Respiratory mechanics in COPD patients who failed non-invasive ventilation: role of intrinsic PEEP.

Non-invasive positive pressure ventilation (NPPV) is the first choice to treat exacerbations in COPD patients. NPPV can fail owing to different causes related to gas exchange impairment (RF group) or intolerance (INT group). To assess if the respiratory mechanical properties and the ratio between the dynamic and static intrinsic positive end-expiratory pressure (PEEP(i),dyn/PEEP(i),stat), reflecting lung mechanical inequalities, were different between groups, 29 COPD patients who failed NPPV (15 RF and 14 INT) were studied, early after the application of invasive ventilation. Blood gas analysis, clinical status, and mechanical properties were measured. pH was higher in INT patients before intubation (p<0.001). PEEP(i),dyn/PEEP(i),stat was found higher in INT group with (p=0.021) and without PEEP (ZEEP, p<0.01). PEEP(i),dyn/PEEP(i),stat was exponentially associated with the duration of NPPV in INT group (p=0.011). INT and RF patients had similar impairment of respiratory system resistance and elastance.