1. What is the Henderson-Hasselbalch Equation?

The Henderson-Hasselbalch equation is a mathematical expression used to calculate the pH of a buffer solution. In clinical medicine, it's applied to arterial blood gas analysis to determine acid-base status from bicarbonate and carbon dioxide partial pressure measurements.

2. How Does the Calculator Work?

The calculator uses the Henderson-Hasselbalch equation:

Where:

• \( [HCO_3^-] \) — Bicarbonate concentration (mmol/L)
• \( pCO_2 \) — Partial pressure of carbon dioxide (mmHg)
• 0.03 — Conversion factor for CO₂ solubility
• 6.1 — pKa of carbonic acid at 37°C

Explanation: The equation describes the relationship between pH, bicarbonate concentration, and carbon dioxide partial pressure in the bicarbonate buffer system, which is the primary buffer system in blood.

3. Importance of Arterial pH Calculation

Details: Accurate pH calculation is essential for assessing acid-base balance, diagnosing respiratory and metabolic disorders, and guiding appropriate treatment in critical care settings.

4. Using the Calculator

Tips: Enter bicarbonate concentration in mmol/L and pCO₂ in mmHg. Both values must be positive numbers. The calculator provides the estimated arterial pH based on these parameters.

5. Frequently Asked Questions (FAQ)

Q1: What is the normal range for arterial pH?
A: Normal arterial pH ranges from 7.35 to 7.45. Values below 7.35 indicate acidosis, while values above 7.45 indicate alkalosis.

Q2: How accurate is this calculation compared to measured pH?
A: While the equation provides a good estimate, actual measured pH from arterial blood gas analysis is more accurate as it accounts for all buffer systems.

Q3: When should arterial blood gas analysis be performed?
A: ABG analysis is indicated in patients with respiratory distress, metabolic disorders, critical illness, or when monitoring response to treatment for acid-base imbalances.

Q4: What factors can affect the accuracy of this calculation?
A: Temperature variations, other buffer systems, and certain metabolic conditions can affect the relationship between bicarbonate, pCO₂, and pH.

Q5: Can this calculator be used for venous blood gases?
A: While the same equation applies, venous pH is typically 0.03-0.05 units lower than arterial pH due to higher CO₂ content in venous blood.