week 3 Flashcards
what is respiratory failure
respiratory failure occurs when the respiratory system fails top oxygenate arterial blood adequately (hypoxaemia) and consequently fails to provide the body with adequate amounts of oxygen (hypoxia) and/or the person fails to ventilate well enough to eliminate carbon dioxide
what is hypoxia
inability to provide oxygen to the tissues
what is hypoxaemia
lack of oxygen in arterial blood
How do we diagnose respiratory failure
take a sample of arterial blood and measure the partial pressure of O2 and CO2
what are the two main types of respiratory failure
type 1 and type 2
how long does it take for acute respiratory failure to develop
minutes to hours
whats an example of an acute respiratory failure
pneumonia
how long does chronic respiratory failure take to develop
over days
what is an example of chronic respiratory failure
COPD
what is type 1 respiratory failure
failure to maintain O2 levels in arterial blood
(hypoxaemia)
what is type 2 respiratory failure
failure of respiratory pump to ventilate adequately
(hypoxaemia and hypercapnia)
what is ischaemic hypoxaemia due to
inadequate blood flow through the lung
What is anaemic hypoxaemia
reduction in the carrying capacity of the blood e.g. anaemia/significant blood loss/sickle cell crisis
what is toxic hypoxaemia
difficulty utilising oxygen
what are some of the clinical signs of hypoxaemia
central cyanosis
peripheral shut down (cool to touch, cold and clammy)
tachypnoea
tachycardia
low oxygen saturations
confusion or agitation
Causes of type 2 respiratory failure
CNS depression/abnormalities with the respiratory drive centres
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
what can happen if patients with hypoxic drive are given large and unchecked amounts of additional oxygen
it can remove their drive to breathe
what is hypoxic drive
a condition associated with a small number of people with COPd and tends to be associated with more severe cases
what does CPAP stand for
continuous positive airway pressure
what does CPAP do
delivers the same flow of gas throughout inspiration and expiration
increases functional residual capacity and primarily aimed at improving gas exchange and type 1 respiratory failure
splints open alveoli
What does NIV stand for
non-invasive ventilation
what does NIV do?
blows air into the lungs, via a nasal mask or a face mask, to ensure that the breathing remains supported and to prevent under-breathing
The NIV machine will recognise that the person using it has started to breathe in and assists with each breath
what are the acute effects of NIPPV
reduced PaCO2
increase alveolar ventilation
rest respiratory muscles
decrease load on the respiratory muscles
what are the contraindications for NIV
life threatening hypoxaemia
haemodynamic instability
confusion or agitation
upper gastrointestinal surgery or bowel obstruction
barotrauma
inability to protect airway
risk of vomiting
excessive secretions
facial trauma
haemoptysis
what are the advantages of NIV
non invasive
no sedation
can be ward managed
low cost
easy to withdraw
easy to manage at home
allows communication, mobility, sleep
why is severe hypoxaemia potentially dangerous
because it causes tissue hypoxia with insufficient oxygen available to tissues to meet metabolic needs
what does an increase in PaCo2 cause
respiratory acidosis
what does a decrease in PaCO2 cause
respiratory alkalosis
what are some potential causes of respiratory acidosis
hypoventilation
exhaustion
drugs
cardiac arrest
what are some potential causes of a respiratory alkalosis
excess mechanical ventilation
acute hyperventilation
anxiety/pain
stroke
anaemia
meningitis
acute asthma
SAH
altitude fever
what does an increase in HCO3 cause
metabolic alkalosis
what does a reduction in HCO3 cause
metabolic acidosis
what are some causes of metabolic alkalosis
volume depletion
diuretics
excess vomiting
burns
what are the causes of metabolic acidosis
diabetic ketoacidosis
diarrhoea
renal failure
what two organs compensate for one another to maintain a relatively constant pH
lungs and kidneys
name some indications for oxygen therapy
hypoxaemia
acute care situations in which hypoxaemia is suspected
severe trauma
acute MI
short term therapy (post anaesthesia recovery)
name some complications of oxygen therapy
oxygen toxicity
depression of ventilation
absorption atelectasis
fire hazard
what is the amount of oxygen delivered dependent on
oxygen flow rate
patients inspiratory volume
respiratory rate
what are the types of oxygen delivery methods?
nasal cannula
simple face mask
reservoir mask
what are the advantages of a nasal cannula
easy to fix
keeps hands free
not much interference with further airway care
low cost
compliant
what are the disadvantages with nasal cannula
unstable
easily dislodges
high flow uncomfortable
nasal trauma
mucosal irritation
FiO2 can be inaccurate and inconsistent
what are the advantages of a simple face mask
moderate but variable FiO2
good for patients with blocked nasal passages and mouth breathers
easy to apply
what are the disadvantages of a simple face mask
uncomfortable
interfere with further airway care
proper fitting is required
risk of aspiration in unconscious patient
rebreathing
name the variable flow devices for prescribing oxygen
nasal cannula
face mask
reservoir mask/non rebreathe
name the fixed flow devices for prescribing oxygen
venturi system via simple face mask or humidified system
nasal high flow
what is the aim of oxygen therapy
to help manage type 1 respiratory failure
