Differential diagnosis
Although central and obstructive sleep apnea have some signs and symptoms in common, others are present in one but absent in another, enabling differential diagnosis as between the two types:Signs and symptoms of sleep apnea generally

Signs:Observed breathing pauses during sleep
High carbon-dioxide saturation of blood, especially just before awakenings during which a patient experiences urgent need to breathe (see "Symptoms" below)
Low oxygen saturation of blood
Heart rate increase (response to both hypercapnia and hypoxemia/hypoxia), unless there also exist problems with the heart muscle itself or the autonomic nervous system severe enough to make this compensatory increase impossibleSymptoms:High frequency of urgent need to breathe upon awakening (symptom created by hypercapnia), especially among subset of awakenings occurring at times other than normal for an individuals sleep schedule and circadian rhythmsSigns and symptoms of central sleep apnea

Signs:Lack of abdominal and thoracic movement for 10 seconds or longer during sleep and coincident with breathing pausesSymptoms:Inability, either complete or without excessive effort, to voluntarily operate diaphragm and other thoracic muscles upon awakeningThe combination of this symptom with a high frequency of urgent need to breathe upon awakening is especially specific in that the co-presence of the latter symptom differentiates central sleep apneas presentation from that of sleep paralysis generally.Signs and symptoms of and conditions associated with obstructive sleep apnea
Signs:Observably ineffective respiratory movements (observable lack of air flow despite observable muscle movements indicating efforts to breathe)
Snoring (high-sensitivity but low-specificity)
Observably dry mouth or throat (high-sensitivity but low-specificity)Symptoms:Sleepiness, fatigue, or tiredness, often rising to the level of excessive daytime sleepiness
Frequent feelings of choking (airway and/or lung compression), as distinguished from mere feeling of suffocation nonspecific with respect to presence/absence of pressure, upon awakeningAssociated conditions:Opioid medication use
Large neck circumference (>16" for females, > 17" for males) (frequent causal factor and possible indirect symptom; see "Obesity" below)
Obesity (frequent causal factor and possible, albeit low-specificity, sign both direct and indirect): Obesity frequently involves accumulation of fat below the chin and around the neck, depressing the trachea when one is in the supine position, and central obesity can, depending on an individuals fat distribution, lead to increased direct pressure on the thoracic cavity and/or compressive anterior (headward) displacement of the abdominal organs, in the second case reducing space for and increasing difficulty of the motion of the diaphragm.
Magnesium oxide (MgO), or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium (see also oxide). It has an empirical formula of MgO and consists of a lattice of Mg2+ ions and O2− ions held together by ionic bonding. Magnesium hydroxide forms in the presence of water (MgO + H2O → Mg(OH)2), but it can be reversed by heating it to remove moisture. Magnesium oxide was historically known as magnesia alba (literally, the white mineral from Magnesia), to differentiate it from magnesia negra, a black mineral containing what is now known as manganese. Related oxides
While "magnesium oxide" normally refers to MgO, magnesium peroxide MgO2 is also known as a compound. According to evolutionary crystal structure prediction, MgO2 is thermodynamically stable at pressures above 116 GPa (gigapascals), and a semiconducting suboxide Mg3O2 is thermodynamically stable above 500 GPa. Because of its stability, MgO is used as a model system for investigating vibrational properties of crystals. Electric properties
Pure MgO is not conductive and has a high resistance to electric current at room temperature. The pure powder of MgO has a relative permettivity inbetween 3.2 to 9.9 
  
    
      
        k
      
    
    {\displaystyle k}
   with an approximate dielectric loss of tan(δ) > 2.16x103 at 1kHz. Production
Magnesium oxide is produced by the calcination of magnesium carbonate or magnesium hydroxide.