COPD is the most commonly identified risk factor for Postoperative Pulmonary Complications (PPCs). In large cohorts from the NSQIP database, patients with COPD had increased median length of stay, increased 30-day morbidity and increased 30-day mortality compared to those patients without COPD^1,2.

Low preoperative SpO₂ (while supine on room air) is a significant independent risk factor for PPCs. Compared with SpO₂ of 96%, patients with preoperative SpO₂ of 91-95% were twice as likely, and those with SpO₂ 90% were ten times more likely, to get a PPC³.

As no specific thresholds of lung function are mandated for non-thoracic surgery, the risk/benefit ratio for individual patients needs to be estimated. The indication for specific COPD treatment (e.g. bronchodilators, inhaled corticosteroids) remains the same as those for patients not preparing for surgery⁴:

Well-controlled asthma appears to confer little additional perioperative risk for severe morbidity from anaesthesia⁵.

The indication for specific treatment (e.g. bronchodilators, inhaled corticosteroids) remains the same as non-surgical patients⁶:

1. Gupta H, Ramanan B, Gupta PK, et al. Impact of COPD on postoperative outcomes: results from a national database. Chest. 2013:Jun; 143(6):1599-1606.
2. Fields AC, Divino CM. Surgical outcomes in patients with chronic obstructive pulmonary disease undergoing abdominal operations: An analysis of 331,425 patients. Surgery. 2016;Apr; 159(4):1210-6.
3. Canet J, Gallart L, Gomar C, et al. Prediction of postoperative pulmonary complications in a population-based surgical cohort. Anesthesiology 2010;113:1338-50.
4. Agusti A, Celli BR, Criner GJ, et al. Global Initiative for Chronic Obstructive Lung Disease 2023 Report: GOLD Executive Summary. Eur Respir J. 2023;61:2300239.
5. Warner DO, Warner MA, Barnes RD, et al. Perioperative Respiratory Complications in Patients with Asthma. Anesthesiology. 1996;85:460-467.
6. Global Initiative for Asthma. Global Strategy for Asthma Management and Prevention, 2023. Updated July 2023. Available from: www.ginasthma.org.

The reported incidence of PPCs is difficult to quantify; it ranges from <1% to 23% and varies depending on:

• Criteria used to define PPC
• Definition of the ‘perioperative period’
• Patient population
• Type of surgery performed, specific surgeon and hospital performing surgery
• Anaesthesia used.

To address the issue of differing definitions and outcome measures of PPCs within the research literature, several taskforces have attempted to standardise endpoints. To date, the definition of ARDS and pneumonia are more straightforward than one of a PPC that may include several criteria as demonstrated below.

1. European Society of Anaesthesiology and European Society of Intensive Care Medicine (ESA-ESICM) joint taskforce on perioperative outcome measures published a consensus statement: European Perioperative Clinical Outcome (EPCO) definitions². Their definitions of PPCs are shown in the table below:

2. Core Outcome Measures in Perioperative and Anaesthetic Care – Standardised Endpoints in Perioperative Medicine (StEP-COMPAC)³

• An international collaboration recommended 4 key PPCs endpoints for future perioperative clinical trials
• Included a new definition of PPCs
• Also included an assessment of severity within the definitions.

Risk prediction models are available to identify patients at high risk of PPC. This can inform optimal perioperative management.

ARISCAT: Assess respiratory risk in surgical patients in Catalonia⁴ is a screening tool in which a variable weighting is given to each of seven factors to provide a score that is then translated into a risk grading of low, medium or high for PPCs:

The quality of evidence supporting interventions that aim to reduce the risk of PPCs is variable⁵. Moderate quality evidence shows that intraoperative lung protective ventilation and goal-directed haemodynamic strategies may reduce PPCs.

Prophylactic respiratory education and breathing exercises have been shown to improve lung volumes assist with removal of pulmonary secretions, thereby reducing the risk of PPCs^6,7. Please refer to Universal exercise intervention for further information.

1. Miskovic A, Lumb AB. Postoperative pulmonary complications. Br J Anaesth. 2017; Mar 1;118(3):317-334.
2. Jammer I, Wickboldt N, Sander M, et al. Standards for definitions and use of outcome measures for clinical effectiveness research in perioperative medicine: European Perioperative Clinical Outcome (EPCO) definitions: a statement from the ESA-ESICM joint taskforce on perioperative outcome measures. Eur J Anaesthesiol 2015; 32: 88–105.
3. Abbott TEF, Fowler AJ, Pelosi P, et al. A systematic review and consensus definitions for standardised end-points in perioperative medicine: pulmonary complications. BJA. 2018;120(5):1066e1079.
4. Canet J, Gallart L, Gomar C, et al. Prediction of postoperative pulmonary complications in a population-based surgical cohort. Anesthesiology. 2010;113:1338–50.
5. Odor PM, Bampoe S, Gilhooly D, et al. Perioperative interventions for prevention of postoperative pulmonary complications: systematic review and meta-analysis. BMJ. 2020;368:m540.
6. Boden I, Skinner EH, Browning L, et al. Preoperative physiotherapy for the prevention of respiratory complications after upper abdominal surgery: pragmatic, double blinded, multicentre randomised controlled trial. BMJ. 2018;360:j5916. Erratum in: BMJ. 2019;365:l1862. PMID: 29367198; PMCID: PMC5782401.
7. Boden I, Denehy L. Respiratory Prehabilitation for the Prevention of Postoperative Pulmonary Complications after Major Surgery. Current Anesthesiology Reports. 2022;12.

Anaesthesia and sleep are different states of unconsciousness with considerable physiological similarities^1,2, including reductions in:

• Hypoxic and hypercapnic ventilatory drive
• Muscle activation
  • With preferential inhabitation of upper airway (UA) vs respiratory pump muscles & increased diaphragm dependence
• Cortical influences
  • With removal of volitional control and of the stimulatory effect of wakefulness
• Gain of UA pharyngeal and other load compensation reflexes
• Lung volume.

These physiological changes render the UA vulnerable to collapse and predispose to hypoventilation. These tendencies to UA collapse and hypoventilation in sleep and anaesthesia are related.

Increasing age and obesity rates are contributing to the higher prevalence of patients with OSA presenting for surgery. The global prevalence of OSA in the adult general population is 9-38% (higher in men of advancing age) when OSA is defined as disordered breathing present on a sleep study³. The overall prevalence among adult surgical patients ranges from 24% to 41%⁴.

Of concern, most cases of OSA remained undiagnosed (and therefore untreated) amongst adult patients at the time of presentation for elective surgery. The major international societal guidelines on perioperative OSA assessment and management – American Society of Anesthesiologists (ASA) and the Society of Anaesthesia and Sleep Medicine (SASM) – support OSA screening as part of standard pre-anaesthetic evaluation^5,6.

The optimal preoperative OSA screening and confirmatory test remains unclear. There are currently no Australian-based consensus guidelines for the perioperative evaluation or management of OSA; rather individual hospital networks often develop guidelines for use in patients admitted to hospital.

Once diagnosed, the Apnoea-Hypopnea Index (AHI) is an imperfect metric in predicting increased risk of postoperative compromise from OSA. An important preoperative metric translating into significantly higher rates of postoperative compromise is the hypoxaemia burden.

Most cases of morbidity and mortality from respiratory depression and ventilatory compromise are preventable. The optimal method for detecting patients at heightened risk of OSA-related complications remains poorly defined. An individualised risk evaluation is recommended and requires a balance between patient safety and finite hospital resources.

STOP-Bang questionnaire⁷

The following features and comorbidities may be present in those with OSA.

Surrogate markers:

• Resting hypoxaemia
• Hypercapnoea
• Elevated bicarbonate
• Polycythaemia.

Associated comorbidities:

• Elevated BMI
• Cardiovascular disease, e.g. hypertension, atrial fibrillation
• Respiratory disease, e.g. pulmonary hypertension.

Patients screened as high risk for OSA should be referred – either directly or via their primary care provider – for a sleep study.  Where the waiting lists for sleep studies are long, individual assessment of patient risk vs the urgency of the surgery need to be made on a case-by-case basis.

Once OSA is detected, treatment should ideally be instituted prior to surgery. The SASM guidelines recommend extending preoperative assessment to evaluate for comorbid ventilatory or gas exchange conditions, such as pulmonary hypertension, hypoventilation syndromes, and resting hypoxaemia in the absence of other cardiopulmonary pathology (GRADE: weak).

Perioperative management of OSA

Proceeding with surgery in unassessed or untreated patients must encompass evaluation of the potential severity of OSA, the extent of any comorbid conditions and the invasiveness of the surgical procedure.

Among patients with established OSA adherent with CPAP, the SASM guidelines⁶ support the postoperative continuation of CPAP therapy, unless specifically contraindicated (GRADE: strong); CPAP therapy after surgery has been shown to reduce the incidence of postoperative cardiopulmonary complications compared with patients with untreated OSA. If a patient has an oral appliance, this should similarly be used postoperatively.

1. Hillman DR, Chung F. Anaesthetic management of sleep-disordered breathing in adults. Respirology. 2017; Feb;22(2):230-239.
2. Eastwood PR, Szollosi I, Platt PR, et al. Comparison of upper airway collapse during general anaesthesia and sleep. Lancet. 2002; 359:1207-1209.
3. Senaratna CV, Perret JL, Lodge CJ, et al. Prevalence of obstructive sleep apnea in the general population: a systematic review. Sleep Med Rev. 2017; 34:70–81.
4. Vasu TS, Grewal R, Doghramji K, et al. Obstructive sleep apnea syndrome and perioperative complications: a systematic review of the literature. J Clin Sleep Med. 2012; 8(2):199–207.
5. American Society of Anesthesiologists Task Force on Perioperative Management of Patients With Obstructive Sleep Apnea. Practice guidelines for the perioperative management of patients with obstructive sleep apnea: an updated report by the American Society of Anesthesiologists Task Force on Perioperative Management of Patients with Obstructive Sleep Apnea. Anesthesiology 2014; 120:268–286.
6. Chung F, Memtsoudis SG, Ramachandran SK, et al. Society of Anesthesia and Sleep Medicine guidelines on preoperative screening and assessment of adult patients with obstructive sleep apnea. Anesth. Analg. 2016; 123(2):452–73.
7. Chung F, Abdullah HR, Liao P. STOP-Bang questionnaire: a practical approach to screen for obstructive sleep apnea. Chest. 2016; 149(3):631–638.

Tobacco smoking is a risk factor for perioperative pulmonary, cardiovascular, bleeding and wound healing complications^1,4. In active smokers, the incidence of Postoperative Pulmonary Complications (PPCs) increases incrementally with the number of pack-years smoked. Smoking is associated with a higher risk of red blood cell transfusion as a proxy for surgical bleeding across all surgical specialties combined².

Patients should be supported to stop smoking as soon as possible. The greater the duration of smoking cessation, the greater the benefit³:

• Smokers who quit >4 weeks before surgery had lower risks of respiratory complications than current smokers; the risk was lower still in those who quit >8 weeks before surgery
• The risk of wound healing complications was less in smokers who quit >3 weeks before surgery than in current smokers
• Short-term (<4 weeks) smoking cessation does not appear to reduce the risk of postoperative respiratory complications, however, smokers who quit <4 weeks before elective surgery do not have increased risks for respiratory or cardiovascular events.

The Ask, Advise, Help structure for supporting smoking cessation is a brief intervention developed by Quit Victoria and offers patients best practice smoking cessation treatment by linking into multi-session behavioural interventions (e.g. Quitline) and encouraging the use of pharmacotherapy.

The three-step brief intervention model can be summarised as follows:

• Ask and record smoking status
• Advise all people who smoke to quit and advise on the most effective methods
• Help by offering to arrange referral, encourage the use of behavioural intervention and use of evidence-based smoking cessation pharmacotherapy.

Options for behavioural support include the Australian Department of Health quit website (quit.org.au) or a tobacco treatment specialist (www.apsad.org.au).

1. Hawn MT, Houston TK, Campagna EJ, Graham LA, Singh L, Bishop M, Henderson, WG. The attributable risk of smoking on surgical complications. Annals of Surgery. 2011;254(6), 914–920.
2. Nordestgaard AT, Tølbøll TH, Sørensen HT. Smoking and risk of surgical bleeding: A nationwide analysis of 5,452,411 cases. Transfusion. 2020;60(8), 1689–1697.
3. Wong J, Abrishami A, Yang Y, Zaki A, Chung F. Short-term preoperative smoking cessation and postoperative complications: A systematic review and meta-analysis. Canadian Journal of Anesthesia 2012;59(3): 268–279.
4. Wong J, Lam DP, Abrishami A, Chan MTV, Chung F. Society for Perioperative Assessment and Quality Improvement (SPAQI) consensus statement on perioperative smoking cessation. Anesthesia & Analgesia. 2020;131(3):955–968.