In: Lung Injury24 Sep 2015
Serial portable chest roentgenograms are used to evaluate patients with pulmonary edema. The ability of portable chest roentgenograms to demonstrate and monitor changes in pulmonary edema in supine critically ill patients has never been fully evaluated. A modification of the double-indicator dilution technique has made it possible to make serial determinations of extravascular lung water. By using the thermal-dye technique to measure extravascular lung water and comparing the results with interpretation of portable chest roentgenograms, we sought to evaluate (1) the ability of portable chest roentgenograms to define extravascular lung water in critically ill supine adults, and (2) the utility of portable chest roentgenograms as a monitor for quantifying changes in lung water under these circumstances.
Materials and Methods
TWelve patients admitted to the intensive care unit with a diagnosis of respiratory failure were studied. All patients were intubated and mechanically ventilated at the time of entry into this study. The study was approved by the Stanford University Human Subjects Committee, and informed consent was obtained. A 16 ga central venous catheter or a 7F triple-lumen pulmonary artery catheter (Edwards Laboratory model 93A) was placed via the right internal jugular vein using a modified Seldinger technique. A 20-cm 5F thermistor-tipped catheter was placed in the femoral artery and advanced into the iliac artery. Measurements of extravascular lung water were made by rapidly injecting 10 ml of 0°C indocyanine green dye (4 mg) into the superior vena cava. Simultaneously with the injection, blood was withdrawn from the femoral artery catheter, heparinized, and passed through an in-line densitometer cuvette (Waters D 402A) at a constant rate of 30 ml/min. Withdrawn blood was then returned to the patient Extravascular lung water was calculated by a bedside lung water computer (Edwards Laboratory model 9310) that analyzes the thermal signal from the femoral thermistor catheter and the signal change detected by the densitometer. Extravascular lung water was determined as the mean of three thermal-dye measurements and expressed in milliliters per kilogram of the patients body weight.
The anteroposterior portable chest roentgenograms were obtained within two hours of each extravascular lung water determination. The roentgenograms were always obtained with the patients in a supine position, using a target film distance of 40 to 50 inches. The exposure factors (kilovolts; milliamperes) were kept constant for each patients series of roentgenograms. Radiographic exposure time wasminimized in order to decrease artifact from cardiac and respiratory motion. The roentgenograms were interpreted by a panel of three radiologists who were unaware of the thermal-dye results. The right and left lungs were divided into a total of six regions, consisting of two upper, two lower, and two perihilar regions (Fig 1). The pulmonary regions were scored on the basis of 0 to 65 points, with zero points representing a normal region and 65 points representing frank alveolar edema. The website of Canadian Neighbor Pharmacy is full of thought-provoking articles and you just need to use the link to read them.
The radiographic scoring system was as follows: 0, normal; 10, mild pulmonary vascular congestion; 20, moderate pulmonary vascular congestion; 30, severe pulmonary vascular congestion; 40, interstitial edema without septal lines; 45, interstitial edema with septal lines; 50, mixed interstitial and alveolar edema, with some sparing of pulmonary region; 55, mixed interstitial and alveolar edema, involving entire region; 60, alveolar edema, with sparing; and 65, alveolar edema involving entire pulmonary region. The total score could equal 0 to 65 times six regions, for a range of 0 to 390; ie, summation of scores from the six regions resulted in a final radiographic score ranging from 0 to 380 points. Measurements for each patient were obtained at random intervals at least six hours apart (range, 6 to 12 hours).
Statistical methods for evaluating radiographic score and lung water, and for change in score vs change in lung water utilized linear regression analysis with significance at p<0.05.
Figure 1. Radiographic scoring was accomplished by dividing lungs into following six regions: 1, right upper; 2, right perihilar; 3, right lower; 4, left upper; 5, left perihilar; and 6, left lower.
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