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. 2016:2016:9874150.
doi: 10.1155/2016/9874150. Epub 2016 Sep 5.

Can Transcutaneous CO2 Tension Be Used to Calculate Ventilatory Dead Space? A Pilot Study

Pradeep H Lakshminarayana  1 , Adiba A Geeti  1 , Umer M Darr  2 , David A Kaufman  1
Affiliations

Can Transcutaneous CO2 Tension Be Used to Calculate Ventilatory Dead Space? A Pilot Study

Pradeep H Lakshminarayana et al. Crit Care Res Pract. 2016.

Abstract

Dead space fraction (V d/V t) measurement performed using volumetric capnography requires arterial blood gas (ABG) sampling to estimate the partial pressure of carbon dioxide (PaCO2). In recent years, transcutaneous capnography (PtcCO2) has emerged as a noninvasive method of estimating PaCO2. We hypothesized that PtcCO2 can be used as a substitute for PaCO2 in the calculation of V d/V t. In this prospective pilot comparison study, 30 consecutive postcardiac surgery mechanically ventilated patients had V d/V t calculated separately using volumetric capnography by substituting PtcCO2 for PaCO2. The mean V d/V t calculated using PaCO2 and PtcCO2 was 0.48 ± 0.09 and 0.53 ± 0.08, respectively, with a strong positive correlation between the two methods of calculation (Pearson's correlation = 0.87, p < 0.05). Bland-Altman analysis showed a mean difference of -0.05 (95% CI: -0.01 to -0.09) between the two methods. PtcCO2 measurements can provide a noninvasive means to measure V d/V t, thus accessing important physiologic information and prognostic assessment in patients receiving mechanical ventilation.

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Figures

Figure 1
Figure 1
Scatter plot of V d/V t using PaCO2 against V d/V t using PtcCO2.
Figure 2
Figure 2
Modified Bland-Altman plot of V d/V t(PaCO2) − V d/V t(PtcCO2) against mean of V d/V t(PaCO2) and V d/V t(PtcCO2).
See this image and copyright information in PMC

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