Oxygen Supplementation and Cardiac-Autonomic Modulation in COPD

Patients with COPD have an increasedsympathetic modulation and reduced baroreflex sensitivity (BRS).Therefore, we studied the effects of breathing 31% supplemental oxygen(SuppO2) on autonomic modulation in a group of COPDpatients. We measured autonomic modulationbefore and during the administration of SuppO2 on 51patients with COPD using time-frequency analysis of R-R intervals and , BP before and after intervention. This was done via a counterbalancedcrossover design. The BRS index was determined using the sequencemethod. Significant differences were seen inoxygen saturation levels following breathing with SuppO2([mean ± SD] 96.4 ± 1.5%) when compared to those seen afterbreathing with compressed air (CA) (92.8 ± 2.9%; p < 0.0001).Significant increases were seen in the natural log-transformedhigh-frequency modulation (HFln) (SuppO2, 10.8 ± 1.3natural logarithm [ln] ms2/Hz; CA, 10.6 ± 1.3 lnms2/Hz; p < 0.028) and BRS (SuppO2,3.3 ± 2.2 ms/mm Hg; CA, 2.8 ± 1.8 ms/mm Hg) following thesupplemental oxygen treatment (p < 0.015). Thelow-frequency/high-frequency ratio of heart rate variability revealedsignificant differences between the two treatments (SuppO2,2.7 ± 1.2; CA, 3.1 ± 1.3; p < 0.008). The analysis of BPvariability 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 adecrease in mean heart rate after breathing SuppO2 comparedwith that after breathing CA (CA, 87.3 ± 13.3 beats/min; SuppO2, 85.0 ± 12.4 beats/min; p < 0.0004). Thearterial 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). Oxygen supplementation in, COPD patients significantly and favorably alters autonomicmodulation.