Isoflurane and ketamine anesthesia have different effects on ventilatory pattern variability in rats

Area of Science:

• Anesthesiology
• Physiology
• Computational Neuroscience

Background:

• Anesthesia profoundly affects physiological processes, including respiratory control.
• Understanding how different anesthetics alter ventilatory pattern variability (VPV) is crucial for patient safety and mechanistic insights.
• Ventilatory patterns exhibit complex linear and nonlinear dynamics that may be differentially modulated by anesthetics.

Purpose of the Study:

• To investigate the distinct impacts of isoflurane and ketamine on ventilatory pattern variability (VPV) in rats.
• To differentiate the effects of these anesthetics on both linear and nonlinear components of breathing dynamics.
• To explore the underlying mechanisms by analyzing surrogate data sets.

Main Methods:

• Adult Sprague-Dawley rats were studied using whole-body plethysmography before, during, and after deep anesthesia.
• Ventilatory pattern variability (VPV) was quantified using a suite of analytical techniques, including surrogate data analysis.
• Analysis focused on metrics such as coefficient of variation, mutual information, sample entropy, and nonlinear complexity index (NLCI).

Main Results:

• Both isoflurane and ketamine decreased VPV, as indicated by the coefficient of variation, despite opposing effects on respiratory rate.
• Mutual information increased, sample entropy decreased, and the nonlinear complexity index (NLCI) increased during anesthesia.
• Surrogate data analysis revealed that isoflurane did not alter mutual information or sample entropy, whereas ketamine significantly changed these metrics, suggesting distinct modulation of linear and nonlinear variability.

Conclusions:

• Isoflurane and ketamine differentially impact ventilatory pattern variability, affecting both linear and nonlinear dynamics.
• The observed changes suggest that separate neural mechanisms underlie the modulation of linear and nonlinear components of breathing under anesthesia.
• These findings contribute to a deeper understanding of anesthetic effects on cardiorespiratory control.