Comparison of the performance of linear resistance and ultrasonic pneumotachometers at rest and during lobeline-induced hyperpnoea.

The paper compares the performance of a Fleisch No. 5 pneumotachometer and two commercial ultrasonic pneumotachometers (BRDL and Spiroson) in assessing ventilatory parameters in healthy Thoroughbred horses at rest and during lobeline-induced hyperpnoea. Results show that ultrasonic flowmeters pose significantly lower resistive loads on the respiratory system during above-rest ventilation than the Fleisch pneumotachometer, while maintaining accurate reading, especially the Spiroson model.

Research Methodology

• The study involved five clinically healthy Thoroughbred horses, which were tested with each of the three types of pneumotachometers (devices used to measure airflow in the lungs).
• The testing was done both at rest and during lobeline-induced hyperpnoea, a condition of rapid or deep breathing triggered by lobeline, a pharmacological agent.
• The researchers measured various aspects such as respiratory airflow, respired gas concentrations, oesophageal pressures, mask system pressures, and arterial blood gases both before and after inducing lobeline-induced hyperpnoea.
• Peak expiratory airflow rates exceeding the stated linear range of the Fleisch pneumotachometer were corrected according to a derived regression equation by determining differential pressure-flow curves in vitro over the range of flows recorded in vivo.

Research Findings

• At rest, all three types of pneumotachometers showed no significant differences in their measurements of the different variables.
• During peak ventilation of lobeline-induced hyperpnoea, mask pressures and end tidal carbon dioxide were significantly higher in the Fleisch system.
• In contrast, respiratory frequency and peak inspired and expired flows tended to be lower with the Fleisch system, though the differences were not statistically significant.
• Despite these variations, the overall measurements of ventilatory mechanics did not show significant differences among the three system types.

Conclusions

• The ultrasonic flowmeters imposed significantly lower resistance loads on the respiratory system during ventilation above resting levels compared to the Fleisch No 5 pneumotachometer.
• The Spiroson flowmeter performed accurately in determining ventilatory mechanics at rest and during lobeline-induced hyperpnoea.