title: Platypnea induced by worsening of VA/Q inhomogeneity in the sitting position in chronic obstructive lung disease.
abstract: We report a patient with COPD who experienced severe dyspnea with a decreased PaO2 in the sitting position, largely improved in the ventral prone position (platypnea). By using an isotopic method, we showed that this phenomenon is the result of a deleterious effect of the sitting position on regional ventilation/perfusion matching. We speculated that hypoxic vascular pulmonary constriction was deficient in our patient. This hypothesis is supported by a dramatically better matching of the VA/Q ratio after treatment with almitrine bismesilate, a drug that could potentiate hypoxic pulmonary vasoconstrictive reflexes.
mesh_terms: D000368:Aged; D015765:Almitrine; D000697:Central Nervous System Stimulants / Q000627:therapeutic use*; D004417:Dyspnea / Q000209:etiology*; D006801:Humans; D000860:Hypoxia / Q000209:etiology; D008173:Lung Diseases, Obstructive / Q000150:complications* / Q000188:drug therapy; D008297:Male; D010879:Piperazines / Q000627:therapeutic use*; D011187:Posture; D014692:Ventilation-Perfusion Ratio
chemical_list: D000697:Central Nervous System Stimulants; D010879:Piperazines; D015765:Almitrine