resspiratory failure lms Flashcards
type 1 respiratory failure
hypoxaemia
gas exchange failure
type 2 failure
hypercapnia
ventilatory failure
caauses of hypoventilation
brainstem - stroke, encephalitis, drugs
spinal cord - trauma
anterior horn cell - motor neurone disease, poliomyelitis
nerves - GBS
neuromuscular junction - myasthenia gravis
muscle - muscular dystrophies, muscle relaxants
chest well - obesity, kyphoscoliosis
lung and airways - COPD, brnchiectasis, thymoma
factors decreasing respiratory drive
sedatives, opioids, anaasthesia
sleep and sleep disruption
excess O 2
rare = diseases of medulla, eg. stroke, trauma, encephalitis
sleep hypoventilation
sleep in a healthy individual: basal metabolic rate declines, alveolar ventilation declines more, PaCO2 rises by 2-4mmHg
PaCO2 rises by > 10mmHg = sleep hypoventilation
diagnosis of type 2 resp failure
variable symtpoms
orthopnoea - cant lie flat
thoracic abdominal paradox
shortness of breath
alteration in rate and depth of breathing
accessory muscle use
symptoms and signs of CO2 retention
poor sleep quality
morning headahce
day time fatigue and sleepiness
cenrtral nervous system - decreased conscious state
invasive ventilation
ETT/tracheotomy
non-invasive ventilation
negative pressure ventilation (eg. during polio epidemics)
positive pressure ventilators (e.g VPAP, bipap)
why not CPAP
doesnt ventilate - splints upper airways and bronchial airways
nocturnal NIV
non invasive ventilation
improves outcomes in chronic type 2 resp failure
VQ mismatch
ddx of hypoxia
atmospheric oxygen presssure eg. altitude
shunt (pulmonary arteriovenous fistulas, congenital heart disease)
hypoventilation (ie. secondary to severe type 2)
acute lung disease causing hypoxia
infections, cardiac failure (pulmonary oedema
pulmonary embolism
exoossure to inhaled toxic substances
chronic lung disease causing hypoxia
COPD, cystic fibrosis, interstitial lung dissease, pulmonary vascular disease
treatment of type 1 respiratory failure
supplimental oxygen
CPAP/NIV
invasive ventilation
ECMP (extra corporeal membrane oxygenation)
treat underlying condition
nasal cannula
convenient - patient can still talk and eat and drink
variable FiO2
low oxygen requirements including home use
usually dont go higher than 4L/min
hudson mask
5-10L/min flow
higher FiO2 40-60%
non rebreather mask
reservoir bag collects. exhaled gas
40-90% FiO2
inadequate humidifications
patients with chronic lung disease
severe chronic lung diease when CO2 is chronically raised, ie. loss of most stimulus to ventilation form CO2
hypoxic drive to ventilation becomes very important
ie. arterial hypoxaemia becomes the cheif stimulus to ventilation
high oxygen concentrations to relieve hypoxia can cause depressed breathing
ventilation can be dangerous for
people with chronically raised Co2 levels eg. acute on chronic COPD
venturi devices
reliable FiO2
humidification not necessary
HFNC
high flow nasal cannula
heats, humifidies and delivers high flow oxygen
30-60L/min
FiO2 up to 100%
well tolerated due to humidification
minimal dilution with room air (precise FiO2)
blood pH in patients with hypercapnia
normal pH suggests chronic CO2 retention while a low pHraises concern for acute or acute on chronic CO2 retention, which requires immidiate intervention ie. respsiratory acidosis
