Forced oscillations and respiratory system modeling in adults with cystic fibrosis

BACKGROUND The Forced Oscillation Technique (FOT) has the potential to increase our knowledge about the biomechanical changes that occur in Cystic Fibrosis (CF). Thus, the aims of this study were to investigate changes in the resistive and reactive properties of the respiratory systems of adults with CF. METHODS The study was conducted in a group of 27 adults with CF over 18 years old and a control group of 23 healthy individuals, both of which were assessed by the FOT, plethysmography and spirometry. An equivalent electrical circuit model was also used to quantify biomechanical changes and to gain physiological insight. RESULTS AND DISCUSSION The CF adults presented an increased total respiratory resistance (p < 0.0001), increased resistance curve slope (p<0.0006) and reduced dynamic compliance (p<0.0001). In close agreement with the physiology of CF, the model analysis showed increased peripheral resistance (p<0.0005) and reduced compliance (p < 0.0004) and inertance (p<0.005). Significant reasonable to good correlations were observed between the resistive parameters and spirometric and plethysmographic indexes. Similar associations were observed for the reactive parameters. Peripheral resistance, obtained by the model analysis, presented reasonable (R=0.35) to good (R=0.64) relationships with plethysmographic parameters. CONCLUSIONS The FOT adequately assessed the biomechanical changes associated with CF. The model used provides sensitive indicators of lung function and has the capacity to differentiate between obstructed and non-obstructed airway conditions. The FOT shows great potential for the clinical assessment of respiratory mechanics in adults with CF.