Abstract â–¡ 116

The ability to eliminate irritants from the upper airways and changes in breathing accompanying sneezing and crying were studied in 82 premature newborns (66 healthy and 16 newborns with respiratory distress syndrome - RDS). In healthy premature newborns, inhalation of menthol vapours (*) or an administration of nasal drops (**) to the nasal mucosa caused in 43% (*) and in 50% (**) of the cases transient respiratory inhibition and/or arrest. Mechanical stimulation of the nasal mucosa elicited an expulsive reaction - sneezing in 95 % of the stimulations. The sneezing was not preceded by a deep preparatory inspirium typical for adults. Mechanical irritation of the laryngo - pharyngeal (LPh) region produced transient apnoea in 25% of stimulations and forced respiratory reactions in 75 % of the stimulations (expiratory in 18%, inspiratory in 33% and complex cough reactions in 24 %). The LPh coughing had a pronounced inspiratory component.

The parameters of mechanics of breathing were calculated from oesophageal pressure, airflow and tidal volume during sneezing and crying in 22 healthy premature newborns. The dynamic compliance decreased and the lung resistance increased markedly during the expulsive phase of the sneezing and during crying. During the crying the inspiration: expiration ratio changed from 1 : 1.5 to 1: 5.1. This change resulted from the shortening of inspiration as well as the prolongation of expiration.

In premature newborns with RDS, mechanical irritation of the nasal mucosa elicited expulsive reactions only in 45% of the stimulations (compared to 95% in controls). The stimulation of the LPh region produced expulsive reactions in 48% of cases (compared to 75%). In other cases, inhibition of breathing was the most common reaction. The expulsive component of the sneezing, expiratory reaction, and crying was weaker in newborns with RDS in comparison to healthy controls. The inspiratory component of sneezing and coughing, on the contrary, was stronger. The increase in the heart rate to the mechanical stimulation of the airways seen in healthy newborns was not present in newborns with RDS. The maximum expiratory effort during crying was weaker in newborns with RDS than in controls. However, the maximum inspiratory effort during crying did not differ significantly in both groups.

Conclusions: Healthy premature newborns are able to eliminate actively irritants from the nose. In the reactions evoked by stimulation of the LPh region were predominant inspiratory components. Crying in newborns was accompanied by a special pattern of breathing with additional requirements to energy. In the newborns with RDS, the active elimination of irritants from the airways, cardiac responses to the upper airway stimulation and expiratory activities during crying were reduced. The inspiratory activities in all studied reactions were not diminished.