Abstract
BackgroundIn acute respiratory failure, arterial blood gas analysis (ABG) is used to diagnose hypercapnia. Once non-invasive ventilation (NIV) is initiated, ABG should at least be repeated within 1 h to assess PaCO2 response to treatment in order to help detect NIV failure. The main aim of this study was to assess whether measuring end-tidal CO2 (EtCO2) with a dedicated naso-buccal sensor during NIV could predict PaCO2 variation and/or PaCO2 absolute values. The additional aim was to assess whether active or passive prolonged expiratory maneuvers could improve the agreement between expiratory CO2 and PaCO2.MethodsThis is a prospective study in adult patients suffering from acute hypercapnic respiratory failure (PaCO2 ≥ 45 mmHg) treated with NIV. EtCO2 and expiratory CO2 values during active and passive expiratory maneuvers were measured using a dedicated naso-buccal sensor and compared to concomitant PaCO2 values. The agreement between two consecutive values of EtCO2 (delta EtCO2) and two consecutive values of PaCO2 (delta PaCO2) and between PaCO2 and concomitant expiratory CO2 values was assessed using the Bland and Altman method adjusted for the effects of repeated measurements.ResultsFifty-four datasets from a population of 11 patients (8 COPD and 3 non-COPD patients), were included in the analysis. PaCO2 values ranged from 39 to 80 mmHg, and EtCO2 from 12 to 68 mmHg. In the observed agreement between delta EtCO2 and deltaPaCO2, bias was −0.3 mmHg, and limits of agreement were −17.8 and 17.2 mmHg. In agreement between PaCO2 and EtCO2, bias was 14.7 mmHg, and limits of agreement were −6.6 and 36.1 mmHg. Adding active and passive expiration maneuvers did not improve PaCO2 prediction.ConclusionsDuring NIV delivered for acute hypercapnic respiratory failure, measuring EtCO2 using a dedicating naso-buccal sensor was inaccurate to predict both PaCO2 and PaCO2 variations over time. Active and passive expiration maneuvers did not improve PaCO2 prediction.Trial registrationClinicalTrials.gov: NCT01489150.
Highlights
In acute respiratory failure, arterial blood gas analysis (ABG) is used to diagnose hypercapnia
The main aim of this study was to assess the ability of a dedicated end-tidal CO2 (EtCO2) naso-buccal sensor to predict PaCO2 variations and/or PaCO2 absolute values in hypercapnic patients during non-invasive ventilation (NIV)
Patients Non-intubated patients suffering from hypercapnic (PaCO2 ≥ 45 mmHg) acute respiratory failure, hospitalized in the ICU, equipped with an arterial line and requiring NIV could be included in the study if they had no major hemodynamic instability, no facial lesion preventing the use of the naso-buccal sensor, and no cognitive disability or psychiatric disease liable to interfere with NIV
Summary
Arterial blood gas analysis (ABG) is used to diagnose hypercapnia. The main aim of this study was to assess whether measuring end-tidal CO2 (EtCO2) with a dedicated naso-buccal sensor during NIV could predict PaCO2 variation and/or PaCO2 absolute values. As new specialized naso-buccal EtCO2 sensors have recently been developed to collect expired gas directly at the airway opening, there is an opportunity to use capnometry to monitor capnia during NIV. The main aim of this study was to assess the ability of a dedicated EtCO2 naso-buccal sensor to predict PaCO2 variations and/or PaCO2 absolute values in hypercapnic patients during NIV. The second aim of the study was to assess whether active or passive prolonged expiratory maneuvers could improve the agreement between expiratory CO2 and PaCO2
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