Mech Properties Of Lung And Chest Wall Flashcards
Alveolar pressure
Slight negative before inhale
Slight positive before exhale
Intrapleural pressure
Negative during normal breathing and max inhale
Compliance
Is a consequence of the distensibility of the lung
It is inversely proportional to recoil- the lungs ability to resist distention
Increases around FRC, decreases around TLC & RV
Alveolar surface tension
Accounts for close to 50% of the recoil forces of the lung
Surfactant
Released by type II pneumocytes
Lowers the surface tension on the alveoli effectively reducing recoil forces that try to collapse the alveoli and increasing lung compliance
Respiratory system compliance
Combination of lung and chest wall compliances
Lungs and chest wall have greater fnxnl range when they work as a unit
Airway resistance and lung volume
Resistance decreases with increased volume
Pt with increased airway resistance breath at a higher volume effectively at a higher FRC
Neurohormone causes of dilation of airways
Sympathetic B2 AR, B2 agonists
NO
Increased small airway PCO2
Decreased sm airway PO2
Neurohormone causes of constriction of airways
Parasympathetic stimulation Ach Histamine Serotonin Decreased PCO2 in sm airways
Dynamic vs static compliance
For normal breathing dyn comp is about the same as stat comp
During exercise dyn > stat
In pt w/ fast shallow breathing where airway resistance is increased dyn<stat
Work of breathing
=pressure x change in pressure
Elastic component
Elastic recoil forces of the chest wall and lung and the alv surf tens
Resistive component- overcoming resistance of airways
Work of breathing in relation to resp rate
Increased elastic resistance (recoil force) causes an increase in RR
Increased airway resistance causes a decrease in respiratory rate
This compensation accounts for inability to apples recoil and slowness of filling respectively
