Cerebrospinal fluid pH in chronic respiratory acidosis.

In the proposed manuscript, we extracted arterial and cerebrospinal fluid (CSF) acid-base data from 16 published articles concerning chronic respiratory acidosis. Using a traditional narrative review style literature search, we sought published research articles wherein arterial and CSF data were available in patients with chronic respiratory acidosis. We extracted individual data where possible, and mean and standard deviation data otherwise, representing 180 patients with respiratory acidosis and 184 healthy individuals. With this data we demonstrate the differences in hydrogen ion (H⁺) buffering between the arterial blood and CSF. We also use these relationships to produce prediction equations for CSF pH in health and disease. Arterial pH explains ~61% the variation in CSF pH, while PaCO₂ explains ~55%. Using linear regression equations between arterial [H⁺]_a, pH_a, PaCO₂, and CSF pH produce mild to moderate agreement between predicted and actual CSF pH when used to predict CFS pH.