*From the North West Lung Research Centre, Wythenshawe Hospital, Manchester, UK.
Correspondence to: Curig Prys-Picard, MA, North West Lung Research Centre, Wythenshawe Hospital, Southmoor Rd, Manchester OL5 0BA, UK; e-mail: email@example.com
Disproportionate breathlessness is a term that is used synonymously with dysfunctional breathing and idiopathic hyperventilation in the absence of chest disease. In the presence of chest disease, it may not be possible to use these three terms interchangeably. We report a case of a patient with documented asthma but breathlessness that was out of proportion to the measured lung function or exercise tolerance. The breathing pattern was abnormal and was characterized by the need to take frequent deep sighs, which increased in frequency during incremental exercise, despite increasing respiratory rate and tidal volume. Treatment with physiotherapist-led breathing retraining resulted in an improvement in the sigh rate and breathlessness scores. Disproportionate breathlessness and deep sighing breathing are part of the spectrum of conditions that comprise dysfunctional breathing and can cause symptoms that may be wrongly attributed to asthma.
The term disproportionate breathlessness is used synonymously with dysfunctional breathing and idiopathic hyperventilation in the absence of concomitant chest disease.1 When chest pathology is present, it is not possible to reliably attribute symptoms either to dysfunctional breathing or to the chest disease. We present a case of disproportionate breathlessness associated with deep sighing breathing in a patient with difficult-to-treat asthma.
The patient was a 33-year-old chemical engineer who was initially referred for an assessment of occupational asthma. She was receiving therapy with 500 μg of fluticasone and a long-acting β2-agonist daily, and had required three unplanned visits to here primary care physician in the previous year. She complained of daily symptoms of breathlessness on exertion. Assessments were made as part of her routine care and as part of an interventional trial of breathing retraining in patients with severe asthma. We measured breathlessness using the University of California, San Diego (UCSD) shortness of breath (SOB) questionnaire2(score range, 0 [minimum] to 120 [maximum]). In a study3 of 521 patients with COPD (mean FEV1, 44% predicted), the mean UCSD SOB score was 56.8.
Over the course of 6 months, the patient was assessed twice. Her FEV1 was normal on each occasion (110% and 116% predicted) as was her FEV1/FVC ratio. Asthma was confirmed by histamine reactivity (ie, a provocative concentration causing a 20% fall in FEV1 varying between 1.5 and > 8 mg/mL) demonstrating airway hyperreactivity. The sputum eosinophil count was raised at 8.5% (normal, < 2%), implying continued airway inflammation, but the fraction of exhaled nitric oxide measured at 50 mL/s was normal at 8.9 parts per billion (normal, < 15 parts per billion). There was no suggestion of vocal cord dysfunction from the patient’s medical history, and flow-volume loops were consistent with an intrathoracic obstructive defect and were reproducible.
At the baseline assessment, the patient scored 99 on the UCSD SOB questionnaire, indicating a high degree of breathlessness. Her modified Borg score relating to the preceding 2 weeks was 5, corresponding to “severe breathlessness.” Incremental shuttle walk tests4 were performed 1 year apart. On each occasion, despite rating herself limited by breathlessness, she was able to complete 12 min of the shuttle test (requiring a steady jog).
Breathing patterns were measured by respiratory inductance plethysmography (RIP) [Lifeshirt; Vivometrics Inc; Ventura, CA] both at rest and during exercise. These were characterized by the need to take frequent deep sighs, as shown in Figure 1
As the exercise intensity increased, so did the respiratory rate and tidal volume. The need to take deep breaths increased in frequency (Fig 2
) to an equivalent of 60 sighs per 15-min period.
The patient completed five monthly sessions of physiotherapist-led breathing retraining. After assessment, this consisted of breathing control and reeducation, relaxation and stress management, and a graduated activity/exercise program. The patient’s condition improved; her UCSD SOB score dropped to 85 at 6 weeks after treatment, and to 72 at 6 months after treatment. This represents a total reduction of 27 points (ie, a 27% reduction). Her resting sigh rate had dropped to five sighs per 15-min period at rest. Her FEV1 remained unchanged (105% predicted).
Deep sighing breathing has been reported in patients who are in chronic anxiety states. Healthy subjects sigh between none and 3 times per 15-min period, while chronic anxiety patients sigh 4 to 25 times per 15-min period.5 This is the first description of an increase in sigh rate in response to exercise.
This subject presented clearly has mild-to-moderate asthma, as evidenced by her lung function, and bronchial hyperreactivity. She appears to have disproportionate breathlessness since she has normal values of FEV1 with an excellent exercise tolerance but extremely high breathlessness scores. After undergoing breathing retraining, her breathlessness improved and the sigh rate decreased. Dysfunctional breathing (in this case, deep sighing breathing) can be associated with symptoms that may be wrongly attributed to asthma. Dysfunctional breathing may be very responsive to physiotherapist-led breathing retraining.
This case demonstrates the difficulty in using the term disproportionate breathlessness synonymously with hyperventilation in the presence of asthma. The breathlessness can only be described as being disproportionate when the asthma is apparently reasonably well controlled and the exercise tolerance is good. This is a different clinical scenario from that of idiopathic hyperventilation, in which exercise tolerance is limited. Deep sighing breathing in association with disproportionate breathlessness forms part of a spectrum of conditions that are described as dysfunctional breathing.
Abbreviations: RIP = respiratory inductance plethysmography; SOB = shortness of breath; UCSD = University of California, San Diego
This work was funded entirely by the North West Lung Research Centre. The Lifeshirt was provided on loan by Vivometrics Inc, Ventura CA.
The authors have reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.
The UCSD SOB questionnaire was used with permission of the UCSD Medical Center.
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