Proteomic Analysis of Two Non-Bronchoscopic Methods of Sampling the Lungs of Patients with the Acute Respiratory Distress Syndrome (ARDS)

Abstract

Abstract Objective The collection of lung fluid using a suction catheter (s-Cath) and non-bronchoscopic bronchoalveolar lavage (mini-BAL) are two minimally invasive methods of sampling the distal airspaces in patients with the acute respiratory distress syndrome (ARDS). The objective of this study was to determine the similarity of the lung fluid samples recovered by these methods using proteomic analysis. Methods Distal lung fluid samples were collected from seven mechanically ventilated patients with ARDS using both s-Cath and mini-BAL in each patient and compared using two-dimensional difference gel electrophoresis. Protein spots of interest were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Main Results An average of 2,164 spots was detected in the s-Cath and mini-BAL samples. Of these, 68.4% of the protein spots were similar between the s-Cath and mini-BAL samples, 13.2% were increased in s-Cath compared to mini-BAL, and 18.4% were decreased in s-Cath compared to mini-BAL. For each of the seven subjects, overabundance analysis showed that the actual number of differentially expressed spots in the mini-BAL and s-Cath sample was more than the expected number if the samples were identical. There were nine proteins that were consistently differentially expressed between the mini-BAL and s-Cath samples. Of these nine proteins, five are abundantly found in neutrophils or airway epithelial cells, suggesting that the s-Cath may sample the bronchial airways to a greater extent than mini-BAL. Conclusion Proteomic analysis of mini-BAL and s-Cath samples shows for the first time that, although these two methods for sampling the lungs of critically ill patients are generally similar, the s-Cath method oversamples the distal airways compared to the mini-BAL method.