Procedure—During isoflurane anesthesia, 15 pigeons
were allowed to breathe spontaneously (SP group)
and 15 were mechanically ventilated (MV group) by
use of a pressure-limited ventilator. In each group,
cardiopulmonary variables (including end-tidal CO2
concentration [ETCO2]) were measured before (baseline),
during, and after coelioscopy. An arterial blood
sample was collected for blood gas analyses from
each pigeon before coelioscopy and after the procedure,
when the caudal thoracic air sac was still open.
Results—At baseline, hypoventilation was greater in
the SP group than the MV group. Compared with the
SP group values, ETCO2 overestimated PaCO2 to a
greater degree in the MV group. Cardiovascular variables
were not different between groups. After coelioscopy
(when the air sac was open), PaCO2 had
decreased significantly from baseline in the MV group.
In the SP group, hypoventilation worsened despite an
increase in respiratory rate. After coelioscopy, PaO2 in
the SP group had decreased from baseline and was
lower than PaO2 in the MV group; arterial blood pressure
and heart rate in the MV group had decreased from
baseline and were lower than values in the SP group.
Conclusions and Clinical Relevance—In adult
pigeons, controlled ventilation delivered by a pressurelimited
device was not associated with clinically important
adverse cardiopulmonary changes but may be
associated with respiratory alkalosis and cardiovascular
depression when air sac integrity has been disrupted.
(J Am Vet Med Assoc 2005;227:1424–1428)