Airway occlusion assessed by single breath N 2 test and lung P-V curve in healthy subjects and COPD patients

• Published in: Respiratory physiology & neurobiology Vol. 234; pp. 60 - 68
• Main Authors: Pecchiari, Matteo, Radovanovic, Dejan, Santus, Pierachille, D’Angelo, Edgardo
• Format: Journal Article
• Language: English
• Published: Netherlands 01.12.2016
• Subjects: Adult; Age Factors; Aged; Aged, 80 and over; Airway Resistance - physiology; Breath Tests; Closing Volume - physiology; Female; Humans; Lung - physiopathology; Lung Volume Measurements; Male; Middle Aged; Nitrogen - metabolism; Plethysmography; Pulmonary Disease, Chronic Obstructive - pathology; Pulmonary Disease, Chronic Obstructive - physiopathology; Young Adult; Airway resistance; Closing volume; Single breath oxygen test; Phase IV; Single breath nitrogen test; Lung pressure-volume curve
• ISSN: 1569-9048; 1878-1519
• DOI: 10.1016/j.resp.2016.09.006

To determine whether the analysis of the slow expiratory transpulmonary pressure-volume (P -V) curve provides an alternative to the single-breath nitrogen test (SBN) for the assessment of the closing volume (CV). SBN test and slow deflation P -V curve were simultaneously recorded in 40 healthy subjects and 43 COPD patients. Onset of phase IV identified CV in SBN test (CV ), whereas in the P -V curve CV was identified by: a) deviation from the exponential fit (CV ), and b) inflection point of the interpolating sigmoid function (CV ). In the absence of phase IV, COPD patients exhibited a clearly discernible inflection in the P -V curve. In the presence of phase IV, CV and CV coincided (CV /CV =1.04±0.04 SD), whereas CV was systematically larger (CV /CV =2.1±0.86). The coincidence between CV and CV , and the presence of the inflection in the absence of phase IV indicate that the deviation of the P -V curve from the exponential fit reliably assesses CV.