Inclusion Criteria:  age between 18-40 years, body mass index between 19 and 30 kg/m^2, resident at a similar altitude for a minimum of 1-year, no travel to/from areas varying by ~2000 feet of elevation within 4-weeks of initiation of study participation.  Exclusion Criteria:  identification of overt chronic disease (including cardio-pulmonary disorders), prior diagnosis of asthma, cystic fibrosis, Chronic obstructive pulmonary disease, or ventilator therapy anemia, pregnancy, habitual use of tobacco/nicotine products, known allergy to sodium phosphate (or other common laxatives), habitual use of recreational drugs that require inhalation, history of seizures, kidney problems, stomach or bowel problems, ulcerative colitis, problems with swallowing or gastric reflux, gout, and and/or low blood sodium. irritable bowel ACUTE respiratory illness such as bronchitis, pneumonia, Upper Respiratory Infection OR ACUTE GI issues such as gastroenteritis. Anemia (as measurement of hemoglobin and/or hematocrit) . sickle cell disease. history of altitude sickness