Respiratory Physiology, Part II
Anesthesia, Chapter 57
1. In normal lungs total (physiologic) dead space ventilation includes:
- Anatomic dead space
- The volume of gas that ventilates zone 1 alveoli
- The volume of gas that ventilates all unperfused alveoli
- Approximately 1/3 of each breath
- All of the above
2. Each of the following is true of anatomic dead space EXCEPT:
- Anatomic dead space varies with lung size and is normally approximately 2 ml/kg of body weight
- Is roughly equal to total dead space in the supine patient
- Is a smaller volume than total dead space in the supine patient
- Is not increased with acute pulmonary embolism
- Is not increased with destruction of alveolar septa
3. Calculate the VD/VT ratio (physiologic dead space ventilation) based on the following data: PaCO2 45 mmHg, mixed expired CO2 tension 30 mmHg:
4. You're working in the SICU. One of your patients is a 42 year old male status-post right hemicolectomy for and drainage of an appendiceal abscess. He is 2 days post-op and appears to be severely septic. He has been recently intubated and had a PA catheter placed shortly thereafter. You are attempting to maximize oxygen delivery at the cellular level. The patient has a hemoglobin of 12.0. His initial cardiac output is 5 L/min. His PvO2 is 40 torr. PaO2 is 180. You give the patient a bolus of 1000 cc of Hespan. Repeat cardiac outputs show C.O.= 7 L/min. PvO2 is now 35 torr. Hgb is unchanged. PaO2 has dropped to 60. Would it be correct to infer that you are accomplishing the goal of improving cellar O2 delivery?
5. List the following values:
- P50 of hemoglobin corresponds to an oxygen partial pressure of
- PaO2 of 60 corresponds to roughly % saturation
- Normal mixed venous oxygen partial pressure is
- Normal mixed venous oxygen saturation is
6. List at least 6 factors that could contribute to a "left shift" in the oxy-hemoglobin dissociation curve. What happens to O2 unloading in the periphery when such a shift occurs?
7. List at least 4 factors that could contribute to a "right shift" in the oxy-hemoglobin dissociation curve. What happens to O2 affinity when such a shift occurs?
8. You are called to see a patient on 4C whom you recently intubated without incident. The primary service is concerned because the patient's O2 sats and PaO2 have dropped from 99-100% in the first few hours after intubation to 84% currently. This change occurred rather abruptly (over less than 1 hour), and seems to have been temporally related to sitting the sedated and paralyzed patient up in bed and bathing him. Increasing the patient's FIO2 produced virtually no change in PaO2. Suctioning also had no effect. CXR immediately after intubation showed the endotracheal tube in good position. Describe the initial steps in your evaluation and management of this patient. What do you suspect may have happened?
9. Which of the following is the most sensitive indicator of changes in cardiac output?
10. It is one week later and the patient in #4 has developed full-blown ARDS. You are struggling to ventilate the patient adequately to maintain his PaCO2 at an acceptable level. He has been on hyperal since placement of his PA catheter. Mechanical ventilation appears to be optimal given the limitations of his pathology. He no longer shows signs of active sepsis. Can you suggest additional changes that may improve his PaCO2 levels?
11. The approximate values of carbonic acid, bicarb, and carbamino-hemoglobin relative to the total CO2 transported in the blood are (K-question):
- H2CO3 = 7%
- HCO3 = 80%
- HbCO2 = 13%
- HCO3 = 87%
12. The shift of the CO2-hemoglobin dissociation curve which occurs in response to changes in PaO2 is known as the
- Bohr effect
- Fick principle
- Haldane effect
- Law of Laplace
- Le Chatelier principle
13. The dependence of the oxy-hemoglobin dissociation curve on changes in PaCO2 and pH is known as the:
- Bohr effect
- Fick principle
- Haldane effect
- Law of Laplace
- Le Chatelier principle
14. You are (still) PAR dog. A patient with a history of smoking, obesity, pulmonary hypertension, and sleep apnea arrives intubated after a 4 hour laparoscopic cholecystectomy. Shortly after arrival he is responsive to voice and follows some simple commands. NIF is -35. Tidal volume is 10 ml/kg. He can sustain a head lift for greater than 5 seconds. He has been on T-piece since arrival, with sats of 98-100% on 40% FIO2. You extubate the patient after suctioning him. His initial inspirations after extubation are stridorous and suddenly absent. The patient appears to be making strong respiratory efforts without moving any air. You apply positive pressure with a mask and ambu bag and after a few (excruciatingly long) seconds, he begins to ventilate adequately without assistance. Over the course of the next hour, his O2 sats slowly decline despite increases in his FIO2. Chest x-ray shows pulmonary edema, although the patient received only 1 liter of crystalloid intraoperatively and has no history of CHF. What may explain this?
15. You are anesthetizing a 72 year old 90 kg male with a history of long-standing hypertension. He has a 1.2 pack-century smoking history. Prior to admission, he was found unconscious and posturing on the kitchen floor, a half-empty (or half-full, for the optimists in the group)box of chocolate covered cherries by his head. CT scan revealed a sizable subdural bleed; the patient is undergoing craniotomy for evacuation of hematoma. As the case proceeds you give Decadron, mannitol, and hyperventilate the patient to an end tidal CO2 of 22. Prior to induction his O2 sats are 99-100% with preoxygenation. As the case proceeds, his sats drop substantially (80's). Increasing the FIO2 to 100% produces only a modest improvement in O2 sats. You also note what may be ST depression in the V lead you are monitoring. Discuss possible etiologies and how you would proceed.
16. List at least 6 possible causes of decreased FRC.
17. Endotracheal intubation reduces the size of the tracheal opening by:
- 10-15%
- 20-40%
- 30-50%
- 60-85%
- No change
18. Describe absorption atelectasis and suggest a case where it might be likely to occur.
19. All of the following surgical positions may decrease FRC EXCEPT:
- Lithotomy
- Kidney
- Steep Trendelenburg
- Supine
- Prone
20. Reduced mucociliary flow occurs with (K-question):
- Poor systemic hydration
- Low inspired humidity
- High FIO2
- Inflation of a low compliance endotracheal tube cuff
22. All of the following reduce hypoxic pulmonary vasoconstriction EXCEPT:
- Mitral stenosis
- Eisenminger's Syndrome
- Hypothermia
- Epinephrine
- Hypervolemia
23. List at least 4 potential causes of hypercapnia.
24. List at least 4 potential causes of hypocapnia.
25. You are anesthetizing a 30 week preemie now 10 weeks post partum for closure of a patent ductus arteriosus. You are excruciatingly familiar with the surgeon and anticipate that the procedure will take about three hours (though it will seem like weeks). How will you set your FIO2? How will you determine whether oxygenation is acceptable?
|
