Resp3&4 - Lung Mechanics & Ventilation of the Lungs w/ Clinical Conditions Flashcards
Definitions of Lung Volumes and Capacities
Tidal Volume
Inspiratory Reserve Volume (IRV)
Expiratory Reserve Volume (ERV)
Residual Volume (RV)
Inspiratory Capacity
Functional Residual Capacity
Vital Capacity
Total Lung Volume
Tidal Volume - volume of air entering and leaving the lungs with each breath
Inspiratory Reserve Volume - maximum volume of extra air that can be breathed in during forced inspiration
Expiratory Reserve Volume - maximum volume of extra air that can be breathed out during forced expiration
Residual Volume - air left in lungs after forced expiration
Inspiratory Capacity - from end of quiet expiration to maximum inspiration (tidal volume + IRV)
Functional Residual Capacity - volume of air at the end of quiet expiration (ERV + RV)
Vital Capacity - maximum volume of air that can be breathed in and out (tidal volume + IRV + ERV)
Total Lung Volume - maximum volume of air that can be breathed in and ‘thoretically’ breathed out (vital capacity + RV)
3 features of dead spaces in the lungs
1.) Anatomical Dead Space - the volume of the conducting airways (nostrils to terminal bronchioles)
- ) Alveolar Dead Space - air in alveoli which dont take part in gas exchange (not perfused) e.g. due to damaged alveoli
- a pulmonary embolism increases alveolar dead space
3.) Physiological Dead Space - anatomical dead space + alveolar dead space
4 features of forces at the resting expiratory level
Rest
Inwards
Outwards
Net Effect
- ) At rest, the lung is subject to 2 equal and opposing forces, one inwards and one outwards
- ) Inward - lungs elasticity and surface tension generate inwardly directed force that favours small lung volumes
- ) Outwards - elasticity of the muscles and CT associated w/ rib cage
- lungs would collapse if outside of the body - ) Net Effect - opposing forces balances out and creates negative pressure within the intrapleural space relative to atmospheric pressure
- pressure in the alveoli = atmospheric pressure
4 features of inspiration
Quiet and Forced
Pleural Seal and Pressure
- ) Quiet Inspiration - contraction of diaphragm (70%) and external intercostal muscles expands the thoracic cavity
- increase in volume –> decreases pressure below atm pressure forcing air into lungs - ) Forced Inspiration - uses accessory muscles
- SCM, scalene, serratus anterior, pec major - ) Pleural Seal - surface tension of pleural fluid holds the outer surface of the lungs to the inner surface of the chest wall
- this ensures the chest wall and lungs move together
4.) Pleural Pressure - negative (relative to atm pressure) at rest and becomes even more negative even during inspiration
2 features of expiration
Quiet and Forced
- ) Quiet Expiration - elastic recoil of lung brings thoracic cavity back to original equilibrium position
- it is a passive process - ) Forced Expiration - uses accessory muscles
- internal intercostals, abdominal wall muscles
5 features of surfactant
Secretion Function Stabilising Effect Effect on Lung Compliance Prevents Oedema
1.) Secretion - by type II pneumocytes in the alveoli
- ) Function - reduces surface tension by disrupting the interaction between fluid molecules
- contains both hydrophilic and hydrophobic regions - ) Stabilising Effect - prevents small alveoli collapsing into larger ones
- w/out surfactant, smaller alveoli have more surface tension so will collapse into larger alveoli
- surfactant is more efficient in smaller alveoli as the molecules are closer together. This allows different sized alveoli to have same surface tension - ) Increases Lung Compliance - reduces surface tension of alveolar fluid
- ) Prevents Oedema - high surface tension in alveoli can create a suction force which can cause oedema from pulmonary capillaries into the alveoli
5 features of interstitial lung disease
What is it? Effect on Lung Compliance Effect on Lung Size Effect on Radial Traction Effect on Diffusion Distance
- ) Infiltrated Interstitial Space - between the alveolar cells and the capillary basement membrane
- contains fibrous tissue (collagen fibres), cells, or fluid
2.) Reduced Lung Compliance - collagen fibres are less stretchy than elastin so lungs are stiffer and harder to expand
- ) Smaller Lungs - due to increased elastic recoil (elastin + collagen)
- chest expansion is reduced on examination
- reduced inspiratory and vital capacity - ) Increased Radial Traction - fibrous tissue exerts an outward pull on the small bronchioles, keeping airways open
- radial traction increases as alveoli expands —> bronchioles more open - ) Greater Diffusion Distance - due to thickened alveolar walls
- effect is greater on O2 than CO2 (more soluble)
3 symptoms
4 signs
5 groups of causes of interstitial lung disease
Symptoms - SOB, less exercise tolerance, dry cough
Signs - tachypnoea, tachycardia, reduced bilateral chest movement, coarse crackles
Causes
Occupational - e.g. abestosis
Treatment Related - e.g. radiation, chemo, amiodarone
CT Disease - e.g. rheumatoid arthritis
Immunological - e.g. sarcoidosis, allergic alveolitis
Idiopathic - fibrosing alveolitis
5 features of respiratory distress syndrome (RDS) in newborns
Surfactant Surface Tension Effect on Lung Compliance Signs x3 Treatment
1.) Surfactant Deficiency - premature babies (esp <30 weeks) are surfactant deficient
- ) High Surface Tension - in fluid lining the alveoli making it harder for lungs to expand
- some alveoli remain collapsed (airless) - ) Reduced Lung Compliance - results in impaired ventilation and increased effort required to breathe
- ) Signs - cyanosis, grunting, intercostal and subcostal recession
- ) Treatment - surfactant replacement via endotracheal tube
- supportive treatment w/ O2 and assisted ventilation
6 features of emphysema
Definition Effect on Lung Compliance Effect on Lung Size Effect on Radial Traction Symptoms x2 Causes
- ) Definition - loss of elastin and breakdown of alveolar walls
- ) Increased Lung Compliance - less elastin means reduced lung elastic recoil making the lungs easier to expand
- ) Hyper-Inflated Lungs - more expanded than due to loss of elastic recoil
- on examination, produces a ‘barrel’ chest - ) Narrowed Small Airways - due to less radial traction
- loss of elastic fibres exerting an outward pull on the small bronchioles
5.) Symptoms - SOB and reduced exercise tolerance
- ) Causes - feature of COPD so mainly smoking
- rarer cause is alpha-1-antitrypsin deficiency
2 features of asthma
Definition
Narrowed Airways x3
- ) Definition - chronic inflammatory process causing reversible airways obstruction
- may be triggered by allergic and/or non-allergic stimuli - ) Narrowed Airways - due to inflammation causing:
- bronchial smooth muscle contraction
- thickening of airway walls by mucosal oedema
- excess mucus production, partially blocking lumen
3 features of a pneumothorax
Definition
Pressure Gradients
Lung Collapse
1.) Definition - where air enters the pleural space with loss of pleural seal and lung collapse
- ) Pressure Gradients - at rest, intra-pleural pressure is slightly below atm pressure
- when an opening is created, air flows down the pressure gradient into the pleural cavity
- until intra-pleural pressure reaches atm. pressure - ) Lung Collapse - loss of pleural seal means elastic recoil of the lung causes it to collapse towards the hilum
- this means ventilation is reduced on the affected side
4 features of atelectasis
Definition
Pulmonary Parenchyma
Compression Atelectasis
Resorption Atelectasis
- ) Definition - incomplete expansion of the lungs or the collapse of previously inflated lung
- ) Airless Pulmonary Parenchyma - due to the collapse
- ) Compression Atelectasis - air (pneumothorax) or fluid (pleural effusion) enter the pleural cavity
- ) Resorption Atelectasis - complete obstruction of an airway. Over time, air is resorbed from alveoli which collapses
- a cause is bronchial carcinoma
