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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 2013 June-September;52(2-3):123-8
Measurements of pressure-volume curves by constant low inflation flow in the rat: effects of body posture
Rubini A. 1, Bosco G. 1, Catena V. 2, Del Monte D. 2
1 Section of Physiology Department of Biomedical Sciences University of Padua, Padua, Italy;
2 Department of Emergency and Intensive Care ULSS 2, Feltre, Belluno, Italy
Aim: The aim of this paper was to define the effects of body position, i.e. head up and down tilting, on the quasi-static respiratory system pressure-volume curve by means of constant and low flow rate inflations.
Methods: During constant and low rate inflation flow, the resistive pressure of the respiratory system may be considered practically negligible, so that airway pressure measurement allows to record quasi-static pressure-volume curve of the system. We continuously recorded pressure-volume curves in the anaesthetised paralysed rat in the supine, 30 degrees head-down and 30 degrees head-up positions.
Results: Pressure-volume mean curve significantly shifted toward the pressure axis in the head-down position, and toward the volume axis in the head-up position, indicating that changes in diaphgram displacement due to gravity force affect respiratory system elastic properties. The effects were observed on the entire range of the tested inflation volumes, which reached values about double with respect to the physiological rat’s tidal volume. The gravitational effect of head-up tilting were shown to increase with inflation volume increment, while the same effect was not observed in head-down tilting.
Conclusion: Over the entire volume range we tested, mean respiratory system compliance values decreased in the head-down and increased in the head-up positions, respectively.