Noninvasive monitoring of end-tidal CO2 via nasal cannulas in spontaneously breathing children during the perioperative period

Abstract

Objective: To determine the correlation between end-tidal CO2 and Paco2 values measured via nasal cannulas in spontaneously breathing children during the perioperative period. Design: Prospective evaluation. Setting: Pediatric intensive/intermediate care unit in a tertiary care referral center. Patients: Thirty postoperative surgical and trauma patients aged ≤18 yrs (average age 7.8 yrs [range 6 months to 16 yrs] and average weight 28.3 kg (range 8.5 to 69). Measurements and Main Results: Spontaneously breathing, nonintubated patients with an arterial cannula in place were selected for study. End-tidal CO2 was sampled from nasal cannulas by a sidestream aspirator and was estimated by infrared spectroscopy. The difference between Paco2 and end-tidal CO2 was compared using linear regression analysis. A total of 55 blood gas measurements were obtained on the 30 patients. The Paco2 to end-tidal CO2 gradient was ≤4 torr in 54 of the 55 samples. The mean Paco2 was 39.5 ± 3.3 torr (5.27 ± 0.44 kPa) with a mean end-tidal CO2 value of 39.7 ± 3.8 torr (5.29 ± 0.51 kPa). Linear regression analysis of arterial vs. end-tidal CO2 yielded a slope of 0.992 andp= .0001. Conclusions: End-tidal CO2 measurement by infrared spectroscopy provided an accurate estimation of Paco2 in this patient population. Its use may limit the need for invasive monitoring and/or repeated arterial blood gas analysis. (Crit Care Med 1994; 22:1805–1808)