What are the signs and symptoms of pneumothorax in a patient under anesthesia, particularly in those with underlying lung disease or undergoing thoracic surgery?

Signs and Symptoms of Pneumothorax Under Anesthesia

In patients under anesthesia, pneumothorax presents with nonspecific cardiorespiratory decompensation—specifically tachycardia, hypotension, hypoxemia, and progressively increasing airway pressures—making clinical diagnosis challenging but essential, as positive pressure ventilation can rapidly convert even small pneumothoraces into life-threatening tension pneumothorax. 1, 2, 3

Primary Clinical Manifestations

Cardiovascular Signs

• Tachycardia is typically the earliest cardiovascular sign, often appearing before other hemodynamic changes 4, 2
• Hypotension develops as intrapleural pressure increases, indicating progression toward tension physiology 1, 2
• Hemodynamic instability with cardiovascular collapse represents tension pneumothorax requiring immediate needle decompression before imaging confirmation 1, 5

Respiratory Signs

• Decreased or absent breath sounds on the affected side is a key physical examination finding, though difficult to detect with limited chest access during surgery 1, 4, 3
• Progressive increase in peak airway pressures on the ventilator is a critical warning sign specific to the anesthetized patient 2, 3
• Hypoxemia (oxygen desaturation) occurs in 75% of pneumothorax cases, often out of proportion to pneumothorax size in patients with underlying lung disease 5, 6
• Difficulty with ventilation or signs of airway obstruction may be the initial presentation 4, 3

Timing and Triggers

• Symptoms may appear immediately after surgical port insertion in laparoscopic procedures 4
• Coughing episodes followed by persistent unexplained hypoxemia should raise suspicion, even with supraglottic airways 6
• Positive pressure ventilation can rapidly convert asymptomatic small pneumothoraces into tension pneumothorax 7, 2, 3

Critical Diagnostic Challenges

Why Diagnosis Is Difficult Under Anesthesia

• Initial vital sign changes are nonspecific and other causes (endotracheal tube malposition, bronchospasm, pulmonary embolism) are more common, making pneumothorax a diagnosis of exclusion 3
• Limited chest access during surgery compromises physical examination 3
• Local signs may be difficult to elicit in the draped, positioned surgical patient 3

High-Risk Scenarios Requiring Heightened Suspicion

• Previous failed central line attempts (especially subclavian) on the same or previous day, even if the patient had normal preoperative assessment 2
• Iatrogenic procedures around the base of the neck or chest wall 3
• Patients with underlying lung disease (COPD, asthma, bullous disease) are at higher risk and develop more severe symptoms 8, 1, 7
• Thoracic surgery or laparoscopic procedures with high insufflation pressures 4

Immediate Management Algorithm

Step 1: Recognize the Pattern

When you observe tachycardia + hypoxemia + increasing airway pressures, immediately consider pneumothorax in your differential 4, 2

Step 2: Exclude Common Causes First

• Verify endotracheal tube depth to exclude one-lung ventilation or mainstem intubation 2, 3
• Check for circuit disconnection or ventilator malfunction 3

Step 3: Clinical Examination

• Auscultate both hemithoraces for decreased or absent breath sounds 4, 3
• Assess for tracheal deviation (late sign of tension) 1

Step 4: Imaging When Feasible

• Portable chest radiograph in the operating room if patient is stable enough 4, 2
• Do NOT delay intervention if tension pneumothorax is clinically suspected based on hemodynamic instability 1, 5, 3

Step 5: Immediate Intervention

• For tension pneumothorax with hemodynamic compromise: Perform immediate needle decompression with large-bore cannula, followed promptly by tube thoracostomy 1, 5
• Halt surgery temporarily and manually ventilate with 100% oxygen 4
• Insert chest tube (16F-22F for most cases; 24F-28F if requiring continued positive pressure ventilation) connected to water seal 1, 7

Special Considerations for Underlying Lung Disease

Patients with COPD, asthma, or bullous disease develop symptoms out of proportion to pneumothorax size and require more aggressive intervention 8, 7

• Even small pneumothoraces (<2 cm) in secondary cases have significant clinical implications and should not be observed 8
• Arterial PaO₂ below 7.5 kPa (55 mmHg) and PaCO₂ above 6.9 kPa (50 mmHg) occurs in 16% of secondary pneumothorax cases 8
• These patients require immediate chest tube drainage rather than aspiration, as aspiration has significant limitations in secondary pneumothorax 7

Critical Pitfalls to Avoid

• Never initiate positive pressure ventilation in a patient with known or suspected pneumothorax without first inserting a chest tube, as this will create tension pneumothorax 7, 2, 3
• Do not rely on normal preoperative assessment to exclude pneumothorax risk—undetected small pneumothoraces can be asymptomatic until positive pressure is applied 2
• Maintain close communication with surgeons about any penetrating procedures performed preoperatively (central lines, nerve blocks, biopsies) 3
• Do not dismiss persistent hypoxemia after coughing episodes, even with apparently normal examination 6