RS Lec 4 Flashcards
lung compliance (def.) - (3)
- measure of the elastic properties of lungs
- measure of how easily the lungs can expand
- magnitude of change in lung volume produced by change in transpulmonary pressure (slope in P-V curve)
two types of lung compliance
- static compliance
- dynamic compliance
static compliance (def.)
-lung compliance during periods of no gas flow (during inspiratory/expiratory pause)
static compliance determined by
-P/V slope measured at FRC (end of expiratory effort)
dynamic compliance (def.)
-lung compliance during periods of gas flow (inspiration, when Ptp changes)
dynamic compliance reflects
-lung stiffness, airway resistance
dynamic compliance decreases when (2)
lung stiffness/airway resistance increase
dynamic compliance & static compliance relationship
-dynamic compliance is less than/equal to static lung compliance
pressure-volume relationship (1. Stable VL)
-at low lung volumes, difficult to pop open airways, rising Ptp little effect on lung volume
pressure-volume relationship (2. Opening of airways)
-first increases in lung volume open proximal airways, recruitment of other airways
pressure-volume relationship (3. expansion of airways)
-all airways are open, Pip is more negative by chest wall expansions, increases V (linear)
pressure-volume relationship (4. limit airway inflation)
-at high lung volumes, lung compliance decreases
hysteresis
-difference between inflation + deflation compliance paths
greater pressure difference (lung compliance)
-needed to open airway than keep from closing
lung compliance determined by (2)
- elastic components of lungs + airway tissue (elastin + collagen)
- surface tension at air-water interface in alveoli
location of elastic components of airways
-alveolar walls, around vessels, bronchi
elastic behaviour determined by
-geometrical arrangements, not typically elongation of fibers
collagen (twine) characteristics (3)
- high tensile strength
- inextensible
- stiff (low compliance)
elastin (weak spring) characteristics (3)
- low tensile strength
- extensible
- spring- high compliance
emphysema (def.)
-floppy lungs due to elastin destruction + alveolar wall destruction
emphysema effects (3)
- increased compliance, less elastic recoil
- little Ptp changes, large changes in lung volume
- time to fill increased
pulmonary fibrosis (def.)
-collagen deposition in alveolar walls in response to injury, silica dust, asbestosis
pulmonary fibrosis effects (2)
- reduction in lung compliance (stiff lungs)
- large Ptp needed for little changes in Lung volume
Surface tension (amount for elastic recoil)
-2/3 of elastic recoil of lungs, decreases lung compliance