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Slide 1
Hypoxia: types & effects, Cyanosis, Hypercapnia, Dyspnea,
Asphyxia By Dr. Roomi
Slide 2
TYPES OF HYPOXIA: There are 4 types of hypoxia: 1.Hypoxic
Hypoxia 2.Anemic Hypoxia 3.Stagnant / Ischemic Hypoxia 4.Histotoxic
Hypoxia
Slide 3
HYPOXIC HYPOXIA: Causes: 1.High altitude decreased PO 2 in
atmospheric air. 2.Respiratory muscle paralysis. 3.Obstructive lung
disease (COPD). 4.Restrictive lung disease (pulmonary fibrosis,
pneumothorax). 5.Depression of respiratory centre (disease/ drug).
Effect on arterial PO 2: Decreased arterial partial pressure of
oxygen. MCQ In other types of hypoxia, PO 2 is normal.
Slide 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.
Slide 5
ANEMIC HYPOXIA: Arterial PO2 is normal but inadequate O2
carrying capacity of blood. Causes: 1.decrease in Hb conc.
2.abnormal Hb like met-Hb or Hb-S 3.CO poisoning: binding site of
Hb for oxygen is not available
Slide 6
CO Poisoning CO is produced by incomplete combustion of carbon.
CO is a colorless & odourless gas. Hb has 250 times more
affinity to bind with CO as compared to O 2. 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 PO 2
is normal. When there is 70% carbon monoxy Hb in blood death
occurs.
Slide 7
Treatment of CO Poisoning: Remove the subject from source of
exposure. 100% oxygen therapy can help. Hyper-barric O 2 can help
(O 2 with increased pressure = 2-3 atm)
Slide 8
STAGNANT / ISCHEMIC HYPOXIA: CAUSES: Decreased cardiac output /
sluggish blood flow due 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, PCO 2 increases, it
facilitates unloading of oxygen from hemoglobin (shifts the
oxy-hemoglobin association dissociation curve to right).
Slide 9
HISTOTOXIC HYPOXIA: (poverty amongst plenty) DEFINITION:
Inability of the tissues to utilize oxygen inspite of normal
arterial PO2 and oxygen carrying capacity. CAUSES: Cyanide
poisoning (it inhibits cytochrome oxidases 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).
Slide 10
CYANOSIS: Definition: Bluish discoloration of skin & mucus
membrane, when conc. of deoxy-Hb in small blood vessels like
capillaries > 5 g/dl.
Slide 11
Types of Cyanosis: 1. Peripheral: Seen on: exposure to moderate
cold & in case of stagnant hypoxia. Seen in: fingers, outer
surface of lips. Arterial PO 2 remains normal.
Slide 12
Types of Cyanosis: 2. Central: Seen in : case of Congenital
heart diseases & chronic lung disease. Mostly Arterial PO 2 is
below normal (due to hypoxic hypoxia).
Slide 13
Conditions in which Cyanosis does not occur: Severe anemia
(less than 5 gram deoxy Hb/dl) CO poisoning (masked due to cherry
red complexion) Met-Hemoglobinemia (chocolate brown
discoloration)
Slide 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 breathing by 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).
Slide 15
HYPERCAPNIA: DEFINITION: Excess CO 2 in body fluids.
(Hypercapnia + Hypoxia): Only when hypoxia is caused by
hypoventilation or circulatory deficiency.
Slide 16
Causes of hypoxia + hypercapnia (simultaneously): In hypoxia
due to hypoventilation, CO 2 transfer between alveoli &
atmosphere is affected as much as is oxygen transfer. In
circulatory deficiency decreased blood flow decreased removal of CO
2 from the tissues tissue hypercapnia + hypoxia. But transport
capacity of blood for CO 2 is more than 3 times that for O 2, so
resulting tissue hypercapnia in much less than tissue hypoxia.
Slide 17
Severe hypercapnea When alveolar PCO 2 rises above about 60-75
mm Hg air hunger / dyspnea becomes severe. If PCO 2 rises to 80-100
mm Hg lethargy, +/- semicomatose If PCO 2 rises to 120 to 150 mm Hg
+ / - anesthesia & death At such high PCO 2 Resp. Centre is
depressed rather than stimulated vicious circle
Slide 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.
Slide 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.
Slide 20
O 2 THERAPY: (3 ways) O2 mask on nose Intra-nasal tube O2 tent
(newborn)
Slide 21
Oxygen therapy is helpful in: 1.Most helpful in hypoxic
hypoxia. 2.May be helpful in cyanide or CO poisoning 3.May be
helpful in case of Gas Gangrene. Note: No use in Anemic &
Ischemic (stagnant) hypoxia.
Slide 22
OXYGEN TOXICITY If 100% O 2 treatment is given for over 8
hours: Features of airway irritation sore throat substernal
distress nasal congestion coughing If 100% O 2 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, Retrolental
fibroplasia in infants kept in O 2 tents for long.
Slide 23
Cause of toxic effects of oxygen: When O 2 is given for longer
period toxic effects. Formation of certain free radicals:
1.Super-oxide ions (O 2 -) 2.Hydrogen peroxide (H 2 O 2 )
Prevention of toxic effects of oxygen: By anti-oxidants like
vitamin E.