Functional Properties of the Human Lungmeasured duringspontaneous and modified respiration in COPD Patients

Rationale:patients began to cough and expectorate few minutes since starting inhalation of tiny amounts of a diagnostic aerosol. This observation led to develop a device (UNIKO, MPR) delivering positive pressure of 1-2 mmHg at airway opening in proto-expiration to counteract airways expiratory closure in these patients. METHODS: in 5 COPD patients (mean±SD: age = 67±9.8 yrs, FEV1/FVC % =35.2±6.8, FEV1 % pred =37±5, RV % pred =183±35, TLC % pred =118±18, DLCO % pred =62±19) airflow and mouth and esophageal pressures were simultaneously computer acquired for 10 minutes at baseline (B), 15 minutes with UNIKO on at the mouth (U), and 5 minutes post UNIKO (P). Lung compliance (CL) and resistance (RL) were obtained by, breath to breath, computer processing all the respiratory signals thus upgrading the analogic approach by oscilloscope of Mead and Whittenberger (JAP 1953; 5:779-796). RESULTS: in each breath, elastic lung pressure (PCL) was generated multiplying 1/CL (i.e. elastance) times instantaneous values of tidal volume (VT) whereas frictional lung pressure (PRL) was obtained by substracting PCL from transpulmonary pressure (PL). Instantaneous RL as PRL/airflow (cmH2O/L/min) was computed, breath by breath, in inspiration (RLi) and expiration (RLe) over a representative number of breaths for each of the conditions B, U, and P. RLi showed a trend to decrease from B to U (4.5±2.5 vs 4.1±2.6, respectively, p=0.067), similar values in B and P, and a non significant increase from U to P. Values of RLe were higher, not significantly in this small sample, than those of RLi in B (p=0.225), U (p=0.308), and P (p=0.254), respectively. RLe decreased from B to U (9.4±9.9 vs 7.1±8.1, respectively, p=0.053), remained lower but not significantly respect to B in P (p=0.214), and showed similar values in U and P (p=0.745). CONCLUSIONS: expiratory lung resistances were higher than inspiratory resistances in the 5 COPD patients studied. By raising airway opening pressure by 1-2 mmHg in proto-expiration, results suggested that expiratory lung resistances decreased in patients with moderate to severe chronic obstructive pulmonary disease.