Significance of Pulmonary Elastic and Viscous Resistance in Orthopnea

Journal/Book: Reprinted from CIRCULATION Vol. XV No. 6 June 1957. 1957;

Abstract: By R. M. CHERNIACK M. D. T. E. CUDDY M. D. and J. B. ARMSTRONG M.D. From the Winnipeg General Hospital and the Department of Physiology and Medical Research University of Manitoba Winnipeg. Supported by a grant from the National Research Council of Canada. Drs. Cherniack and Armstrong are Markle Scholars in Medical Science; Dr. Cuddy is a Fellow National Research Council of Canada. The mechanical properties of the lungs were measured in the sitting and supine positions in 5 normal subjects and in 5 patients with orthopnea due to congestive heart failure. The patients had higher elastic and viscous resistances in the sitting position. Recumbency increased both resistances in both groups but there was a disproportionate increase in the viscous resistance of the patients. This increase was most marked in late expiration and early inspiration. The significance of these findings to orthopnea is discussed. SUMMARY The assumption of the supine position resulted in a marked increase in viscous resistance in patients with congestive heart failure. The major part of this increased resistance occurred at the end of expiration and beginning of inspiration when lung volumes were low. As a consequence the work of breathing in patients with congestive heart failure in the supine position was increased by 25 per cent. The dyspnea of recumbency in these patients is tentatively attributed to interference with the patency of the respiratory passages at low levels of lung inflation. schö

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