Acid-Base Balance, Respiration, and Renal-Pulmonary Regulation

Hydrolysis Reaction

The reversible acid-base reaction in body fluids expressed as $CO_2 + H_2O \rightleftharpoons H_2CO_3 \rightleftharpoons H^+ + HCO_3^-$

Volatile Acid

An acid that can convert from a liquid state into a gaseous state and is excreted exclusively by the lungs via exhalation (e.g., carbonic acid, $H_2CO_3$).

Fixed (Non-Volatile) Acid

An acid that cannot convert into a gas and remains in liquid solution, requiring excretion exclusively by the kidneys in urine (e.g., lactic acid, ketoacids).

Normal Arterial Blood $\text{pH}$ Range

$7.35 \text{ to } 7.45$, with an absolute median normal target of $7.40$.

Normal $PaCO_2$ Range

$35\,mmHg \text{ to } 45\,mmHg$, representing the arterial volatile acid component regulated by alveolar ventilation.

Normal $HCO_3^-$ Range

$22\,mEq/L \text{ to } 26\,mEq/L$, representing the primary plasma base component regulated by the kidneys.

Kussmaul's Respirations

Deep, rapid breathing pattern triggered as a respiratory compensation mechanism to blow off excess $CO_2$ during metabolic acidosis.

Renal Compensation for Respiratory Acidosis

The retention and reabsorption of bicarbonate ($HCO_3^-$) by the kidneys over several days to elevate blood $\text{pH}$ in response to chronic $CO_2$ retention.