The goal of this observational study is to ascertain the practice patterns and predictors in performing lung protective ventilation as per clinical guidelines for adult patients undergoing non-cardiac surgery in Fraser Health Authority, a large Canadian authority in the lower mainland of British Columbia, Canada. In particular, the investigators explore changes before/after the COVID-19 pandemic. The main questions it aims to answer are:

• In this population, what is the general compliance rate to lung protective ventilation
• In this population, what are the predictors of compliance before/after the COVID-19 pandemic.

This is a retrospective study using linked patient data from two databases in the health region: the anesthesia informational management system for intraoperative data, and the electronic medical record for perioperative data.

Rationale for study:

Breathing problems after surgery affect 5% to 33% of patients and can lead to serious issues like lung infections, breathing failure, and longer hospital stays, with up to a 20% risk of death within 30 days for serious cases. A proven way to reduce these risks is lung protective ventilation (LPV), a technique used during surgery where the ventilator delivers smaller breaths based on clinical guidelines and calculated using a person's ideal body weight, while applying gentle pressure to keep the lungs slightly open. While this approach has been widely adopted in intensive care units over the past 20 years, it's less commonly used in operating rooms, with fewer than half of surgeries using it. Barriers include suboptimal default ventilator settings, patients at extremes of weight, and misunderstandings of LPV among clinicians. During the COVID-19 pandemic, LPV use increased for patients with COVID-related lung problems, showing improved survival rates in ICUs. However, it's unclear if this practice carried over to surgical patients at-large or continued after the pandemic. Most studies on LPV during surgery have been conducted outside Canada, where healthcare practices and education may differ from within Canada. To address these gaps, the investigators aim to study LPV use during surgery in a large Canadian health system, identify factors that influence its use, and examine trends during and after the COVID pandemic. This research will help improve patient care by promoting the use of this effective technique in Canadian operating rooms.

This observational study aims to elucidate the patterns and predictors of intraoperative lung protective ventilation (LPV) in adult patients undergoing non-cardiac surgery at Fraser Health Authority, a large Canadian health authority on the west coast of Canada, between 2014-2023. It also assesses the impact of pre-COVID vs. 2020s era on LPV compliance, and interactions of predictors with pre-COVID vs. 2020s era. LPV is defined as both 1) tidal volume of 6-8mL/kg ideal body weight and 2) positive end-expiratory pressure of 5 cmH2O or more. Intraoperative data will be derived from the intraoperative anesthesia information management system, and the perioperative data from the regional electronic medical record. The investigators will use a predictive logistic regression model to ascertain statistically significant predictors to LPV. Hypothesized predictors of LPV compliance based on literature and expert opinion will be considered for inclusion in the model. Pre-COVID and 2020s data will be compared, and interactions with predictors will be explored. As a secondary analysis, a Shewhart chart will be used to elucidate any special cause variation in LPV compliance introduced by the COVID pandemic. For details of descriptive analyses, model derivation, and Shewhart chart methodology, please refer to study protocol.

Inclusion Criteria:

• over the age of 18
• underwent general anesthesia with endotracheal tube placement for a procedure lasting ≥30 minutes.
• included in both our clinical anesthesia record database and the National Surgical Quality Improvement Program (NSQIP) database, and linkable by usual identifiers (name, date of birth, medical record number, personal health number, date of surgery)

Exclusion Criteria:

• no endotracheal tube utilized
• cardiothoracic surgery
• organ donation surgery
• organ transplant recipient
• Hyperthermic intraperitoneal chemotherapy
• surgical procedure related to an occurrence or complication of prior procedure during the same admission/within 30 days,
• multiple NSQIP assessed cases within 30 days only for same patient
• cases in clinical anesthesia record database that are unable to be linked to NSQIP data or vice versa.

Patients from January 2014 to December 2023, age above 18, undergoing non-cardiac and non-thoracic surgery for greater than 30 minutes with an endotracheal tube placed. Both inpatients and outpatients are eligible.

Individual patient data (IPD) is obtained from medical record registries at Fraser Health Authority. While IPD used in this study will not be shared, these data (and similar data at other time frames) are freely available to investigators of subsequent proposed studies, in collaboration with an investigator at Fraser Health Authority, through the usual data access application mandated by Fraser Health Authority.