A neonatal circuit is a specialized breathing system designed to provide respiratory support to newborns and infants in a Neonatal Intensive Care Unit (NICU). These circuits are engineered to meet the unique physiological needs of neonates, such as very small tidal volumes, high respiratory rates, and delicate airways.

• Tubing Size: Neonatal circuits typically use 10mm internal diameter tubing (compared to 15mm for pediatric or 22mm for adult circuits) to minimize “dead space” and ensure accurate delivery of small air volumes.
• Heated Wire Technology: Many circuits include internal heated wires to maintain gas temperature and prevent condensation (“rain-out”), which can block the small tubing or trigger the ventilator incorrectly.
• Humidification: Systems like the Fisher & Paykel 950™ provide heated, humidified air to protect the baby’s airway and assist natural defense mechanisms.
• Specialized Valves: High-precision expiratory valves are used to manage minute pressure differences and support spontaneous breathing.

• Ventilator Circuits (Dual Limb): Used for invasive mechanical ventilation, featuring both inspiratory (air going in) and expiratory (air coming out) limbs.
• CPAP Circuits: Specifically for Continuous Positive Airway Pressure, often used with nasal prongs or masks to keep the lungs inflated.
• Resuscitation Circuits (T-Piece): Used for immediate support at birth, allowing clinicians to set precise peak inspiratory and end-expiratory pressures manually.
• Cardiopulmonary Bypass (CPB) Circuits: Specialized, miniaturized systems used during neonatal heart surgery to circulate and oxygenate blood outside the body. 

• Dead Space: Minimized to prevent the re-breathing of carbon dioxide.
• Compliance: Circuits are designed with low compliance to ensure that the volume of gas delivered by the ventilator actually reaches the patient’s lungs rather than expanding the circuit tubing.