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21 Cards in this Set
- Front
- Back
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inspiration
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- diaphragm
- forced or labored uses 1) external intercostals ( raise anterior chest wall) 2) sternocleidomastoid ( lifts sternum and upper ribcage up and out) 3) scalenes - normal: diaphragm expands by pushing lower ribs out |
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Diaphragm
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- contraction expands thoracic cavity by pushing lower ribs out
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expiration
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- passive from relaxation of inspiratory muscles and compression of thoracic volume
- forced: contraction of abs and external intercostals |
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Gas Flow
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- pressure gradients
- inspiration: contraction of muscles and increased thoracic volume (incrased volume,decrease pressure) - |
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Intrapleural pressure
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- PIP
- potential space between pleura (parietal and visceral) - less than atmospheric at end of expiration (-5 cmH20) |
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Alveolar Pressure
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- PA
- pressure in alveoli - varies with respiratory cycle |
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Atmospheric Pressure
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- PB
- not change so value considered 0 (reference for teh rest) |
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Transmural Pressure
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- PTM
- pressure difference across vessel wall (between inside and outside) |
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Transpulmonary Pressure
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- PTP
- differnce between alveolar and intrapleural pressure - Pa - PIP |
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intrapleural pressure at FRC
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- lungs recoil inward
- chest wall (at low lung volumes recoil outward - at resting expiration in balance with lungs with FRC - PIP -5 cm H2O - PA = PB - no air flow |
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During respiratory cycle
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- PIP becomes more (-) on inspiration
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compliance
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- change in volume/ change in pressure
- L/cmH2O - change in volume on inspiration not linear - hysteresis: difference between inspiratory and expiratory curves - due to airway resistance and surface tension - slope of inspiratory curve --> changes in compliance with increasing volume |
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surface tension
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- unbalanced molecular cohesive forces
- bubble: surface forces contract sphere so smallest volume occupied |
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Law of Laplace
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- decreasing radius increases surface tension on spere and collapse it
- alveoli basically sphere shaped - |
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alveoli
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- connected by airways (like grapes)
- la place would collapse the small alveolus into larger ones |
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hysteresis
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- difference between inspiratory and expiratory curves
- air liquid interface in alveoli - air filled lungs: more difficult to expand than saline filled lungs - air filled lungs less compliant at very low and high volumes |
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Surfactant
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- mixture of lipids and proteins
- alveolar type 2 pneumocytes - constitutive: low production and secretion before birth (35 weeks) - increased with lung hyperinflation, exercise, beta agonists - increases lung compliance - minimizes fluid accumulation in lung |
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thoracic compliance
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- = to total compliance
- ΔV/ΔP = determined by compliance of chest wall and lung combined - 1/CT = 1/CL + 1/CCW) - lung always recoils inward - Cell Wall can go in or out |
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equilibrium point
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- cell wall recoil outward and lung recoil inward =
- lung volume : FRC - airway pressure = 0 |
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Compliance Curves
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- PV curves
- lower area of curve shows work done to get a breath - work due to airway resistance and lung compliance |
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Distribution of ventilation
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- PIP more negative at apex than at bases
- alveoli in apex larger than at base, flatter and less compliant as well - base: steeper portion of P/V curve so ventilate better |
