Superiority of transcutaneous CO2 over end-tidal CO2 measurement for monitoring respiratory failure in nonintubated patients: A pilot study

• Published in: Journal of critical care 2016-02, Vol.31 (1), p.150-156
• Main Authors: Lermuzeaux, Mathilde, MD, Meric, Henri, MSc, Sauneuf, Bertrand, MD, Girard, Salomé, MSc, Normand, Hervé, MD, PhD, Lofaso, Frédéric, MD, PhD, Terzi, Nicolas, MD, PhD
• Format: Article
• Language: English
• Subjects: Acute respiratory failure; Aged; Aged, 80 and over; Analysis of Variance; Blood Gas Monitoring, Transcutaneous - methods; Carbon Dioxide - blood; Cognitive science; Cohort Studies; Critical Care; End-tidal CO2; Female; Humanities and Social Sciences; Humans; Intensive care unit; Life Sciences; Male; Middle Aged; Monitoring; Neuroscience; Partial Pressure; Pilot Projects; Prospective Studies; Psychology; Pulmonary Disease, Chronic Obstructive; Respiration; Respiratory Distress Syndrome, Adult - blood; Respiratory Insufficiency - blood; Respiratory Insufficiency - diagnosis; Time Factors; Transcutaneous CO2
• ISSN: 0883-9441; 1557-8615
• DOI: 10.1016/j.jcrc.2015.09.014

Abstract Purpose Arterial blood gas measurement is frequently performed in critically ill patients to diagnose and monitor acute respiratory failure. At a given metabolic rate, carbon dioxide partial pressure (Pa co2 ) is entirely determined by CO2 elimination through ventilation. Transcutaneous partial pressure of carbon dioxide (PtcCO2 ) monitoring permits a noninvasive and continuous estimation of arterial CO2 tension (Pa co2 ). The accuracy of PtcCO2 , however, has not been well studied. To assess the accuracy of different CO2 monitoring methods, we compared PtcCO2 and end-tidal CO2 concentration (EtCO2 ) to Pa co2 measurements in nonintubated intensive care unit (ICU) patients with acute respiratory failure. Methods During a 2-month period, we conducted a prospective observational cohort study in 25 consecutive nonintubated and spontaneously breathing patients admitted to our ICU. Arterial blood gases were measured at study inclusion, 30, 60, and 120 minutes later. At each sampling time, EtCO2 was continuously monitored using a Philips Smart Capnoline Plus, and PtcCO2 was measured using was measured using SenTec device. The aim of the study was to assess agreement between PtcCO2 and Pa co2 and between EtCO2 and Pa co2 in nonintubated ICU patients with acute respiratory failure. Bland-Altman techniques and Pearson correlation coefficients were used. The differences over time (at 30, 60, and 120 minutes) between Pa co2 and EtCO2 and between PtcCO2 and Pa co2 were evaluated using 1-way analysis of variance. Results Transcutaneous partial pressure of carbon dioxide and Pa co2 were well correlated ( R = 0.97), whereas the correlation between EtCO2 and Pa co2 was poor ( R = 0.62) probably due to the presence of an alveolar dead space in a few patients, most notably in the group with chronic obstructive pulmonary disease. The difference over time remained stable for both Pa co2 vs EtCO2 (analysis of variance; P = .88) and Pa co2 vs PtcCO2 ( P = .93). Conclusion We found large differences between EtCO2 and Pa co2 in spontaneously breathing nonintubated ICU patients admitted for acute respiratory failure. Our study argues against the use of EtCO2 monitoring in such patients but raises the possibility that PtcCO2 measurement may provide reasonable estimates of Pa co2.