Pulmonary Ventilation and Pulmonary circulation

1. PULMONARY VENTILATION
AND
PULMONARY CIRCULATION
Dr. Sanjeev Shrivastava
05/01/2019
09:00 AM to 10.00 AM

2. • Pulmonary ventilation
• Alveolar ventilation
• Dead space
types of dead space
measurement of dead space
• Ventilation Perfusion ratio
• Effect of gravity on ventilation perfusion ratio
• Pulmonary circulation
• Bronchial circulation
• Functions of pulmonary circulation

3. Pulmonary ventilation
• Volume of air that enters lungs each minute.
• Product of TV and RR.
• = 500x 12
=6 L/min
Range = 5 L to 10 L/min

4. The rate of alveolar ventilation
Alveolar ventilation per minute is the total volume of
new air entering the alveoli and other adjacent gas
exchange areas each minute.
Va = Respiratory rate X (Vt – Vd)
= Respiratory rate X (Vtidal volume – Vdead space)
= 12 X (500 – 150) = 4200ml

5. Effect of rate & tidal volume on ALVEOLAR VENTILATION
VT R VE VA
ml/min ml/min
200 30 6000 0 no alveolar ventilation
500 12 6000 4200 normal ventilation
1000 6 6000 5100 excess ventilation
VA = (VT - VD) RR
= ( 500 - 150)x 12
= 4200ml
Fixed VE&
VD

6. Dead space
• volume of air in airways that can not
exchange gases with blood .
• Occupies the conducting zone.
• typical value about 150 ml or 1 ml per
pound body weight.
• Ratio of dead space volume to tidal
volume in normal health is 25% - 30%.

7. DEAD SPACEVD
7
Physiological Dead space (volume)
sum of anatomical and alveolar dead space
Anatomical Dead Space (volume)
volume of air in airways that can not exchange
gases with blood - typical value about 150 ml
or 1 ml per pound body weight.
Alveolar Dead Space (volume)
volume of alveoli that are ventilated but do
not receive a blood flow and thus no gas exchange. Small
in normal lung but can be very large in some pulmonary
diseases.

8. Measurement of anatomical dead space
• 1- Single breath oxygen technique/Single breath N2
washout method- calculate the anatomical dead space
area A x VE
VD= ----------------------------
Area A + Area B

9. Measurement of physiological dead space
• Bohr’s equation - by determining CO2 conc in expired
and alveolar gas.
• Based on the fact that inspired air contains negligible
CO2. All the CO2 in expired air is derived from the
functional alveoli.
• VD= (PaCO2 – PECO2) x VE
PaCO2

10. Pulmonary Circulation

11. Three Types of circulations
• Pulmonary artery - Pulmonary trunk divides into Rt n Lt pulmonary
arteries.
• Bronchial artery (2 left 1 Right)- Two left and one right
-From descending thorasic aorta
-Contributes to a physiological shunt
-1 to 2 % of COP.
• Lymphatic circulation – present in walls of terminal bronchioles n
• in all supportive tissue. Perticulate matter
entering the alveoli during inspiration is removed by lymphatics.
• Remove the plasma proteins leaking from capilarries and help to
prevent the pulmonary oedema.

12. LUNG RECEIVES 2 BLOOD SUPPLIES
From the Left
Ventricle
BRONCHIAL
ARTERIES
Carry oxygenated blood
Blood supplied to
the conducting
airways, lung
interstitium & tissue.
From the Right
ventricle
PULMONARY
ARTERIES
Carry deoxygenated mixed -
venous blood
Blood circulates the
alveoli to get
oxygenated.

13. Pulmonary Arterial Circulation

15. General Characters
• Thin walled , distensible , large compliance
• Low pressure , low resistance , high capacitance system
• Pul capillaries are larger and have more anastamosis
• Helps in gas exchange
• Serves as a filter
• Metabolic functuions
• Serves as a blood reservoir

16. Comparison of the Pulmonary & Systemic
Circulation
PULMONARY
CIRCULATION
• LOW PRESSURE
- because it only needs to pump blood to the top of
the lungs.
- if it is HI pressure, then following Starling forces,
the fluid would flood the lungs.
• LOW RESISTANCE
- only 1/10th of the resistance of the systemic circ.
- arterioles have less smooth muscle, veins are
wider & shorter & pulmonary vessel walls are thinner.
• HIGH COMPLIANCE
- accommodates 5 L of blood (same as the
systemic circulation)
- Accommodates shifts of blood more quickly e.g.
when a person shifts from a standing to a lying
position
SYSTEMIC
CIRCULATION
• HIGH PRESSURE
- B/c it needs to send blood
to the brain even when standing
& to the tip of en elevated
fingertip.
• HIGH RESISTANCE
- because of increased
smooth muscle in the
arterioles & the metarterioles.
• LOW COMPLIANCE
- because of resistance
offered by the arterioles and
the metarterioles.

17. Advantages of Pulmonary
Circulation being a Low Resistance
system:
1. Accommodates more blood as a person shifts
from the standing to the lying position.
2. High compliance allows the vessel to dilate in
response to modest increase in Pulmonary arterial
pressure.
3. Pulse pressure in the pulmonary circulation is
rather low.

18. Pressures in pulmonary system
Pressure Pulmonary system Systemic vasculature
Ventricular pressure RV- 25 (systolic) LV- 120 systolic
Pulmonary artery 25 sys
8 diastolic
120 sys
80 dias
MAP 15 mm/hg 100
Pulse pressure 17 40
atrial pressure LA – 5 RA - 0
Pressure gradient Pp= MAP- MVP= 15-5 =10 100

19. Pulmonary Capillary Pressure
• Mean value is 10 mmHg
• Is less than colloid osmotic pressure 25mmHg
• So a net suction force of 15mmHg is keeping the
alveoli dry
• However if hydrostatic pressure raises more than
25mmHg then pulmonary edema ensures e.g.
exercise, high altitude, left heart failure.
• Layer of fluid increases the distance b/w blood and
gases in alveoli. This reduces rate of gas exchange in
lungs

20. Pulmonary Blood Flow
• Vessels contain 600 ml of blood at rest (200-900)
• Decreases in standing and haemorrhage according to
posture and pathological conditions
• Act as a reservoir
• Increase in lying position, mitral stenosis MR n Lt
heart failure.

21. Pulmonary Capillary Wedge Pressure
• Is measured to give the LAP
• Direct measurement of LAP is difficult
• So indirect measurement is done
• LAP corresponds to PCWP
• Measures by swans gans catheter
• Catheter is wedged in the tip of the small branch of
pulmonary artery
• Stops flow of blood in that

23. Swans Gans Catheter

24. Regional Distribution Of Pulmonary
Blood
• Pulmonary bld flow same as the CO or LV output
• Effect of gravity :-
• in supine position MAP is same all over the lungs so uniform
perfusion
• Gravity changes the hydrostatic pressure
• Zero reference plane is at the level of RA which is at the
middle of the lung in the region of hilum.
• Which is approximately at the middle of the lung or hilum

25. At Standing Position
• In a 30cm height lung
• In the middle pressure is 15mmHg
• In the apex its 11 mmHg less ie 4mmHg
• In the base its 26mmHg

26. Perfusion Zones Of Lungs
• Depends upon three pressure
• PA - alveolar pressure
• Pa – pulmonary arterial pressure
• Pv – pulmonary venous pressure
• Divided into three zones in erect posture – 1, 2, 3

27. The Zones of the Lung and the
Difference in Regional Blood Flow
ZONE 1:
No blood flow during
all portions of the
cardiac cycle
• Pulmonary capillary
pressure never rises
higher than the
alveolar air pressure
, so the capillaries
are crushed and the
blood flow is greatly
reduced!
ZONE 2:
Intermittent blood
flow
• Intermittent blood
flow during the
systolic phase of the
cardiac cycle as then
only do the PA and
PV rise higher than
the Pa, so arterial end
dilated and open
during the systole.
ZONE 3:
Continuous blood
flow
• PA & PV are much
higher than Pa, so the
vessels dilated
throughout the
cardiac cycle and
blood flow at its
maximum.

28. ZONES OF THE LUNGS

29. Zone 1
• Area of zero perfusion
• Does not exist in normal lungs
• Occurs when Pul arterial pressure becomes less than
alveolar pressure
• Pulmonary capillaries become collapsed
• Flow becomes zero
• Ex- pulmonary embolism , shock , obstructive lung
diseases ,

30. Zone 2
• Region of intermittent blood flow
• This occurs during systole when the pul arterial pressure
raises more than PA
• In normal lungs this zone occurs from apex to hilum of the
lungs
• Systolic Pa pressure is 25 mmHg and diastolic is 8 mmHg

31. Zone 3
• This zone has continues high blood flow
• Here pa is greater than PA during the entire cardiac
cycle
• this region occurs in from the middle zone of lungs
to bottom

32. Effect of exercise
• Blood flow increases 4- 7 times
• Near base its 2-3 times
• In apex its 8 times
• So whole lungs becomes zone 3
• Possible because of two reasons
• Recruitment
• Distensibility
• Ability of lungs to accommodate large blood serve two purpose
• Reduces Rt heart work and prevents pulmonary edema

33. Pulmonary Capillary Dynamics
• Pulmonary transit time 4sec
• Net filtration pressure
• Net outward forces :-
• Interstitial oncotic pressure = 14mmHg
• Intersttial hydrostatic pressure = -8
• Capillary hydroststic pressure = 7
• Total = 29mmHg
• Net inward pressure:-
• Plasma oncotic pressure = 28mmHg
• NFP = 29-28= 1

34. Functions of pulmo. Circulation
• Gas exchange
• Reservoir of Lt ventricle.
• Filters for removal of emboli n other particles from blood.
• Removal of fluid from alveoli.
• Absorption of drugs.
• Synthesis of ACE.

35. Regulation
• Neural regulation is not very effective
-Effrent Sympathatic – Vasoconstrictor when stimulated
*Baroreceptor stimulation- reflex dilation.
*Chemoreceptor stimulation-vasoconstriction.
Baroreceptors- tunica adventitia of pulmo trunk-bradycardia n
hyotentn
Volume receptors-at the junc of pulmo vain n LA-tachycardia n
diuresis
J receptors-Adjacent 2 pulmo capi.-Reflex tachypnea n decrease in ms
tone .
sti by microemboli
• Chemical control is major regulatory mechanism

36. Chemical Regulation
Local hypoxia – Produce vasoconstriction.
- divert pulmo bld flow from the alveolithat are
poorly ventilated to better ventilated regions.
Hypercapnia n acidosis- vasoconstriction. Just opposite to
the systemic circulation
Chr. Hypoxia – Pulmonary hypertension result I Rt venti
hypertrophy.

37. The overall V/Q = 0.8 [ ven=4 lpm, per=5 lpm]
Ranges between 0.3 and 3.0
Upper zone –nondependent area has higher ≥ 1
Lowe zone – dependent area has lower ≤ 1
VP ratio indicates overall respiratory functional status of
lung
V/Q = 0 means ,no ventilation-called SHUNT
V/Q = ∞ means ,no perfusion – called DEAD SPACE
Ventilation Perfusion ratio VA/Q

38. Ventilation pattern - VA
•Pleural pressure [Ppl] increased
towards lower zone
•Constricted alveoli in lower zones
& distended alveoli in upper zones
•More compliant alveoli towards
lower zone
•Ventilation: distributed more
towards lower zone

39. Ventilation Perfusion ratio VA/Q
•Ventilation & Perfusion both are
distributed more towards lower zone.
•Ventilation[VA] less increased
t0wards l0wer zone than
Perfusion[Q]
•Perfusion more increased towards
Lower zone than Ventilation
•Ventilation Perfusion ratio VA/Q:
Less towards lower zone
VA/Q
VA
Q

40. Ventilation Perfusion ratio VA/Q
•Ventilation & Perfusion both are
distributed more towards lower zone.
•Ventilation[VA] less increased t0wards
l0wer zone than Perfusion[Q]
•Perfusion more increased towards
Lower zone than Ventilation
•Ventilation Perfusion ratio VA/Q:
Less towards lower zone
VA/Q
VA
Q

41. Means – Wasted perfusion
Shunt – 1. Absolute Shunt : Anatomical shunts – V/Q = 0
2. Relative shunt : under ventilated lungs –V/Q ≤ 1
Shunt estimated as Venous Admixture
Venous Admixture expressed as a fraction of total cardiac
output Qs/Qt
Qs = CcO2-CaO2
Qt CcO2-CvO2
Normal shunt- Physiologic shunt < 5%
Q
V
V/Q<1
SHUNT

42. PULMONARY EDEMA
Definition:
It is a condition in which fluid accumulates in the lungs.
OR
It is the effusion of fluid into the alveoli and the interstitial spaces
of the lungs.
Underlying Cause:
Any factor that causes the Pulmonary Interstitial fluid pressure to
rise from the negative range into the positive range will cause rapid
filling of the pulmonary interstitial spaces & alveoli with large
amounts of free fluid.

43. • CAUSES OF PULMONARY EDEMA:
1. Left-sided heart failure or mitral valve disease (Most common).
2. Damage to the pulmonary capillary membrane caused by
infections. e.g. pneumonia, inhalation of poisonous gases as
chlorine or sulfur dioxide. This causes the leakage of the
plasma proteins & fluids into the pulmonary interstitial spaces
& alveoli that raises the Pulmonary Interstitial pressure.
Safety Factor in Pulmonary edema:
The plasma capillary pressure must rise from the normal value of 7
mmHg to above 28 mmHg (plasma colloid osmotic pressure) for
edema to occur. So there is a safety factor of 21 mmHg.

44. Signs & Symptoms of Pulmonary edema:
• Difficulty breathing
• Coughing up blood (pink, frothy sputum)
• Anxiety
• Excessive sweating and pallor
• Inability to lie down due to breathlessness
• Signs of left ventricular failure like peripheral edema
& raised JVP.
• Respiratory failure
• Death

45. Treatment:
• Symptomatic treatment
• High-flow oxygen therapy.
• Diuretics to improve preload and afterload & aid in
improving the cardiac function.

46. THANK YOU