End-tidal arterial CO2 partial pressure gradient in patients with severe hypercapnia undergoing noninvasive ventilation

Abstract

Background:Patients with severe hypercapnia represent a particularly serious condition in an emergency department (ED), requiring immediate attention. Noninvasive ventilation (NIV) is an integral part of the treatment for acute respiratory failure. The present study aimed to validate the measurement of end-tidal CO 2 (EtCO 2 ) as a noninvasive technique to evaluate the effectiveness of NIV in acute hypercapnic respiratory failure. Methods: Twenty consecutive patients admitted to the ED with severe dyspnea were enrolled in the study. NIV by means of bilevel positive airway pressure, was applied to the patients simultaneously with standard medical therapy and continued for 12 hours; the arterial blood gases and side-stream nasal/oral EtCO 2 were measured at subsequent times: T0 (admission to the ED), T1h (after 1 hour), T6h (after 6 hours), and T12h (after 12 hours) during NIV treatment. Results: The arterial CO 2 partial pressure (PaCO 2 )-EtCO 2 gradient decreased progressively, reaching at T6h and T12h values lower than baseline (P , 0.001), while arterial pH increased during the observation period (P , 0.001). A positive correlation was found between EtCO 2 and PaCO 2 values (r = 0.89, P , 0.001) at the end of the observation period. Conclusion: In our hypercapnic patients, the effectiveness of the NIV was evidenced by the progressive reduction of the PaCO 2 -EtCO 2 gradient. The measurement of the CO 2 gradient could be a reliable method in monitoring the effectiveness of NIV in acute hypercapnic respiratory failure in the ED.

End-Tidal Carbon Dioxide Pressure Measurement after Prolonged Inspiratory Time Gives a Good Estimation of the Arterial Carbon Dioxide Pressure in Mechanically Ventilated Patients

“…In healthy anaesthetised patients, the monitoring of end-tidal CO 2 pressure (PetCO 2 ) is mandatory even if it underestimates the PaCO 2 , with a gradient around 4.5–13 mm Hg [ 2 ]. Lung diseases are associated with pulmonary heterogeneity, and the PaCO 2 –PetCO 2 gradient rises in unpredictable proportions [ 3 , 4 , 5 , 6 , 7 , 8 ]. Therefore, the PetCO 2 value cannot be taken as a good estimate of alveolar PCO 2 and hence cannot be used as an estimate of PaCO 2 .…”

The association between end-tidal carbon dioxide and arterial partial pressure of carbon dioxide after cardiopulmonary bypass pumping in cyanotic children

“…In some studies, the association between EtCO2 and PaCO2 has been established, but the accuracy of this method is still debated. [4][5][6][7] In a study comparing the relationship between EtCO2 and PaCO2 in the prone and supine positions, it was found that under normal circumstances, EtCO2 is a useful tool for monitoring PaCO2, but its accuracy may decrease when using different surgical techniques and in different positions. 8 Overall, measuring and monitoring EtCO2 is an important aspect of critical patient care.…”