The outlines of the lungs at the five CT levels were traced onto paper; these were cut out and weighed using an electronic balance. The ratios of the weights (and thus the lung volumes) for the five levels were (mean ± SD) as follows: level 1=0.129 ±0.017; level 2=0.190 ±0.011; level 3=0.222 ±0.008; level 4=0.228 ±0.009; and level 5=0.230 ± 0.015. The mean of the percentage of abnormal lung estimated by the two observers at each level was multiplied by the corresponding ratio. Adding the five adjusted figures gave an estimation of the overall percentage volume of abnormal lung. purchase zyrtec
Data are presented in the text as mean±SEM except where otherwise stated. The percentage of persistently abnormal lung at both initial scan and follow-up was correlated with the LIS using linear regression analysis. A p value less than 0.05 was considered significant.
The Royal Brompton National Heart and Lung Hospital is a tertiary referral center and all patients had been treated for varying periods in other units prior to transfer to our own ICU. Furthermore, they were all considered too unstable to be transferred immediately to the CT scanning unit on arrival. Consequently, the mean time interval from the precipitating event leading to the development of ARDS to the initial scan was 26 days (range, 3 to 48 days). A number of patients had particularly difficult and prolonged clinical courses in the ICU and the mean time interval to the follow-up scans from the precipitating event was 108 days (range, 18 to 177 days) from the precipitating event (Table 1). All patients were mechanically ventilated during the first scan and were breathing spontaneously at the second. The mean duration of ventilatory support was 35 days (range, 13 to 54 days).