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2011-04-12 14:01:43
Bio Mechanical

Engineering Bio Mechanics
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  1. What are the divisions of the airway?
    • Trachea, Branchii, Branchioles, Alveoli
    • Smooth Muscle--------------->|
    • Cartilage--->|
  2. What are the partial pressures of the pulmonary system in mmHG?
    • Atmosphere: 160 O2, 0 CO2
    • Alveoli: 100 O2, 40 CO2
    • Blood in: 40 O2, 46 CO2
    • Blood out: 100 O2, 40 CO2
  3. What are the steps to breathing?
    • 1) (Rest) The thorax is always under a slight vaccuum and lungs a slightly expanded to avoid collapse.
    • 2) (Inspiration) A combination of the diaphragm and rib muscle contraction expands the lung cavity reducing the pressure. Alveolies expand causing there pressure to become sub-atmospheric.
    • 3) (Expiration) Muscle relax causing increased pleural pressure, which forces gasses out of alveoli.
  4. Describe pressure volume loops.
    • y-Volume
    • x-pressure
    • The energy used during inspiration is higher than that regained through passive expiration. This differnce is due to heat loss in the muscles.

    **As rate increases the elastic work gets less and heat dissipation increases (Larger loops).
  5. Describe measurements found in Spirometry.
    • 1) Inspiratory reserve (IRV) = Max - Max tidal
    • 2) Expiratory reserve (ERV) = Min tidal - Min
    • 3) Residual (RV) = min
    • 4) Inspiration capacity (IC) = IRV + TV
    • 5) Functional residual capacity (FRC) = ERV + RV
    • 6) Vital Capacity (VC) = IC + ERV
    • 7) Total lung capacity = VC + RV

    **TV ~0.5L
  6. How is lung compliance defined?
    Plot Volume (y) against Transmural Pressure you get a log curve. Compliance is the inverse of stiffness = DV/DP.

    High compliance (Low stiffness) initially and low compliance (High stiffness) after.
  7. Discuss effects of emphysema, fibrosis, elderly, obesity.
    • 1) Emphysema - (COPD) Elastic tissues of lung is destroyed. Get a large floppy lung. VC goes up due to increased RV, but pressure goes down reducing ERV. Inner circle gets closer to outer circle.
    • 2) Pulmonary fibrosis - Lung scarring. IC and ERV decrease (VC decreases) because lung can not expand/contract well.
    • 3) Old age - RV increases, ERV decreases.
    • 4) Obesity - ERV decreases substantially.
  8. Explain how surfactants stop alveolies from collapsing.
    Without a surfactant the surface tension in all alveolies would be the same, causing a larger pressure in the small alveoli (due to the law of laplace) and they would collapse into the larger ones. The surfactant reduces the tension in the small alveoli.
  9. What are the two mechanical ventilation methods?
    • 1) Negative pressure - to the thorax of the patient expands lungs.
    • 2) Positive pressure - to the end of the airway directly inflates the lungs. The trachea can be by-passed during a tracheotomy so the the patient can eat and talk.

    **In both cases expiration is passive.
  10. What are the two ventilation modes?
    • 1) Mandatory - Ventilator determines when to breath.
    • 2) On-Demand - The ventilator breaths when the patient attempts to breath.
  11. What are the 7 control variables for mechanical ventilation?
    • 1) Respiratory rate
    • 2) %O2 (Change Perfusion)
    • 3) Flow (Qdot)
    • 4) Tidal Volumn
    • 5) Peak flow rate
    • 6) PEEP - Positive end expiratory pressure (Helps lungs from collapsing)
    • 7) On-demand sensitivity
  12. What are the two control types?
    • 1) Pressure controlled (Achieve a desire transmural pressure)
    • 2) Volume controlled (Provide calculated control volume)

    **In each case the non-control variable is determined by the patient pulmonary system. DP = Qdot*Resistance