Basic Interpretation SG (1)

Types of spirometric graphs (2)

1. Flow volume

2. Volume time

Flow-volume curve w/ obstruction

1. low peak flow (shorter top)

2. Stopped or concave (L/toilet shaped)

3. Total volume is lower (shorter x-axis)

Flow-volume curve w/ restriction types (3)

all have lower volumes + NO concave (flat slope)

1. Parenchymal disease/alveoli problem: NORMAL peak + exhalation (slope), SMALL volumes (tiny x-axis spread)

2. Chest wall: Normal shape BUT small peak and volumes.

3. NMD: small + round peak b/c lack of muscle strength and volumes.

What makes a normal flow-volume curve (each part)?

1. Peak: sharp if has muscle strength

2. Slope: exhalation is good if no problem w/ airways

3. Duck butt: upward concavity that shows a slight “plateau” of expiratory, aka got them to empty

4. Volume curve: inspiration was maximal and curved back

Flow-volume curve: variable vs fixed upper airway obstructions types

Two types:

1. variable: obstruction is present based on EITHER max insp. OR exp. Good example of this is Jen’s friend w/ vocal cords (she could move air through vocalizing, but inhaling produced a wheeze)

2. Fixed: obstruction not changing based on efforts. Example being a tumor.

Flow-volume curve: upper airway obstruction types and how it reflects on a curve (3)

1. Stridor: easy to get OUT (normal peak, slope, butt), hard to get IN (flat/low volumes) b/c stridor = increased Raw @ UA, normal LA.

2. Wheeze: easy to get IN (normal volumes), hard to get OUT (short peak + wobbly/short slope) b/c UA are patent, LA are narrow.

3. Obstruction at any point throughout trachea: hard to get IN AND OUT, creates HAMBURGER shape: low peak, flat/small slope + volumes.

Causes of upper airway obstruction

1. variable extrathoracic (tumors, structures, vocal cord paralysis)

2. variable intrathoracic (tumors, structures, tracheomalacia)

3. fixed (non-dynamic tumors and fibrotic structures)

Spirometry tree

1. Assess FEV1/FVC ratio

   1. IF normal ratio:

      1. IF have normal FVC + FEV1: NORMAL

      2. IF reduction in both: RESTRICTION

   2. IF ratio <0.7:

      1. IF isolated reduction in FEV1: OBSTRUCTION

      2. If decreased FVC: MIXED

LLN vs actual normal

LLN (lower limit of normal). Example being FVC predicted of 4.25, but LLN is 4.0, means that there is a RANGE of normal.

The ABSOLUTE cut off for low is 0.7.

Obstruction grading based off GOLD

Mild: >80%

Moderate: 50-79%

Severe 30-49%

Very severe: <30%

What spirometry test result values equals obstruction?

FVC or FEV1 increased by >12% AND 200mL

Reversibility in spirometry

Bronchodilator response can prove reversibility in asthma AND COPD

False negative: medications/caffeines not withheld, exercise

FEF25-75% importance

Helps understand why concave exists + where airflow is being impeded.

Not specific for small airway, not indicated in bronchodilator response and highly variable b/w people + test.

Where to look on graph in order

1. Look at loop (good “punch”)

2. FEV1/FVC ratio

3. FEV1

4. FVC

5. PEFR (good “punch”)

6. FEF 25-75% (angle of flow)