title: Effects of lung volume on lung and chest wall mechanics in rats.
abstract: To investigate the effect of lung volume on chest wall and lung mechanics in the rats, we measured the impedance (Z) under closed- and open-chest conditions at various positive end-expiratory pressures (0-0.9 kPa) by using a computer-controlled small-animal ventilator (T. F. Schuessler and J. H. T. Bates. IEEE Trans. Biomed. Eng. 42: 860-866, 1995) that we have developed for determining accurately the respiratory Z in small animals. The Z of total respiratory system and lungs was measured with small-volume oscillations between 0.25 and 9.125 Hz. The measured Z was fitted to a model that featured a constant-phase tissue compartment (with dissipation and elastance characterized by constants G and H, respectively) and a constant airway resistance (Z. Hantos, B. Daroczy, B. Suki, S. Nagy, and J. J. Fredberg. J. Appl. Physiol. 72: 168-178, 1992). We matched the lung volume between the closed- and open-chest conditions by using the quasi-static pressure-volume relationship of the lungs to calculate Z as a function of lung volume. Resistance decreased with lung volume and was not significantly different between total respiratory system and lungs. However, G and H of the respiratory system were significantly higher than those of the lungs. We conclude that chest wall in rats has a significant influence on tissue mechanics of the total respiratory system.
authors.affiliation: Meakins-Christie Laboratories, McGill University, Montreal, Quebec, Canada H2X 2P2.
authors.forename: T
authors.initials: T
authors.lastname: Hirai
authors.forename: K A
authors.initials: KA
authors.lastname: McKeown
authors.forename: R F
authors.initials: RF
authors.lastname: Gomes
authors.forename: J H
authors.initials: JH
authors.lastname: Bates
mesh_terms: D000403:Airway Resistance / Q000502:physiology; D000465:Algorithms; D000818:Animals; D008168:Lung / Q000033:anatomy & histology* / Q000502:physiology; D008176:Lung Volume Measurements; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D015656:Respiratory Mechanics / Q000502:physiology*; D013909:Thorax / Q000502:physiology*