Differences in spontaneous breathing pattern and mechanics in patients with severe COPD recovering from acute excerbation

The aims of this study mere to assess spontaneous breathing patterns in pat ients with chronic obstructive pulmonary disease (COPD) recovering from acu te exacerbation and to assess the relationship between different breathing patterns and clinical and functional parameters of respiratory impairment. Thirty-four COPD patients underwent assessment of lung function tests, arte rial blood gases, haemodynamics, breathing pattern (respiratory frequency ( fR), tidal volume (VT), inspiratory and expiratory time (tI and tE), duty c ycle (tI/ttot), VT/tI) and mechanics (oesophageal pressure (Poes), work of breathing (WOB), pressure-time product and index, and dynamic intrinsic pos itive end-expiratory pressure (PEEPi,dyn)). According to the presence (group 1) or absence (group 2) of Foes swings dur ing the expiratory phase (premature inspiration),20 (59 %) patients were in cluded in group 1 and 14 (41%) in group 2. Premature inspirations were obse rved 45+/-6.4 times.min(-1) (range 1-31), i.e. 20+/-21% (3.7-100%) of total fR calculated from VT tracings. In group 1 the coefficient of variation in VT, tE, tI/ttot, PEEPi,dyn, Foes and WOE of the eight consecutive breaths immediately preceding the premature inspiration was greater than that of ei ght consecutive breaths in group 2. There were no significant differences i n the assessed parameters between the two groups in the overall population, whereas patients with chronic hypoxaemia in group 1 showed a more severe i mpairment in clinical conditions, mechanics and lung function than hypoxaem ic patients in group 2. In spontaneously breathing patients with chronic obstructive pulmonary dise ase recovering from an acute exacerbation, detectable activity of inspirato ry muscles during expiration was found in more than half of the cases. This phenomenon was not associated with any significant differences in anthropo metric, demographic, physiological or clinical characteristics.