Oxygen supplementation and cardiac-autonomic modulation in COPD

Study objectives: Patients with COPD have an increased sympathetic modulation and reduced baroreflex sensitivity (BRS). Therefore, we studied the effects of breathing 31% supplemental oxygen (SuppO₂) on autonomic modulation in a group of COPD patients. Design: We measured autonomic modulation before and during the administration of SuppO₂ on 51 patients with COPD using time-frequency analysis of R-R intervals and BP before and after intervention. This was done via a counterbalanced crossover design. The BRS index was determined using the sequence method. Results: Significant differences were seen in oxygen saturation levels following breathing with SuppO₂ ([mean ± SD] 96.4 ± 1.5%) when compared to those seen after breathing with compressed air (CA) (92.8 ± 2.9%; p < 0.0001). Significant increases were seen in the natural log-transformed high-frequency modulation (HFln) (SuppO₂, 10.8 ± 1.3 natural logarithm [ln] ms²/Hz; CA, 10.6 ± 1.3 ln ms²/Hz; p < 0.028) and BRS (SuppO₂, 3.3 ± 2.2 ms/mm Hg; CA, 2.8 ± 1.8 ms/mm Hg) following the supplemental oxygen treatment (p < 0.015). The low-frequency/high-frequency ratio of heart rate variability revealed significant differences between the two treatments (SuppO₂, 2.7 ± 1.2; CA, 3.1 ± 1.3; p < 0.008). The analysis of BP variability data revealed significant decreases in the HFln (CA, 6.9 ± 1.0 mm Hg²/Hz; SuppO₂, 6.5 ± 1.2 mm Hg²/Hz; p < 0.0001). Hemodynamic data also revealed a decrease in mean heart rate after breathing SuppO₂ compared with that after breathing CA (CA, 87.3 ± 13.3 beats/min; SuppO₂, 85.0 ± 12.4 beats/min; p < 0.0004). The arterial pulse pressure significantly decreased when breathing SuppO₂ compared with that when breathing CA (CA, 57.2 ± 13.5 mm Hg; SuppO₂, 53.3 ± 13.0 mm Hg; p < 0.0023). Conclusion: Oxygen supplementation in COPD patients significantly and favorably alters autonomic modulation.