Healthy volunteers breathe thin air for science

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion criteria * Have a photo identification (ID) * Male or female individuals age between 18 and 40 years old * BMI between 19 and 24.9 kg/m2 * Having capacity to consent to the study Exclusion criteria * Evidence of any physical, mental, and/or medical conditions that would make the proposed studies relatively more hazardous * Prior high altitude pulmonary edema (HAPE) or high-altitude cerebral edema (HACE) diagnosis * Born at altitudes greater than 2,100 m (\~7,000 ft) * Systemic disease with or without any functional limitation; including * controlled hypertension * controlled diabetes without systemic effects * Pregnancy determined by urine pregnancy test, detecting presence of human chorionic gonadotropin (hCG), or less than six weeks postpartum * Women who are not willing to receive urine pregnancy tests * Active smoking. Volunteers may be enrolled if they quit smoking for more than 1 year. * Excess alcohol use: more than ½ L/day of wine consumption or equivalent * Any current medication use except oral contraceptives. * Living in areas that are more than 1,200 m (\~4,000 feet), or have traveled to areas that are more than 1,200 m for more than four days within the last 2 months * Tobacco chewers * Abnormal hemoglobin or hematocrit levels or presence of hemoglobin S * Evidence of apnea or other sleeping disorders * Evidence of asthma * Lower respiratory infection within the last 30 days * If applicable, unwilling to refrain from using energy drinks or other caffeinated beverages for 7 days prior to and during the study * If applicable, unwilling to refrain from use of all over-the-counter oral medications, herbal remedies, and nutritional supplements for 7 days prior to and during the study * Not willing to have blood drawn from an arm vein each test day of the study * Claustrophobia (inability to wear a facemask) or other active psychiatric conditions or not willingness to cooperate with the investigators and the other medical team * Currently enrolled in another research study * Facial abnormalities that would preclude proper use of a face mask Pregnancy Prevention/Testing: Women using oral, subdermal or injectable contraceptives, and those using other means of birth control may participate. A urine pregnancy test will be conducted as part of the screening process for study participation no more than 7 days before starting the study. The test result will be read by a female staff member who will keep the result confidential. If a woman declines to have a pregnancy test, she will not be able to participate.