Hi, Respiratory failure or distress occurs when pulmonary gas exchange is sufficiently impaired to cause hypoxaemia with or without hypercarbia. It is defined as a PaO2 It can be divided into two main categories: Type I or acute hypoxaemic respiratory failure, in which the PaO2 is Occurs with diseases that damage lung tissue, with hypoxaemia due to right-left shunts or V/Q mismatch. Common causes: Asthma Pneumonia Pulmonary oedema Adult respiratory distress syndrome Pulmonary fibrosing alveolitis Type II or ventilatory failure , with hypoxia (PaO2 8 kPa) and a PaCO2 of 6 kPa. Occurs when alveolar ventilation is insufficient to excrete the volume of CO2 being produced by tissue metabolism. Inadequate alveolar ventilation due to reduced respiratory effort, inability to overcome an increased resistance to ventilation, failure to compensate for an increase in dead space and/or CO2 production. Common causes: Chronic bronchitis and emphysema Chest wall deformities Respiratory muscle weakness (e.g. Guillain-Barre syndrome) Depression of respiratory centre (e.g. opioids) I hope this helps you and good luck with your presentation. Regards, Dr K A Pottinger, MBChB FRCA