Mechanics of Ventilation Flashcards
define and contrast minute ventilation and alveolar ventilation
minute ventilation: volume of air that enters the lungs per minute (tidal volume x respiratory rate)
alveolar respiration: volume of air entering or leaving the alveoli with each breath; air involved directly in gas exchange;
have to subtract dead space from minute ventilation to account for the volume of ventilated air in the resp tract that does not directly participate in gas exchange to calculate
define and contrast the different pulmonary dead spaces, both anatomic and physiologic
physiologic dead space = anatomical and alveolar dead spaces
anatomic dead space: air in the oronasal zone and conducting zone (no participate in gas exchange)
alveolar dead space: alveoli that are ventilated but not perfused so don’t participate in gas exchange; found only in the respiratory zone and should be minimal in healthy animals
what is tidal volume?
the volume of inhalation + passive expiration (resting); the average air inhaled and exhaled per breath at resting
also equal to volume of dead space plus volume of alveolar ventilation (air breathed and air used at rest = tidal volume)
VT = VD + VA
what is functional residual capacity?
the volume remaining in the lungs after a normal, passive exhalation; thanks to opposing inner recoil forces of lungs and outer recoil forces of chest wall
expiratory reserve volume (forced exhale volume) + residual volume (air left in lungs after forced exhale, needed for ventilation, cannot breathe out unless dead)
FRC = ERV + RV
what is inspiratory reserve volume?
the biggest inhale volume of air
what are the 4 lung volumes?
- tidal volume: normal respiration
- inspiratory reserve volume
- expiratory reserve volume
- residual volume
list and describe the 4 lung capacities
- inspiratory capacity: all the air that can be inhaled (passive plus forced)
- vital capacity: all inhale plus expiratory reserve volume, all air that can be inhaled or exhaled without being dead
- total lung capacity: all air that can be inhaled and exhaled (including residual volume(
- functional residual capacity: ERV + RV
describe how the parietal and visceral pleura in the thorax interact to create the negative pressure within the intrapleural space
- the intrapleural space is a potential space (don’t want it to be a huge space)
- contains a small serous-like pleural fluid that reduces friction and
- generates its own force due to the polarity of its water content wanting to pull the wet surfaces of the two pleura together, but the opposing forces of the lungs trying to pull inward from the chest wall (due to elasticity and surfactant surface tension) and the chest wall trying to pull outward due to the ribcage and chest wall muscles
- keeps the pleura stuck together by creating negative pressure/suction between the two pleura = good and can breathe!
describe the effects of air or fluid accumulating in the intrapleural space
this would destroy the negative pressure suction of the pleural fluid and cavity and it would become incredibly hard to breathe as intrapleural pressure is usually negative relative to the atmosphere (so air flows in) but if that gradient doesn’t exist = no breathe
give the sequence of events that occurs during inspiration (5)
- inspiratory muscles contract (diaphragm down, rib cage out and up)
- thoracic cavity volume increases
- lungs are stretched so intrapulmonary volume increases
- intrapulmonary pressure drops
- air flows into the lungs down its pressure gradient until intrapulmonary pressure is equal to atmospheric pressure again
give the sequence of event that happen during expiration (5)
- inspiratory muscles relax (diaphragm rises, rib cage descends due to recoil of costal cartilages)
- thoracic cavity volume decreases
- elastic lungs recoil passively, intrapulmonary volume decreases
- intrapulmonary pressure rises
- air flows out of lungs down its pressure gradient until intrapulmonary pressure is equal to atmospheric pressure
