Respiratory failure Flashcards
what is respiratory failure
the respiratory system fails to oxygenate the arterial blood adequately and/ or fails to prevent CO2 retention
causes of respiratory failure
abnormalities in airways/alveoli and blood supply system (pneumonia and COPD)
the CNS- control of respiratory system (motor neuron disease), PNS (GBS), respiratory musculature (thoracotomy muscular dystrophy), chest wall dynamics (rib fracture)
consequences of respiratory failure
respiratory and all muscles fatigue, hypoventilation, sputum retention, hypoxaemia
consequences of respiratory failure- if left
cardiac arrhythmias, cerebral hypoxaemia, respiratory acidosis, CO2 necrosis, coma, cardiac arrest
types of respiratory failure- how are they classified?
classified as hypoxaemic or hypercapnic and may be either acute or chronic
types of respiratory failure- type 1
type 1 failure or hypoxemic respiratory failure is characterised by PaO2 of less than 8KPa with a normal or low PaCo2. disorders of diffusion are a problem with oxygenation
types of respiratory failure- type 2
type II respiratory failure is characterised by PaO2 of less than 8kPa (hypoxaemia) with an increase in Paco2 levels greater than 7kPa (hypercapnia)
what happens during respiration and what goes wrong
3 processes- transfer of O2 across the alveoli, transport oxygen to the tissues, removal of CO2 from blood into the alveolus and then into environment
in type 1- process 1 and 2 compromised, in type 2- all 3 components compromised
causes of type 1 respiratory failure
hypoxic hypoxaemia, ischemic hypoxaemia, anaemic hyperaemia, toxic hypoxaemia
what is hypoxic hypoxaemia
inability to transfer oxygen across the respiratory membrane, VQ mismatch, acute bronchoconstriction, insufficient inspired oxygen therapy, primary respiratory disease (pneumonia =, COPD/sputum retention, primary cardiac disease= heart failure
how does the SA of the lung reduce PP of oxygen
in the SA of the lung is reduced and the PP of oxygen is reduced, the diffusion decreases causing type 1 respiratory failure. if the respiratory membrane increases in thickness, diffusion is reduced= type 1
if severe enough it may affect CO2 diffusion as well and patients may present as type 2 respiratory failure
consequences of hypoxaemia- aneamic hypoxia and toxic hypoxaemia
oxygen carrying capacity of the blood, affinity, cardiac output, distribution of blood flow, oxygen used by cells, PaO2 not a good indicator alone
toxic- difficulty using oxygen, inhalation burns and simple inheritation, carbon monoxide poisoning, cyanide poisoning
consequences of hypoxaemia- ischemic and anaemic hypoxaemia
ischaemic- inadequate blood flow through the lung, pulmonary embolus, destruction of the lung capillaries
anaemic hypoxaemia- reduction in the O2 carrying capacity of the blood, shock (significant blood loss), primary blood disease sickle cell crisis/ anaemia
how long does tissue it take for tissue hypoxia to occur
brain= 3-5 mins, kidney and liver= 10-20 mins, skeletal muscle= 60-90 mins, vascular smooth muscle= 24 hours, hair and nails= days
type II respiratory failure
disorders of ventilation, caused by any disorders or pathology that affects ventilation, e.g. a change in any system that alters rate and depth of breathing causing decrease PPO2 and increase in PPCO2.
balance between strength (diminished drive, impaired neuromuscular transmission, muscle weakness) and load (chest wall abnormalities and airways/ lung abnormalities)
causes of type 2 respiratory failure
CNS depression/ abnormalities with the respiratory drive centres (opiates/alcohol/head injury), disorders of the spinal cord, abnormalities of the peripheral nerves, respiratory disease, neuromuscular disease, muscle weakness, loss of integrity of the chest wall/poor ventilatory mechanics
capacity or strength of respiratory muscles
hyperinflation, respiratory muscle fatigue, poor muscle oxygenation/ nutrition, general fatigue, over use of accessory muscles
load on respiratory muscles
increased airway resistance (airway collapse, sputum, bronchospasm), static and dynamic hyperinflation, intrinsic peep, increased resistance to airflow, increased elastic load
how do we treat respiratory failure
reverse the cause if possible.
type 1 causes- ischaemic/ anaemia and toxic hypoxaemia= involved from optimisation perspective, hypoxic= remove secretions and increase volumes
type 2= disorders of ventilation= offer support to respiratory system
what is hypoxaemia
lack of oxygen= give oxygen, it is often considered when our patients are in respiratory failure
types of hypoxaemia- oxygen therapy
mild hypoxaemia on air (9-10kPa)- nasal cannula 2-4L per min (28-36%) or mask (simple) 4L min (24-25%)
moderate hypoxaemia- <9Kpa (type 1 failure)- mask (simple)- 4-15 L/min (24-50%), Hi flow systems 6-15 L/mins
consequences of respiratory failure
hypoxic drive, instead of high levels of O2 causing an increase in rate and depth of breathing and low levels of O2 drive the respiratory pattern- too much O2 given then body thinks it has enough so stops breathing= cardiac arrest, CO2 levels start to rise because respiration has stopped, hypoxia kills, hypercapnia happens
what is oxygen therapy
is the admission of O2 at concentrations greater than those found in ambient air in order to treat or prevent hypoxaemia. it is a drug so must be prescribed according to a target solution range- must be monitored to ensure O2 administered keeps them within targeted range
improves oxygenation but it does not treat underlying cause of hypoxaemia
indications for O2 therapy
PaO2 <8Kpa or SaO2 <90% on room air and PaO2 or SaO2 below desirable range for a specific clinical situation
acute care situation in which hyperaemia is suspected, severe trauma, acute MI, short term therapy (post anaesthesia), decrease symptoms associated with chronic hypoxaemia, decrease the workload hypoxaemia imposes on cardiopulmonary system
complications of O2 therapy
oxygen toxicity- it causes lung fibrosis
depression of ventilation- get high levels of oxygen depressed respiratory drive, retinopathy of prematurity- complication of oxygen in babies (blind- causes vasodilation of blood vessels in retina- burst), fire hazard, atelectasis
starting and monitoring oxygen
oxygen should be prescribed prior to administration (accept in an emergency), oxygen therapy is started using an approprioate delivrey system and flow rate, O2 sats should be observed for first 5 mins after change in o2 therapy
oxygen sats documentation
documented with oxygen device, FiO2 and flow rate
assessing for oxygen therapy
pulse ox- non-onvasive and measures SpO2 only (no info on pH, PaCO2, haemoglobin levels)
ABG- gold standard test for respiratory failure, measure Pa02, pH, PaCO2, HCO3, SaO2, invasive
what is a variable- performance devices
amount of oxygen delivered is dependent on- O2 flow rate, patient inspiratory volume, RR
Types= nasal cannula, simple face mask, reservoir mask- partial re-breath mask and non-rebreathe
what is nasal cannula
a plastic disposable device consisting of 2 tips or prongs 1cm long, connected to oxygen tubing. inserted into a vestibule in nose. flow- 1/4 8L/min (adult) and <2L/min (child), maximum via nasal cannula= 35%
nasal cannula- advantages and disadvantages
advantages- easy to fix, keeps hands free, not much interference with further airway care, low cost, compliant
Disadvantages- unstable, easily dislodged, high flow uncomfortable, nasal trauma, mucosal irritation, FiO2 can be inaccurate and inconsistent
reservoir cannula- advantages and disadvantages
advantages- lower O2 use and cost, increased mobility, less discomfort because of lower flow
Disadvantages- unattractive, cumbersome, poor compliance, must be regularly replaced (3 weekly), breathing pattern affects performance (must exhale through nose to reopen reservoir membrane)
simple face mask
reservoir- 100-120ml, variable performance device, FiO2= o2 input flow, mask volume, extent of air leakage, patients breathing pattern, 40-60%, input flow range is 5/8L/min
minimum flow- 5L/min to prevent CO2 rebreathing
simple face mask- advantages and disadvantages
+ve- moderate but variable FiO2, good for patients with blocked nasal passages and mouth breathers, easy to apply
-ve= uncomfortable, interface with further airway care, proper fitting is required, risk of aspiration in unconscious patient, rebreathing (if input is less than 5 L/min)
reservoir masks
commonly used reservoir system- partial re-breath mask, non-rebreathe, FiO2- 60-80%, flow >8L/min
the bag should remain inflated to ensure the highest FiO2 and to prevent CO2 rebreathing
oxygen delivery methods- fixed performance devices
deliver a fixed proportion of air and oxygen ensuring an accurate concentration of oxygen delivery regardless of inspiratory volumes and rate
a venturi mask
a fixed FiO2 model, a variable FiO2 model
rationale for humidified oxygen
humidified oxygen should be considered for patients who require high-flow oxygen systems for more than 24 hours
