Disorders of ventilation

Decreased ventilatory drive

Decreased mental status (eg, caused by head injury, oversedation, sepsis, shock, or stroke)

Obstructed ventilation

Bronchospasm

Dislodgement of endotracheal tube

Mucus plugging of the airways or endotracheal tube

Severe pain in the chest, abdomen, or both

Rib fractures

Thoracic or abdominal surgery

Disorders of oxygenation

Pulmonary causes

Acute respiratory distress syndrome

Atelectasis, pneumonia, pneumothorax, pulmonary embolus, pulmonary contusion, aspiration pneumonitis

Nonpulmonary causes

Iatrogenic fluid overload

Heart failure (eg, due to exacerbation of underlying disease or to acute myocardial infarction)