Resistance to breathing Flashcards
Describe the sources of resistances to airflow in the respiratory system
Mechanical - elastic forces in the parenchyma
Surface tension
Airway - Airflow changes
What are the factors that influence rate of airflow
Elastin and collagen for expiration. Opposing force = recoil a major resistance to lung inflation
What is Laplace’s law
Larger the radius the larger the wall tension needed to withstand internal pressure
What is surfactant
Produced and secreted by alveolar type II penumocytes
Acts as a detergent and breaks the molecular bonds between air and liquid
What is surface tension
Property of a liquid which minimises the area of the liquid at a liquid-gas interface. An inward directed force reducing compliance
Force attracts water
Igf not impeded it will collapse alveoli and fill them with fluid causing more forces to open them during inspiration
What is Neonatal respiratory distress syndrome (NRDS)
Caused by lack of surfactant which is first detected om the fatal lung at 24 weeks gestation and rapidly increases after the 30th week.
Believed to be genetic due to inherited variations of surfactant A & B.
Use artificial ventilation to spare the infant excessive work of breathing against stiff lungs.
What is airway resistance
Result of frictional forces opposing air flow.
In conducting zone, flow of air is laminal (streamlined). When airway narrows there’s turbulence and noise
What is Poiseuille’s law
Resistance is inversely related to radius.
What is bronchomotor tone and explain the factors that change bronchomotor tone
At rest, parasympathetic activity provides bronchomotor tone a low level of bronchial smooth muscle activity. Nerve endings that release acetylcholine cause bronchoconstricition.
Triggers include respiratory disease, raised pressure on bronchi, excess mucus, inflammation due to histamine
