This chapter focuses on the use of invasive ventilation and presents more advanced methods of ventilating patients. It provides a basic knowledge of respiratory physiology and respiratory failure. Most modern intensive care units (ICUs) use positive pressure to drive air/oxygen into patients' lungs through an interface, which may be an endotracheal tube or a tracheostomy. Hence, this is known as Intermittent Positive Pressure Ventilation (IPPV). Non-invasive ventilation uses a face mask or hood, and has different terminology. Different manufacturers may have different names for these modes in their ventilators. For instance, spontaneous mode may be called Pressure Support or Assisted Spontaneous Breathing. Generally, successful weaning needs the patient's underlying health condition, which caused them to be ventilated, to start getting better. The patient also needs to be calm, neurologically intact and to have adequate strength. Some patients may wean slowly and need weaning plans that are tailored to them.