Background: Hypercapnic coma is a rare differential diagnosis in the unconscious patient. One underlying mechanism may be hypoventilation due to spontaneous pneumothorax. Although hypercapnia is not a typical finding in spontaneous pneumothorax in patients with otherwise healthy lungs, under certain circumstances, hypercapnia may readily develop.
Objectives: We report a rare case of profound hypercapnic coma due to spontaneous pneumothorax after contralateral pneumonectomy. In addition, we review other causes of hypercapnic coma and its outcome and discuss the relationship between arterial carbon dioxide partial pressure and level of consciousness.
Case report: An 85-year-old man without evidence of trauma or intoxication presented unconscious to our Emergency Department. The physical examination and X-ray study revealed a left-sided spontaneous pneumothorax. A right-sided pneumonectomy 25 years earlier had promoted the development of profound hypercapnic coma. After insertion of a thoracic drain, the coma rapidly resolved without any neurological deficit.
Conclusions: Although severe hypercapnia is usually due to decompensation of chronic lung disease, pneumothorax potentially may cause hypercapnic coma. Review of the literature suggests that there is no close correlation between arterial pCO(2) (partial pressure of CO(2)) levels and the degree of impairment of consciousness; however, levels exceeding 80 mm Hg are likely associated with significantly impaired consciousness. Hypercapnic coma usually resolves without neurological deficit as arterial pCO(2) tensions decline.
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