Lecture 18 - Mechanics of Breathing Flashcards
Name and define the 3 steps of respiration
Pulmonary ventilation (insp/exh of air between atm and lungs)
Pulmonary/external respiration (exchange of gases - alveoli <-> blood)
Tissue/internal respiration (exchange of gases - blood in systemic capillaries <-> tissues)
State Boyle’s Law
When temperature is constant, the pressure of a gas varies inversely with volume
What is a good benchmark for atmospheric pressure in most places?
760 mmHg
What is intrapleural pressure and how is it formed?
The pressure within the pleural cavity - it exists due to the elastic recoil of the lungs
How does intrapleural pressure compare to atmospheric and intrapulmonary?
It is always lower than both
Define pulmonary compliance
The ease with which the lungs can be expanded
Which 3 factors affect compliance?
Elasticity of lung connective tissue
Mobility of the Chest/Thoracic Wall
Surface tension
What is the equation for compliance?
Compliance = (Delta) Volume / (Delta) Pressure
State Laplace’s Law
P (pressure) = 2T (tension) / r (radius of alveoli)
What 3 things does surfactant achieve?
Reduces surface tension, increases compliance and equalises pressure differences between small and large alveoli
What issue related to surface tension can premature babies experience?
Neonatal Respiratory Distress Syndrome (not enough surfactant produced yet, reduced compliance, difficult to inflate lungs)
What two factors affect airway resistance?
Lung volume (bronchi dilate as lungs expand)
Bronchial smooth muscle (PSNS -> bronchoconstriction, SNS + Adrenaline -> bronchodilation)
Name 2 simple methods of assessing lung function
Breath Sounds
Peak flow meter (measures the max speed at which you can breath out)
What is the name of the piece of equipment used for measuring inspiratory and expiratory volumes?
Spirometer
Define Tidal Volume (+ Normal M+F Values)
The volume of air inhaled or exhaled in one quiet breath (500ml both)
Define Expiratory Reserve Volume (+NMFV)
The volume of air that CAN be exhaled AFTER a normal tidal volume exhalation (1000ml, 700ml)
Define Inspiratory Reserve Volume (+NMFV)
The volume of air that CAN be inhaled AFTER a normal tidal volume inhalation (3300ml, 1900ml)
Define Residual Volume (+NMFV)
The volume of air remaining in the lungs AFTER maximum expiration (1200ml, 1100ml)
Define Vital Capacity (+NMFV +Calc)
The maximum volume of air that can be expired after a maximum inspiratory effort, VC = TV + IRV + ERV (4800ml, 4200ml)
Define Inspiratory Capacity (+Calc)
Maximum volume of air that can be inspired after a normal expiration, IC = TV + IRV
Define Functional Residual Capacity (+Calc)
The volume of air remaining in the lungs after a normal expiration, FRC = RV + ERV
Define Total Lung Capacity (+NMFV +Calc)
The maximum volume of air contained in the lungs after a maximum inspiratory effort, TLC = TV + IRV + ERV + RV (6000ml, 4200ml)
Formula for Pulmonary Ventilation Rate (Respiratory Minute Volume)?
PVR = Respiratory Rate (no. of breaths per min) x Tidal Volume (vol. of air moved per breath)
Define Alveolar Ventilation (as opposed to Pulmonary Ventilation) and name the reason for the difference
The volume of air Reaching The Alveoli (per minute) -> Anatomical Dead Space
