Lung testing, ABG and Pleural Effusion

Question 1

what is the mechanism behind pleural effusions

Answer 1

they arise when the balance between pleural fluid production and absorption has been disrupted

Question 2

what are the common symptoms of a pleural effusion

Answer 2

SOB, cough, chest pain (often pleuritic), heavy chest

Question 3

name the signs of a pleural effusion

Answer 3

reduced chest expansion, reduced tactile vocal fremitus, stoney dull percussion, quiet breath sounds, bronchial breathing above fluid level, pleural rub due to pleural inflammation.

Question 4

what should you do with the pleural fluid you obtain from sampling

Answer 4

Send 100ml to cytology, do biochem for LDH, protein, glucose, Should do paired serum samples, send a sample to micro and make sure to include a test for TB. If possible empyema then send blood cultures as well.

Question 5

what are the normal parameters for an ABG

Answer 5

pH: 7.35 – 7.45.
H+: 36-43
PaCO2: 4.7-6.0 kPa.
PaO2: >10.5 kPa.
HCO3-: 23-30 mEq/L.
Base excess: -2 to +2 mmol/L

Question 6

Name some common pitfalls in spirometry

Answer 6

appropriately trained technician, effort and technique dependent, patient frailty, patient in pain or too unwell to perform the exam

Question 7

What is residual volume and what will happen to it in emphysema and why

Answer 7

Residual volume is the volume of air remaining in the lungs after maximal exhalation.
Will increase in emphysema due to the air trapping that occurs

Question 8

what pattern will you see on spirometry in obstructive lung disease

Answer 8

FEV1/FVC ratio will be <70%

Question 9

Describe the different classes of COPD based on % predicted FEV1

Answer 9

mild - >80%
Moderate - 50-80%
Severe - 30-50%
Very severe - <30%

Question 10

what pattern will restrictive lung disease show on spirometry
Name some causes of a restrictive pattern

Answer 10

FEV1 and FVC reduced. FEV1/FVC ratio >70%
ILD, kyphscolliosis, previous pneumonectomy, obestiy,
neuromuscular disease

Question 11

what is transfer factor a measure of

Answer 11

gas exchange in the ungs. Give patient CO and the measure the concentration of exired gas that is breathed out to give you an idea of breath exchnage ub the body.

Question 12

when will transfer factor be reduced

Answer 12

emphysema, ILD, pulmonary vascular disease, anaemia

Question 13

name some factors that affect transfer factor

Answer 13

alveolar surface area
pulmonary capillary blood volume
haemaglobin concentration
ventilation-perfusion mismatch

Question 14

what method would you use to measure the residual volume

Answer 14

body plethysmography: perform respiratory manoeuvres in a sealed box leading to changes in the air pressure with can be measured to derive the lung volumes

Question 15

name some causes of a V/Q mismatch

Answer 15

hyppventilation, ventilation/perfusiojn mismacth (COPD, pneumonia), shunt (blood bypasses the lungs completely), low levels of inspired oxygen

Question 16

what is hypoxic pulmonary vasoconstriction

Answer 16

system whereby the body detects alveolar hypoxia and so the pulmonary blood vessels in that area constrict, reducing blood flow to that area of the lung

Question 17

when is a throacoscopy indicated

Answer 17

in undiagnosed, cytology negative pleural effusion