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What are the divisions of the airway?
- Trachea, Branchii, Branchioles, Alveoli
- Smooth Muscle--------------->|
- Cartilage--->|
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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
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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.
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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).
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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
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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.
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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.
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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.
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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.
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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.
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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
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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
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