Top Banner
Hy Hy poxia poxia
23

Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

Jan 03, 2016

Download

Documents

Mark Wade
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Page 1: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

HypoxiaHypoxia

Page 2: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

ConceptConcept

Oxgen supply = CaO2× Q

Oxygen consumption = ( CaO2 - CvO2 ) × Q

Tissue cells can’t obtain enough oxygen

or can’t fully utilize oxygen

metabolic, functional and structural changes

Page 3: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

CO2 - dissolved O2

CO2maxO2 saturation ( SO2 ) = ×100%

SaO2 95%, SvO2 70%

Parameters of blood gasParameters of blood gasPartial pressure of O2 ( PO2 ) PaO2 100mmHg , PvO2 40 mmHg O2 content ( CO2 ) = CO2max×SO2 + dissolved O2

CaO2 19ml/dl , CvO2 14ml/dl

O2 capacity ( CO2max ) = 1.34 ml/g × Hb g/dl

Page 4: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

Dissociation curve of oxyhemoglobinDissociation curve of oxyhemoglobin

Page 5: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.
Page 6: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

Classification, etiology and pathogenesisClassification, etiology and pathogenesis 1. 1. Hypotonic hypoxiaHypotonic hypoxia — — PaOPaO22↓ ↓

Causes : 1) PiO2↓

2) pulmonary dysfunction

3) shunt

Results : PaO2↓→ SaO2↓→ CaO2↓ hypotonic hypoxemia, cyanosis ( PaO2 - PMO2 )↓ →( CaO2 - CvO

2 )↓

PaO2 < 60mmHg → VO2↓ ?

Page 7: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

Results : CO2max↓↓ CaO2 ↓↓

( CaO2 - CvO2 ) ↓ P50 ↓ ( CaO2 - CvO2 ) ↓

2.2. Hemic hypoxia — COHemic hypoxia — CO22maxmax ↓

Causes : 1) anemia

2) carboxyhemoglobinemia

3) methemoglobinemia

enterogenous cyanosis

4) P50↓ : transfusion of depot blood

Page 8: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

Result : Q↓↓→ CvO2↓

→ ( CaO2 - CvO2 )↑

Causes : general circulatory failure

local circulatory disorder

3. 3. Circulatory H — Q↓Circulatory H — Q↓

··

Page 9: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

4. Histogenous hypoxia

Causes: 1) histotoxic H

cyanide poisoning

2) cell injured by biological or p

hysical factor

3) vitamin deficiency --- B1

Result : CvO2↑ → ( CaO2 - CvO2 )↓

Page 10: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

What kind of hypoxia might occur in

septic shock ?

Page 11: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

Hypotonic hypoxia

PaO2 < 60mmHg → compensation < 30mmHg → severe disturbances

Functional and metabolic alterationsFunctional and metabolic alterations

Page 12: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

1. 1. Respiratory systemRespiratory system

• Respiratory rate and depth ↑

arrive at 4000m high →ventilation ↑ 65%

few days later → ventilation ↑ 5 – 7 times

long residents → 15 % more than at sea level

• Hyperventilation→PaO2↑→CaO2 ↑

↘O2 consumption ↑

occur in any type of hypoxia?

Severe hypoxia→pulmonary edma

↘Inhibition of respiratory center

Page 13: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

2. 2. Circularory systemCircularory system

• Cardiac output↑ due to: 1. cardiac contractility↑ 2. heart rate↑ 3. venous return↑

• Redistribution of blood flow α-Adrenoceptor vasoconstriction Local metabolites vasodilation

Page 14: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

Pulmonary vasoconstriction (HPV)→PaO2 ↑

Sympathetic nerve

Humoral factors — AT 、 ET 、 LTs 、 TxA2

PGI2 、 NO 、 histamine

Direct effect of O2 on SMC — Kv

How to prove?

Capillary proliferation --- VEGF

Page 15: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

Severe hypoxia

• Myocardiac systolic and diastolic dysfunction

• Cardiac arrhythmia ---

Hypoxia acidosis hyperkalemia

Arrhythmia

• Venous return↓

• Pulmonary hypertention right ventricle

Page 16: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

3. 3. Hemic systemHemic system

• RBC↑--- erythropoitin • P50 ---- 2.3 - DPG↑

Page 17: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

4.4.Central nervous systemCentral nervous system

• Acute H → headache 、 impaired attention • Chronic H → sleepiness, depression

• Severe H → confusion, coma, convulsion

due to : energy deficiency and acidosis

decreased RMP

abnormal neurotransmitter synthesis

cell damage

vasodilation and cerebral edema

Page 18: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

5. 5. Cellular alterationsCellular alterations

AdaptationAdaptation

• Ability to use O2↑---

number of mitochondia , it’s enzymes

• Anaerobic glycolysis↑

ATP/ADP↓ → phosphofructokinase

activity

• Low metabolic state --- caused by acidosis

• Myoglobin↑

Page 19: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

Dissociation curve of oxymyoglobin and oxyhemoglobin

Page 20: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

• Cell membrane

decreased permeability + ion pump dysfunction

[ Na+ ]i → Cellular swelling

[ K+ ]i ↓ → Synthetic metabolism↓

[ Ca2+ ]i → Mitochondria damage

ROS

Lysosome damage

Severe H → Cellular damage

Page 21: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

• Mitochondria Respiratory function ↑ (PmO2< 1mmHg)

PmO2< 1mmHg dehydrogenase activity

• Lysosome Acidosis phospholipase activity

hydrolases release

Page 22: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

Factors influencing the tolerance to hypoxiaFactors influencing the tolerance to hypoxia

• Oxygen consumption rate

• Compensatory ability to hypoxia

Page 23: Hypoxia Hypoxia. Concept Oxgen supply = CaO 2 × Q Oxygen consumption = ( CaO 2 - CvO 2 ) × Q Tissue cells can’t obtain enough oxygen or can’t fully utilize.

Oxygen therapy and oxygen intoxication

Oxygen intoxication --- PO2> 0.5 atm

• Cerebral type --- visual and auditory

dysfunction , nausea, convulsion and coma

How to differentiate it from hypoxic encephalopathy?

• Pulmonary type --- cough, dyspnea

vital capacity , PaO2