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Hypoxia: types & effects, Cyanosis, Hypercapnia , Dyspnea , Asphyxia

Hypoxia: types & effects, Cyanosis, Hypercapnia , Dyspnea , Asphyxia. By Dr. Roomi. TYPES OF HYPOXIA:. There are 4 types of hypoxia: Hypoxic Hypoxia Anemic Hypoxia Stagnant / Ischemic Hypoxia Histotoxic Hypoxia. HYPOXIC HYPOXIA:. Causes :

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Hypoxia: types & effects, Cyanosis, Hypercapnia , Dyspnea , Asphyxia

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  1. Hypoxia: types & effects, Cyanosis,Hypercapnia, Dyspnea, Asphyxia By Dr. Roomi

  2. TYPES OF HYPOXIA: There are 4 types of hypoxia: • Hypoxic Hypoxia • Anemic Hypoxia • Stagnant / Ischemic Hypoxia • Histotoxic Hypoxia

  3. HYPOXIC HYPOXIA: Causes: • High altitude  decreased PO2 in atmospheric air. • Respiratory muscle paralysis. • Obstructive lung disease (COPD). • Restrictive lung disease (pulmonary fibrosis, pneumothorax). • Depression of respiratory centre (disease/ drug). Effect on arterial PO2: • Decreased arterial partial pressure of oxygen. MCQ • In other types of hypoxia, PO2 is normal.

  4. Clinical features of Hypoxic Hypoxia: • Due to decrease arterial PO2  Interstitial cells in peritubular capillaries of kidney secrete Erythropoietin  polycythemia • Hypoxia  pulmonary V.C  Pulm. Hypertension  Rt. Vent. Hypertrophy  Rt. Vent. Failure. TREATMENT: O2 treatment is most effective in this type of hypoxia.

  5. ANEMIC HYPOXIA: • Arterial PO2 is normal but inadequate O2 carrying capacity of blood. • Causes: • decrease in Hbconc. • abnormal Hblike met-Hb or Hb-S • CO poisoning: binding site of Hb for oxygen is not available

  6. CO Poisoning • CO is produced by incomplete combustion of carbon. • CO is a colorless & odourless gas. • Hbhas 250 times more affinity to bind with CO as compared to O2. • Carbon monoxide Hb shifts the oxy-Hb curve to left  O2 dissociation becomes difficult. • CO also inhibits cytochrome. • In CO poisoning, skin is cherry red colored. • There is no stim. of resp. centre, because arterial PO2 is normal. • When there is 70% carbon monoxyHb in blood  death occurs.

  7. Treatment of CO Poisoning: • Remove the subject from source of exposure. • 100% oxygen therapy can help. • Hyper-barric O2can help (O2 with increased pressure = 2-3 atm)

  8. STAGNANT / ISCHEMIC HYPOXIA: CAUSES: • Decreased cardiac output / sluggish blood flowdue to: • heart failure, • hemorrhage, • circulatory shock and • venous obstruction. • EFFECTS: • Blood remains in tissues for longer time, so tissue extracts increased oxygen from blood more AV difference of oxygen concentration. • So, PCO2 increases, it facilitates unloading of oxygen from hemoglobin (shifts the oxy-hemoglobin association dissociation curve to right).

  9. HISTOTOXIC HYPOXIA:(poverty amongst plenty) DEFINITION: Inability of the tissues to utilize oxygeninspite of normal arterial PO2 and oxygen carrying capacity. CAUSES: • Cyanide poisoning (it inhibits cytochromeoxidases oxidative process is inhibited). • Narcotic overdosage(it inactivates the enzyme dehydrogenase inhibition of tissue oxygenation). • Beri-beri (it is deficiency of thiamine co-enzyme which is required for many oxidative reactions). TREATMENT: • Methylene blue or nitrites. These convert hemoglobin  met-hemoglobin. • Cyanide + met-hemoglobin cyn-met-hemoglobin (non-toxic compound).

  10. CYANOSIS: • Definition: Bluish discoloration of skin& mucus membrane, when conc. of deoxy-Hb in small blood vessels like capillaries > 5 g/dl.

  11. 1. Peripheral: Seen on: exposure to moderate cold & in case of stagnant hypoxia. Seen in: fingers, outer surface of lips. Arterial PO2 remains normal. Types of Cyanosis:

  12. Types of Cyanosis: 2. Central: • Seen in : • case of Congenital heart diseases & • chronic lung disease. • Mostly Arterial PO2 is below normal (due to hypoxic hypoxia).

  13. Conditions in which Cyanosis does not occur: • Severe anemia (less than 5 gram deoxyHb/dl) • CO poisoning (masked due to cherry red complexion) • Met-Hemoglobinemia (chocolate brown discoloration)

  14. DYSPNEA = Air Hunger Dyspnea: shortness of breath (SOB), or air hunger, is the subjective symptom of breathlessness. 3 factors that cause the sensation of dyspnea: 1) Abnormality of respiratory gases in body fluids (mainly hypercapnia & partly hypoxia) 2) Increase work of breathingby respiratory muscles to breath forcefuly e.g. in asthma 3) State of Mind (neurogenic/emotional dyspnea) • More enhanced in people who are claustrophobic (fear of not being able to receive a sufficient quantity of air e.g., small or crowded places).

  15. HYPERCAPNIA: DEFINITION: • Excess CO2 in body fluids. • (Hypercapnia + Hypoxia): Only when hypoxia is caused by hypoventilation or circulatory deficiency.

  16. Causes of hypoxia + hypercapnia (simultaneously): • In hypoxia due to hypoventilation, CO2 transfer between alveoli & atmosphere is affected as much as is oxygen transfer. • In circulatory deficiency  decreased blood flow  decreased removal of CO2 from the tissues  tissue hypercapnia + hypoxia. • But transport capacity of blood for CO2 is more than 3 times that for O2, so resulting tissue hypercapnia in much less than tissue hypoxia.

  17. Severe hypercapnea • When alveolar PCO2 rises above about 60-75 mm Hg  air hunger / dyspnea becomes severe. • If PCO2 rises to 80-100 mm Hg  lethargy, +/- semicomatose • If PCO2 rises to 120 to 150 mm Hg  + / - anesthesia & death • At such high PCO2  Resp. Centre is depressed rather than stimulated  vicious circle

  18. ASPHYXIA: DEFINITION: Simultanoeus acute hypoxia & hypercapnia. CAUSES: • Acute airway obstruction • When a person is forced to re-breathe his own air in a confined space.

  19. Mechanism: • During asphyxia  hypoxia + hypercapnia strong stimulation of respiratory centre & violent inspiratory efforts  heart rate increases, BP increases, CATS increase from adrenal medulla (increase in nor-epinephrine > epinephrine)   unconsciousness, convulsions & decrease in respiratory rate  death.

  20. O2 THERAPY: (3 ways) Intra-nasal tube O2 mask on nose O2 tent (newborn)

  21. Oxygen therapy is helpful in: • Most helpful in hypoxic hypoxia. • May be helpful in cyanide or CO poisoning • May be helpful in case of Gas Gangrene. • Note: No use in Anemic & Ischemic (stagnant) hypoxia.

  22. OXYGEN TOXICITY If 100% O2 treatment is given for over 8 hours: If 100% O2 treatment is given for 24-48 hrs: Toxic effects start like: lung damage, decreased ability of alveolar macrophages to kill bacteria, decrease in surfactant secretion, cyst formation in lung may occur, Retrolentalfibroplasia in infants kept in O2 tents for long.  Features of airway irritation • sore throat • substernal distress • nasal congestion • coughing

  23. Cause of toxic effects of oxygen: • When O2 is given for longer period  toxic effects. • Formation of certain free radicals: • Super-oxide ions (O2-) • Hydrogen peroxide (H2O2) • Prevention of toxic effects of oxygen: • By anti-oxidants like vitamin E.

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