Oxygen and resp failure Flashcards
type 1 resp failure
short of oxygen
type 2 resp failure
short of oxygen
too much CO2
hypoventilation leads to _____ which leads to _____
hypoxaemia
hypercabia
if in doubt regarding type of resp failure what should be carried out
blood gas
primary hypoxia bad lungs
low pO2/ high pCO2/ normal HCO3 acidosis low pO2/ high pCO2/ high HCO3 virus low pO2/ very high pCO2/ high HCO3 acidosis
anaesthetic opinion on giving O2
hypoxia = bad hypoxia = kills you hypoxaemia = main cause of hypoxia reverse all hypoxia CO2 worry about later
chest physician opinion on giving O2
type 2 resp failure = very common
hypercarbia = damaging
O2 poisons
stop O2
oxygen in A + E
all O2
oxygen in AMU
controlled O2
oxygen in ICU
all O2 again
prescribing O2
O2 = drug
always ensure = prescribed
1st rule =
only give O2 if risk/ benefit ratio is in favour of O2
some people = very sensitive to O2
as pO2 rises =
pCO2 rises
- acidosis
- can be severe
- can be life threatening
bad lungs =
low pO2/ high pCO2/ normal HCO3 acidosis low pO2/ high pCO2/ high HCO3 O2 given high pO2/ very high pCO2/ high HCO3 acidosis
COPD patients T2RF
high risk of developing it
1/5 COPD patients
Areas of poor ventilation =
reactive vasoconstriction
excess O2 + reactive vasoconstriction = reserves
perfusion = good
ventilation = poor
effect of pCO2 on haemoglobin
haldane effect
-O2 can displace CO2 from Hb
bohr effect
-high concn of CO2 = prevent O2 binding to Hb
pCO2 Bohr Effect
shifts dissociation curve
Theory of Hypoxic Drive
normal respiration = driven by CO2 chemoreceptors
chronic hyperbia = destination of receptors
O2 chemoreceptors = primary respiration drive
Treat Hypercarbia
Conservative O2 management SaO2 88-92% increase Vminute -RR = usually already high -increase Vt with NIV
Severe hypoxaemia
Altered mental state Cyanosis Dyspnoea tachypnoea Arrhythmias -tissue hypoxia
pO2<5.3kPa = hyperventilation increases dramatically
- 3kPa = loss of consciousness
- 7kPa = death
circulatory hypoxia
O2 blood needs to get to tisses
global reduction - circulatory hypoxia
heart failure
local reduction - circulatory hypoxia
obstruction of vessels
oedema
compression
compartment syndrome
types of hypoxia
circulatory hypoxia
anaemic hypoxia
toxic hypoxia
hypoxaemic hypoxia
hypoxaemic hypoxia
low inspired O2 concn
impaired diffusion
failure of alveolar - endothelial surfaces
interstitial thicking
pulmonary fibrosis
lymphangitis
sarcoidosis
vascular dysfuction
pulmonary vasculitis
endothelial malignancy
what is required for transfer of O2 from airway to blood
adequate perfusion
adequate ventilation
perfusion without ventilation
shunting
ventilation without perfusion
dead space
lung apex
good v
poor Q
lung base
poor V
good Q
where should perfusion be directed
areas of best ventilation
steps patient = hypoxia
which bit = failing cardiac output haemoglobin poisoning then lungs
patient = hypoxaemia
O2 given (not for breathlessness) reversal hypoxaemia = not always beneficial high flow/ concn O2 = rarely beneficial
high flow, high concn O2 therapy used for
cluster headaches
CO poisoning
pneumothorax - no chest drain
sickle cell crisis
If SaO2 greater than or equal to 90%
no O2
COPD SaO2
88-92%
90-94%
everything bar COPD
Vmin =
Vt x RR
Vmin @ rest
5-40l
Vmin when unwell
400l
nasal cannulae
well tolerated
low flow only
uncontrolled FiO2
Nasal breathing dependent
variable performance mask
cheap and simple
5-15l/min
uncontrolled fiO2
unable to cope with high flow requirements
venturi mask
fixed performance
flows of up to 250 l/min
non-rebreathing mask
up to 85% FiO2 uncontrolled fiO2 flow limited to outflow of wall beware large Vt Indications for mask = now very few (CO poisoning, PTX, cluster headaches, sickling crisis)
