Respiratory failure

Question 1

what is respiratory failure

Answer 1

the respiratory system fails to oxygenate the arterial blood adequately and/ or fails to prevent CO2 retention

Question 2

causes of respiratory failure

Answer 2

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)

Question 3

consequences of respiratory failure

Answer 3

respiratory and all muscles fatigue, hypoventilation, sputum retention, hypoxaemia

Question 4

consequences of respiratory failure- if left

Answer 4

cardiac arrhythmias, cerebral hypoxaemia, respiratory acidosis, CO2 necrosis, coma, cardiac arrest

Question 5

types of respiratory failure- how are they classified?

Answer 5

classified as hypoxaemic or hypercapnic and may be either acute or chronic

Question 6

types of respiratory failure- type 1

Answer 6

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

Question 7

types of respiratory failure- type 2

Answer 7

type II respiratory failure is characterised by PaO2 of less than 8kPa (hypoxaemia) with an increase in Paco2 levels greater than 7kPa (hypercapnia)

Question 8

what happens during respiration and what goes wrong

Answer 8

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

Question 9

causes of type 1 respiratory failure

Answer 9

hypoxic hypoxaemia, ischemic hypoxaemia, anaemic hyperaemia, toxic hypoxaemia

Question 10

what is hypoxic hypoxaemia

Answer 10

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

Question 11

how does the SA of the lung reduce PP of oxygen

Answer 11

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

Question 12

consequences of hypoxaemia- aneamic hypoxia and toxic hypoxaemia

Answer 12

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

Question 13

consequences of hypoxaemia- ischemic and anaemic hypoxaemia

Answer 13

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

Question 14

how long does tissue it take for tissue hypoxia to occur

Answer 14

brain= 3-5 mins, kidney and liver= 10-20 mins, skeletal muscle= 60-90 mins, vascular smooth muscle= 24 hours, hair and nails= days

Question 15

type II respiratory failure

Answer 15

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)

Question 16

causes of type 2 respiratory failure

Answer 16

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

Question 17

capacity or strength of respiratory muscles

Answer 17

hyperinflation, respiratory muscle fatigue, poor muscle oxygenation/ nutrition, general fatigue, over use of accessory muscles

Question 18

load on respiratory muscles

Answer 18

increased airway resistance (airway collapse, sputum, bronchospasm), static and dynamic hyperinflation, intrinsic peep, increased resistance to airflow, increased elastic load

Question 19

how do we treat respiratory failure

Answer 19

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

Question 20

what is hypoxaemia

Answer 20

lack of oxygen= give oxygen, it is often considered when our patients are in respiratory failure

Question 21

types of hypoxaemia- oxygen therapy

Answer 21

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

Question 22

consequences of respiratory failure

Answer 22

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

Question 23

what is oxygen therapy

Answer 23

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

Question 24

indications for O2 therapy

Answer 24

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

Question 25

complications of O2 therapy

Answer 25

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

Question 26

starting and monitoring oxygen

Answer 26

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

Question 27

oxygen sats documentation

Answer 27

documented with oxygen device, FiO2 and flow rate

Question 28

assessing for oxygen therapy

Answer 28

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

Question 29

what is a variable- performance devices

Answer 29

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

Question 30

what is nasal cannula

Answer 30

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%

Question 31

nasal cannula- advantages and disadvantages

Answer 31

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

Question 32

reservoir cannula- advantages and disadvantages

Answer 32

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)

Question 33

simple face mask

Answer 33

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

Question 34

simple face mask- advantages and disadvantages

Answer 34

+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)

Question 35

reservoir masks

Answer 35

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

Question 36

oxygen delivery methods- fixed performance devices

Answer 36

deliver a fixed proportion of air and oxygen ensuring an accurate concentration of oxygen delivery regardless of inspiratory volumes and rate

Question 37

a venturi mask

Answer 37

a fixed FiO2 model, a variable FiO2 model

Question 38

rationale for humidified oxygen

Answer 38

humidified oxygen should be considered for patients who require high-flow oxygen systems for more than 24 hours