Eighteen patients referred to a ventilator clinic with chronic obstructive or restrictive lung disease and newly diagnosed nocturnal hypoventilation ( 10 male , median ( interquartile range ) : age 54 ( 41-61 ) years , mean daytime PaO2 9.25 ( 8.59-10 .31 ) kPa , - PaCO2 6.38 ( 5.93-6 .65 ) kPa were randomized to iVAPS and standard PS .