The upper limit of alveolar capillary recruitment in a young man with lung growth impairment

Abstract

T Th he e u up pp pe er r l li im mi it t o of f a al lv ve eo ol la ar r c ca ap pi il ll la ar ry y r re ec cr ru ui it tm me en nt t i in n a a y yo ou un ng g m ma an n w wi it th h l lu un ng g g gr ro ow wt th h i im mp pa ai ir rm me en nt t P.M. Donnelly*, B.V. Daxini**, P.T.P. Bye* ABSTRACT: In order to obtain further insight into the adaptive mechanisms relating to gas exchange in anatomically small lungs, tests of mechanical lung function and gas exchange were made in an active young man, whose lung growth had been severely impaired due to pectus excavatum developed in childhood. We found our patient to have small (total lung capacity, 59% of predicted) but mechanically normal lungs. He had a normal cardiac output, a normal single-breath diffusing capacity (100% pred), and a high diffusion coefficient (148% pred) associated with a high pulmonary capillary blood volume (131% pred) at rest. Pulmonary distensibility (K) and elastic recoil were normal. During steady-state exercise he was unable to recruit further reserves of pulmonary capillaries, but this was not reflected in a plateau for oxygen consumption, which was presumably the result of an increased pulmonary capillary blood flow rather than volume. The recruitment of pulmonary capillary reserves in this young man has enabled him to maintain a normal maximum exercise capacity. In addition, the high stroke volume and a haemoglobin level in the high normal range (176 g·l -1 ) may have maintained his maximal exercise function, despite fewer alveolar units.This study suggests that, contrary to previous findings, loss of a major proportion of lung tissue need not impair exercise capacity. Patients with either small lungs or following pneumonectomy may benefit from physical training sufficient to optimize both an increase in cardiac output and recruitment of their existing alveolar capillary reserves.

Pulmonary capillary recruitment during exercise after detraining in a young man with small lungs

“…He agreed to be restudied at 6, 9 and 11 months after his knee injury. All lung function parameters remained essentially unchanged after the first study at 6 months post-training, at which time both DLCOsb and KCO values averaged 14% lower than previously reported whilst active [1]. Pulmonary capillary blood volume (Vc) and maximal oxygen uptake were reduced by 22 and 21%, respectively.…”

“…In the original report [1], we hypothesized that a period of detraining in this man might reduce his Vc, thus, allowing for DLCO recruitment during exercise; and this has in fact proved to be the case. Twelve months ago, he suffered a knee injury, which has prevented him from playing soccer since that time.…”

“…In a recent case report in the Journal [1], we described the adaptive mechanisms relating to gas exchange during exercise in an active young man with anatomically small lungs, the result of lung growth impairment due to pectus excavatum developed in childhood.…”

Large lungs and growth hormone: an increased alveolar number?

“…Perhaps, the large lungs of swimmers [26][27][28], in contrast to the normal lungs of runners [6,29], really are "built for exercise". In contrast, we have recently described a case of an active young man (with an increased stroke volume, with small thoracic cage, and subsequent restriction of all subdivisions of lung volumes) reaching a plateau of TL,CO,sb recruitment during exercise [30]. His resting KCO was 140 % pred and remained unchanged during exercise.…”

Endothelial progenitors in pulmonary hypertension: new pathophysiology and therapeutic implications: Fig. 1—

“…This is accomplished through recruitment of a large network of capillaries, which are not perfused in basal conditions and form a functional pulmonary vascular reserve [46]. Thus, it is intuitive that rarefaction of the pulmonary capillary network would reduce the pulmonary vascular reserve and increase pulmonary pressures, especially in the case of increased demand, such as during physical efforts [47,48]. This scenario is best represented by the patient with emphysema, in whom chronic hypoxia and loss of septum-associated capillaries lead to PH, which manifests or worsens during exercise.…”