Regional pulmonary function by lobar spirometry in unanesthetized sheep.

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Abstract
The sheep has advantages as a preparation for lobar spirometry because of the tracheal origin of its right apical lobar bronchus, which allows easy intubation without anesthesia. The lobar ventilation fraction, 100 x Ve (lobe)/Ve (total), was 9.8% [plus or minus]5.8 sd in 8 unanesthetized sheep and was stable over a period of 3 hr. Lobar and total ventilation increased proportionately during either thermal polypnea or hyperventilation due to CO2 mixtures. When the rest of the lung inspired against a negative pressure, the lobar ventilation fraction increased significantly, from 6.7 to 13.8% (P = 0.02) in 4 sheep. By contrast, acute changes in lobar PaO2 and PaCO2, had no significant effect. Systemic effects of these changes were small. Both ventilation of the lobe with nitrogen and local alveolar hypoventilation appeared to shift blood flow away from the lobe.