Transcutaneous monitoring as a replacement for arterial PCO₂ monitoring during nocturnal non-invasive ventilation☆

Summary 

Background

Continuous, non-invasive assessment of alveolar ventilation achieved by transcutaneous PCO₂ (PtcCO₂) monitoring is clearly superior to intermittent, invasive blood gas analyses in patients receiving nocturnal non-invasive positive pressure ventilation (NPPV), but the reliability and accuracy of PtcCO₂-monitoring is still disputed. The present study was aimed at investigating the capability of modern PtcCO₂-monitoring to reliably assess alveolar ventilation during nocturnal NPPV.

Methods

Capillary blood gas measurements (11pm, 2am, 5am and 7am) and 8 h of continuous PtcCO₂-monitoring using three of the latest generation devices (SenTec Digital Monitor, Radiometer TCM4-TINA and Radiometer TOSCA500) were performed during polysomnography-proven sleep studies in 24 patients receiving NPPV (15 with COPD, 9 with restrictive disorders).

Results

The technical calibration drift for SenTec DM, TCM4-TINA and TOSCA500 was 0.1, −0.4 and −0.5 mmHg/h, respectively. Bland-Altman method comparison of PaCO₂/drift-uncorrected PtcCO₂ revealed a mean bias (limits of agreement) of 1.0 (−4.7 to 6.7), −1.5 (−15.6 to 12.5) and 0.8 (−6.8 to 8.3) mmHg, respectively. Continuous overnight PtcCO₂-monitoring detected variations in alveolar ventilation, with median ranges of 12.3 (10.7–14.5) mmHg for SenTec DM, 14.5 (12.5–17.0) mmHg for TCM4-TINA and 11.5 (11.0–13.0) mmHg for TOSCA500 (RM-ANOVA, p < 0.001). The four capillary PaCO₂ values ranged by a median of 6.3 (4.7–9.7) mmHg.

Conclusions

Modern PtcCO₂-monitoring is reliable, accurate and robust. Since PtcCO₂-monitoring is also non-invasive, does not disrupt sleep quality and provides a more complete picture of alveolar ventilation than intermittent capillary PaCO₂, PtcCO₂-monitoring should become the preferred technique for assessing alveolar ventilation during nocturnal NPPV.

Trial Registration: DRKS00000433 at http://apps.who.int/trialsearch/default.aspx.

Keywords: Alveolar ventilation, Carbon dioxide, Monitoring, Nocturnal ventilation, Sleep, Transcutaneous pressure of carbone dioxid

Abbreviations: ABG, arterial blood gas analysis, BE, base excess, BMI, body mass index, CI, confidence interval, COPD, chronic obstructive pulmonary disease, CO₂, carbon dioxide, EPAP, expiratory positive airway pressure, FEV₁, forced expiratory volume in 1 s, FVC, forced vital capacity, HCO^-₃, standard bicarbonate, HRF, hypercapnic respiratory failure, IPAP, inspiratory positive airway pressure, LTOT, long-term oxygen therapy, min, minutes, NF, normality test failed, NREM, non-rapid eye movement sleep, NPPV, non-invasive positive pressure ventilation, PCO₂, partial pressure of carbon dioxide, PaCO₂, arterial partial pressure of carbon dioxide, PetCO₂, end-tidal partial pressure of carbon dioxide, PtcCO₂, transcutaneous partial pressure of carbon dioxide, PaO₂, partial pressure of oxygen, REM, rapid eye movement sleep, RM-ANOVA, Repeated Measures Analysis of Variance, RR_set, preset respiratory rate, RV, residual volume, SaO₂, arterial oxygen saturation, SenTec DM, SenTec Digital Monitor, SD, standard deviation, TLC, total lung capacity, TST, total sleep time