Journal of the Louisiana State Medical Society
channel between the lung or a peripheral bronchus and the pleura. 20 The underlying causes for BPFs can also be evalu- ated with MDCT. Thin-section MDCT with axial and MPR (multiplanar reconstruction) images is important in the detection of small, central BPFs. Standard CT images are at a disadvantage due to the plugging of the fistula with debris or secretions and the small size of the defect. Multidetector CT scanners can solve these problems with their thin sec- tions, faster scanning times, fewer respiration artifacts, and higher image quality. 8 Chest MDCT is an accurate, easy, and non-invasive technique for diagnosing and monitoring BPFs and should be the first diagnostic method of choice for patients who are clinically suspected of having a BPF. Multidetector CT allows for the evaluation of the presence, size, and localiza- tion of the fistula tract and also demonstrates the possible underlying causes of this rare occurrence. 8 Other techniques used for the diagnosis of BPF include bronchography, the instillation of methylene blue dye through the stump and its detection in the chest tube, small metallic probes introduced through the working channel of the bronchoscope, and changes in gas concentration in the pneumonectomy cavity after inhaling different concentra- tions of oxygen and N 2 O. 2,17 Treatment options include conservative approach, endobronchial intervention, or surgical repair. Small fistu- las (<5 mm) can be medically managed with conservative strategies. Larger fistulas require surgical repair. In high surgical risk patients, endoscopic/endobronchial options can be pursued. Conservative management with chest tube(s) drainage and lung protective ventilation is sometimes chosen for critically ill patients. The air flow through the BPF theoreti- cally delays the healing of the fistula site, and reducing flow through the fistula has been a major goal in management of these patients. The BPF provides an area of low resistance to flow and acts as a conduit for the escape of a variable percentage of the delivered tidal volume during conven- tional positive pressure mechanical ventilation. Strategies to decrease fistula flow (reduce airway pressure) include application of lowest effective tidal volume, least number of mechanical breaths, lowest PEEP, and short inspiratory time. In our patient, this was complicated by poor oxygenation secondary to ARDS requiring high PEEP. 14 Other ventilatory strategies include differential lung ventilation, 18 selective intubation of the unaffected lung, and patient position. Positioning the patient such that BPF is dependent has been shown in one report to decrease fistula flow. 16 Few case reports of successful use of high frequency oscillatory ventilation (HFOV) have been published. 9,10 In a retrospective review of 39 patients with BPF sup- ported by conventional ventilation, it was shown that even in the face of significant fistula leaks, only two of the 39 patients developed severe respiratory acidosis (pH <7.30). 15 Literature suggests that the gas excreted via a chest tube participates in gas exchange prior to reaching the BPF and the chest tube.
In a study of nine patients with ARDS complicated by barotrauma-induced BEF, it was concluded that gas excreted via a chest tube in a patient with ARDS participated in gas exchange and must be considered when calculating total CO2 excreted via the leak. In this study, the mean total minute ventilation was 23.9 ± 7.5 L/min with 25% ± 17% of that gas escaping via the leak. Carbon dioxide was routinely present in the leaked gas, often in higher concentrations than in the expired gas, although the difference between the leaked and expired gas was not significant. The fraction of minute production of carbon dioxide excreted via the leak correlated with the fraction of inspired gas excreted via the leak. 11 Endobronchial intervention includes either a sealant application or an endobronchial placement of a blocker, a stent, or an occluding device. Successful closure of a BPF us- ing an occlusion device originally designed for transcatheter closure of an atrial septal defect has been recently done. 12 Surgical repair is considered to be the definitive treat- ment of BPF. In a study of 42 patients with postoperative BPF, surgical repair of BPF resulted in a success rate of 86% and associated mortality of 9.5%. 18 In another study of 13 patients with postoperative BPF, surgical repair was associ- ated with one fatal recurrence at three months post-repair. 19 Prognosis of BPF is poor in the setting of mechanical ventilation. BPF is an ominous complication of ventilator management in acute respiratory failure. In a single center study, 39 of the 1,700 patients receiving mechanical ventila- tion had BPFs lasting at least 24 hours. Overall mortality in these 39 patients was 67%. Mortality was higher when BPF developed late rather than early in the illness (94% vs 45%, respectively). Large air leaks also had significant mortality compared to smaller leaks. 13 CONCLUSION This case illustrates a rare but important presentation of bronchopleural fistula in the setting of acute respiratory distress syndrome. Physicians should be aware of this entity and consider it in the differential diagnosis of a persistent air-leak in a technically adequate chest tube. ACKNOWLEDGEMENTS The authors report that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article. REFERENCES 1. Dutau H, Breen DP, Gomez C, Thomas PA, Vergnon JM. The integrated place of tracheobronchial stents in themultidisciplinary management of large post-pneumonectomy fistulas: our experience using a novel customised conical self-expandable metallic stent. Eur J Cardiothorac Surg . 2011 Feb;39(2):185-9. 2. Lois M, Noppen M. Bronchopleural fistulas: an overview of the problem with special focus on endoscopic management. Chest . 2005 Dec;128(6):3955-65.
260 J La State Med Soc VOL 166 November/December 2014
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