This Article  • References  • Full text PDF  • Send to a friend  • Save in My Folder  • Save to citation manager  • Permissions  Citing Articles  • Contact me when this article is cited  Related Content  • Similar articles in JAMA  Social Bookmarking   What's this?

Akhil Bidani, MD; Victor J. Cardenas, Jr, MD
University of Texas Medical Branch Galveston

JAMA. 1995;273(10):775.

	Since this article does not have an abstract, we have provided the first 150 words of the full text PDF and any section headings.

In Reply.

—We appreciate Dr Helmholz's comments regarding our article on permissive hypercapnia. Regarding his critique of equation 1, we concur that the alveolar air equation as delineated in his letter is the more accurate form.¹ However, for purposes of clarity and simplicity, we elected to use the more familiar clinical form of the alveolar gas equation as a reasonable approximation.

Regarding equation 2, we disagree with Helmholz's assertion that PACO₂ is independent of barometric pressure. The relationship between volume and pressure is adjusted by a constant, K, whose value is valid only under a set level of temperature and pressure. In his example, K=0.863=(TB/TS) (PB)/(1000 mL/L), where TB is body temperature (310°K), Ts is standard temperature (273°K), and PB is standard barometric pressure (760 mm Hg).² Therefore, changes in these conditions alter the value of K and affect partial pressure as well as gas volumes. The . . . [Full Text PDF of this Article]

CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter     What's this?