Inclusion Criteria:  healthy adult men and women; 18-45 years of age; BMI 18-30 kg/m2; non-pregnant/non-breastfeeding; non-nicotine users;  Exclusion Criteria:  taking any medications known to affect metabolic, respiratory, cardiovascular, and/or autonomic  Self-reported history of:  hepatic, renal, pulmonary, cardiovascular, or neurological disease; stroke or neurovascular disease; bleeding/clotting disorders; sleep apnea or other sleep disorders; diabetes; smoking; history of alcoholism or substance abuse; hypertension; respiratory disease; active cancer; autoimmune disease.