Fig. 7.
Effects of morphine on respiratory activity. Representative recordings of respiratory variables showed a decrease in respiratory rate from baseline (A) to morphine conditions (B). Morphine significantly decreased respiratory rate (P = 0.021, n = 10; C) and did not significantly change oxygen saturation (P = 0.647, n = 10; D), but decreased significantly heart rate (P = 0.023, n = 10; E). Compared to control group (blue), morphine significantly decreased respiratory rate in the morphine group (red, n = 10; F). Respiratory depression was not dependent on morphine dosage (G; R = 0.04, P = 0.924, n = 10) or age (H; R = 0.30, P = 0.396, n = 10). Data are shown as mean ± 95% CI. *Mean values significantly different with a P < 0.05. Gray area indicates 95% CIs of the linear regressions. ECG = electrocardiogram; O2 sat = blood oxygen saturation; Pco2 = expired carbon dioxide partial pressure.