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Med 1 Block > Interpretation basics > Flashcards

Interpretation basics Flashcards

1
Q

What are the normal value ranges on an ABG?

A

pH = 7.35 - 7.45
PaCO2 = 4.7 - 6.0 kPa
PaO2 = 11 - 13 kPa
HCO3- 22-26 mEq/L
Base excess (BE) -2 to +2 mmol/L

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2
Q

What are the thresholds for hypoxaemia and respiratory failure on ABG O2 sats?

A

PaO2 <10kPa on air = hypoxaemia
PaO2 <8kPa on air = respiratory failure as severely hypoxaemix

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3
Q

What is the basic criteria for type 1 and type 2 respiratory failure?

A

Type 1 - hypoxaemia and normocapnic
Type 2 - hypoxaemia and hypercapnia

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4
Q

What is the typical cause of Type 1 respiratory failure?

A

V/Q mismatch = volume of air in lungs does not match blood flow to lungs

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5
Q

What can cause a low ventilation to normal perfusion mismatch in the lungs?

A

Asthma attack
Pulmonary odema

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6
Q

What can cause a norm ventilation to low perfusion mismatch in the lungs?

A

Pulmonary embolism

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7
Q

Why is O2 low and CO2 norm in type 1 respiratory failure?**

A

PaO2 dec and PaCO2 increases
Increased respiratory drive - trigger inc overall alveolar ventilation (RR),
This corrects PaCO2 but not PaO2

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8
Q

What is the typical cause of Type 2 respiratory failure?

A

Alveolar hypoventilation (not breathing enough per minute)
Stops adequate oxygenation and elimination of CO2 from their blood (cause PaCO2).

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9
Q

What are the different causes of alveolar hypoventilation in type 2 respiratory failure?

A

Inc resistance due to airway obstruction e.g COPD
Dec movement of lung tissue/chest wall pneumonia, rib#. obesity
Decreased strength of respiratory muscles e.g MND, GBS
Drugs depression resp efforts e.g opiods

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10
Q

What is the equation underpinning why CO2 has an acidic affect in the body?

A

CO2 + H2O <—–> H2CO3 <—-> HCO3- + H+

The first part of this reversible reaction is catalysed in both direction by carbonic anhydrase.

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11
Q

What conditions can cause respiratory acidosis?
what are the shows on an ABG?

A

Low pH high paCO2
Asthma and COPD
Respiratory Depression

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12
Q

What conditions tend to cause respiratory alkalosis?

A

Due to hyperventilation
Anxiety
Pain
PE
Pneumothorax

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13
Q

What conditions tend to cause metabolic acidosis?

A

Either increased acid production or acid ingestion
Decreased acid excretion or increased rate of gastrointestinal/renal HCO3- loss

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14
Q

What equation is used to work out the cause of metabolic acidosis?

A

The Anion Gap
Na+ - (Cl- + HCO3-)
Artificial measure used to determine the presence of unmeasured anions mainly albumin.
Measures the balance of neg and positive ions in the blood - how many more cations than anions.

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15
Q

What is the normal anion gap?

A

= 4 to 12 mmol/L?

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16
Q

What are the causes of a high anion gap?

A

DKA
Lactic acidosis
Aspirin OD
Renal failure
Increased production/ingestion or reduced excretion of H+ by the kidneys

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17
Q

What are the causes of anormal anion gap?

A

GI loss (diarrhoea, ileostomy etc)
Renal tubular disease
Addisons disease

Loss of bicarb, replaced by chloride in the plasma, results in stable overall anion concentration

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18
Q

What are the main causes of metabolic alkalosis?

A

Decreased H+ conc, leading to increased bicarb or direct result of increased bicarb
For example - GI loss of H+ (DV), renal loss of H+ (diuretics, HF, nephrotic syndrome), iatrogenic.

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19
Q

What are the difference compensation systems for alkalosis/acidosis?

A

Metabolic system - compensates slowly over days - by dec or inc HCO3-
Respiratory system - compensates quickly by retaining or blowing off CO2.

20
Q

What additional blood results should by analysed in a ABG?

A

Na+ and Cl- = for anion gap is metabolic acidosis
Look at K+ as can be cause of cardiac arrest
Lactate - predictor of how unwell
Glucose - high or low, DKA or hypoglycemic

21
Q

What is the first step when interpreting any results?

A

Confirm patient details
Confirm date and time of test
What was the clinical indication for this test?
Are there any previous tests for comparison?

22
Q

How should the quality of a CXR by assessed?

A

RIPE
Rotation - medial aspect of clavicle should be equidistant from the spinous process, spinous process vertical to vertebral bodies
Inspiration - 5-6 ant ribs, lung apicies, costophrenic angles and lateral rib edges should be visible
Presentation - AP or PA
Exposure - vertebrae should be visible behind heart if very white is over exposed, left hemiD should by visible to the spine

23
Q

What is the A-E approach for CXR analysis?

A

Airway
Breathing
Cardiac
Diaphragm
Everything else

24
Q

What should be considered in the Airway part of a CXR interpretation?

A

Trachea - central or deviated, if deviated pushed ( pleural effusion, tension pneumothorax) or pulled (consolidation with associated lobar collapse)

Carnia and bronchi - present

Hilar structures - no visible lymph nodes, same size,

25
Q

What are some causes of hilar pathology on a CXR?

A

Enlargement - bilaters = sarcoidosis, unilateral/asymmetrical = underlying malignancy

Abnormal position - pushing (enlarging mass) or pulled (global collapses)

26
Q

What should be considered within the breathing section of CXR interpretation?

A

Lung markings present inc at edge of lungs (absence = pneumothorax)
Are zones (three zones on each lungs - NOT LOBES) symmetrical?
Are zones good side and colour
Any increased airspace shadowing? Y=consolidation/malignancy
Is the pleura visible? Y = mesothelioma
Pattern of opacity - increased = fluid, decreased = air.

27
Q

What does a visible pleura indicate on a CXR?

A

Not visible on healthy people
Visible indicates pleural thickening
Norm - mesothelioma - associated with asbestos exposure.

28
Q

What is the cause of a pneumothorax?

A

Damage to pleura
Air from outside in to pleura but can not bet out
Air accumulates in pleural cavity
Positive pressure on lungs - prevents expansion cause respiratory distress
Trachea and structures pushed away from pneumothorax
Compress heart and great vessels - leads to cardiovascular collapse and cardiac arrest.

29
Q

What is the treatment for a tension pneumothorax?

A

Needle decompression.

30
Q

What are the key parts of a cardiac analysis on a CXR?

A

Only comment on PA, AP makes bigger
Heart should be no bigger that 50% thoracic width if >=cardiomegaly
Borders clearly visible including right atrium as right border and left ventricle as left border.

31
Q

What can cause loss of the heart borders on a CXR?

A

Loss of right border = right atrium = right middle lobe consolidation
Loss of left border = left ventricle - lingular consolidation

32
Q

What is important about the diaphragm on analysis of a CXR?

A

R hemi higher due to liver
L - often gastric bubble due to stomach underneath
Free gas under diaphragm - pneumoperitoneum - panic as bowel perforation
Costoprhenic angles should be acute and visible - if missing/blunting due to fluid or flattening in hyperinflation COPD patients

33
Q

What should be considered in he everything else part of examining a CXR?

A

Bones - fractures etc
Soft tissue - breast tissue or hematoma
Equip - NG, ECG leads, central lines, artificial heart valves, pacemakers.
Aortic knuckle loss in AAA
Aortopulmonary window - lost in mediastinal lymphadenopathy.

34
Q

What are the three different categories of blood tests?

A

Haematology, biochemistry and coagulation

35
Q

What blood bottles are used for haematology, biochemistry and coagulation during a blood test?

A

Haematology = purple top
Biochemistry = Gold top
Clotting screen = blue top

36
Q

What blood tests are included within haematology?

A

FBCs
WBC
Platelets

37
Q

What rests are included within a biochemistry blood test?

A

U&Es
LFTs
CRP
Albumin

38
Q

What tests are included in a clotting screen?

A

Coagulation screen
INR
D-dimer

39
Q

How should changes in FBC, WBC and Platelets be indicative of?

A

FBC - low is bleed or anaemia, high polycythemia (COPD)
WBC - high infection or steroid (leukocytosis), low immunodeficiency (leucopenia)
Platelets - Thrombocytopenia acute -bleeding, viral infection, HELLP syndrome, DIC or chronic (cirrhosis, alcohol, iron deficient, HIV)
Thrombocytosis - reactive, inflammation, malignancy.

40
Q

What is the difference between a liver pathology and a biliary pathology in LFTs?

A

Liver - high ALT
Biliary - high ALP

41
Q

What does a low albumin indicate?

A

Poor nutritional intake
Incorrect fluid distribution

42
Q

How to interpret different elements of a clotting screen?

A

Coag screen - bleeding time for platelet function, PTT is a marker of liver function (too high not functioning)
INR - used in warfarin patients - higher indicates longer clotting time
D-dimer - low rules our thrombosis

43
Q

What is the use of the pink blood bottle?

A

Cross match, Group and Saves

44
Q

What is the use of the grey blood bottle?

A

Glucose
Lactate
Ethanol

45
Q

What is the use of a dark green top blood bottle?

A

Ammonia

46
Q

What is a pleural effusion?
How does it tend to present on a CXR?

A

Accumulation of excessive fluid in the pleural space - hydrothorax (serous), haemothorax, empyema.
Blunting of costophrenic angles, prominent upper zone vessels.

47
Q

What is flash pulmonary oedema?
How does it tend to present on a CXR?

A

Rapid onset acute pulmonary oedema
Often precipitated by acute MI, mitral regurg/HF

CXR findings:
Fluid in alveolar walls, batting winging (increased vascular shadowing), kerley B lines (parelel lines at lung edges - represent interlobar septa), possible pleural effusions

Med 1 Block (39 decks)

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