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

The role of respiratory function tests in infants with stridor: diagnosis at glance and follow-up

BACKGROUND

Recently, the development of advanced, noninvasive methods has allowed the study of respiratory function even in uncooperative infants. To date, there is still little data on the application of this technique in infants with suspected airway obstruction.

THE AIMS OF OUR STUDY WERE

- To evaluate the role of respiratory function testing (PFR) in the diagnosis and follow-up of infants with stridor - To evaluate the differences between patients with inspiratory stridor and expiratory stridor. - To evaluate the concordance between PFR and endoscopy.

METHODS

We enrolled infants aged < 1 year with a diagnosis of inspiratory and/or expiratory chronic stridor and a group of healthy controls. For each patient we performed PFR at diagnosis (T0) and for cases at follow-up, at 3 months (T1), 6 months (T2), 12 months (T3). At T0, all patients were classified according to a clinical score, and at follow-up, stature-ponderal growth was assessed. When clinically indicated, patients underwent bronchoscopy.

RESULTS

We enrolled 48 cases (42 diagnosed with inspiratory stridor and 6 expiratory stridor) and 26 healthy controls. At T0, patients with stridor had increased inspiratory time (p < 0.0001) and expiratory time (p < 0.001) than healthy controls and abnormal curve morphology depending on the type of stridor. At T0, patients with expiratory stridor had a reduced Peak expiratory flow (p < 0.023) and a longer expiratory time (p < 0.004) than patients with inspiratory stridor. We showed an excellent concordance between PFR and endoscopic examination (k = 0.885, p < 0.0001). At follow-up, we showed a progressive increase of the respiratory parameters in line with the growth.

CONCLUSIONS

PFR could help improve the management of these patients through rapid and noninvasive diagnosis, careful monitoring, and early detection of those most at risk.

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

Analysis of tidal breathing flow–volume (TBFV) curves is a convenient method to assess lung function in infants. We have shown that impedance pneumography (IP) is a valid method to assess overnight TBFV profiles in young children [1] and infants [2] and that certain specific curve shapes are related to symptom presentation and asthma risk [3]. We have also shown that the reduced variability of TBFV curves may be an indicator of airway obstruction in children [4–6]. However, in infants, it is unknown whether overnight TBFV variability is associated with respiratory symptoms or asthma risk.

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

Combining Bioimpedance and Myographic Signals for the Assessment of COPD During Loaded Breathing

Chronic Obstructive Pulmonary Disease (COPD) is one of the most common chronic conditions. The current assessment of COPD requires a maximal maneuver during a spirometry test to quantify airflow limitations of patients. Other less invasive measurements such as thoracic bioimpedance and myographic signals have been studied as an alternative to classical methods as they provide information about respiration. Particularly, strong correlations have been shown between thoracic bioimpedance and respiratory volume. The main objective of this study is to investigate bioimpedance and its combination with myographic parameters in COPD patients to assess the applicability in respiratory disease monitoring. We measured bioimpedance, surface electromyography and surface mechanomyography in forty-three COPD patients during an incremental inspiratory threshold loading protocol. We introduced two novel features that can be used to assess COPD condition derived from the variation of bioimpedance and the electrical and mechanical activity during each respiratory cycle. These features demonstrate significant differences between mild and severe patients, indicating a lower inspiratory contribution of the inspiratory muscles to global respiratory ventilation in the severest COPD patients. In conclusion, the combination of bioimpedance and myographic signals provides useful indices to noninvasively assess the breathing of COPD patients.

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.