Bedside Measurement of Ventilation With or Without a One-way Valve During Lung Lavage

Surveillance of the lungs for bacteria is routinely undertaken in artificially ventilated patients as these individuals are at high risk of developing pneumonia. Knowledge of the types of bacteria present allows the rapid treatment with the correct antibiotics if a pneumonia develops. Surveillance is undertaken using a technique called non-directed bronchoalveolar lavage (NBL), which can be performed by the bedside nurse. This involves suctioning some of the lung secretions into a sample pot and sending it to the microbiology laboratory to identify any bacteria present. When this procedure is performed there is some collapse of the lung due to escaping gas. The purpose of this study is: 1. To use a non-invasive imaging technique known as electrical impedance tomography (EIT) to measure the amount of lung collapse during an NBL. Half of the patients in the study will have a one-way adapter valve connected to the breathing circuit. This adapter is designed to make the insertion of a suction catheter easier and prevent the loss of gas. 2. Look at which region of the lung the sample is being collected from as the suction tube used to take the samples may pass into either the left or right lung. EIT is a simple non-invasive technique which has been in use for many years. It uses pairs of electrodes around the chest through which imperceptible currents are passed. A computer shows an image of which parts of the lungs have the most or least air in them. This has the advantage over other imaging techniques in critical care that it does not use radiation and gives a real time picture at the bedside of the variations in ventilation throughout the lungs.