Pulmonary Function Tests

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Pulmonary Function Tests

• Mike Poullis

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Overview

• Lung Volumes
• FVC and FEV1
• Ratios FVC/FEV1
• Obstruction, restriction and mixed pictures
• Flow Volume loops
• Upper airway obstruction
• Dead space
• V/Q scanning
• DLCO
• Zones of West
• Predicting post op FEV1 and DLCO
• BTS Guidelines

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Lung Volumes
TLC RV ERV TV IRV. VC ERV TV IRV.
FRC RV ERV.
TV
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TLC

• TLC lt 80 of predicted value restriction.
• TLC gt 120 of predicted value hyperinflation.

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FVC/FEV1
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Definitions

• FEV1 - forced expiratory volume 1 - the volume of
  air that is forcefully exhaled in one second.
• FVC - forced vital capacity - the volume of air
  that can be maximally forcefully exhaled
• FEV1/FVC - ratio of FEV1 to FVC, expressed as a
  percentage
• PEF - peak expiratory flow rate - the peak flow
  rate during expiration

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Comparison
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FVC FEV1 ratios
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Normal
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Obstruction Severity
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Mild Obstruction
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Mild and severe obstruction
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Restrictive Lung Disease
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Restrictive Lung Disease
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Obstruction, Restriction, Mixed
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Upper Airway Obstruction

• Variable extrathoracic obstructions
• vocal cord paralysis,
• thyromegaly,
• tracheomalacia, or
• Neoplasm
• Large airways variable intrathoracic obstructions
• tracheomalacia or
• neoplasm
• Fixed obstruction
• tracheal stenosis,
• foreign body, or
• neoplasm.

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Variable Extrathoracic Upper Airway Obstruction
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Fixed Upper Airway Obstruction
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Anatomical verses physiological dead space

• In physiology, dead space is air that is inhaled
  by the body in breathing, but does not partake in
  gas exchange.
• Anatomical dead space - the gas in the conducting
  areas of the respiratory system, such as the
  mouth and trachea, where the air doesn't come to
  the alveoli of the lungs.
• Alveolar dead space - the area in the alveoli
  that does get air to be exchanged, but there is
  not enough blood flowing through the capillaries
  for exchange to be effective.

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Quantitative VQ scans
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Diffusion Capacity

• This is a test of the ability of inhaled carbon
  monoxide to diffuse into the pulmonary
  circulation.
• It is dependent on functional alveolar capillary
  membrane surface area and red blood cells within
  the circulation.
• It is reduced when ever there is a loss of
  functional alveolar capillary membrane surface
  area or decrease in hemoglobin.
• The diffusion capacity is "corrected" for lung
  volume by dividing by VA (alveolar volume). This
  gives an estimate of the diffusion capacity of
  the lung volume that is present.

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VQ mismatch Zones of West
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Predicting post operative FEV1 and DLCO

• epoFEV1 preFEV1 (19 - segs. to be removed)
• If any segments obstructed use
• epoFEV1 preFEV1 (19 - a) - b)/(19 a)
• a no. of obstructed segments
• b no. of unobstructed segments to be resected
• Right upper lobe 3, left upper lobe 3
• middle lobe 2, lingula 2
• right lower lobe 5
• left lower lobe 4

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verses Actual FEV1

• 2 L for pneumonectomy
• 1.5 L for lobectomy
• Risk model based on
• Think patient size

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BTS Guidelines

• PART I FITNESS FOR SURGERY
• Age
• Pulmonary function
• Cardiovascular fitness
• Weight loss, performance status and nutrition
• Multiple risk factors
• PART II OPERABILITY
• Diagnosis and staging
• Operability and adjuvant therapy
• Operations available
• Locally advanced disease
• Small cell lung cancer

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BTS Bottom Line

• Pred FEV1, DLCO
• 40 magic numbers
• Exercise test if not sure

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250metres