Breathing mechanics presentation systems

Breathing

1. Prof. Sultan Ayoub Meo
MBBS, M.Phil, Ph.D (Pak), PG Dip Med Ed, M Med Ed (Scotland)
FRCP (London), FRCP (Dublin), FRCP (Glasgow), FRCP (Edinburgh)
Professor and Consultant, Department of Physiology,
College of Medicine, King Saud University, Riyadh, Saudi Arabia
MECHANICS OF BREATHING

2. MECHANICS OF BREATHING

3. Mechanicsmeanssciencethatdealswithforces
Breathingmechanicsisinterplayofforcegeneratedby
pressure,volumeandflowchangesoccurringduringthe
breathingcycle
Roleofrespiratorymuscles
Alveolar,PleuralandTranspulmonarypressures
Complianceoflungs,chestwall&together
Lungrecoilduetoelastic&collagenfibers
Workofbreathing.
MECHANICS OF BREATHING

4. Muscles of inspiration
Principal muscles
•Diaphragm
•External intercostals
Accessory muscles
•Sternocleidomastoid
•Scaleni
•Serratus anterior
•Pectoralis minor
Muscles of forced expiration
•Internal intercostal
•External oblique abdominis
•Internal oblique abdominis
•Rectus abdominis
•Transversus abdominis
Muscles of normal expiration
•Normal expiration is due to
elastic recoil of lungs and
associated structures
MUSCLES OF RESPIRATION

5. MUSCLES OF RESPIRATION

6. MUSCLES OF RESPIRATION

7. FUNCTIONS OF THE
RESPIRATORY MUSCLES

8. FUNCTIONS OF THE
RESPIRATORY MUSCLES

9. FUNCTIONS OF THE
RESPIRATORY MUSCLES

10. FUNCTIONS OF THE
RESPIRATORY MUSCLES

11. FUNCTIONS OF THE
RESPIRATORY MUSCLES

12. IntraAlveolarpressure(Alveolarpressure):
Pressureinsidethealveoli.Theprocessofinspiration
andexpirationdependsuponthispressure.
Normalalveolarpressureisequaltothe
atmosphericpressure=760mmHg.
ALVEOLAR PRESSURE

13. ALVEOLAR PRESSURE
Alveolarpressureduringinspiration:Thealveolarpressure
islowerthantheatmosphericpressureduringinspiration(760
to758mmHg)soairmovesfromtheatmospheretowardsthe
lungalveoli.
Alveolarpressureduringexpiration:Alveolarpressureis
increasedduringtheprocessofexpirationandisslightlymore
withrespecttotheatmosphericpressure(763mmHg)soair
movesfromlungstotheatmosphere.

14. ALVEOLAR PRESSURE

15. Intrapleuralpressureorpleuralpressure:Pressureinthe
narrowspacebetweenthelungpleuraandchestwallpleura.
Negativepressureinthepleuralspacepreventthecollapseof
thelungs.
-5cmH
2Oatthebeginningofinspiration
-7.5cmH
2Oatthepeakofinspiration
Transpulmonarypressure:Pressuredifferencebetweenthe
alveolarandpleuralpressureiscalledtranspulmonarypressure.
PLEURAL AND TRANSPLEURAL
PRESSURE

16. CHANGING ALVEOLAR VOLUME

17. NORMAL BREATHING CYCLE

18. NORMAL BREATHING CYCLE

19. 19
ROLE OF NEGATIVE INTRAPLEURAL
PRESSURE
Atresttheintrapleuralpressureisnegative(Sub-
atmospheric)Morenegativeatapex(-10cmsofwater)as
comparedtobase(-2.5cmsofwater)
ItcanbecomemorenegativeduringdeepInspirationand
becomessubstantiallymorepositiveduringForced
expiration
Mainfunctionisthatitpreventsthelungsfromcollapsing
andthechestwallfromgoingout.

20. Pulmonary ventilation (Pulmo=lungs, ventilation=breathing)
Pulmonary ventilation is the inspiration (inflow) and expiration
(outflow) of air between the atmosphere and lungs
In ventilation important factor called the pressure gradient exists.
Air moves into the lungs when the pressure inside the lungs is
less than that of the atmospheric pressure.
Air moves from the lungs to the atmosphere, when the pressure
in the lungs is greater than the atmospheric pressure.
PULMONARY VENTILATION

21. PULMONARY VENTILATION
[INSPRATION AND EXPIRATION]

22. PULMONARY VENTILATION
[INSPRATION AND EXPIRATION]

23. PULMONARY VENTILATION
[INSPIRATION]
Movementofairinto
andoutoflungs
Airmovesfromarea
ofhigherpressureto
areaoflowerpressure
Pressureisinversely
relatedtovolume

24. PULMONARY VENTILATION
[INSPIRATION]

25. PULMONARY VENTILATION
[INSPRATION]

26. THORACIC VOLUME

27. THORACIC VOLUME

28. THORACIC VOLUME

29. THORACIC VOLUME

30. PULMONARY VENTILATION
[EXPIRATION]
Relaxation of inspiratory muscle
Decreased vertical and antero-posterior diameter of
the chest cavity
Increased intra-thoracic pressure
Size of lungs decreases
Increased alveolar pressure from 760-763 mm Hg
Air moves from lung alveoli towards atmosphere
Expiration

31. PULMONARY VENTILATION
[EXPIRATION]

32. THANK YOU
College of Medicine, King Khalid University
Hospital, King Saud University, Riyadh,
Saudi Arabia