respiratory physiology

1. 11
Dynamics of Pulmonary Circulation
& Pulmonary Edema
Prof. Dr. Rashid Mahmood
• A 60 year old diabetic who had an attack of
Myocardial infarction an year ago,
complains of chest pain, difficulty in
breathing, cough with blood stained sputum
and edema feet. He had been diagnosed as
a patient of congestive cardiac failure.
1.What is the cause of his cough and problem
in breathing?
2.Which side heart failure contributes to this
respiratory system problem?

2. 22
Objectives
• Goal/Aim: To understand the physiology of
pulmonary dynamics and pulmonary edema
• Specific Objectives: At the end of this lecture
students should be able to
• Compare pressures in Pulmonary blood vessels
and Systemic blood vessels
• Explain capillary exchange of fluid in the lungs
and pulmonary interstitial fluid dynamics
• Describe the mechanism of development of
Pulmonary Edema
• Explain “Pulmonary edema safety factor” and its
significance

3. 33
Lesson Contents
• Physiologic Anatomy of the Pulmonary
Circulatory System
• Difference between systemic and
pulmonary blood vessels
• Pressures in the different vessels of the
lungs
• Pulmonary Capillary Dynamics
• Pulmonary Edema
• Pulmonary Edema Safety Factor

4. 44
Physiologic Anatomy of the Pulmonary
Circulatory System
• Pulmonary Vessels
– pulmonary artery
• wall thickness one third that of the aorta
– large compliance
– pulmonary veins
• into the left atrium
• Bronchial Vessels
– flow into the left atrium and the left ventricular
output are about 1 to 2 per cent greater than
the right ventricular output.

5. 55
Difference between systemic and
pulmonary blood vessels
Blood vessels Systemic Pulmonary
Walls of large arteries Thicker Thinner (30% as thick
as Systemic)
Small arteries More muscle Less muscle
(endothelial tubes)
Walls of post-capillary
vessels
Almost no smooth
muscle
smooth muscle
present
Capillaries Smaller Larger, with multiple
anastomosis (each
alveolus sits in
capillary basket)

6. 66
Lymphatics
• right thoracic lymph duct
• prevent pulmonary edema
• remove
– Particulate matter entering the alveoli
– protein leaking from the lung capillaries

7. 77
Pressure pulse contours in the right
ventricle, pulmonary artery, and aorta
systolic
pressure in the
right ventricle =
25 mm Hg
diastolic
pressure =0 to
1 mm Hg
systolic
pulmonary
arterial
pressure =25
mm Hg
diastolic
pulmonary
arterial
pressure = 8
mm Hg

8. 88
Pressures in different vessels of lungs
• systolic pulmonary
arterial pressure =
25 mm Hg
• diastolic pulmonary
arterial pressure =
8 mm Hg
• mean pulmonary
arterial pressure =
15 mm Hg
• Pulmonary Capillary
Pressure=
7 mm Hg
• Left Atrial and
Pulmonary Venous
Pressures =
2 mm Hg

9. 99
Assessment Q. 1
• What is the anatomical difference
between capillaries of systemic
and pulmonary circulation?

10. 1010
Blood flow at different levels in the lung
of an upright person
at rest, the blood flow is
very low at the top of the
lungs; most of the flow
is through the bottom of
the lung.

11. 1111
Mechanics of blood flow in the three
blood flow zones of the lung
zone 3, continuous flow-arterial
pressure and pulmonary capillary
pressure (Ppc) remain greater than
alveolar air pressure at all times.
zone 1, no flow-alveolar air
pressure (Palv) is greater than
arterial pressure;
zone 2, intermittent flow-
systolic arterial pressure rises
higher than alveolar air
pressure, but diastolic arterial
pressure falls below alveolar air
pressure;

12. 1212
Effect on mean pulmonary arterial
pressure caused by increasing the
cardiac output during exercise.

13. 1313
Function of the Pulmonary Circulation
When the Left Atrial Pressure Rises as a
Result of Left-Sided Heart Failure
• healthy person: almost never rises above
+6 mm Hg, even during the most
strenuous exercise
• up to about 7 mm Hg→ little effect
• greater than 7 or 8 mm Hg→↑ pulmonary
arterial pressure
→increased load on the right heart
→increases the capillary pressure
→pulmonary edema (safety factors)

14. 1414
Pulmonary Capillary Dynamics
• Length of Time Blood Stays in the
Pulmonary Capillaries
• 0.3 second

15. 1515
Assessment Q. 2 (MCQ)
• If the systolic arterial pressure rises higher
than alveolar air pressure, but diastolic
arterial pressure falls below alveolar air
pressure; the flow in pulmonary capillaries
will be:
A.no flow
B.intermittent flow
C.continuous flow

16. 1616
Capillary Exchange of Fluid in the Lungs,
and Pulmonary Interstitial Fluid Dynamics
• qualitatively same as for peripheral
tissues
• quantitatively, important differences
• slight continual flow of fluid from the
pulmonary capillaries into the interstitial
spaces
–pumped back to the circulation through the
pulmonary lymphatic system
–a small amount that evaporates in the
alveoli

17. 1717
Hydrostatic and osmotic forces at
the capillary (left) and alveolar
membrane (right) of the lungs

18. 1818
Difference between systemic and
pulmonary capillary dynamics
Pressure (mmHg) Systemic Pulmonary
Pc 17.3 7
Pisf -3 -8
πc 28 28
πisf -8 -14
Net filtration P
Pc+πisf-πc-Pisf
0.3 1

19. 1919
Assessment Q. 3
• Calculate net filtration pressure of
pulmonary capillaries, if
• Pc= 7
• Pisf= -8
• Πc= systemic colloid osmotic pressure
• πisf+= -14

20. 2020
Mechanism for Keeping the Alveoli
"Dry
• Negative Pulmonary Interstitial
Pressure
• pulmonary capillaries
• pulmonary lymphatic system

21. 2121
Pulmonary Edema
• Mechanism :
– rapid leakage of both plasma proteins and fluid out of
the capillaries and into both the lung interstitial spaces
and the alveoli
– Any factor that causes the pulmonary interstitial fluid
pressure to rise
• causes
– Left-sided heart failure or mitral valve disease
– Damage to the pulmonary blood capillary membranes
• infections such as pneumonia
• noxious substances such as chlorine gas or sulfur dioxide
gas

22. 2222
Rate of fluid loss into the lung tissues
when the left atrial pressure (and
pulmonary capillary pressure) is increased

23. 2323
Pulmonary Edema Safety Factor
• pulmonary capillary pressure must rise from the
normal level of 7 mm Hg to more than 28 mm
Hg to cause pulmonary edema, giving an acute
safety factor against pulmonary edema of 21
mm Hg
• Safety Factor in Chronic Conditions
• lymph vessels expand greatly
• 40 to 45 mm Hg
• Rapidity of Death in Acute Pulmonary Edema
• 20 to 30 minutes
• in acute left-sided heart failure

24. 2424
Summary points
• The pressure gradient in the pulmonary circulation
system is much less than that in the systemic
circulation, although qualitatively the same.
• Rapid leakage of both plasma proteins and fluid out
of the capillaries and into both the lung interstitial
spaces and the alveoli is call Pulmonary Edema.
• Any factor that causes the pulmonary interstitial fluid
pressure to rise will result in Pulmonary Edema
• Pulmonary capillary pressure must rise from the
normal level of 7 mm Hg to more than 28 mm Hg to
cause pulmonary edema, giving an acute safety
factor against pulmonary edema of 21 mm Hg

25. 2525
Assessment Q. 4
• In a patient with chronic left heart failure
capillary pulmonary capillary pressure
rises 4 times than its normal resting value.
Will pulmonary edema develop in this
patient? Explain the reason also.

26. 2626
Trigger
• A 60 year old diabetic who had an attack of
Myocardial infarction an year ago, complains of
chest pain, difficulty in breathing, cough with blood
stained sputum and edema feet. He had been
diagnosed as a patient of congestive cardiac failure.
1. What is the cause of his cough and problem in
breathing?
2. Which side heart failure contributes to this
respiratory system problem?

27. 2727
Learning resources
• Guyton and Hall (Text book of
physiology), 13th Edition
• Ganong (Text book of physiology),
24th Edition
• Lauralee Sherwood Human
physiology from Cells to Systems, 9th
edition.
® Prof. Dr. rashid Mahmood 27

28. 2828
Surah: 24 Al-Noor Aya: 19
Questions?
Comments?
drrashid62@gmail.com
rashid.mahmood@rmc.edu.pk
The End