A Case of Chronic Mountain Sickness Diagnosed by Routine Pulmonary Function Tests

Abstract

In summary, this is a patient who presented with respiratory acidosis and cor pulmonale. The major diagnostic challenge was in differentiating primary cardiopulmonary disease from a central abnormality of ventilatory drive. The arterial blood gases showed a normal A-a gradient suggesting hypoventilation as the etiology of his hypoxemia. Pulmonary function testing showed air trapping, but a relatively normal FEV1/FVC and airways resistance. The literature suggests that most altitude natives have depressed hypoxemic and hypercapnic drives with a distinct subset demonstrating a profoundly depressed drive to ventilation. This latter group has been labeled as having chronic mountain sickness or Monge's disease. As one might expect, ventilatory control during sleep is also abnormal in these patients with CMS. Our patient indeed showed typical frequent severe desaturations with hypopnea. The diagnosis of CMS in our patient was made with routine arterial blood gases and standard pulmonary function tests. Additional tests of ventilatory responsiveness to oxygen and carbon dioxide could have been performed, but are not necessary to make the diagnosis.