Gas exchange variables were measured in unanaesthetized domestic geese fitted with rubber facemasks and indwelling air-sac and arterial catheters. The results were analysed on the basis of functional models.

  1. Ventilation was characterized by low frequency (8·4 min−1) and high tidal volume (29·3 ml kg−1).

  2. Average values (± S.E.) of arterial blood variables were as follows: kPa, pH = 7·52 ± 0·01. Body temperature was 41·4 ± 0·2°C.

  3. The gas exchange ratio (calculated with reference to inspired gas) of caudal air sacs (average 1·09) was higher, and that of cranial air sacs (0·73) lower, than that of mixed-expired (0·82) or end-expired gas (0·78). This pattern can be explained by a higher effective ventilation/perfusion ratio in the neopulmo than in the paleopulmo.

  4. During inspiration, the neopulmo was estimated to contribute about 7% to the overall inspiratory O2 uptake, and about 18% to the CO2 output. Total inspiratory gas exchange was twice that during expiration.

  5. Arterial ⁠, was close to, but lower than, the partial pressure in cranial air sacs and in end-expired gas. This can be explained on the basis of a crosscurrent gas exchange system with unequal distribution of ventilation to perfusion between functional compartments.

Keywords:
air sacs, birds, blood gases, diffusing capacity, parabronchial gas exchange, respiratory air flow
© 1989 by Company of Biologists
1989
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