The project will be pursued in our respiratory, autonomic nervous system physiology laboratory (Respiratory, autonomic nervous system physiology laboratory, Department of Pneumology and Intensive Care Medicine, RWTH Aachen University Hospital).

Overactivity of the sympathetic nerve activity (SNA) axis with "centrally" increased heart rate and peripheral vasoconstriction is a known phenomenon in patients with systolic heart failure (HF) and has recently been described in patients with primary lung diseases as in chronic obstructive pulmonary disease (COPD) and pulmonary hypertension (PH). Comprehensive studies investigating sympathetic drive in Asthma as one of the major pulmonary diseases are still lacking. Furthermore, the intention of this study is to determine the impact of Nasal High Flow Therapy (NHFT) on SNA and assess respiratory muscle function using state-of-the-art techniques.

Asthma, being one of the major pulmonary diseases affects roughly 300 million people worldwide. This disease leads to airflow obstruction within the lung following chronic inflammation of the respiratory tract, which results in a wide range of symptoms. Overactivity of SNA has been already linked to patients with systolic heart failure and COPD. The investigators postulate that similar pathomechanism is prevalent in Asthma which leads to an overactivity of SNA.

Nasal High Flow Therapy (NHFT) is a recently developed form of oxygen therapy that delivers heated and humidified high-flow oxygen and gas mix through a nasal cannula. In comparison to conventional oxygen therapy, NHFT has been proven substantially beneficial due to additional effects like decreased oxygen dilution, increased FRC, dead space washout with CO2 removal, increased mucociliary function and generation of positive end-expiratory pressure (PEEP) which lead to significantly improved breathing mechanics often preventing the need for invasive machine ventilation (IMV) in various acute diseases. Furthermore, these mechanisms lead to the bronchodilation of small airways in primary obstructive pulmonary diseases like COPD. Positive benefits of NHFT, not only during an acute exacerbation but also with long-term stable disease have been already established in COPD. Similar effects could be expected in bronchial Asthma characterized by obstruction of small airways.

Thus, using a comprehensive, multimodal approach and state-of-the-art technology, this research project is designed to determine the prevalence, extent and nature of increased SNA in Asthma (AIM 1) and evaluate the impact of NHFT on sympathovagal balance in patients (AIM 2).

The project will address the following hypotheses:

1. SNA is increased in asthma patients.
2. NHFT has a positive impact on the sympathetic drive resulting in decreased SNA.

Inclusion Criteria:

• Clinically diagnosed Asthma
• Age ≥ 18
• Ability and willingness to give informed consent to participate in the study

Exclusion Criteria:

• Atrial fibrillation
• Active pacing of the heart by a cardiac pacemaker (i.e. no intrinsic heart rate)
• Clinically pre-established cardiovascular disease or other pulmonary diseases (e.g. arterial hypertension, systolic heart failure, COPD)
• In-patient stay in the hospital within the last 4 weeks prior to the study examination date
• Severe polyneuropathy

Asthma patients (n=20) and Controls (n=10) patients without an established cardiovascular disease will be enrolled and the extent, nature and mechanism of SNA increase compared with healthy controls matched in a 2:1 ratio for age, sex and body mass index (BMI).