HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Cole, R.P. Search for Related Content PubMed PubMed Citation Articles by Cole, R.P.

Carbon dioxide production during acetazolamide and medroxyprogesterone treatment

Dept of Medicine, Columbia University, New York, USA

To the Editor:

Wagenaar et al. 1 report improvement in gas exchange and increased minute ventilation (V'_E) in patients with stable, moderately severe chronic obstructive pulmonary disease receiving treatment with acetazolamide and medroxyprogesterone. They estimate a baseline carbon dioxide (CO₂) production rate of 400 mL·min^–1 from the placebo values for CO₂ arterial tension (P_a,CO2) of 6.5 kPa or 49 mmHg and V'_E of 9.3 L min^–1. Assuming that P_a,CO2 can be substituted for alveolar carbon dioxide tension (P_CO2), one can calculate the dead space to tidal volume ratio (V_D:V_T) using the standard formula 2:

(001)

where V'_CO2 is carbon dioxide production.

The V_D:V_T calculates to 0.24, a surprisingly low value in patients with advanced airways obstruction. If this value is modified by the increased V_T during acetazolamide and medroxyprogesterone treatment and one calculates V'_CO2 (P_a,CO2 of 5.3 kPa or 40 mmHg and V'_E of 11.2 L·min^–1), V'_CO2 is 412 mL·min^–1, not the 450 mL·min^–1 the authors state.

If medroxyprogesterone therapy was associated with a substantial increase in metabolic carbon dioxide production, then an increase in total ventilation would be necessary to prevent an increase in alveolar and arterial carbon dioxide tension production, in part defeating the purpose of the use of respiratory stimulants in this situation.

References

1. Wagenaar M, Je Vos P, Heijdra YF, Teppema LJ, Folgering HTM. Combined treatment with acetazolamide and medroxyprogesterone in chronic obstructive pulmonary disease patients. Eur Respir J 2002;20:1130–1137.[Abstract/Free Full Text]
2. Staub NC. Basic Respiratory PhysiologyNew York, Churchill Livingston, 1991; pp. 52–53.

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Cole, R.P. Search for Related Content PubMed PubMed Citation Articles by Cole, R.P.