More and more people are engaging in sports in the mountains, including individuals with heart or lung diseases. At the same time, such diseases are becoming more common in Switzerland. At high altitude, less oxygen is available, which places stress on the body-particularly on the heart, which has to pump blood through the lungs. How the heart, especially the right ventricle, in people with asthma responds to this stress is still not well understood. Therefore, this study investigates how the heart responds to simulated altitudes of 2,500 m and 4,000 m, both at rest and during light physical activity in patients with asthma. The primary objective is to assess how right ventricular function changes under conditions of reduced oxygen availability. In addition, vital signs, changes in blood gases, oxygen levels in blood and tissue and shortness of breath are assessed. The "altitude" is simulated using a special gas mixture that participants inhale. Participants undergo three altitude conditions (490, 2,500, and 4,000 m above sea level). The order of the altitude conditions is assigned at random. The aim is to better understand how the right ventricle and other parameters respond to low-oxygen conditions and how affected patients can be better supported in the future.
Outdoor activities in the mountains are becoming increasingly popular. At higher altitudes, the air contains less oxygen, which puts extra strain on the body-especially on the heart. The right side of the heart plays a key role in pumping blood through the lungs and may need to work harder when oxygen levels are low. While the heart's response to long-term altitude exposure is relatively well known, much less is understood about how the heart reacts to short-term (acute) exposure to low oxygen, particularly during light physical activity and in individuals with asthma. This study aims to better understand how the right ventricle responds to short-term simulated altitude exposure. Participants with asthma will be exposed to different oxygen levels that correspond to altitudes of 490 m (near sea level), 2,500 m, and 4,000 m, both at rest and during light cycling exercise. The main focus of the study is to measure changes in right ventricular function, assessed using a non-invasive heart ultrasound technique called speckle-tracking echocardiography. In addition, heart rate, blood pressure, oxygen saturation, and symptoms such as shortness of breath and leg fatigue will be recorded. The study is conducted at a single center and uses a randomized, double-blind, cross-over design, meaning that each participant undergoes all altitude conditions in a random order, and neither the participants nor the investigators know which altitude is being simulated at a given time. Participants Only adults aged 18-80 years with diagnosed asthma bronchiale will be included. Participants must live below 800 m above sea level and must not have been exposed to higher altitudes for more than 24 hours in the three weeks before participation. Individuals with significant other medical conditions, pregnancy, need for long-term oxygen therapy, or inability to follow the study procedures will be excluded. Study procedures Each study visit includes: * 1 hour resting period * Measurement of vital signs (heart rate, blood pressure, oxygen saturation) * Heart ultrasound at rest * A 10-minute low-intensity cycling exercise * Repeated heart ultrasound during and symptom assessment after exercise * Low-oxygen conditions are created using a special gas mixture that participants breathe through a mask. Each condition is separated by at least 2 hours wash-out period to ensure recovery. Study size and duration Based on statistical calculations, 18 participants will be recruited to allow balanced allocation across all study conditions and to account for potential dropouts. Participation may take place over two to three days, depending on the preferred schedule of the participant. The days can be spread or be spread over several weeks, depending on individual availability. Aim of the study The goal of this study is to improve understanding of how the right side of the heart responds to short-term low-oxygen exposure at rest and during light exercise. This knowledge will help interpret future findings in patients with heart or lung disease and may contribute to safer recommendations for physical activity at altitude.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
DIAGNOSTIC
Masking
TRIPLE
Enrollment
18
Normobaric hypoxia according to 408m (control/normobaric normoxia), 2500 m and 4000 m above sea-level at rest for 1 hour and at low intensity cycling for 10 minutes (5 min 30 W, 5 min 60 W).
Consultant Clinic of Pulmonology, University Hospital of Zurich
Zurich, Canton of Zurich, Switzerland
Right ventricular free wall strain
The primary endpoint is defined as the right ventricular free wall strain (RVFWS) from condition normobaric normoxia to condition 4000m for group 1 and from normobaric normoxia to condition 2500m for group 2 at rest. RVFWS will be measured by speckle tracking strain analysis according to the guidelines of the European Association of Cardiology. Speckle tracking echocardiography allows to assess the right ventricular volume and true global RV function without relying on geometric assumption and is a valuable clinical bedside tool for assessing myocardial strain. Tomtec software (Philipps) will be used.
Time frame: It will be assessed once at baseline in rest and during each condition three times: Once after 1 hour in the specific condition at rest, then during the 5 min of 30 Watt cycling and during the 5 min of 60 Watt cycling.
Tricuspid annular plane systolic excursion (TAPSE)
Differences in tricuspid annular plane systolic excursion (TAPSE) \[cm\] between the conditions at rest and during exercise, measured according to the guidelines of the European Association of cardiology.
Time frame: It will be assessed once at baseline in rest and during each condition three times: Once after 1 hour in the specific condition at rest, then during the 5 min of 30 Watt cycling and during the 5 min of 60 Watt cycling.
Right ventricular-arterial coupling
Differences in TAPSE/sPAP and RVFWS/sPAP between the conditions at rest and during exercise, measured by echocardiography, as a validated, noninvasive measure of right ventricular-arterial coupling.
Time frame: It will be assessed once at baseline in rest and during each condition three times: Once after 1 hour in the specific condition at rest, then during the 5 min of 30 Watt cycling and during the 5 min of 60 Watt cycling.
RV/PA
Differences in RV/PA ratio between the conditions at rest and during exercise, measured by echocardiography according to the guidelines of the European Association of cardiology.
Time frame: It will be assessed once at baseline in rest and during each condition three times: Once after 1 hour in the specific condition at rest, then during the 5 min of 30 Watt cycling and during the 5 min of 60 Watt cycling.
Stroke volume
Differences in stroke volume based on the left ventricular outflow tract diameter and the velocity time integral over the aortic valve in the apical 5-chamber view or the apical long axis view \[ml\] between the conditions at rest and during exercise, measured by speckle tracking strain analysis according to the guidelines of the European Association of Cardiology.
Time frame: It will be assessed once at baseline in rest and during each condition three times: Once after 1 hour in the specific condition at rest, then during the 5 min of 30 Watt cycling and during the 5 min of 60 Watt cycling.
Heart rate
Differences in heart rate \[bpm\] and HRV between the conditions at rest and during exercise, continuously measured throughout the intervention by electrocardiogram connected to an Alice pdx.
Time frame: It will be assessed at baseline and continuously measured during each condition (1 hour resting period and during the 10 minutes cycling).
Blood pressure
Differences in blood pressure between the conditions at rest and during exercise, measured by a digital sphygmomanometer four times at rest and four times during low load cycling \[mmHg\] and continuously measured by a PPG-based Wrist-monitor (biobeat).
Time frame: It will be measured at baseline once and during each condition six times: Four times during the resting period (every 15 min) and two times during low load cycling.
Borg Rating of Perceived Exertion Scale (CR10)
Differences in Borg Rating of Perceived Exertion Scale (CR10) between the conditions at rest and during exercise. Measured through showing a paper with the 10 categories and the participant points to the according category which describes the current breathing difficulty.
Time frame: Measured at baseline and in each condition twice: Once at the end of the resting condition and again at the end of the cycling exercise.
Oxygen saturation
Differences in oxygen saturation \[%\] between the conditions at rest and during exercise, continuously measured throughout the intervention by an oximeter connected to an Alice pdx.
Time frame: It will be assessed at baseline and continuously measured during each condition (1 hour resting period and during the 10 minutes cycling).
Lung tissue oxygenation
Differences in lung tissue oxygenation between the conditions at rest and during exercise, assessed using near infrared spectroscopy (NIRS) continuously measured throughout the intervention according to our SOP.
Time frame: It will be assessed at baseline and continuously measured during each condition (1 hour resting period and during the 10 minutes cycling).
Brain oxygenation
Differences in brain oxygenation between the conditions at rest and during exercise, assessed using near infrared spectroscopy (NIRS) continuously measured throughout the intervention according to our SOP.
Time frame: It will be assessed at baseline and continuously measured during the 1 hour resting period during each condition, and during the 10 minutes cycling.
Respiratory effort
Differences in respiratory effort abdominal and chest using zRIP belts between the conditions at rest and during exercise connected to an Alice pdx.
Time frame: It will be assessed at baseline and continuously measured during each condition (1 hour resting period and during the 10 minutes cycling).
Multiomics profiles
Differences in multiomics profiles between the conditions at rest, assessed using mass spectrometry analysis of blood serum collected from venous blood from the V. antecubita, will be evaluated to determine the effects of acute hypoxia and group-specific responses.
Time frame: A blood sample will be collected during each condition after 1 hour of rest.
Arterial blood gas analysis
Differences in arterial blood gas analysis (ABGA) between the conditions at rest, collected through puncture of the A. radialis by a trained physician.
Time frame: A blood sample will be collected during each condition after 1 hour of rest.
Right ventricular size
Differences in right ventricular size between the conditions at rest and during exercise, measured according to the guidelines of the European Association of cardiology.
Time frame: It will be assessed once at baseline in rest and during each condition three times: Once after 1 hour in the specific condition at rest, then during the 5 min of 30 Watt cycling and during the 5 min of 60 Watt cycling.
End-diastolic diameter
Differences in end-diastolic diameter between the conditions at rest and during exercise, measured according to the guidelines of the European Association of cardiology.
Time frame: It will be assessed once at baseline and once during each condition after the resting period.
Fractional area change
Differences in fractional area change between the conditions at rest and during exercise, measured according to the guidelines of the European Association of cardiology.
Time frame: It will be assessed once at baseline in rest and during each condition three times: Once after 1 hour in the specific condition at rest, then during the 5 min of 30 Watt cycling and during the 5 min of 60 Watt cycling.
Maximal tricuspid regurgitation velocity
Differences in maximal tricuspid regurgitation velocity between the conditions at rest and during exercise, measured according to the guidelines of the European Association of cardiology.
Time frame: It will be assessed once at baseline in rest and during each condition three times: Once after 1 hour in the specific condition at rest, then during the 5 min of 30 Watt cycling and during the 5 min of 60 Watt cycling.
Pulmonary acceleration time
Differences in pulmonary acceleration time between the conditions at rest and during exercise, measured according to the guidelines of the European Association of cardiology.
Time frame: It will be assessed once at baseline and once during each condition after the resting period.
Diastolic dysfunction grade
Differences in diastolic dysfunction grade between the conditions at rest and during exercise, measured according to the guidelines of the European Association of cardiology.
Time frame: It will be assessed once at baseline and once during each condition after the resting period.
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