What factors increase a patient's risk of barotrauma and how should they be screened and managed before activities involving rapid ambient pressure changes?

Barotrauma Risk Factors and Pre-Activity Screening

Patients with localized or generalized airway narrowing, bullae, emphysematous blebs, or reduced mid-expiratory flow rates are at significantly increased risk of pulmonary barotrauma and should be identified through targeted respiratory assessment before diving or hyperbaric exposure. 1, 2

Primary Risk Factors for Pulmonary Barotrauma

The most critical risk factors that increase mortality and morbidity include:

• Airway obstruction (localized or generalized) - impedes gas escape during ascent 1
• Bullae or emphysematous blebs - particularly subpleural blebs that may not appear on standard chest X-ray 2
• Reduced mid-expiratory flow rates - specifically MEF50 and MEF25 values significantly lower than normal 2
• Low FVC - inversely related to barotrauma risk during pressure exposure 1
• Asthma - documented as a major risk factor in case reports of cerebral air embolism 1
• Previous pneumothorax - creates structural lung weakness 1

A critical caveat: Even patients with normal imaging and negative bronchoprovocation testing can experience barotrauma, though this is rare 1. CT scans reveal subpleural blebs in approximately 40% of barotrauma cases that were invisible on standard chest radiographs 2.

Screening Algorithm Before Pressure Activities

Step 1: Detailed Respiratory History

Focus specifically on:

• Current respiratory symptoms (dyspnea, wheeze, cough)
• Asthma or COPD diagnosis
• Previous pneumothorax episodes
• Childhood lung disease
• Chest trauma history 1

Step 2: Physical Examination

Perform thorough respiratory system examination looking for:

• Wheeze or reduced air entry
• Signs of hyperinflation
• Evidence of previous chest surgery 1

Step 3: Spirometry (Mandatory)

Measure and evaluate:

• FEV1, FVC, and peak expiratory flow - must be within normal limits 1
• Mid-expiratory flow rates at 50% and 25% of vital capacity - reduced values are red flags even when FEV1 is normal 2

Key finding: Divers who developed pulmonary barotrauma had significantly lower MEF50 (p<0.05) and MEF25 (p<0.02) compared to those with decompression sickness alone 2.

Step 4: Risk-Stratified Imaging

Low-risk patients (negative history, normal examination, normal spirometry):

• Routine chest imaging is not indicated 3
• Standard chest X-ray has low sensitivity for detecting blebs/bullae 3, 2

High-risk patients (positive history, abnormal spirometry, or respiratory symptoms):

• CT chest is preferred over plain radiography for detecting emphysematous changes 2
• However, recognize that CT has high false-positive rates due to incidental findings in healthy individuals 3

Additional Risk Factors by Organ System

Middle Ear Barotrauma Risk Factors

• Inability to autoinflate (Valsalva maneuver) - 91% incidence vs. 37% in those who can autoinflate 4
• Altered mental status - 2.5-fold increased risk (OR 2.50) 5
• Eustachian tube dysfunction 4
• Emergency/urgent treatment scenarios - 6.75-fold increased risk 5

Situational Risk Factors

• Rapid uncontrolled ascent - most common scenario for pulmonary barotrauma 1
• Running out of compressed gas at depth 1
• Skip breathing pattern (intermittent breathing) 1
• Breath-holding during ascent 1

Management Approach

For patients with identified risk factors:

1. Absolute contraindications to diving/hyperbaric exposure:

   • Active asthma with current symptoms
   • Known bullae or cysts on imaging
   • Previous spontaneous pneumothorax
   • Significantly reduced mid-expiratory flows

2. Relative contraindications requiring specialist evaluation:

   • Well-controlled asthma (asymptomatic, normal spirometry)
   • Remote history of pneumothorax with documented resolution
   • Borderline spirometry values

3. For middle ear protection in hyperbaric therapy:

   • Consider prophylactic myringotomy or pressure-equalizing tubes for patients unable to autoinflate 4
   • Oral pseudoephedrine 120 mg has Level 1 evidence for preventing otic barotrauma in adults (not effective in children at 1 mg/kg) 6

Critical Clinical Pearls

• Barotrauma can occur at shallow depths - serious cases documented at only 5 meters depth due to greater pressure-volume changes near the surface 1
• Arterial gas embolism is the most feared complication - presents with neurological symptoms, impaired consciousness, convulsions, or sudden death from coronary embolism 1
• Pneumothorax at depth becomes tension pneumothorax during ascent due to continued gas expansion 1
• Questionnaire-based screening is insufficient - medical examination with spirometry is required when any positive responses are obtained 1