Clinical dilemmas associated with pneumothoraces

Iatrogenic pneumothoraces

Small iatrogenic pneumothoraces in ventilated patients are inevitable in critical care. Typically, small air collections are an incidental or expected finding after difficult central venous cannulation. Subcutaneous emphysema may be palpable locally. Large ongoing leaks with obvious clinical signs clearly require intercostal drainage. Small and clinically insignificant pleural air collections due to needle laceration do not necessarily require drainage, as such lacerations may rapidly seal without further consequence. A repeat radiograph to determine pneumothorax evolution allows a reasoned decision in this situation. Vigilant observation in such patients is the key to avoiding extension of iatrogenic morbidity.

Pneumothoraces in ventilated asthmatics

The diagnosis of a pneumothorax in acute asthma may be extremely difficult. All ventilated asthmatics are at risk of pneumothorax, with a reported incidence of up to

20 per cent (Man..S.e!,.e.t...,a.( 1990). Patients may be moribund with extreme hyperinflation, and the clinical differentiation from pneumothorax may be extremely difficult.

One discriminating point is that ventilated asthmatics usually exhibit normal arterial oxygen saturation at moderate FiO 2 (e.g. 0.5), whereas those with a significant pneumothorax may be hypoxic owing to shunt through associated collapsed lung. In addition, an extended period of apnea (>20 s) should see significant hemodynamic improvement in asthma, although not in tension pneumothorax. We believe that there is no indication for needle aspiration in asthma. If no pneumothorax is present before aspiration, it certainly will be following blind needling and will mandate subsequent pleural cavity drainage. If a pneumothorax is suspected, intercostal tube placement, often bilateral, is appropriate. The potential for direct damage to the hyperinflated lung, which will not collapse away when the pleural incision is made, must be recognized, and intercostal catheters must be inserted with great care.

The significance of subcutaneous emphysema

Air originating from damaged lung units may track back via the hilum to the mediastinum and be manifest only as subcutaneous emphysema in the neck. In this situation, no pneumothorax may be present. In critical care practice, these signs are usually associated with pneumothorax or represent the precursor of more extensive pulmonary leaks in patients with predisposing pulmonary disease.

Subcutaneous emphysema, although cosmetically alarming, is usually a benign condition and does not, of itself, require treatment. However, massive surgical emphysema may render a patient difficult to intubate. It is reasonable to observe small areas of subcutaneous emphysema in the intubated patient if no pneumothorax can be identified. If subcutaneous air is extensive, and particularly if it is increasing, a CT scan may identify the origin. Alternatively, speculative bilateral pleural drainage may access an unrecognized air collection.

Subcutaneous emphysema of the chest wall, in the presence of a chest drain, may indicate that the drain is blocked and air is tracking around it or that the pneumothorax is incompletely drained. It may also occur if the proximal side-hole of the chest drain has migrated out of the pleural cavity.

Interhospital transfer of patients with severe respiratory failure

In patients undergoing positive-pressure ventilation, an attempt should be made to drain all pneumothoraces before interhospital transfer is undertaken. Strict limitation of peak inflation pressures or hyperinflation is impossible in such patients during transfer. Transport ventilators are often inadequate in poorly compliant patients, and manual ventilation, although necessary, may predispose to air leaks. Even the smallest pneumothorax should be drained, as the implications of its evolution during transport may be catastrophic.

Subcutaneous emphysema in such patients without obvious pneumothorax mandates bilateral prophylactic chest tube insertion. In pneumonia, acute lung injury, or other necrotizing lung disease, patients with poor compliance, who have been ventilated for several days and in whom pulmonary function is worsening, are at high risk of developing pneumothoraces in transit, and the insertion of bilateral prophylactic chest drains is reasonable and appropriate.

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Responses

  • peter brown
    Does pneumothorax in intubated patient mandate chest tube?
    7 years ago

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