Capnography is a continuous and noninvasive method for carbon dioxide (CO2) measurement, and it has become the standard of care for basic respiratory monitoring for intubated patients in the intensive care unit. In addition, it has been used to adjust ventilatory parameters during mechanical ventilation (MV). However, a substantial debate remains as to whether capnography is useful during the process of weaning and extubation from MV during the postoperative period. Thus, the main objective of this study was to present a new use for time-based capnography data by measuring the end-tidal CO2 pressure ([Formula: see text]), partial pressure of arterial CO2 ([Formula: see text]) and feature extraction of capnogram signals before extubation from MV to evaluate the capnography as a predictor of outcome extubation in infants after cardiac surgery. Altogether, 82 measurements were analysed, 71.9% patients were successfully extubated, and 28.1% met the criteria for extubation failure within 48 h. The ROC-AUC analysis for quantitative measure of the capnogram showed significant differences (p < 0.001) for: expiratory time (0.873), slope of phase III (0.866), slope ratio (0.923) and ascending angle (0.897). In addition, the analysis of [Formula: see text] (0.895) and [Formula: see text] (0.924) obtained 30 min before extubation showed significant differences between groups. The [Formula: see text] mean value for success and failure extubation group was 39.04 mmHg and 46.27 mmHg, respectively. It was also observed that high CO2 values in patients who had returned MV was 82.8  ±  21 mmHg at the time of extubation failure. Thus, [Formula: see text] measurements and analysis of features extracted from a capnogram can differentiate extubation outcomes in infant patients under MV, thereby reducing the physiologic instability caused by failure in this process.

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BackgroundRespiratory monitoring is important after surgery to prevent pulmonary complications. End-tidal carbon dioxide (Petco2) measurement by capnometry is an indirect and noninvasive measurement of Pco2 in blood and is accepted and recognized in critical care.ObjectivesTo determine the correlation and level of agreement between Petco2 and Paco2 in spontaneously breathing children after cardiac surgery and to determine whether Petco2 measured by using tidal volume (Vt-Petco2) or vital capacity (VC-Petco2) shows more or less significant correlation with Paco2.MethodsVt-Petco2 and VC-Petco2 by capnometry and Paco2 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.ResultsA total of 172 Vt-Petco2, VC-Petco2, and Paco2 values from 48 children were analyzed. The overall coefficients of determination were 0.84 (P &lt; .001) for Vt-Petco2 and Paco2 and 0.62 (P = .02) for VC-Petco2 and Paco2. The mean gradient for Paco2 to Petco2 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.ConclusionsIn spontaneously breathing children, Vt-Petco2 provided a more accurate estimate of Paco2 than did VC-Petco2, 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.

The monitoring of carbon dioxide pressure through Capnography has been clinically used as a continuous and non-invasive measurement of alveolar ventilation. The patients with lung disease, respiratory and hemodynamic instability and when in mechanical ventilation have a significant alteration in the waveform of the capnogram. In this study, quantitative analysis between capnographic indices of the patients under prolonged mechanical ventilation were obtained and compared to waveforms of spontaneously breathing patients. The measurements were performed at the 10 th day of invasive mechanical ventilation and 48 hours after tracheal extubation, totalling 52 capnographic curves. PaCO 2 and PetCO 2 measurements maintained a significant correlation in spontaneously breathing patients (r 2 = 0.97, p<0.001) and a weak correlation in patients during prolonged mechanical ventilation (r 2 = 0.86). Four waveform parameters (intermediate slope, alpha angle, beta angle and area ratio) were identified as altered. These altered parameters can provide guidance to physicians about the physiological interpretation of capnograms and clinical decision. Proper interpretation of the capnogram can alert a clinician to important changes in mechanical ventilatory parameters in order to obtain a capnographic wave closest to normal thereby improving the lung function of patients.