Normative Reference Equations of Airway Dynamics Assessed by Whole-Body Plethysmography During Spontaneous Breathing Transitionally Evaluated in Infants, Children and Adults

Background In contrast to the conventional parameters of airway dynamics mostly obtained by the two-point approximation method, the effective specific airway resistance (sReff), its reciprocal value the effective specific airway conductance (sGeff) resp., obtained by the integration of the entire tidal breathing loop, features promising target parameters for differentiating between individual functional disease patterns. sReff can be computed as the ratio between the integral of the area enclosed by the plethysmographic shift volume–tidal flow loop, featuring the specific aerodynamic work of breathing (sWOB), and the tidal flow–volume loop, sGeff by the ratio of the integral of the tidal flow–volume loop and the sWOB, respectively. However, normative values for sWOB, sReff and sGeff at resting level are not yet available.Methods We aimed to define reference equations in healthy infants (n=28), children (n=47) and adults (n=273), which incorporates not only the standard anthropometric measures, but also lung volume and breathing pattern indices (including both volume and time indices). Retrospectively exported data were collected from databases of 5 Swiss lung function centres, in which plethysmography (Jaeger Würzburg, Germany) was performed using standard techniques (ATS-ERS criteria) for the assessment of airway dynamics, static lung volumes and forced breathing flow-volume loops.Results Using multi-linear modelling, reference equations of sReff, sGeff, and sWOB could be defined taking as independent parameters apart from anthropometric parameters, also parameters given by the ratio between the tidal volume (VT) and functional residual capacity (FRCpleth), and the ratio between VT and inspiratory time (VT/TI). In addition, we examined the effect of age on the breathing pattern, the relationship between breathing pattern (tidal volume) and timing (inspiratory time).Conclusions An alternative statistical approach to define reference equations of airway dynamics reveals that apart from the subject’s anthropometric measurements, parameters of the magnitude of static lung volumes, the breathing pattern, and the timing of breathing are co-variants of reference equations of airway dynamics over a large age range.

Effect of sleep on upper airway dynamics in obese adolescents with obstructive sleep apnea syndrome

Study Objectives The biomechanical basis of obstructive sleep apnea syndrome (OSAS) may influence upper airway dynamics. In this study, we investigate dynamic changes during respiration in wakefulness and sleep in obese adolescents with and without OSAS. Methods Respiratory-gated dynamic magnetic resonance imaging (MRI) at the retropalatal and retroglossal regions was performed with simultaneous measurement of SpO2 and nasal-oral mask airflow and pressure. Airway cross-sectional area (CSA) was determined using AMIRA. Percent change in CSA was calculated from five continuous tidal breaths in states of wakefulness and sleep. Mixed effects models were used to evaluate interactions between group (OSAS/control), site (retropalatal/retroglossal), and stage (wake/sleep). Results We studied 24 children with OSAS (mean age 15.49 ± 2.00 years, mean apnea–hypopnea index [AHI] 16.53 ± 8.72 events/h) and 19 controls (mean age 14.86 ± 1.75 years, mean AHI 2.12 ± 1.69 events/h). Groups were similar in age, sex, height, weight, and BMI Z-score. Participants with OSAS had a 48.17% greater increase in percent change of airway CSA during sleep than controls (p < 0.0001), while there was no difference between groups during wakefulness (p = 0.6589). Additionally, participants with OSAS had a 48.80% increase in percent change of airway CSA during sleep as compared with wakefulness (p < 0.0001), whereas no such relationship was observed in controls (p = 0.5513). Conclusions This study demonstrates significant effects of sleep on upper airway dynamics in obese children with OSAS. Dynamic MRI with physiological data can potentially provide further insight into the biomechanical basis of OSAS and assist in more effective management.

Cross-sectional study of effect of adiposity and hypertensive states on airway dynamics

Background: Adiposity and hypertensive states are major burden for community. It causes many health-related issues, including problems related to respiratory system. It is proposed that pulmonary functions can be affected in obese hypertensive and obese normotensive adults compared to non-obese normotensive adults. The objective of the study was to find out the effect of adiposity and hypertensive states on the airway dynamics.Methods: About 30 male obese normotensives and 30 male obese hypertensive subjects were selected as study participants. 30 age-controlled non-obese, normotensive males were selected as controls. All participants were in the age group of 40 to 60 years. The pulmonary functions measured were FVC, FEV1, FEV1% and PEFR. All the participants performed 3 attempts of spirometry and maximum among the three recordings were used for analysis. ANOVA followed by Post hoc analysis to find out any significant differences between these groups. Spearman’s rank correlation was used.Results: There was a statistically significant differences in BMI between the group I and group II and III. There was a significant difference in SBP and DBP between obese normotensive (group II) and obese hypertensive (group III) subjects. There were significant decline in % predicted values of PFT parameters, on comparing obese normotensive and obese hypertensive when compared to non-obese normotensive participants. There were statistically significant negative correlations between age and FEV1 as well as BMI and PEFR.Conclusions: There was a significant decrease the pulmonary functions in obese normotensive and obese hypertensive adults in comparison to non-obese normotensive adults. It can be concluded that body weight and adiposity as well as high blood pressure creates deleterious effect on airway dynamics.