An observational study in Patent Foramen Ovale (PFO) and High Altitude Pulmonary Edema, sponsored by University of Texas Southwestern Medical Center. Not yet recruiting. Open to participants aged 18 Years to 60 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-08-03.
Sponsored by University of Texas Southwestern Medical Center · Observational
Before birth, the foramen ovale is a normal opening in the heart that allows blood to flow from the mother to the baby. After birth, this opening usually closes. However, in up to 38% of the population it does not fully close and is then called a patent foramen ovale (PFO). Having a PFO allows venous (blue) blood to mix with arterial (red) blood in the heart, which can lower blood oxygen levels. The mixing of blood has been suggested to be greater during exercise and with exposure to high-altitude. Also, people with a PFO may be a greater risk for severe altitude sickness, specifically involving the collection of fluid in the lungs which makes breathing very difficult - this is called high-altitude pulmonary edema (HAPE).
No study has directly measured the pressure difference across the heart which is required for the mixing of blood during exercise or at high-altitude. The present study will directly measure the pressure difference across the heart, as well as blood flow through the PFO during rest and exercise in simulated high altitude in adults with and without a PFO and a previous history of severe altitude sickness. The study will test the hypothesis that elevations in pulmonary artery pressure during exposure to hypoxia will not elicit a pressure gradient, and thus blood flow, across the PFO neither at rest nor during exercise.
136 studies on the registry are indexed under Foramen Ovale, Patent; 47 are open to participants now.
This study's planned enrollment of 50 is below the median of 254 across 59 observational studies indexed under Foramen Ovale, Patent.
Browse Foramen Ovale, Patent studies →University of Texas Southwestern Medical Center is the lead sponsor of 1,010 studies on the registry; 199 are open to participants now.
Of its 139 completed or terminated interventional studies of FDA-regulated products, 105 (76%) have results posted.
Counted across the registry records on this site, refreshed daily.
Individuals with documented history of high-altitude pulmonary edema and with or without a patent foramen ovale
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Adults with documented history of high-altitude pulmonary edema and a patent foramen ovale
Adults with documented history of high-altitude pulmonary edema
Transmural pressure
Absolute difference between pulmonary capillary wedge pressure and right atrial pressure
Time frame: During 5 minutes of rest in normoxia, after 15 minutes of exercise in normoxia, after 90 minutes of rest in hypoxia, after 15 minutes of exercise in hypoxia.
Arterial oxygen saturation
Time frame: During 5 minutes of rest in normoxia, after 15 minutes of exercise in normoxia, after 90 minutes of rest in hypoxia, after 15 minutes of exercise in hypoxia.
Pulse oxygen saturation
Time frame: During 5 minutes of rest in normoxia, after 15 minutes of exercise in normoxia, after 90 minutes of rest in hypoxia, after 15 minutes of exercise in hypoxia.
Gas exchange
Oxygen uptake and carbon dioxide production
Time frame: During 5 minutes of rest in normoxia, after 15 minutes of exercise in normoxia, after 90 minutes of rest in hypoxia, after 15 minutes of exercise in hypoxia.
Arterio-venous oxygen different
Time frame: During 5 minutes of rest in normoxia, after 15 minutes of exercise in normoxia, after 90 minutes of rest in hypoxia, after 15 minutes of exercise in hypoxia.
Cardiac output
Time frame: During 5 minutes of rest in normoxia, after 15 minutes of exercise in normoxia, after 90 minutes of rest in hypoxia, after 15 minutes of exercise in hypoxia.
Right ventricular diameter
Time frame: During 5 minutes of rest in normoxia, after 15 minutes of exercise in normoxia, after 90 minutes of rest in hypoxia, after 15 minutes of exercise in hypoxia.
Tricuspid regurgitant jet velocity
Time frame: During 5 minutes of rest in normoxia, after 15 minutes of exercise in normoxia, after 90 minutes of rest in hypoxia, after 15 minutes of exercise in hypoxia.
Tricuspid annular plane systolic excursion
Time frame: During 5 minutes of rest in normoxia, after 15 minutes of exercise in normoxia, after 90 minutes of rest in hypoxia, after 15 minutes of exercise in hypoxia.
No study locations are listed for this record.
Plan to share: No
No publications or documents are linked to this record.
This study is not yet recruiting, as verified in Jul 2026. You cannot join it, but the record below documents what was studied.
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University of Texas Southwestern Medical Center →