Respiratory Muscle Assesment in COVID-patients Without Hospitalization

Study Overview
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Brief Summary
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Fatigue and exercise intolerance after survived COVID-19-infection might be related to weakness of the respiratory muscles. The aim of the project is to measure respiratory muscle function and strength in our respiratory physiology laboratory in patients who were not hospitalized during the acute COVID-19-infection but still complain of different persistent symptoms including exertional dyspnea and fatigue.

Detailed Description
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Since the beginning of the COVID pandemic, more and more recovered patients have a number of persistent symptoms including exertional dyspnea and fatigue even months after recovering from acute coronavirus disease 2019 (COVID-19). These symptoms often cannot be explained because routine clinical diagnoses, including extensive cardiac and pulmonary examinations, do not reveal any relevant abnormalities. In our previous study (Regmi et al) with 50 patients formerly hospitalized due to acute COVID-19 infection, it was shown that diaphragm muscle weakness contributes to persistent exertional dyspnea about one year after hospitalization for COVID-19, regardless of mechanical ventilation. Additionally, the severity of exertional dyspnea correlated with the extent of diaphragmatic weakness. Since laboratory findings, pulmonary function tests and cardiological routine examinations did not reveal any significant impairments, this was the first time that a potential pathophysiological correlate is objectively associated with dyspnea in long COVID-19 syndrome. The results of our study were clinically relevant because the persistent symptom burden in patients after surviving COVID-19 infection remains very high. In addition diaphragm training presents itself as a potential therapeutic target, since in other diseases such as COPD, such training has been shown to improve the symptoms. Therefore, the investigators believe that the results provide important perspectives, both for the pathophysiological understanding and for the potential treatment of persistent exertional dyspnea in patients. However, a considerable gap exists here: a significant number of patients who suffer from an acute COVID-19 infection but do not have a severe course during the initial infection, so that hospitalization is not necessary, still complain of different persistent symptoms. Here, too, despite an extensive cardiopulmonary work-up, there is a lack of a sufficient explanation of the lasting complaints. It is precisely in these patients that a possible role of diaphragmatic weakness on the symptoms is yet to be investigated using already established gold standard techniques.

Official Title
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Potential Role of Diaphragmatic Muscle Weakness as a Cause of Persistent Exertional Dyspnea in Patients With COVID-19 Disease Without Hospitalization

Conditions
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Covid19, Diaphragm Injury

Intervention / Treatment
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* Diagnostic Test: Comprehensive assessment of respiratory muscle function.


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patients with COVID-19 infection without hospitalization during the acute infection (n=25) Patients aged at least 18 years, who are mentally and physically able to consent and participate into the study Exclusion Criteria: Clinically pre-established cardiovascular disease or other pulmonary diseases which might lead to exertional dyspnea (systolic heart failure, COPD). Body-mass-index (BMI) >40 Expected absence of active participation of the patient in study-related measurements Alcohol or drug abuse Metal implant in the body that is not MRI compatible (NON MRI compatible pacemaker, implantable defibrillator, cervical implants, e.g. brain pacemakers etc.) Slipped disc Epilepsy Bound to a wheel chair

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 75 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Intervention/Treatment |
| --- |
|Diagnostic Test: Comprehensive assessment of respiratory muscle function.|Comprehensive assessment of respiratory muscle function to the point of its invasive assessment with recordings of twitch transdiaphragmatic pressure in response to magnetic phrenic nerve stimulation and stimulation of the lower thoracic nerve roots.|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Twitch transdiaphragmatic pressure in response to supramaximal magnetic stimulation of the phrenic nerve roots | Recording of twitch transdiaphragmatic pressure (Unit: Pressure in cmH2O) | 1 year | 
| Respiratory mouth pressures | Measurement of respiratory (inspiratory and expiratory) mouth pressures (Unit: Pressure in cmH2O) | 1 year | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Diaphragm ultrasound | Comprehensive evaluation of diaphragm excursion (amplitude during tidal breathing, sniff maneuver and maximal inspiration in cm, corresponding velocity in cm/sec, respectively) and thickening on ultrasound (thickness at functional residual capacity, at total lung capactiy in cm), Markers of Diaphragm excursion and thickening will be combined to classify diaphragm function as normal, mildly, moderately or severly impaired. | 1 year | 
| Exercise intolerance | Comprehensive evaluation of symptoms (breathlesness based on NYHA class, on a visual scale ranging from 1-10, respectively) and exercise capacity (6 minute walking distance). These measurements will be combined to classifiy patients as presenting with exercise intolerance or no exercise intolerance. | 1 year | 
| Lung function | Comprehensive assessment of lung function by bodyplethysmography (most importantly forced vital capacity, forced expiratory volume after 1 second, intrathoracic gas volume, residual volume) and capillary blood gas analysis (most importantly pO2 in mmHG and pCO2 in mmHG). These measurements will be combined to classify patients as showing normal, restrictive, obstructive lung function impairment, as being hypoxic, hypercapnic, respectively. | 1 year | 
| EMG | Diaphragm and accessory respiratory muscle electromyography | 1 year | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Respiratory muscle functtion