Management of persistent air leaks in patients on mechanical ventilation

INTRODUCTION — Persistent (prolonged) air leaks (PALs) via a chest tube thoracostomy can occur in mechanically ventilated patients, often indicating the development of an alveolopleural fistula (APF).

An overview of the management of air leaks from APF in the setting of mechanical ventilation [1-3] is reviewed here. The pathogenesis, diagnosis, and management of APF in nonventilated patients and the management of bronchopleural fistulas [4,5] are discussed separately. (See "Alveolopleural fistula and prolonged air leak in adults" and "Bronchopleural fistula in adults".)

DEFINITION — An alveolopleural fistula (APF) is a pathological communication between the pulmonary parenchyma distal to a segmental bronchus and the pleural space. APFs in mechanically ventilated patients occur via alveolar rupture due to barotrauma, direct injury, or other mechanisms (table 1). The distinction between APF and bronchopleural fistulas (ie, a pathological communication between a bronchus down to the segmental level and the pleural space) is described separately. (See "Bronchopleural fistula in adults" and "Alveolopleural fistula and prolonged air leak in adults".)

APFs present as PALs noted on chest tube drainage. PALs from APF are most commonly seen following lung volume reduction surgery, but can also be associated with several other specific etiologies including ventilator-induced barotrauma, iatrogenic injury related to central venous catheter placement, parenchymal lung disease (table 2). What defines "persistent" in mechanically ventilated patients is unclear. However, air leaks beyond five days are accepted by most experts as being "persistent." In most cases the location of the fistula and the etiology are apparent but additional investigations may be necessary to locate and diagnose APF (eg, computed tomography), the details of which are discussed separately. (See "Alveolopleural fistula and prolonged air leak in adults", section on 'Clinical features' and "Diagnosis, management, and prevention of pulmonary barotrauma during invasive mechanical ventilation in adults", section on 'Diagnostic evaluation and management'.)

The etiology and pathogenesis of alveolar rupture in mechanically ventilated patients is also discussed separately. (See "Diagnosis, management, and prevention of pulmonary barotrauma during invasive mechanical ventilation in adults", section on 'Pathogenesis and risk factors'.)

MANAGEMENT — For all etiologies, most patients on mechanical ventilation with an air leak can be managed conservatively [1,3]. This includes continued drainage of air via chest tube thoracostomy (if feasible), limiting airway pressure and tidal volume on mechanical ventilation, treatment of underlying pulmonary disorders including infection, and optimizing nutrition. This management strategy is based upon our experience and indirect data from observational studies of patients with alveolopleural fistula and patients with acute respiratory distress syndrome (ARDS) complicated by barotrauma. This strategy is fundamentally different compared with management of air leaks due to a bronchopleural fistula, which are more often managed with an intervention to seal the leak. Importantly, the treatment approach should be multidisciplinary to promote a treatment plan tailored to the patient's condition. (See "Bronchopleural fistula in adults".)

Quantification of the volume of the air leak is not always necessary but may be useful when the leak is suspected to be large, including when an intervention may be required. Details regarding quantification are provided separately. (See "Alveolopleural fistula and prolonged air leak in adults", section on 'Quantifying the air leak'.)

Continued drainage of air — Air should continue to be drained by chest tube thoracostomy to facilitate lung expansion and reduce the risk of hemodynamic complications. In severe cases, including those with incomplete lung re-expansion, more than one chest tube may be required.

Most experts agree that the least amount of chest tube suction should be applied to maintain lung inflation [1]. The rationale for this practice is that suction may increase air flow through the defect, thus preventing spontaneous healing [6-9]. There are also isolated reports of excessive chest tube suction (for bronchopleural fistula) leading to ventilator auto-triggering [10,11]. On the other hand, if the visceral and parietal membranes are not apposed, then healing is unlikely to occur. Studies on suction practices in mechanically ventilated patients are limited to the post-thoracic surgery population and evaluate development or prevention [6-8,12], as opposed to management, of established PALs. Thus, in our experience the amount of suction is generally determined on a case-by-case basis.

Further details regarding drainage and suction are provided separately. (See "Alveolopleural fistula and prolonged air leak in adults", section on 'General supportive care (drainage of air)'.)

Ventilator management — Ventilator strategies should aim to lower airway pressures in order to reduce the driving pressure for airflow through the defect [1,3,13]. For bronchopleural fistulas in mechanically ventilated patients, it appears that the volume of air leak is proportional to the mean airway pressure, with peak airway pressures >30 cm H₂O associated with increased air leak [14-16]. In one study evaluating patients undergoing surgical lung biopsy for ARDS, 30 percent developed an air leak lasting more than seven days, and the risk of PAL was reduced by 42 percent for every 5 cm H₂O reduction in peak airway pressure [17].

Specific strategies are largely based on expert opinion and include the following:

●Lowering the tidal volume and/or positive end-expiratory pressure often in conjunction with permissive hypercapnia, avoiding hyperventilation, and limiting time in inspiration to reduce mean airway pressure [1,13,14,17,18].

●If a patient's disease state allows, switching to pressure support ventilation can be beneficial. Similarly, synchronous intermittent mandatory ventilation with a low set rate will also limit airway pressures relative to standard assist control breaths.

●Patients should be liberated from mechanical ventilation as soon as possible. Further details regarding ventilator management are provided separately. (See "Diagnosis, management, and prevention of pulmonary barotrauma during invasive mechanical ventilation in adults", section on 'Ventilator management'.)

Supportive care — General supportive care involves optimizing nutrition and medical comorbidities as well as treating infection and ensuring adequate oxygenation.

REFRACTORY PATIENTS — Most PALs should resolve with supportive care as the underlying disease resolves. In the rare patients in whom the air leak does not improve or worsens, options include placement of additional chest tube(s) with ongoing supportive care, alternate modes of mechanical ventilation, extracorporeal support, and occasionally specific therapies aimed at closing the fistula.

Alternate modes of mechanical ventilation and support — Rare case reports have described the use of alternative modes of mechanical ventilation including high-frequency ventilation [19-22] or airway pressure release ventilation [23] when severe air leaks persist despite conservative measures.

Other reports have described success using independent lung ventilation [24-28] and bronchial occlusion of the lobe feeding the fistula using a double lumen tube [29] as a way to decrease flow through the leak.

Bronchial blockers are occasionally used on a short-term basis to accomplish the same goal [30,31].

Very rarely, for patients with persistent and refractory respiratory failure due in part to loss of tidal volume through the fistula, extracorporeal membrane oxygenation (ECMO) is an option if resources are available [32-35]. In combination with ultra-protective mechanical ventilation, one small series described sealing of three traumatic bronchopleural fistulae using ECMO as a primary treatment strategy [34,36]. (See "High-frequency ventilation in adults" and "Extracorporeal life support in adults in the intensive care unit: Overview" and "Modes of mechanical ventilation", section on 'Airway pressure release ventilation'.)

Definitive measures — Some air leaks and in particular, larger air leaks, may not respond to conservative therapy. In such cases definitive therapy to close the fistula may be necessary (eg, bronchoscopic or surgical methods). However, the timing of definitive procedures is variable since most interventions have better outcomes in spontaneously breathing patients. Thus, most clinicians continue conservative therapy until the patient is extubated, while considering interventions only on a case by-case basis (eg, patients with large air leaks not responding to conservative therapy that is potentially preventing extubation).

For many patients with prolonged air leak on mechanical ventilation who fail conservative therapy, less invasive management is preferable, particularly for those with comorbid conditions. For these situations, data describing successful closure specifically in mechanically ventilated patients are limited, with many available studies focused on bronchopleural rather than alveolopleural fistula [37-41]. Options include bronchoscopic placement of endobronchial valves, bronchoscopic sealants and sclerosants, and airway stents, along with nonsurgical pleural procedures including pleurodesis (via medical thoracoscopy or chest tube) or blood patches. Among the options, experience is greatest with endobronchial valves [38,40,42]. As an example, in one case series endobronchial valve replacement facilitated extubation in three patients with severe respiratory failure and PAL from acute respiratory distress syndrome [40,43]. Valves for prolonged air leak have been shown to be more successful in patients with complete integrity of the fissures by computed tomography scan (and thus absence of collateral air flow) [44]. Selection of an intervention should take into consideration the etiology of the air leak, reversibility of the underlying etiology, and location of the fistula, as well as local expertise. Further details of interventions for fistula closure are provided separately. (See "Alveolopleural fistula and prolonged air leak in adults", section on 'Patients who fail supportive care'.)

Surgical management of pneumothorax, including those with prolonged air leaks, is provided separately. (See "Pneumothorax: Definitive management and prevention of recurrence".)

OUTCOMES — The prognosis of patients who are mechanically ventilated and have prolonged air leaks is poorly studied but likely worse than patients with air leaks who are not mechanically ventilated. The outcome also likely depends upon the underlying cause, such that those with air leaks due to acute respiratory distress syndrome or cancer likely have worse prognosis than those following thoracic surgery.

One series reported an overall mortality of 67 percent in 39 patients who developed bronchopleural fistula on mechanical ventilation, with prognosis worse among those who developed nontraumatic fistulae late in their course, as well as in those with estimated air leaks >500 mL [45]. Data describing outcomes from air leaks due to barotrauma and alveolopleural fistula are discussed separately. (See "Diagnosis, management, and prevention of pulmonary barotrauma during invasive mechanical ventilation in adults", section on 'Prognosis' and "Alveolopleural fistula and prolonged air leak in adults", section on 'Evaluation and management'.)

SUMMARY AND RECOMMENDATIONS

●Definition – Persistent air leaks (PALs) present after initiation of chest tube thoracostomy can occur in mechanically ventilated patients, often indicating the development of an alveolopleural fistula (APF). An APF is a pathological communication between the pulmonary parenchyma distal to a segmental bronchus and the pleural space and is most commonly seen in mechanically ventilated patients with barotrauma (table 1). (See 'Definition' above and "Alveolopleural fistula and prolonged air leak in adults".)

●Management – The treatment approach to PALs in patients who are mechanically ventilated should be multidisciplinary and involve intensivist, pulmonary interventional, and thoracic surgery specialists to promote a treatment plan tailored to the patient's condition. (See 'Management' above and "Alveolopleural fistula and prolonged air leak in adults".)

•The primary management strategy of patients with a PAL from APF while on mechanical ventilation regardless of the etiology is conservative. This includes continued drainage of air via one or more chest tubes, using minimal suction to maintain lung inflation, limited airway pressure and volume ventilator settings (usually lowering the tidal volume and/or positive end-expiratory pressure), and treatment of the underlying disorder. (See 'Continued drainage of air' above and 'Ventilator management' above.)

•Additional supportive measures include optimizing nutrition and treating infection. (See 'Supportive care' above.)

•Most PALs from APF should resolve with supportive care as the underlying disease resolves. However, in a limited number of patients, PALs do not improve or progress. Options are limited and include continued supportive care with multiple chest tubes, alternate modes of mechanical ventilation/support, and occasionally definitive therapy. Definitive interventions can be considered on a case-by-case basis (eg, patients with large air leaks not responding to conservative therapy), though data are limited. (See 'Refractory patients' above.)

●Prognosis – The prognosis of patients who are mechanically ventilated and have PALs from APF is poorly studied but likely worse than patients with air leaks who are not mechanically ventilated. The outcome also likely depends upon the underlying cause and timing of the leak. (See 'Outcomes' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges David Pierson, MD, who contributed to earlier versions of this topic review.