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21 Cards in this Set
- Front
- Back
Intrapleural Pressure
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-Less than atmospheric pressure because the lungs and chest wall pull away from each other.
-Intrapleural pressure varies along the lung due to gravity and during respiratory cycle. |
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Intercostal Muscles in Ventilation
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-Internal: Forced Expiration
-External: Inhalation |
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Respiratory Muscles: Inspiration
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Diaphragm
External Intercostals Accessory: Scalenes & Sternocleidomastoids |
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Respiratory Muscles: Normal Expiration
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NONE - Elastic Recoil of lung
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Respiratory Muscles: Forced Expiration
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Abdominal Muscles (int & ext. oblique, rectoabdominal and transverse abdominal)
Internal Intercostals Some muscles of the back and neck. |
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Respiratory Cycle
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1. End of quite expiration - muscles at rest - balance of forces equal.
2. Inspiration - contraction of inspiratory muscles - ^ thoracic volume > decreased ip pressure. 3. Expiration - Relaxation- elastic recoil - increased intrapleural pressure. 4. Contraction of expiratory muscles - decreased thoracic volume - increased ip pressure |
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Pneumothorax
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Air within the pleural space due to disruption of pleural membrane
- Lung collapses due to elastic recoil. - Insert chest drain to remove air and re-expand the lung. |
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Haemothorax
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-Common after both penetrating and blunt trauma.
-Pleural cavity can hold up to three litres of blood. -Insert chest drain and remove blood and re-expand the lung. |
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Compliance
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Change in Volume/ Change in Pressure
(At low volume,pressure is low = lung is easy to stretch. At high volume, pressure is high = lung is difficult to stretch) |
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Emphysema & Fibrosis: Compliance
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Emphysema lungs more compliant.
Fibrosis lungs less compliant. |
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Total Compliance (lung + chest wall)
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- Lung Compliance: Always wants to collapse, never reaches zero pressure.
-Chest wall compliance : Zero pressure at 60% VC. < chest wants to collapse > chest wall wants to expand |
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Factors affecting Compliance
Tissue Forces + Surface Tension |
Elastin + Collagen = Tissue forces
-Elastin: stretch and recoil. -Collagen: Extends but does not stretch, limits maximal expansion. Surface Tension -Liquid higher ST than gas - pulls alveoli in on themselves. |
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Surfactant
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-Produced by Type II alveolar cells.
- Detergent, prevents alveolar collapse. - Dilution as lung expands, break on rapidly expanding alveoli. -Premature babies lact surfactant. |
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Autonomic Control of Bronchial Tone
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-Parasympathetic via ACh muscarinic receptors : Bronchoconstriction
-Sympathetic - little or no nerve innervation - adrenaline acting on B2-adrenoceptors : Bronchodilation -Peptinergic : Substance P - Neurokinin receptors : constriction VIP- vip receptors :bronchodilation |
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Bronchial Secretions
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Mucus- secreted by goblet cells.
-Increased by activation of cholinergic (para) pathways. -Sympathetic supply has little effect. - a1 =inhibition B2= stimulation -Increased mucus decreases luminal diameter: increased resistance. |
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Measurement of Airway resistance
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FEV1/FVC = 80%
Amount of air expired in 1 second divided by forced vital capacity. |
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Asthma
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-Allergens bind to specific IgE receptors on mast cells.
-Eosinophils and Neutrophils are attracted & perpetuate inflammatory response. -Some inflammatory mediators can cause airflow limitation. -Airway epithelial damage stimulates collagen production. Thickening of basement membrane. - Treat with B2-adrenergic agonists. Corticosteroids can also suppress inflammation. |
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Ideal Gas Law
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One mole of a gas will occupy 22.4 litres at atmospheric pressure and 0oC irrespective of species.
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Daltons Law
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Total Pressure is equal to the sum of the partial pressures of each gas in the mixture.
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Henrys Law
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The concentration of a gas dissolved in a liquid is proportional to the partial pressure in the gas phase. The solubility of the species is the proportionality constant.
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Diffusion of Oxygen
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Rate of O2 transfer is proportional to alveolar Po2 - capillary Po2.
The diffusion capacity of O2 allows equilibrium between alveoli and blood in 0.25s. |