Sill's 7th edition Self-Study Questions (Chapter 3 Blood Gas Sampling, Analysis, Monitoring, and Interpretation)

12. Interpret the following arterial blood gas drawn from a patient who is breathing 60% O2: pH, 7.18; PaCO2, 50 mmHg; PaO2, 72 mmHg; bicarbonate, 18 mEq/L; and base excess, −10 mEq/L; SaO2, 94%. 1. Uncorrected hypoxemia 2. Corrected hypoxemia 3. Uncorrected respiratory acidosis 4. Uncorrected metabolic acidosis 5. Combined metabolic and respiratory acidosis A. 1 and 5 only B. 2 and 5 only C. 2 and 3 only D. 2 and 4 only

The correct answer is: A A PaO2 level of less than 80 torr is uncorrected hypoxemia. A combined metabolic and respiratory acidosis is indicated by the increased PaCO2 value coupled with decreased bicarbonate level and decreased base excess found with an acidotic pH. (Review Tables 3-3 and 3-8.)

29. Interpret the following arterial blood gas drawn when the patient was breathing 30% oxygen: pH, 7.44; PaCO2, 25mmHg; PaO2, 85mmHg; HCO3 −, 17mEq/L; and BE, −7mEq/L; SaO2, 91%. 1. Corrected hypoxemia 2. Uncorrected hypoxemia 3. Compensated respiratory alkalosis 4. Uncompensated respiratory alkalosis 5. Combined metabolic and respiratory acidosis A. 1 and 3 only B. 1 and 4 only C. 2 and 3 only D. 2 and 5 only

The correct answer is: A A PaO2 value of less than 85 mmHg while breathing supplemental oxygen is corrected hypoxemia. A compensated respiratory alkalosis is indicated by the decreased PaCO2 value coupled with a decreased bicarbonate level and decreased base excess found with a normal pH. (Review Tables 3-3 and 3-8.)

33. A neonatal patient is receiving 40% oxygen in an oxyhood. The following capillary blood gas results have just been received: pH, 7.37; PCO2, 45 mmHg; PO2, 60 mmHg; HCO3 −, 22 mEq/L; and BE, −2 mEq/L; SO2, 91%. Which of the blood gas values can be reliably used clinically? 1. pH, 7.37 2. PCO2, 45 mmHg 3. PO2, 60 mmHg 4. SO2, 91% A. 1 and 2 only B. 3 and 4 only C. 1, 2, and 3 only D. 1, 2, 3, 4

The correct answer is: A An arterialized capillary blood gas sample will provide pH and carbon dioxide values that are close to those found in an arterial sample. Oxygenation cannot be reliably evaluated through a capillary sample.

19. A respiratory therapist is working with a postanesthesia patient who is on a PtcCO2 monitor. The correlation factor between the PaCO2 and the PtcCO2 is 1.4. The patient's previous PtcCO2 level was 63 torr. The nurse has called you because it is now 75 torr. The patient's approximate PaCO2 value would be calculated as: A. 54 torr B. 63 torr C. 75 torr D. 105 torr

The correct answer is: A The patient's approximate PaCO2 value of 54 torr is found by dividing the PtcCO2 value of 63 torr by the correlation factor of 1.4. (See an example calculation in the text.)

24. A premature neonate breathing room air has a PtcCO2 electrode placed on her right thigh and a PtCO2 electrode placed on her left thigh. Both have been showing stable readings over the past hour. After the patient was moved about for nursing care it is noticed that the PtCO2 electrode value has increased. The PtcCO2 electrode value is unchanged. What could explain this? A. The PtCO2 electrode has pulled loose from the skin. B. The inspired oxygen percentage has been decreased. C. The patient's pulmonary condition has improved. D. The patient is hyperventilating

The correct answer is: A The sudden increase in the PtCO2 value can be explained by the electrode being pulled loose from the skin, allowing room air to contact it. If the patient's oxygen percentage was decreased (less than 21% in room air), there would be a decrease in the PtCO2 value. If the patient's pulmonary condition suddenly improved, her PtcCO2 value would probably also have changed. If the patient was hyperventilating to raise her oxygen value, her carbon dioxide value would have decreased.

2. A patient is brought into the Emergency Department after being rescued from a house fire. She is unconscious and has facial burns. The physician believes that she is suffering from smoke inhalation. What should be recommended as the best way to evaluate her? A. ABGs analyzed through a CO oximeter B. Standard pulse oximetry C. ABGs analyzed through a standard blood gas analyzer D. Continuous PtcO2 monitor

The correct answer is: A When there is the possibility that a patient has carbon monoxide poisoning, blood gas analysis should be performed through a CO oximeter or hemoximeter to check for COHb. The other three choices cannot measure COHb level. Additionally, pulse oximetry and PtCO2 monitoring do not give CO2 or pH values.

10. Interpret the following arterial blood gas drawn from a patient who is breathing 35% O2: pH, 7.29; PaCO2, 37 mmHg; PaO2, 86 mmHg; bicarbonate, 17 mEq/L; and base excess, −8 mEq/L; SaO2, 90%. 1. Corrected hypoxemia 2. Uncorrected hypoxemia 3. Compensated metabolic acidosis 4. Uncompensated metabolic acidosis 5. Compensated respiratory acidosis A. 2 and 4 only B. 1 and 4 only C. 2 and 5 only D. 1 and 3 only

The correct answer is: B A PaO2 value greater than 80 torr with supplemental O2 is corrected hypoxemia. An uncompensated metabolic acidosis is indicated by the normal PaCO2 value coupled with decreased bicarbonate concentration and decreased base excess found with an acidotic pH. (Review Tables 3-3 and 3-8.)

7. A 50-year-old patient has a PaO2 value of 72 torr when breathing room air. How should this be interpreted? A. Normal for a person of that age B. Mild hypoxemia C. Moderate hypoxemia D. Severe hypoxemia

The correct answer is: B A PaO2 value in the 60 to 79 torr range indicates mild hypoxemia. Review Table 3-3 for the categories of hypoxemia.

30. Which of the following clinical values indicates that a patient's tissues are hypoxic? A. PaO2 of 55 torr B. PvO2 of 25 torr C. SvO2 of 80% D. SaO2 of 88%

The correct answer is: B A PvO2 value of 25 torr is quite low. A PvO2 value of 40 torr is normal, and a value below 30 torr usually indicates tissue hypoxia. An SvO2 value of 80% is above the normal value of 75% and indicates above-normal tissue oxygenation. Although a PaO2 value of 55 torr and an SaO2 value of 88% are below normal, they do not necessarily indicate tissue hypoxia. Many patients with chronic lung disease live acceptable lives with values in this range. (Review Table 3-11.)

1. Before drawing a blood gas sample from the radial artery, which test should be performed? A. Allen test B. Modified Allen test C. Blood pressure measurement D. Nail bed blanching

The correct answer is: B A modified Allen test is used to determine whether adequate perfusion exists through the ulnar artery in case the radial artery should become occluded. This would ensure that the hand is still well perfused. The Allen test is used to determine adequate perfusion through the radial artery. Adequate arm blood pressure does not ensure adequate perfusion of the hand, should the radial artery become blocked. Pressing on the nail bed to make it blanch and then releasing the pressure to check on reperfusion is only a general indicator of peripheral perfusion. It does not confirm adequate circulation through either the radial or the ulnar arteries.

31. A spontaneously breathing neonate is in an incubator. The patient is being monitored with a transcutaneous carbon dioxide electrode on her right upper chest. An hour ago, the patient's carbon dioxide value was 45 mmHg, and now it is 5 mmHg. The nurse tells you there has been no change in the neonate's condition. What is the most likely explanation for this difference? A. The patient has a patent ductus arteriosus. B. Air has leaked under the electrode. C. The temperature inside the incubator has been increased. D. The patient's cardiac output and lung condition have improved.

The correct answer is: B Because the PtcCO2 has rapidly changed from the normal range of 45 mmHg to the current very low value of 5 mmHg, the only possible explanation has to be a leak of room air under the electrode. Check the adhesive ring. If loose, seal the ring on the skin and look for a rise in the carbon dioxide level. If the patient had a patent ductus arteriosus, a decrease in the PtcO2 value would be found over the patient's left chest area and body. An increased temperature inside the incubator would have no effect on the PtcCO2 value. Even if the patient's cardiopulmonary condition had improved, a neonate would not spontaneously hyperventilate to a PtcCO2 value of 5 mmHg.

8. An acute rise in PaCO2 level from 40 to 50 mmHg would result in the following change in pH: A. Rise of 0.10 unit B. Fall of 0.05 unit C. Fall of 0.10 unit D. Rise of 0.05 unit

The correct answer is: B Shapiro and associates (1994) have stated that an acute rise in CO2 of 20 mmHg results in a drop in pH of 0.10 unit. So, an acute rise in CO2 of 10 mmHg would result in a drop in pH of 0.05 unit.

34. The results of a set of arterial blood gases and central venous blood gases have been received from a patient in the Intensive Care Unit. The results show that the PcvCO2 is 58 torr and the PaCO2 is 43 torr. How should these results be interpreted? A. Disregard because of a preanalytic error with the PcvCO2. B. The patient has low cardiac output. C. The patient is being hyperventilated. D. The patient is in ventilatory failure

The correct answer is: B The approximate difference between the arterial and the central venous carbon dioxide levels should be about 6 torr. This patient's larger than expected difference could be the result of low cardiac output and decreased peripheral circulation. As the blood passes through the body more slowly, there is more time for carbon dioxide to accumulate, resulting in the high PcvCO2. There is no reason to believe that there was a preanalytic error with either blood gas sample. Because the patient's PaCO2 is in the normal range of 43 torr, he or she is not being hyperventilated or in ventilator failure.

17. An adult patient has Guillain-Barré syndrome and pneumonia. The patient has just been placed on 35% O2 by mask. The physician asks for your suggestion on the best way to evaluate the patient's overall ability to breathe. What should be recommended? A. Doing a full set of pulmonary function tests B. Drawing an arterial blood sample for analysis C. Performing pulse oximetry D. Performing a force vital capacity measurement

The correct answer is: B The results of an ABG measurement inform you of the patient's oxygenation status and PaCO2 level. Pulse oximetry gives information only on oxygenation status. Pulmonary function tests do not give any information on the patient's PaO2 and PaCO2 levels. Additionally, a full set of pulmonary function tests can be very tiring for the patient.

15. Blood gas analyzer calibration values are considered to be in control if they are within: A. 1 SD of the norm B. 2 SDs of the norm C. 3 SDs of the norm D. 4 SDs of the norm

The correct answer is: B Two SDs are considered "in control" with a blood gas analyzer. (See Fig. 3-8.)

13. Interpret the following arterial blood gas drawn from a patient who is breathing 24% O2: pH, 7.45; PaCO2, 22 torr; PaO2, 57 torr; bicarbonate, 16 mEq/L; and base excess, −6 mEq/L; SaO2, 91%. 1. Corrected hypoxemia 2. Uncorrected hypoxemia 3. Compensated respiratory alkalosis 4. Uncompensated respiratory alkalosis 5. Combined metabolic and respiratory acidosis A. 1 and 3 only B. 1 and 4 only C. 2 and 3 only D. 2 and 5 only

The correct answer is: C A PaO2 value of less than 80 torr while breathing supplemental oxygen is uncorrected hypoxemia. A compensated respiratory alkalosis is indicated by the decreased PaCO2 value coupled with decreased bicarbonate concentration and decreased base excess found with a normal pH. (Review Tables 3-3 and 3-8.)

14. Which of the following best indicates that a patient's tissues are adequately oxygenated? A. PaO2, 85 mmHg B. PvO2, 30 mmHg C. SvO2, 75% D. SaO2, 90%

The correct answer is: C An SvO2 value of 75% is normal and correlates with normal tissue oxygenation. A PvO2 value of 30 mmHg indicates tissue hypoxia. Normal ABG values do not necessarily correspond to normal tissue oxygenation values. (See Table 3-11.)

11. Interpret the following arterial blood gas drawn from a patient who is breathing 21% O2: pH, 7.57; PaCO2, 20 torr; PaO2, 117 torr; bicarbonate, 24 mEq/L; and base excess, +1 mEq/L; SaO2, 98%. 1. Normal oxygenation 2. Excessively corrected hypoxemia 3. Uncompensated respiratory alkalosis 4. Uncompensated metabolic acidosis 5. Compensated respiratory and metabolic alkalosis A. 2 and 3 only B. 2 and 4 only C. 1 and 3 only D. 1 and 4 only

The correct answer is: C Normal oxygenation is indicated because the patient's PaO2 level is elevated as a result of hyperventilation (PaCO2 value of 20 torr). An uncompensated respiratory alkalosis is indicated by the low PaCO2 value coupled with normal bicarbonate concentration and normal base excess found with an alkalotic pH. (Review Tables 3-2 and 3-8.)

32. A 17-year-old patient is receiving mechanical ventilation because of apnea resulting from a drug overdose. While the patient is breathing 25% oxygen, the following ABG values are analyzed: PaO2 of 155 torr SaO2 of 100 % pH of 7.42 PaCO2 of 41 torr BE of + 2 mEQ/L What action should now be taken? A. Reduce the patient to 21% oxygen. B. Maintain the present settings. C. Recheck the blood gas analyzer. D. Hyperventilate the patient.

The correct answer is: C Recheck the blood gas analyzer for a problem with the PO2 electrode. A calculation of the patient's PAO2 level shows that the maximum PaO2 value the patient can have is 127 torr. Do not make a change to the patient's inspired oxygen percentage until there is an accurate PaO2 value. Although there is no reason exists to doubt the pH and PaCO2 values, do not make any changes to the ventilator setting until there is correct PaO2 value. There is no indication to hyperventilate this drug-overdose patient. Do not confuse this case with temporary hyperventilation of a patient with a head injury and increased intracranial pressure.

18. A respiratory therapist is called to evaluate a patient who is using a pulse oximeter. Upon entering the room, it is noticed that the patient is an African American woman with an oximeter probe on her right earlobe. The monitor shows a weak pulse signal and a fluctuating SpO2 value. Which of the following should be done in an attempt to correct the problem? 1. Try monitoring from a fingertip. 2. Switch to a bridge of the nose sensor. 3. Cover the probe with an opaque wrap. 4. Switch the probe to the left earlobe. A. 2 only B. 3 only C. 1 and 3 only D. 2 and 4 only

The correct answer is: C Some pulse oximeters obtain inaccurate readings through the skin of darkly pigmented patients. Blocking outside light with an opaque wrap or moving the sensor to a lightly pigmented area such as a fingertip (without nail polish) often results in accurate readings. (See Table 3-13.)

6. Which of the following are safety guidelines for the protection of the respiratory therapist who is drawing an ABG sample? 1. Put a glove on the hand used to draw the sample. 2. Put a glove on the hand with which feels the pulse. 3. Put gloves on both hands. 4. Wear goggles and mask. A. 2 only B. 3 only C. 3 and 4 only D. 1 and 4 only

The correct answer is: C Standard Precautions necessitate that gloves be worn on both hands when blood may be contacted by either hand. Additionally, the eyes should be protected from possible blood splashes.

23. A 50-year-old male patient is being treated for a pulmonary embolism. He is receiving 50% O2 by mask. The results of a P(A-a)O2 study indicate that his alveolar-arterial difference is 205 torr. What is the best interpretation of this study? A. The results are not physiologically possible. B. It is within the normal range. C. The alveolar-arterial difference is increased. D. The patient's condition is improving

The correct answer is: C The P(A-a)O2 value should be 15 torr or less in a normal person because of good matching of ventilation and perfusion. Therefore this patient's alveolar- arterial difference is increased. Review the example calculations in this chapter.

3. A respiratory therapist is ordered to draw a blood sample from your patient's radial artery. Before drawing the sample, a circulation test is performed by having the patient make a fist while pressure is applied over his ulnar and radial arteries. The patient's hand is then opened, and pressure is released from the ulnar artery. His hand color returns within 15seconds. This would indicate that the patient's: A. Radial circulation is adequate B. Radial circulation is inadequate C. Ulnar circulation is adequate D. Ulnar circulation is inadequate

The correct answer is: C The described test and its results are of a positive modified Allen test. This positive result means that the patient has adequate ulnar circulation.

36. Because it is not possible to obtain an arterial blood gas sample on a newborn child, the physician orders blood gas analysis of an arterialized capillary blood sample. Which of the following should be selected as the preferred sampling site? A. Fingertip B. Earlobe C. Lateral area of the heel D. Toe tip

The correct answer is: C The lateral area of the heel is the preferred puncture site. (See Fig. 3-4.) A fingertip, toe tip, or earlobe could be used if the lateral heel puncture is unsuccessful.

21. Based on the listed conditions, what is the patient's P(A-a)O2 value? A. 41 mmHg B. 232 mmHg C. 243 mmHg D. 248 mmHg

The correct answer is: C The patient's P(A-a)O2 value (difference between alveolar pressure and arterial pressure of oxygen) can be calculated as follows: The patient's PAO2 = 303 mmHg The patient's PaO2 = − 60 mmHg/243 mmHg

A 35-year-old patient with pneumonia is receiving mechanical ventilation with PEEP. Calculate and interpret the patient's P(A-a)O2 level. The following conditions exist: 1. PB =750 mmHg; normal is 760 mmHg for sea level 2. PH2O =54 mmHg because your patient's temperature is 104° F/40° C; normal is 47 mmHg for a normal temperature 3. FIO2 =0.5 for 50% inspired oxygen; normal is 0.21 for room air 4. PaCO2 =36 mmHg 5. PaO2 =60 mmHg 6. Respiratory exchange ratio=0.8 PACO2 = [(PB − PH2O ) FIO2 ] − PaCO2/0.8 Based on the listed conditions, what is the patient's PAO2 value? A. 95 mmHg B. 101 mmHg C. 303 mmHg D. 312 mmHg

The correct answer is: C The patient's PAO2 value (pressure of alveolar oxygen) can be calculated as follows: PAO2 = ([PB − PH2O ] FIO2 ) − PaCO2/0.8 = ([750−54] 0.5) − 36/0.8 = ([696] 0.5) − 45 = (348) −45 = 303 mmHg

16. A 50-year-old patient with emphysema seems to be tiring 30 minutes into a weaning attempt on a Briggs adapter (T-piece). The best way to evaluate the patient's ventilatory status is by: A. Checking pH value B. Measuring a PtcCO2 value C. Checking PaCO2 value D. Measuring bedside vital capacity

The correct answer is: C The patient's PaCO2 value best correlates with ventilatory status and level of fatigue. The other tests are of value but give less direct evidence of the ability to breathe effectively.

4. A respiratory therapist working in the Intensive Care Unit notices that an arterial blood sample has been sitting out for 40 minutes. It was not put in ice water. The blood gas analysis could be affected in which of the following ways? 1. Increased PaO2 2. Increased PaCO2 3. Decreased PaO2 4. Decreased PaCO2 5. Increased pH 6. Decreased pH A. 1, 2, and 6 only B. 3, 4, and 5 only C. 2, 3, and 6 only D. 3, 4, and 6 only

The correct answer is: C When a blood sample is not quickly cooled in ice water, the living tissue will continue to consume O2 and produce CO2. The increased CO2 level will decrease the pH value

27. Interpret the following arterial blood gas drawn when the patient was breathing 45% oxygen: pH, 7.38; PaCO2, 59torr; PaO2, 64torr; HCO3 −, 39mEq/L; and BE, +12mEq/L; SaO2, 91%. 1. Corrected hypoxemia 2. Uncorrected hypoxemia 3. Metabolic alkalosis 4. Compensated respiratory acidosis 5. Metabolic acidosis A. 1 and 4 only B. 1 and 3 only C. 2 and 5 only D. 2 and 4 only

The correct answer is: D A PaO2 level of less than 80 mmHg while breathing supplemental oxygen is uncorrected hypoxemia. A compensated respiratory acidosis is indicated by the increased PaCO2 value coupled with an increased bicarbonate level and increased base excess found with a normal pH. (Review Tables 3-3 and 3-8.)

9. Interpret the following arterial blood gas drawn from a patient who is breathing 40% O2: pH, 7.37; PaCO2, 62 torr; PaO2, 54 torr; bicarbonate, 38 mEq/L; and base excess, +11mEq/L; SaO2, 87%. 1. Corrected hypoxemia 2. Uncorrected hypoxemia 3. Metabolic alkalosis 4. Uncompensated metabolic acidosis 5. Compensated respiratory acidosis A. 1 and 4 only B. 1 and 3 only C. 2 and 4 only D. 2 and 5 only

The correct answer is: D A PaO2 value of less than 80 torr while breathing supplemented oxygen is uncorrected hypoxemia. A compensated respiratory acidosis is indicated by the increased PaCO2 value coupled with an increased bicarbonate level and increased base excess found with a normal pH. (Review Tables 3-3 and 3-8.)

28. Interpret the following mixed venous blood gas drawn when the patient was breathing 40% oxygen: pH, 7.35; PvCO2, 46 mmHg; PvO2, 40 mmHg; SvO2, 75%. 1. Corrected hypoxemia 2. Uncorrected hypoxemia 3. Metabolic acidosis 4. Normal acid-base balance 5. Respiratory acidosis A. 2 and 3 only B. 1 and 5 only C. 2 and 5 only D. 1 and 4 only

The correct answer is: D A normal PvO2 value of 40 mmHg with supplemental oxygen indicates corrected hypoxemia. Normal acid- base balance is shown by the normal mixed venous carbon dioxide and pH. (Review Table 3-11.)

5. In which of these clinical situations should an arterial blood gas sample be taken and analyzed? 1. Check the PaO2 after a change in the inspired O2 concentration 2. Suspected Carbon Monoxide poisoning 3. Check the PaCO2 after a change in the minute volume 4. A patient has been admitted with a tension pneumothorax A. 1 and 2 only B. 1 and 3 only C. 2, 3, and 4 only D. 1, 2, 3, 4

The correct answer is: D All of the listed conditions would warrant a blood gas analysis because they all deal with significant oxygenation and/or CO2 removal issues.

26. A 45-year-old patient has been admitted to the Emergency Department after having smoke inhalation from a house fire. The patient is wearing a nonrebreathing mask set at 10L/min of oxygen. The most appropriate way to evaluate the patient's oxygenation status is by: A. Pulse oximetry with a standard unit B. Transcutaneous oxygen monitor C. ABG sample run through a blood gas analyzer D. ABG sample run through a CO-oximeter

The correct answer is: D The best way to assess the oxygenation status of a patient with carbon monoxide poisoning is to run an ABG sample through the CO oximeter. The CO oximeter is the only device that can accurately differentiate between carboxyhemoglobin and oxyhemoglobin (and other types of hemoglobin) and measure the amounts of each. Therefore it gives an accurate SaO2 value. The first-generation pulse oximeter device is unable to distinguish between carboxyhemoglobin and oxyhemoglobin. This provides a false high value for SaO2. The transcutaneous oxygen probe can be used to give an approximate tissue oxygen value. However, it is not the clinically accepted way to evaluate a patient with CO poisoning. Running an ABG sample through a standard blood gas analyzer results in measurements of oxygen and carbon dioxide concentrations and of pH. However, the SaO2 value is calculated from the PaO2 value. This can result in a falsely high value for the calculated SaO2 level if the patient is receiving supplemental oxygen and has an elevated PaO2 value (measured from the blood plasma).

22. How should the patient's P(A-a)O2 results be interpreted? A. Check for a blood gas analyzer error. B. Normal oxygenation and ventilation. C. Normal for a patient of this age. D. Larger than normal difference.

The correct answer is: D The normal P(A-a)O2 difference should be no more than 25 mmHg for a healthy person of this age. The patient's difference of 243 mmHg is far greater than normal for any patient. (See Fig. 3-21.) There is no indication that the blood gas analyzer needs recalibration. This equation is not used to evaluate ventilation.

25. After a modified Allen test is performed on a patient's right wrist, it takes 25 seconds for the patient's hand to regain its color. What should be done now? A. Perform an Allen test on the right wrist. B. Draw an arterial blood sample on the right wrist. C. Draw an arterial blood sample on the left wrist. D. Perform a modified Allen test on the patient's left wrist

The correct answer is: D The results of the modified Allen test performed on the patient's right wrist are abnormal. It took 25 seconds for the return of adequate circulation through the ulnar artery. No arterial blood sample should be taken from the right radial artery because of poor collateral circulation through the ulnar artery (see Fig. 3-2). Check the circulation on the patient's left wrist by doing a modified Allen test on it. Draw from the left radial artery if the test result is normal (less than 15 seconds for the return of circulation). The Allen test is a test of circulation through the radial artery, whereas the modified Allen test is a test of circulation through the ulnar artery

35. An adult patient in Denver, Colorado, is receiving 50% oxygen through an air entrainment mask. The patient's arterial blood gas values are pH, 7.41; PaCO2, 38 mmHg; PaO2, 85 mmHg; bicarbonate, 25 mEq/L; and base excess, +1 mEq/L; SaO2, 96%. The local PB is 745 mmHg. The patient's P:F ratio would be calculated as which of the following? A. 0.05 B. 0.11 C. 0.76 D. 1.7

The correct answer is: D With the P:F ratio, the PaO2 of 85 mmHg is divided by the oxygen percentage as a whole number (or, in an alternate equation version, by the FIO2 as a decimal fraction of 0.50). So, the equation is set up as follows: PaO2/O2 %= 85/50 = 1.7