The document outlines the mechanics of pulmonary ventilation, detailing the roles of various muscles in inhalation and exhalation, the pressures involved, and factors influencing airflow. It describes pulmonary volumes and capacities, including tidal volume, inspiratory reserve volume, and total lung capacity, while noting differences in lung volumes between sexes and fitness levels. Additionally, it discusses the impacts of smoking on airway resistance and energy expenditure during respiration.

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2. External respiration can be divided
into
4 major functional events
1) Ventilation
2) Diffusion
3) Transport of O2 and CO2 in the
blood, body fluids, to and from
the cells
4) Regulation of ventilation

3. PULMONARY VENTILATION
 BOYLE’S LAW
 Gas pressure in closed container is
inversely proportional to volume of
container
 Pressure differences and Air flows

4. Mechanics of pulmonary
v e n t i l a t i o n
Diaphragm – which increase and decrease the vertical
diameter of the chest cavity.
Intercostal muscles – affect the anteroposterior
diameter of the chest cavity by moving the ribs.
Internal intercostal muscle (downward and backward)
 lower the ribs and sternum  reducing the
anteroposterior diameter
External intercostal muscle (downward and forward) 
raise the ribs and sternum  increasing the
anteroposterior diameter of the thoracic cavity

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7. Inspiration/Inhalation
 Diaphragm & Intercostal muscles
 Increases volume in thoracic cavity as
muscles contract
 Volume of lungs increases
 Intrapulmonary pressure decreases
(758 mm Hg)

9. Expiration/Exhalation
 Muscles relax
 Volume of thoracic cavity decreases
 Volume of lungs decreases
 Intrapulmonary pressure increases
(763 mm Hg)
 Forced expiration is active

12. Factors that influence
pulmonary air flow
 F = P/R
 Diameter of airways, esp. bronchioles
 Sympathetic & Parasympathetic NS

13. Various pressure in the lungs
Pleural pressure – is the pressure of fluid in the narrow
space between the visceral and parietal pleura,
normally slightly negative pressure
The normal pleural pressure at the beginning of
inspiration is –5cm of H2O (it reach about –7.5cm of
H2O due to movement of the chest cage)
The pleural pressure at the beginning of expiration is
–7.5cm of H2O to reach –5cm of H2O

14. Alveolar pressure
Alveolar pressure: – is the pressure inside the lung
alveoli
During inspiration: ¯ –1cm of H2O (this slight
negative pressure is enough to move about 0.5 liter
of air into the lungs in the first 2 second of
inspiration)
During expiration: it rises to about +1cm of H2O (this
forces 0.5 liter of inspired air out of the lungs during
the 2 to 3 seconds of expiration

16. Inspiration and expiration

17. T h e work done in breathing
the work of inspiration can be divided into 3
fractions:
The work required to expand the lungs against its
elastic forces called compliance work or elastic work.
The work required to overcome the viscosity of the
lung and chest wall structures called tissue
resistance work.
The work required to overcome airway resistance
called airway resistance work.
Work energy required for respiration:
during normal quiet respiration = 2 to 3% of the total
work energy (­ to 50 fold in exercise, ­ airway
resistance).

18. Pulmonary volumes and
c apacities
1) Tidal volume – is the volume of air inspired or expired with
each normal breath = 500ml in young adult man.
2) Inspiratory reserve volume – is the extra volume of air
that can be inspired over and beyond the normal tidal volume
= 3000ml.
3) Expiratory reserve volume – is the extra amount of air
that can be expired by forceful expiration after the end of a
normal tidal expiration ~ 1100ml.
4) Residual volume – is the extra volume of air that still
remain in the lungs after the most forceful expiration ~
1200ml.

19. The pulmonary capacities
1) Inspiratory capacity – is the volume of air inspired by a maximal
inspiratory effort after normal expiration = 3500ml =
inspiratory reserve volume + tidal volume.
2) The functional residual capacity – is the volume of air remaining in
the lungs after normal expiration = 2300ml = expiratory reserve
volume + residual volume.
3) The vital capacity – is the volume of air expired by a maximal
expiratory effort after maximal inspiration ~ 4600ml =
inspiratory reserve volume + tidal volume + expiratory reserve
volume.
4) Total lung capacity – is the maximum volume of air that can be
accommodated in the lungs ~ 5800ml = vital capacity + residual
volume.
5) Minute respiratory volume – is the volume of air breathed in or out
of the lungs each minute = respiratory rate x tidal volume = 12
X 500ml = 6000ml/min.
All lung volume and capacity are about 20 to 25% less in women
than in men and are greater in athletic persons than in small
and asthenic persons.

21. Does Ventilation Limit Aerobic
Capacity for Average Person?
 If inadequate
breathing capacity
limited aerobic
capacity, ventilatory
equivalent for oxygen
would decrease.
 Actually, healthy
person tends to over-breathe
in relation to
VO2.
 In strenuous exercise,
decreases arterial PCO2
& increase Alveolar
PO2.

22. Work of Breathing
 Acute effects of 15 puffs
on a cigarette during a 5-
minute period
 3 fold increase in airway
resistance
 Lasts an average 35
minutes
 Smokers exercising at
80%
 Energy requirement of
breathing after smoking
was 14% of oxygen
uptake
 Energy requirement of
breathing no cigarettes
was only 9%.

23. THANK YOU.