Ahpra registration PHY0002298174
How these guides are written and reviewed →
After major surgery the lungs do not work as well for a while. Breathing is shallow, the cough is weak and painful, and parts of the lung collapse. Sometimes this progresses to a chest infection that keeps a person in hospital longer, or worse. This page is about who that happens to, why, and what genuinely reduces the risk — which turns out to be far more about what happens before the operation than after it.
What counts as a post-operative pulmonary complication
"Post-operative pulmonary complication" (PPC) is an umbrella term, not a diagnosis, and the definition problem is not academic — reported incidence ranges from under 2% to over 40% across studies largely because of what each study chose to count.1 A trial that counts only pneumonia will find a low rate; one that counts any radiographic atelectasis will find a high one.
Two definitions dominate. The Melbourne Group Scale requires four or more of eight criteria and is the standard in Australian physiotherapy trials; it is deliberately set to capture clinically meaningful events rather than radiological findings alone.2 The European Perioperative Clinical Outcome definitions and the later consensus work of the StEP-COMPAC group instead define each complication separately — respiratory infection, respiratory failure, pleural effusion, atelectasis, pneumothorax, bronchospasm, aspiration pneumonitis — which makes trials comparable but individually less sensitive.3,4
| Melbourne Group Scale criterion | Threshold |
|---|---|
| Chest radiograph | Atelectasis or consolidation |
| Temperature | >38 °C on more than one consecutive day |
| Oxygen saturation | SpO2 <90% on room air on more than one consecutive day |
| Sputum | Purulent, and different from pre-operative |
| Microbiology | Positive sputum culture |
| Medical diagnosis | Pneumonia or chest infection recorded by the treating team |
| White cell count | >11.2 × 109/L, otherwise unexplained |
| Escalation | Readmission to, or prolonged stay in, a high-dependency or intensive care unit for respiratory reasons |
Four or more criteria on any single post-operative day constitutes a PPC. Note what the scale does not do: a single day of desaturation, or radiographic basal atelectasis alone, does not meet it. That is intentional.
Why they happen
The mechanism is mechanical before it is infective, and understanding the order matters because it is what makes prevention plausible.
Every effective preventive intervention acts at step 1, 2 or 4. Almost nothing acts usefully at step 5 except antibiotics.
Who is at risk
Risk is dominated by two factors that are known before the patient reaches theatre: the site of the incision and the state of the patient. Surgical site is the single strongest predictor — risk rises steeply as the incision approaches the diaphragm.
| Factor | Comment |
|---|---|
| Surgical site | Thoracic and upper abdominal highest; lower abdominal intermediate; peripheral low. This outweighs almost every patient factor. |
| Duration of anaesthesia | Risk climbs beyond roughly two hours and again beyond three.3,5 |
| Age | A graded effect from around 50 years, independent of comorbidity. |
| Pre-operative SpO2 | An ARISCAT variable and an easy bedside marker — ≤95% on room air raises risk substantially.3 |
| Respiratory infection in the preceding month | A strong, and often the only modifiable, reason to defer elective surgery.3 |
| Smoking | Current smoking raises risk; cessation helps most when achieved several weeks pre-operatively. |
| Chronic lung disease, poor exercise capacity, low albumin, anaemia | Each contributes; predicted VO2max and respiratory comorbidity were independent predictors in the Australian cohort work.5 |
| Emergency surgery | Removes the opportunity for the intervention with the best evidence — see below. |
The ARISCAT score combines age, pre-operative SpO2, respiratory infection within a month, anaemia, surgical site, duration and urgency into a validated three-tier risk estimate, and is the most practical stratification tool for a physiotherapy service deciding who to see.3
What actually prevents them
A single pre-operative session
This is the strongest result physiotherapy has in peri-operative care, and it is worth stating precisely. LIPPSMAck-POP randomised 441 adults awaiting elective upper abdominal surgery to either an information booklet alone, or the booklet plus one 30-minute pre-operative physiotherapy session teaching breathing exercises and, critically, why and how to do them immediately after waking.2 The incidence of PPC was halved — 12% versus 27% — giving a number needed to treat of 7. Hospital-acquired pneumonia fell correspondingly.
Two features of that trial are routinely misread. First, the effect came from the education session, not from a course of post-operative treatment; the intervention was delivered before the operation and the post-operative care was the same in both arms. Second, the comparator was not "nothing" — it was a booklet. The active ingredient appears to be a person explaining the task and rehearsing it, not the information itself.
Citing LIPPSMAck-POP to justify a daily post-operative treatment round is not what the trial tested. If a service has finite physiotherapy hours, this evidence argues for moving them into the pre-admission clinic, not for adding post-operative contacts.
Early mobilisation
Getting patients upright and walking early is the intervention with the broadest support across enhanced-recovery literature, and it acts on FRC, secretion clearance, and venous thromboembolism risk simultaneously.6 It is also the element of Enhanced Recovery After Surgery (ERAS) protocols most often documented as prescribed and least often achieved in practice. Where a choice must be made, mobilising a patient out of bed is a better use of the contact than a set of breathing exercises performed in bed.
Inspiratory muscle training
Pre-operative IMT reduces PPC after cardiac and major abdominal surgery in meta-analysis, though the trials are heterogeneous and mostly small.7 It is a reasonable addition where a patient has weeks rather than days before surgery, and it pairs naturally with the pre-operative education contact.
Anaesthetic and analgesic strategy
Lung-protective intra-operative ventilation, avoidance of long-acting neuromuscular blockade without reversal, and regional analgesia that permits deep breathing and coughing all reduce PPC.8 These are not physiotherapy decisions, but inadequate analgesia is the single most common reason a physiotherapy treatment fails, and escalating it is a legitimate physiotherapy recommendation.
What does not work, or works less than believed
- Incentive spirometry. Cochrane review found no evidence of benefit for preventing PPC after upper abdominal surgery.9 It is not harmful, and it has a role in specific settings, but it should not displace mobilisation. See Incentive Spirometry for the full picture, including the one indication where it clearly does work.
- Routine post-operative chest physiotherapy for all-comers. Where early mobilisation and adequate analgesia are already in place, adding routine breathing exercises for every patient has not shown consistent benefit. Targeting the high-risk group is a better use of the resource.
- Prophylactic antibiotics for retained secretions. Treats step 5 while leaving steps 1–4 untouched.
Managing an established complication
Once a PPC has developed, the assessment question is which problem is actually present — they are managed differently and are frequently conflated:
| Problem | Clues | Priority |
|---|---|---|
| Loss of lung volume | Reduced breath sounds without added sounds, basal shadowing, desaturation, no sputum | Volume: mobilisation, positioning, deep-breathing or non-invasive support. Not suction. |
| Sputum retention | Coarse crackles clearing with cough, audible secretions, weak or painful cough, productive of purulent sputum | Analgesia first, then humidification, clearance technique and cough support |
| Consolidation / pneumonia | Fever, raised inflammatory markers, bronchial breathing, purulent sputum | Medical treatment; physiotherapy only if secretion retention coexists |
| Pleural effusion | Stony dullness, absent breath sounds at the base, meniscus on imaging | Medical/surgical drainage — no technique will clear it |
The last row is the one most often missed on a post-operative ward round, and treating it as sputum retention wastes the session and tires the patient.
Role of the physiotherapist
The highest-value physiotherapy contribution to PPC is delivered before the incision: identifying the high-risk patient, delivering the pre-operative education session, and setting the expectation that the patient will be sitting out and walking on day one. After surgery, the priorities are analgesia advocacy, early mobilisation, accurate differentiation of the four problems above, and escalation when oxygenation is failing rather than persisting with a technique that is not working.
See also Pre-Surgical Rehabilitation, Post-Surgical Rehabilitation and, for the chest that has already collapsed, Atelectasis.
Evidence summary
Framing. PPCs account for more post-operative morbidity, prolonged stay and 30-day mortality than cardiac complications after major abdominal and thoracic surgery, and the literature has shifted decisively over the past decade from post-operative treatment towards pre-operative risk modification and intra-operative protection.1,8 For physiotherapy this is an uncomfortable but clarifying shift: the discipline's strongest single trial result is a pre-operative one.
Evidence — pre-operative physiotherapyLIPPSMAck-POP is the anchor trial: pragmatic, multicentre, blinded outcome assessment, 441 patients, PPC halved with a single pre-operative session and a number needed to treat (NNT) of 7.2 Effect sizes of this magnitude from a 30-minute intervention are rare, and the result has held up in subsequent implementation work. The mechanism is presumed to be a combination of skill rehearsal and expectation-setting rather than any physiological training effect — which is consistent with the absence of a dose-response signal.
Evidence — bundles and ERASMeta-analysis of peri-operative interventions supports lung-protective ventilation, goal-directed fluid therapy, regional analgesia and early mobilisation as a bundle, with individual component effects difficult to isolate.8 ERAS pathways consistently reduce length of stay and complications; the respiratory component is rarely the element driving the effect, and physiotherapy services should be wary of claiming it.6
Physiotherapy implicationsStratify with ARISCAT or an equivalent, and concentrate resource on the high-risk tier rather than distributing it evenly. Move contacts pre-operatively wherever elective pathways allow. Post-operatively, prioritise mobilisation over bed-based breathing exercises, treat inadequate analgesia as a treatable cause of physiotherapy failure, and differentiate volume loss from secretion retention from effusion before selecting a technique.
Evidence gapsThe pre-operative effect has been demonstrated most robustly in elective upper abdominal surgery; its transfer to thoracic, cardiac and emergency populations is assumed more than shown. The optimal content and minimum effective dose of the pre-operative session are undefined, as is whether telehealth delivery preserves the effect. There is no adequately powered trial of targeted versus universal post-operative physiotherapy in a contemporary ERAS setting.
References & evidence base
- Miskovic A, Lumb AB. Postoperative pulmonary complications. Br J Anaesth 2017;118(3):317–334.
- Boden I, Skinner EH, Browning L, et al. Preoperative physiotherapy for the prevention of respiratory complications after upper abdominal surgery (LIPPSMAck-POP): pragmatic, double blinded, multicentre randomised controlled trial. BMJ 2018;360:j5916.
- Canet J, Gallart L, Gomar C, et al. Prediction of postoperative pulmonary complications in a population-based surgical cohort (ARISCAT). Anesthesiology 2010;113(6):1338–1350.
- Abbott TEF, Fowler AJ, Pelosi P, et al. A systematic review and consensus definitions for standardised endpoints in perioperative medicine: pulmonary complications. Br J Anaesth 2018;120(5):1066–1079.
- Scholes RL, Browning L, Sztendur EM, Denehy L. Duration of anaesthesia, type of surgery, respiratory co-morbidity, predicted VO2max and smoking predict postoperative pulmonary complications after upper abdominal surgery: an observational study. Aust J Physiother 2009;55(3):191–198.
- Ljungqvist O, Scott M, Fearon KC. Enhanced Recovery After Surgery: a review. JAMA Surg 2017;152(3):292–298.
- Katsura M, Kuriyama A, Takeshima T, et al. Preoperative inspiratory muscle training for postoperative pulmonary complications in adults undergoing cardiac and major abdominal surgery. Cochrane Database Syst Rev 2015;(10):CD010356.
- 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.
- do Nascimento Junior P, Módolo NSP, Andrade S, et al. Incentive spirometry for prevention of postoperative pulmonary complications in upper abdominal surgery. Cochrane Database Syst Rev 2014;(2):CD006058.
References are numbered in citation order (Vancouver/BMJ style) and were current at the time of writing. Guidelines are living documents — verify against the latest version before clinical use.
Physiotherapy around major chest, cardiac and upper abdominal procedures — from open surgery to bronchoscopic, catheter-based and bedside treatments — aims to reduce chest complications and shorten the return to normal function.
Corrections: If something on this page is wrong, out of date or unclear, we want to know. Email reception@inspireclinic.au with the page name and what you believe is incorrect. Substantive corrections are made promptly, and the guide’s version and last-updated date are changed to reflect it.