Respiratory Acid-Base Balance Flashcards
what occurs when CO2 dissolves in an aqeous solution
CO2 is gaseous acid
what are pH buffers
that reversibly bind H+
blood pH is a measure of H+ that are not bound to buffers
what is the most important buffer system in the blood
interaction between CO2 and HCO3
there is a large amount of bicarb in the blood (24mM/L)
reactions are reversible so dependent on what’s on each side of equation
how does hemoglobin buffer pH
through imidazole groups
H+ ions will bind
what are intracellular buffers
when inside the cell, H+ buffered by amino acids, peptides, proteins and organic phosphates
how do intracellular buffers work
when intracellular H+ increases
what mechanisms ultimately correct the H+ load
lungs and kidneys
how can arterial pH be measured
by using henderson-hasselbalch equation
what is pH
negative Log of [H+]
what is the henderson-hasselbalch equation
when HCO3- is constant, increases in PCO2 cause decrease in pH
how does hypoventilation change PCO2 and alter pH
- PaCO2 increases
- leads to hypercapnia
- acidosis (lowers pH)
how does hyperventilation change PCO2 and alter pH
- PaCO2 decreases
- leads to hypocapnia
- alkalosis (increase in pH)
what is the davenport diagram
as PCO2 increases or decreases the changes in pH and bicarbonate concentration are predicted by the normal buffer line
how can H+ ions be eliminated
kindey is the only route
H+ excretion occurs in the PCT and is coupled to reabsorption of HCO3-
H+ secreted into the tubular lumen in exchange for Na+
Na+ and HCO3- are reabsorbed
what are primary problems in acid-base distribution (2)
- excessive accumulation or elimanation of CO2 (resp. abnormalities)
- excessive accumulation or elimination of fixed acids or buffer bases (metabolic abnormalities)
what is resp acidosis
- breathing is suppressed holding CO2 in body –> pH decreases, PCO2 increases, HCO3- no change
- the kidneys conserve HCO3- ions and eliminate H+ ions in acidic urine
- or lactate solution used in therapy converted to bicarbonate ions in the liver
what is metabolic acidosis
- metabolic acidosis HCO3- decreases because of excess presence of ketones, chloride or organic acid ions. pH decreases, PCO2 no change, HCO3- decreases
- body compensation: hyperactive breathing to blow off CO2 + kidneys conserve HCO3- and eliminate H+ ions in acidic urine
- lactate solution used converted to bicarbonate ions in liver
what are the causes of respiratory acidosis
- CNS depression
- Resp muscle paralysis/diaphragm paralysis, rib fractures
- obstructive lung diseases (emphysema)
- pulmonary edema
how does the body compensate resp acidosis
- carbonic acid excess caused by blood levels of CO2 above 45 mmHg
- kidneys eliminate hydrogen ion and retain bicarbonate ion
- kidney also generates new bicarbonate
what are the causes of metabolic acidosis
- bicarbonate deficit: blood conc. of HCO3- drops below 22mEq/L
- diabetic ketoacidosis
- severe diarrhea (loss of HCO3-)
- hypoaldosteronism
- acute renal failure (fail to excrete H+)
- accumulation of acids
how does the body compensate for metabolic acidosis
- increased ventilation
- renal excretion of hydrogen ions if possible
- K+ exchanges with excess H+ on ECF (H+ into cells, K+ out of cells)
what are the causes of resp alkalosis
carbonic acid deficit: pCO2 is <35mmHg (hypocapnia)
- hyperventilation
- high altitude (oxygen deficiency)
- hysterical
- anorexia nervosa
- early salicylate intoxication
how does the body compensate for resp alkalosis
- conditions that stimulate resp centre and wash out CO2 (hyperventilation)
- kidneys conserve+ ion
- excrete bicarbonate ion
what are the causes of metabolic alkalosis
blood conc. of HCO3 is > 26mEq/L
- severe vomiting = loss of stomach acid or heavy ingestion of antacids
- severe dehydration
- excess antacids & alkaline drugs
- hyperaldosteronism (endocrine disorders)
how does the body compensate metabolic alkalosis
- kidney excretes alkaline urine and retain H+
- respiratory compensation difficult (hypoventilation limited by hypoxia)
how do acid base disturbances affect distribution of K+
decrease in pH = increase in [K+] (hyperkalemia)
increase in pH = decrease in [K+] (hypokalemia)
what does hypokalemia lead to
increase in H+ elimination
what does Cl- depletion occur
can maintain metabolic alkalosis (ex. after vomiting has stopped) because of absence of Cl-, kidney must reabsorb HCO3- with Na+ (electroneutrality)
