Anesthetics such as isoflurane adversely affect heart rate. In this study we analysed the interaction behveen heart rhythm and respiration at different concentrations of isoflurane and ventilation rates. In two rats, the electrocardiogram (ECG) and respiratory signals were recorded under the influence of isoflurane. For the assessment of cardiorespiratory coordination, we analysed the phase locking between heart rate, computed from the R-R intervals of body surface ECG, and respiratory rate, computed from impedance changes, using Hilbert transform. The changes in heart rate, percentage of synchronization and duration of synchronized epochs at different isoflurane concentrations and ventilation rates were assessed using linear regression model. From this study it appears that the amount of phase locking between cardiac and respiratory rates increases with the increase in concentration of isoflurane. Heart rate and duration of synchronized epochs increased significantly with the increase in the level of isoflurane concentration while respiratory rate was not significantly affected. Cardiorespiratory coordination also showed a considerable increase at the ventilation rates of 50-55 cpm in both the rats, suggesting that the phase-locking between the cardiac and respiratory oscillators can beincreased by breathing at a particular respiratory frequency.
Biomedical Applications of Micro- and Nanoengineering IV and Complex Systems. Proceedings of SPIE, Vol. 7270 (Melbourne 10-12 December, 2008)