The acoustic reflection method for the assessment of paediatric upper airways.

The acoustic reflection method (ARM) is based on the analysis of the reflection of an acoustic wave in the airway, allowing the calculation of its longitudinal cross-sectional area profile and airway resistance. The ARM represents a simple, quick and totally non invasive tool for the investigation of the upper airways, requiring minimal cooperation, which makes this technique particularly suitable for children. Normal values of the minimal cross sectional area of the upper airways in children have been recently published. The ARM has shown its utility in the investigation of the nasal cavity in healthy and diseased children and of the upper airways in children with various diseases such as mucopolysaccharidosis and cystic fibrosis. This simple, rapid, and inexpensive technique seems promising for the non-invasive investigation of the whole upper airway during wakefulness in children, both in health and disease, and may constitute a complementary or alternative method to explore and follow children with anomalies of the upper airways.

Pregnancy is associated with a decrease in pharyngeal but not tracheal or laryngeal cross-sectional area: a pilot study using the acoustic reflection method.

BACKGROUND: The risk of difficult upper airway access is increased during pregnancy, especially in labor. Changes in upper airway calibre have been poorly studied during pregnancy. The acoustic reflection method is a non-invasive technique that allows a longitudinal assessment of the cross-sectional area of the upper airway from the mouth to carina. We used this technique to evaluate upper airway calibre during normal pregnancy. METHODS: We conducted a prospective, single centre, observational study with a clinical and upper airway acoustic reflection method evaluation of healthy women during the first, second and third trimesters of pregnancy, and up to two days and one month after delivery. RESULTS: Fifty women participated to the study. The mean pharyngeal cross-sectional area decreased between the first and third trimesters (P < 0.001) with no significant change of the minimal and mean tracheal cross-sectional areas. The Mallampati score increased during pregnancy between the first and third trimesters (P< 0.001). CONCLUSION: Using measurements with the acoustic reflection method, normal pregnancy is associated with a significant reduction in the cross-sectional area of the pharynx and a concomitant increase in the Mallampati score. No change was observed in the minimal and mean tracheal cross-sectional areas.