title: Exponential analysis of the pressure-volume characteristics of ovine lungs.
abstract: Static pressure-volume curves were generated from data obtained from 18 normal anaesthetized adult sheep. Lung volumes were determined by helium dilution. An exponential curve of the form V = Vmax - Ae-KP was fitted to the pressure-volume data from each sheep where P is the static recoil pressure, Vmax represents the volume asymptote, A is the difference between Vmax and the intercept on the volume axis and K defines the slope and hence the shape of the P-V curve. Quality of fit of the data was assessed visually, by means of a sign test and a runs test and by the coefficient of determination (r2). Exponential equations were found to adequately describe the shape of the pressure-volume curve in sheep. The exponent K was not correlated with effective alveolar volume (VAeff) (rs = 0.183; P > 0.05). Static lung compliance was determined over a volume range from the end-expiratory level (VEEL) to VEEL plus 400 ml. Measurements of static lung compliance were significantly correlated with measurements of effective alveolar volume (VAeff) (rs = 0.505; P < 0.025). In the ovine, the exponent K, an index of distensibility, is independent of lung volume and offers a means of assessing lung distensibility in this species.
authors.affiliation: Royal (Dick) School of Veterinary Studies, Veterinary Field Station, Roslin, Midlothian, UK.
authors.forename: D D
authors.initials: DD
authors.lastname: Collie
authors.forename: N J
authors.initials: NJ
authors.lastname: Watt
authors.forename: P M
authors.initials: PM
authors.lastname: Warren
authors.forename: I
authors.initials: I
authors.lastname: Begara
authors.forename: L
authors.initials: L
authors.lastname: Luján
mesh_terms: D000399:Air Pressure; D000758:Anesthesia; D000818:Animals; D005260:Female; D008168:Lung / Q000033:anatomy & histology / Q000502:physiology*; D008170:Lung Compliance / Q000502:physiology; D008176:Lung Volume Measurements; D015656:Respiratory Mechanics / Q000502:physiology; D012756:Sheep / Q000502:physiology*; D014109:Total Lung Capacity / Q000502:physiology