LO 1. Define the Henderson-Hasselbalch Equation for Bicarbonate/CO2.
H2O + CO2 H2CO3 H+ + HCO3- pH = 6.1 + log [HCO3] / 0.03xPCO2 For a normal bicarbonate concentration of 24 mM (at sea-level) and an arterial PCO2 of 40 Torr, the Henderson-Hasselbalch equation gives arterial blood pH of 7.40.
What is normal human pH?
normal pH is 7.4 (7.38-7.43, perhaps a bit higher here in Denver)
What are the 2 major types of buffers?
intracellular and extracellular
What are the intracellular buffers?
organic phosphates, proteins, ESPECIALLY hemoglobin
What are the extracellular buffers?
phosphate, ESPECIALLY bicarbonate and plasma proteins (mostly albumin)
pH = pK + log [A-] [HA]
For humans, the best buffer ought to be close to what pH?
______ is the conjugate base of carbonic acid.
Bicarbonate is the conjugate base of _______.
Why is bicarbonate the most important buffer in the body?
- It is present in relatively high concentration (higher than phosphate)
- The pK is relatively close to arterial pH
- The conjugate acid, CO2, is readily controlled via ventilation by the lungs
_______ has a pK of 7.9.
Deoxyhemoglobin has a pK of _____.
Carbon dioxide can then diffuse into red blood cells, where it is rapidly converted to bicarbonate and the protons are buffered by _______.
Carbon dioxide can then diffuse into red blood cells, where it is rapidly converted to ______ and the protons are buffered by deoxyhemoglobin.
The acid/base status of normal arterial blood can be altered in two general ways: (a) ________, or (b) by too much or too little acid, resulting in a metabolic disturbance.
by altering PCO2 resulting in a respiratory disorder
The acid/base status of normal arterial blood can be altered in two general ways: (a) by altering PCO2 resulting in a respiratory disorder or (b) ______.
by too much or too little acid, resulting in a metabolic disturbance
Too much acid in the blood is referred to as ______, and too much base in the blood is referred to as ______.
Because CO2 can be regulated by the _______ and bicarbonate can be regulated by the _______, the body will attempt to compensate for any acid-base disturbance to try and correct the pH back towards normal.
What is respiratory acidosis?
an increase in arterial PCO2, leading to a decrease in pH
This is an increase in arterial PCO2, leading to a decrease in pH.
What can lead to chronic respiratory failure?
- chronic bronchitis (COPD)
- Central hypoventilation disorders (obesity hypoventilation)
- neuromuscular diseases (e.g. ALS, AKA Lou Gehrig’s disease)
What causes acute respiratory failure?
1. drugs (opiates, benzos, EtOH) 2. muscle fatigue
Which compensatory mechanism is slow, taking 2-3 days to complete?
bicarbonate conservation in the kidneys
What is respiratory alkalosis?
a decrease in arterial PCO2, leading to an increase in pH
This is a decrease in arterial PCO2, leading to an increase in pH.
What are the most common causes of chronic alveolar hyperventilation?
- high altitude
- neuro disorders
- chronic salicylate (aspirin) toxicity
What are the most common causes of acute alveolar hyperventilation?
- mechanical ventilation
Compensation of respiratory alkalosis takes place through the ______, which increase the excretion of bicarbonate and lower the pH toward its normal value.
Compensation of respiratory alkalosis takes place through the kidneys, which increase the excretion of ______ and ______ the pH toward its normal value.
What is metabolic acidosis?
a primary addition of an acid other than CO2 leading to a reduction in bicarbonate