Periodic breathing (PB)-related intermittent hypoxia can have long-lasting deleterious consequences in preterm infants. Olfactory stimulation using vanilla odor is beneficial for apnea of prematurity in the first postnatal days/weeks. We aimed to determine for the first time whether vanilla odor can also decrease PB-related intermittent hypoxia.

This pilot study was a balanced crossover clinical trial including 27 premature infants born between 30 and 33⁺⁶ weeks of gestation. We performed 12-h recordings on two nights separated by a 24-h period. All infants were randomly exposed to vanilla odor on the first or second study night. The primary outcome was the desaturation index, defined as the number per hour of pulse oximetry (SpO₂) values <90 % for at least 5 s, together with a drop of ≥5 % from the preceding value. Univariate mixed linear models were used for the statistical analysis.

Overall, exposure to vanilla odor did not significantly decrease the desaturation index (52 ± 22 events/h [mean ± SD] on the intervention night vs. 57 ± 26, p = 0.2); furthermore, it did not significantly alter any secondary outcome. In a preliminary post hoc subgroup analysis, however, the effect of vanilla odor was statistically significant in infants with a desaturation index of ≥70/h (from 86 ± 12 to 65 ± 23, p = 0.04).

In this pilot study, vanilla odor overall did not decrease PB-related intermittent hypoxia in infants born at 30–33⁺⁶ weeks of gestation, which is when they are close to term. Preliminary results suggesting a beneficial effect in infants with the highest desaturation index, however, justify further studies in the presence of PB-related intermittent hypoxia as well as in infants born more prematurely.