All patients had an LIS in excess of 2.5 on admission to our ICU, but this had fallen to 1.72 ±0.14 at the time of the initial scan (Table 1). Mean LIS at follow-up was 0.6 ±0.17. There was a significant correlation between the extent of CT abnormalities and LIS for all time points (r=0.75, p<0.01).
We have shown that the CT changes observed in patients with ARDS who survive are variable in extent and character and change considerably over time as the disease resolves. Moreover, the morphologic and functional abnormalities observed in this in certain diffuse lung diseases, particularly those involving fibrosis. The patients in our population were considered too unwell to tolerate open lung biopsy to allow pathologic correlation with the CT findings. generic for doxycycline
Furthermore, the lung injury in ARDS is known to be patchy and representative sampling is difficult. However, the range of histopathologic changes seen in ARDS have been well-documented in samples taken from patients with disease of varying severity and in different stages of evolution up to and including post mortem. The natural history of the syndrome has also been characterized using plain chest radiography. In most cases, the disease process is nonuniform, some parts of the lung showing no changes at all, but overall three distinct stages can be recognized.
Stage 1 can be regarded as radiologieally latent and occurs during the first few hours following any precipitating insult, often antedating the need for mechanical ventilatory support. At a pathologic level, pulmonary capillary congestion, endothelial cell swelling, and extensive microatelectasis are described. Prior to ventilation, lung volumes may be decreased reflecting the onset of diffuse microatelectasis. At this stage, there is only a small increase in extra vascular water content of lungs, which may be reflected in subtle peribronchovascular obscuration or diffuse ground-glass opacification.” This phenomenon was observed at least in part on the first CT scan taken in all patients in the current study, although to a very variable extent.