Mechanics of breathing in goats.

Common pulmonary function tests used in man and domestic mammals were adapted to the goat. Requirements for intrathoracic pressure record and pulmonary function investigation were determined. The elastance of the mid-thoracic portion of the oesophagus was measured in 17 healthy goats. The calculated percentage error in identifying the endoesophageal intrathoracic pressure decreased with somatic growth, and was found to be smaller than 2 per cent for adult goats. The location of the oesophageal balloon catheter used to measure the intrathoracic pressure was standardised. The following regression equation calculated between the length of catheter (Lcat) and the thoracic circumference (TC) was found: Lcat (cm) = 6.19 +/- 0.7163 X TC (cm) (R2 = 0.96). The influence of the dead space of a face mask on respiration pattern and arterial blood gas were studied. There were no significant changes in arterial partial pressure of oxygen (PaO2) and carbon dioxide (PaCO2), pHa, breathing frequency and intrathoracic pressures. The influence of head and neck position was investigated. Upper airway resistance (Ruaw), measured with the head in a normal position did not significantly differ from values obtained with the head in a horizontal position. Ruaw measured with the head in a vertical position was considerably increased. Arterial blood gas tension and pulmonary mechanics were measured to assess the reproducibility of pulmonary function measurements. Variability in blood gas tension, tidal volume and minute volume is small. The variability of peak to peak intrathoracic pressure change (max delta Plp), dynamic lung compliance (Cdyn), total pulmonary resistance (RL) and Rt were relatively large.

Effect of vagotomy on respiratory mechanics and gas exchange in the neonatal calf.

The effect of vagotomy on the mechanical and gas exchange properties of the respiratory system was determined in 7 healthy, anesthetized neonatal Holstein calves. A pressure-compensated volume displacement plethysmograph measured the quasi-static pressure-volume (PV) characteristics of the lungs and thoracic cage. Functional residual capacity (FRC) was determined by He equilibration. Lung and chest wall compliances per kilogram of body weight were 2.25 +/- 0.19 ml/cm of H2O/kg and 8.85 +/- 2.44 ml/cm of H2O/kg, respectively. Total lung capacity (TLC) averaged 78.3 +/- 13 ml/kg and FRC was 51 +/- 5% of TLC. The lung PV curve deviated from single exponential behavior below 75% of TLC, indicating airway closure at large lung volumes. Residual volume, which averaged 28.1 +/- 6.0% of TLC, appeared to be determined by airway closure because the thoracic cage was compliant between FRC and residual volume. Vagotomy had no effect on the lung and thoracic cage PV curves, lung volumes, or the alveolar-arterial oxygen difference, but it decreased pulmonary resistance and increased respiratory system conductance and the dead space/tidal volume ratio, indicating dilation of large conducting airways. The calf appears similar to other neonates, in that the thoracic cage is compliant and airway closure occurs at large lung volumes. Both of these factors may predispose the calf to atelectasis.