Resp

Question 1

V/Q at apex of lung vs. base of lung; V/Q of 0 vs. V/Q of infinity

Answer 1

V/Q is high at apex of lung (well ventilated, poorly perfused)

V/Q is low at base of lung (poorly ventilated, well perfused)

Thus V/Q of 0 indicates airway obstruction; V/Q of infinity indicates bloodflow obstruction

Question 2

Causes of hypoxemia with normal Aa gradient

Answer 2

Aa = 5-15

• High altitude
• Hypoventilation (e.g. opioid use, obesity hypoventilation syndrome, neuromusc disorders)

Question 3

Causes of hypoxemia with high Aa gradient (> 15)

Answer 3

• V/Q mismatch (airway obstruction causing shunting, or blood flow obstrxn increasing dead space)
• Diffusion limitation (e.g. alveolar wall thickening, fibrosis)
• R to L shunt (cyanotic congenital heart defect)

Question 4

Anion gap equation

Answer 4

Na - Cl - HCO3

normal = 10-14

Question 5

Stages of salicylate toxicity and acid/base imbalance

Answer 5

1: < 15 min (resp alkalosis) - ingestion of aspirin stimulates resp drive, causing you to blow off CO2
2: 3-5 hrs (resp alkalosis and metabolic acidosis) - acid (aspirin) dissociates, so now you also have a met acidosis. pH will start to normalize
3: mixed acidosis - GABA increases, slowing everything down. Decreased resp rate –> CO2 retention –> resp acidosis and metabolic acidosis from the aspirin

Question 6

Causes of metabolic gap acidosis

Answer 6

MUDPILES:
Methanol (formic acid)
Uremia
DKA/starvation
Propylene glycol
INH/Iron tablets
Lactic acidosis
Ethylene glycol (oxalic acid)
Salicylates (late - when aspirin dissociates into an acid)

Question 7

Causes of metabolic non-gap acidosis

Answer 7

HARDASS
Hyperalimentation
Addison disease
RTA
Diarrhea, Acetazolamide (decrease bicarb)
Spironolactone
Saline infusion

Question 8

Causes of respiratory alkalosis

Answer 8

"I start to hyperventilate if i HAS To Pee":
High altitude
Anxiety/panic attack
Salicylates (first 15 min)
Tumor
Pulmonary embolism

Question 9

Causes of metabolic alkalosis

Answer 9

Loop diuretics
Vomiting (decreased K+)
Antacid use (decreased H+)
Hyperaldosteronism (decreased H+ and K+)

Question 10

Causes of respiratory acidosis

Answer 10

Airway obstrxn
Acute or chronic lung disease (if chronic: metabolic compensation -> high bicarb)
Opioids, sedatives (normal bicarb bc acute)
Weakening of resp muscles

Question 11

O2-induced hypercapnia in COPD

Answer 11

COPD pts have poor ventilation, so pulm vasculature constricts and shunts blood to more well-ventilated regions. Giving supplemental O2 gives ventilated regions more O2 and reverses pulmonary vasocontrxn. This will increase dead space and decrease total alveolar ventilation

Question 12

Type I and II pneumocytes, collapsing P equation

Answer 12

• Type I: 97% of alveolar surfaces; line alveoli. squamous, small, thin for gas xchng
• Type II: secrete surfactant from lamellar bodies; decrease surface tension, prevent alv collapse, reduce lung recoil, increase compliance. cuboidal, clustered. Proliferate during lung dmg/give rise to type I and other type II cells (stem cells)
• collapsing P = 2(surface tension)/radius