respiratory physiology Flashcards
muscles used for inspiration
quiet breathing: external intercostals, diaphragm
forced inspiration: SCM, scalenes
expiration muscles
internal intercoastals, rectal abdominis, external/ internal oblique, transversus abdominis
i let the air out of my TIRES
is expiration active or passive
passive driven by chest wall recoil
active if increased minute ventilation (COPD)
what law is used in inspiration
boyles- contraction of inspiratory muscles reduces thoracic pressure and increases throacic volume
how do you prevent airway collapse
pressure inside airway (alveolar pressure) must be greater than pressure outside of the airway (intrapleulal pressure)
formula for transpulmonary pressure
transpulmonary pressure (TPP)= alveolar pressure- intrapleural pressure
during inspiration how does the pressure change
alveolar pressure becomes slightly neg (muscles of inspiration contract and inctrase volume, pressure decreases)
air flows in until pressure is = to atm pressure
end inspiration: alveolar pressure = atm pressure
how does pressure change with expiration
alevolar pressure becomes +
air flows out (down pressure gradient) back into atm
alevolar pressure= atm pressure at end expiration
what is tidal volume
amount of gas exhaled/ inhaled during a breath
normal vt
6-8 ml/kg
where does tidal volume go when you take a breath
only part of it goes to the respiratory zone- the remainer sits in conducting zone (dead space)
what is normal dead space in a healthy 70 kg pt
2 ml/kg
what does increased vd make more difficult
to eliminate expiratory gases from the lungs
it widens the paco2-etco2 gradient-> CO2 RETENTION
what is alveolar ventilation measuring
the minute ventilation avaliable for gas exchange (it removes dead space from the equation)
equations for minute ventilation and for alveolar ventilation
min ventilation= vt x rr
alveolar ventilation (vt- vd) x rr
does gas exchange occurr in dead space
no
what is anatomic dead space
air confined to conducting airways
(nose and mouth-> terminal bronchioles)
what is alveolar dead space
alevoli ventilated but not perfused
what is apparatus dead space
added by equipment (facemask, HME)
what is physiologic dead space
anatomic + alveolar dead space (varies)
some airway conditions that increase and decrease dead space (Vd)
increase: face mask, hme, ppv
decrease: ETT, LMA, trach
drugs that increase vd
anticholinergics (bronchodilation_)
age that increases vd
old age
neck position that increases or decreases vd
increases: extension- opens hypopharynx
decreases: flexion
pathophysiology that increases vd
increases: decreased CO, COPD, PE
surgical position that increases or decreases vd
increased: sitting
decreased: supine, t burg
where does dead space begin in circle system
begins at y piece
anything proximal to y piece does not influence dead space, nor does it increase length of circuit
exception: incompetent valve in the circle system
physiologic dead space can be calculated using what equation
bohr equation
compares partial pressure of co2 in the blood compared to partial pressure of co2 in exhaled gas
the greater the difference betwen the two, the greater amount of dead space
what is alveolar compliance
a change in alveolar volume for a given change in pressure
are all alveoli ventilated equal
no- due to gravitational force (transpulmonary pressure or TPP)
greater degree of volume change during a breath means what
better gas exchange
where are alveoli the largest
near the apex (higher TPP)
where are alveoli the smallest
near the base- lower TPP
where is ventilation greatest. why?
lung base- due to higher alveolar compliance- has greatest rate of volume change during a breath
where is perfusion greatest. why?
perfusion is greatest at lung base- due to gravity (when standing upright)
blood flow always follows..
ex if supine…
gravitational flow
ex: if supine perfusion will be greatest in posterior lungs
