Cerebrospinal fluid pH in chronic respiratory acidosis.

In this article, 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 these 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 healthy and diseased conditions. Arterial pH explains ∼61% of the variation in CSF pH, whereas arterial partial pressure of CO2 ([Formula: see text]) explains ∼55%. Using linear regression equations between arterial H+ concentration, arterial pH, [Formula: see text], and CSF pH produce mild to moderate agreement between predicted and actual CSF pH when used to predict CSF pH.NEW & NOTEWORTHY Cerebrospinal fluid pH is tightly regulated in healthy individuals, but in cases of respiratory acidosis, both acute and chronic, pH becomes derailed. Acid-base buffering is only able to compensate so far before pH becomes challenged. We find that pH in the CSF may not manage acidosis as well as the arterial buffering capacity. We also leverage these data to estimate the predictive power of arterial pH on CSF pH.