Prevalence and characterization of spontaneous oral breathing in preterm infants.

Oral breathing is an important defense mechanism, yet its prevalence and relationship to behavioral activities have not been studied in preterm infants. We tested the hypothesis that oral breathing is rare in these infants and likely to be restricted to periods of body movements. Ten healthy preterm infants (birthweight 1300 +/- 100 g [SE]; gestational age 29 +/- 1 weeks; postnatal age 36 +/- 7 days) were studied. Ventilation was measured with a nose piece and screen flowmeter. Oral breathing was detected with a carbon dioxide sampler at the mouth. Movements were classified according to intensity into type I (localized, minor signal distortion) and type II (generalized, moderate signal distortion). Oral breathing was present 10% of the time, with a mean duration of 27 +/- 3 seconds. Of 104 episodes of oral breathing, 13 (13%) occurred during type I movement, 89 (86%; p < 0.01) during type II, and 2 (2%) in the absence of movement. The delay from beginning of movements to the beginning of oral breathing was 20 +/- 3 seconds. Nasal minute ventilation decreased from 0.203 +/- 0.013 L.min-1.kg-1 during movements in the absence of oral breathing to 0.167 +/- 0.013 L.min-1.kg-1 during movements plus oral breathing (p = 0.017). In 496 type I and II movements, the prevalence of oral breathing was 21 of 165 (13%) in quiet sleep, 37 of 194 (19%) in rapid eye movement sleep, 6 of 12 (50%) in transitional sleep, and 44 of 125 (35%) in indeterminate sleep (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)