Respiratory Muscles After Hospitalisation for COVID-19

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 especially following invasive mechanical ventilation in the Intensive Care Unit. The aim of the project is to measure respiratory muscle function and strength in our respiratory physiology laboratory (Respiratory Physiology Laboratory, Department of Pneumology and Intensive Care Medicine, Head: Professor Michael Dreher) in patients who survived a severe COVID-19-infection (25 with a severe course requiring mechanical ventilation in the intensive care unit, 25 with a moderate-severe course requiring administration of supplemental oxygen only, respectively). Based on this data the aim is to develop a model which determines the severity, pathophysiology and clinical consequences of respiratory muscle dysfunction in patients who had been hospitalised for COVID-19. This will potentially prove the importance of a dedicated pulmonologic rehabilitation with respiratory muscle strength training in patients who had been hospitalised for COVID-19.

Detailed Description
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The aim of the present project is to comprehensively measure respiratory muscle function and strength in patients who survived a hospitalisation for a severe COVID-19-infection (25 with a severe course requiring mechanical ventilation in the intensive care unit, 25 with a moderate-severe course requiring administration of supplemental oxygen only, respectively). We intend to recruit 50 patients during their regular follow up appointments (12 months and 24 months after their discharge from the hospital) in our pulmonology outpatient-clinic. Patients fulfilling the criterions of inclusion and exclusion will be included. Patients will undergo a series of measurements on one day in our respiratory physiology laboratory (Respiratory Physiology Laboratory, Department of Pneumology and Intensive Care Medicine, Head: Professor Michael Dreher). Patients will be asked to complete a questionnaire, followed by some examinations comprising spirometry by bodyplethysmography, exercise endurance, capillary blood gas analyses, measurement of maximum inspiratory and expiratory mouth pressures, dynamometric measurement of arm and leg strength, diaphragm ultrasound, magnetic stimulation of the phrenic and lower thoracic nerves with invasive recording of twitch transdiaphragmatic pressure and markers of systemic inflammation based on in depth analyses of blood samples that will be obtained. Based on this data the aim is to develop a model which determines the severity, pathophysiology and clinical consequences of respiratory muscle dysfunction in patients who had been hospitalised for COVID-19. This will potentially prove the importance of a dedicated pulmonologic rehabilitation with respiratory muscle strength training in patients who had been hospitalised for COVID-19.

Official Title
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Respiratory Muscle Function After Hospitalisation for COVID-19 -Pathophysiological Model on Severity, Determinants and Clinical Consequences of Respiratory Muscle Strength Impairment in Patients Who Had Been Hospitalised for COVID-19-

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: 50 patients with survived COVID-19-infection (25 with a severe course requiring mechanical ventilation in the intensive care unit, 25 with a moderate-severe course requiring administration of supplemental oxygen only, respectively) Patients aged at least 18 years, who are mentally and physically able to consent and participate into the study Exclusion Criteria: Diagnosis of another disease, which causes a permanent increase in carbon dioxide level in the blood (chronic hypercapnia) or a permanent combined lung weakness (particularly a neuromuscular disease) 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 Patients who are mentally and physically unable to consent and participate into the study Patients in an interdependence or with an employment contract with the principal investigator, Co-PI or his deputy. Emergency hospital stay in the last 4 weeks preceding the day of the measurements

Ages Eligible for Study
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Minimum Age: 18 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) | 2 years | 
| Respiratory mouth pressures | Measurement of respiratory (inspiratory and expiratory) mouth pressures (Unit: Pressure in cmH2O) | 2 years | 

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. | 2 years | 
| 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. | 2 years | 
| Analyses of markers of systemic inflammation (interleukin levels in ng/ml, TNF alpha in ng/ml, CRP in mg/L; immune phenotyping of inflammatory cells, most importantly whilte blood cell subtypes in %) | Analyses of markers of systemic inflammation based on blood samples taken. These measurements will be combined to classify patients as having increased or normal levels of systemic inflammation. | 2 years | 
| 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. | 2 years |