Inclusion Criteria:  Age between 2 years and 20 years inclusive Written informed consent provided by a parent or legal guardian Admitted to Duke Children's Hospital for primary reason of asthma exacerbation (and treated with methylprednisolone) BMI-percentile greater than 95th for obese subjects and BMI less than 95th percentile for non-obese subjects  Exclusion Criteria:  Patients with suspected liver failure, renal failure, sepsis, or cardiopulmonary instability deemed by the PI. Receiving any extracorporeal life support including extracorporeal membrane oxygenation, ventricular assist devices, and renal replacement therapy at enrollment Any condition or circumstance that, in the opinion of the investigator, would compromise the safety of the participant or the quality of the data.