Expiratory variability index is associated with asthma risk, wheeze and lung function in infants with recurrent respiratory symptoms.

Impedance pneumography enables the measurement of the expiratory variability index (EVI) at home during a night's sleep in infants with recurrent respiratory symptoms. EVI is associated with asthma risk, symptoms and lung function. https://bit.ly/2PF2cx8.

Expiratory variability index (EVI) is associated with the severity of acute bronchial obstruction in small children: A proof-of-concept study.

BACKGROUND: Lung function testing in small children is cumbersome. However, reduced variability of tidal breathing recorded using impedance pneumography (IP) during sleep was recently found to be a potential objective marker of wheeze in children aged 1-5 years. We aimed to investigate how an acute bronchial obstruction (BO) and its severity, and recovery thereof reflect in expiratory variability index (EVI). METHODS: EVI was measured using a wearable IP system (Ventica®) during sleep in 40 healthy controls (aged 1.5-5.9 years) and 30 patients hospitalized due to acute BO (aged 1.3-5.3 years). In healthy controls, EVI was measured for 1-3 nights at their homes. Patients were measured for several nights during hospitalization, as practically feasible, and at home 2 and 4 weeks post-discharge. RESULTS: We received 79 EVI results from 39 controls and 139 from 30 patients. 90% had previous BO episodes, 30% used asthma controller medication before and 100% after hospitalization. Compared to controls, EVI was significantly lower during hospitalization (P < .0001) having significant correlation with number of days to discharge (r = -.38, P = .004). At 2 or 4 weeks post-discharge, EVI was not significantly different from the controls (P = .14, P = .49, respectively). EVI was significantly associated with chest auscultation findings (P = .0001) being 17.5 (4.9) (median, IQR) with normal auscultation, 15.6 (7.4) in those with prolonged expiration and 11.4 (6.8) in those with wheeze and/or rales and crackles. CONCLUSIONS: EVI was found to be a sensitive, objective marker of acute BO, showing strong association with changes in clinical status in wheezy children aged 1-5 years.

Reduced expiratory variability index (EVI) is associated with controller medication withdrawal and symptoms in wheezy children aged 1-5 years.

BACKGROUND: Lung function testing is an essential part of diagnostic workup and monitoring of asthma, but young children are lacking easy, routine testing methods. However, recent discoveries show reduced tidal breathing variability measured using impedance pneumography (IP) at home during sleep as a sign of airway obstruction. In this study, we assessed (a) the discriminative capacity of expiratory variability index (EVI) between healthy controls and young children with recurrent wheeze on-and-off controller medication, (b) association between EVI and parentally perceived obstructive symptoms (need for bronchodilator) and (c) measurement success rate. METHODS: We included 68 patients (aged 1.0-5.6) and 40 healthy controls (aged 1.0-5.9 years). The patients were prescribed a three-month inhaled corticosteroid (ICS) treatment due to recurrent obstructive bronchitis. We measured EVI using IP at home at the end of the treatment (0W) and 2 (2W) and 4 (4W) weeks after ICS withdrawal. RESULTS: EVI was higher in controls than in patients, and significant within-patient reduction occurred at 4W as compared to 2W or 0W. Area under curve of the ROC curve (controls vs all patients) at 4W was 0.78 (95% CI 0.70-0.85). Children who were administered bronchodilator by parental decision had lower EVI than those without bronchodilator need at 4W, but not at 0W or 2W. Patients with parent-reported airway infection, but no bronchodilator need, had normal EVI. Measurement success rate was 94%. CONCLUSION: EVI was lower in patients than in controls and it reduced further after controller medication withdrawal, especially in the presence of parentally perceived wheeze symptoms. This technique shows a significant potential for routine lung function testing of wheezy young children.

Sources of variability in expiratory flow profiles during sleep in healthy young children.

Standard lung function tests are not feasible in young children, but recent studies show that the variability of expiratory tidal breathing flow-volume (TBFV) curves during sleep is a potential indirect marker of lower airway obstruction. However, the neurophysiological sources of the TBFV variability in normal subjects has not been established. We investigated sleep stages and body position changes as potential sources for the TBFV curve variability. Simultaneous impedance pneumography (IP), polysomnography (PSG) and video recordings were done in 20 children aged 1.4-6.9 years without significant respiratory disorders during sleep. The early part of expiratory TBFV curves are less variable between cycles of REM than NREM sleep. However, within individual sleep cycles, TBFV curves during N3 are the least variable. The differences in TBFV curve shapes between sleep stages are the main source of overnight variability in TBFV curves and the changes in body position have a lesser impact.

Airway obstruction is associated with reduced variability in specific parts of the tidal breathing flow-volume curve in young children.

Impedance pneumography recordings during sleep at night show reduced variability in specific parts of the expiratory flow-volume curve in children with recurrent wheeze http://bit.ly/2Wkfap0.