Airway occlusion assessed by single breath N2test and lung P-V curve in healthy subjects and COPD patients.
To determine whether the analysis of the slow expiratory transpulmonary pressure-volume (PL-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 PL-V curve were simultaneously recorded in 40 healthy subjects and 43 COPD patients. Onset of phase IV identified CV in SBN test (CVSBN), whereas in the PL-V curve CV was identified by: a) deviation from the exponential fit (CVexp), and b) inflection point of the interpolating sigmoid function (CVsig).



In the absence of phase IV, COPD patients exhibited a clearly discernible inflection in the PL-V curve. In the presence of phase IV, CVSBNand CVexpcoincided (CVSBN/CVexp=1.04±0.04 SD), whereas CVsigwas systematically larger (CVsig/CVexp=2.1±0.86).



The coincidence between CVSBNand CVexp, and the presence of the inflection in the absence of phase IV indicate that the deviation of the PL-V curve from the exponential fit reliably assesses CV.
Dipartimento di Fisiopatologia e dei Trapianti, Università degli Studi di Milano, Milan, Italy. Electronic address: matteo.pecchiari@unimi.it.
Matteo
M
Pecchiari
Dipartimento di Scienze Biomediche, Università degli Studi di Milano, Milan, Italy. Electronic address: danko86@hotmail.com.
Dejan
D
Radovanovic
Dipartimento di Scienze Biomediche, Università degli Studi di Milano, Milan, Italy. Electronic address: pierachille.santus@unimi.it.
Pierachille
P
Santus
Dipartimento di Fisiopatologia e dei Trapianti, Università degli Studi di Milano, Milan, Italy. Electronic address: edgardo.dangelo@unimi.it.
Edgardo
E
D'Angelo
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000403:Airway Resistance / Q000502:physiology*; D001944:Breath Tests; D003011:Closing Volume / Q000502:physiology*; D005260:Female; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D009584:Nitrogen / Q000378:metabolism*; D010991:Plethysmography; D029424:Pulmonary Disease, Chronic Obstructive / Q000473:pathology* / Q000503:physiopathology*; D055815:Young Adult
D009584:Nitrogen
Airway resistance; Closing volume; Lung pressure-volume curve; Phase IV; Single breath nitrogen test; Single breath oxygen test