140401 pertukaran gas, transportasi gas dan pengendalian pernapasan
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FisiologiPernapasan:Pertukaran Gas, Transportasi Gas dan
Pengendalian Pernapasan
Ninuk Dian K
1
Tujuan instruksional, mahasiswadapat menjelaskan:• Proses pertukaran gas: pressure gradient, sistem kapiler,
ventilasi dan perfusi matching
• Transport gas: fungsi Hb, faktor yang mempengaruhi afinitas
Hb, BGA sebagai penanda status respirasi (keseimbangan
asam-basa respiratorik), proses pengikatan O2 dan CO2 dalam
darah, transport O2 dan CO2
• Pengendalian respirasi: batang otak, pengendalian secara
kimiawi oleh PO2, PCO2, H+
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Organ Respirasi
Zona konduksi• Saluran yang
membawa udara ketempat pertukarangas
• Menyaring,melembabkandanmenghangatkanudara
Zona respirasi• Tempat pertukaran
gas
• Terdiri dari• Bronkhioli
• Alveoli 3
• Ventilasi:
• Bernapas dengan paru dan otot
• Pertukaran gas:
• Antara udara dan kapiler paru
• Antara kapiler sistemik dengan jaringan
• Penggunaan 02 :
•Respirasi seluler di mitokondria
Respirasi
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PERTUKARAN:
DIFUSI &
TRANSPORT GAS
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Alveolus
tempat gas difusion & gas exchange
O2
CO2
• antara 2 kompartemen
alveolus & kapiler
• dibatasi oleh parenkim
• dipengaruhi oleh
1. gradient tekanan
2. luas permukaan
3. tebal membran
RD = k x A x P x 1/D 6
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P : Gradient tekanan
• P : beda tekanan parsial gas antara alveolus dengan kapiler
• Tekanan parsial gas : PO2, PCO2
• Semakin besar beda tekanan, semakin mudah difusi terjadi
• Arah difusi, dari tekanan
• PaO2,> PO2,O2,berdifusi ke dalam kapiler
• PaCO2, < PCO2 ,CO2 berdifusi ke alveolus
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Man a ya ng R D pa li ng be sa r ?
• alveolus yang lebih
besar memiliki area
difusi yang lebih luas
• makin besar alveolus,
makin mudah difusi gas
• restriksi, compliance ,alveolus kecil, RD kecil,
hipoksia8
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PERTUKARAN GAS DAN V/Q
MATCHING
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ec an sms o u monary
Ventilation
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Komponen sistem respirasi
• Zona konduksi.
• Zona Respirasi
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• All the structures air
passes through before
reaching the respiratory
zone.
• Function:
• Warms and humidifies
inspired air.
• Filters and cleans:
• Mucus secreted to
trap particles in theinspired air.
• Mucus moved by cilia
to be expectorated.
Insert fig. 16.5
Conducting Zone
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• Region of gasexchangebetween airand blood.
• Includesrespiratorybronchioles
and alveolarsacs.
Respiratory Zone
The Bronchi and Lobules of the
Lung
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Respiratory Membrane
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Respiratory Membrane
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Lung Perfusion and Ventilation
Matching
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Circulation Overview
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Ventilation and Perfusion
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Ventilation Perfusion Match in the Lungs
Local controls act on the smooth muscles of airways andarterioles to match airflow to blood flow
Accumulation of CO2 in alveoli as a result of increasedperfusion decreases airway resistance leading toincreased airflow
Increase in alveolar O2 concentration as a result of increased ventilation causes pulmonary vasodilation
which increases blood flow to match larger airflow
Area in which blood flow (perfusion)
is greater than airflow (ventilation)
Helps
balance
Helps
balanceLarge blood flow
Small airflow
CO2 in area
Relaxation of local-airway
smooth muscle
Dilation of local airways
Airway resistance
Airflow
O2 in area
Contraction of local pulmon-
ary arteriolar smooth muscle
Constriction of local blood vessels
Vascular resistance
Blood flow
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Area in which airflow (ventilation)
is greater than blood flow (perfusion)
Helps
balance
Helps
balanceLarge airflow
Small blood flow
CO2 in area
Contraction of local-airway
smooth muscle
Constriction of local airways
Airway resistance
Airflow
O2 in area
Relaxation of local pulmonary
arteriolar smooth muscle
Dilation of local blood vessels
Vascular resistance
Blood flow
Edema paru: swelling parenkim paru
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Transport Gas
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Transport Gas dalam darah
• Transport oksigen dalam darah
• Sebagian besar melalui hemoglobin (Hb)
• Sebagian kecil terlarut dalam plasma
• Jumlah Oksigen yang dibawa Hb dipengaruhi :
• PO2 plasma: ventilasi paru, komposisi gas, RD
• pH
• temperature
• DPG
• Kadar Hb
• Fetal hemoglobin has a higher O2 affinity than adult
hemoglobin
• % saturasi Hb = O2 max yang terikat x 100% 27
An Overview of Respiratory Processes and Partial Pressures in
Respiration
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Gas Exchange in the Lungs and
Tissues: Oxygen
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Gas Transport in the Blood:
Oxygen
• 2% in plasma
• 98% in hemoglobin (Hb)
• Blood holds O2 reserve
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Hemoglobin Transport of Oxygen
• 4 binding sites per Hb molecule
• 98% saturated in alveolar arteries
• Resting cell PO2 = 40 mmHg
• Working cell PO2 = 20 mmHg
• More unloaded with more need
• 75% in reserve at normal activity
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Forming Oxyhemoglobin
Figure 17.6a
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Dissociation of O2 from
Hemoglobin
Figure 17.6b
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Saturation of Hemoglobin with
O2
• Arterial blood
• Hemoglobin is 98.5% saturated
Figure 17.7a
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Saturation of Hemoglobin with
O2
• Venous blood
• Hemoglobin is 75% saturated
Figure 17.7b
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O2 and CO2 Movement
Figure 17.1
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Hemoglobin Saturation Curve
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• Temperature, pH, PCO2, and DPG• Increase of temperature, PCO2, and DPG and decrease of pH :
• Decrease hemoglobin’s affinity for oxygen
• Enhance oxygen unloading from the blood
• Decreases of temperature, PCO2, and DPG and the increase of pH act in theopposite manner
• These parameters are all high in systemic capillaries where oxygenunloading is the goal
Factors Influencing
Hemoglobin Saturation
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Figure 17.9
Effects of O2 Affinity Changes• Shift right
• Less loading of O2
• And less unloading
• Shift left
• More loading of O2
• And less unloading
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Temperature Effects: O2
Saturation• Higher temperature
• Active tissues
• Shift right
• More O2 unloading in tissues
• More O2 delivery to tissues
Figure 17.10a
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Figure 17.10b
pH Effects: O2 Saturation• Bohr effect
• Lower pH increases O2 unloading
• Active tissues
• Produce more acid pH decreases intissues
• Decreased pH causes shift right insaturation curve
• More O2 is unloaded to tissues
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A Functional Comparison of Fetal
and Adult Hemoglobin
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Carbon Monoxide• Hemoglobin has greater affinity for carbon monoxide (CO) than for
oxygen
• Prevents oxygen from binding to hemoglobin
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• 7% dissolved in plasma
• 70% carried as carbonic acid
• buffer system
• 23% bound to hemoglobin
• carbaminohemoglobin
• Plasma transport
Carbon dioxide transport
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Carbon Dioxide Transport in
Blood
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CO2
+ H2
O H2
CO3
H+ + HCO3
-
CA
Carbonic Anhydrase
• Enzyme that converts carbon dioxide and water to
carbonic acid
• Law of Mass Action: An increase in CO2 causes an
increase in bicarbonate and hydrogen ions
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CO2 Exchange: Tissues
Figure 17.11a
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CO2 Exchange: Lungs
Figure 17.11b
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PO2 Effect on CO2 Transport
Figure 17.12
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Figure 17.13a
Tissues: CO2
Loading/O2
Unloading
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Figure 17.13b
Lungs: CO2 Loading/O2
Unloading
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• Driven by differences in partial pressure
• Oxygen enters blood at lungs and leaves at tissues
• Carbon dioxide enters at tissues and leaves at lungs
Summary of gas transport
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A Summary of the Primary Gas
Transport Mechanisms
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PCO2, sistem buffer & pH
darah
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Analisis gas darahpH darah = 7.3
pCO2 = 50 mmHg
[HCO3-] = 35 mM
Dx : asidosis respiratorik
Urine pH ~ 6.0
Blood pH = 7.35 - 7.45
Blood [HCO3-] = 24 mM
Blood PCO2 = 45 - 35 mmHg
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Respiratory compensation for metabolic acidosis
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BMJ Acute Medical Emergency
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Tissue Respiration
Oxygen release and CO2 pick up at the tissue level.
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Cellular Respiration
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Pengendalian Respirasi
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Kendali napas : ventilasi• Kendali napas mempengaruhi ventilasi
• Pusat kendali terdapat pada :
• Medulla oblongata : rhythmic of breathing
• Pons : frekuensi dan intensitas napas
• Pusat fungsi luhur : sistem limbik
• Input : perubahan mekanik, pH darah, PCO2, PO2, emosi
• Receptor : mechano & chemoreceptor
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Control centersin the brain
regulate
breathing
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Neural control
• Respiratorycenters
• In hindbrain
• - medullaoblongata
• - pons
• Automaticbreathing
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Pacemaker di Medulla• Dorsal respiratory group (DRG) : Rhythmic Inspiratory
neuron
• Diafragma + m.intercosatlis externa.
• Ventral respiratory group (VRG) : forced respiratory neuron
• E neuron : m.intercostalis interna dan otot abdomen
• I+ neuron m.sternocleidomastoideus.
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Neural control
• I neurons = inspiration
• E neurons = expiration
• I neurons -> spinal motorneurons -> respiratorymuscles.
• E neurons inhibit I neurons.
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Neural control
• Also
• voluntary breathing controlled by the
cerebral cortex.
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Rhythmic of breathing
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Peripheral chemoreceptorsregulating respiration
• Aortic bodies*
• On aorta
• Send sensory info to medulla
through X (vagus n)
• Carotid bodies+• At fork of common carotid
artery• Send info mainly through IX
(glossopharyngeal n)
*
+
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Chemoreceptors
• Oxygen: large “reservoir” attached
to hemoglobin.
• So chemoreceptors are more
sensitive to changes in PC02(as
sensed through changes in pH).
• Ventilation is adjusted to maintain
arterial PC02 of 40 mm Hg.
•Chemoreceptors are locatedthroughout the body (in brain and
arteries).71
CO2, O2 DAN pH MEMPENGARUHI VENTILASI
• Chemoreceptor :
• Perifer : carotid dan aortic bodies
• Central : Ventral medulla
• Carotid dan aortic bodies peka thd :
• pH dan PCO2
• PO2 (< 60 mmHg)
• Central chemoreceptor peka thd PCO2 bukan [H+] dan pH
, mengapa …?
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• K channel pada membran sel
Glomus peka thd PO2
• PO2 sensor kanal K
permeabelitas ion K ion
K sulit keluar depolarisasi
memanjang
• Potensial aksi memanjang
neurotramisi inspirasi
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Mechanoreceptor• Input : iritan & hyperinflation
• Bahan iritan terhirup iritasi mukosa sensoris SSP
parasimpatik brochiolus konstriksi
• Hering–Breuer inflation reflex
Vol tidal > 1 lt stretch receptor brainstem inspirasi stop
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