Low cost of ventilation in the vagotomised alligator ( Alligator mississippiensis )

Abstract Pulmonary ventilation requires energy, but the estimated costs of breathing in reptiles vary from 1 to 30% of resting metabolic rate. The low values have been estimated from changes in oxygen uptake during hypoxia or hypercapnia, but it remains possible that these treatments affected metabo...

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Bibliographic Details
Published in:Respiratory physiology & neurobiology 2007-10, Vol.159 (1), p.28-33
Main Authors: Skovgaard, Nini, Wang, Tobias
Format: Article
Language:English
Subjects:
Alligators and Crocodiles - physiology
American alligator ( Alligator mississippiensis)
Animals
Basal Metabolism - physiology
Biological and medical sciences
Cost of ventilation
Fundamental and applied biological sciences. Psychology
Hypercapnia
Hypercapnia - metabolism
Hypoxia
Hypoxia - metabolism
Medical Education
Medical sciences
Pneumology
Pulmonary Ventilation - physiology
Pulmonary/Respiratory
Reptile
Respiratory system : syndromes and miscellaneous diseases
Vagotomy
Ventilatory response
Vertebrates: respiratory system
Work of Breathing - physiology
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Summary:Abstract Pulmonary ventilation requires energy, but the estimated costs of breathing in reptiles vary from 1 to 30% of resting metabolic rate. The low values have been estimated from changes in oxygen uptake during hypoxia or hypercapnia, but it remains possible that these treatments affected metabolism. We equipped alligators with masks for simultaneous measurements of ventilation and oxygen uptake during hypercapnia, hypoxia and bilateral vagotomy. Hypercapnia and hypoxia caused a marked increase in total ventilation, but oxygen uptake remained unchanged indicating a very low energetic cost of breathing. Upon vagotomy, breathing pattern changed to occasional and exceedingly deep breaths (76.1 ± 11.1 ml kg−1 ) followed by buccal oscillations and shallower breaths (22.2 ± 2.3 ml kg−1 ) interspersed between long non-ventilatory periods. This change in breathing pattern did not affect oxygen uptake. The duration of inspiration increased substantially upon vagotomy, so that inspiratory flow rate did not increase proportionally to tidal volume. These prolonged inspiratory times leads to less flow resistance and may explain that tidal volume could be increased substantially without a measurable energetic cost.
ISSN:1569-9048
1878-1519
DOI:10.1016/j.resp.2007.04.010