RESPIRATORY PHYSIOLOGY (HUMAN PHYSIOLOGY I) Dr. Waheeb Alharbi

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RESPIRATORY PHYSIOLOGY(HUMAN
PHYSIOLOGY I)Dr. Waheeb Alharbi
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References

• (1) Physiological basis of medical practice.
• By John B. West
• (2) Concise Human Physiology
• By M. Y. Sukkar, H. A. El-Munshid
• M. S. m. Ardawi
• (3) Human physiology
• ByGuyton

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Lecture 1

• Ventilation
• Gas transport
• Tissue respiration
• Functional anatomy of the respiratory system
• Basic mechanism of VE
• Lung volume and capacities
• Dead space
• Alveolar VE
• VD and uneven VE

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• Resp is the use of O2 by the living cell for
  oxidation of nutrients. This result in production
  of CO2.
• It can be divided into 4 main events
• 1) pulmonary VE
• 2) gas diffusion
• 3) gas transport
• 4) regulation of resp
• VE is the movement of air between the environment
  and the alveoli. It can be spontaneous or
  artificial.
• Air is a mixture of gases. According to Daltons
  Law, the total pres of a mixture of gases is the
  sum of the pres of the individual gases (Ptotal
  P1 P2 P3 ).I.e. partial pressure.
• VE fr X VT

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Gas transport

• Most gases transported in the blood in 2 forms
• 1- Dissolved in the plasma
• 2- Combine with Hb
• Under normal circumstances, more than 98 of the
  O2 in a given vol of blood is transported in
  RBCs, bound to Hb.

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Tissue resp

• It means getting energy out of glucose.
• The most efficient form of resp is aerobic
  (require O2) and anaerobic resp (does not require
  O2).
• Aerobic resp It is the normal process by which
  food substances are broken down and oxidized to
  provide energy.
• Glucose O2 ? CO2 H2O energy
  released
• Anaerobic resp It means that energy can be
  derived from food substances without the
  simultaneous utilization of O2.
• Glucose ? lactic acid much less energy
  released

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Functional anatomy of the resp system

• Anatomy of the resp system is composed of
• 1) the resp air ways
• 2) the lungs
• 3) the resp muscles
• 4) the neural centers
• The main function of the lungs is to provide
  continuous gas exchange between inspired air and
  blood in the pulmonary circulation, supplying O2
  and removing CO2, which is then cleared from the
  lungs by subsequent expir.
• The functional structure of the lung can be
  divided into
• 1- The Conducting zone, and
• 2- The respiratory zone.
• The Conducting zone (air flow) Air comes into
  the nose and the mouth through the pharynx,
  larynx and then through the trachea.
• The respiratory zone (gas diffusion) It begins
  when alveoli start to appear in the walls of the
  bronchioles.

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Basic mechanism of vent

• Breathing consists of 2 phases inspiration
  (active process) and expiration (passive
  process).
• During inspir The diaphragm and intercostals
  muscles contract. The diaphragm moves downwards
  increasing the vol of the thoracic cavity, and
  the intercostals muscles pulls the ribs up
  expanding the rib cage and further ? this vol.
• During expir The diaphragm and intercostals
  muscles relax. This returns the thoracic cavity
  to its original vol, ? the air pressure in the
  lungs, and forcing the air out.

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• Pleural pressure It is the pres in the narrow
  space between the lung pleura and chest wall
  pleura.
• Alveolar pressure It is the pres inside the lung
  alv.

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Lung volumes and capacities

• Capacity is the sum of 2 or more vols.
• Lung vol and capacity can be measured by a
  spirometer. It also can be measured by
  vitalograph, gas dilution and body
  plethysmography.
• Lung vol includes
• 1) Tidal volume (VT) It is the vol of air
  expired and inspired in each breath (500 ml).
• 2) Inspiratory reserve volume (IRV) It is the
  max vol of additional air that can be inspired
  from the end of a normal insp (3100 ml).
• 3) Expiratory reserve volume (ERV) It is the
  max vol of additional air that can be expired
  from the end of a normal exp (1200 ml).
• 4) Residual volume (RV) It is the vol of air
  that remains in the lung after maximal exp (1200
  ml).
• Lung capacities include
• 1) Inspiratory capacity (IC) VT IRV.
• 2) Functional residual capacity (FRC) ERV RV.
• 3) Vital capacity (VC) IC ERV.
• 4) Total lung capacity (TLC) IC FRC.

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Spirometer
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Normal values of lung vol and capacities in both
male female
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LUNG CAPACITIES AND RESP DISEASES

• A) Restrictive Disease. Resp disease which make
  it more difficult to get air in to the lungs.
  They restrict inspiration. Includes fibrosis,
  sarcoidosis, muscular diseases, and chestwall
  deformities.
• B) Obstructive Disease. Resp disease which make
  it more difficult to get air out of the lungs.
  Includes emphysema, chronic bronchitis, asthma.
• C) A summary of lung capacity changes during
  disease such as follow
• Restrictive Disease ? VC ? TLC, ? RV, ? FRC.
• Obstructive Disease ? VC ? TLC, ? RV, ? FRC.

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Anatomical and physiological VD

• VD is defined as the vol of inspired air that
  does not participate in GE.
• The normal VD in a young adult man is about 150
  milliliters. This ? slightly with age.
• There are two types of VD anatomical and
  physiological.
• (1) Anatomic VD is the vol of an inspired
  breath which has not mixed with the gas in the
  alv. It is anatomical because it measures the
  anatomical vol of the conducting airways leading
  up to the alv. It can be measured from the vol of
  expired gas leaving the mouth and nose before the
  'front' of alveolar gas containing CO2 arrives at
  the lips.
• (2) Physiological VD is the vol of an inspired
  breath which has not taken part in GE. It is
  physiological because it assesses one of the
  functions of the lungs (GE). It can be estimated
  using the Bohr equation, which is derived from
  the fact that the vol of gas expired equals the
  vol from the VD plus the vol from the alv.

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• In a normal person, the anatomic and physiologic
  VD are nearly equal because all alv are
  functional in the normal lung, but in a person
  with partially function or nonfunctional alv in
  some parts of the lungs, the physiologic VD may
  be as much as 10 times the vol of anatomic VD.

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VA

• VA is the total vol of new air entering the alv
  and adjacent GE area each minute.
• It is equal to the resp frequency times the
  amount of new air that enters these area with
  each breath
• VA fr X (VT- VD)
• What is the VA in a normal person?
• VA . X (. - .) ml/min
• Because of the VD, rapid, shallow resp produces
  much less VA than slow, deep resp at the same
  minute vol (see table).

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Table Effects of variations in respiratory rate
depth on VA.
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VD and uneven VE

• In the upright subject the bases of the lungs are
  found to be better ventilated than the apices.
  This can be demonstrated by breathing radioactive
  xenon.
• The uneven VE is due to the effect of gravity.
  Similarly, a subject in the supine position will
  have better VE of the posterior parts of the
  lungs than the anterior parts. Uneven VE can
  significantly affect gas exchange in the lungs.
• VE is preferentially distributed to the more
  dependent portions of the lungs because, as a
  result of the weight of the lungs, the
  intrapleural pres is lower (i.e. less negative).
• A clinical correlate of the effect of gravity on
  VE is that arterial oxygenation is improved in
  unilateral lung diseases when patients lie on
  their sides so that the good lung is in the
  dependent position.