Poincaré plots applied to analysis of breathing pattern after lung injury

Lung injury alters breathing patterns. We hypothesized that analysis of pattern variability would provide insight into mechanisms responsible for altered ventilatory control. Adult male Sprague‐Dawley rats received intratracheal injections of either bleomycin (BM; 1 unit in 40μl PBS) or PBS (40μl). One week after injection, baseline breathing (FiO 2 =0.21) was recorded in unanesthetized animals using whole‐body plethysmography (>5 min sampling at 300 Hz). Breath‐to‐breath variability of expiratory time (T E ) was assessed by Poincaré distribution of T E for breath n plotted against n+1. Plots revealed complex patterning in both groups of animals; however, movement of the centroid of the distribution over 15 breath intervals revealed multiple attractors or domains of stability in BM but not saline‐treated animals. Within a domain of stability, breath‐to‐breath variability for T E may be comparable for both BM‐injected and control animals. We conclude that the different domains of stability with locally regular breath‐to‐breath variability indicate multiple states of pattern formation for the lung injured but not control animals. Supported by: VA Research Service, HL063463 , HL25830, HL080318