During exhale the muscles relax & recoil b/c low vol & high P.
Anything causing disruption of the intraplural space causes increase recoil & collapse of the lung.
C.)Vol P R/L:.
1. Pressure gradients- 100mmhg- 50mmhg gas moves from area of high P to low P until it equalizes.
2. Boyle's Law: As vol increases P decreases.
Anything interfering with muscles of vent & thorax can create lung/air exchange problems = hypoxia.
2.WOB= work muscles must do to vent the lungs.
a) overcome resistance to lung expansion (compliance).
b) overcome resistance to airflow.
c) meet demand for vent.
a) overcome resistance to lung expansion (compliance).
Compliance is the elasticity of the lung. Increases- easily expands/ .
decreased - hard to expand.
Factors affecting compliance:.
1. Lung elasticity: stiff lungs = decreased comp. Caused by: consolidation, pneumothorax, atelectisis, pneumonia, Cf, pul edema. If decrease comp= increased WOB = use of increased E.
2. Surface tension: surfactant decreases H2O to H2O attraction so alv don't collapse. Helps increase comp. Problems with pul edema, near drowning, ARDS, partial collapse/ collapse = increase surface tension & decrease comp.
3. Resistance of the chest wall.
Restrictions to expansion:.
1. In lung: infiltrative process in the plura caused by air or fluid in the chest wall/ abd.
2. surface tension: Increase surface tension decrease comp.
3. Lung elasticity = decreased comp.
RESTRICTIVE DISORDERS:.
Decrease comp b/c decrease lung expansion.
Increase WOB.
Decrease vol decrease VT.
Present with rapid shallow breathing.
Ie. VT= 600 F = 12 VE = 600 x 12 = 7.2L.
Increase WOB, increase E to main vol they decrease VT & increase freq.
Ie. VE= 400 x 18 = 7.2L they are able to main N min vol with les WOB for them but still use more E than N breathing pattern.
B. AIRWAY RESISTANCE: RESISTANCE TO FLOW CREATED BY THE AIRWAY.
Factors affecting airway resistance:.
1. nature & rate of flow- smooth/turb, speed. Increase turb then increase resist= air blocked by secretion/ obs.
