RC time constant of single lung equals that of both lungs together: a study in chronic thromboembolic pulmonary hypertension

• Published in: American journal of physiology. Heart and circulatory physiology Vol. 297; no. 6; pp. H2154 - H2160
• Main Authors: Saouti, N, Westerhof, N, Helderman, F, Marcus, J. T, Stergiopulos, N, Westerhof, B. E, Boonstra, A, Postmus, P. E, Vonk-Noordegraaf, A
• Format: Journal Article
• Language: English
• Published: United States American Physiological Society 01.12.2009
• Subjects: Adult; Aged; Blood Pressure; Cardiac Catheterization; Chronic Disease; Compliance; Female; Heart; Humans; Hypertension, Pulmonary - etiology; Hypertension, Pulmonary - physiopathology; Lung - blood supply; Lungs; Magnetic Resonance Imaging; Male; Middle Aged; Patients; Pulmonary arteries; Pulmonary Artery - physiopathology; Pulmonary Circulation; Thromboembolism - complications; Thromboembolism - physiopathology; Time Factors; Vascular Resistance; Young Adult
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.00694.2009

1 Department of Pulmonary Diseases and 3 Department of Physics and Medical Technology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam; 2 Department of Physiology, VU University, Amsterdam; 5 BMEYE, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; and 4 Laboratory of Hemodynamics and Cardiovascular Technology, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland Submitted July 24, 2009 ; accepted in final form September 29, 2009 The product of resistance, R , and compliance, C ( RC time), of the entire pulmonary circulation is constant. It is unknown if this constancy holds for individual lungs. We determined R and C in individual lungs in chronic thromboembolic pulmonary hypertension (CTEPH) patients where resistances differ between both lungs. Also, the contribution of the proximal pulmonary arteries (PA) to total lung compliance was assessed. Patients ( n = 23) were referred for the evaluation of CTEPH. Pressure was measured by right heart catheterization and flows in the main, left, and right PA by magnetic resonance imaging. Total, left, and right lung resistances were calculated as mean pressure divided by mean flow. Total, left, and right lung compliances were assessed by the pulse pressure method. Proximal compliances were derived from cross-sectional area change A and systolic-diastolic pressure difference P ( A / P) in main, left, and right PA, multiplied by vessel length. The lung with the lowest blood flow was defined "low flow" (LF), the contralateral lung "high flow" (HF). Total resistance was 0.57 ± 0.28 mmHg·s –1 ·ml –1 , and resistances of LF and HF lungs were 1.57 ± 0.2 vs. 1.00 ± 0.1 mmHg·s –1 ·ml –1 , respectively, P < 0.0001. Total compliance was 1.22 ± 1.1 ml/mmHg, and compliances of LF and HF lung were 0.47 ± 0.11 and 0.62 ± 0.12 ml/mmHg, respectively, P = 0.01. Total RC time was 0.49 ± 0.2 s, and RC times for the LF and HF lung were 0.45 ± 0.2 and 0.45 ± 0.1 s, respectively, not different. Proximal arterial compliance, given by the sum of main, right, and left PA compliances, was only 19% of total lung compliance. The RC time of a single lung equals that of both lungs together, and pulmonary arterial compliance comes largely from the distal vasculature. compliance; pulmonary hypertension; resistance and capacitance time; resistance Address for reprint requests and other correspondence: A. Vonk Noordegraaf, Dept. of Pulmonary Diseases, VU Univ. Medical Center, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands (e-mail: a.vonk{at}vumc.nl ).