Detection of fibroproliferation by chest high-resolution CT scan in resolving ARDS

Abstract

Background: In ARDS, the extent of fibroproliferative activity on chest high-resolution CT (HRCT) scan has been reported to correlate with poorer short-term outcomes and pulmonary-associated quality of life. However, clinical factors associated with HRCT scan fibroproliferation are incompletely characterized. We questioned if lung compliance assessed at the bedside would be associated with fibroproliferation on HRCT scans obtained during the resolution phase of ARDS.

Methods: We used data from a published randomized, controlled clinical trial in ARDS. All patients were cared for using a low tidal volume strategy. Demographic data and ventilator parameters were examined in association with radiologic scores from chest HRCT scans obtained 14 days after diagnosis.

Results: Data from 82 patients with ARDS were analyzed. Average static respiratory compliance over the first 14 days after diagnosis was inversely associated with chest HRCT scan reticulation (ρ = -0.46); this relationship persisted in multivariable analysis including APACHE (Acute Physiology and Chronic Health Evaluation) II scores, initial Pao2/Fio2, pneumonia diagnosis, and ventilator days. Average static respiratory compliance was also lower among patients with bronchiectasis at day 14 (P = .007). Initial static respiratory compliance obtained within the first day after ARDS diagnosis was correlated inversely with the presence of HRCT scan reticulation (ρ = -0.38) and was lower among patients who demonstrated bronchiectasis on the day 14 HRCT scan (P = .008).

Conclusions: In patients with ARDS, diminished lung compliance measured bedside was associated with radiologic fibroproliferation 14 days post diagnosis. Establishing factors that predispose to development of excessive fibroproliferation with subsequent confirmation by chest HRCT scan represents a promising strategy to identify patients with ARDS at risk for poorer clinical outcomes.

Figures

Figure 1 –

Evidence of fibroproliferative changes on chest HRCT scan were quantitated by radiologists from the level of the aortic arch (slice 1) to 1 cm above the dome of the right hemidiaphragm (slice 5) and at three additional levels spaced equally between these two levels (slices 2-4). On average, fibroproliferative changes were most prominent in slices 3, 4, and 5 although they were observed in all slices examined. A, Bars represent mean scores for reticulation, with 95% CIs. B, Bars represent mean scores for bronchiectasis, with 95% CIs. HRCT = high-resolution CT.

Figure 2 –

Ventilator parameters recorded during the first 14 d after ARDS diagnosis were examined in conjunction with HRCT scan radiologic involvement present at 14 (SD, 2) d after ARDS diagnosis. A, B, In this cohort of patients, the average plateau pressure exposure during the first 14 d after diagnosis correlated positively with HRCT scan reticulation scores (A, ρ = 0.52) and bronchiectasis scores (B, ρ = 0.42). C, If patients were stratified according to having no bronchiectasis vs any bronchiectasis, average plateau pressure exposure among the group with any bronchiectasis was significantly higher (P < .0001). D, E, Complementary to this, the average static compliance for patients over the first 14 d after diagnosis calculated using tidal volume, plateau pressure, and positive end-expiratory pressure correlated inversely with HRCT scan reticulation scores (D, ρ = −0.46) and bronchiectasis scores (E, ρ = −0.31). F, The presence of any bronchiectasis on HRCT scan was associated with a lower average static compliance (P = .007). Horizontal bars indicate mean values; diagonal bars are regression lines. See Figure 1 legend for expansion of abbreviation.

Figure 3 –

The highest single plateau pressure, and the first available recorded plateau pressure or static compliance within 24 h of ARDS diagnosis, were examined in conjunction with HRCT scan reticulation and bronchiectasis present at 14 d (SD, 2) after ARDS diagnosis. A, In this cohort of patients, the highest plateau pressure exposure was associated with 14-d chest HRCT scan reticulation score (ρ = 0.33). B, Among patients who exhibited any bronchiectasis on their 14-d HRCT scan, on average, the highest single plateau pressure value recorded in the days prior to the HRCT scan was higher (P < .01). C, D, Similar relationships between the earliest single plateau pressure exposure obtained within 24 h of ARDS diagnosis and reticulation (C, ρ = 0.32) or bronchiectasis (D, P < .04) were also observed. E, F, Complementary to the earliest plateau pressure/HRCT scan relationships, the first recorded static respiratory compliance was inversely associated with HRCT scan reticulation (E, ρ = −0.38) and was also determined to be lower in patients with evidence of bronchiectasis (F, P = .008). Horizontal bars indicate mean values; diagonal bars are regression lines. See Figure 1 legend for expansion of abbreviation.