Acid-Base Balance — Flashcards

Flashcard 31: If the pH is reduced from 7.4 to 7.3 while the alveolar PO2 remains constant at 100 mmHg, the path on a Davenport diagram follows the _____.

Answer: PCO2 isobar (specifically the 40 mmHg isobar)

Extra: A constant alveolar PO2 (100 mmHg) implies a constant arterial PCO2 (~40 mmHg) according to the alveolar gas equation. In a Davenport diagram (which plots [HCO3-] vs pH), changes occurring at a constant PCO2 follow the corresponding PCO2 isobar. This scenario represents a metabolic acidosis without respiratory compensation.