How can intra‑operative bronchospasm be recognized in an intubated patient?

Recognizing Intra-Operative Bronchospasm in an Intubated Patient

Intra-operative bronchospasm in an intubated patient is recognized primarily through a combination of increased peak airway pressures, characteristic capnography changes (upsloping expiratory plateau or "shark fin" pattern), difficulty with manual ventilation, and decreased oxygen saturation—with capnography and airway pressure monitoring serving as the earliest and most reliable indicators. 1

Primary Monitoring Modalities

Airway Pressure Monitoring (First-Line Indicator)

Airway pressure monitoring should be used during controlled ventilation and provides breath-by-breath information about chest-lung mechanics. 1

• Increased peak inspiratory pressure is one of the earliest signs of bronchospasm in mechanically ventilated patients 1
• Monitor peak, plateau, mean, and end-expiratory airway pressures, ideally displayed as a waveform 1
• Rising peak pressures with normal plateau pressures suggest increased airway resistance (bronchospasm) rather than decreased lung compliance 1
• Audible alarms should be enabled and set appropriately for the individual patient 1

Capnography (Gold Standard for Ventilation Monitoring)

Capnography has numerous monitoring roles including detecting bronchospasm or other lung pathology. 1

• Waveform capnography is essential at all times in patients with tracheal tubes and serves as a vital monitor of airway patency and alveolar ventilation 1
• The characteristic capnography pattern in bronchospasm shows an upsloping expiratory plateau (often called "shark fin" appearance) due to prolonged expiratory phase and incomplete alveolar emptying 1
• Elevated end-tidal CO2 (ETCO2) may occur as CO2 clearance becomes impaired 2
• Uninterrupted capnography monitoring should occur during induction, maintenance, transfers, and emergence from anesthesia 1

Spirometry and Flow-Volume Loops

Display and skilled interpretation of spirometry loops enables rapid detection of changes in lung mechanics. 1

• Combining pressure, flow, and volume measurements provides breath-by-breath spirometry on modern anesthetic machines 1
• Decreased expiratory flow rates and prolonged expiratory time are characteristic of bronchospasm 1
• Although not mandatory, spirometry provides valuable early warning of deteriorating lung mechanics 1

Clinical Signs and Physical Examination

Ventilation Difficulty

• Difficulty with manual bag-valve ventilation with increased resistance felt by the anesthesia provider 3
• Decreased tidal volumes despite adequate ventilatory effort 1
• Decreased minute ventilation if not corrected 1

Auscultation Findings

• Bilateral expiratory wheezing over lung fields, though this may be a late finding 1
• Decreased or absent breath sounds if severe bronchospasm causes near-complete airway obstruction 1
• Listen over the axillae for best assessment of peripheral lung sounds 1

Oxygenation Changes (Late Indicator)

• Decreased oxygen saturation (SpO2) is a late indicator of bronchospasm, occurring after significant ventilation-perfusion mismatch develops 2, 4
• Pulse oximetry may remain falsely reassuring initially, especially with supplemental oxygen 2
• Progressive hypoxemia indicates severe bronchospasm requiring immediate intervention 4, 3

Systematic Approach Using the DOPE Mnemonic

If an intubated patient's condition deteriorates, consider the DOPE mnemonic to systematically evaluate potential causes: 1

• Displacement of the tube (verify with capnography and direct laryngoscopy if needed) 1
• Obstruction of the tube (pass suction catheter to verify patency) 1, 3
• Pneumothorax (assess for unilateral breath sounds, subcutaneous emphysema) 1
• Equipment failure (disconnect from ventilator and manually ventilate with bag-valve) 1, 3

Bronchospasm should be considered after ruling out these mechanical causes. 3

Algorithmic Recognition Strategy

Step 1: Immediate Assessment

• Note sudden increase in peak airway pressures on ventilator display 1
• Observe capnography waveform for upsloping expiratory plateau 1
• Assess difficulty with manual ventilation if hand-bagging 3

Step 2: Verify Tube Position and Patency

• Confirm positive wave-formed capnography (rules out esophageal intubation) 1, 3
• Pass suction catheter through endotracheal tube to verify patency 1, 3
• Consider direct or video laryngoscopy if tube position uncertain 1, 3

Step 3: Rule Out Mechanical Causes

• Disconnect from ventilator and manually ventilate with 100% oxygen 3
• Check for equipment failure (kinked tubing, closed APL valve, filter obstruction) 1, 3
• Auscultate for unilateral breath sounds suggesting pneumothorax or mainstem intubation 1

Step 4: Diagnose Bronchospasm

• If bilateral wheezing, increased airway pressures, characteristic capnography pattern, and mechanical causes excluded, diagnose bronchospasm 1, 4, 3
• Consider fiberoptic bronchoscopy if diagnosis remains uncertain 1, 3

Important Clinical Pitfalls

Delayed Recognition

• Relying solely on pulse oximetry will delay recognition as oxygen saturation drops late in the course of bronchospasm 2
• Capnography and airway pressure changes occur minutes before oxygen desaturation 2

Misdiagnosis

• Bronchospasm can mimic tube obstruction, pneumothorax, or equipment failure—systematic evaluation using DOPE mnemonic prevents misdiagnosis 1, 3
• In cases of profound bronchospasm, capnography may show reduced CO2 detection, potentially mimicking esophageal intubation—skilled use of flexible bronchoscopy helps differentiate 1

Inadequate Monitoring

• Failure to use continuous waveform capnography is a preventable error that delays bronchospasm recognition 1
• Not displaying airway pressure waveforms limits early detection of rising pressures 1

Special Considerations

Patient Risk Factors

• Bronchospasm is more common in patients with asthma, COPD, or reactive airway disease, but can occur in patients without specific respiratory disorders 4
• Tracheal irritants like sputum, blood, or secretions can trigger bronchospasm 4
• Histamine-releasing drugs or anaphylaxis should be considered as potential causes 4

Severity Assessment

• Severe bronchospasm manifests as very high peak pressures (often >40-50 cmH2O), profound hypoxemia, and near-complete inability to ventilate 3, 5, 6
• Refractory bronchospasm unresponsive to standard therapies requires escalation to advanced treatments 5, 7, 6