 Methods Design: This is an observational cohort study which will be conducted at McMaster childrens hospital, pediatric critical care unit PCCU. Children under 18 years of age, admitted to PCCU, who require respiratory support by HHFNC, as determined by the caring physician; and informed consent and or assent of substitute decision maker. Those children must have NG tube of size 10 French or smaller inserted at time of HHFNC application. Patients who are on intermittent NGT suction will be excluded. Airway pressure will be measured indirectly using esophageal pressure liquid filled method. 