measuring lung function Flashcards

1
Q

what is spirometry? 3

A
  • can be done slowly of forced
  • most often done as forced expiration
  • FVC of tiffeneau manoeuvre: deep breath, don’t hold your breath, put lips around outside of the tube and blow out for as long and hard as you can
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2
Q

how do we interpret spirometry? 4

A
  • FE1/FVC: ratio of FEV1 and FVC values
  • for all other results, compare to actual predicted values
  • predicted values may vary by gender, height and age
  • abnormal result: any result <80% of the predicted value or any results less than the lower limit of normal
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3
Q

how much of FVC should be exhaled in the first second?

A
  • 70%

- if FEV1.FVC is <0.7 then an obstruction is present

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4
Q

what do expiratory flow- volume loops show? 3

A
  • early airflow obstruction
  • mid expiratory flow rates are usually more affected
  • PEFR (peak expiratory flow rate) may be normal
  • where an obstruction is located in the tracheobronchial tree
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5
Q

when is peak flow used normally? 2

A
  • for people with asthma

- it can show extrathoracic obstructions including tracheal, stenosis

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6
Q

explain a peak flow rate? 7

A
  • easy to perform
  • easy to maintain device
  • diagnosis of asthma
  • monitoring day-day variation
  • picking up exacerbations
  • assessing response to treatment
  • mandatory for patients on nebulised Rx
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7
Q

how can we measure lung function?

A
  • helium dilution

- plethysmography

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8
Q

name some causes for lung restriction? 5

A
  • alveolar filling process (pneumonia)
  • lung tissue disease: fibrotic lung disease
  • pleural disease: pneumothorax, large pleural effusion, fibrosis of pleural tissue
  • chest wall disease
  • weakness due to nerve or muscle disease
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9
Q

where does gas exchange take place? 5

A
  • takes place at the alveoli
  • depends on adequate ventilation of alveoli
  • influenced by alveolar surface area and thickness of alveolar membrane
  • delivers oxygen to where is combines with Hb
  • gets rid of carbon dioxide to exhaled air
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10
Q

how do we measure gas transfer? 6

A
  • CO diffuses like O2
  • CO binds to Hb and is carried away
  • inhale known volume of gas with low concentration of CO and helium
  • hold breath for the known time
  • measure CO and He in expired air
  • He dilution give alveolar volume
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