Research Review: Dyspnea (Shortness of Breath) in PD
Respiratory problems have been associated with Parkinson’s disease (PD) since it was first documented by James Parkinson in 1817.
The problems that people with PD experience in breathing and lung function can look very different depending on the individual. Respiratory dysfunction can be related to breathing restriction due to chest wall rigidity, reduced lung volume due to stooped posture, diaphragm dyskinesias, and lung damage caused by medications.
A 2016 electronic literature review by K. Torsney and D. Forsyth of the Royal College of Physicians in Edinburgh investigated the types of respiratory dysfunction occurring in people with PD as well as the effects of levodopa on respiratory function.
Findings of the review:
Upper airway obstruction (UAO) has been reported in over one third of people with PD. The most common type of UAO is hypophonia (signs are hoarse voice, reduced loudness, reduced pitch and loudness variability in speech). Prevalence of UAO in subjects with PD ranges from around 7 percent to 67 percent depending on whether levodopa was taken during the study or not.
The overall prevalence of UAO in people with PD seems to be declining and may be related to better diagnosis and management of the problem or to the effectiveness of levodopa.
Restrictive respiratory dysfunction — most commonly felt as dyspnea (shortness of breath) with exertion — was reported in 28 to 94% of people with PD depending on the size and health of the group studied, severity of PD, and whether the subjects were taking levodopa during the study or not.
Many people with PD who have respiratory dysfunction do not show symptoms or report shortness of breath. This may be for two reasons: 1) as PD motor symptoms progress, a person‘s tolerance for exercise may decrease and respiratory symptoms may not be noticeable and 2) people with PD have been shown to have an impaired perception of dyspnea (POD).
Levodopa use results in significant improvement in POD. In addition to levodopa, specific training to increase inspiratory muscle strength and endurance has been shown to reduce POD.
There is controversy whether levodopa improves or worsens respiratory function. Levodopa and ergot-derived dopamine agonists may also bring about respiratory problems in people with PD.
Conclusions of the review:
Greater awareness of respiratory dysfunction in PD will help providers identify signs and symptoms earlier, resulting in better treatment and outcomes.
More systematic studies are needed to investigate respiratory dysfunction in PD and to understand the effect of levodopa on respiratory function.