Integrated control of ventilation Flashcards
Blood pH is proportional to the ratio of
[HCO3-] to PaCO2
A change in pH in regards to homeostasis is referred to as
Acidosis (Decrease)
Alkalosis (Increase)
In homeostasis, low pH accompanied by high PaCO2 is referred to as
Respiratory acidosis
Hypoventilation is responsible (more CO2 in arterial blood, increase in H+, decrease in pH as less ventilation)
High pH accompanied by low PaCO2 is referred to as
Respiratory alkalosis
Hyperventilation responsible for decrease in CO2 (decrease in H+ -> higher pH, lower arterial conc of CO2 (hypocapnia))
Low pH accompanied by low [HCO3-] is referred to as
Metabolic acidosis
Excessive metabolic acid production/increased excretion of HCO3- responsible.
High pH accompanied by high [HCO3-] is referred to as
Metabolic alkalosis
Reduced metabolic acid production/reduced excretion of HCO3- responsible for increased pH
Describe the effect of acidosis
Increased H+, increased activation of respiratory chemoreceptors, increased respiratory activity. Increase in CO2 removal from the body, increasing blood pH until normal level re-established.
Describe the effect of alkalosis
Decreased H+, decreased activation of chemoreceptors, decreased respiratory activity. Accumulation of CO2 decreases blood pH until normal levels re-established.
Which conditions are associated with each acid-base balance
Resp Acidosis - COPD (more CO2, hypoventilation, resp failure)
Resp alkalosis - Anxiety, altitude-induced hyperventilation -> Hyperventilation and excessive CO2 removal
Metabolic acidosis -> Excessive acid production (sepsis, ketoacidosis) or excessive excretion of HCO3 (Renal failure)
Metabolic alkalosis -> Excessive consumption of basic substances (antacid abuse), excessive excretion of acid from body (vomiting), deficient absorption of HCO3 from GI tract (Chronic diarrhoea) or excessive reabsorption of HCO3 (renal dysfunction)
Describe how levels of potassium within the blood are maintained.
Hydrogen efflux, sodium influx followed by sodium efflux, potassium influx. Net: Potassium ions enter the cell, in exchange for hydrogen ions leaving.
This requires a H+ conc gradient. (more H+ in cell than in blood)
Describe how acidosis-induced hyperkalaemia affects potassium levels in the body
pH falls, greater H+ conc outside cells.
K+ uptake by cells is reduced, so potassium accumulates in extracellular fluid in blood. K+ is responsible for membrane potentials and muscle functions, as well as skeletal muscle and cardiac pacemaker cells.
Symptoms include arrhythmia, muscle weakness
Describe alkalosis-induced vasoconstriction
Carbon dioxide (as H+) acts as a vasodilator, relaxing smooth muscle and increasing blood flow.
In alkalosis, reductions in PaCO2 and H+ (increase in pH) induce vasoconstriction of cerebral arteries, less blood flow to brain.
Symptoms - Headache, light-headedness, seizures then unconsciousness
