title: [Physiological factors influencing pulmonary capillary volume and membrane diffusion].
abstract: BACKGROUND
  The lung is subject to many physiological changes during life. The aim of this study was to identify factors that influence gas transfer, which depends on membrane diffusion (Dm) and pulmonary capillary blood volume (Vc).
  
  
  METHODS
  Dm and Vc measurements were performed at rest in 135 healthy patients divided into three groups according to age and after an exercise in 22 non-trained children. Measurements were made using a simultaneous transfer of 2 gases; nitric oxide (NO) and carbon monoxide (CO).
  
  
  RESULTS
  Dm was correlated with height in the adult group and with weight in the elderly group. Vc was not correlated with weight in the three studied groups, but correlated with height in the adult group. Dm and Vc declined with age (p<0.05), For Dm this started at the age of forty whereas a fall in Vc was apparent at sixty. Pulmonary and vascular ageing could explain these results. Sex had no effect on Dm and Vc. Exercise led to a significant rise in Dm and Vc (p<0.05) which was attributed to pulmonary capillary distension and recruitment.
  
  
  CONCLUSIONS
  Knowledge of these physiological changes permits a better understanding of pathological changes.
authors.affiliation: Laboratoire de physiologie et explorations fonctionnelles, EPS Farhat Hached, Sousse, Tunisie. sonia.rouatbi@rns.tn
authors.forename: S
authors.initials: S
authors.lastname: Rouatbi
authors.forename: Y F
authors.initials: YF
authors.lastname: Ouahchi
authors.forename: C
authors.initials: C
authors.lastname: Ben Salah
authors.forename: H
authors.initials: H
authors.lastname: Ben Saad
authors.forename: I
authors.initials: I
authors.lastname: Harrabi
authors.forename: Z
authors.initials: Z
authors.lastname: Tabka
authors.forename: H
authors.initials: H
authors.lastname: Guénard
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001810:Blood Volume; D001827:Body Height / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D002196:Capillaries / Q000502:physiology; D002648:Child; D003430:Cross-Sectional Studies; D005080:Exercise Test; D006801:Humans; D008875:Middle Aged; D011653:Pulmonary Diffusing Capacity