Am J Hyperten ; 15(4,2)182A. 2002
Acute effects of device-guided breathing on cardiovascular parameters and baroreflex sensitivity in normal subjects.
1, 2Parati G, 2Glavina F, 2Ongaro G, 2Maronati A, 2Gavish
B, 3Castiglioni P, 3Di Rienzo M, 1Mancia G. 1Dept. Internal Medicine,
University of Milano-Bicocca, Milan, Italy, 2II Dept. Cardiology, S. Luca Hospital, Ist. Auxologico Italiano,
Milan, Italy, 3LaRC, Centro Bioingegneria, Fondaz. Don Gnocchi, Milan, Italy
Repeated episodes of slow breathing (SLB) reduce blood pressure (BP) in hypertension, perhaps by increasing baroreflex sensitivity. This study investigated the acute effects of SB produced with a device-g, 1/ HR) and spontaneous sensitivity of baroreflex control of HR (BRS) in normal subjects. In supine normal volunteers (n=15; ageuided breathing exercise (RESPeRATE, InterCure) on BP, pulse interval (PI 39.9 ± 8.4 yrs, 10 males) finger BP, PI, respiratory rate (RR), ETCO2 and SaO2 were continuously recorded for 3 periods of 15 min each: baseline (BAS), SLB, and resumption of spontaneous breathing (SB). Beat-by-beat systolic (S)BP and PI values were averaged during each period. SD was used as an index of variability of SBP and PI. BRS was quantified as the LF and HF coefficient (squared ratio of the spectral powers of PI and SBP at 0.1 and 0. 3 Hz, respectively) and by the slope of +PI/+SBP and -PI/-SBP) sequences. RR was 12.5 breath/min during BAS and SB and fell to 5.2 breath/min during SLB (p<0.01). ETCO2 and SaO2 did not change throughout the study. BAS SBP and PI were 124.3±13.5 mm Hg and 0.951±0.134 sec, respectively, with no change during SLB or SB. PI SD was 0.064.0±0.026 sec in BAS and increased to 0.074.0±0.028 and 0.082±0.030 sec during SLB and SB respectively (p<0.01). SBP SD showed a tendency to increase in parallel (NS). LF was 12.6±6.5, 14.9±7.2 and 14.7±7.5 msec/mm Hg during BAS, SLB, and SB respectively (p<0.05 vs BAS). The corresponding values of -PI/-SBP slope were 13.0±7.8, 15.6±6.7 and 16.3±6.4 msec/mm Hg (p<0.05 vs BAS). HF and +PI/+SBP slope also showed a tendency to increase vs BAS. The number of +PI/+SBP and -PI/-SBP sequences was 7.7±6.6 and 8.4±5.7, respectively, during BAS, increased to 23.2±16.9 and 32.3±16.0 during SLB (p<0.01) and returned to 10.2±6.9 and 12.4±5.2 during SB (NS vs BAS). In summary, acute SLB has no effect on BP and PI in normal subjects, but increases PI variability and BRS in the LF region and during baroreceptor deactivation during and after SLB. We conclude that the favourable effects of repeated SLB on cardiovascular parameters may be at least partially mediated by increased BRS and by cardiac vagal modulation.
