Format

Send to

Choose Destination
J Physiol. 2008 Aug 1;586(15):3675-82. doi: 10.1113/jphysiol.2008.154716. Epub 2008 Jun 19.

Non-invasive prospective targeting of arterial P(CO2) in subjects at rest.

Author information

1
Department of Anaesthesiology, University Health Network, Toronto Canada.

Abstract

Accurate measurements of arterial P(CO(2)) (P(a,CO(2))) currently require blood sampling because the end-tidal P(CO(2)) (P(ET,CO(2))) of the expired gas often does not accurately reflect the mean alveolar P(CO(2)) and P(a,CO(2)). Differences between P(ET,CO(2)) and P(a,CO(2)) result from regional inhomogeneities in perfusion and gas exchange. We hypothesized that breathing via a sequential gas delivery circuit would reduce these inhomogeneities sufficiently to allow accurate prediction of P(a,CO(2)) from P(ET,CO(2)). We tested this hypothesis in five healthy middle-aged men by comparing their P(ET,CO(2)) values with P(a,CO(2)) values at various combinations of P(ET,CO(2)) (between 35 and 50 mmHg), P(O(2)) (between 70 and 300 mmHg), and breathing frequencies (f; between 6 and 24 breaths min(-1)). Once each individual was in a steady state, P(a,CO(2)) was collected in duplicate by consecutive blood samples to assess its repeatability. The difference between P(ET,CO(2)) and average P(a,CO(2)) was 0.5 +/- 1.7 mmHg (P = 0.53; 95% CI -2.8, 3.8 mmHg) whereas the mean difference between the two measurements of P(a,CO(2)) was -0.1 +/- 1.6 mmHg (95% CI -3.7, 2.6 mmHg). Repeated measures ANOVAs revealed no significant differences between P(ET,CO(2)) and P(a,CO(2)) over the ranges of P(O(2)), f and target P(ET,CO(2)). We conclude that when breathing via a sequential gas delivery circuit, P(ET,CO(2)) provides as accurate a measurement of P(a,CO(2)) as the actual analysis of arterial blood.

PMID:
18565992
PMCID:
PMC2538829
DOI:
10.1113/jphysiol.2008.154716
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Wiley Icon for PubMed Central
Loading ...
Support Center