TMC Style Question and Explanation 3

After surgery a 170 lb male is receiving mechanical ventilation using the following settings:

  • Mode AC/VC
  • TV 450
  • F 12
  • FIO2 .45
  • Peep 5

ABGs are just resulted:

  • pH 7.16
  • PCO2 69
  • Po2 58
  • HCO3- 23
  • Sao2 91

Which should the respiratory therapist recommend?

  1. Increase fio2 to 55%
  2. Increase rate to 14
  3. Increase peep to 7
  4. Increase TV to 580

First evaluate the scenario and the laboratory results.  The patient is receiving mechanical ventilation following surgery, no pulmonary history is given. The patient’s pH,co2 and Po2 are abnormal.  Ventilation is necessary for survival so we need to address this before the hypoxia is addressed. The two ways to address the ventilation are to increase the TV and increase the RR. You always want to adjust the tidal volume first before adjusting the rr.

TMC Style Question and Explanation Example 2

A 27 year old hospitalized male with pneumonia has the following laboratory results, the results were obtained when the patient was on 1lpm NC

  • pH7.36 RBC 6.5 mil/mm3
  • paCO2  45Hb
  • paO2 59
  • Sao2 88
  • HCO3-  23
  • Hb 15
  • Hct 47
  • WBC 2500/mm3
  • Temp 39C
  • Bp 128/ 78

What should the respiratory therapist recommend?

  1. Administer antibiotics
  2. Initiate non invasive positive pressure therapy
  3. Initiate pep/ flutter
  4. Increase nc to 4lpm

First think we do is analyze the information and ask the following questions in the following order

  1. Is the patient ventilating? Yes the abg reveals a normal pH and Co2
  2. Is the patient oxygenating? No paO2 is 59 (normal is80-100) Hypoxia must be addressed immediately.
  3. Is the patient circulating and perfusing? Yes
  4. Treating the underlying issue

The correct answer is to increase the NC to 4lpm. Starting antibiotics is also right but oxygenation is an emergency and must be treated before we move on to treating the underlying issue of pneumonia with antibiotics and flutter. If the patient’s oxygenation had been normal we would check the patient’s perfusion and move onto the underlying issue since they are circulating and perfusing.

TMC Style Question and Explanation Example 1

Below is a sample question, similar to ones you might find on the tmc exam. This type of question is an analysis type of question , they are the hardest and the least common type of question on the exam . Analysis questions often give people the most trouble on the exam and is the area that causes most people to fail. Practicing analysis type questions will help you prepare for the exam because it requires you to know the normal values and equipment and how to apply each. This will help you on all the other exam questions.

Following surgery a 39 female, that is 5’6”,145 lbs is receiving mechanical ventilation at the following settings:

  • Mode AC
    • TV 500
    • F 13
    • Peep 5
    • Fio2 .45

The following patient values are available

  • pH 7.38
  • PCO2 46
  • PO2 63
  • HCO3- 23
  • CVP 8 cmHG
  • PAP 15mmHg

The respiratory therapist should recommend the following change

  1. Increase the peep to 8
  2. Increase Fio2 to 55%
  3. Increase  TV to 600
  4. Increase RR to 16

The first thing you do is analyze the information and ask:

  • Is the patient ventilating? Yes, her co2 and pH are normal
  • Is the patient oxygenating? No, her pO2 i s 63 so she hypoxic, this must be treated. Two answers here address hypoxia, peep and fio2 since the fio2 is below 60 we address that first. The correct answer is to increase the fio2 to 55%

ABG Analysis Directions And Example 3

Below is an example of a basic abg results and the steps to analyze it.

If you need to review the basics of abg interpretation refer to these steps .

  • pH 7.35
  • Co2 62
  • Hco3 28
  • Po2 61
  1. Is the pH normal? pH is normal so it is compensated
  2. Is the Co2 normal? No, so it is respiratory
  3. Is the bicarb normal? No
  4. Is the pO2 normal? No, so hypoxemia

Compensated respiratory acidosis with hypoxemia

I have a free Basic ABG analysis tip sheet with 6 examples that are explained.

ABG Analysis Example 2

If you need to review the basics of abg interpretation refer to these steps .

  • pH 7.48
  • Co2 22
  • Bicarb 22
  • Po2 71
  • Spo2 92

Is the pH above or below normal range?It is above so we have alkalosis

  1. Is the pH normal? No, it is uncompensated
  2. Is the pH above or below normal range?It is above so we have alkalosis
  3. Is the Co2 normal?  No, it is a respiratory issue 
  4. Is the bicarb with in range?  Yes
  5. Is the Po2 normal?  No, hypoxemia is present

The final analysis uncompensated respiratory acidosis with hypoxemia

For tce test you always ask the following:

  1. Is the patient ventilating?  Yes the patient is over ventilating
  2. Is the patient oxygenating? No, adjustments should be made

I have a free Basic ABG analysis tip sheet with 6 examples that are explained.

ABG Interpretation Example 1

If you need to review the basics of abg interpretation refer to these steps

  • pH 7.28
  • Pco2 57
  • Bicarb 23
  • Po2 72
  • Spo2 94
  1. Look a pH- is it normal? No, it is not so it is uncompensated. The pH is low so it is an acidosis.
  2. Look at PCO2, is it normal? No is not, it is a respiratory issue
  3. Look at the bicarb is it normal? Yes
  4. Look at the PO2 is it normal ? No it isn’t, it is hypoxemia is present

Putting the individual results from above together the final analysis is uncompensated respiratory acidosis with hypoxemia.

During the TMC and clinical simulation exams an example similar to this could be used as part of the scenario. The first question you need to ask is the patient ventilating? Since this patient has uncompensated respiratory acidosis they are not ventilating. Ventilation is necessary for survival so this must be addressed first. If there are no options to address ventilation then we would move on to oxygenation

ABG Interpretation Basics

Before we begin analyzing abgs we need to have the normal values:

  • pH 7.35
  • pCO2 35-45
  • Bicarb 22-26
  • Po2 80-1000

First thing you look at is the pH, is it normal? If it is then it is compensated. If the pH is not normal it is uncompensated.

When the pH is low it is called acidosis.  When the pH is high it is called alkalosis.  (I like to remember it by the c in acidosis is lower in the alphabet then the l in alkalosis is)

If the pCo2 is abnormal it is a respiratory issue.

If the bicarb is abnormal it is a metabolic issue.  

If the pO2 is low their is hypoxemia present

 

Get your free Basic ABG analysis tip sheet and 6 examples explained here