Diagostic value of respiratory impedance measurements in elderly subjects

Obstructive lung disease (OLD) is highly prevalent in elderly subjects bur markedly under-diagnosed. Indeed, only 40-50% of hospitalized elderly patie nts are able to adequately perform spirometric tests This study aimed to ev aluate. in an acute-care geriatric hospital, the diagnostic value of measur ing airway impedance (Z(rs)) by the forced oscillation technique (FOT) for: (1) identifying OLD and (2) identifying responders vs, non-responders to b ronchodilators. Sixty-seven patients (aged 82 +/-8 years) underwent consecutive measurement of Z(rs) and forced expiratory volumes before and after bronchodilators. Z (rs) was measured by FOT at frequencies of 4-30 Hz. Correlations. ROC curve s and logistic regression models were established to determine the sensitiv ity (Se) and specificity (Sp) of Z(rs) in identifying OLD. Significant correlations were found between spirometric and Z(rs) measureme nts. The Z(rs) parameters yielding the best Se and Sp for detecting OLD wer e: Fn (resonant frequency: Se: 760%: Sp: 78%) and R-0 (resistance extrapola ted for a frequency of 0: Se: 76%: Sp: 74%). Using the logistic regression models. 76% of the patients were correctly classified as having OLD or not. Z(rs) was however not contributive in identifying responders to bronchodil ators. Z(rs) measurements by FOT are contributive to the diagnosis of OLD in elder ly hospitalized patients.