The effect of breathing retraining on the cardiovascular system

We thought we'd focus on the role of breathing on the cardiovascular system. 

This is a pertinent topic as COVID19 seems to target the respiratory system, but also has broad cardiovascular interactions. COVID19 risk factors include hypertension, cardiovascular disease, diabetes, and COPD that can worsen the course of severe COVID19 and SARS illness.  Cardiorespiratory Physiotherapy can target these cardiovascular risk factors and diseases to improve outcomes. 

Hypertension and inspiratory muscle training (IMT)

Research evidence has been building over the past few years that daily sessions of IMT helps to improve inspiratory strength and reduce resting heart rate and hypertension in at-risk patients. The results of one meta-analysis show that moderate and low intensity IMT was associated with a reduction of resting heart rate (7.5 BPM reduction in heart rate), while moderate to high intensity IMT reduced diastolic blood pressure (8.9 mmHg reduction in Blood Pressure). (Cipriano et al, 2019).

How does this work?
During Inspiratory Muscle Training, the lungs with certain exercises are inflated close to maximum capacity and this may cause pulmonary parasympathetic stimulation, and consequently sympathetic activity reduction. Therefore, in patients with essential hypertension, blood pressure reduction has been associated with sympathetic activation reduction and increased parasympathetic tone.
 
Often in elderly patients, it's difficult to increase respiratory and cardiovascular load through general walking or biking exercise, due to musculoskeletal problems such as hip and knee OA, and balance issues. Therefore, an advantage of IMT is that it can be completed statically sitting or standing in these groups.

POTS (postural orthostatic tachycardia syndrome)

POTS is a challenging to treat syndrome that is defined as an increase in heart rate of ≥30 bpm in adults (or by ≥40 bpm in children), within 10 minutes of standing, with no orthostatic fall in blood pressure. Recently research has shown that respiratory fluctuations of hyperpnea (breathing more deeply and sometimes faster than usual) and hypocapnia, (but not fast breathing or tachypnea), can create significant decreased cardiac output, increased blood pressure and increased peripheral resistance which worsens the symptoms of POTS.
 
Encouragingly, a recent pilot study of 100 POTS patients has suggested that physiotherapy breathing retraining may be useful in targeting these breathing changes and was shown to reduce symptoms in this cohort (Reiley et al 2020). This is promising and may lead to physiotherapy being standard care in POTS patients in the future.

Chronic heart Failure

IMT has also shown strong positive results in Chronic Heart Failure populations with improvements in walking distance (6 minute walk test), reduced shortness of breath, and quality of life in both RCTs and meta-analysis (Wu and Kuang, 2018; Hossein et al 2020). This is like the effects seen with cardiac rehabilitation and pulmonary rehabilitation.

Bottom Line

Breathing rehabilitation physiotherapy and Inspiratory Muscle Training have the potential to improve many cardiovascular parameters and diseases in meaningful ways.