Age‐dependent effects of thoracic and capillary blood volume distribution on pulmonary artery pressure and lung diffusing capacity

• Published in: Physiological reports Vol. 6; no. 17; pp. e13834 - n/a
• Main Authors: Coffman, Kirsten E., Boeker, Matthew G., Carlson, Alex R., Johnson, Bruce D.
• Format: Journal Article
• Language: English
• Published: United States John Wiley & Sons, Inc 01.09.2018; John Wiley and Sons Inc
• Subjects: Ageing and Degeneration; Aging; Blood; Carbon monoxide; cardiac output; Cardiovascular Physiology; Echocardiography; Head; Lung; Lungs; Nitric oxide; Older people; Original Research; Physiology; Pressure; Pulmonary arteries; Pulmonary artery; pulmonary smooth muscle tone; pulmonary vascular distensibility; pulmonary vasculature; Sildenafil; Smooth muscle; Thorax; Vasodilation; cardiac output; Aging; pulmonary smooth muscle tone; pulmonary vascular distensibility; pulmonary vasculature
• ISSN: 2051-817X
• DOI: 10.14814/phy2.13834

Aging is associated with pulmonary vascular remodeling and reduced distensibility. We investigated the influence of aging on changes in cardiac output (Q), mean pulmonary artery pressure (mPAP), and lung diffusing capacity in response to alterations in thoracic blood volume. The role of pulmonary smooth muscle tone was also interrogated via pulmonary vasodilation. Nine younger (27 ± 4 years) and nine older (71 ± 4 years) healthy adults reached steady‐state in a Supine (0°), Upright (+20°), or Head‐down (−20°) position in order to alter thoracic blood volume. In each position, echocardiography was performed to calculate mPAP and Q, and lung diffusing capacity for carbon monoxide (DLCO) and nitric oxide (DLNO) was assessed. Next, 100 mg sildenafil was administered to reduce pulmonary smooth muscle tone, after which the protocol was repeated. mPAP (P ≤ 0.029) and Q (P ≤ 0.032) were lower in the Upright versus Supine and Head‐down positions, and mPAP was reduced following sildenafil administration (P = 0.019), in older adults only. SV was lower in the Upright versus Supine and Head‐down positions in both younger (P ≤ 0.008) and older (P ≤ 0.003) adults. DLCO and DLNO were not greatly altered by position changes or sildenafil administration. However, the DLNO/DLCO ratio was lower in the Supine and/or Head‐down positions (P ≤ 0.05), but higher following sildenafil administration (P ≤ 0.007), in both younger and older adults. In conclusion, older adults experience greater cardiopulmonary alterations following thoracic blood volume changes, and pulmonary smooth muscle tone plays a role in resting mPAP in older adults only. Furthermore, mPAP is an important determinant of pulmonary capillary blood volume distribution (DLNO/DLCO), regardless of age. We investigated the influence of aging on changes in cardiac output (Q), mean pulmonary artery pressure (mPAP), and lung diffusing capacity in response to alterations in thoracic blood volume as well as pulmonary vasodilation via sildenafil. We found that older adults experience greater cardiopulmonary alterations following thoracic blood volume changes, and pulmonary smooth muscle tone plays a role in resting mPAP in older adults only. Furthermore, mPAP is an important determinant of pulmonary capillary blood volume distribution (DLNO/DLCO), regardless of age.