TABLE A2.

Model Features

Types of EHR Data	Feature	Observation Windowa
Demographics	Continuous: age	NA
	Binary: male, White, Hispanic, married
Diagnosis codesb	Number of all diagnosis records, number of unique diagnosis codes	All historical data leading to surgical case request time
	Number of all diagnosis records for respiratory problems, number of unique diagnosis codes for respiratory problems
Cancer treatment	Number of days on radiation treatment	1 year leading to surgical case request time
	Number of chemotherapy and immunotherapy medication orders
Previous inpatient admissions and outpatient visits	Total hospital length of stay, number of inpatient admissions, number of outpatient visits	1 year leading to current hospital admission time
Medication administration records	Number of all medication orders	30 days leading to surgical case request time
	Number of medication orders for each therapeutic class: anti-infective agents, antineoplastic agents, endocrine and metabolic drugs, cardiovascular agents, respiratory agents, GI agents, genitourinary products, CNS drugs, analgesics and anesthetics, neuromuscular drugs, nutritional products, hematologic agents, topical products, miscellaneous products, unknown classc
Oxygenation support	Highest oxygenation support leveld	30 days leading to surgical case request time
	Number of days on oxygenation support, number of oxygenation support records	1 year leading to surgical case request time
	Most recent values: FiO2, flow rate, PEEP, PIP, tidal volume	Most recent values
Vital signs	Most recent values: systolic blood pressure, diastolic blood pressure, heart rate, respiratory rate, SpO2, temperature, weight	Most recent values
Laboratory tests	Most recent values: albumin, alkaline phosphatase, calcium, creatinine (blood), glucose, hematocrit, hemoglobin, lactate, lymphocytes percent, platelet, prothrombin time, RBC, RDW, segmented neutrophils percent, sodium, total bilirubin, WBC	Most recent values
	Number of laboratory test results, number of normal laboratory test results, number of abnormal laboratory test results, percentage of abnormal laboratory test results	90 days leading to surgical case request time

Abbreviations: BiPAP, bilevel positive airway pressure; CPAP, continuous positive airway pressure; EHR, electronic health record; FiO2, the fraction of inspired oxygen; NA, not available; PEEP, positive end-expiratory pressure; PIP, peak inspiratory pressure; RDW, red blood cell distribution width; SpO2, oxygen saturation by pulse oximetry.

^aFeatures were created within the observation window and aggregated at the operation level.

^bDiagnosis codes related to respiratory problems (eg, acute respiratory failure, pleural effusion, pneumonia, etc) were identified by clinical experts.

^cOrders that did not have therapeutic class assigned in the EHR were grouped to unknown class.

^dThe oxygenation support level was coded as no oxygenation support/room air = 0, face mask = 1, nasal cannula = 2, CPAP/BiPAP = 3, others = 4, ventilator = 5.