Assessment of respiratory mechanics in patients with sarcoidosis using forced oscillation: correlations with spirometric and volumetric measurements and diagnostic accuracy.

BACKGROUND: The forced oscillation technique (FOT) is a promising method for providing a detailed analysis of respiratory mechanics during spontaneous breathing. There is limited data about the use of FOT in patients with sarcoidosis.
OBJECTIVES: The aims of this study were to test the ability of FOT to describe the changes in respiratory mechanics in sarcoidosis and to evaluate the clinical potential of FOT.
METHODS: Twenty healthy subjects and 31 patients were studied. All subjects performed spirometric exams, and pulmonary volumes were measured in patients. Resistive data were interpreted using the zero-intercept resistance (R0), the slope of the resistive component of the impedance (S), and the mean resistance (Rm). The analysis of reactance was used to measure the mean reactance (Xm) and the respiratory system dynamic compliance (C(dyn)). The total mechanical load was evaluated using the absolute value of the respiratory impedance (Z4Hz).
RESULTS: In close agreement with pathophysiological fundamentals, significant (p < 0.001) increases in R0, Rm, and Z4Hz, and reductions in C(dyn) (p < 0.003) were observed. S and Xm presented smaller modifications (p < 0.02). All FOT parameters were significantly correlated with spirometric indices. Z4Hz was the most adequate parameter for clinical use (Se = 75%, Sp = 75%), followed by R0 and Rm.
CONCLUSIONS: FOT parameters were consistent with the pathophysiology of sarcoidosis and were also able to detect the effects of this disease. Because the FOT is easy to perform, such a technique may represent an alternative and/or a complement to other conventional exams to help the clinical evaluations of sarcoidotic patients. Copyright 2009 S. Karger AG, Basel.