Respiratory Muscle Strength in Patients With Obesity Hypoventilation Syndrome (OHS) or With a Precursor of the Disease

Study Overview
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Brief Summary
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Using an extensive set of both volitional and non-volitional tests of respiratory muscle function and strength it is the aim of this study to identify potential determinants for the development of obesity hypoventilation to identify predictors for the presence of a sleep-related hypoventilation requiring treatment in obese patients

Official Title
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Multimodal Measurement of Respiratory Muscle Strength by Using Volitional and Non-volitional Tests in Patients With Obesity Hypoventilation Syndrome (OHS), Obesity-associated Hypoventilation and OHS-Risk-Patients to Evaluate Pathophysiological Determinants and Predictors for the Presence of a Sleep-related Hypoventilation Requiring Treatment in Obese Patients

Conditions
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Obesity Hypoventilation Syndrome

Intervention / Treatment
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* Diagnostic Test: magnetic phrenic nerve stimulation


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: patients with BMI > 30 and obesity-associated hypoventilation stages I - IV patients with BMI > 30 and elevated OHS-risk (= obstructive sleep apnea without hypercapnia) age:18-80 years capacity to consent Exclusion Criteria: any other disease, that causes ventilatory insufficiency pacemaker, defibrillators or device for deep brain or vagus nerve stimulation esophagitis, Barrett-esophagus, esophageal cancer acute gastritis and ulcera ventriculi epilepsy any medical, psychological or other condition impairing the patient's ability to provide informed consent

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 80 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

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| OHS or elevated OHS-risk (stages 0-IV)<br>stage 0: OHS-risk (OSA / no hypercapnia) stage I: obesity associated hypoventilation (intermittent hypercapnia during sleep, arterial carbon dioxide partial pressure (PaCO2) or transcutaneous carbon dioxide partial pressure (PtcCO2) morning   evening), bicarbonate < 27 mmol/L awake) stage II: obesity associated hypoventilation (intermittent hypercapnia during sleep, PaCO2 or PtcCO2 morning > evening, bicarbonate ≥ 27 mmol/L awake) stage III: OHS (hypercapnia, carbon dioxide partial pressure (PCO2) > 45 mmHg awake) stage IV: OHS with end organ damage (hypercapnia , PCO2 > 45 mmHg awake, cardiometabolic comorbidities) diagnostic tests: magnetic phrenic nerve stimulation, diaphragmatic ultrasound | Diagnostic Test: magnetic phrenic nerve stimulation<br>* cervical and cortical stimulation of N. Vagus<br>* Other names: capnography;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Carbon dioxide rebreathing test | minute volumen (L/min) | 1 day | 
| transdiaphragmatic pressure (non-volitional) | difference between intraesophageal and intragastral pressure after posterior magnetic stimulation of the phrenic nerves | 1 day | 
| peripheral nervous system (non-volitional) | electroneurography after posterior magnetic stimulation of the phrenic nerves | 1 day | 
| diaphragmal ultrasound - excursion (non-volitional) | excursion of the diaphragm | 1 day | 
| diaphragmal ultrasound - thickness (non-volitional) | thickness of the diaphragm | 1 day | 
| P0.1 (volitional) | mouth occlusion pressure (kPa) | 1 day | 
| PImax (volitional) | maximal inspiratory mouth pressure (kPa) | 1 day | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Comparison of PImax and transdiaphragmatic pressure | Correlation between PImax and transdiaphragmatic pressure | 1 day |