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Hypoxia , Asphyxia , and Cyanosis

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Hypoxia , Asphyxia , and Cyanosis ﺼﺩﻕﺼﺩﻕ ﺍﺍﷲﷲ ﺍﻟﻌﺍﻟﻌﻅﻅﻴﻡﻴﻡ ﺍﺍﻻﻻﺴﺴﺭﺍﺀﺭﺍﺀ ﺍﻴﺔﺍﻴﺔ 5588 HHypypoxoxiaia ,, AAsspphhyxyxiaia ,, anandd CCyanosiyanosiss HypHypoxiaoxia Def: •• Hypoxiaxia means O2 deficiency at tissue level resulting from disturbance in respiratory processes. •Hypoxemia → ↓ O2 content and PO2 in arterial blood. •• Remember:ber: •• Respiration is the process of transport of atmospheric oxygen to tissues and carbon dioxide from tissues to atmosphere. •• It is divided into 3 divisions;s; I- External Respiration •Pulmonary ventilation •Gas exchange II- Intermediate respiration: •Transport of gases by blood III - Internal Respiration Oxidation of food with release of energy HypHypoxiaoxia Types: It can be divided into: 1) Disturbance in external respiration → Hypoxic hypoxia 2) Disturbance in respiratory function of the blood → •Anaemic hypoxia •Stagnant hypoxia 3) Disturbance in internal respiration → Histotoxic hypoxia. Types and Causes of Hypoxia Hypoxic hypoxia Anaemic hypoxia Stagnant hypoxia histotoxic hypoxia Def., Hypoxia results from Hypoxia results from Hypoxia results from Hypoxia is due to defective oxygenation of deficiency of Hb in reduced tissue defect in internal arterial blood. amount or functions. perfusion respiration 1) ed PO2 in the 1)All types of anaemia 1)General: 1) Cyanide poisoning: Causes ↓ atmospheric air as in high 2)CO poisoning i. Shock. Cyanide blocks more altitude or breathing O2 3) MetHb ii.Congestive heart than 40 enzyme poor mixtures e.g. in 4) Sulph Hb failure. systems mainly mines. iii. Polythycemia. cytochrome oxidase 2) Ventilation defect: 2) Local: system. i. Obstructive disease e.g. ­Obstruction of blood 2) Alcoholic obstruction of the airway . vessels either from poisoning: ii. Restrictive disease e.g. inside by thrombus and Alcohol blocks pulmonary fibrosis . emboli or from outside. dehydrogenase 3)Gas exchange defect: enzyme.. i. Disease in respiratory ­ Peripheral vascular membrane: e.g. spasm e.g. Raynaud's ­↑ed thickness of the disease membrane. 4) Shunting of venous blood into arterial blood: e.g. congenital cyanotic heart disease. HyHyppeerrccaappnniaia Def.Def., -Hypercapnia means excess carbon dioxide in the body fluids. - Usually occurs in association with hypoxia only when the hypoxia is caused by hypoventilation or circulatory deficiency AsAspphhyxiayxia Def., It is a condition associated with CO2 excess, O2 lack and ↑ H concentration. Causes: 1.Occlusion of the air passage (drowning). 2.Paralysis of the respiratory ms (Poliomyelitis). 3.CO poisoning. 4.Inhibition of R.C. e.g. morphine poisoning. AsAspphhyxiayxia Stages., 1) Temporary slowing of respiration: It is due to ↑ed level of catecholamines which ↑ ABP→ reflex inhibition of respiration 2) Stage of hyperapnea: There is pronounced ++ of respiration with violent respiratory efforts. This is due ++ of chemoreceptors (central and peripheral) by excess CO2, O2 lack and ↑ H concentration. 3) Premortal stage: ­Respiration becomes deep and slow, then gasping then stops when R. C fails. ­Blood pressure falls and heart rate slows. -At this point, the person can be saved by artificial respiration because heart still beats for other few minutes. -If artificial respiration is not started, cardiac arrest occurs in 4-5 minutes. CyanoCyanossisis Def, It is a blue colour of the skin and mucus membrane due to the presence of ↑ed amount of reduced Hb in the blood of superficial capillaries. CCyayannosisosis (CONT.) Threshold of cyanosis: -For cyanosis to occur there must be at least 5gm reduced Hb% in the capillary blood. - Normally, the arterial blood contains about 3% reduced Hb i.e. about 0.45 gm % (3x15). - The venous blood contains 30% reduced Hb i.e. 4-5 gm %( 30 x l5). - The capillary blood contain an a average value = 0.45 +4.5 gm = 2.5 gm 2 CCyayannosisosis (CON(CONTT.).) Causes of cyanosis: 1)Defective blood oxygenation or it's stagnation at tissue i.e. •Hypoxic hypoxia • Stagnant hypoxia. 2) Normally in moderate cold weather due to V.C. of skin arterioles. N.B. Cyanosis does not occur in: •Histotoxic hypoxia: Hb is either oxy Hb or cynoHb which is red in colour. •Anaemic hypoxia: It is due to reduced Hb content. •Carbon monoxide poisoning: Carboxy hemoglobin is cherry red in colour. CCyayannosisosis (CONT.) Types of cyanosis:: a)Central cyanosis: appears in skin and mucous membrane It occurs in: ­Hypoxic hypoxia. - Stagnant hypoxia. -Heart failure. b) Peripheral cyanosis: appears only in periphery (skin) This type of cyanosis results from impaired peripheral circulation e.g. due to thrombus or emboli in the blood vessels or V.C. TTTHHHAAANNNKKKSSS Abdel A ziz H ussein , Ma nsou ra Un ive rsity, Mans oura, E gypt.
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