Basic indices of pulmonary mechanics can be measured in real time and displayed on the ventilator screen and can assist in guiding and individualising respiratory care in newborn infants receiving respiratory support. The compliance of the respiratory system is an index of how much pressure needs to be applied to the lungs to achieve a certain change in lung volume. Compliance is typically low in respiratory distress syndrome and increases post administration of exogenous surfactant. The resistance of the respiratory system is an index which describes the relative difficulty with which gas flows through the airways and can be increased either due to acute mechanical complications or in the context of specific diseases with airflow limitation such as bronchopulmonary dysplasia. The inspiratory time constant is the product of the compliance and the resistance and can be used to describe how long it takes for the pressure applied at the level of the upper airway or the endotracheal tube to be delivered down to the distal lung parts. The time constant is determined by the mechanical properties of the lung and can assist in fine tuning the inspiratory time during invasive ventilation.