Bronchial obstruction in osteogenesis imperfecta can be detected by forced oscillation technique

Abstract

Introduction: Respiratory insufficiency is a leading cause of death in individuals with osteogenesis imperfecta (OI). However, evaluating pulmonary function in OI presents challenges. Commonly used pulmonary function tests such as spirometry and body plethysmography are sometimes difficult to perform for OI patients, and reference intervals are not always applicable. The forced oscillation technique (FOT) is a patient-friendly method for detecting respiratory abnormalities that requires no effort from the patient.

Objective: This study investigates the feasibility of FOT in the evaluation of respiratory function in the clinical management of OI patients.

Methods: Twelve OI patients, comprising eight with Sillence OI I, two with OI IV, and two with OI III, underwent spirometry, body plethysmography, and FOT, both pre-and post-administration of salbutamol.

Results: FOT measurements exhibited consistent trends that aligned with spirometry and body plethysmography findings. The resistance at 8 Hz decreased after the administration of salbutamol, indicating that FOT is able to detect bronchial obstruction and its alleviation by medication (p < 0.05). The resonant frequency during expiration was higher than during inspiration in nearly all patients, suggesting obstructive disease. The technique gives insight into both inspiratory and expiratory impairment of pulmonary ventilation. The main FOT parameters showed a relatively high repeatability in duplicate measurements.

Conclusion: Bronchial obstruction can be detected by FOT in patients with OI during quiet breathing, making it an easily executable alternative to other lung function measurements. The technique can detect the bronchodilator effect of sympathomimetic medication. It has the potential to provide information on expiratory flow limitation, pulmonary restriction, and reduced lung compliance.

Keywords: bronchial obstruction; collagen type 1; forced oscillation technique (FOT); lung function; osteogenesis imperfecta (OI).

Figure 1

Schematic drawing of the FOT device. The patient breathes through the mouthpiece and the mesh wire. The loudspeaker generates oscillations that are transferred towards the mouthpiece. Pressure is measured in the mouthpiece and airflow is derived from the pressure difference across the pneumotach head.

Figure 2

Changes in resistance of respiratory system (Rrs) at 08, 12, 16, 20 and 24 Hz. Rrs was assessed before and after salbutamol administration. Graphs on the left show Inspiration phases whereas graphs in the right show expiration phases. A decrease after salbutamol administration (in particularly noted during the exhalation) is indicative for a bronchial obstructive pattern. Rrs demonstrates a linear relationship with frequency across all patients and under all conditions (r² > 0.95).

Figure 3

Changes in reactance of respiratory system (Xrs) at 08, 12, 16, 20 and 24 Hz. Xrs was assessed before and after salbutamol administration. Left graphs indicate inspiration phases whereas right graphs indicate expiration phases. A decrease after salbutamol administration (in particularly noted during the exhalation) is indicative for a bronchial obstructive pattern. Xrs demonstrates a linear relationship with frequency across all patients and under all conditions (r² > 0.95).

Figure 4

Respiratory impedance as a function of time for different frequencies in patient 8. Lower panel: airflow (low-pass filtered): blue, inspiration; green, expiration. Upper panel: respiratory impedance for five frequency bands (8–24 Hz): blue, Rrs; red: Xrs. Grey lines indicate the upper and lower limits of the 90%-confidence intervals of Rrs and Xrs, respectively. On the left is the measurement before salbutamol administration, and on the right is the measurement after salbutamol administration. Note that Rrs significantly increases during expiration while Xrs decreases. Especially the drop in Xrs during expiration indicates expiratory flow limitation (left panel), which is largely abolished after salbutamol (right panel).