Accepted version. Heart & Lung, Vol. 16, No. 6 (November 1987). Publisher Link. © 1987 Elsevier. Used with permission.

NOTICE: this is the author’s version of a work that was accepted for publication in Heart and Lung. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Heart and Lung, [VOL 16, ISSUE 6, (November 1987) Publisher Link.