Low Oxygen Levels, Poor Exercise Endurance Are Common

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by Patricia Inacio PhD |

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Low oxygen levels during sleep and while exercising — resulting in poor endurance — are very common among Parkinson’s disease patients, despite dopaminergic treatment, an Italian study suggests.

The findings indicate a need for combining motor and respiratory rehabilitation, particularly for patients with severe Parkinson’s, who show the lowest oxygen levels.

The study “Exercise Intolerance and Oxygen Desaturation in Patients with Parkinson’s Disease: Triggers for Respiratory Rehabilitation?” was published in the International Journal of Environmental Research and Public Health.

People with Parkinson’s disease may have a higher prevalence for obstructive sleep apnea, according to some reports. However, it remains unclear whether disturbances in breathing during sleep or exercise are linked with symptoms, such as motor impairment, and affect patients’ rehabilitation.

To answer this, a group of researchers in Italy conducted a prospective data analysis from clinically stable Parkinson’s disease patients — on their “on” phase, meaning they were responsive to treatment with medication — and undergoing rehabilitation at two neuro-rehabilitation units in Italy.

“We aimed to test exercise tolerance and oxygen saturation levels both during exercise and at night in [Parkinson’s] patients to better define their rehabilitative needs,” the researchers wrote.

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Besides evaluating clinical data, disease severity, and additional disorders, the team also assessed sleepiness, motor function, balance, and lung function. These parameters were evaluated using spirometry — a test that measures how much air a person can breathe out in one forced breath — and the 6-minute walk distance (6MWD) test, which measures the distance walked for six minutes on a hard, flat surface. Peak cough expiratory flow (the maximum air flow generated during a cough) and continuous night oxygen monitoring also were evaluated.

In total, 55 patients (mean age 73 years, 53% men) were included in the analysis. Of these, 27 had mild Parkinson’s and 28 had moderate-to-severe disease. The majority (90%) were receiving treatment with levodopa, a precursor to dopamine; 45% were on dopamine agonists, which mimic the effect of dopamine by binding to the dopamine receptors; and 38% were on both levodopa and dopamine agonists.

Lack of the neurotransmitter dopamine — a chemical messenger essential for muscle control — is a hallmark of Parkinson’s disease.

The analysis showed that 96% of the patients had reduced exercise capacity at the 6MWD test, and severe impairments in respiratory muscles as shown by a maximum inspiratory (MIP) and maximum expiratory pressure (MEP), measures of the strength of respiratory muscles, below 45% predicted.

Also, 12.7% patients had below-normal oxygen levels (oxygen desaturation) during the night, and 21.8% failed to reach optimal oxygen levels during exercise.

Patients with moderate-to-severe Parkinson’s had a higher burden of additional diseases (comorbidities) and worse motor impairments and disabilities. Lung function, exercise capacity, and balance also were poorer.

The risk of poor lung function, as measured by a forced vital capacity (FVC%)    predicted of 80% or below, was seven times higher in moderate-to-severe patients compared to those with mild disease. Exercise tolerance, defined as a 6MWD predicted below 50%, was 19 times higher in those with moderate-to-severe Parkinson’s.

A prediction analysis revealed that increased disability and a low peak cough expiratory flow were significant predictors of low exercise tolerance as evaluated by the 6MWD.

Also, high body-mass index (BMI, a measure of body fat), the presence of additional diseases, and low oxygen levels during exercise were predictors of low oxygenation during the night. Predictors of low oxygen levels during exercise included being female, having high disability, younger age, and lower forced expiratory volumes.

Overall, the findings suggested that “exercise tolerance, exercise-induced desaturations, and nocturnal desaturations were extremely frequent in PD [Parkinson’s disease] patients and were worse in more severe PD patients,” researchers wrote.

“This suggests considering a combined role for motor and respiratory rehabilitation in these patients,” the team concluded.

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