[Evaluation of total and inflated lung volumes by a quantitative study using computerized tomography in patients with...

Our study was aimed at developing a method to assess lung volumes and relative percentages of well-inflated lung parenchyma in Adult Respiratory Distress Syndrome (ARDS) patients by processing conventional CT examinations of the lung and at investigating the prognostic value of CT findings. Fourteen patients (5 women and 9 men, age range: 35-79 years) admitted to the intensive care unit January, 1992, to June, 1994, because of severe ARDS, and with lung injury scores exceeding 2.5, were submitted to CT. A homologous group of 14 patients matched for sex and age and with normal lungs was examined as a control group to investigate the accuracy of our method. Two examinations were obtained in 7 of 14 ARDS patients; the trend of lung volumes and of the relative rates of well-inflated parenchyma could thus be calculated. During the examination, we maintained in all ARDS patients the same ventilatory pattern used in the intensive care unit. Consequently, in 18/21 examinations scans and respiratory phases were not correlated. In the control group no statistically significant differences were observed between the scans obtained with (inspiratory apnea) and without coordination with the respiratory phase. As for lung volumes, our results in normal subjects showed a good correlation with normal spirometric data. In ARDS patients lung volumes, although reduced, did not correlate with prognosis. As for the percentage of well-inflated parenchyma in ARDS patients, we observed a good correlation with prognosis in the patients submitted to two examinations and, in all patients, a good correlation with D(A-a)O2 index (p < 0.05), PaO2/FiO2 index (p < 0.005) and with the rate of arteriovenous shunt (p < 0.001). In conclusion, our results show that CT of the lung is a reliable and repeatable method for the functional assessment of the lung in ARDS patients.