Pulmonary Circulation Flashcards
(16 cards)
blood supply to the lungs:
* There are actually two blood supplies to the lungs
– the — and the — circulations
* The bronchial circulation is part of the — circulation
– arises from the —
* The bronchial vascular bed supplies — and — to the —- and —- of the lung
* It drains into —- and returns back to the —
– so pulmonary venous return is slightly — than cardiac output
– it is also why gas exchange will never be perfect
bronchial and pulmonary
systemic
aorta
oxygen and nutrients
smooth muscle and interstitial tissues
pulmonary veins
left ventricle
greater
- The pulmonary circulation transports — blood from — to the —
– and returns — blood to the — - Pulmonary circulation receives the — of cardiac output as right ventricular output must equal left
– ~4-6 l/min at rest and can increase to ~25 l/min in exercise - Though it receives the same volume of blood, the pulmonary circulation is a — pressure system
deoxygenated
right ventricles
alevolar capillaries
oxygenated blood
left atrium
the whole
less
pulmonary circulation is a – pressure system
* Right ventricular pressure 25/0 mmHg
* Pulmonary artery pressure 25/10 mmHg
* Pulmonary Pulse pressure 15 mmHg
– systolic - diastolic
* Mean Pulmonary pressure 15 mmHg
– diastolic + 1/3 pulse pressure
* Pulmonary capillary pressure ~6 mmHg
(range 6-10 mmHg)
* Left atrial pressure (LAP) ~ 2 mmHg
(range 2-6 mmHg)
- artery pulmonary is —- and the mean is —
- artery systemic is — and the mean —
low
25/8 mmhg
15 mmhg
120/80 mmhg
100 mmhg
measuring pulmonary pressure:
* Unlike systemic pressure, pulmonary pressure cannot be measure by —-
* Pulmonary capillary pressure is measured by — pressure
– is slightly higher than —-pressure
– used to estimate left atrial pressure
* — put through — side into branch of pulmonary artery
– it wedges at the pulmonary capillaries and — flow
plethysmography
capillary wedge
left arterial
catheter
right
stops
effect of gravity and volume:
* As lung expands during — , the extra-alveolar vessels are pulled —
– this distension means lung vascular resistance is — at high lung volumes
– and conversely vascular resistance is — at low lung volumes
* This is offset by the effect on capillaries where the opposite is true
* Capillaries are squashed as lung volume rises meaning that capillary resistance — as lung volume does
– and — as lung volume does
* So resistance varies across the respiratory cycle
inspiration
open
low
higher
rises
falls
effect of gravity on flow:
* Alveolar capillaries are — so they are distended by — yet compressed by —
* When standing, blood pressure is — above the cardiac level
– by approximately 0.74 mmHg/cm
* Given the height of the lung and its position relative to the heart, there is a difference in pressure between the — and the —
– the lung is ~30 cm in height, so this is ~22 mmHg of difference
– apex is -14 mmHg; base is +8 mmHg relative to cardiac level
* This difference gives — regions of —
– zone 1 (—) -14mmgf , zone 2 (—) and zone 3 (—) + 8 mmhg
thin
blood pressure
air pressure
reduced
base and apex
three
lung perfusion
apex , middle , base
Effect of Gravity on Flow
* Zone 1 ( — ): – flow
– in certain circumstances
* Normally there will be flow but if — > — then flow will —
* This can occur if…
– Pa — (e.g. — )
– PA — (e.g. — pressure ventilation)
* Zone 2 ( — ): — flow
* Systemically flow is due to the — difference
– Q = ΔP/R where ΔP = Pa - Pv
* Hydrostatic pressure — due to gravity mean Pa is — than PA but Pv ( venous) is not
– so ΔP here is — not —
* In exercise, increased pulmonary arterial pressure means — flow in —
* Zone 3 ( —): — flow
* At the base, hydrostatic pressure is —
* Both arterial and venous pressure —
alveolar pressure
* Flow is continuous throughout the cycle
apex
no flow
pA ( alveolar ) > pa ( arteriel )
cease
drops
hemaorrages
increases
+ve
middle
intermittent
arterial venous
increases
greater Pa-PA nottt Pa-Pv
contirnous
lungs
so basically in zone:
Zone 2: intermittent flow
Pa > PA > Pv
(Flow depends on aA gradient
not av gradient)
base
continuous
greatest
exceed
summary on gravity effect on flow:
Zone 1: – flow at —
(in certain circumstances)
P– > P– > P–
Zone 2: — flow at —
P– > P– > P–
(Flow depends on — gradient
not – gradient)
Zone 3: — flow at —
P– > P– > P–
no
apex
PA> Pa> Pv
intermittent
middle
pa> PA > Pv
aA not av
contirnous
base
pa > Pv > pA
pulmonary resistance:
* Pulmonary circuit receives the same — of blood
* Since it is low pressure, it must also be — resistance
– Q = ΔP ÷R so rearranging R = ΔP ÷Q
* Systemic circulation
– R = 100– 2 ÷ 6 = 98 ÷ 6 = 16.3 mmHg/L/min
* Pulmonary circulation
– R = 15 - 5 ÷ 6 = 10 ÷ 6 = 1.7 mmHg/L/min (about 10x lower)
* The pulmonary circulation can take larger cardiac output without — resistance or pressure
* Pulmonary blood volume is approximately —
* Volume can increase to some extent without a change in — or — due to the — and –
volume
low
increasing
500 ml
pressure or resistance
capillary recruitment and distension
- Pulmonary blood volume is approximately—
- Volume can increase to some extent without a change in pressure orresistance
– due to the—- and — - In — heart failure pulmonary volume increases
– pulmonary — - In conditions of SNS activation up to — of the pulmonary volume can move to systemic circulation
– sympathetic constriction — capacitance
500 ml
capillary recruitment and distension
left
pulmonary congestion
50%
decreases
control of pulmonary resistance:
* Relatively — neural/hormonal influence
– there is SNS and PNS innervation, but role is questionable
* Little or no — or — effect as in other beds
– other than the recruitment and distension
* — is hugely important factor and pulmonary circulation behaves differently to systemic arteries
– in systemic arteries there is adenosine-related —
* In pulmonary circulation, hypoxia leads to —
– hypoxic pulmonary vasoconstriction
low
myogenic or metabolic
oxygen
vasodilatation
vasoconstriction
hypoxic pulmonary constriction:
* Pulmonary arteries constrict to —
– this is an — mechanism
* This response controls —
– shunting blood — from poorly — areas
– matching ventilation (V) and perfusion (Q)
* An important factor in hypoxic diseases:
– — / — altitude cause hypoxic pulmonary vasoconstriction
– ultimately leads — and —
– may eventually lead to — heart failure
hypoxia
intrinsic
capillary perfusion
away
ventilated
COPD/ high
pulmonary hypertension and oedema
right heart failure
Pulmonary Oedema
* As with the systemic circulation, this relates to the Starling forces
* However, values in the lung are quite different
– due to the — pressure nature of the circulation
* Hydrostatic pressures:
– low pressure means — pressure is low: – mmHg
– lymphatic pumping mean interstitial pressure lower: — mmHg
* Colloid Osmotic pressures
– leaky capillaries allow more colloid in — : — mmHg
– plasma colloid about the same as systemic circulation:— mmHg
Capillary Dynamics - Normal
* Net filtration pressure = (Pc− Pi)− σ(πc− πi)
low
capillary
6
-8
intertitium
15 mmhg
26
pls check slide 27
Pulmonary Oedema
* Fluid in the — leaves by one of two mechanisms
– before being carried away be —
* Active pumping of — creating an — gradient or the —- pressure sucks it out
* As with peripheral oedema, an imbalance in —- or failure to clear — leads to oedema
* Interstitial oedema increases the diffusion — for O2 and decreases —-
– if there is—- interstitial fluid pressure, fluid crosses alveolar membranes giving alveolar oedema
– potentially fatal due to —
alveoli
lymphatics
Na+
osmotic gradient ot -ve interstitial pressure
starling forces
clear fluid
diffusion time
lung compliance
+ve
suffocation
Pulmonary Oedema
* Major causes of pulmonary oedema are:
1- Rises in pulmonary —:
– — heart failure leads to failure of the — and —
increasing capillary pressure
– — altitude causes hypoxic pulmonary vasoconstriction leading to HAPE
– in chronic conditions lymphatics can — to compensate
2- Increases in pulmonary — :
– damage to the capillary in conditions like —-
– damage leads to — and a decrease in the—- osmotic pressure holding fluid in the capillary
capillary pressure
left
circulation and pulmonary congestion
high
expand
capillary permeability
pneumonia
leakiness
colloid pressure
summary:
* The pulmonary circulation is a — pressure, — resistance system
* There is limited — control and resistance is controlled by —
* Pulmonary arteries constrict to —
–> matches — with —
–> cause of morbidity in pulmonary disease
* Changes in Starling forces leads to —
low
low
extrinsic
local facotrs
hypoxia
perfusion w ventilation
pulmonary oedema
