Measurement of end-tidal carbon dioxide in spontaneously breathing children after cardiac surgery

Respiratory monitoring is important after surgery to prevent pulmonary complications. End-tidal carbon dioxide (Petco(2)) measurement by capnometry is an indirect and noninvasive measurement of Pco(2) in blood and is accepted and recognized in critical care. To determine the correlation and level of agreement between Petco(2) and Paco(2) in spontaneously breathing children after cardiac surgery and to determine whether Petco(2) measured by using tidal volume (Vt-Petco(2)) or vital capacity (VC-Petco(2)) shows more or less significant correlation with Paco(2). Vt-Petco(2) and VC-Petco(2) by capnometry and Paco(2) by blood gas analysis were measured once a day after tracheal extubation. The determination coefficient and degree of bias between the methods were assessed in children with and without supplemental oxygen. A total of 172 Vt-Petco(2), VC-Petco(2), and Paco(2) values from 48 children were analyzed. The overall coefficients of determination were 0.84 (P < .001) for Vt-Petco(2) and Paco(2) and 0.62 (P = .02) for VC-Petco(2) and Paco(2). The mean gradient for Paco(2) to Petco(2) in all groups increased with the increase in supplemental oxygen; the gradient was significantly larger in the groups given 2 to 5 L of oxygen per minute. In spontaneously breathing children, Vt-Petco(2) provided a more accurate estimate of Paco(2) than did VC-Petco(2), especially in children given little or no supplemental oxygen. The difference between the methods was significantly larger in the groups given 2 to 5 L of oxygen per minute.