On-line monitoring of lung mechanics during spontaneous breathing: a physiological study

Background: Monitoring the mechanics of breathing in patients with advanced chronic obstructive lung diseases prior to lung transplantation is useful to characterize changes in the mechanical properties of the lungs. On-line methods of monitoring immediately process the data for clinical decisions. However, the few available methods are so far limited to monitor respiratory mechanics in ventilator-dependent patients. We investigated whether on-line monitoring of the lung mechanics, including intrinsic PEEP, was feasible in spontaneously breathing patients. Methods: In 9 stable patients with chronic obstructive pulmonary disease (COPD) and 11 with cystic fibrosis (CF) undergoing the procedure for the lung transplantation waiting list, we applied 2 methods of on-line monitoring (modified recursive least squares, RLS and modified multiple linear regression methods, SLS) of intrinsic PEEP (P-0), dynamic lung elastance (E-Ldyn) and inspiratory resistance (R-Linsp), and compared them with an off-line graphical analysis (GA), our reference technique. Results: In CF patients, there was no difference between methods, white in COPD, the median values of E-Ldyn and R-Linsp were significantly different between GA/SLS and GA/RLS, respectively (Dunn's, p 0.05). However, the correlation was very high for all comparisons, particularly for E-Ldyn (R > 0.98) and R-Linsp (R > 0.93). Moreover, Bland-Altman plots showed that the mean differences were consistently tow and the intervals of agreement reasonable. Conclusions: Our study suggests that on-tine methods are reliable for monitoring lung mechanics in spontaneous breathing patients with severe lung diseases and could help clinicians in their decision-making process. (C) 2009 Published by Elsevier Ltd.