Acid-base buffering, Henderson-Hasselbalch and respiratory compensation
How body buffers absorb acid, why the open bicarbonate system works despite its pKa, how chemoreceptors drive respiratory compensation, and how to use expected-compensation rules to find a second acid-base disorder.
Tier 1Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- Each day the body makes about 15,000 mmol of CO2 (volatile acid, cleared by the lungs) and 50 to 100 mmol of non-volatile acid (about 1 mmol/kg, cleared by the kidneys).
- Buffers blunt the immediate pH change. The lungs compensate within minutes to hours; the kidneys take 3 to 5 days.
- pH depends on the ratio of HCO3 to PaCO2, not on either value alone.
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Sources
- Guyton and Hall Textbook of Medical Physiology (14th ed.)Elsevier (Hall and Hall, 2021), 2021
- Brenner and Rector's The Kidney (11th ed.)Elsevier (Yu et al., 2020), 2020
- Physiological approach to assessment of acid-base disturbancesNew England Journal of Medicine (Berend, de Vries and Gans, 2014;371:1434-1445), 2014
- Modern quantitative acid-base chemistryCanadian Journal of Physiology and Pharmacology (Stewart, 1983;61:1444-1461), 1983
- Last updated
- 14 November 2026
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