Controlled breathing protocols probe human autonomic cardiovascular rhythms

Abstract

The purpose of this study was to determine how breathing protocols requiring varying degrees of control affect cardiovascular dynamics. We measured inspiratory volume, end-tidal CO2, R-R interval, and arterial pressure spectral power in 10 volunteers who followed the following 5 breathing protocols: 1) uncontrolled breathing for 5 min; 2) stepwise frequency breathing (at 0.3, 0.25, 0.2, 0.15, 0.1, and 0.05 Hz for 2 min each); 3) stepwise frequency breathing as above, but with prescribed tidal volumes; 4) random-frequency breathing (∼0.5–0.05 Hz) for 6 min; and 5) fixed-frequency breathing (0.25 Hz) for 5 min. During stepwise breathing, R-R interval and arterial pressure spectral power increased as breathing frequency decreased. Control of inspired volume reduced R-R interval spectral power during 0.1 Hz breathing ( P < 0.05). Stepwise and random-breathing protocols yielded comparable coherence and transfer functions between respiration and R-R intervals and systolic pressure and R-R intervals. Random- and fixed-frequency breathing reduced end-tidal CO2modestly ( P < 0.05). Our data suggest that stringent tidal volume control attenuates low-frequency R-R interval oscillations and that fixed- and random-rate breathing may decrease CO2 chemoreceptor stimulation. We conclude that autonomic rhythms measured during different breathing protocols have much in common but that a stepwise protocol without stringent control of inspired volume may allow for the most efficient assessment of short-term respiratory-mediated autonomic oscillations.

Breathing-control lowers blood pressure

“…The results of our study are supported by studies in the literature showing that an acute slow and regular breathing pattern may beneficially affect reflex control of the cardiovascular system and modulates BP, probably via stimulation of slowly adapting pulmonary stretch receptors. 13,16,26 More specifically, slowing down breathing rate increases baroreceptor sensitivity. 15 The breathing rate achieved by the patients during the active treatment is much slower than normal breathing (12-20 breaths per minute) and overlays the frequency range of large effects of breathing on acute cardiovascular response.…”

“…15 The breathing rate achieved by the patients during the active treatment is much slower than normal breathing (12-20 breaths per minute) and overlays the frequency range of large effects of breathing on acute cardiovascular response. 15,16,26 However, this mechanism cannot be extrapolated to explain sustained BP reduction following a series of repeated interventions. The slow breathing rate achieved by the patients in the treatment group at the end of the treatment sessions demonstrates a potential for eliciting an acute response to slow breathing.…”

Heart rate variability and spontaneous baroreflex sequences in supine healthy volunteers subjected to nasal positive airway pressure

“…Subjects were instructed to maintain this breathing frequency throughout the different ventilatory settings. Short-term laboratory recordings using frequency-controlled breathing protocols avoid artifacts in the low-frequency (LF) range of HRV from irregular slow breaths (10). Each PAP level was sustained for 10 min.…”

“…Any interpretation of measurements of HRV and baroreflex gain must acknowledge the influences of respiration. When the breathing rate is at frequencies below ϳ12 breaths/min, LF and HF R-R interval oscillations tend to merge, making it impossible to evaluate parasympathetic neural outflow without pharmacological blockade (10). In the assessment of relative power distribution of HRV, it is therefore important to ensure that the respiratory pattern is limited to the HF component (6).…”

Leave-one-out prediction error of systolic arterial pressure time series under paced breathing

“…Concerning the second group, cardiac death occurred in 54 (20%) of the patients during a 3-year follow-up, while the other 221 patients were still alive at the end of the follow-up period. All the subjects underwent a 10 min supine rest, recorded in the paced respiration regime (Cooke et al 1998, Rzeczinski et al 2002. To perform paced breathing, subjects were asked to follow a digitally recorded human voice inducing inspiratory and expiratory phases, at 0.25 Hz frequency.…”