<P> In those with deep unconsciousness, there is a risk of asphyxiation as the control over the muscles in the face and throat is diminished . As a result, those presenting to a hospital with coma are typically assessed for this risk ("airway management"). If the risk of asphyxiation is deemed high, doctors may use various devices (such as an oropharyngeal airway, nasopharyngeal airway or endotracheal tube) to safeguard the airway . </P> <P> Physical examination is critical after stabilization . It should include vital signs, a general portion dedicated to making observations about the patient's respiration (breathing pattern), body movements (if any), and of the patient's body habitus (physique); it should also include assessment of the brainstem and cortical function through special reflex tests such as the oculocephalic reflex test (doll's eyes test), oculovestibular reflex test (cold caloric test), nasal tickle, corneal reflex, and the gag reflex . </P> <P> Vital signs in medicine are temperature (rectal is most accurate), blood pressure, heart rate (pulse), respiratory rate, and oxygen saturation . It should be easy to evaluate these vitals quickly to gain insight into a patient's metabolism, fluid status, heart function, vascular integrity, and tissue oxygenation . </P> <P> Respiratory pattern (breathing rhythm) is significant and should be noted in a comatose patient . Certain stereotypical patterns of breathing have been identified including Cheyne--Stokes, a form of breathing in which the patient's breathing pattern is described as alternating episodes of hyperventilation and apnea . This is a dangerous pattern and is often seen in pending herniations, extensive cortical lesions, or brainstem damage . Another pattern of breathing is apneustic breathing, which is characterized by sudden pauses of Inhalation and is due to a lesion of the pons . Ataxic breathing is irregular and is due to a lesion (damage) of the medulla . </P>

Comas are most likely to be reversible when the coma is due to