Abstract

Introduction

POTS is a chronic syndrome with complex symptoms of orthostatic intolerance. It is defined as an increase in heart rate of ≥ 30bpm in adults (≥40 bpm in children) within 10 minutes of standing with no orthostatic drop in blood pressure.

POTS is more common in women. Symptoms can be debilitating (impairment comparable to congestive heart failure and COPD) and include palpitations, light headedness/syncope, chest discomfort, breathlessness, neuropathic pain, chronic fatigue, poor sleep efficience, gastrointestinal symptoms, syncope, cognitive slowing, and psychological distress.

Breathlessness is a common symptom in POTS. Breathlessness is often attributed to changes in breathing pattern, frequency, and/or quality occuring alongside cardiac symptoms. Breathlessness can be episodic, triggered by physical activity, stressful thoughts and events.

Dysfunctional breathing (DB) is an umbrella term describing breathing disorders where chronic changes in breathing pattern result in breathlessness and other symptoms without respiratory or cardiac disease. The most studied form of DB is hyperventilation syndrome (HVS)

Boulding et al. (2016) suggest classifying dysfunctional breathing into the following: 1) Hyperventilation syndrome (a respiratory pattern associated with symptoms both related to respiratory alkalosis and independent of hypocapnia), 2) Periodic deep sighing (frequent sighing with an irregular breathing pattern), 3) Thoracis dominant breathing (a respiratory pattern occurring separate to somatic disease may be considered dysfunctional and results in dyspnoea), 4) Forced abdominal expiration (inappropriate and excessive use of abdominal muscle contraction to aid expiration), 5) Thoraco-abdominal asynchrony (a respiratory pattern in which there is delay between rib cage and abdominal contraction resulting in ineffective breathing movements)

Patients with POTS often undergo extensive investigations due to the complexity of potential comorbidities but there is no guidance or consensus on the assessment of breathlessness.

Methods

Retrospective study of POTS patients referred to repiratory physiotherapy

Respiratory physiotherapy outpatient's referral criteria: tests performed and identification of DB/HVS are explained

Physiotherapy assessment and outcome measures

A standardised physiotherapy assessment of symptoms was performed on all patients (details provided in the paper)

Physiotherapy intervention:

The physiotherapy intervention was standaradised in terms of education and breathing re-training exercises and was delivered by a consultant physiotherapist of a highly specialised respiratory physiotherapist. Each patient was assessed and treated by the same physiotherapist.

Physiotherapy treatment

The educational component focused on patient's understanding of respiratory physiology and the mind-body link

Breathing re-training intervention involved teaching breathing control (details provided). The breathing retraining exercises were standardised and progressive. All techniques used were standard respiratory physiotherapy techniques commonly applied for acute and chronic respiratory disease. Their use for breathlessness in POTS had no previously been assessed.

Patients were discharged when they were confident to continue the re-training programme independently or if they did not attend for follow-up appointments.

Data analysis: details and figures provided in the paper

Results

Demographic information is given in Table 1

Signficiant improvements were observed and are noted in Table 2

Discussion

This paper is the first to characterise DB/HVS and investigate the impact of physiotherapy in POTS. The results indicate that breathing retraining results in significant improvements in breathing pattern and symptom burden thus potentially improving their health related quality of life. Further studies are needed.

Significance of the findings

it is estimated that DB/HVS affects 10% of the general population and is more prevalent in women than men. Patients with POTS who reported respiratory symptoms had DB/HVS. DB/HVS may coexist alongside chronic respiratory diseases and COPDalthough the relationship is unclear.

Although there were statistically significant improvements for the patient cohort as a whole, not all patients had complete resolutions of their DB/HVS and there are several limitations in interpreting the results for this study.

Unexplained breathlessness or 'air hunger' are predominant symptoms of DB/HVS and can result in significant patient morbidity and an array of non-respiratory symptoms which can themselves provoke anxiety/panic and further breathing irregularity

Whilst orthostatic tachycardia is the main symptom of POTS, orthostasis causes a variety of other symptoms through a vaireity of different mechanisms. The paper provides an overview of the hypothesised mechanisms.

Psychological influences (stress, axniety, depression, etc.) are highly prevalent in POTS patients and predispose them to DB/HVS. The impact of this study's intervention could, therefore, be partly related to a change in anxiety thanks to education, greater understanding of DB/HVS, and empowerment.

Proposed improvements for further studies include the inclusion of pre-post PaCO2 measurements, the exclusion of asthma and pulmonary hypertension, analysis of why patients attended appointments (and addressing the issues)

Access to respiratory physiotherapy outpatient services is limited across the NHS and many POTS patients are instead seen by muscluloskeletal physiotherapists due to comorbidities. Increased awareness may improve treatment for these patients

More data is needed to investigate the prevalence of dysfunctional breathing in POTS and how it relateds to other chronic conditions. More detailed investigation and assessment guidelines and techniques are needed.

Limitations

No control data were available

Outcome measures were potentially not sensitive to non-hyperventilatory dysfunctional breathing

Observational nature and small sample size did not allow exploration of the role of confounding variables

A selection bias may have been introduced due to this being a convenience sample

The Nijmegen score used to characterise these patients has not been validated in this patient population. Its limitations highlight the need for a holistic POTS-specific measure.

Physiological outcome measures for the diagnosis of HVS are often limited to specialist services so alternative diagnostic tests are sought. The Breathing Pattern Assessment Tool (BPAT) has demonstrated good sensitivity and specificity for the diagnosis of DB in refractory asthma. Responsiveness of the BPAT to treatment remains to be ascertained.

Measuring Neural Respiratory Drive (NRD) in breathlessness patients with POTS may be advantageous. NRD provides a global measure of breathlessness and a physiological correlate to breathlessness but there is no data on whether NRD is increased in POTS or on NRD pre-post respiratory interventions