There is growing interest in how breathing pace, pattern, and training (e.g., device-guided or -resisted breathing) affect cardiovascular health. It is unknown whether the route of breathing (nasal vs. oral) affects prognostic cardiovascular variables. Because nasal breathing can improve other physiological variables (e.g., airway dilation), we hypothesized that nasal compared with oral breathing would acutely lower blood pressure (BP) and improve heart rate variability (HRV) metrics. We tested 20 adults in this study [13 females/7 males; age: 18(1) years, median (IQR); body mass index: 23 ± 2 kg·m-2, means ± SD]. We compared variables between nasal- and oral-only breathing (random order, five min each) using paired, two-tailed t tests or Wilcoxon signed-rank paired tests with significance set to P < 0.05. We report the median (interquartile range) for diastolic BP and means ± SD for all other variables. We found that nasal breathing was associated with a lower mean BP (nasal: 84 ± 7 vs. oral: 86 ± 5 mmHg, P = 0.006, Cohen's d = 0.70) and diastolic BP [nasal: 68(8) vs. oral: 72(5) mmHg, P < 0.001, Rank-biserial correlation = 0.89] but not systolic BP (nasal: 116 ± 11 vs. oral: 117 ± 9 mmHg, P = 0.48, Cohen's d = 0.16) or heart rate (HR; nasal: 74 ± 10 vs. oral: 75 ± 8 beats·min-1, P = 0.90, Cohen's d = 0.03). We also found that nasal breathing was associated with a higher high-frequency (HF) contribution to HRV (nasal: 59 ± 19 vs. oral: 52 ± 21%, P = 0.04, Cohen's d = 0.50) and a lower low frequency-to-HF ratio at rest (nasal: 0.9 ± 0.8 vs. oral: 1.2 ± 0.9, P = 0.04, Cohen's d = 0.49). These data suggest that nasal compared with oral breathing acutely 1) lowers mean and diastolic BP, 2) does not affect systolic BP or heart rate, and 3) increases parasympathetic contributions to HRV.NEW & NOTEWORTHY There is growing interest in how breathing pace, pattern, and training (e.g., device-guided or -resisted breathing) affect prognostic cardiovascular variables. However, the potential effects of the breathing route on prognostic cardiovascular variables are unclear. These data suggest that nasal compared with oral breathing 1) lowers mean and diastolic blood pressure (BP), 2) does not affect systolic BP or heart rate (HR), and 3) increases parasympathetic contributions to heart rate variability (HRV). These data suggest that acute nasal breathing improves several prognostic cardiovascular variables.
Keywords: blood pressure; blood pressure variability; breathing; cardiac vagal baroreflex; heart rate variability.