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Notes How Lungs Work


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Obstructive Lung Disease
(reduced capacity to get air through conducting airways and out of the lungs)
Increased Compliance
Decreased Elastic Recoil
PFTS: FEV1/FRC <75% low
Spirometry=scooped out
Restrictive Lung Disease
(Inability to get air into the lungs and maintain normal air volumes)
Decreased Compliance
Increased Elastic Recoil
Both FEV1 & FVC are decreased
Decreased TLC
Spirometry=little, small circle
Obstructive Diseases:
COPD (chronic bronchitis +
Hyperinflated lungs and air trapping= Increased TLC & RV
Restrictive Diseases
Pulmonary Fibrosis
Interstitial Lung Disease
Infiltrative Lung Disease
Pleural Disease
Chestwall deformities
Increased Compliance
Decreased Compliance
(stiff lung):
Pulmonary fibrosis
Pulmonary Edema
Obstructive Diseases DLCO Effect
Restrictive DLCO effect

Normal=Chest wall disease
Compliance: (V/P), Compliance is the measure of ease at which the lungs expand, the more complient the lung the easier it is for pressure to cause expansion
Reduced Complaince means lungs are stiff and hard to expand
Elastic recoil: Elastic tissue fibers and surface tension tend to collapse alveoli, also the surface tension inside the alveoli pulls them closer, but surfactant reduces this tension to prevent alveolar collapse
Shift to the right: means O2 more readily unloads into tissues.

Obstructive Lung Diseases ?
Decreased pH, Increased CO2, Increased Temp.
Shift to the left: More O2 uptake in the lungs
Restrictive Lung Diseases
Increased PH, decreased CO2, decreased temp
Turbulent flow:
Upper airways
Gas more dense
Laminar flow:
Lower airways
Gas less dense
Diseases w/ Increased Resistance:
Alveolar Ventialation: volume of fresh air entering lungs, expressed as
minute ventilation=TVxRR
A-a gradient=Alveolar O2-arterial O2. Normal=3-16
the A-a gradient locates hypoxemia
Increased A-a gradient:
V/Q mismatch
Right to left shunt
Impaired Diffusion
Normal A-a, w/hypoxia
High ALtitude
Alveolar hypoventilation

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