Altitude, High-altitude Adaptation, Hypoxia, Immunosuppression, Lung Transplantation, Microbiota, Oxygen Saturation Measurement, Physical Fitness
Conditions
Brief summary
This prospective observational study investigates the effects of intermittent hypoxic conditioning and real high-altitude exposure in lung transplant recipients compared with healthy controls. The study includes an eight-week home-based preparatory phase during which participants use a normobaric hypoxic tent with reduced oxygen concentration. Prior to this phase, all participants receive standardized training on the safe use of the equipment. During the preparatory period, daily vital parameters, including heart rate, oxygen saturation, and heart rate variability, are recorded using a sports watch and a pulse oximeter. Symptoms, adverse events, and subjective well-being are documented daily in an electronic diary. All data are transmitted to the study team via encrypted electronic systems, allowing continuous remote monitoring. At the end of the preparatory phase, participants undergo a clinical evaluation to confirm fitness for the expedition phase. The expedition phase consists of a monitored ascent of Aconcagua (6,971 meters). Before departure, all participants are required to attend a comprehensive safety, protection, and first aid training conducted jointly by the study team and professional expedition providers. The expedition is planned and led by an experienced international expedition company in cooperation with a local provider specializing in high-altitude mountaineering. The expedition includes arrival in Mendoza, preparatory procedures such as equipment checks and permits, followed by a staged ascent to base camp. Subsequent days involve rest periods and acclimatization hikes with the establishment of progressively higher camps. A summit attempt is planned after sufficient acclimatization, followed by descent to high camp. A weather-dependent buffer period is included before the final descent to the valley and return to Mendoza, where the expedition concludes. Total study participation is expected to last approximately 15 weeks, including about eight weeks of home-based preparation and approximately three weeks at altitude. A final follow-up examination is conducted 2 to 4 weeks after completion of the expedition, marking the end of study participation.
Interventions
None listed
Sponsors
Medical University of Vienna
Study design
Observational model
COHORT
Time perspective
PROSPECTIVE
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
Yes
Inclusion criteria
Lung transplant recipients: * Age ≥ 18 years * \> 1 years after lung transplantation * Stable lung function over 6 month prior to inclusion, FEV1 +/-10% from baseline * VO2peak of more than 25 ml/min/kg * Physical and mental fitness, defined as the ability to complete strenuous day trips lasting 8 to 10 hours independently without suffering from a fear of heights, an altitude exposure of at least 2500m must be confirmed. * Negative pregnancy test for women of childbearing age * Written informed consent Healthy volunteers: * Age ≥ 18 years * VO2peak of more than 25 ml/min/kg * Physical and mental fitness, defined as the ability to complete strenuous day trips lasting 8 to 10 hours independently without suffering from a fear of heights * Negative pregnancy test for women of childbearing age * Written informed consent
Exclusion criteria
Lung transplant recipients: * Age \< 18 years * Refusal to participate in the study * Pregnancy Healthy controls: * Age \< 18 years * Refusal to participate in the study * Pregnancy * Chronic obstructive pulmonary disease (COPD)
Design outcomes
Primary
| Measure | Time frame |
|---|---|
| Change in forced expiratory volume in one second (FEV₁) | From enrollment to the end of the expedition at 3 weeks |
| Change in peripheral oxygen saturation (SpO₂) as a marker of physiological adaptation | From enrollment to the end of the expedition at 3 weeks |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Heart Rate Variability (HRV) | From enrollment to the end of the expedition at 3 weeks | — |
| Blood gas analysis (BGA) | From enrollment to the end of the expedition at 3 weeks | — |
| Acute mountain sickness (AMS) | From enrollment to the end of the expedition at 3 weeks | — |
| Level of immunosuppression | From enrollment to the end of the expedition at 3 weeks | — |
| Level of Torque Teno Virus (TTV) | Before enrollment until approx. 4 weeks after the end of the expedition | — |
| Voice analysis | Prior to enrollment to the end of the expedition at 3 weeks | Voice-based heart failure detection developed by Noah Labs uses artificial intelligence to analyze short voice recordings from patients with heart failure. Patients regularly record a standardized speech sample using a smartphone. Deep-learning algorithms extract numerous acoustic features such as frequency patterns and subtle variations in vocal cord vibration. The system identifies these changes as "voice biomarkers" and compares them with previous recordings. If patterns suggest worsening heart failure, clinicians can be alerted early, potentially allowing timely therapeutic adjustments and preventing hospitalizations. The study aims to investigate changes in height and in patients following lung transplantation. |
| Gut Microbiota Dynamics | Prior to enrollment to the end of the expedition at 3 weeks | The composition of the gut microbiota is being studied longitudinally using stool samples collected prior to the expedition and following successive ascents to high altitudes over the course of several weeks. The samples are analyzed to determine bacterial diversity and taxonomic composition. Microbial diversity indices, including Shannon, Simpson, and Chao1, are calculated to assess changes in community structure. In addition, the Bray-Curtis distance and the Jaccard index are used to assess differences in species distribution across time points. The relative abundance of bacterial taxa is quantified to identify shifts in pathogenic and beneficial microbial populations during altitude exposure. |
| Transthoracic echocardiography | Prior to enrollment to the end of the expedition at 3 weeks | — |
| Lung Ultrasound Score | Prior to enrollment to the end of the expedition at 3 weeks | — |
| Renin-angiotensin-aldosterone system | Prior to enrollment to the end of the expedition at 3 weeks | — |
| End-tidal CO₂ measurements | Prior to enrollment to the end of the expedition at 3 weeks | — |
| Continuous glucose monitoring | Prior to enrollment to the end of the expedition at 3 weeks | — |
Countries
Austria
Outcome results
None listed