The main advantages of FOT are to require only passive cooperation from the patient and to obtain new parameters that contribute to a more detailed analysis of the respiratory system. The aim of this study was to investigate the clinical application of the FOT in the evaluation of respiratory mechanical alterations resulting from increased levels of airflow obstruction in asthmatics patients, in comparison to spirometry.METHODS AND RESULTS: 111 nonsmoking subjects were analyzed using FOT and spirometry, 25 healthy (59,5±13,0 years; 66,0± 14,5 kg), without history of any pulmonary disease, and 86 asthmatics divided in 4 levels according to the spirometry report: normal to the exam (n=21; 38,4± 17,3 years; 67,5±18,9 kg), mild (n=30; 40,1±16,7 years; 72,5± 22,0 kg), moderate (n=24; 47,1± 18,6 years; 64,5± 12,5 kg) and severe (n=11; 44,1± 17,5 years; 66,8± 12,9 kg). The subjects with asthma symptoms and normal respiratory response by spirometry, constitute the level “normal to the exam”. The FOT parameters analyzed in this study were R0 (intercept resistance), the slope of the resistive component of the impedance (S) associated to non-homogeneity, both evaluated in the 4-16Hz frequency range, and Crs,dyn calculated from the reactance in 4 Hz.One-way analysis of variance (ANOVA) showed significant increases (p<0,001) in R0 and S, among the groups. It indicated an increase in the obstruction and a decrease of the pulmonary homogeneity, as the asthma obstruction was becoming harder, which is characterized by the decrease in FEV1. Although we can observe a clear reduction in the Crs,dyn with the pathology progression, it was not significant (p>0,05).
The results indicated that the increasing in the respiratory obstruction in asthmatic subjects are accompanied by homogeneity and dynamic compliance reductions.
FOT measurements supplied parameters that were in close agreement with spirometric results and pathophysiological fundamentals, confirming the great clinical potential of this technique in the evaluation of asthmatic subjects.
Spirometric and FOT results in all subjectsFEV1 (L)R0 (cmH2O/L/s)S (cmH2 O/L/s/Hz)Crs,dyn (L/cmH2O)Control Group2.2 ± 0.72.4 ± 1.1−20.5 ± 24.30.038 ± 0.020Normal to the Exam2.9 ± 0.93.0 ± 1.7−15.7 ± 30.90.040 ± 0.036Mild2.5 ± 0.93.9 ± 1.9−48.5 ± 69.50.026 ± 0.020Moderate1.6 ± 0.95.0 ± 2.6−108.6 ± 118.20.022 ± 0.024Severe1.2 ± 0.35.9 ± 3.7−167.4 ± 158.30.025 ± 0.027
P.L. Melo, None. Supported by CNPq and FAPERJ.