20 - Acid-Base Physiology

Question 1

pH range of important bodily fluids

Answer 1

gastric juice: ~1.5 - 3
saliva: ~6.5
blood: 7.35 - 7.45
urine: ~4.5 - 8

Question 2

pH for acidosis (acidemia) and alkalosis (alkalemia)

Answer 2

acidocis: blood pH under 7.35
alkalosis: blood pH above 7.45
we can only stay outside of this range for very short periods of time

Question 3

respiratory causes of acidosis

Answer 3

lungs cannot remove CO2 from the blood efficiently enough so CO2 and H2O equilibrium shifts right (to make H+ and HCO3-)

causes:
- lung damage (emphysema)
- loss of patency in airways (foreign body)
- chest wall damage (damage to muscles of respiration)

Question 4

what tells the brain to breathe?

Answer 4

CO2 levels, if CO2 can be removed without increasing O2 levels, the brain will believe you are breathing
(O2 contributes to the signalling as well, but not nearly as much)

Question 5

nonrespiratory/metabolic acidosis causes
(all except consumption/GI related causes)

Answer 5

anything other than CO2 causes
- anaerobic metabolism: lactic acid produced during anaerobic glycolisis (during excercize)
- kidney dysfunction: responsible for excreting H+, if dysfuntional pH will fall
- incomplete breakdown of fatty acids: uncontrolled diabetes mellitus and other forms of starvation lead to large increases in fatty acids
- normal metabolism: small contribution to acidosis

Question 6

nonrespiratory/metabolic causes of acidosis
(related to consumtion/GI)

Answer 6

• consumption of ethanol in large quantities: or more poisonous alcohols like methanol
• acidic fruits: small contribution
• diarrhea: lower reabsorption, can’t reabsorb as much bicarb to offset H+

Question 7

respiratory alkalosis

Answer 7

hyperventilation: excessive deep breathing causes low CO2 levels

Question 8

nonrespiratory/metabolic causes of alkalosis

Answer 8

• vomiting: loss of H+ from vomiting stomach contents
• ingestion of bicarbonate: consume some of blood pH, pH goes up
• constipation: excessive absorption of bicarbonate in GI

Question 9

how to correct changes in pH

Answer 9

breathe more: correct acidity
breathe less: correct alkalinity
renal: correct acidity by removing H+ and absorbing bicarbonate

Question 10

finding causes of acidosis or aklalosis

Answer 10

• determine acidosis (< 7.35) or alkalosis (> 7.45): check blood pH
• determine respiratory or metabolic: check blood CO2
  
  • if CO2 levels correspond to the pH change, cause is likely respiratory
• more evidence for non-respiratory: check blood bicarbonate
  
  • if bicarb levels correspond to the pH change, cause is likely metabolic