Measurement of ventilatory responses in the toad Bufo marinus: A comparison of pneumotachography and buccal pressures

Determination of pulmonary ventilation in anuran amphibians is usually accomplished from recordings of buccal pressure or by pneumotachography. Considering the well described changes in ventilatory pattern during increased respiratory drive, it is pertinent to determine whether the two methods produce comparable ventilatory responses. To resolve this question, a toad was equipped with both a buccal cannula and a pneumotachograph enabling a direct comparison of the two methods. While the two methods result in similar determinations of the overall ventilatory response to hypoxia, there was a poor correlation between buccal pressure and exhaled volume for individual breaths.