This document discusses pulmonary flow volume loops, which can identify obstructive or restrictive ventilatory defects. Obstructive defects cause the descending limb of the loop to have an upward concavity. Restrictive defects cause the loop to become tall and narrow or miniature in all directions. Specific loop patterns indicate fixed or variable upper airway obstruction, intrathoracic variable obstruction, or extrathoracic variable obstruction. Mixed defects show both curvilinear and miniature loop shapes. Examples of conditions that can cause these patterns are also provided.

1. Pulmonary Flow Volume Loops
Dr.Padmesh
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6. The abnormality can be due to either
Obstructive or Restrictive ventilatory defects.
• In Obstructive ventilatory defect,
-Level of obstruction ie., intrathoracic (below
6th tracheal ring) or extrathoracic,
-Fixed or variable
-Reversibility to bronchodilators
• In Restrictive defect,
-Stage of disease (early or late)

8. • Peripheral Obstructive Flow Volume curves are recorded in diseases such as
asthma, chronic bronchitis and emphysema.
• Most characteristic feature is the curvilinear shape (up- ward concavity) of
descending limb of curve .
• This loss of linearity is related to the severity of the obstruction as well as the
type of disease.

10. • i) Fixed upper airway obstruction: Both the inspiratory and expiratory limbs are truncated.
The shape is quite characteristic with more or less equal restriction of both inspiratory and
expiratory flow rates.
• ii) Intrathoracic variable obstruction : Obstruction at expiration. Expiratory limb is flattened
and inspiratory limb is normal.
• iii) Extra thoracic variable obstruction : Obstruction at inspiratory phase. Inspiratory limb is
flattened and expiratory limb is normal.

11. • Eg: Tracheal stenosis

12. • Extra thoracic variable obstruction : Obstruction at inspiratory phase.
Inspiratory limb is flattened and expiratory limb is normal.
• Eg: vocal cord paralysis, extrinsic compression from cervical
tumour, goiter, etc.

13. • Intrathoracic variable obstruction : Obstruction at expiration.
Expiratory limb is flattened and inspiratory limb is normal.

16. • Restrictive Ventilatory Defect
• Any disease which decreases the lung expansion either by chest wall diseases or by
space occupying lesion in the pleural cavity or lung causes restrictive type of
abnormality.
• In early interstitial lung disease (curve a) even before lung volumes are decreased, the
FV curves usually show super maximal expiratory airflow associated with a steep
descending limb of the curve (due to increase in lung elastic recoil) and the curve
becomes tall and narrow or vertically oriented with respect to the volume axis.
• In severe reduction of lung volumes (curve b), the FV curve may maintain a relatively
normal shape but appears miniatured in all directions.

17. • Examples of restrictive lung disease are pulmonary
fibrosis, pneumonias, pleural effusion, obesity, damage to the nerve
supply to the respiratory muscle, etc.

20. • Mixed Ventilatory Defects
• This is a combination of both obstructive and re-strictive
abnormalities. Both curvilinear and miniature shapes are seen in the
these situations, e.g. pneumoconiosis

25. •Thank you!
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