Physiological Consequences of Disruption or Destruction of Flashcards
What is type 1 respiratory failure?
Respiratory failure due to gas exchange abnormality - leads to a fall in PaO2 - as gas exchange worsens ventilation increases which partially improves PaO2 but also leads to low PaCO2
What is type 2 respiratory failure?
Respiratory failure due to inadequate ventilation - leads to low PaO2 (50mmHg)
How does type 1 respiratory failure lead to type 2 respiratory failure?
If respiratory muscles become fatigued and so can no longer hyperventilate
What is the surface area of the alveolar capillary membrane?
75 square metres
What processes and diseases can effect the alveolar-capillary membrane?
inflammation, infection, fibrosis, emphysema, fluid, cancer
What are the physiological effects of disruption the AC membrane?
Diffusion impairment for oxygen (not usually for CO2), difficult for lung mechanics and if enough of the lung is effected may lead to increased pulmonary artery pressure
What are the causes for low PaO2?
Low PiO2, low ventilation, abnormal gas exchange (either low V/Q, shunt or diffusion impairment)
How can you determine the cause for low PaO2?
The A-a gradient will be wider if there is abnormal gas exchange
What are the mechanical effects on the lung of a restrictive lung disease?
breathlessness, increased elastic WOB, reduced lung volumes, altered pattern of breathing, reduced maximum ventilation
What is the effect on compliance for restrictive lung diseases?
Reduced compliance
What is the usual pattern of breathing in restrictive lung diseases?
small breaths and a fast rate
What is the result of reduced compliance on lung volumes?
Will cause reduced lung volumes - TLC, RV, FRC, VC, FEV1, FVC
What is the FEV1/FVC in restrictive lung disease?
Normal - because both FEV1 and FVC are reduced
What influences compliance of the lungs?
tissue composition and surface tension in the alveoli
What is compliance?
Change in volume/change in pressure
What is the normal relationship between pressure and volume?
Initial expansion of the lung doesn’t require much pressure but as you get closer to the TLC you need to generate a lot of negative pressure
What happens to lung compliance in pulmonary fibrosis?
Decreased lung compliance - need a lot of pressure to generate any change in volume
What happens to lung compliance in emphysema?
Increased lung compliance - need very little change in pressure to generate change in volume
What is the maximum ventilation in restrictive lung disease?
Reduced (35 x FEV1) because FEV1 is reduced
Does the reduced maximum ventilation effect ability to exercise?
Yes, but exercise is usually more limited by hypoxia and or pulmonary hypertension which both worsen with exercise
