ISSN:
1741-0444
Keywords:
Alveolar gas exchange
;
Breath
;
Gas analyser
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
Abstract The O2-paramagnetic or polarographic and CO2-infra-red expired gas analyser have a response delay which results in an underestimation in breath-by-breath $$\dot vO_2 $$ and $$\dot vCO_2 $$ calculations. In this study, correction for this delay has been made. After measuring the step response of the O2-polarographic and CO2-infra-red analyser, the damping factor and the natural angular frequency were determined as well as the time constant, assuming the response was a first-order one. $$\dot vO_2 $$ and $$\dot vCO_2 $$ were calculated when the response of the analyser was corrected for the first- and second-order responses using the inverse Laplace transform. For the uncorrected $$\dot vO_2 $$ and $$\dot vCO_2 $$ , values from the breath-by-breath method were 27·5 and 18·1 per cent systematically underestimated (p〈0·001) compared with those of the Douglas bag method. When correction for the first-order response was made, values of the breath-by-breath method became equivalent to those of the Douglas bag method for $$\dot vCO_2 $$ whereas there was still a 17·5 per cent systematic underestimation (p〈0·001) for $$\dot vO_2 $$ . The correction for the second-order response gave equivalence and significant correlation (p〈0·001) between the values of both methods for $$\dot vO_2 $$ and $$\dot vCO_2 $$ . These results might indicate that breath-by-breath measurement of alveolar gas exchange with a slow-response gas analyser is valid when a second-order response delay correction is used.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02442842
Permalink