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Lecture

Mechanics II

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School
Department
Biology
Course
BIOL 1840U
Professor
Peter Cheung
Semester
Fall

Description
Mechanics II—Dynamics I. Basic Principles a. Dynamics—concerned w/ bulk airflow occurring predominantly in conducting zone b. Since cross-sectional area of conducting zone is much less than respiratory zone, airflow velocity & resistance ↑ c. Must have pressure gradient for flow to take place: P1-P2 = Q*R = flow*resist. 8μL R = π(r)4 II. Respiratory Muscles a. Inspiratory—contraction => outward movement of chest wall & (-) pressure inside lungs => air flows in i. Normal P = -100 cmH2O insp ii. Diaphragm—major inspiratory mm. iii. Intercostals & accessory mm also help under stress b. Expiratory—normally passive, only use mm. to expel things (cough) & when in extreme states (aggressive exercise) i. Max exp. Pressure > +100cm H2O ii. Max flow limited more by lung factors than by mm. strength iii. Abdominal mm—major expiratory mm III. Quiet breathing a. Always begins & ends at FRC b. Defined as active mm contraction causing inspiration & passive exhalation c. Process i. From FRC, contraction of diaphragm => outward movement of CW ii. Ppl => PA↓ (<0) & air flows into lungs iii. Lung volume increases iv. Inspiratory mm relax => net recoil force v. P A 0 => expiration vi. Continues until FRC d. Ventilation below FRC requires active contraction of expiratory mm. to ↑P >A IV. Airway Resistance a. Airways = tubes in series => resistance falls w/ successive branching b/c ↑ b. Change i. Active—smooth mm. contraction ii. Passive—↑ lung volume => ↑ radius of airways & ↓resistance c. Relationship between airway conductance & lung volume is linear V. Forced Expiration a. Used to asses mechanics & dynamics of airflow b. Spirometry—inhale to TLC then forcibly exhale to RV i. VC—total exhaled volume (vital capacity) ii. FEV1—volume of air exhaled in 1 second iii. FVC—forced vital cap
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