The goal of this clinical trial is to compare, in healthy preterm babies, 9 doses of dorsal mechanical stimuli, in order to answer:

• if there is a dose of dorsal mechanical stimuli that improves the basal respiration.

Participants will be stimulated through a cotton shirt for one minute with each dose, while respiratory measures will be taken through a nasobuccal mask, slightly tightened by the investigator staff. All time, babies are going to be monitored and assessing that they are comfortable.

Apnea of Prematurity (AOP) occurs in 90% of infants born at ≤34 weeks of gestation. Despite current treatments, these infants continue to experience intermittent hypoxia (IH) events, which lead to subsequent complications. Dorsal and extremity kinesthetic stimulation-commonly practiced in patients experiencing apnea-has been shown to trigger the infant's own respiratory effort. Several clinical studies have demonstrated that mechanized or reactive stimulation, performed with various devices and at different intensities, decreases the number of apneas and reduces the time spent with oxygen saturation levels below 90%, a measure of IH. However, there are also reports of no favorable effects with certain other stimulation mechanisms.

To study the kinesthetic mechanism, a pilot study was conducted on 10 healthy premature infants. The infants were dorsally stimulated using a surgical glove inflated by a mechanical ventilator at rates of 20 and 40 cycles per minute, applying a standardized stimulus independent of weight and gestational age. The main results showed that, during the stimulation period, the respiratory rate decreased by 19-50% compared to baseline (without stimulation), while oxygen saturation increased by 2-7 percentage points. Additionally, it was observed that synchronization of breathing with the dorsal stimulus occurred 0-77% of the time.

These observations could be explained by the assumption that premature infants achieved more effective breaths through stimulation, recruiting more alveolar units, and potentially triggering the Hering-Breuer reflex, which inhibits subsequent respiratory efforts. Although these findings were statistically significant based on the analysis of paired sample means, not all infants responded in the same way.

Method: A pilot study involving 10 healthy preterm infants (24-34 weeks gestational age) will be conducted. The infants will be stimulated on their backs with different combinations of lifting (3, 5, and 8 mm) and frequency (20, 30, and 40 cycles per minute) using a shirt equipped with an inflating-deflating actuator. The main outcome will be a comparison of minute ventilation and tidal volumes at baseline and with the different stimulation doses. The software "Rec Trial" will be used to record vital signs, operational settings, respiratory volumes, and patterns for repeated measures ANOVA analysis. The expected results are to find the optimal combination of lifting and frequency stimulus to optimize minute ventilation and/or detect relevant respiratory patterns that improve minute ventilation.

Inclusion Criteria: 24-34 weeks of birth gestational age (BGA) preterms, healthy -

Exclusion Criteria: respiratory support, thoracic or abdominal malformations-recent surgeries, hypotonic syndromes

-

All the data is going to be registered by Rec Trial Software, anonimize and blind to everybody