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Pulmonary 9.5.12
gas Exchange, CXR, acid base
| Question | Answer |
|---|---|
| What 2 forms is oxygen in in the blood? | dissolved:responsible for PO2 bound to Hb: majority of O2 in blood |
| What does oxygen saturation express? | shows how many of all heme groups have bound O2 |
| In what state must iron be in to bind 02 and what enzyme does the body use to accomplish this? | must be in ferrous Fe2+, 3+ converted to 2+ by methomoglobin reductase |
| What is Hb with Fe3+? | methemoglobin |
| What is the mechanism of methemoglobinemia and what drugs can cause it? | nitrates and lido can overwhelm methemoglobin reductase making more fe3+ Hb |
| What types of Sx makes you suspect methemoglobinemia? | cyanosis, choclate brown blood, SaO2 by oximetry=85%. SaO2 by ABg is normal, PO2 is normal |
| How is a dx of methemoglobinemia made? | see methemoglobin % on ABG |
| What is PaO2 normal? | dissolved O2 in blood, 100 mm Hg |
| What is SaO2? normal? | % of hemes bound. normal =97.5%. |
| On what does the O2 dissolved in blood depend? | soulbility coefficient, alpha.0.003 mL O2/dL/mm Hg |
| How much O2 is carried by Hb? | 1.34mmO2/g Hb |
| How is total O2 concentration calculateD? | CaO2=[1.39xHgbxSaO2]+[0.003xPaO2] |
| What has the largest impact on the amount of O2 that can be carried? | Hemoglobin levels. Decreased Hb = decreased CaO2 |
| What is the mechanism of CO poisoning? | binds Hb and displaces O2. also causes bound O2 o bind more sticky |
| What are the Sx of CO poisoning? | HA. nausea, confusion,NOT SOB |
| How is the dx of CO poisoning made? | normal PO2, low Sa)2 (only with co-oximetric of arterial blood), finger is normal |
| What is the normal, smoker and posion concentrations of CO? | norm=3%, smoker =10%, posion=25% |
| How do you tx methemoglobinemia? | methylene blue |
| How do you treat CO poisoning? | 100% O2, hyperbaric O2 |
| What is the meaning of a right shift to the Oxygen dissociation curve> | O2 affinity for Hb is reduced, more unbound for O2 in capalaries |
| What is the meaning of a left shift to the oxygen dissociation curve? | O2 affinity for Hb is increased, less O2 unloading in capalaries |
| What causes a right shift to the oxygen dissociation curve? | acidosis, fever, increased pCO2, increased DPG |
| What causes a left shift to the oxygen dissociation curve? | alkalosis, low CO2, hypothermia, decreased DPG, CO poisoning |
| What is DPG and how is it increased an decreased? | helps load and unload O2, increased in high altitude and chronic hypoxia. decreased in store RBC |
| What are the 3 ways CO2 is transported the blood? | 1.dissolved (10%) 2. bicarbonate (60%) 3. carbamino acid (30%) |
| What is the chemical equalibrium of CO2 in the blood? What enzyme is key? | CO2+H2)<---->H2CO3<----> H+ HCO3-. 1st step catalyzed by carbonic anhydrase |
| How does the RBC act as a CO2 transporter? | dissolved CO2 enters RBC and binds to Hb, other is converted to caronic acid and bicarb which is exchanged on the outside for Cl- |
| What is the process of CO2 and bicarb release in the lungs? | dissovled CO2 exhaled, bicarb is pumped into RBC via Cl- where its bound to Hb and then exhaled |
| What is the RBC chloride shift? | maintians electrical neutrality by exchanging Cl- for HCO3- |
| What determines how well Hb binds CO2? | amount O2 unloads in tissues increased CO2 loading |
| What is the affect on oxygen saturation on the carbondioxide dissociation curve? | shift the curve upward |
| What is the arterial veous diff for O2? | 60mmHg |
| What is the arterial venous diff for CO2? | 5mmHg |
| How do O2 and CO2 move intpo/out of cappilaries? | only by diffusion. so O2 is lower the further away from capillary |
| What is myoglobin? what is whabdomyolyisis? | reserve of O2 in muscle, seen destroyed in muscle injury called rhabdomylysis which can damage kidney |
| What is the effect of exercise on the O2 dissociation curve? | shift to right, O2 is distributied easier |
| What are 3 means of hypoxia? | 1. low arterial )2 2. reduced blood O2 carrying capacity 3. reduced tissue BF |
| What is histotoxic hypoxia? | cells can't use )2 due to malfunction orf organells like mitochondria |
| What is the mechanism of cyanide poisoning? | prevents usage of O2 by cytochrome oxidase |
| What is the presentation of Cyanide poisoning? | HA, confusion, tachycardia |
| How is the dx of cyanide poisoning made? | bright red blood, high blood acetate, pink skin |
| How is cyanide poising treated? | sodium sulfate + hydroxycobalamine |
| What tissues survive longest and least without oxygen? | brain=3 min kidney/liver=10-15 skeltal=60min smm=24-72hr |
| Can you asccess the aorta at the aortic knob? Why not? | no. because see it medially and laterally in different planes can't assess size might appear falsely dilated |
| What does dilation of the azygous arch show? | ahows pressure in RH |
| What does a subcarinal mass do to the azygous esophageal recess? | displaces AE recess to right |
| What are the 5 main thing on the DDX for an airspace pattern? | blood, pus, water, protein, cells |
| What is a silhouette sign? | objects of same density are additive with e/o. R middle pleural effusion can block right Heart border |
| What is the spine sign? | spine is supposed to get darker moving superior to inferior |
| What is the normal blood pH? | 7.35-7.45 |
| What is the affect on pH with increasing H2CO3 or increasing HCO3-? | increased H2CO3=decreased pH, increased HCO3-=increased pH |
| What is the normal [HCO3]? | 24 |
| What is the normal [PaCO2]? | 40 |
| What is the lungs role in pH maintenance? | minute to minute pH controle b/v Va determine PaCO2, Ve=RRx(Va+Vd) |
| What does respiratory hyperventilation cause? | hypocapnea( PaCO2<35) |
| What does respiratory hypoventialation lead to? | hypercapnea (PaCO2>45) |
| How does the kidney contribute to pH control? | retain or release HCO3 |
| What is a simple acid base disturbance vs a complex one? | simple is compensated, complex isnt |
| Does a compensated patient ever get to normal pH? | no |
| What are the signs of respiratory acidosis? | increased pCO2, fix:renal retention of bicarb (increased HCO3), pH >7.4 |
| What are the signs of respiratory alkalosis? | decreased pCO2, pH>7.4, fix: increased renal excertion (decreased bicarb) |
| What are the signs of metabolic acidosis? | decreased HCO3,fix: incr. Ve, decreased PCO2. pH<7.4 |
| What are the signs of metabolic alkalosis? | increased HCO3, pH >7.4. fix:decrease Ve, increase PCO2 |
| What is the compensation of acute phase respiratory acidosis? | 10mmincrease PCO2=1mmHCO3 increase |
| What is the compensation ruile for chronic respiratory acidosis? | 10mm Hb incr PCO2= incr HCO3 3.5 mm rq |
| What type of acid base disruption do CNS depression, neuromuscular junction, obstructive lung disease, obesity and hyperthyoidism cause? | respiratory acidosis |
| What is the compensation rule for acute respiratory alkalosis? | 10 mm decr PCO2=HCO3 decr 5 m,eq |
| What type of acid base disturbance does axiety, pain, sepsis, CNS stim, pregnancy, chronic liver disease, hyperthyroidism? | respiratory alkalosis |
| What is the acid nase disturbance with an increased anion gap? | metabolic acidosis |
| How is the anion gap calculated? What is normal? | Na-(Cl+HCO3), 12+/- 2 |
| What is the compensation rule for metabolic acidosis? | last 2 digits of pH should equal pCO2 if com[pensated |
| What type of acid base disturbance is caused by ketoacidosis, lactic acidosis, uremia, methonoly and etylene glycol overdose as well as aspirin OD? | anion gap metabolic acidosis |
| What acid base disturbance is caused by diarrhea, renal tubular acidosis? | non anion gap metabolic acidosis |
| What is the normal osmolar gap and what does it help to characterize? | 10. helps characterize anion gap acidoses. increased gap=methanol or etgly posioning |
| What is the compensation rule for a metabolic alkalosis? | incr 1 HCO3=incr 0.6 mm PCO2 |
| What type of acid base disturbance is caused by vomit, nasogastric suction, diuretics? | cholride responsive metabolic alkalosis |
| What type of acid base disturbance is caused by hyperaldosteronism, Cushing syndrome, corticosteroid, Bartter's syndrome? | chloride undresponsive metabolic alkalosis |
| What does a base excess >+2 indicate? | metabolic alkalosis |
| What does a base excess <-2 indicate? | metabolic acidosis |
| How do you calculate the A-aPO2 gradient? what is normal | A-aPO2=[150-(5/4) xPCO2))-PaO2. norm =4+age/4 |
Created by:
tjs2123
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