Physiological responses to spirometer load

Area of Science:

• * Physiology
• * Respiratory System Dynamics
• * Animal Models in Research

Background:

• * The spirometric loading effect, a transient increase in respiratory parameters, is a known phenomenon.
• * Understanding these effects is crucial for accurate physiological measurements and interpreting respiratory control mechanisms.

Purpose of the Study:

• * To quantify the transient effects of spirometry on tidal volume and respiratory rate in decerebrate cats.
• * To investigate the underlying mechanisms, including reflex and chemical factors, contributing to these changes.
• * To observe the impact of spirometry on different breathing patterns.

Main Methods:

• * Experiments conducted on 22 decerebrate cats.
• * Respiration monitored using impedance pneumography.
• * Tidal volume measured using a spirometer at 10-60 minute intervals; 233 spirograms recorded.

Main Results:

• * Significant time-dependent increases in tidal volume (up to 64%) and respiratory rate observed.
• * Instantaneous minute volumes increased up to nearly 400% of control levels.
• * Spirometric loading led to regularization of irregular or periodic breathing patterns (e.g., Biot's breathing).

Conclusions:

• * Spirometry introduces transient perturbations into the respiratory control system.
• * Maximal effects are reached within 80 seconds, involving a combination of vagal afferent reflexes and chemical factors (increased CO2).
• * These findings underscore the importance of considering spirometer-induced effects in respiratory research.