Regional lung volume changes with noninvasive positive pressure ventilation in healthy adults

Abstract

Noninvasive assessments of lung volume distribution often require inhaled contrast and are limited by low regional resolution. We aimed to examine a noncontrast imaging method of spatial lung volume displacement, adapted to assess changes with noninvasive positive pressure ventilation (NIPPV). This study evaluated regional lung volume displacement in nine healthy volunteers (6 males and 3 females; ages 29–55 yr; body mass index 20.2–31.3 kg/m2) using X-ray velocimetry (XV). Participants were assessed during tidal breathing and, also with 15 cmH2O inspiratory and 5 cmH2O expiratory pressures in a supine position. Regional specific ventilation (SV) was measured during tidal breathing and NIPPV. Mean specific ventilation (MSV, mL/mL), low-volume region (LVR; % < 0.1 mL/mL), and high-volume region (HVR; % > 0.3 mL/mL) were calculated as output variables. Images were segmented into lobar as well as central and peripheral zones. Two-way ANOVA and paired t tests were used to determine regional differences within individuals and the effect of NIPPV. NIPPV increased MSV in both peripheral (P ¼ 0.01) and central (P ¼ 0.02) lung regions compared with tidal breathing. High-volume regions increased in both peripheral (P ¼ 0.04) and central regions (P ¼ 0.04) during NIPPV. This study demonstrates that noncontrast imaging techniques can assess regional lung ventilation and redistribution of lung volumes on NIPPV. Heterogeneous responses to NIPPV may be associated with a distinct distribution of ventilation, and further work is needed to ascertain differential responses to NIPPV due to lung pathology among those with respiratory disease.