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EM > WK 12- Acid Base and Chest X-ray > Flashcards

WK 12- Acid Base and Chest X-ray Flashcards

1
Q

What is the normal pH value

A

7.35 – 7.45

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2
Q

What is the normal CO2 value

A

35-45

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3
Q

What is the normal HC03 value

A

24-28

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4
Q

What is the base excess

A
  • The base excess is defined as the amount of H+ ions that would be required to return the pH of the blood to 7.35 if the pCO2 were adjusted to normal.
  • the excess is positive (above 3) in alkalosis
  • the excess is negative (-3) in acidosis
  • 3 +3
  • bigger the number- more acid:base imbalance
  • only tells you about metabolic component (not respiratory)
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5
Q

If you have a low pH and a high PCO2, what is it

A

respiratory acidosis

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6
Q

What causes the O2 curve to shift to the right

A
  • Right shift, lower SpO2 for a given PaO2
  • Increased temperature
  • Increased Hydrogen
  • Increased CO2
  • Increased 2-3-DPG
  • Improve oxygen delivery in tissues
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7
Q

What are the 2 ways to acquire acidosis

A

-2 ways to acquire acidosis
→ too much CO2= lungs are not functioning= respiratory acidosis
→ added to much acid (accumulate H+) to blood/lost bicarb (low HC03)= metabolic acidosis

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8
Q

What are the two ways to acquire alkalosis

A

→ loss of CO2= respiratory alkalosis

→ accumulate bicarb or loss of H+ (acid)= metabolic alkalosis

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9
Q
  • pH= 7.2
  • PO2= 80mmg
  • PCO2= 60mmHg
  • HCO3= 30 mmol/L (low)
A

-low pH, high PCO2, High HCO2
→ high PCO2 triggers high bicarb to try and neutralise→ therefore has primary resp acidosis with compensatory metabolic alkalosis
-never fully compensate→ pH is still low
→ primary process must be the one in the direction of the pH

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10
Q

What is the anion gap

A

-represents the difference between the cations (pos) and anions (neg) in blood
-major cations= Na and K
-major anions= Cl and HCO3
=Cations – Anions
→ Na + K – ( HCO3+Cl)

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11
Q

What is the normal anion gap

A

-normal anion gap should be less than 16
-if above 16= acid is coming from something not normally present in body→ another anion floating around
-if below 16→ acidosis is due to the accumulation of HCL/loss of bicarb
→RAISED ANION GAP INDICATES METABOLIC ACIDOSIS

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12
Q

What causes a raised AG (HAGMA)

A

Raised AG with 1:1 change in bicarb and AG→ cause by ketoacidosis, lactic acids, urea, salycilate- also the causes of metabolic acidosis

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13
Q

What is a NAGMA

A

NAGMA: non-anion gap metabolic acidosis

  • Bicarb loss/consumption→ diarrhoea
  • Acid production
  • Endocrinopathies
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14
Q

What causes metabolic acidosis

A

due to accumulation of H+ or loss of HC03

  • H+ is an acid, so will bind to base HC03-> causing loss of HC03
  • HCO3 can also be lost in diarrhoea without addition of H+ occuring
  • compensated for by resp alklaosis (hypoventilation)
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15
Q

What causes metabolic alkalosis

A

loss of H+ (ie. in vomit)

-compensation by resp acidosis (increased CO2)= hyperventilation

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16
Q

What causes respiratory alkalosis

A
  • drop in CO2
  • hyperventilation, hypoxia at altitidue
  • can be compensated by metabolic acidosis (increasing H+)
17
Q

What causes respiratory acidosis

A
  • Increased CO2

- hypoventilation/resp insufficiency= COPD

18
Q

What is the alveolar arterial oxygen gradient

A
  • refers to tension of oxygen in the alveolar sac compared to blood running past it
  • measured by blood gas and can approximate alveolar concentration
19
Q

How do you calculate the A-a gradient

A

do alveolar pressure- arterial pressure (PO2)

20
Q

How do you calculate the alveolar pressure

A

0.21 x (760mmHg- 47mmHg) – 5/4 x PaC02

21
Q

What does it mean if the Aa gradient is raised

A

ventilation perfusion mismatch→ due to pathologies in the lung

22
Q

How do you calculate the respiratory compensation (winters formula)

A
  • used to calculate the expected PCO2 in someone with metabolic acidosis
  • pCO2= 1.5 x HCO3 + 8 +/- 2
  • if CO2 is higher than calculated compensation= resp insufficiency
23
Q

What is the acronym used for analysing CXR

A

D= details
R= RIPE
R- rotation-> are the clavicles equidistant from the spinous process, do the clavicles and sternum line up
I- inspiration= should be 5-7 ribs seen-> anymore= hyperinflation= COPD
P- projection= PA posterior-anterior view
E- exposure= should be able to see the spinous processes going all the way down the spine
S= soft tissues and bone-> lung tissue (check for consolidation), look at scapula and ribs (check for breaks)
A= airway-> check trachea and bronchus- are they deviated- pneumothorax
B= breathing-> compare lung fields-> divide into middle, upper and lower
C= cardiac-> clear cardiac margins? (lost in pneumonia due to silhouette sign), also check the size of the heart (length of the heart should be 1/3 the size of the thoracic cage)
D= diaphragm= check costophrenic angles (angle between the ribs and diaphragm-> meniscus sign), also check height of the diaphragm->make sure they are equal
E= extras-> ECG lines

24
Q

What structures are found on the right side of the chest in an X-RAY

A

SVC, IVC, RA, hilar structures (right bronchus, pulmonary artery)

25
Q

What structures are found on the left side of the chest in an X-RAY

A

Aortic arch, left atrium, left ventricle, hilar structure (left bronchus, pulm trunk)

26
Q

What is the silhouette sign

A

-when two objects of the same density touch eachother, the edge between them disappear
→ if there is pneumonia (lung filled with pus), then the line between the lung and heart will disappear as they will be same density

27
Q

What is the meniscus sign

A

-loss of costodiaphragm angle→ effusion cause by heart failure and pneumonia

28
Q

What sign is seen in pulmonary oedema

A

-Batwing sing→ fluid in the alveolar tissue

29
Q

What X-ray changes are seen in heart failure

A
  • upper lobe diversion
  • Kerley B lines→ fluid in the interstitial tissue in the peripheral lungs
  • cardiomegaly
  • batwing appearance with severe heart failure
  • pleural effusion
30
Q

What CXR changes are seen in COPD

A
  • Large lung field
  • high number of ribs present due to hyper-inspiration
  • flat diaphragm

EM (11 decks)

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