One-lung ventilation

Surgical approach

Common operations requiring OLV: thoracotomy, VATS (lobectomy/segmentectomy), pneumonectomy, oesophagectomy (thoracic phase), mediastinal surgery, lung volume reduction, thoracic aortic surgery
Patient positioning: usually lateral decubitus (operative side up), table flexion; occasionally supine for anterior mediastinal/robotic approaches
Surgeon requests: lung collapse on operative side; may insufflate CO2 in some VATS/robotic cases; may intermittently clamp pulmonary vessels/bronchus
Key surgical moments affecting physiology: opening pleura (loss of negative pressure), retraction/compression of dependent lung, pulmonary artery clamping, bronchial stump leak testing, mediastinal manipulation (arrhythmias), conversion VATS→thoracotomy, major bleeding

Anaesthetic management

Type of anaesthesia: General anaesthesia with lung isolation; regional analgesia adjunct (thoracic epidural, paravertebral, erector spinae plane, serratus anterior plane) depending on procedure and local practice
Airway: Double-lumen tube (DLT) most common; alternatives: single-lumen ETT + bronchial blocker; rarely Univent; SGA not suitable when lung isolation required
Monitoring: standard + arterial line (common), large-bore IV access; consider CVC if major resection/poor access; consider urinary catheter for long cases; temperature monitoring
Duration: typically 2–6 hours (VATS often shorter; oesophagectomy/complex resections longer)
Pain: moderate–severe (thoracotomy highest; VATS moderate). Multimodal analgesia essential to facilitate breathing/cough and reduce pulmonary complications
Ventilation strategy during OLV: lung-protective (VT ~4–6 mL/kg predicted body weight), avoid high plateau pressures, appropriate PEEP to dependent lung; permissive hypercapnia often acceptable if haemodynamics stable

Definition and aims

OLV = ventilation of one lung while the other is isolated and allowed to collapse (or intermittently ventilated) to facilitate surgery and/or protect the healthy lung
Aims: provide surgical exposure, prevent contamination (blood/pus), allow differential ventilation, permit bronchial/airway surgery

Indications (core FRCA list)

Surgical exposure: VATS/thoracotomy lung resections, oesophagectomy (thoracic phase), mediastinal surgery
Protection from contamination: massive haemoptysis, unilateral infection/bronchiectasis, lung abscess, broncho-pleural fistula
Differential ventilation: unilateral air leak, giant bullae, bronchopleural fistula, unilateral compliance differences
Airway procedures: bronchial sleeve resection, tracheo-bronchial surgery, bronchopleural fistula repair

Physiology of OLV: oxygenation and shunt

Key problem: increased right-to-left shunt through non-ventilated lung → hypoxaemia
Hypoxic pulmonary vasoconstriction (HPV): intrinsic mechanism diverting blood away from hypoxic alveoli; reduces shunt and improves PaO2 during OLV
- Time course: onset within minutes; maximal effect ~15–30 min; biphasic (early then sustained phase)
- Magnitude: can reduce blood flow to non-ventilated lung by ~30–50% (variable)
Determinants of oxygenation during OLV: fraction of cardiac output perfusing non-ventilated lung, dependent lung V/Q matching, FiO2, airway pressures, lung pathology, position
Lateral position effects: dependent lung better perfused (gravity) but may be less ventilated (compression/atelectasis) → V/Q mismatch; non-dependent lung less perfused but non-ventilated → shunt
Opening chest/pleura reduces FRC and promotes atelectasis; retraction and surgical manipulation worsen dependent lung ventilation

Factors affecting HPV (commonly examined)

Inhibit/attenuate HPV (worsen shunt): high pulmonary artery pressures, alkalosis, high mixed venous PO2, vasodilators (e.g. nitroprusside, GTN), some volatile anaesthetics (dose-dependent), excessive PEEP to ventilated lung (if it diverts blood back to non-ventilated lung)
- Volatiles: isoflurane/sevo/des can inhibit HPV in a dose-dependent manner; clinically modest at ≤1 MAC, but relevant if high concentrations and other factors present
Augment/preserve HPV: IV anaesthesia (e.g. propofol), mild hypercapnia, avoidance of excessive airway pressures, maintaining normal acid-base and temperature
Other important modifiers: cardiac output (very high CO can worsen shunt; very low CO reduces SvO2 and can worsen arterial oxygenation), anaemia reduces CaO2 even if SpO2 acceptable

Preoperative assessment (thoracic focus)

History: exercise tolerance, dyspnoea, cough/sputum, haemoptysis, previous thoracic surgery, OSA, reflux/aspiration risk, smoking, chemo/radiotherapy, anticoagulants
Investigations: spirometry (FEV1), DLCO, ABG if indicated, CXR/CT, ECG ± echo if pulmonary HTN/right heart disease, CPET if major resection
Predicted postoperative function: ppoFEV1 and ppoDLCO (segment counting or perfusion scan); higher risk if ppoFEV1 or ppoDLCO <40% (thresholds vary by guideline)
Optimisation: bronchodilators, treat infection, smoking cessation, physiotherapy, consider prehab; plan postoperative destination (HDU/ICU) and analgesia

Devices for lung isolation

Double-lumen tube (DLT): fastest reliable isolation, allows suctioning/CPAP to non-ventilated lung, easier switching between OLV and two-lung ventilation
- Left DLT generally preferred (more forgiving anatomy; right upper lobe take-off makes right DLT positioning more critical)
- Sizing (adult typical): women 35–37 Fr, men 39–41 Fr (adjust to height/airway; confirm with leak/pressures and fibreoptic view)
Bronchial blocker (via single-lumen ETT): useful in anticipated difficult airway, existing ETT/tracheostomy, paediatrics, need for postoperative ventilation
- Limitations: slower lung collapse, harder suctioning of operative lung, displacement risk, less effective CPAP delivery, may obstruct upper lobe depending on position
Univent tube: single-lumen tube with integrated blocker; less commonly used
Absolute requirement: fibreoptic bronchoscopy to confirm position after insertion and after positioning

Technique: DLT placement and confirmation (exam sequence)

Preparation: check cuffs, lubricate, have fibreoptic scope ready, suction, capnography, plan for difficult airway (videolaryngoscope, bougie, airway exchange catheter)
Insertion: laryngoscopy, pass DLT through cords with stylet, remove stylet, rotate 90° toward intended bronchus (left for left DLT), advance to depth (often ~27–29 cm at teeth; varies with height)
Initial checks: bilateral chest movement on two-lung ventilation, capnography, cuff pressures (avoid overinflation), auscultation (limited reliability)
Fibreoptic confirmation (gold standard): confirm bronchial lumen in correct main bronchus, bronchial cuff just below carina, unobstructed upper lobe bronchi; repeat after lateral positioning and after any desaturation/airway pressure change

Ventilation strategy during OLV

FiO2: start 1.0 for transition to OLV; then titrate down if stable to reduce absorption atelectasis/oxygen toxicity (often remain high in practice)
Tidal volume: 4–6 mL/kg predicted body weight; avoid volutrauma
Pressures: aim plateau <25 cmH2O (context-dependent); avoid excessive peak pressures; accept permissive hypercapnia if appropriate
PEEP to dependent lung: individualise (e.g. 5 cmH2O then titrate). Too little → atelectasis; too much → overdistension and worsened V/Q (and may worsen shunt by diverting blood to non-ventilated lung)
Recruitment manoeuvres: to dependent lung after disconnections or if atelectasis suspected; reassess haemodynamics and pressures
Mode: volume or pressure control acceptable; pressure control may limit peak pressures but does not guarantee lung protection; focus on VT, plateau, driving pressure, and oxygenation/CO2

Management of hypoxaemia during OLV (stepwise algorithm)

Define problem: SpO2 falling (e.g. <90%) or PaO2 low; act early
Immediate actions: increase FiO2 to 1.0; check haemodynamics; ensure adequate Hb and cardiac output; deepen anaesthesia if bronchospasm/coughing
Check equipment and tube position (most common correctable cause): suction both lumens, check circuit, check DLT/blocker with fibreoptic bronchoscopy (after positioning, surgical manipulation, or if high airway pressures)
- Common DLT issues: bronchial cuff herniation over carina, endobronchial migration, right upper lobe obstruction (esp. right DLT), secretions/blood plugging
Optimise dependent lung ventilation: recruitment manoeuvre, titrate PEEP (consider PEEP trial), ensure VT 4–6 mL/kg PBW and avoid overdistension; treat bronchospasm
Reduce shunt from non-ventilated lung: apply CPAP 1–5 cmH2O with O2 to non-dependent lung (if surgical field allows); ensure minimal interference with surgery
If still hypoxaemic: intermittent two-lung ventilation (ask surgeon to pause), or clamp/ligate pulmonary artery earlier if appropriate (surgical decision)
Consider contributing pathology/physiology: low CO, anaemia, pneumothorax in dependent lung, pulmonary oedema, aspiration, malposition after retractor placement

Haemodynamic considerations and fluids

OLV and lateral position can reduce venous return; high intrathoracic pressures worsen this; monitor closely (arterial line helpful)
Right ventricular strain: hypoxia/hypercapnia and high airway pressures increase PVR; avoid severe hypoxaemia, acidosis, excessive PEEP
Fluids: aim euvolaemia; avoid excessive crystalloid (risk pulmonary oedema/ARDS, especially post-pneumonectomy). Use goal-directed approach where available

Analgesia (thoracic emphasis)

Thoracic epidural: excellent analgesia for thoracotomy; risks include hypotension, urinary retention, failure, epidural haematoma (anticoagulation considerations)
Paravertebral block: comparable analgesia for many thoracic procedures with less hypotension; can be single-shot or catheter
Erector spinae plane (ESP) / serratus anterior plane: easier/safer in some settings; variable dermatomal spread; useful for VATS
Multimodal: paracetamol, NSAID (if appropriate), opioid (often PCA), adjuncts (ketamine, magnesium, gabapentinoids selectively), antiemetics

Extubation vs postoperative ventilation

Aim for extubation when feasible: awake, warm, good gas exchange on two-lung ventilation, adequate analgesia, haemodynamic stability, acceptable surgical status (air leak/bleeding)
Indications for postoperative ventilation/ICU: major resection, poor preop lung function, ongoing bleeding, severe hypoxaemia/hypercapnia, haemodynamic instability, difficult airway, significant comorbidity
If postoperative ventilation anticipated: consider bronchial blocker + single-lumen ETT strategy, or exchange DLT to single-lumen ETT with airway exchange catheter at end

You are asked to provide one-lung ventilation for a VATS lobectomy. How will you assess and plan the anaesthetic?

Structure: patient factors → surgical factors → airway plan → monitoring/lines → ventilation/analgesia → postoperative plan.

Patient assessment: exercise tolerance, COPD/asthma, smoking, sputum, haemoptysis, OSA, reflux; previous thoracic surgery; anticoagulants
Investigations: spirometry (FEV1), DLCO, CT/CXR, ECG ± echo; consider ABG/CPET for major resections; estimate ppoFEV1/ppoDLCO
Airway plan: left DLT vs ETT+blocker; difficult airway strategy (VL, AEC); fibreoptic bronchoscope mandatory
Monitoring/lines: arterial line, good IV access; consider CVC; temperature; urinary catheter if long case
Ventilation plan: OLV lung-protective (VT 4–6 mL/kg PBW, plateau <25), titrated PEEP, recruitment; plan for hypoxaemia algorithm
Analgesia: VATS—paravertebral/ESP/serratus + multimodal ± PCA; thoracotomy—consider thoracic epidural
Postop: extubation criteria; HDU/ICU planning; chest drain considerations; physiotherapy and nausea prevention

Explain why hypoxaemia occurs during one-lung ventilation and how the body compensates.

Non-ventilated lung continues to receive perfusion → right-to-left shunt → reduced PaO2
HPV diverts blood away from hypoxic alveoli to ventilated lung, reducing shunt fraction and improving oxygenation
Lateral position: gravity increases perfusion to dependent lung; however anaesthesia/surgery reduce dependent lung ventilation (atelectasis/compression) worsening V/Q

List the factors that inhibit hypoxic pulmonary vasoconstriction and explain the clinical relevance during OLV.

Volatile agents inhibit HPV in a dose-dependent manner (clinically modest at ≤1 MAC but additive with other causes of hypoxaemia)
Pulmonary vasodilators (GTN, nitroprusside, PDE inhibitors), high pulmonary artery pressures, alkalosis, high mixed venous PO2, excessive airway pressures/overdistension affecting perfusion distribution
Clinical relevance: inhibition increases perfusion of non-ventilated lung → increased shunt → lower PaO2; manage by optimising ventilation/perfusion and avoiding unnecessary HPV inhibitors

How do you confirm correct placement of a left-sided double-lumen tube with a fibreoptic bronchoscope?

Confirm tracheal lumen view: carina visible; bronchial cuff not herniating across carina
Confirm bronchial lumen view: left main bronchus entered; left upper and lower lobe bronchi patent; bronchial cuff just below carina
Repeat after lateral positioning and after any change in compliance/oxygenation or surgical manipulation

A patient desaturates to SpO2 85% shortly after starting OLV. Talk through your management in order.

Prioritise reversible causes: oxygenation, tube position, ventilation strategy, shunt reduction, then escalation.

Increase FiO2 to 1.0; check pulse oximeter trace; assess haemodynamics; call for help early if severe/rapid
Check circuit and ventilation: confirm capnography, airway pressures, delivered VT; suction lumens
Fibreoptic bronchoscopy to confirm DLT/blocker position (most common cause); correct malposition
Recruit dependent lung and optimise PEEP (trial titration); treat bronchospasm; ensure adequate depth and muscle relaxation
Apply CPAP 1–5 cmH2O with O2 to non-dependent lung if surgeon can tolerate; consider apnoeic oxygen insufflation as alternative
If unresolved: intermittent two-lung ventilation; discuss with surgeon (pause, adjust retraction, consider clamping pulmonary artery if appropriate)
Consider other diagnoses: pneumothorax of dependent lung, pulmonary oedema, aspiration, endobronchial obstruction with blood, low cardiac output/anaemia

Compare a double-lumen tube with a bronchial blocker: advantages, disadvantages, and when you would choose each.

DLT advantages: reliable isolation, faster collapse, easy suctioning/CPAP to operative lung, easier switching between OLV and two-lung ventilation
DLT disadvantages: larger external diameter (airway trauma), more difficult insertion in difficult airway, usually needs exchange if postoperative ventilation required
Blocker advantages: can be placed through standard ETT (useful in difficult airway/tracheostomy), easier to continue postoperative ventilation without exchange
Blocker disadvantages: slower collapse, harder suctioning, displacement risk, CPAP less effective, positioning can be tricky (esp. upper lobe obstruction)
Choice: DLT for most elective thoracic cases; blocker when difficult airway anticipated/confirmed, already intubated, paediatric, or postoperative ventilation likely

What ventilator settings would you start with for OLV in an adult and why?

VT 4–6 mL/kg predicted body weight to reduce volutrauma; adjust to maintain acceptable CO2
RR adjusted for minute ventilation; accept permissive hypercapnia if haemodynamically stable
PEEP ~5 cmH2O then titrate to oxygenation/compliance; avoid overdistension
FiO2 initially 1.0 during transition; then titrate if stable; monitor SpO2/ABG
Pressure limits: aim plateau <25 cmH2O where possible; monitor driving pressure and haemodynamics

Why is a left-sided DLT usually preferred? When would you use a right-sided DLT?

Left DLT preferred because left main bronchus is longer and left upper lobe take-off is less likely to be obstructed; positioning is more forgiving
Right DLT may be required if left main bronchus pathology prevents placement (tumour, stenosis, distortion), left pneumonectomy/left bronchial surgery where left bronchus must be free
Right DLT caveat: must align ventilation slot with right upper lobe bronchus; malposition can obstruct RUL causing hypoxaemia

How does CPAP to the non-dependent lung improve oxygenation during OLV, and what are the downsides?

CPAP provides oxygen to non-ventilated alveoli, reducing shunt by improving alveolar oxygenation and allowing some oxygen transfer without full ventilation
Downsides: can impair surgical exposure (lung inflation), may increase risk of air trapping if partial obstruction, may be difficult to deliver effectively with blockers

Describe the main causes of high airway pressure during OLV and how you would manage them.

Tube problems: DLT malposition, kinking, secretions/blood plug, bronchial cuff overinflation → suction and fibreoptic check; adjust cuff volumes
Bronchospasm: treat with deepening anaesthesia, bronchodilators, consider steroids; check triggers (light anaesthesia, secretions)
Reduced compliance: dependent lung atelectasis, retraction, pulmonary oedema → recruitment, optimise PEEP, consider diuresis if appropriate, discuss with surgeon re retraction
Ventilator settings: excessive VT/PEEP → reduce VT, titrate PEEP, accept higher CO2 if safe

Outline a safe plan if you anticipate a difficult airway but still need lung isolation for thoracic surgery.

Primary aim: secure airway with a single-lumen ETT first (using VL/awake technique as indicated), then add lung isolation with a bronchial blocker under fibreoptic guidance
Alternative: intubate with standard ETT then exchange to DLT over an airway exchange catheter if appropriate and safe; maintain oxygenation throughout
Always: have a failed airway plan; consider awake fibreoptic intubation if high risk; ensure skilled assistance and equipment

What are the key postoperative complications associated with OLV and thoracic surgery, and how can anaesthesia reduce them?

Pulmonary: atelectasis, pneumonia, respiratory failure, bronchospasm, air leak, pulmonary oedema/ARDS (esp. after major resection)
Cardiovascular: arrhythmias (AF), RV strain, myocardial ischaemia
Reduce risk: lung-protective ventilation, avoid fluid overload, excellent analgesia enabling deep breathing/cough, early mobilisation, PONV prevention, smoking cessation, physiotherapy