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Respiratory Physiology week 3


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What are the PVO2 and PVCO2 of mixed venous blood?
PVO2 = 40 mm Hg

PVCO2 = 46 mm Hg
why is emphysema an "obstructive disease"?
loss of elastic recoil leads to collapse of airways, which causes obstruction
what are the two reasons that expiration is impaired in COPD?
(1) loss of elastic recoil that normally drives air out of the lungs

(2) collapse and obstruction of airways and inc resistance to airflow
O-2 binding capacity of Hb definition
how many mL of O2 each gram of Hb can hold at 100% saturation

things that DON'T affect it: dec [Hb], change in PO2, left/right shift

things that do affect: CO poisoning
anion gap eqn
[Na+] - ([Cl-] + [HCO3-])
anion gap normal value
10-16 mEq/L
what happens in diabetes mellitus that leads to an inc anion gap?
Beta-hydroxybutyric acid and acetoacetic acid inc --> excess H+ buffered by HCO3- --> dec in measured anion HCO3 - --> replaced by unmeasured ketoanions
what happends in renal failure that leads to an inc anion gap?
metabolic acidosis, dec HCO3- concentration, and inc unmeasured anions such as sulfate and phosphate
what are three overall causes of metabolic acidosis?
(1) inability to excrete H+ (renal failure, renal tubular acidosis)

(2) fixed acid load
- lactic acidosis
- ketoacidosis
- ingestion of salicylate, NH4Cl (HCl), methanol, ethylene glycol

(3) HCO3- loss
- diarrhea
- CA inhibitors
what are the two major causes of metabolic alkalosis?
(1) H+ loss
- vomiting
- hyperaldosteronism
- diuretics

(2) HCO3- excess
- administration of HCO3-
list four causes of respiratory acidosis.
(1) inhibition of the medullary respiratory center

(2) disorders of the respiratory muscles

(3) upper airway obstruction

(4) disorders of gas exchange (e.g. COPD)
what are three causes of respiratory alkalosis?
(1) hypoxemia

(2) direct stimulation of the medullary respiratory center

(3) mechanical ventilation
what does an inc in blood [K+] do to NH3 synth?
inhibits NH3 synth
what happens to K+ secretion by distal tubules in metabolic alkalosis?
in alkalosis H+ leaves renal distal cells and K+ enters, thus inc intracellular K+ and increasing the driving force for K+ secretion

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