Inspiratory muscle training improves muscle endurance, dyspnea following COVID-19
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Key takeaways:
- Two years after COVID-19 hospitalization, patients still had inspiratory muscle weakness.
- Six-week inspiratory muscle training appears to be promising for those suffering with long COVID.
SAN DIEGO — Individuals with inspiratory muscle weakness 2 years after COVID-19 hospitalization had improvement with inspiratory muscle training, according to research presented at the American Thoracic Society International Conference.
“Inspiratory muscle weakness, together with decreased diaphragm cortical activation, might underlie dyspnea on exertion individuals with long COVID,” Michael Dreher, MD, head of the department of internal medicine at University Hospital Aachen in Germany, said during his presentation.
As Healio previously reported, 15 months following COVID-19 hospitalization, both ventilated and nonventilated patients displayed diaphragm muscle weakness, and this impairment was linked to shortness of breath when conducting physical efforts.
In an observational and interventional clinical trial, Dreher and colleagues assessed 30 patients (median age, 58.3 years; 63% men) previously hospitalized with COVID-19 to see if respiratory muscle weakness and symptoms remain 2 years since hospitalization.
“None of them suffered from COPD, asthma or systolic heart failure,” Dreher said. “They all had normal lung function parameters, and echocardiographic assessment was completely normal, but the majority of them still suffer from dyspnea.”
Among those with diaphragm muscle weakness and unexplained exertional dyspnea (n = 18), researchers wanted to assess whether 6-week inspiratory muscle training (IMT) could improve inspiratory muscle fatiguability and did so by randomly assigning nine patients to IMT and nine patients to sham training, which was coined “endurance training” to patients.
“In the IMT arm and in the sham arm, the people were asked to overcome 30 breaths in the morning and 30 breaths in the evening,” Dreher said.
A key difference between the IMT group and the sham training group was the set resistance level. According to Dreher, resistance for those receiving IMT was 40% to 50% of individual sniff nasal inspiratory pressure, whereas resistance was 10% of individual maximal sniff nasal inspiratory pressure for those receiving sham training.
“The strength of overcoming five of these breaths was rated four to seven on a visual analogue scale,” Dreher said.
On a weekly basis, those in the IMT group had their resistance adjusted, whereas in the sham training group, resistance did not change.
After the 6-week training period, as well as 6 weeks following the end of this training, researchers evaluated outcomes via a global inspiratory muscle assessment, Dreher said.
This study’s median follow-up period after hospitalization was 31 months.
In the time after COVID-19 hospitalization, specifically between 14 and 31 months, researchers found no improvement in dyspnea.
“There was no natural recovery,” Dreher said during his presentation.
In contrast, patients demonstrated slight improvement in respiratory muscle function, but these positive changes were not enough to rid them of having “deteriorated” function.
Similar to the study assessing muscle weakness 15 months after COVID-19 hospitalization, Dreher said there was a link between exertional shortness of breath and diaphragm muscle weakness, inspiratory muscle weakness and diaphragm cortical activation.
Switching to the IMT analysis, researchers observed a similar proportion of completed sessions in the IMT group (85%) and the sham group (87%).
During his presentation, Dreher highlighted that patients receiving IMT vs. sham IMT had improvements in several measures including global inspiratory muscle strength, diaphragm voluntary activation, inspiratory muscle endurance and dyspnea.
When reassessed 6 weeks after completing the training, patients in the IMT group continued to have these improved measures.
“The current randomized, sham-controlled trial is the first to show that 6 weeks of inspiratory muscle strength training could improve inspiratory muscle endurance and coronal activation, and thereby exertional dyspnea in individuals with long COVID,” Dreher said. “This represents to our point of view a potential treatment for persisting long COVID-associated external dyspnea related to inspiratory muscle weakness.”