial periods off the ventilator. This abstract is funded by: Aspen Medical Products.