1. Unit 4.1: Supplemental Oxygen Therapy Case studies by Elizabeth Kelley Buzbee AAS, RRT-NPS, RCP

2. Case study #1  Mr. Hall is a 45 year old WM who presents in the ER with rapid shallow breathing. He was standing in his backyard when the chemical plant exploded and started to burn.  How do you want to assess this person?

3. Answer: 1.Do vital signs for s/s of respiratory distress 2.Check his state of consciousness 3.Check his work of breathing 4.Listen to breath sounds 5.Perform pulse oximetry but remember that it will not pick up HbC0 6.Do a co-oximetry reading

4. 1.vital signs : HR 140 respiratory rate: 33 bpm 2.He is anxious but understands your questions 3.He is retracting and has nasal flaring 4.His breath sounds show diffuse crackles in all lobes consistent with chemical pneumonitis 5.Sp02 is 88% 6.HbC0 is wnl What do you want to do with this patient?

5. answer  Start him on supplementary 02 to treat the s/s of hypoxemia

6.  What 02 device do you select?

7. Answer:  Without any history, it would be safe to start him on 1-2 lpm nasal cannula

8.  Before you place this patient on 2 lpm nasal cannula, to make sure the device is working correctly you do what?

9. Answer:  You look at the flow meter; is the flow indicator in the middle of the ball?  You feel the flow coming out of the device on the back of your hand  You look at the bubbles coming from the humidifier  You check the connections:  Between the wall connection and the flow meter  between the humidifier and flow meter.  Between the humidifier and the 02 line

10.  You put the nasal cannula in Mr. Hall’s nose and warn him about what?

11. Answer: 1.Fire hazards of 02 2.Calling you if he feels the 02 is disconnected or that he feels short of breath

12.  What is the approximate Fi02 of this device at this flow rate?

13. Answer:  Fi02 of nasal cannula can be estimated by adding 4% per each liter of flow to base line of 20%.  2 lpm = [2 x 4] + 20%  2 lpm = 28% Fi02

14.  If he starts breathing any faster, what might happen to this estimated Fi02?

15. Answer:  The Fi02 will drop as his respiratory rate rises and more air is entrained.

16.  How do you assess the effectiveness of this device?

17. Answer: 1.Redo vital signs 2.Redo pulse oximetry 3.Reassess him for increased work of breathing

18.  Is this patient at risk for 02 toxicity?

19. Answer:  Not at this flow rate

20.  Is this patient at risk for 02 induced hypoventilation?

21. Answer:  He have no history that indicated he has chronic hypoxemia nor that he breathes on a hypoxic drive, but at this flow rate, he is safe enough

22.  After 10 minute on 2 lpm nasal cannula, Mr. Hall still is breathing at a rate of 33 bpm.  His Sp02 is still 88% and his HR is still 130 bpm  He is still retracting and flaring on 2 lpm nasal cannula  What do you do?

23. Answer:  Increase his 02 from 2 lpm to 3 lpm

24.  How do you assess the effectiveness of 3 lpm nasal cannula?

25. Answer: 1.Repeat Sp02 2.Reassess the vital signs 3.Reassess the work of breathing

26.  You have increased Mr. Hall’s nasal cannula from 5 lpm to 6 lpm without any change in his appearance.  What do you suggest now?

27. Answer:  Do an arterial blood gas to make sure that he doesn’t need more than 02  From the blood gas, calculate the Fi02 he needs

28.  You increase the flow rate a few times and when you get to 6 lpm you switch to a simple mask.  Why?

29. Answer: 1.The flow rate at 6 lpm via the cannula may not be that comfortable 2.The mask holds the 02 in the reservoir so that the patient gets more 02 and less entrained air.

30.  What is the Fi02 of this device?

31. answer  30% - 60% at flow rates of 5-12 lpm

32.  The doctor looks at the Sp02 of 89% and orders him placed on 50% entrainment mask.  What is the total flow rate if the flow meter is set at 6 lpm?

33. Answer:  Based on the magic box at 50% there is 1.6 lpm air entrained per liter of 02 6 lpm 02 + [ 6 x 1.6] = 6 + 9.6 = 15.5 lpm is the total flow going to this patient

34.  If Mr. Hall’s Ve is 14 lpm, is this flow rate adequate for him?

35. Answer:  No, for a high flow system, he needs his Ve x [i+e] usual I:E breathing spontaneously is 1:1 or 1:1.5  So 14 x [1+1] = 28 lpm  He needs a total flow of 28 lpm  What can we do?

36. Answer:  Increase the flow meter from 6 lpm to 12 lpm to increase the total flow rate going to this patient

37.  You get an ABG on 12 lpm 50% entrainment mask and the Pa02 is 45 mmHg.  What do you do?

38. Answer:  Based on the Pa02:Fi02 formula, you need to increase the Fi02 from 6 lpm simple mask to 88% Pa02 : Fi02 as Pa02 you want :Fi02 you need 45: 50% as 80 : x 45 x =.5 x 80 45 45 X =.88 Or 88% Fi02 needed is to get Pa02 about 80 mmHg

39.  Identify the supplementary 02 device you need to deliver 88%

40. Answer:  To get an Fi02 of 88% you need to switch to a non-rebreather mask

41.  How long can this patient stay on this device without suffering side effects?

42. Answer:  He is at risk of getting 02 toxicity if he wears Fi02 100% for 24 hours  And he can get into trouble with Fi02 70% within 2 days so he’s got about a day to get off this 02.

43.  What can you do under these circumstances to get him off NRM?

44. Answer:  He is in refractory hypoxemia. We need to wean his Fi02 back down to less than 50%. If we cannot do this-- then we need to consider other options such as mechanical ventilation or CPAP. For example we might put him on CPAP so that we can decrease his Fi02 below 50%

45.  What might we have done in the beginning of this case study that would have avoided a lot of changes in therapy?

46. Answer: 1.We probably needed to get the ABG after the first 2 lpm nasal cannula didn’t work. 2.Also, in smoke inhalation, going straight to a NRM is frequently the first choice because [1] the patient may have CO poisoning [2] persons in chemical pneumonitis are frequently in refractory hypoxemia