Acute respiratory failure is defined as inadequate gas exchange by the respiratory system, with the result that arterial oxygen and/or carbon dioxide levels cannot be maintained within their normal ranges. A drop in blood oxygenation is known as hypoxemia[oxygen PaO2 less than 60 mmHg (8.0 kPa)]; a rise in arterial carbon dioxide levels is called hypercapnia[ carbon dioxide PaCO2 greater than 45 mmHg (6.0 kPa)].Classification into type I or type II relates to the absence or presence of hypercapnia respectively.
Type 1 respiratory failure is defined as hypoxaemia without hypercapnia, and indeed the PaCO2 may be normal or low. It is typically caused by a ventilation/perfusion (V/Q) mismatch
Type 1 respiratory failure seen in
* Parenchymal disease (V/Q mismatch)
* Diseases of vasculature and shunts: right-to-left shunt, pulmonary embolism
* interstitial lung diseases: ARDS, pneumonia, emphysema.
Type 2 respiratory failure is caused by increased airway resistance; both oxygen and carbon dioxide are affected.
Emergency treatment follows the principles of cardiopulmonary resuscitation. Treatment of the underlying cause is required. Endotracheal intubation and mechanical ventilation may be required. Respiratory stimulants such as doxapram may be used, and if the respiratory failure resulted from an overdose of sedative drugs such as opioids or benzodiazepines, then the appropriate antidote such as naloxone or flumazenil will be given.
No comments:
Post a Comment