Background Preterm infants often need respiratory support. HFNV is a non-invasive method with benefits over CPAP, such as reduced nasal trauma and improved feeding.

Aim Study the impact of low (2 LPM) vs. high (6 LPM) HFNV flow rates on CO2 levels in preterm infants.

Methods Design: Prospective, crossover observational study. Participants: Preterm newborns (24-33.6 weeks' gestation) on HFNV. Procedure: Randomized flow rate adjustments, monitoring tcCO2 and other respiratory parameters over three hours.

Outcomes Primary: Change in tcCO2. Secondary: Study terminations due to unsafe CO2 levels and changes in other respiratory metrics.

Statistical Analysis Sample size: 45 infants. Analysis: Paired and unpaired t-tests for comparison within and between groups.

Background:

Preterm Births: About 10% of births are preterm, with infants at risk for respiratory distress.

Respiratory Support: Endotracheal ventilation has improved survival but increased the risk of bronchopulmonary dysplasia.

Non-Invasive Support: Nasal CPAP minimizes complications. Heated, humidified high-flow nasal ventilation (HFNV) is an alternative, providing advantages like reduced nasal trauma and improved oral feeding.

Aim:

Primary Goal: Examine changes in transcutaneous CO2 (tcCO2) levels in preterm infants when using HFNV at low (2 LPM) versus high (6 LPM) flow rates.

Hypothesis: Different HFNV flow rates will show minimal change in tcCO2 (≤5 mmHg).

Methods:

Design: Prospective, crossover observational study in Rambam NICU. Participants: Preterm newborns (24-33.6 weeks' gestation) needing HFNV. Inclusion Criteria: Stabilized HFNP settings and tcCO2, parental consent. Exclusion Criteria: Specific flow and CO2 levels, unstable conditions, or congenital malformations.

Procedure: Randomize infants into two groups starting with 2 or 6 LPM flow rates, monitoring tcCO2 over three consecutive hours with alternating flow rates.

Measurements:

Primary Outcome: Change in tcCO2 levels. Secondary Outcomes: Number of study terminations due to pCO2/TcCO2 out of safety range, changes in respiratory parameters, and episodes of desaturation or bradycardia.

Statistical Analysis:

Sample Size: 45 infants needed to detect no difference with 90% power and 5% significance level.

Data Analysis: Use paired and unpaired Student's t-tests to compare results within and between groups.

Safety Protocol: The study will terminate if significant desaturation, bradycardia, or pCO2 levels outside the safety range occur.

Inclusion criteria:

• Gestational age 240 to 336.
• At least 6 hours of stabilized HFNP settings, i.e. minor changes in settings (FiO2 ≤0.10, no change in flow).
• At least 6 hours of stabilized tcCO2, i.e. ≤5 mmHg variation.
• At least 6 hours from surfactant administration.
• Parental consent

Exclusion criteria:

• If flow is <3 and tcCO2 related pCO2 is<40mmHg.
• If Flow is ≥5 bpm and tcCO2 related pCO2 is>60mmHg.
• Unstable infants due to acute conditions (sepsis. IVH), or congenital malformations.