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Diagnostic Testing Pt 2 Flashcards

Principles of Pulm Med Chapter 3 (previously assigned), Appendix B, and Appendix C 1. List and discuss the indications for arterial blood gases (ABGs), including the risks to the patient, cost effectiveness, and patient education. 2. When given a clinical scenario, correctly interpret ABG results. 3. Discuss the pathological changes occurring in the body as they relate to acidosis and alkalosis on ABG results. 4. List and discuss the indications for ventilation-perfusion scans (V/Q scans),

1
Q

In practice, which two tests are very rarely completed these days?

A

VQ Scanning and Pulmonary Angiography, but they are still important to know about in limited resource areas.

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2
Q

This test evaluates the mismatches between ventilation and perfusion

A

Ventilation/Perfusion Scanning (VQ Scanning)

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3
Q

In VQ scanning where are radioactive chemicals inserted into the body?

A
  1. Inhaled

2. IV injections

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4
Q

After injective/inhalation of radioisotopes, what is done?

A

A scanner measures the gamma radiation in the blood flow and ventilation throughout the lungs

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5
Q

Segmental Anatomy of the Lungs are important and used for?

A

Analysis of VQ scanning to know where certain mismatching is occurring – indicating disease.

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6
Q

Three main phases of ventilation scanning:

A
  1. Wash-In
  2. Equilibrium
  3. Wash-out
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7
Q

During which phase of ventilation scanning would we be able to identify gas trapping if evident?

A

Wash out due to obstruction

**Commonly seen in COPD

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8
Q

The ventilation study is performed in the ________ projection to cut down on artifact created from soft tissues and to maximize the number of pulmonary segments seen.

A

Posterior.

This is also because the gas used (Xenon) is fat soluble and can be absorbed in the breast tissue, so posterior would avoid that.

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9
Q

Uptake of the tracer throughout the vasculature would indicate:

A

Healthy perfusion scan because it has gone through all the vasculature.

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10
Q

Tracer for Perfusion Scan

A

Albumin with radioactive particles

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11
Q

Tracers in perfusion scan are injected into the _____.

A

Venous system

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12
Q

True/False

Pulmonary arteries are primarily seen on the perfusion scan as opposed to bronchial arteries.

A

True

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13
Q

What would areas that are not perfused going to indicate?

A

Arteries blocked by clots

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14
Q

What are the results of a Perfusion Scanning?

A
  1. High Probabilty of PE
  2. Intermediate Probability of PE
  3. Low probability of PE
  4. Normal
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15
Q

What are the indications to perform a V/Q Scan?

A
  1. Diagnose PE

Assess lung function:

  1. Prior to resection for lung cancer
  2. Prior to lung volume reduction
  3. Prior to lung transplantation
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16
Q

High Probability for PE would

A

Greater than or equal to 2 segmental or larger perfusion defects with normal ventilations

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17
Q

Low Probability for PE would

A

Small or segmental perfusion defects, matched defects, radiographic abnormality larger than defect.

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18
Q

Normal

A

No perfusion defects

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19
Q

Most patients have _____ probability VQ scans.

A

Intermediate.

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20
Q

Likelihood of diagnosing PE with VQ scan

A

15-85%

In other words, it’s too variable to determine

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21
Q

What is the Gold Standard for diagnosis of Pulmonary Embolism?

A

Pulmonary Arteriography

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22
Q

What is a happening in a Pulmonary Arteriography?

A

Catheter is advanced into the right heart into the pulmonary artery. Contrast dye is injected during fluoroscopy.

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23
Q

This scan is commonly paired with V/Q scan when there is a clinical suspicion is high but it is not diagnostic.

A

Pulmonary Arteriography

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24
Q

Contradictions and Risks of Pulmonary Arteriography

A
  1. Increased bleeding risk (Coagulopathy)
  2. Renal Failure
  3. Left Bundle Branch Block - pt must me paced during the procedure to prevent heart block.
  4. This could also cause RBBB
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25
Q

Complications of Pulmonary Arteriography

A
  1. Death
  2. Severe Cardiopulmonary compromise requiring endotracheal intubation or CPR
  3. Renal Failure requiring hemodialysis
  4. Renal Failure not requiring hemodialysis
  5. Groin hematomas requiring transfusion of at least 2 units of blood

Complications are more likely in patients that are more ill - i.e. there is a higher complication rate inpatients referred from the ICU for arteriography

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26
Q

Pulmonary Arteriographs are …

A
  1. Expensive
  2. Invasive (i.e. carries some risk of harm)
  3. Requires skilled radiologists
27
Q

V/Q scan may be indicated when there is a high suspicion of pulmonary embolism and dye cannot be given because of _________ or ___________.

A

Severe Allergy;

Renal Failure

28
Q

Indications for Pulmonary Angio

A
  1. Before Pulmonary thrombendarterectomy

2. Bronchial artery angiography is done as part of procedure when embolization is done for massive hemoptysis

29
Q

ABG

A

Arterial Blood Gases

30
Q

ABGs are useful for determining:

A
  1. Acid/Base Disturbances
  2. Efficacy of Ventilation (based off CO2 level)
  3. Oxygenation
31
Q

What is the normal values for a pH in a ABG?

32
Q

What is the normal values for a pCO2 in a ABG?

33
Q

What is the normal values for a pO2 in a ABG?

34
Q

What is the normal values for a HCO3 in a ABG?

35
Q

What two systems control Acid and Base in Body?

A

Respiratory (Lungs)

Metabolic (Kidneys)

36
Q

High PaCO2 would indicate?

A

Respiratory Acidosis

37
Q

High HCO3 would indicate?

A

Metabolic Alkalosis

38
Q

First step when looking at ABGs:

A

Look at the pH
Is it acidosis or alkalosis?
1. Acidosis pH < 7.35
2. Alkalosis pH > 7.45

39
Q

Second step when looking at ABGs

A

Look at PaCO2 and serum HCO3 and determine the primary disorder (respiratory vs metabolic)

40
Q

PH 7.26
PaCO2 56
HCO3 23

A

Respiratory Acidosis

41
Q

PH 7.56
PaCO2 37
HCO3 41

A

Metabolic Alkalosis

42
Q

Third Step when looking at ABGs

A

Look for compensation

43
Q

If you hyperventilate all day your kidneys will compensate by spitting out more

A

Serum bicarbonate

44
Q

If you are put into metabolic alkalosis due to excessive vomiting, then your body will increase ________ to try and maintain homeostatic pH.

45
Q

Will body compensation ever be able to bring your body back to a completely normal or homeostatic state?

A

No! It will never get back to normal.

46
Q

Two ways to determine Metabolic Acidosis

A
  1. Anion Gap

2. Non-anion gap

47
Q

How do you measure the anion gap?

A

Na+ - (Cl- + HCO3-)

48
Q

What is the normal range for a metabolic state?

49
Q

MUDPILES indicates?

A

Metabolic Acidosis:

Methanol
Uremia
Diabetic ketoacidosis or starvation
Propylene glycol (alcoholics)
Isoniazid
Lactic acidosis
Ethylene glycol (antifreeze)
Salicylates, seizures
50
Q

What is non-anion metabolic acidosis?

A

Loss of Bicarbonate!!!

51
Q

Causes of Non anion metabolic acidosis

A

GI losses: Diarrhea, ileal conduit

Urinary losses: Proximal or distal renal tubular acidosis

52
Q

How does hyperventilation cause respiratory alkalosis?

A

Hyperventilation is more CO2 being excreted than O2 being taken in, so this causes a hypoxic state in the lung.

53
Q

How does chronic hyperventilation cause respiratory acidosis?

A

Hyperventilation is more CO2 being excreted than O2 being taken in, so this causes a hypoxic state in the lung.

After consistent hyperventilation, the diaphragm and respiratory muscles become fatigued causing hypoventilation.

In hypoventilation, CO2 levels aren’t being increased relative to the amount of O2 coming in. Creating a respiratory acidotic state.

54
Q

Acid or Base? CO2

55
Q

Acid or Base? HCO3

56
Q

What can cause respiratory acidosis?

A
  1. Hypoventilation
  2. CNS Depression
  3. Neuromuscular Disorders
  4. Airway Obstruction (Upper or Lower)
  5. Lung Parenchymal Abnormalities (pneumonia, pulmonary edema, restrictive lung dz)
  6. Thoracic Cavity Abnormalities (pneumothorax, flail chest, kyphoscoliosis)
57
Q

What can cause Hyperventilation?

A
  1. CNS Disorders
  2. Pain, Anxiety
  3. Drugs (Salicylates)
  4. Sepsis
  5. Hepatic Failure
58
Q

A 55 year old man is given morphine for pain today. He is breathing around 7 times per minute.

His ABG results show:
pH 7.08
pCO2 80
pO2 80
HCO3- 28
A

Respiratory Acidosis

You know it’s Respiratory because the PaCO2 is high

Note: HCO3- is a bit abnormal due to compensatory, but the pH is still acidosis

59
Q

A 24 year old female with diabetes who presented with abdominal pain. Lab results show:

Na+ 135
Cl- 100
HCO3 15
Glucose 600
pH 7.3
pCO2 30
pO2 100
A

Based on the pH: Acidosis
Based on the the Bicarb: We see a significant decrease
pCO2 and pO2 indicates a slight increase, but not enough

Calculate the Anion Gap:

135 - (100+15) = 20
Elevated!

** These results are consistent with DKA

60
Q

Decreased oxygen content of blood - paO2 less than 60 mm Hg and the saturation is less than 90%

61
Q

Inadequate amount of oxygen available to or used by tissues for metabolic needs, ie low O2 with symptoms such as tachycardia, mental status change

A

Hypoxia – clinical condition

62
Q

Look at the oxyhemoglobin curve

A

On physio slides

63
Q

Causes of Hypoxia?

A
  1. Low inspired oxygen level (altitude, airplane)
  2. Hypoventilation
  3. V/Q Mismatch (most common)
  4. Shunt (from artery to vein with no delivery of O2)
  5. Diffusion abnormalities (Pulmonary fibrosis)
64
Q

If hypoxic, what should you do?

A 
Physical examination -- Evidence of Lung Dz
Chest X-ray
Chest CT scan
Pulmonary Function testing
Shunt study (100% oxygen test)

Pulmonary Medicine (14 decks)

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