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* From the Division of Pulmonary and Critical Care (Dr. Baydur), the Department of Medicine, and the Department of Pathology (Dr. Kanel), Rancho Los Amigos National Rehabilitation Center, Keck School of Medicine, University of Southern California, Los Angeles, CA.
Correspondence to: Ahmet Baydur, MD, FCCP, 2025 Zonal Ave, GNH 1900, Los Angeles, CA, 90033
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Abstract |
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Design: Necropsies were performed in seven patients with DMD who had received positive-pressure ventilation through uncuffed tracheostomies for a duration of 5 to 30 years.
Setting: Rehabilitation facility affiliated with a university medical center.
Results: The range of peak airway pressures sustained during ventilation by all the patients was 23 mm Hg to 36 mm Hg. Bronchoscopy (which was performed in four of the five patients) detected tracheomalacia in only one of the patients. Five of the seven patients demonstrated variable degrees of airway malacia. Two patients also had tracheal perforations, one of which resulted in a fatal hemorrhage from a tracheovascular fistula.
Conclusions: Given enough time, patients receiving positive-pressure ventilation can develop airway thinning and dilation even without the use of an inflated tracheostomy cuff. There is also a potential for tracheal erosion into an adjacent artery that can lead to fatal hemorrhage. Such findings also have implications for individuals receiving noninvasive positive-pressure ventilation, who could develop TBM as a result of the continuous cycling pressures on the airway wall.
Key Words: Duchenne muscular dystrophy • mechanical ventilation • tracheobronchomalacia • tracheostomies
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Introduction |
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Following the placement of a cuffed tracheostomy tube, most patients with neuromuscular disease who are to receive long-term ventilation are changed to an airway without a cuff to facilitate comfort and speech.5 Until now, it has been assumed that tracheal complications such as tracheal stenosis and TBM have been associated mainly with the constant pressure of the inflated cuff on the tracheal wall.3 4 There are no reports of TBM in adult patients receiving long-term ventilation through an uncuffed tracheostomy. We describe the autopsy findings of TBM in five patients with Duchenne muscular dystrophy (DMD) who had received long-term ventilation for many years (even decades) while using an uncuffed tracheostomy. In addition, two of the patients developed tracheal perforations, one of which led to fatal hemorrhage.
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Materials and Methods |
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Results |
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18 years of age between 1957 and 1995. During this period, approximately 30 ventilator-dependent patients lived at the facility for variable lengths of time because of the unavailability of community resources. The autopsy records were reviewed for seven patients with DMD who died after having lived at the facility for many years. All patients had spinal deformities. Five of these seven patients (listed in Table 1
) were found to have varying degrees of tracheal malacia (with or without bronchial malacia). The causes of death included ventilator-associated pneumonia and cardiomyopathy. The clinical and pathologic aspects of these five patients are summarized in Table 1
. The remaining two patients did not demonstrate tracheal or bronchial malacia at autopsy. Chest roentgenograms demonstrated tracheal dilation (with an uncuffed tracheostomy) in only one of five patients (patient 5; Table 1 ). Bronchoscopy (three fiberoptic and one rigid) was performed to evaluate airway obstruction in four of five patients who were found to have TBM at autopsy. Patient 4 was found to have a long segment of invagination of the posterior tracheal membrane, which gave the appearance of a polypoid diverticular structure. Patient 1, who underwent bronchoscopy at the time of the revision of his tracheostomy was found to have stenosis from granulation tissue. A false passage also was noted below the tracheostomy site in the anterior wall. In addition to a patulous stoma and proximal trachea, patient 5 was noted to have erosions and edema at the level of the tip of the tracheostomy. No bleeding was observed at the time, however. Patient 2 underwent repeated bronchoscopy for the evaluation and management of secretions. His posterior tracheal wall was noted to bulge inward during the expiratory cycle of ventilation.
Sections of the trachea taken from patient 4 at the postmortem examination showed the focal absence of the tracheal cartilage, with replacement by the predominantly firm tan-gray fibrous tissue (Fig 1 ). A microscopic examination confirmed the absence of cartilage in these sites, with the fibrous tissue composed of collagen and mature fat (Fig 2 ). The border of the intact cartilage and this fibrous tissue was distinct, without an associated inflammatory component involving the cartilage.
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Discussion |
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All of the patients described here were receiving long-term ventilation through uncuffed tracheostomies. In only one of our patients, in whom TBM was found at autopsy (patient 5), was there radiographic evidence of abnormal tracheal dilation. Thus, the chest roentgenogram was unreliable in detecting airway widening. In patient 5, because of the patulous stoma and recurrent wound breakdown, an attempt was made to ventilate the patient with an uncuffed flexible metal tracheostomy. The use of this device did not result in wound closure or prevent the terminal hemorrhage. The direct cause of the vascular erosion was not clear but was in some way related to the markedly enlarged tracheostomy site. A small outflow vessel from the innominate artery exhibited direct communication with the hemorrhagic region and was the site of the terminal bleeding. The presence of the vessel at the site may have been coincidental or it may have contributed to the weakening of the already compromised tracheal wall.
It is not known at what airway pressures and over what period of time tracheobronchial damage occurs even with the use of uncuffed tracheostomies in older children or young adults with DMD who are receiving assisted ventilation. Barret et al10 reported a higher incidence of tracheomalacia in 36 children with burns (most of whom had inhalation injuries) who had required airway pressures of > 50 cm H2O for > 10 days. Law et al4 described 81 patients with long-term tracheostomies (mean duration, 4.9 months) who were examined via fiberoptic bronchoscopy prior to decannulation. Twenty-three percent of their patients had TBM. Their study did not report airway pressures. None of our patients’ airway pressures approached the values of the patients in the study by Barret et al,10 but our patients had received tracheostomy positive-pressure ventilation for many years. Recurrent tracheobronchial infections also could have led to chronic inflammation, weakening, and atrophy of the longitudinal elastic fibers with thinning of the muscularis mucosa, resulting in the dilation of the membranous and cartilaginous portions of the trachea and main bronchi. This increased compliance of the wall allows the development of broad diverticulum-like protrusions of redundant musculomembranous tissue between the cartilaginous rings.11 The myopathic involvement of the tracheal muscularis also could contribute to the weakening and dilation of the wall. The use of pressure-controlled ventilation instead of volume-cycled ventilation may prevent tracheal complications, although ventilation may need to be adjusted to compensate for the uncuffed tracheostomy.
These findings also have implications in patients who receive noninvasive positive-pressure ventilation (NIPPV), which is currently the form of ventilation advocated in neuromuscular and chest wall disorders.8 12 It is now possible, with appropriate nasal and oral interfaces, to provide ventilatory assistance up to 24 h per day, even in patients with unmeasurable vital capacities.12 Since inflation pressures similar to those delivered through a tracheostomy would be needed to provide equivalent ventilation, the same pressure-related airway changes could develop in individuals receiving NIPPV. Pathologic confirmation of such changes in patients receiving NIPPV is not available, in part because patients have not been using it as long as tracheostomy-assisted ventilation (approximately 15 vs 50 years, respectively). The postmortem examination of the airway in patients who had received NIPPV for many years (comparable in time to those receiving tracheostomy-assisted ventilation) would provide information on this issue.
Of interest, therapy with continuous positive airway pressure has been used to "pneumatically stent" airways in intubated newborns with TBM while awaiting improvement in airway rigidity with growth.13 It is possible that in our patients the application of tracheostomy-assisted positive-pressure ventilation, while contributing to the TBM, also prevented or delayed airway collapse until the terminal phase of illness.
In addition to the finding of tracheal and bronchial malacia, two of our patients developed erosions that led to hemorrhage, one of which was fatal. Patients with spinal deformities may have tracheostomies that are crooked or eccentric within the tracheal lumen, as demonstrated by a chest radiograph or fiberoptic bronchoscopy. In our experience, fiberoptic bronchoscopy has demonstrated erosions mainly in those patients in whom the tracheostomy tip abuts against the tracheal wall. This situation may be found in patients with scoliosis or in those in whom traction from the ventilator tubing pulls the tracheostomy to one side. Repeated tracheal suctioning to remove secretions also can exacerbate erosions. In at least two of these patients (patients 1 and 5), perforations developed in the trachea that undoubtedly resulted from friction or suction trauma. To avoid this complication, whenever possible, the ventilator tubing should be adjusted so that it does not pull the tracheostomy to one side and the latter is positioned parallel to the axis of the trachea. In wheelchair-dependent individuals, this may require the installation of supports that are designed to keep the tracheostomy in a neutral position. Despite these precautions, however, erosion and perforation may be unavoidable in patients receiving tracheostomy-assisted ventilation for many years. The use of NIPPV should at least prevent tracheal erosions, although, as discussed above, it may not avoid tracheal malacia.
In summary, we have presented autopsy evidence of TBM in five patients with DMD who had received support from uncuffed, tracheostomy-assisted, positive-pressure ventilation for between 5 and 30 years. Histologic findings of the airways revealed variable degrees of cartilage thinning and airway dilatation. Two of the patients also had tracheal perforations, one of which directly led to a massive hemorrhage through a tracheovascular fistula. These clinical and pathologic findings demonstrate that, given enough time, it is possible to develop airway malacia while receiving positive-pressure ventilation, even without the use of tracheostomy cuffs. Thus, these changes may have implications for patients receiving NIPPV, as continuously cycling intratracheal pressures may lead to a similar complication. Such findings would need to be confirmed postmortem in patients who have received long-term NIPPV.
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Acknowledgements |
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Footnotes |
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Received for publication April 30, 2002. Accepted for publication August 26, 2002.
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This article has been cited by other articles:
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  F. Iodice, G. Brancaccio, A. Lauri, and R. Di Donato Preventive ligation of the innominate artery in patients with neuromuscular disorders Eur. J. Cardiothorac. Surg., April 1, 2007; 31(4): 747 - 749. [Abstract] [Full Text] [PDF]
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 A. Baydur, G. Kanel, and M. Koss Tracheobronchomalacia and Noninvasive Ventilation Revisited Chest, October 1, 2004; 126(4): 1390 - 1392. [Full Text] [PDF]
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J. R. Bach Tracheobronchomalacia and Noninvasive Ventilation? Chest, November 1, 2003; 124(5): 2038 - 2038. [Full Text] [PDF]
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