Capnometria com cateter nasal em pacientes com respiraçåo espontânea / Capnometry with nasal prong in patients under spontaneous ventilation

ABSTRACT

Background and Objectives - Different systems have been developed for the evaluation of PETCO2 in patients under sedation without tracheal intubation. The purpose of this study was to evalaute the PETCO2 obtained through a nasal prong and correlate it to the PaCO2 obtained from arterial gasometry. Methods - Thirty patients, age varying between 16 and 78 years, submitted to general anesthesia for abdominal surgery were studied. After extubation, with the patient under spontaneous ventilation, the expired gas was continuously collected through a special nasal prong an PETCO2 was analyzed by an OHMEDA 5.200 capnograph. The PETCO2 was compared with the PaCO2, in thirty simultaneous measurements. In order to evaluate the accuracy of the system, the Pa-ETCO2 gradient was also evaluated. Results - PaCO2 mean values were 36+-7 mmHg (range 28-53 mmHg) and PETCO2 values were 34+-6 mmHg (range 23-47 mmHg), with a good correlation between them (r=0.85, p<0.01). Mean values for Pa-ETCO2 gradient were 2.0+-3.5 mmHg. Although the mean values for PETCO2 and PaCO2 were close, some patients showed an important difference between them. Conclusions - We conclude that the methods is suitable for continuous noninvasive monitoring ofspontaneous ventilation in extubated patients. However, although the correlation between PETCO2 and PaCO2 is good, the method should not be used for predicting of PaCO2 values