Upload
husnainahmed
View
241
Download
0
Embed Size (px)
Citation preview
7/28/2019 Respiration 1.ppt
1/33
Respiration
Dr Sabeen Haq
7/28/2019 Respiration 1.ppt
2/33
Respiration
Introduction
Internal respiration, cellular respiration
External respiration
Breathing
Mechanical act of moving gases in and out
7/28/2019 Respiration 1.ppt
3/33
Steps of external respiration
Breathing
Exchange of gases between alveoli and
pulmonary blood
Transport of gases to tissues
Exchange of gases between tissues and systemic
circulation First 2 steps by respiratory system
Last two steps by circulatory system
7/28/2019 Respiration 1.ppt
4/33
Anatomy of airway
7/28/2019 Respiration 1.ppt
5/33
Conducting zone
Respiratory airway starting from nose till
terminal bronchiole is conducting zone.
7/28/2019 Respiration 1.ppt
6/33
Respiratory unit
It is gas exchange area
Respiratory
bronchioles,
alveolar ducts, atria
and alveoli
7/28/2019 Respiration 1.ppt
7/33
7/28/2019 Respiration 1.ppt
8/33
Functions of respiratory system
Respiratory function
Evaporation and heat loss
Increases venous return
Acid base balance
Enables vocalization
Defense against inhaled foreign materials
Lungs activate angiotensin II
Nose - smell
7/28/2019 Respiration 1.ppt
9/33
Mechanics of respiration
Pleural pressure:
Pressure of fluid inside pleural cavity Slightly negative pressure
Varies from -5 to -7.5cm of H2O during
inspiration and expiration
7/28/2019 Respiration 1.ppt
10/33
Mechanics of respiration
Alveolar pressure:
Pressure of air
inside lung
alveoli
7/28/2019 Respiration 1.ppt
11/33
Mechanics of respiration Cont.
Transpulmonary pressure:
Difference between alveolar pressure andpleural pressure
Measure of elastic forces in the lungs that
tend to collapse the lungs during respirationAlso known as recoil pressure
7/28/2019 Respiration 1.ppt
12/33
Compliance:
Distensibility (stretchability):
Ease with which the lungs can expand.
100 x more distensible than a balloon.
Elasticity:
Tendency to return to initial size after distension.
High content of elastin proteins.
Very elastic and resist distension.
Recoil ability.
Physical Properties of the Lungs
7/28/2019 Respiration 1.ppt
13/33
Compliance
The extent to which lungs can expand for each
unit increase in transpulmonary pressure
Total compliance of both lungs = 200ml / cm
of H2O transpulmonary pressure
7/28/2019 Respiration 1.ppt
14/33
Compliance diagram
Compliance is determined by elastic forces of
lungs which are:
Elastic forces of lung tissues itself
Elastic forces caused by surface tension of the
fluid that lines the inside walls of alveoli
7/28/2019 Respiration 1.ppt
15/33
Compliance diagram
Tissue elastic forces tending to collapse the
lungs represent only 1/3rd of the total lung
elasticity and fluid-air surface tension forces
represent about 2/3rd.
7/28/2019 Respiration 1.ppt
16/33
7/28/2019 Respiration 1.ppt
17/33
Compliance of thorax and lungs
together
To inflate lungs in thoracic cavity, twice as much
pressure is requires than that to inflate lungs
alone
Compliance of total system is half i.e around 110
ml
7/28/2019 Respiration 1.ppt
18/33
Mechanics of respiration
Lungs can be expanded or contracted by:
Upward or downward movement ofdiaphragm
Elevation or depression of ribs
7/28/2019 Respiration 1.ppt
19/33
7/28/2019 Respiration 1.ppt
20/33
7/28/2019 Respiration 1.ppt
21/33
Muscles of inspiration
They contract the diaphragm and elevate the rib
cage
Quiet inspiration:
Diaphragm = vertical diameter
External intercostals = anteroposterior and
lateral diameter
Forceful inspiration
Sternocleidomastoid
Anterior serrati
scleni
7/28/2019 Respiration 1.ppt
22/33
7/28/2019 Respiration 1.ppt
23/33
Muscles of expiration
Quiet expiration:
Relaxation of diaphragm and elastic recoil of
lungs, chest wall and abdominal structures
Forceful expiration:
Abdominal recti
Internal intercostals
7/28/2019 Respiration 1.ppt
24/33
7/28/2019 Respiration 1.ppt
25/33
Work of breathing
Quiet breathing
Inspiration = active process
Expiration = passive process
Work of inspiration
Compliance work
Tissue resistance work
Airway resistance work
7/28/2019 Respiration 1.ppt
26/33
Work of breathing Cont.
Energy required:Quiet respiration = 3-5 % of total energy
Energy requirement increases up to 50 folds in
case of
Increase airway resistance (COPD)
Decrease pulmonary compliance (Fibrosis)
Decreased lung elastic recoil (Emphysema)
When increased ventilation needed ( Exercise)
7/28/2019 Respiration 1.ppt
27/33
7/28/2019 Respiration 1.ppt
28/33
Surfactant
Surfactant decreases surface tension to 1/2 -1/12. Secreted by type II alveolar epithelial cells
Dipalmitoyl phosphatidylcholine + surfactant
apoproteins + calcium ions
Surface tension of
pure water = 72 dynes/cm
Alveolar fluid without surfactant = 50 dynes/cm
Alveolar fluid with surfactant = 5-30 dynes/cm
7/28/2019 Respiration 1.ppt
29/33
Surfactant
7/28/2019 Respiration 1.ppt
30/33
7/28/2019 Respiration 1.ppt
31/33
Pressure in occluded alveoli
Surface tension tends to collapse the alveoli
Pr = 2 surface tension / radius of alveoli
Pressure in average size alveoluswith normal surfactant = 4 cm of H2O
with no surfactant = 18 cm of H2O
Inverse relationship of radius with pressure
7/28/2019 Respiration 1.ppt
32/33
Respiratory distress syndrome of
newborn
Radius of alveoli in premature babies is quarter
as compared to that in adults.
Surfactant begin to secrete around 6 to 7th
month of gestation.
So tendency of alveoli to collapse is 6-8 times
higher
Treatment = continuous positive pressure
ventilation
7/28/2019 Respiration 1.ppt
33/33