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A Journal on Diseases of the Respiratory System

Official Journal of the Italian Society of Thoracic Endoscopy
Indexed/Abstracted in: EMBASE, Scopus, Emerging Sources Citation Index




Minerva Pneumologica 2017 December;56(4):249-53

DOI: 10.23736/S0026-4954.17.01799-0


language: English

Flow and volume dependence of resistive pressures dissipation in the respiratory system

Alessandro RUBINI

Section of Physiology, Department of Biomedical Sciences, University of Padua, Padua, Italy


An inspiratory driving pressure must be applied to the respiratory system to inflate airflow from the external ambient to the alveolar space. This pressure is dissipated as heat after the inflation, and allows to win two resistive components named “ohmic” and visco-elastic resistances. The first depends on the frictional forces opposing airflow in the airway, while the second is exerted by respiratory tissue resistance to deformation during inflation. Both of them are here described. Experiments in animals and humans showed that both the resistances exhibit flow as well as volume dependence. The “ohmic” resistance increases with increasing values of flow rate mostly because of increased turbulence in the airway, and decreases with lung volumes increments. This decrement happens because lung inflation increases the tensile stress on the bronchial walls causing bronchodilation. On the contrary, the visco-elastic component decreases with increasing values of flow rate and increases with increments in lung volume. The exact mechanisms are still under debate, but these findings probably depend on the effects of the flow and volume changes on the physical-chemical characteristics of the lung tissue, on the network of the fibrous elements in the alveolar septa, and on interstitial fluid dynamics. The combined effects of volume and flow changes are reviewed, together with some energetic aspects. The consequences during quiet breathing at rest and in muscular exercise hyperventilation are described.

KEY WORDS: Respiratory mechanics - Airway resistance - Pulmonary medicine

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Publication History

Issue published online: October 20, 2017
Manuscript accepted: May 23, 2017
Manuscript received: May 15, 2017

Cite this article as

Rubini A. Flow and volume dependence of resistive pressures dissipation in the respiratory system. Minerva Pneumol 2017;56:249-53. DOI: 10.23736/S0026-4954.17.01799-0

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