Dynamic Mechanisms Flashcards
airflow =
(alveolar P - atm P) / airway resistance
why is alveolar P greater than atm P?
alveolar P is subject to pleural pressure applied around lungs and intrinsic static elastic recoil pressure of lungs
expiratory airflow can be low if–
low intrapleural P, low intrinsic static elastic recoil P, high resistance
low intrapleural pressure example
poor expiratory effort
low intrinsic static elastic recoil P example
low lung volume or disease
high airway resistance example
narrow airway as in asthma or bronchitis
what determines expiratory flow
lung elastic recoil
Does a forced expiratory maneuver in which pleural pressure becomes markedly positive increase expiratory flow?
not necessarily
• When the fall in intra-luminal pressure P is numerically equal to Pst(L), then the intra-luminal and extra-mural pressures will be equal.
equal pressure point
As the airway collapses, resistance – and intra-luminal pressure increases, causing the airway to open again
increases
Patients with emphysema are highly susceptible to airway collapse and increased expiratory effort is – at increasing airflow.
relatively ineffective
resistance
P/V dot (flow)
conductance
V dot (flow) / P
what disease is associated with decreased elastic recoil?
emphysema
what disease is associated with increased airway resistance?
chronic bronchitis
