Discussion
We prospectively enrolled a well defined cohort of patients
with chronic respiratory failure and grouped them on
the basis of clinical and biological data into groups of
baseline condition (Groups 1 and 2) and acute respiratory
failure (Groups 3 and 4). The separation of stable and
unstable patients, on the one hand, and elevated and nonelevated
plasma bicarbonate levels, on the other hand, was
successful (see Tables 2–4).
One issue addressed in the present study was the
contribution of metabolic alkalosis to elevated plasma
bicarbonate. In the stable patients with elevated plasma
bicarbonate, the apparent strong ion difference and the
effective strong ion difference were significantly higher
than in the patients with non-elevated plasma bicarbonate.
Similar findings were observed in the unstable patients
between those with elevated and non-elevated
plasma bicarbonate. Furthermore, in the patients with
elevated plasma bicarbonate, whether stable or unstable,
the apparent strong ion difference and the effective
strong ion difference were slightly higher than those
expected from an appropriate renal adaptation to chronic
hypercapnia