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Objectives

  1. Describe the pathophysiology of bronchopleural fistula.

  2. Describe the design and function of underwater seal chest drainage units.

  3. List techniques to minimize air leak.

  4. Discuss the mechanical ventilation of patients with bronchopleural fistula.

Introduction

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 post-thoracic surgery. Properly treated extra-alveolar air and bronchopleural fistula are not usually life-threatening problems; however, they do complicate ventilator management.

Overview

Pathophysiology

Extra-alveolar gas can develop with trauma, surgical procedures, tumors, and vascular line placement. During mechanical ventilation, extra-alveolar gas forms as a result of alveolar rupture, allowing it 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 accumulate to a critical level. Extra-alveolar gas develops most frequently in patients with COPD and ARDS, particularly if complicated by necrotizing pneumonia. Maintaining peak alveolar pressure less than 28 cm H2O, driving pressure less than 15 cm H2O, and tidal volume 4 to 8 mL/kg avoids the setting where alveolar rupture is facilitated. Signs and symptoms of a pneumothorax during mechanical ventilation are listed in Table 25-1.

Table 25-1Signs and Symptoms of a Pneumothorax During Mechanical Ventilation

Chest Tubes

Pressure within the pleural space is normally subatmospheric. Once the thorax is opened, gas moves into the pleural space. To prevent the extension or development of a pneumothorax, a one-way valve is attached to the chest tube to prevent movement of gas 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 exits 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 prevent loculated pockets of gas from accumulating in the pleural space, a third chamber is added to control the suction pressure applied ...

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