Effects of nocturnal Non-Invasive Ventilation (NIV) with automatic tailoring of Positive End Expiratory Pressure (PEEP) on gas exchange and patient-ventilator interaction in COPD (Chronic Obstructive Pulmonary Disease)

Tidal Expiratory Flow Limitation (EFL T ) promotes intrinsic PEEP (PEEP i ) which increases work of breathing and patient-ventilator interaction. The application of an external PEEP adjusted to counterbalance PEEP i improves these variables. Forced oscillation technique can monitor EFLT by measuring within-breath changes in reactance at 5Hz (ΔX RS ) (Dellaca et al ERJ 2004). This technique has been incorporated in a prototype of NIV ventilator (Synchrony, Philips/Respironics, Pittsburgh, USA) able to continuously adjust PEEP to the minimum pressure needed to abolish EFL T (AutoAdjusted, AA). Eight hyercapnic COPD patients (FEV 1 %pred=41.3±14.6; FEV 1 /FVC%pred=49.3±18.6) were studied during two nights, one with their prescribed PEEP (P) and the other with AA, in random sequence. Transcutaneous CO 2 (TcCO 2 ) and standard PSG were recorded over the night. The number of ineffective efforts (IE) per hour was manually assessed and the percentage of the night spent with TcCO 2 > 45 mmHg was computed from tracings. Data is reported as median(IQR). The optimised PEEP delivered in the AA night was lower than P during 42(33)% of the night. Sleep efficacy index as computed by PSG was similar for both nights (76.8(13.3)% for AA, 73.6(11.5)% for P, p=0.58). The number of IE was reduced by 25(43)%, (p=0.02) and the percentage of night time spent in hypercapnia was reduced by 25(75)% (p=0.04) during AA night. Automatic adjustment of PEEP targeted to abolish EFL T during night improves patient-ventilator interaction and reduces hypercapnia in COPD.