What Is the Potential Role of Transcutaneous Carbon Dioxide in Guiding Acute Noninvasive Ventilation?

Abstract

BACKGROUND: Transcutaneous carbon dioxide (P tcCO 2 ) monitoring is rarely used in the acute hospital setting, where serial samples of arterial blood are instead taken to measure carbon dioxide tension (P aCO 2 ). In this pilot observational study, we assessed the potential of P tcCO 2 monitoring to calculate pH and guide management of acute noninvasive ventilation (NIV). METHODS: Ten subjects with acute hypercapnic respiratory failure were recruited. All had arterial lines placed to guide acute NIV. P tcCO 2 was monitored for 12 h (TOSCA TCM4) and compared with P aCO 2 . Noninvasive transcutaneous pH was determined from P tcCO 2 and calculated bicarbonate and then compared with true arterial pH. Agreements between P CO 2 and pH methods were assessed using Bland-Altman analysis of limits of agreement and Pearson correlation coefficients. Hypothetical adjustments to acute NIV settings were based on transcutaneous data alone and evaluated in comparison with true management. Pain scores for each method were compared using the Wilcoxon signed-rank test. RESULTS: P CO 2 time trends were concordant. Mean P CO 2 bias was ؊2.33 (95% limits of agreement of ؊9.60 to 5.03) mm Hg, and r ‫؍‬ 0.89 (P < .001). Mean pH bias was 0.012 (95% limits of agreement of ؊0.070 to 0.094), and r ‫؍‬ 0.84 (P < .001). Hypothetical clinical decisions based on transcutaneous data alone matched true management on 85% of 34 occasions. Initiation of transcutaneous monitoring was less painful than the arterial equivalent (P ‫؍‬ .008). CONCLUSIONS: This pilot study demonstrates that P tcCO 2 monitoring provides a continuous and reliable trend and also allows pH prediction. This patient-friendly approach is a promising alternative to repeated arterial blood gas sampling in patients requiring NIV for acute hypercapnic respiratory failure.

Transcutaneous Carbon Dioxide Monitoring in Subjects With Acute Respiratory Failure and Severe Hypercapnia

“…In critically ill subjects as Rodriguez et al 16 suggest, transcutaneous arterial carbon dioxide is probably more useful as a trend-monitoring tool to predict changes in P aCO 2 than as a single measurement. In the same way, van Oppen et al 17 in a pilot study demonstrate that P tcCO 2 provides a continuous and reliable tool and also allows pH prediction.…”

What Is the Potential Role of Transcutaneous Carbon Dioxide in Guiding Acute Noninvasive Ventilation?

“…As mentioned by van Oppen et al, 4 further research is necessary to validate the use of the pH algorithm described. What might be interesting to consider is whether treatment of this small number of subjects would have been altered had the authors simply monitored signs and symptoms, as mentioned previously.…”

“…van Oppen et al 4 found that subjects who required NIV preferred transcutaneous to arterial blood gas monitoring. The authors referred to arterial blood gas sampling as being more time-consuming and painful for subjects.…”

“…van Oppen et al 4 should be congratulated for their desire to investigate better methods for monitoring patients with acute hypercapnic respiratory failure. Perhaps if and when the use of this technology and the related pH algorithm is further investigated and when the equipment expense is reduced, more centers providing NIV will see the utility of P tcCO 2 monitoring for managing their patients who require NIV.…”

“…One of the goals of van Oppen et al 4 was to compare pain levels associated with arterial blood gas sampling and transcutaneous monitoring technology. The authors stated that a during a COPD exacerbation, it is necessary to obtain arterial blood samples to measure pH.…”