Acid Base Physiology Flashcards
what are the three variables of the Henderson Hasselbach equation? which two organs have effect on these variables?
pH, bicarbonate and PCO2
the kidney sets the level of bicarbonate and the lung sets the partial pressure of CO2
on the davenport graph, what are the x and y axes? what are the lines called that relate pH and bicarbonate at constant PCO2?
the x axis are values of pH and bicarbonate is on the y axis
isobars or metabolic lines
what is the henderson hasselback equation when solving for bicarbonate?
[HCO3-}= 0.03 x PCO2 x 10^(pH-6.1)
what is the davenport graph used for?
to find one of three variables when given the other two (pH, bicarbonate and PCO2)
what do isobars or metabolic lines describe?
the changes in pH and bicarbonate that occur when an acid or base is added at constant PCO2
if a person was on a ventilator to keep constant PCO2 and acid or base would do what to the blood pH and bicarbonate levels? would this follow the davenport graph?
it would cause immediate changes in blood pH and bicarbonate before compensatory responses. the initial changes are not represented on the graph but the compensatory ones are.
what is represented within the hexagon on the Davenport graph? which PCO2 isobar is included in this hexagon?
represents the range of values for normal healthy individuals. PCO2=40 (normal ventilation
what does the CO2 absorption curve demonstrate? what line does this create when plotted on the Davenport graph?
total CO2 ([CO2] + [H2CO3] + [HCO3-] vs PCO2 and the pH that would ensue creates respiratory lines
what do respiratory lines represent?
the effect of pulmonary ventilation on blood pH and bicarbonate
why does pH decrease as PCO2 increases?
because there is a resultant increase in carbonic acid which dissociates into bicarbonate and H+
describe what determines PCO2
set by rate of alveolar ventilation which is in equilibrium with alveolar gas
what does the respiratory line describe on the Davenport graph? what determines the slope of the respiratory line?
how PCO2, [HCO3-] and pH changes with increased ventilation. slope determined by Hb concentration
when Hb is greater, what is the effect on bicarbonate with a change in pH?
more HCO3- is produced per change in pH because the H+ is buffered by the Hb.
what are some causes of hypoventilation?
COPD, asthma, airway obstruction, pneumonia, depression of respiratory control centers or weakness of respiratory muscles
what is created by the intersection between the normal metabolic line and the respiratory line?
four quadrants that describe the four primary acid base disturbances
what are the four acid base disturbances?
resipiratory acidosis, respiratory alkalosis, metabolic acidosis and metabolic alkalosis
what is the mechanism of immediate compensation for pH change? slower change?
immediate- respiratory changes
slow acting- renal mechanisms
what is the normal point on the Davenport graph?
pH is 7.4 with [HCO3-] at 24 mM and PCO2 at 40 mmHg
what is respiratory acidosis in terms of the Davenport graph? what is it caused by?
decreased pH with increased PCO2
caused by hypoventilation
at what point does hypercapnea result in stupor and coma?
when it exceeds 80 mmHg