Severe tracheomalacia in the ICU: identification of diagnostic criteria and risk factor analysis from a case control study

Severe tracheomalacia (STM) is being increasingly recognized as a cause for respiratory failure in the ICU. The diagnosis is often overlooked, as chest radiography appears normal, and the role of invasive diagnostic testing for this diagnosis is not well described in the ICU setting. The prevalence and risk factors for STM are not known, and computed tomography (CT) based diagnostic criteria for ventilated patients are not well studied. Patients admitted between January 2008 and December 2010, with respiratory failure and who failed ventilator discontinuation or required reintubation, were screened for the presence of any tracheal collapse, utilizing prior CT of the chest. Bronchoscopically confirmed cases were compared with age and sex matched controls to identify risk factors. Twenty-five subjects were identified as having STM, which represented 0.7% of ICU admissions and 1.6% of subjects with respiratory failure. The mean ICU stay was significantly longer in STM (30 d, 95% CI 19.7-40 d), compared to controls (4.4 d, 95% CI 3.6-5.2 d). Obesity (odds ratio 1.26, 95% CI 1.04-1.54) and gastro-esophageal reflux (odds ratio 31, 1.7- 586) were associated with increased risk for STM. The pre-intubation PaCO2 (68 mm Hg, 95% CI 57-79 mm Hg) was significantly higher in STM, compared to controls (38 mm Hg, 95% CI 35-41). The distal tracheal antero-posterior diameter (2.80 mm, 95% CI 2.15-3.46) was significantly lower in STM. A receiver operating characteristic analysis showed a distal tracheal antero-posterior diameter < 7 mm to be the optimal cutoff measurement to diagnose STM. STM was associated with prolonged ICU stay. A distal tracheal antero-posterior diameter < 7 mm on a non-intubated CT chest was suggestive of STM that required a confirmatory bronchoscopy. Gastroesophageal reflux disease and obesity were potential risk factors.