History
The following questions should be asked in the course of the history:
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Does the patient have a history of headaches? (With chronic hypercapnia, headaches typically occur at nighttime or when the patient awakens in the morning)
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Does the patient have disturbed sleep patterns? (Chronic hypercapnia can disturb sleep patterns, leading to a reversed sleep-wake cycle)
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Is the patient irritable or anxious, or is he or she having trouble concentrating?
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Does the patient have a possible or known exposure to sedatives (eg, narcotics, benzodiazepines, tricyclic antidepressants)? Is the patient recovering from a procedure in which general anesthesia was used?
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Does the patient have symptoms of neuromuscular weakness or paralysis? (Such symptoms might include bulbar dysfunction suggesting myasthenia gravis, proximal or distal weakness suggesting a myopathy or Guillain-Barré syndrome, and apnea associated with a traumatic injury suggesting an injury to the cervical spinal cord)
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Does the patient have a long-standing pulmonary disease, such as bronchopulmonary dysplasia, cystic fibrosis, asthma, or emphysema?
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Does the patient have an acute change in mental status (eg, signs of stroke, postictal state)? If so, is the change in mental status associated with a fever, which may suggest encephalitis or meningitis? Does the patient have signs of increased intracranial pressure (eg, headaches, visual changes, or emesis)?
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Does the patient have a potential for an anaphylactic reaction?
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Does the patient have a potential traumatic mechanism leading to brain injury?
Physical Examination
Neurologic findings associated with respiratory acidosis include the following:
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Early signs include anxiety, disorientation, confusion, and lethargy
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Somnolence or coma occurs when the arterial partial pressure of carbon dioxide (Pa CO2) exceeds 70 mmHg
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Tremor, myoclonus, or asterixis are occasionally seen
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Brisk deep tendon reflexes are seen in mild-to-moderate respiratory acidosis
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Depressed deep tendon reflexes are seen in severe respiratory acidosis
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Papilledema or blurring of the optic disc may be present
Cardiovascular findings associated with respiratory acidosis include the following:
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Tachycardia
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Bounding arterial pulses
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Hypotension (severe respiratory acidosis or acidemia and hypoxemia)
Cutaneous findings associated with respiratory acidosis include the following:
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Warm, flushed, or mottled skin
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Diaphoresis
Respiratory findings associated with respiratory acidosis include the following:
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Acute hypercapnia is seen in association with increase work of breathing
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Tachypnea, dyspnea, or deep labored breaths may be observed
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Accessory muscle use and nasal flaring are usually present
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With central or peripheral nervous system disease, respiratory distress may not be present
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Decreased aeration, crackles, wheezes, or other signs of airway disease may be observed
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Clubbing is a sign of chronic respiratory disease
