Effects of deep breathing on blood pressure measurement in healthy subjects

The aim of this study was to investigate the effects of deep breathing on blood pressure parameters: systolic (SBP), diastolic (DBP) and pulse pressure, mean pulse rate (MPR), and the amplitude of Korotkoff sounds. Manual SBP and DBP were measured from 20 healthy subjects (age: 44±13 years) during normal (NB) and deep (DB) breathing. A chest magnetometer was used to acquire the respiratory depth, and an electronic stethoscope for the Korotkoff sound. All data were sampled at 2 kHz. MPR was derived from the oscillometric pulse waveform. For each oscillometric pulse, time-frequency analysis of the Korotkoff sound located the time of the peak energy (Tp), and Korotkoff sounds amplitude was defined as the maximum peak-to-peak amplitude in the window T
P
±50ms. The respiratory rate was calculated from both the magnetometer (f
R
) and Korotkoff amplitude series (f
K
) for the period between the manually measured SBP and DBP, with a power spectral density resolution of 0.016 Hz in the physiological respiratory frequency range at rest. DB compared to NB increased respiratory regularity (quantified by spectral concentration) by 9±10% (mean±SD, p<0.005), and decreased f
R
from 0.24±0.06 to 0.20±0.05 Hz (p<0.0005). SBP and pulse pressure also decreased, from 116±12 to 113±11 mmHg (p<0.005) and 41±9 to 37±9 mmHg (p<0.01) respectively, and MPR increased from 64±8 to 68±9 pulse/min (p<0.0005). In 70% of recordings f
R
differed from f
K
by 0.05 Hz or less. The results show an effect of DB on blood pressure, and the presence of a modulating effect of respiration on the Korotkoff sound.