Forced oscillations and respiratory system modeling in adults with cystic fibrosis

Abstract

BackgroundThe 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.MethodsThe 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 discussionThe 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.ConclusionsThe 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.

The Role of Multidetector Computed Tomography and the Forced Oscillation Technique in Assessing Lung Damage in Adults With Cystic Fibrosis

“…Because mean reactance reflects the inhomogeneity of the respiratory system, we believe that the irregular distribution of preferential involvement in the upper lobes and changes in the small airways may explain, at least in part, the decline of mean reactance in adults with CF. 7,44 In addition, we observed higher impedance module at 4 Hz values in adults with CF than in controls. The impedance module at 4 Hz is related to the total mechanical load of the respiratory system, describing the effect resulting from respiratory system resistance, compliance, and inertia.…”

“…These regions exhibited a higher density than the parenchyma with normal aeration, which suggests the presence of areas of consolidation, collapse, and fibrosis in CF. [7][8][9][10][11][12][13][14][15][16][17][18][19] Considering clinical practice, lungvolume quantification using multidetector CT may con-tribute to the early identification of lung disease. In fact, we have found that the presence of poorly aerated regions on inspiratory lung-volume quantification using multidetector CT has good accuracy for diagnosing pulmonary disease in CF.…”

“…5,6 In this context, the forced oscillation technique, a noninvasive and easy-to-perform method, has shown great potential for evaluating pulmonary involvement in CF by assessing both resistive and reactive properties of the respiratory system. 7 Recent studies by our research group successfully applied this method in the early diagnosis of respiratory abnormalities in workers exposed to asbestos 8 and in smokers, 9 as well as in the investigation of patho-physiological changes in subjects with sarcoidosis, 10 silicosis, 11 and COPD. 12 Similar clinical studies have also been performed by other researchers who have investigated the detection of initial obstructive airway disease in subjects with asthma, 13 changes in lung mechanics after bariatric surgery, 14 airway obstruction in sleep apnea, 15 and primary Sjögren's syndrome.…”

Reference values for respiratory impedance measured by the forced oscillation technique in adult men and women

“…The reactive properties were interpreted using parameters widely used in the literature: the dynamic compliance ( C dyn ), which includes the compliance of the lung and bronchial walls, the chest wall/abdominal compartment, the thoracic gas compression and the upper airways (associated with the soft tissues of the mouth, cheeks and pharynx) . This parameter was estimated using Xrs at 4 Hz [ C dyn = −1/(2 πfX 4)]; the resonance frequency (Fr) is defined as the frequency at which Xrs equals zero; the mean reactance (Xm) is a property usually related to the respiratory system's non‐homogeneity . The total mechanical load of the respiratory system was estimated using the absolute value of respiratory impedance at 4 Hz (Z4Hz) and included the resistive and elastic effects .…”

Early pulmonary disease manifestations in cystic fibrosis mice

“…These abnormalities have been reported in young patients with mild CF (6) and in clinically stable individuals without detectable infection (7–14). Using the single frequency forced oscillation technique, decreases in reactance (Xrs) and increases in resistance (Rrs) of the respiratory system in CF patients has been reported, although the magnitude of these differences was not consistent across studies (7, 15–17), likely due to variability of clinical status in these cohorts. Taken together, these findings indicate that a phenotype of altered pulmonary function is present early in the course of CF, independent of documented infections, or onset of pulmonary symptoms.…”