Postoperative respiratory failure (PRF) in this model is defined as need for mechanical ventilation for >48 hours after surgery or unplanned intubation within 30 days. The calculator was designed for preoperative use to estimate an individual patient’s PRF risk before major surgery.

Cohort	Data set	Patients (n)	PRF incidence	Discrimination
Derivation	ACS NSQIP 2007	211,410	3.1%	c-statistic 0.894
Validation	ACS NSQIP 2008	257,385	2.6%	c-statistic 0.897

The original Gupta study used ACS NSQIP 2007–2008 data from more than 468,000 adult surgical patients and retained five preoperative predictors: procedure category, emergency versus elective status, dependent functional status, preoperative sepsis/SIRS and higher ASA class. Patients who developed PRF had markedly higher 30-day mortality than those who did not.

Later perioperative reviews and guidelines cite the Gupta PRF calculator as a simple, fully preoperative pulmonary risk tool, often used alongside the companion Gupta postoperative pneumonia model and broader ACS NSQIP risk calculators. Its calibration in contemporary practice, non-NSQIP settings, day surgery, transplant, trauma and paediatric populations is uncertain, and it does not directly incorporate other important risk modifiers such as age, COPD, obesity, obstructive sleep apnoea, smoking history or existing pneumonia. These should be considered alongside the predicted percentage.

Use the estimate as a preoperative planning aid. Emergency deterioration, aspiration risk, airway difficulty and postoperative care resources may require higher-acuity planning than the percentage alone suggests.

Gupta Postoperative Respiratory Failure Risk