What are the differences between Type I and Type II respiratory failure in terms of ABG measurements and typical causes?

Type I respiratory failure shows a low arterial oxygen (PaO2 <8 kPa) and low oxygen saturation (SaO2 <92%), while Type II also has a low PaO2 but additionally a high arterial carbon dioxide (PaCO2 >6.5 kPa) with a normal or acidotic pH. Causes differ: Type I is linked to conditions such as severe asthma, pneumonia, pulmonary embolism, and ARDS, whereas Type II occurs with COPD exacerbations, neuromuscular disorders, or opiate/barbiturate overdose.

The two types of acute respiratory failure are distinguished by arterial blood gas (ABG) measurements. Type I failure is characterized by hypoxemia without hypercapnia, specifically a PaO2 below 8 kPa and an SaO2 below 92%. Typical causes include severe acute asthma, pneumonia, pulmonary embolism, emphysema, fibrosing alveolitis, and acute respiratory distress syndrome (ARDS). Type II failure, also called hypercapnic respiratory failure, is recognized by a low PaO2 (below 8 kPa) together with a high PaCO2 (above 6.5 kPa) and a blood pH that is either normal or acidotic. It most often occurs in people with acute exacerbations of COPD, in neuromuscular disorders such as Guillain-Barré syndrome, polio, and myasthenia gravis, or after drug overdose with opiates or barbiturates.