Respiratory sensitivity to carbon dioxide in schizophrenia

Respiratory sensitivity was evaluated in 10 patients with schizophrenia and 10 normal control subjects utilizing a rebreathing system and measurements of the changes in the mouth occlusion pressure in 100 ms and ventilation in response to the increase in end-tidal PCO2 (PetCO2). Although ventilation response was similar in both groups, we noted that the occlusion pressure response was more variable (coefficient of variability, CV = 17.5%) and the correlation coefficient (r = 0.75 +/- 0.13) lower in the patients with schizophrenia compared to controls (CV = 4.6%; r = 0.90 +/- 0.04). Apnea threshold was also lower in patients with schizophrenia (29.03 +/- 12.73 Torr, mean +/- SD) compared to controls (39.5 +/- 4.5 Torr). Furthermore, schizophrenia patients showed a significant positive and negative correlation between occlusion pressure response and age (r = 0.73; p less than 0.001) and estimated duration of schizophrenia (r = 0.65; p less than 0.05). We conclude that the apnea threshold is lower and the respiratory sensitivity to CO2 is more variable in patients with schizophrenia compared to normal subjects.