intro and inspiration Flashcards
PO2 at rest
100 +/- 2 mmHg
PCO2 at rest
40 +/- 2 mmHg
volume of O2 per min at rest
approx 250ml/min O2
max is 5l
volume of CO2 per min at rest
approx 200ml/min CO2
max is 6l
what is ventilation at rest?
approx 6l/min
12-16 breaths
what is cardiac output at rest?
approx 5l/min
70bpm
what is the maximum ventilation value?
160l/min
40 breaths
what is the maximum cardiac output value?
25l/min
200bpm
what is the blood air barrier?
blood vessel to alveolus
- capillary endothelium basement membrane
- interstitial space
- basement membrane of alveolus fused
- alveolar epithelium
what is physiological dead space?
total volume of gas in each breath that does noe participate in gas exchange
e.g. ventilated but not perfused
what is the Neurovascular bundle in the thorax?
intercostal vein
intercostal artery
intercostal nerve
VAN
what is respiratory epithelium?
ciliated pseudostartified columnar epithelium
with mucous
what is Boyle’s Law?
P1V1 = P2V2
INVERSE RELATIONSHIP
increase in pressure, decrease in ventilation
increase in ventilation, decrease in pressure
what are the 4 layers that are involved in respiratory gas exchange?
visceral pleura
pleura cavity (parietal space)
parietal pleura
parietal wall
chest wall
are the visceral and parietal pleura connected?
visceral and parietal pleura are tethered together
what is in the pleura cavity? (parietal space)
pleura cavity is filled with serous pleura fluid
to reduce friction, inflammation and tissue damage
what is pleurisy?
inflammation of the pleura
- the membrane that lines the lungs within the chest cavity
can be associated with:
- an accumulation of fluid in the space between the lungs and chest wall (called a pleural effusion)
- it can be dry pleurisy, which has no fluid accumulation.
what are the pressures involved in respiratory gas exchange?
intrapulmonary / intra-alveolar pressure (Ppul)
intrapleural pressure (Pip)
atmospheric / barometric pressure (Patm)
what is intrapulmonary / intra-alveolar pressure?
pressure inside the alveoli
Ppul = 760mmHg
what is intrapleural pressure?
pressure inside the thoracic cavity
Pip = 756mmHg
what is atmospheric / barometric pressure?
pressure exerted by the weight of the atmosphere (outside of body and lungs)
Patm = 760mmHg
at sea level
what do all pressures get compared to?
the atmospheric pressure
Patm = 760 mmHg = 0
so what is intrapulmonary pressure compared to atmospheric pressure?
Ppul = 760 mmHg Patm = 760 mmHg
therefore, Ppul = 0 as equal to Patm (Ppul - Patm)
ZERO PRESSURE
what is intrapleural pressure compared to atmospheric pressure?
Pip = 756 mmHg Patm = 760 mmHg
therefore, Pip = -4 mmHg as it is less than Patm (Pip - Patm)
NEGATIVE PRESSURE
what is Ppul?
intrapulmonary pressure
760mmHg
ZERO PRESSURE
what is Pip?
intrapleural pressure
756mmHg
NEGATIVE PRESSURE
what is Patm?
atmospheric / barometric pressure
760 mmHg
compare other pressures to this
3 factors that make intrapleural pressure negative
elasticity of lungs
- collapsing
surface tension
- collapsing
elasticity of chest walls
- expand chest wall
ATTEMPTING TO INCREASE THORACIC CAVITY VOLUME
- lowering Pip
what is elasticity?
want to recoil when stretched
what is gravity’s impact on pressures in gas exchange?
pulls apex of lung down, pulling visceral pleura from parietal pleura
- decreasing volume so increasing pressure at bottom of intrapleural cavity
- increasing volume at top so decreasing pressure in intrapleural cavity
what is transpulmonay pressure?
TP is the difference between the alveolar pressure and the intrapleural pressure in the pleural cavity.
= intrapulmonary pressure - intrapleural pressure
= Ppul - Pip
= 0mmHg - (-4 mmHg)
= 4 mmHg
positive value
so able to inflate
- During human ventilation, air flows because of pressure gradients
what is transthoracic pressure?
TTP is the difference between the pressure in the pleural space and the pressure at the body surface,
represents the total pressure required to expand or contract the lungs and chest wall
= Pip - Patm = (-4 mmHg) - 0 mmHg = -4 mmHg negative - tries to deflate
what is transrespiratory pressure?
pressure difference between the airway opening and the body surface
used to describe the pressure required to inflate the lungs and the airways during PPV
= Ppul - Patm
what is the diaphragm innervated by?
phrenic nerve
what are the roots of the phrenic nerve?
C3, 4, 5
keeps the diaphragm alive
what are the external intercostals innervated by?
intercostal nerve
what are the roots of the intercostal nerve?
T1 - T11
what stimulates the the phrenic and intercostal nerve?
stimulated by cortical control and ventral respiratory group (VRG)
- nuclei in the medulla
what is the effect of action potentials on external intercostals?
APs cause the external intercostals to contract
pull ribs outwards
- increases the thoracic cavity volume
- bucket handle movement
sternum pulled out and upwards
- increases the thoracic cavity volume
- pump handle movement
what is the bucket handle movement?
APs causing the external intercostals to contract and pull the ribs outwards
what is the pup handle movement?
APs cause the sternum to be pulled outward and upwards
what is the effect of action potentials on the diaphragm?
APs cause the diaphragm to dome downwards
- increasing the thoracic volume greatly
what are the 3 mechanisms that increase thoracic volume in quiet breathing?
diaphragm domed downwards by phrenic nerve innervation
ribs pulled outwards by external intercostals
sternum pulled up and outwards by external intercostals
what is the effect of increase thoracic volume on pleura?
parietal pleura in pulled
visceral pleura is pulled with it
tethered together
what is the effect on increased thoracic volume on pressures?
increased thoracic volume decreases pressure
in inspiration:
Ppul drops to -1mmHg
Pip drops to -6mmHg
Patm should not be effected
what is Ppul in inspiration?
-1mmHg
dropped from 0
what is Pip in inspiration?
-6mmHg
dropped from -4mmHg
what is transpulmonary pressure in inspiration?
Ppul - Pip
(-1mmHg) - (-6mmHg)
= + 5mmHg
positive so able to inflate
what is transthoracic pressure in inspiration?
Pip - Patm
(-6mmHg) - 0
= - 6mmHg
negative
chest wall want to recoil outwards
- pulling on it so helping to increase volume
what is transrespiratoty pressure during inspiration?
Ppul - Patm
(-1mmHg) - 0
= -1mmHg
negative
so air can flow into lungs alveoli (high to low pressure)
- continues to flow into Ppul=Patm at peak inspiration
what occurs in quiet inspiration?
- external intercostals and diaphragm contract
(innervated by intercostal nerves and phrenic nerve)
2.
increase in thoracic cavity volume
3. intra pulmonary pressure (Ppul) decreases to -1mmHg intrapleura pressure (Pip) decreases to -6mmHg
- Transpulmonary pressure TP in positive (+5mmHg)
- lungs able to inflate
Transthroacic pressure TTP is negative (-6mmHg)
- outward elastic recoil of chest walls aids increase in volume
Transrespiratory pressure TRP is negative (-1mmHg)
- air flows into alveoli from environment
what is different about forced inspiration compared to quiet?
requires additional muscles
what additional muscles are needed in forced inspiration?
sternocleidomastoid
- elevates sternum
scalene
- anterior, middle and posterior
- pulls ribs
pectoralis minor
- pulls ribs
what do the additional muscles in forced respiration all help to do?
increase thoracic cavity volume more
so greater decreases in pressure
Ppul = -2mmHg Pip = -7mmHg
so larger volume of air can flow into lungs as takes more time for Ppul=Patm
when does air stop flowing into lungs?
what Ppul increases to equal Patm
at peak inspiration
Ppul=Patm
- air stops flowing into alveoli
