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21 Cards in this Set

  • Front
  • Back
Intrapleural Pressure
-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.
Intercostal Muscles in Ventilation
-Internal: Forced Expiration
-External: Inhalation
Respiratory Muscles: Inspiration
Diaphragm
External Intercostals
Accessory: Scalenes & Sternocleidomastoids
Respiratory Muscles: Normal Expiration
NONE - Elastic Recoil of lung
Respiratory Muscles: Forced Expiration
Abdominal Muscles (int & ext. oblique, rectoabdominal and transverse abdominal)
Internal Intercostals
Some muscles of the back and neck.
Respiratory Cycle
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
Pneumothorax
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.
Haemothorax
-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.
Compliance
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)
Emphysema & Fibrosis: Compliance
Emphysema lungs more compliant.
Fibrosis lungs less compliant.
Total Compliance (lung + chest wall)
- 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
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.
Surfactant
-Produced by Type II alveolar cells.
- Detergent, prevents alveolar collapse.
- Dilution as lung expands, break on rapidly expanding alveoli.
-Premature babies lact surfactant.
Autonomic Control of Bronchial Tone
-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
Bronchial Secretions
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.
Measurement of Airway resistance
FEV1/FVC = 80%

Amount of air expired in 1 second divided by forced vital capacity.
Asthma
-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.
Ideal Gas Law
One mole of a gas will occupy 22.4 litres at atmospheric pressure and 0oC irrespective of species.
Daltons Law
Total Pressure is equal to the sum of the partial pressures of each gas in the mixture.
Henrys Law
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.
Diffusion of Oxygen
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.