A comparison of transcutaneous end-tidal and arterial measurements of carbon dioxide during general anaesthesia.
A randomized, prospective study was performed to evaluate the accuracy of a new transcutaneous carbon dioxide (CO2) monitor (Fastrac) during general anaesthesia. Twenty-two adult patients undergoing elective surgery were subjected to three different levels of minute ventilation by varying their respiratory rates in a randomized cross-over design. Simultaneous measurements of transcutaneous CO2 (PTCCO2) and arterial CO2 (PaCO2) were obtained at three levels of minute ventilation (low, medium and high). End-tidal CO2 (PETCO2) values were also recorded from a mass spectrometer (SARA) at each time period. A total of 66 data sets with PaCO2 ranging from 28-62 mmHg were analyzed. The PTCCO2 values demonstrated a high degree of correlation with PaCO2 over the range of minute ventilation (y = 0.904x + 6.36, r = 0.92, P less than 0.001). The PETCO2 measurement also demonstrated a generally good correlation with PaCO2 (y = 0.62x + 9.21, r = 0.89, and P less than 0.01). However, the PETCO2-PaCO2 gradients (mean 7.0 +/- 3.1 mmHg) were greater than the PTCCO2-PaCO2 gradients (mean 2.3 +/- 2.4 mmHg) at all three levels of minute ventilation (P less than 0.05). These differences were greatest when PaCO2 was in the high range (48-60 mmHg). We conclude that the new Fastrac CO2 monitor is accurate for monitoring carbon dioxide levels during general anaesthesia. The new transcutaneous devices provide an effective method for non-invasive monitoring of CO2 in situations where continuous, precise control of CO2 levels is desired.
Reid
C W
CW
Department of Anaesthesia, Ottawa General Hospital Ontario.
Martineau
R J
RJ
Miller
D R
DR
Hull
K A
KA
Baines
J
J
Sullivan
P J
PJ
D000328:Adult; D000768:Anesthesia, General; D002245:Carbon Dioxide / Q000032:analysis* / Q000097:blood; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000295:instrumentation / Q000379:methods*; D010313:Partial Pressure; D011446:Prospective Studies; D013514:Surgical Procedures, Operative
D002245:Carbon Dioxide