RESPIRATION

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Chapter 5
RESPIRATION
Introduction ? Containing inspiration
expiration ? Functions Obtain O2
from external environment Remove CO2
form the body ? Respiratory processes
Pulmonary ventilation Gas exchange in
the lung Gas transport in the blood
Gas exchange in the tissue
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Respiratory processes
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1. Pulmonary ventilation ? Definition
? Principles of pulmonary ventilation
Driving force Direct pressure
changes in alveoli Source
contraction of respiratory muscles
Inspiratory muscles Diaphragm,
External intercostal muscle
Expiratory muscles Diaphragm,
Ext- Internal intercostals
Accessory respiratory muscles
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Respiratory movement
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Types of respiration ?Eupnea Forced
breathing (Deep breathing) ?Abdominal
Thoracic breathing Principles of pulmonary
ventilation ?Contraction (Relaxation) of
inspiratory muscles?Expansion
(Reduction) of thoracic
cavity?(?)Distension (Recoil) of alveoli?
Intrapulmonary pressure?(?)lt(gt) atmo-
spheric pressure?Air flows into (out of) the
alveoli
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Intrapulmonary pressure ?Inspiratory phase lt1
atm ?Expiratory phase gt1 atm ?At the end
of inspiration or expiration 1 atm Intrapleural
pressure ?Concept Changes during respiratory
cycle More negative as inspiratory
processing Less negative as expiratory
processing ?Measurement Expression
Direct Indirect measurement 775 mmHg or
?5 mmHg Always lt 1 atm under static
condition
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Changes of intrapulmonary intrapleural pressure
during respiratory cycle
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?Formation IAP PRF has opposite directions, so
IPPIAP?PRF At the end of insp- expiration,
so IPPASP?PRF If ASP0, IPP0?PRF ?PRF
IPP intrapleural pressure IAP intra
alveolar pressure PRF pulmonary recoil
force ASP atmospheric pressure
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Formation of intrapleural negative pressure
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?Significance Physiological Distend
the lung Make inspiration easier
Promote venous lymph return in the chest
Pathological (Pneumothorax) Collapse the
lung Make inspiration difficult Affect
venous lymph return Fatal in pulmonary
circulatory failure cases Importance
Keep the interpleural cavity hermetically sealed
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Resistance to breathing Elastic of the
lung Elastic Compliance
CL1/RL?VL/?PL(L/cmH2O) Static
compliance (Cst) of the lung S shaped
curve, divided into 3 portions
Flattened upper portion Steep middle
portion Flattened lower portion
Special compliance (Csp) Csp CL/TLC
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Static compliance (Cst) of the lung
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S shaped compliance curve of the lung
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Source of elastic of the lung Elastic tissue
(1/3) Alveolar surface tension (2/3) Pulmonary
surfactant Nature A lipoprotein, Main lip
component is DPL Characteristics Both
hydro-philia -phobicity Source Type II
alveolar epithelial cells Distribution Inner
surface of the alveoli Action Reduce the
alveolar surface tension Significance
Decrease the inspiratory resistance,
Stabilize the volume pressure in the alveoli,
Prevent pulmonary edema
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Pulmonary compliance curve when filled with air
or saline
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Pulmonary recoil force in the big small alveoli
communicated each other
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Elastic of the thorax Characteristics of
elastic resistance of the thorax
Elastic resistance Pulmonary capacity Inspiration Expiration
Thorax gt67TLC Resistance Driving force
Thorax 67TLC ? ?
Thorax lt67TLC Driving force Resistance
Lung For ever Resistance Driving force
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Non-elastic resistance Airway resistance
(main) Definition Calculation
Factors affecting the airway resistance
Velocity of air flow RAW ? VAF Type of air
flow Laminar flow Turbulence Diameter of
airway Transmural pressure Radiate
traction by pulmonary parenchyma Autonomic
nervous system Chemical factors
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Differences between the large small airway
Large airway Small airway
Diameter gt 2 mm lt 2 mm
Total cross- sectional area Small Large
Air flow velocity Faster Slower
Type of air flow Turbulence Laminar
Total airway resistance 90 10
Fall ill Not easy Easy
Resistance gt 2 cmH2O lt 2 cmH2O
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? Pulmonary volume capacity Tidal volume
(TV) Inspiratory reserve volume (IRV)
TExpiratory reserve volume (ERV) Residual
volume (RV) Inspiratory capacity (IC)
Functional residual capacity (FRC) Vital
capacity (VC) Forced vital capacity (FVC)
Forced expiratory capacity (FEC)
Total lung capacity (TLC)
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Pulmonary volume capacity
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Forced expiratory volume
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? Pulmonary ventilation volume Minute
ventilation volume Maximal (voluntary)
ventilation Percentage of ventilation
reserve volume Anatomical, Alveolar
Physiological dead space, Alveolar
ventilation MVVTV RF AV(TV?DSV)RF MVVTV/22R
F AV?(TV/2?DSV)2RF MVV2TVRF/2
AV?(2TV?DSV)RF/2
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2. Respiratory gas exchange ? Mechanisms
of gas exchange Driving force Partial
pressure of O2 or CO2 Mode Diffusion
of gas Condition Permeability of
membrane ? Processes of gas exchange
Po2 Pco2 in alveoli, blood tissue (mmHg)
Alveolar air Venous blood Arterial blood Tissue
Po2 104 40 100 30
Pco2 40 46 40 50
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Processes of gas exchange
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? Factors affecting gas exchange Diffusion
rate of gas
Ventilation/perfusion ratio (V/Q)
Definition its normal value (0.84)
If V?/Q ? gt 0.84 Alveolar dead space ?
V?/Q ? lt 0.84 Functional A-V shunt
Anoxia occurs more easily than CO2 retention
Affecting by gravity when a person stands

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Respiratory membrane
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Ventilation/perfusion ratio (V/Q)
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DN
3. Gas transport in the blood ? Oxygen
transport Forms of transport
Physically diffusion Combination with Hb
Characteristics of Hb combined with O2
Fast, reversible, need not enzyme,
oxygenate with Fe2, O2 combined
with Hb is 41, S shaped oxygen
dissociation curve Oxygen capacity,
content saturation Cyanosis carbon
monoxide poisoning
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Oxygen dissociation curve Definition why
it is in S shaped Physiological advantages of
S shaped curve The flattened upper portion
(60100 mmHg) The steep middle portion
(4060 mmHg) The steep lower portion (1540
mmHg) Factors affecting oxygen dissociation
curve Concept of P50, affinity to O2, right
or left shift Factors pH Pco2 (Bohr
effect), temperature, 2,
3-DPG, others (Fe2?Fe3, CO)
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Oxygen dissociation curve
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Factors affecting oxygen dissociation curve
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? Carbon dioxide transport Forms of
transport Physically diffusion
Combination with Hb HCO3?
HHbNHCOOH
Carbon dioxide dissociation curve
Influence of combination of Hb with O2 on
CO2 transport (Haldane effect)
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Carbon dioxide transport in the blood
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Carbon dioxide dissociation curve
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4. Regulation of respiratory activity ?
Respiratory centers In the spinal cord
In the lower brain stem
Research techniques Brain stem
transection, Microelectrode, etc.
Medullary oblongata DRG VL-NTS
VRG cVRG, i(or r)VRG, Böt C, pre-Böt
C Pons Pneumotaxic center, PBKF
(NPBMKF) In the higher brain Cerebral
cortex, Limbic system, Hypothalamus
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Research on respiratory centers Brain stem
transection
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? Formation of respiratory rhythm A key
region of its generation Pre-Böt C
Central inspiratory activity generator (CIAG)
Inspiratory off switch mechanism (IOS) ?
Respiratory reflexes Pulmonary stretch
reflex (Hering-Breuer ) Inflation
deflation reflex Chemoreflex
Peripheral central chemoreceptors
Respiratory regulation of CO2, H O2
Interaction of CO2, H O2 on the regulation
Proprioceptive reflex of respiratory muscles
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PBKF



CIAG, Insp. Neurons
IOS
-


Insp. Muscular Neurons


Insp. movement
PSR
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Off switch mechanism

-
-
Insp. center (medulla)
Insp. Neurons (spinal cord)
?
?
Contraction (or relaxation) of insp. muscles
Inflation (or Deflation)
Inflation receptor or deflation receptor
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Paco2? Ha? Pao2?
Resp. A ? F ?
Carotid aortic bodies
Resp. Center (Medulla)
(-)
O2
O2
HCO3? H
CO2H2O
CO2
Central chemoreceptor
H
H
CSF
Blood
A amplitude F frequency BBB blood-brain
barrier CSF cerebrospinal fluid
BBB
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Respiratory regulation of CO2, H O2
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