2. Clinical Application In Ventilation And Lung Mechanics Flashcards
What is the conducting portion of the respiratory tract?
Nasal cavity Pharynx Larynx Trachea Primary bronchi Secondary bronchi Bronchioles Terminal bronchioles
What is the respiratory portion of the respiratory tract?
Respiratory bronchioles
Alveolar ducts
Alveoli
What s compliance?
Measure of distensibility. Change in volume relative to change in pressure
What is elastance?
Measure of elastic recoil - tendency of something that has been distended t return to its original size
What is the relationship between compliance and elastic recoil?
Inversely proportional
What is lung compliance also inversely related to?
Connective tissue surrounding alveoli - elastic fibres including collagen and other matrix elements within the lung parenchyma
Alveolar surface tension
What is lung elastic recoil directly related to?
Connective tissue surrounding alveoli - elastic fibres including elastin and collagen and other matrix elements within the lung parenchyma
Alveolar fluid surface tension
What determines airway resistance?
Surface tension within airways
Diameter of airways - mucus in airways, pulmonary pressure gradients, radial traction
How do bronchioles stay open in expiration?
Radial traction (outward tugging action) of surrounding alveolar walls on bronchioles
What is atelactasis?
Lung (alveoli) collapse - inadequate expansion of air spaces
Impaired pulmonary surfactant production or function collapse - alveoli collapse secondary to surface tension
Why do alveoli become compressed and collapse in atelectasis?
Air in pleural cavity (pneumothorax)
Fluid in pleural cavity (pleural effusion)
Tumour
What is resorption collapse in atelectasis?
Due to obstruction
Airway obstructed - air downstream of blockage slowly absorbed into blood stream
Alveoli collapse
How does atelectasis cause impaired respiratory function?
Alveoli not ventilated so can participate in gas exchange
Also collapsed alveoli more suggestible to lung infection including pneumonia
What happens in interstitial lung disease?
Thickening of pulmonary interstitium - sometimes reversible
What does the interstitium contain?
Elastin fibres
Collagen fibres
Fibroblasts
Matrix substance
Where is the interstitium?
Between alveoli and capillaries
What can cause interstitial lung disease?
Specific exposure - asbestos, drugs, mouldy hay etc.
Autoimmune-mediated inflammation
Unknown injury - e.g. idiopathic pulmonary fibrosis
What happens to the lungs in interstitial lung disease?
Lungs are stiff, harder to expand as lung compliance is reduced
What are the symptoms of interstitial lung disease?
Dry cough
Dyspnea on exertion
Fatigue
Typically gradual, insidious progression
What are the signs of interstitial lung disease?
Decreased lung excursion on palpitation
Bi-basal end inspiratory lung crackles
Finger clubbing
Small pleural effusions
When is surfactant produced in foetuses?
Starts at 24-28 weeks gestation
Increasing amounts by 32 weeks
Usually sufficient y 35-36 weeks
What happens in pre term babies to their lungs?
Insufficient surfactant - high surface tension Lung expansion at birth is incomplete Some alveoli remain collapsed Lung is stiff Increased effort is required to breathe Impaired ventilation
What are the signs of neonatal respiratory distress syndrome?
Grunting Nasal flaring Intercostal and subcostal retractions Rapid respiratory rate Cyanosis
What are the similarities between neonatal respiratory distress syndrome and diffuse pulmonary fibrosis?
Both have stiff lungs
Both decreased compliance and increased elastic recoil
What is COPD primarily caused by?
Smoking and/or inhaled pollutants interacting with genetic vulnerability
What does COPD encompass?
Chronic bronchitis
Emphysema
What is pre-COPD?
Air flow impaired but no clinical symptoms yet and normal spirometry
What happens in chronic bronchitis?
Disease of airways
Mucous hypersecretion
Reduced cilia
What does chronic bronchitis lead to?
Air flow limitation/obstruction by luminal obstruction of small airways
Epithelial remodelling
Alteration of airway surface tension predisposing to collapse
What is the clinical diagnosis of chronic bronchitis?
Cough productive sputum, for three months of the year for more than a year
What is emphysema?
Air sacs disease
Abnormal, permanent enlargement of the air space distal to terminal bronchiole, destruction of alveolar walls
What happens to lungs in emphysema?
Inflammatory cells accumulate, release elastases and oxidants, destroy alveolar walls and elastin
Reduced elastic recoil
Large air spaces - reduced surface area for gas exchange
What is barrel chest?
Sign of emphysema
Distance between anterior chest and posterior chest increased
Due to more air in lungs, imbalance of chest wall elastic recoil and lung elastic recoil
What happens in pneumothorax?
Communication created between pleural space and atmosphere
Air flows from atmosphere into pleural cavity until pleural pressure = atmospheric pressure
Pleural seal is lost
Lung collapses to unstretched size
What is hypoventilation?
Failure to breathe rapidly enough or deeply enough
What can cause hypoventilation?
Brain stem injury Spinal cord trauma Phrenic and intercostal nerve damage Neuromuscular junction damage Muscles of respiration impaired Chest wall impaired Pleural cavity damaged Poor lung compliance Upper airway obstruction High airway resistance
