Inspiratory pressure support is a mode of partial ventilatory support which can be defined as patient-initiated, pressure-targeted and patient-interrupted. Addition of pressure support to a spontaneously breathing patient results in a reduction of respiratory rate and an increase in tidal volume. It corrects arterial blood gas abnormalities resulting from rapid shallow breathing and reduces the work of breathing. The synchrony between the patient's demand and ventilator assistance is optimized and allows an improvement in the efficiency of the spontaneous effort of the patient. Since it is not volume-targeted, variation in delivered ventilation may occur in unstable patients or in patients with fluctuations in respiratory drive. Clinical advantages have been found using pressure support during the process of weaning from mechanical ventilation in patients with prolonged difficulty in tolerating discontinuation from mechanical ventilation. Lastly, it can be delivered via a face-mask to avoid the need for endotracheal intubation in patients with hypercapnic respiratory failure.