Types of hypoxia Flashcards
Hypoxia definition
inadequate oxygen in a particular part or all of the body or at cellular level
often pathological
variations in arterial oxygen concentrations can be part of the normal physiology - hypoventilation training or strenuous exercise
what is anoxia?
no oxygen at all
classification of hypoxia
generalised
local
types of hypoxia
inadequate oxygenation of blood in lungs pulmonary disease venous to arterial shunts inadequate O2 transport to tissues inadequate tissue use of oxygen
inadequate oxygenation of blood in lungs
hypoventilation
altitude hypoxia
altitude hypoxia
barometric pressure of atmosphere is lower
oxygen molecules in air are further apart so oxygen content is lowered
reduction of available oxygen in the air at height reduces oxygen saturation in blood
what is hypoxaemia ?
decreased availability of O2 in inhaled air
hypoventilation
neurological weakness
trouble with bellows - movement of air
central drive of respiration centre suppressed
what causes hypoventilation
opiate overdose motor neuron disease severe neuropathy muscle weakness multiple system atrophy
pulmonary disease
airway resistance - asthma
failure of respiratory membrane diffusion
volume of oxygen getting to airways is reduced
gas exchange failure - alveolar dysfunction or membrane dysfunction
venous-arterial shunt
cardiac shunt
cyanotic congenital heart disease
mixing of arterial and venous blood
only occurs when right sided heart pressure increases and blood shunts from right to left
inadequate O2 transport to tissues
decreased carrying capacity - low Hb - anaemia
generalised circulatory failure - shock
localised circulatory failure - acute MI or stroke
cyanotic congenital heart disease
tetralogy of fallot
transposition of great arteries
ASD/VSD
anaemia
less O2 carriage to tissue
measure oxygen saturation
less oxygen for target tissues/ organ/ cells
oxygen saturation
% of which haemoglobin is saturation with oxygen
inadequate tissue use of oxygen
burns
CO poisoning
red colour
not cyanotic
oxygen sats appear unaffected
what can cause cyanide toxicity?
burning rubber pesticides battery manufacturing gold mining jewellery cleaning plastic, nylon and fumigant manufacturing almonds
who gets cyanide toxicity?
35% of fire victims
symptoms/ signs of cyanide toxicity
cyanosis low GCS normal oxygen saturations lactic acidosis low BP low HR high RR depressed mental activity - confusion and coma tissue and cell death - ischaemia reduced work capacity of muscles
treatment for cyanide toxicity
amyl nitrate and sodium thiosulfate and sodium nitrate
goal to create methaemoglobin
hydroxocobalamin infusion - vitamin B12
oxygen therapy
helpful if O2 is deficient
if alveolar O2 is increased O2 pressure gradient is increased
type 1 respiratory failure
hypoxaemia - PaO2 <8kpa
normocapnia - PaCO2 <6kpa
pathogenesis of type 1 respiratory failure
associated with damage to lung tissue which prevents adequate oxygenation of blood
remaining normal lung is sufficient to excrete carbon dioxide
what causes type 1 respiratory failure?
low ambient oxygen/high altitude ventilation-perfusion mismatch - PE alveolar hypoventilation diffusion problems - pneumonia/ARDS right - left cardiac shunt
type 2 respiratory failure
hypoxaemia - PaO2 <8kpa
hypercapnia - PaCO2 >6kpa
pathogenesis of type 2 respiratory
due to alveolar hypoventilation
unable to get O2 into blood and CO2 out of it
causes of type 2 respiratory failure
increased airway resistance reduced breathing effort decrease in area of lung available for gas exchange neuromuscular problems deformed/rigid/flail chest
what causes increased airway resistance?
COPD
asthma
suffocation
what causes reduced breathing effort?
drugs
brainstem lesion
extreme obesity
what causes a decrease in area of lung available for gas exchange
chronic bronchitis
what causes neuromuscular problems?
guillain-barre syndrome
motor neuron disease
what causes deformed/rigid/flail chest?
kyphoscoliosis
ankylosing spondylitis
how to treat respiratory failure
administer oxygen
mechanical ventilation
treat underlying condition - bronchodilators, steroids, antibiotics etc.
different types of oxygen administration
venturi mask - 24%
rebreathe mask - 100%
when can oxygen therapy be useful?
when there is inadequate oxygenation of blood
pulmonary disease
how is respiration controlled?
central chemoreceptors
peripheral chemoreceptors
brainstem respiratory centres adjust rate and depth of respiration accordingly
central chemoreceptors
respond to arterial PaCO2
peripheral chemoreceptors
respond to PaCO2 and pH
what should PaO2 be on oxygen?
should be 10kpa less than the % inspired O2 concentration
what is anxiolysis?
level of sedation in which a person is relaxed and may be awake, caused by drugs
to help relieve anxiety
minimal sedation
clinical features of COPD
chronically hypoxic chronically retain CO2 high CO2 and bicarbonate smoking history gaunt cachectic dyspnoea minimal cough increased minute ventilation pink skin pursed lip breathing accessory muscle use hyperinflation barrel chest decreased breath sounds tachypnoea
complications of COPD
pneumothorax due to bullae and weight loss due to work of breathing
management of COPD
no longer rely on detecting high levels of CO2 in their blood to stimulate respiration rather they rely on hypoxic drive
need careful oxygen management - venturi devices
target oxygen sats of 88-92% to avoid loss of ventilation stimulation which would cause hypercapnia and acidosis
what to do if someone with COPD becomes acidotic with low O2 and high CO2
non-invasive ventilation
clinical features of chronic bronchitis
chronic productive cough purulent sputum haemoptysis mild dyspnoea initially cyanosis hypoxaemia peripheral oedema - cor pulmonale crackles wheezes prolonged expiration
complications of chronic bronchitis
secondary polycythemia vera due to hypoxaemia
pulmonary hypertension due to reactive vasoconstriction from hypoxaemia
cor pulmonale from chronic pulmonary hypertension
asthma attack
inhalers not working raised respiratory rate tachycardia low PaO2 low PaCO2 normal pH
opioid toxicity clinical features
reduced GCS reduced respiratory rate reduced ventilation high CO2 and low O2 pinpoint/ small pupils acidotic on ABG
risk factor for opioid toxicity
excreted renally so CKD/ impaired renal function
management for opioid toxicity
naloxone, corrects GCS
pulmonary embolism
increases pulmonary vascular resistance decreased RV output reduced LV preload fall in CO hypoxia occurs due to VQ mismatch
VQ mismatch in PE
reduced perfusion with normal ventilation
treatment for PE
LMWH warfarin DOAC thrombolysis clot extraction
guillain barre syndrome
acute inflammatory neuropathy
often have a history of gastronenteritis or flu-like illness weeks before onset of neurological symptoms
clinical features of guillain barre syndrome
bilateral affects distal extremities first prior to progression 1/3 will experience respiratory failure requiring ventilation and airway protection hypercapnia and hypoxia are late signs falling oxygen sats low PaO2 high PaCO2 impending respiratory arrest
testing in Guillain barre syndrome
regular spirometry to observe respiratory effort
nerve conduction studies and lumbar puncture should be done
lumbar puncture will show high protein
pathogenesis of guillain barre syndrome
gastroenteritis or flu-like illness triggers an immune mediated attack on myelin sheaths due to molecular mimicry
affects the motor and sensory nerves
pneumonia presentation
high PaCO2
low PaO2
reduced alveolar expansion - hypoventilation
crepitations at base
treatment for pneumonia
IV antibiotics IV fluids oxygen analgesia chest physio
