Loop gain in paediatric sleep-disordered breathing: A different story from adults

Obstructive sleep apnea in children with Down syndrome: contribution of upper airway and chemosensitivity

BACKGROUND

The high prevalence of obstructive sleep apnea syndrome (OSAS) in children with Down syndrome (DS) has been attributed to a reduced upper airway size, while the role of ventilatory control is unclear. The objectives of our case-control study were to evaluate the upper airway reduction in children with DS and moderate to severe OSAS as compared to typically developing (TD) children with similar OSAS severity and to evaluate the degree of chemical loop gain modifications including its components: controller and plant gains (CG, PG).

METHODS

Thirteen children with DS were matched for age, sex, OSAS severity and ethnicity with 26 TD children. They had undergone acoustic rhinometry and pharyngometry, chemical LG obtained during awake tidal breathing measurement and hypercapnic-hyperoxic ventilatory response testing.

RESULTS

As compared to TD, children with DS depicted reduced oropharyngeal dimensions, significantly lower CG and LG and no different PG. Their hypercapnic ventilatory response slopes were not different.

CONCLUSIONS

We concluded that the decreased CG in DS was related to decreased peripheral chemoreceptor sensitivity, and while central chemosensitivity was normal, the former explained the increased end-tidal PCO2 observed in children with DS as compared to TD. Pharyngeal dimensions are reduced in children with DS and OSAS.

IMPACT

Reduced upper airway size and nocturnal alveolar hypoventilation in children with Down syndrome (DS) have been previously reported. We confirmed that children with DS and moderate-to-severe OSA have reduced oropharyngeal size as compared to typically developing children with similar OSAS severity and demonstrated decreased peripheral chemosensitivity explaining the alveolar hypoventilation observed in children with DS. Central chemosensitivity appears to be intact in children with DS and moderate to severe OSAS Our results support growing evidence that Down syndrome is associated with autonomic nervous system dysfunction.

Clinical Characteristics Combined with Craniofacial Photographic Analysis in Children with Obstructive Sleep Apnea

Purpose

Distinguishing obstructive sleep apnea (OSA) in a high-risk population remains challenging. This study aimed to investigate clinical features to identify children with OSA combined with craniofacial photographic analysis.

Methods

One hundred and forty-five children (30 controls, 62 with primary snoring, and 53 with OSA) were included. Differences in general demographic characteristics and surface facial morphology among the groups were compared. Risk factors and prediction models for determining the presence of OSA (obstructive sleep apnea-hypopnea index>1) were developed using logistic regression analysis.

Results

The BMI (z-score), tonsil hypertrophy, and lower face width (adjusted age, gender, and BMI z-score) were showed significantly different in children with OSA compared with primary snoring and controls (adjusted p<0.05). The screening model based on clinical features and photography measurements correctly classified 79.3% of the children with 64.2% sensitivity and 89.1% specificity. The area under the curve of the model was 81.0 (95% CI, 73.5-98.4%).

Conclusion

A screening model based on clinical features and photography measurements would be helpful in clinical decision-making for children with highly suspected OSA if polysomnography remains inaccessible in resource-stretched healthcare systems.

Oropharyngeal obstruction and respiratory system compliance are linked to ventilatory control parameters in pediatric obstructive sleep apnea syndrome

Instable ventilatory control is an endotypic trait of obstructive sleep apnea syndrome (OSAS). This study aimed to evaluate the relationships between the anatomical compromise of the upper (oro- and naso-pharynx) and lower airways and ventilatory control (measured by chemical loop gain) in otherwise healthy children suffering from moderate to severe OSAS (apnea hypopnea index ≥ 5/hour). The children underwent ear, nose and throat examination, measurement of impedance of the respiratory system that allowed characterizing peripheral lung mechanics using the extended Resistance-Inertance-Compliance model. Physiologically constrained analytical model based on tidal breathing analysis allowed for the computation of steady-state plant gain, steady-state controller gain (CG0) and steady-state loop gain (LG0). Medium-frequency components of the feedback control system were then deduced. Fifty children (median age 11.2 years) were enrolled. Oropharyngeal obstruction was associated with decreased CG0 (0.6 [0.2; 1.0] vs 1.5 [0.5; 6.6] L.s^- 1.mmHg^- 1, p = 0.038) and LG0 (0.4 [0.2; 1.1] vs 1.2 [0.4; 9.3], p = 0.027), while nasal obstruction did not modify ventilatory control parameters. In a multivariate analysis Medium-Frequency PG was negatively related to minute ventilation and respiratory system compliance. Both upper (tonsil hypertrophy) and lower (compliance of respiratory system) airways are linked to ventilatory control in children with moderate to severe OSAS.