The most likely common factor in the pathologic process that leads to reexpansion pulmonary edema seems to be enhanced endothelial permeability. This process may result from alveolar-capillary membrane disruption and ischemia-reperfusion injury caused by stretching, and from increased pulmonary flow occurring in pulmonary reexpansion. This enhanced endothelial permeability may then propagate and worsen as a result of local cellular delivery of free radicals (the main basis of reperfusion injury) and inflammatory mediators.
Another potential factor in the pathogenesis of reexpansion pulmonary edema is increased hydrostatic pressure from vascular flooding of the reexpanded lung caused by negative intrapleural pressure. Although draining larger effusions to dryness in the absence of respiratory symptoms is reasonable, caution should be taken to avoid highly negative intrapleural pressures. Patients who appear to be at higher risk and warrant more gradual evacuation include those who have had a large pneumothorax, younger patients, those in whom the lung has not reexpanded for more than 7 days, and possibly those who have had more than 3 L of pleural fluid drained.[1,5,7,9,10]
The clinical presentation of reexpansion pulmonary edema can vary widely, ranging from asymptomatic radiologic findings to a combination of severe cardiac and respiratory insufficiency and circulatory shock. Detecting initial signs of unilateral pulmonary edema early is important, in order to begin treatment and prevent the above-mentioned cascade that can lead to severe respiratory failure and death.[3,5,11]
Therapy involves, in principle, an increase in the intra-alveolar pressure (to redirect the fluid into the interstitium and capillaries) together with adequate oxygenation and hemodynamic support. The goals of treatment include adequate oxygenation, diuresis (as hemodynamics allow), hemodynamic support, and mechanical ventilation with positive end-expiratory pressure (when necessary).
A few reports have detailed the treatment of unilateral reexpansion pulmonary edema with noninvasive continuous positive airway pressure (CPAP). When clinical conditions allow for it, noninvasive ventilation with CPAP is a reasonable therapeutic alternative. The use of CPAP in cardiogenic pulmonary edema is an effective and accepted therapy. Data in the literature support the use of CPAP in other types of pulmonary edema and respiratory failure.
The use of noninvasive CPAP in the treatment of reexpansion pulmonary edema, is still considered controversial, especially when it manifests as a unilateral process and the patient is hemodynamically unstable.[2,5] The drop in blood pressure and the hemodynamic instability that are often seen in reexpansion pulmonary edema should not, however, be considered an absolute contraindication to the use of CPAP because the benefits of correcting hypoxemia and increasing the mean airway pressure probably outweigh the contraindications, provided that careful attention is paid to any hemodynamic alterations that may occur with this modality.
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Cite this: Giovanni Volpicelli. A 75-Year-Old Man With Dyspnea and Chest Pain - Medscape - Nov 30, 2016.