Regional distribution of pulmonary ventilation and perfusion in elderly subjects

Abstract

A B S T R A C T Using radioactive xenon, we measured the regional distribution of pulmonary ventilation and blood flow in six normal men, whose ages ranged between 65 and 75 yr. The measurements were made in the standing position. The static volume-pressure relation of the lungs was also measured in five of the subjects. The results indicate that by comparison with normal young men: (a) Blood flow to the upper lung zones was increased, although it still remained predominant in the lower zones. (b) Ventilation distribution during a vital capacity inspiration was similar to that seen in young subjects. (c) In five of the six elderly subjects, however, the distribution of ventilation in the resting tidal volume range was not preferential to the lower zones as it was in young men. This was probably caused by airway closure in the lower lung zones. The elderly subjects thus exhibit during normal tidal volume breathing a ventilation distribution pattern similar to that observed in young subjects when breathing at low lung volumes, i.e., near residual volume. This difference is probably due to the combined effect of the loss in elastic recoil of the lungs observed in the elderly subjects and of a decreased resistance to collapse of the aged airways. These findings suggest that in the elderly subjects there is a significant regional ventilation-perfusion impairment during quiet breathing, which may explain in part Dr. Holland's present address is Cardio-Pulmonary Laboratory, Dalhousie University, Halifax, Canada. Address requests for reprints to Dr.

A Novel Interpretation of Closing Volume Based on Single-Breath Nitrogen Washout Curve Simulation

“…This result can be mathematically interpreted as an enhancement of gravity effect in the present model and consistent with the positive correlation of CV and age [3,20]. We have modeled SBNW under the presumption that the expiratory flow rate is less than 0.5 l/s.…”

“…In 1967, Dollfuss and Milic-Emili proposed a hypothesis that phase IV was due to airway closure in a dependent zone and named the volume fraction of phase IV to the vital capacity "closing volume" (CV) [2]. Furthermore, they reported a positive correlation of CV to age [3] and to smoking [4]. They speculated that small airways in aged people and in smokers were closed earlier than those in normal subjects and proposed that the measurement of CV was a simple and sensitive test for the early detection of small airway diseases [4].…”

Diagnostic value of serum angiotensin converting enzyme activity in lung diseases.

“…Increased closure of the dependent small airways in the tidal volume range, with a subsequent fall in the oxygen tension of these alveoli, is a wellknown concomitant of increasing age (Terman and Newton, 1964;Holland et al, 1968).…”

Pulmonary gas exchange in elderly subjects

“…Changes in body position induce alterations in Pa,O 2 , due to changes in the V'A/Q' distribution partially linked to the direct effect of gravity [15], but also to changes in lung volume and, therefore, closing volume [16]. In young subjects, the distribution of V'A/Q' is less heterogeneous in a supine than in an erect posture, as in older subjects this phenomenon is hindered by the effect of airway closure in the dependent part of the lung, decreasing V'A/Q' values.…”