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Objectives
Describe the pathophysiology of bronchopleural fistula.
Describe the design and function of underwater seal chest drainage units.
List techniques to minimize air leak.
Discuss the mechanical ventilation of patients with bronchopleural fistula.
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Pneumothorax, subcutaneous emphysema, pneumomediastinum, pneumopericardium, and other forms of extra-alveolar air are referred to as barotrauma. A bronchopleural fistula is a persistent leak from the lung into the pleural space, identified by either intermittent (during inspiration) or continuous chest tube air leak. Most barotrauma occurs in patients with trauma, acute respiratory distress syndrome (ARDS), chronic obstructive pulmonary disease (COPD), asthma, and postthoracic surgery. Properly treated extra-alveolar air and bronchopleural fistula are not usually life-threatening problems; however, they do complicate ventilator management.
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Extra-alveolar air can develop with trauma, surgical procedures, tumors, and vascular line placement. During mechanical ventilation, extra-alveolar air forms as a result of alveolar rupture to allow gas to enter the adjacent bronchovascular sheath and dissect into the pleural space. Pulmonary disease, high pressure, and overdistention must be present for extra-alveolar gas to develop to a critical level. Extra-alveolar air develops most frequently in COPD and ARDS patients, particularly if complicated by necrotizing pneumonia. Maintaining peak alveolar pressure less than 30 cm H2O and tidal volume 4 to 8 mL/kg ideal body weight avoids the setting where alveolar rupture is facilitated. Signs and symptoms of a pneumothorax during mechanical ventilation are listed in Table 25-1.
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Pressure within the pleural space is normally subatmospheric. Once the thorax is entered, gas tends to move into the pleural space. To prevent the extension or development of a pneumothorax, a one-way valve must be attached to the chest tube to prevent air movement into the thorax. This is accomplished by use of an underwater seal (Figure 25-1). The chest tube is placed 2 cm under a column of water and, thus, gas may exit the pleural space when the pressure exceeds 2 cm H2O. To accommodate fluid drainage, a second container is added to the drainage system. Fluid drains into the collection chamber without affecting the water seal. To facilitate fluid movement and to prevent loculated pockets of air from accumulating in the pleural space, a third chamber is frequently added to control the suction pressure applied ...