Respiratory Physiology Flashcards
what parts of ventilation are active and which are passive?
- inspiration: active (muscles contract)
- expiration: passive (muscles relax) unless under stress
TV
Tidal volume
air that moves into the lung with each quiet inspiration
normal ~500 mL
RV
residual volume
air in lung after MAX expiration
cannot be measured by spirometry
IRV
inspiratory reserve volume
air that can still be inhaled after normal inspiration
ERV
expiratory reserve volume
air that can still be exhaled after normal expiration
IC
inspiratory capacity
IRV + TV
air that can be inhaled after normal exhalation
FRC
functional residual capacity
RV + ERV
vol of gas in lungs after normal expiration
cant measure w spirometry bc includes RV
VC
vital capacity
IRV + TV + ERV
max vol of gas that can be expired after max inspiration
TLC
total lung capacity
volume of gas present in lungs after max inspiration
minute ventilation
total vol of gas entering the lungs per min
= TV x RR
alveolar ventilation
vol of gas that reaches alveoli each min
(TV-phys dead space) x RR
what is physiologic dead space (VD)
anatomic dead space + alveolar/functional dead space (usually = anatomic dead space)
dead space = no gas exchange, no pulmonary blood flow
elastic recoil
- the lungs intrinsic nature to deflate with expiration
- tendency for lungs to collapse in and chest wall to spring out at physiologic baseline (opp motions balance and prevent lung collapse)
pulmonary pressures at FRC
- airway and alveolar pressures equal atmospheric pressure (zero)
- intrapleural pressure is neg
compliance def and factors that affect it
change in lung vol for a change in pressure; inc compliance = lung easier to fill
inversely proportional to wall stiffness (inc compliance, dec stiffness)
inc by surfactant
how does CO2 get to the lungs?
CO2 enters RBC from tissue and is convertred into 3 forms where it is transported to the lungs, from most to least:
- converted into bicarb (via carbonic anhydrase; bicarb/chloride transport on RBC membrane)
- carbamino hemaglobin (bound to deoxy N-terminus, not heme)
- dissolved in plasma
what triggers the release of CO2?
oxygenation of hemoglobin promotes dissociation of H from hemoglobin >
shifts equilibrium toward CO2 formation >
releases CO2 from RBCs (haldane effect)
pulmonary circulation
- low resistance, high compliance system
- oxygen diffuses slowly across alveolar membrane
- carbon dioxide diffuses rapidly
pulmonary diffusion increases with:
- increased area
- larger difference between partial pressures
pulmonary diffusion decreases with:
- decreased area
- less difference between partial pressures
- thicker alveolar wall
pulmonary vascular resistance decreases with:
- inc CO
- inc vessel radius (vasodilation)
- dec arterial pressure
- dec blood viscosity
- dec vessel length
- alkalosis
- anemia
pulmonary vascular resistance equation
pul artery pressure - pul artery occlusion pressure
/
CO
pulmonary vascular resistance increases with:
- acidosis
- hypoxia
- hypothermia
- sympathetic stim
V/Q ratio in various lung zones and common associated conditions
ventilation perfusion ratio
Zone 1 (apex of lung): V/Q ratio INC
- ventilation dec, but perfusion dec more
- TB
Zone 2 (middle): V/Q = 1
Zone 3 (base): V/Q ratio DEC
- ventilation inc, but perfusion inc more
- immune conditions, COPD
what are the main components of alveolar gas exchange?
- SA
- PP gradients of gases
- matching of ventilation and perfusion
what are some of the controls of ventilation and perfusion?
- central chemoreceptors
- cerebral cortex
- pontine respiratory centers
- peripheral chemoreceptors
- pulmonary inputs (stretch, irritant, J receptors)
all > medullary respiratory centers > lung movement
how is CO2 and O2 status in the body measured?
- chemoreceptors on the surface of the medulla detect pH changes in the CSF
- peripheral chemoreceptors (on carotid and aortic bodies) detect pH/Co2/O2 changes in blood and transmit signal via vagus and glossopharyngeal nerves
CNS and ventilation control
- signals sent from chemoreceptors fed to respiratory center in brain stem where there are inspiratory and expiratory neurons (expiratory for deep expiration only)
medulla has three respiratory control centers:
- dorsal resp group (inspiration)
- ventral resp group (expiration)
- pre-botzinger complex (intrinsic rhythm generator)
they interact w pons at pneumotaxic center and apneustic center (inhibits or stim inspiration)
mechanoreceptors in the lungs
assess mechanical status of lungs via vagus nerve
stretch receptors activated when lungs excessively inflated
- triggers inspiration reflex; stops inspiration and prolongs expiration
fibers synapse in cervical and thoracic spine and synapse with motor neurons
- phrenic nerves: diaphragm
- intercostal nerves: intercostal muscles
pain, emotion, and voluntary control
- limbic and hypothalamus send info to respiratory center
- voluntary control from primary motor cortex > communicates directly to spinal cord, bypassing info from brainstem
