Risk Factors for Loss of Sliding Lung in a Medical Intensive Care Population With Acute Respiratory Failure.

SESSION TITLE: Diagnostic Procedures and Interventions PostersSESSION TYPE: Original Investigation PosterPRESENTED ON: Wednesday, October 29, 2014 at 01:30 PM - 02:30 PMPURPOSE: Point of Care Bedside Ultrasound is now widely utilized as a rapid technique to evaluate patients with a range of acute pulmonary emergencies, including acute pneumothorax. We attempted to identify patient related risk factors for absent lung slide in Medical ICU patients with respiratory failure who did not have pneumothoraces, to help define appropriate use of this technology in the future.METHODS: Data was collected on 158 patients admitted to the MICU with Acute Respiratory Failure who were undergoing routine admission lung ultrasound. The lung ultrasound exam consisted of 3 views of each hemithorax. A Sonosite M-Turbo Ultrasound machine was used with a p21x transducer (5.1 MHz) set in abdominal preset mode. 4 second clips at each location on the hemithorax were stored for review. Demographic and patient characteristics were recorded to identify risk factors for loss of lung slide in the absence of a pneumothorax, which was confirmed by Chest X-Ray in all patients and by CT when available for review.RESULTS: There were a total of 3 right sided pneumothoraces in the 158 patients, all were detected by bedside lung ultrasound with loss of lung slide. There were 13 additional patients that demonstrated loss of lung slide on the right. Statistically significant risk factors by multivariate analysis for loss of slide in the absence of pneumothorax were, hypercarbic vs hypoxemic respiratory failure (p<0.05), low BMI (p<0.001) and history of prior chest tube insertion (p=0.03 lateral, p=0.06 apical). On evaluation of the left hemithorax, 7 patients failed to demonstrate lung slide, all at the apical evaluation site. Multivariate analysis confirmed low BMI (p=0.001) and male sex (p=0.017) as risk factors as well as a trend in patients with a history of COPD/asthma (p=0.077). Risk factors which were not significant bilaterally included the presence of ARDS, ILD, prior thoracic surgery and history of lung transplantation.

CONCLUSIONS: Hypercarbic respiratory failure, male sex, prior chest tube insertion and low BMI were the predominant risk factors that were clearly associated with the loss of lung slide in the absence of pneumothorax.

CLINICAL IMPLICATIONS: Our study defines some of the risk factors associated with loss of lung slide in the absence of pneumothorax. Interestingly, prior thoracic surgery and a prior history of lung transplantation were not risk factors for loss of lung slide. Prior chest tube insertion likely causes a pleurodesis causing loss of lung slide by ultrasound.DISCLOSURE: The following authors have nothing to disclose: Christopher Mallow, Warren IsakowNo Product/Research Disclosure Information.