Very-low-frequency oscillations in heart rate and blood pressure in periodic breathing: role of the cardiovascular limb of the hypoxic chemoreflex

In chronic heart failure, very-low-frequency (VLF) oscillations (0.01-0.04 Hz) in heart rate and blood pressure may be related to periodic breathing, although the mechanism has not been fully characterized. Groups of ten pati ents with chronic heart failure and ten healthy controls performed voluntar y periodic breathing with computer guidance, while ventilation, oxygen satu ration, non-invasive blood pressure and RR interval were measured. In air, voluntary periodic breathing induced periodic desaturation and prominent VL F oscillations when compared with free breathing in both patients [RR inter val spectral power from 179 to 358 ms(2) (P < 0.05); systolic blood pressur e (SBP) spectral power from 3.44 to 6.25 mmHg(2) (P < 0.05)] and controls [ RR spectral power from 1040 to 2307 ms(2) (P < 0.05); SBP spectral power fr om 3.40 to 9.38 mmHg(2) (P < 0.05)]. The peak in RR interval occurred 16-26 s before that in SBP, an anti-baroreflex pattern. When the patients follow ed an identical breathing pattern in hyperoxic conditions to prevent desatu ration, the VLF RR interval spectral power was 50% lower (179.0 +/- 51.7 ms (2); P < 0.01) and the VLF SBP spectral power was 44% lower (3.51 +/- 0.77 mmHg(2); P < 0.01); similar effects were seen in controls (VLF RR power 20% lower, at 1847 +/- 899 ms(2), P < 0.05; VLF SBP power 61% lower, at 3.68 /- 0.92 mmHg(2), P = 0.01). Low- and high-frequency spectral powers were no t significantly affected. Thus periodic breathing causes oxygen-sensitive ( and by implication chemoreflex-related) anti-baroreflex VLF oscillations in RR interval and blood pressure in both patients with chronic heart failure and normal controls.