how does respiration affect the blood pressure

It has been reported that deep breathing could reduce blood pressures (BP) in general. It is also known that BP is decreased during inhalation and increased during exhalation. Therefore, the measured BPs could be potentially different during deep breathing with different lengths of inhalation and exhalation. This study aimed to quantitatively investigate the effect of different respiratory patterns on BPs.

Methods

Forty healthy subjects (20 males and 20 females, aged from 18 to 60 years) were recruited. Systolic and diastolic BPs (SBP and DBP) were measured using a clinically validated automated BP device. There were two repeated measurement sessions for each subject. Within each session, eight BP measurements were performed, including 4 measurements during deep breathing with different respiratory patterns (Pattern 1: 4.5 s vs 4.5 s; Patter 2: 6 s vs 2 s; Pattern 3: 2 s vs 6 s; and Pattern 4: 1.5 s vs 1.5 s, respectively for the durations of inhalation and exhalation) and additional 4 measurements from 1 min after the four different respiratory patterns. At the beginning and end of the two repeated measurement sessions, there were two baseline BP measurements under resting condition.

Results

The key experimental results showed that overall automated SBP significantly decreased by 3.7 ± 5.7 mmHg, 3.9 ± 5.2 mmHg, 1.7 ± 5.9 mmHg and 3.3 ± 5.3 mmHg during deep breathing, respectively for Patterns 1, 2, 3 and 4 (all p < 0.001 except p < 0.05 for Pattern 3). Similarly, the automated DBPs during deep breathing in pattern 1, 2 and 4 decreased by 3.7 ± 5.0 mmHg, 3.7 ± 4.9 mmHg and 4.6 ± 3.9 mmHg respectively (all p < 0.001, except in Pattern 3 with a decrease of 1.0 ± 4.3 mmHg, p = 0.14). Correspondingly, after deep breathing, automated BPs recovered back to normal with no significant difference in comparison with baseline BP (all p > 0.05, except for SBP in Pattern 4).

Conclusions

In summary, this study has quantitatively demonstrated that the measured automated BPs decreased by different amounts with all the four deep breathing patterns, which recovered back quickly after these single short-term interventions, providing evidence of short-term BP decrease with deep breathing and that BP measurements should be performed under normal breathing condition.

Background

The importance of accurate blood pressure (BP) measurement is without doubt. According to a major review in the Journal of the American Medical Association (JAMA), a 5 mmHg error would result in 21 million Americans being denied treatment or 27 million being exposed to unnecessary treatment, depending on the direction of the error [1]. Unfortunately, BP measurement is still one of the most poorly performed diagnostic measurements in real clinical practice [2]. It is generally accepted that BP measurement inaccuracies are associated with the measurement conditions, including incorrect patient posture, incorrect arm position and incorrect cuff position and size [3–5], and also associated with short-term physiological changes during the measurement leading to within-subject BP variability [6]. It has been widely accepted that respiration is one of the key factors affecting short-term physiological changes in BP and therefore leading to potential measurement error [2].

Respiration is the natural physiological mechanism during which air is inhaled into the lungs and then exhaled via the nose or mouth. Normal breathing is involuntary and rhythmic, and two processes are involved during breathing are inspiration (or inhalation) and expiration (or exhalation) [7, 8]. During inspiration with oxygen inhaled into the body, the intercostal muscles contract, expanding the ribcage and the diaphragm contracts, pulling down to increase the volume of the chest. This lowers the pressure inside the thorax and gets air sucked into the lungs. During exhalation with carbon dioxide exhaled out of the body, the intercostal muscles relax and lower the ribs downward, causing the diaphragm to relax and move back upwards. This causes a decrease in thorax volume, which as a result, increases the pressure inside the thorax.

Several published studies have shown that respiration influences both short-term and long-term systolic and diastolic blood pressures (SBP and DBP) measured by different techniques [6, 9–14]. For instance, it has been reported by Zheng et al. [6] that, with regular slow and deep breathing, both manual auscultatory SBP and DBP decreased significantly by 4.4 and 4.8 mmHg respectively, in comparison with normal breathing. On the other hand, the physiological mechanisms of respiration process indicate that BP is decreased during inhalation and increased during exhalation [15]. Since a single BP measurement may take more than one or two normal respiratory cycles, the measured BPs could be potentially different with different types of deep breathings where various lengths of inhalation and exhalation are involved. To the best of our knowledge, there is little quantitative information available on the effect of different respiratory patterns on measured BPs.

The aim of this research was to quantitatively investigate the effect of different breathing patterns on BPs in comparison with baseline BP measurement.

Methods

Subjects

Forty healthy normotensive subjects, 20 males and 20 females, aged 18–60, were recruited. The requirements of inclusion criteria included: normal healthy individual, age range 18–60 years old, with SBP < 140 mmHg and DBP < 90 mmHg. Participants with known hypertension and antihypertensive medical treatment, or cardiovascular disease, such as ischaemic heart disease, congestive heart failure, chronic atrial fibrillation, renal failure and previous stroke, were excluded.                                                                                                                                     The measurements were conducted in a quiet room at Anglia Ruskin University. All the subjects were asked to rest in a seated position for at least 5 min before the formal BP measurement. SBP, DBP were measured from the left arm using a suitable cuff matched to individual arm circumference (adult 24–34 cm; large adult 34–41 cm) by a clinically validated automated BP device (HBPM Omron, M6 Comfort). The HR value was also obtained during each measurement from the device. The BP measurement procedure followed the Measurement Guideline from the European Society of Hypertension [16].

A mobile phone application (Paced Breathing, Android App on Google Play), which was designed to adjust the duration of inhalation and exhalation and display the visual pattern on the screen it was used for the subjects to follow the different respiratory patterns and synchronize their breathing with the defined patterns. All subjects were given the opportunity to practice and be familiar with these respiratory patterns before the formal experiment.                                                Overall, the four respiratory patterns applied in this study all reduced the short-term BPs by different amounts. It is noticed that the participants felt more comfortable to follow some patterns than the others, indicating different physiological mechanisms could be involved in these patterns. There is also possibility of this BP lowering effect might be from “self-notice” of own respiration or concentration on own respiration regardless of respiratory pattern. Published report has showed transcendental meditation is associated with reductions of SBP and DBP . Similar BP reduction was observed in both normotensive and hypertensive individuals. For a better understanding of their underlying mechanisms, more data about BP reduction efficacy of self-notice or concentration on spontaneous respiration is required in a future study.