A novel system for evaluation of pulmonary functional residual capacity in the intensive care unit: preliminary data
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KeywordsIntensive Care Unit Respiratory Failure Preliminary Data Ratio Increase Acute Respiratory Failure
The aim of this study is to evaluate the efficacy of pulmonary recruitment by the use of functional residual capacity (FRC) measurement with the Engström Carestation FRC INview™ system (GE Healthcare), in patients with high pulmonary recruitment range (group A) and in patients with low recruitment range (group B).
Five patients without pulmonary disease (group A) admitted to the ICU for a postoperative course and five patients admitted to the ICU for acute respiratory failure (group B) were studied with the Engström Carestation FRC system based on the evaluation of nitrogen wash-in and washout by the COVX metabolic module. The FRC, ratio (PaO2/FiO2) and static compliance (Cstat) are registered in three clinical steps: 1: ICU arrival; 2: after pulmonary recruitment with high inspiratory pressure; and 3: 3 hours after recruitment. Data are shown as the mean ± standard deviation; intragroup variables are analyzed with the Wilcoxon test (W), and intergroups variables are analyzed with the Mann–Whitney test (MW). P < 0.05 is taken as statistically significant.
FRC increase in group A is statistically significant (W) (step 1: 1,525 ± 360 ml; step 2: 1,937 ± 583 ml, P < 0.05 vs step 1; step 3: 2,592 ± 659 ml, P < 0.05 vs step 2 and P < 0.01 vs step 1) while the FRC increase in group B is not significant (step 1: 1,697 ± 210 ml; step 2: 1,757 ± 367 ml; step 3: 1,982 ± 365 ml); the FRC of group A is statistically higher than the FRC of group B in step 2 (P < 0.05 MW) and in step 3 (P < 0.01 MW). The ratio increase in group A is statistically significant (W) (step 1: 256 ± 133; step 2: 407 ± 187, P < 0.01 vs step 1; step 3: 379 ± 169, P < 0.05 vs step 1) while the ratio increase in group B is not significant (step 1: 194 ± 50; step 2: 253 ± 83; step 3: 276 ± 73); the ratio of group A is statistically higher than the ratio of group B in step 2 (P < 0.01 MW) and in step 3 (P < 0.05 MW). The Cstat increase in both groups is not significant, but in group A Cstat is statistically higher than Cstat of group B in every step (P < 0.05 MW) (step 1: 38 ± 2 ml/cmH2O for group A vs 28 ± 7 ml/cmH2O for group B; step 2: 44 ± 6 ml/cmH2O vs 36 ± 8 ml/cmH2O; step 3: 47 ± 5 ml/cmH2O vs 36 ± 8 ml/cmH2O).
With the limit of low sample size, these preliminary data suggest that the FRC evaluation system is a good parameter to optimize pulmonary recruitment and seems to be in a position to overcome the Cstat limit for the evaluation of pulmonary recruitable parenchyma.