Respiratory Failure and Sleep Apnoea Flashcards
What is hypoxia defined as
- defined as partial pressure of oxygen in the blood below 8 kPa
What is type 1 respiratory failure
- hypoxia - partial pressure of oxygen below 8kPa
what is type 2 respiratory failure
- hypoxia - partial pressure of oxygen below 8 kPa
- hypercapnia -partial pressure of carbon dioxide above 6.5 kPa
- carbon dioxide can dissolve in the blood to produce carbonic acid
- pH falls to less than 7.35 in acidosis
What is the main function of the lungs
- Ventilation
- gas exchange
- perfusion of the lungs
describe the mechanism of a action of ventilation
- intercostal muscles and diaphragm contract
- pressure inside the chest is less than outside
- air is sucked into the lungs
- inspiration takes place
- intercostal muscles and diaphragm relax
- elastic recoil of the lungs forces them to contract
- pressure inside the chest is greater than outside
- air is pushed out of the lungs
- expiration happens
What is the mechanism of hypoxia
- hypoventilation
- diffusion abnormality
- ventilation/perfusion mismatch
- right to left cardiac shunt (missing out the lungs)
- low inspired oxygen
What is the normal control of ventilation
- stimulation of breathing centre in the brain
- peripheral chemoreceptors of the carotid and aortic bodies
What can cause hypoventilation
- Obstruction to airways = asthma at late stage and COPD
- Thoracic cage problems = throacoplasty for TB, Kyphoscoliosis, morbid obesity
- Weakness of respiratory muscles = motor neurone disease and muscular dystrophy
- hypoxia stimulates increased ventilation, unable to increase ventilation = hypoxia and hypercapnia
What can cause a V/Q mismatch
Lung airspaces filled with fluid
- lobar pneumonia
- pulmonary oedema
Lung collapse
- pneumothorax
- lung collapse
Area of lung ventilated but not perfused
- pulmonary embolic
- asthma
- Hypoxia leads to increased ventilation
- more carbon dioxide is exhaled
- hypoxic but not hypercapnic
What can cause a diffusion abnormality
- Sarcoidosis
- pulmonary fibrosis
- COPD
- asbestosis
- Hypoxia leads to increased ventilation, more carbon dioxide is exhaled = hypoxic but not hypercapnic
What can cause low inspired oxygen
- high altitude
- air flight
What are the types of respiratory failure
- Type I Acute
- Type I Chronic
- Type II Acute
- Type II Chronic
What are the causes of type 1 respiratory failure
Diffusion abnormality
- pulmonary fibrosis
- emphysema in COPD
V/Q mismatch - reduced V
- pneumonia
- pulmonary oedema
- pneumothorax
- lung collapse
V/Q mismatch - reduced Q
- PE
Low inspired oxygen
What are the causes of type II respiratory failure
Obstruction to airways
- COPD
- Asthma
Hyper expanded lungs
- COPD
Thoracic cage problems
- Kyphoscoliosis, thoracoplasty
- obesity
Weakness of respiratory muscles
- e.g. MND, DMD
How do you treat acute type 1 respiratory failure
- high flow oxygen
- 60-100% oxygen via mask
- keep oxygen stats above 95%
- treat underlying cause - pneumonia, pulmonary oedema, pulmonary embolism, non severe asthma
- consider CPAP if continuing hypoxia
What is CPAP
Continuous positive airway pressure
How does CPAP work
= pushes pressure into airways mainly during expiration
- can expand collapse portions of the lungs which are under ventilated
What is the benefit of CPAP
• Improves ventilation perfusion matching • Improves hypoxia • Keeps airway open in sleep apnoea But • Does not overcome hypoventilation
If you patient is hypoxic you need to give them…
oxygen but not too much oxygen
What is acute type II respiratory failure due to
failure of ventilation
How do you treat acute type II respiratory failure
Use controlled oxygen therapy
- 0.5 or 2 l/min via nasal cannulae
- 24-28% masks using venturi valves
- aim to keep oxygen 88-92%
- do blood gases regularly to monitor carbon dioxide levels
- consider non invasive ventilation if pH and carbon dioxide is not improving
what does non invasive ventilation improve
- hypoventilation
- oxygenation
- prevents or reduces hypercapnia
What does non invasive ventilation do
- delivers high pressure during inspiration to improve ventilation
What conditions is non invasive ventilation helpful in
- useful in all conditions causing hypoventilation and type II respiratory failure
acute type II respiratory failure
- COPD exacerbations
Chronic type II respiratory failure
- kyphoscoliosis, thoracoplasty
- neuromuscular diseases such as MND, muscular dystrophy
- obesity hypoventilation syndrome
- COPD
describe how acute NIV can benefit COPD
- Intubation rate (27% to 15%)
- In-hospital mortality (20% to 10%)
- Complications (mostly ventilator associated pneumonia)
- Length of hospital stay
What are the consequences of chronic type I respiratory failure
- pulmonary hypertension
- cor pulmonale
- peripheral oedema
- secondary polycathaemia - stroke
- symptoms from ischaemic heart/peripheral vascular disease
- poor sleep
- neuropsychiatric
- fatigue
What do you give for chronic type I respiratory failure
long term oxygen
What does long term oxygen therapy do
• Improves survival in COPD patients with hypoxia (PaO2 < 7.3 kPa)
• Reduces complications of hypoxia:
– cor pulmonale
– polycythaemia
how long are they given long term oxygen for
Patients given oxygen concentrator to deliver oxygen for at least 15 hours per day
what is type I respiratory failure a failure of
failure of oxygenation
What is obstructive sleep apnoea
Repetitive episodes of partial or complete upper airway obstruction during sleep
What is apnoea
- a complete cessation of airflow for at least 10 seconds
What is hypopnea
- a reduction in airflow to under 50% or by 30% for at least 10 seconds with a desaturation of at least 4%
What is AHI
– number of apnoeas and hypopnoeas per hour of the study (equivalent to the Respiratory Disturbance Index, RDI)
How is the severity of sleep apnea measured by
- Apnoea-Hypopnoea Index (AHI)
- Respiratory Disturbance Index (RDI)
describe the different severity of sleep apnea measured by the Respiratory Disturbance Index (RDI)
- 0-5 = within normal limits
- 5-15 = mild OSA
- 15-30 = moderate OSA
- 30 + = severe OSA
How many people have sleep apnoea
- 1 in 5 adults have sleep apnoea
- mild sleep apnoea seen in 24% of men and 9% of women
- increases with age until about 65 years
What increases prevalence of sleep apnoea
- older age
- obesity = BMI greater than 30 is associated with a 5-18 fold increase in risk of OSA
- neck circumference increases risk especially if greater than 16.5 inches
- being male - males have a longer pharyngeal airway
- afro-caribbean people have twice there isa of caucasians and Asians
What are the associated conditions of sleep apnoea
Abnormal anatomy • Micrognathia or retrognathia • Large adenoids and tonsils • Acromegaly • Down’s syndrome
Systemic conditions
• Hypothyroidism, Cushing’s syndrome
• Type II diabetes, hypertension
What is the sleep history for sleep apnoea
- Bed partner and family very useful
- Snoring (heavy?)
- Witnessed apnoeas (“I have to prod him to start breathing”)
- Arousals (“I wake up suddenly with a snort”)
- Unrefreshed on waking
- Daytime tiredness
- Planned and unplanned naps
- Other cardiovascular risk factors or events
Describe how the Epworth sleepiness scale works
Situations
- sitting and reading
- watching TV
- sitting inactive in public place
- as a passanger in a car for an hour without a break
- lying down to rest in the afternoon with circumstances permit
- sitting and talking to someone
- sitting quietly after lunch without alcohol
- in a car while stopped for a few minutes in traffic
- 0 = would never dose
- 1 = slight chance of dozing
- 2 = moderate chance of dozing
- 3 = high chance of dozing
total score out of 24
- score of 10 or more is abnormal
Who should be informed of sleep apnoea
- DVLA should be informed of diagnosis
What are the other medical consequences for sleep apnoea
- cardiovascular mortality
- systemic hypertension
- insulin resistance and type II diabetes
- coronary artery disease
- stroke
- congestive cardiac failure
What is the treatment of sleep apnoea
• Weight loss • Avoiding alcohol and sedatives • Non-supine sleep • Tonsillectomy • Mandibular advancement splints • Palatal surgery • Maxillofacial surgery • Treat medical cause e.g. Cushings - CPAP
What are mandibular splints used for
- used for simple snorers
- mild to moderate sleep apnoea
- intolerance of CPAP
When is CPAP used for in sleep apnoea
- used for patients with moderate or severe sleep apnoea
How is CPAP therapy good for sleep apnoea
- Very effective in the majority of patients
- Reduces daytime sleepiness
- Reduces the incidence of RTAs
- Improves cognitive performance, mood and quality of life
- Reduces daytime blood pressure
- Reduces cardiovascular events in severe OSA
- Helps prevent pulmonary hypertension and right heart failure
- May help insulin resistance and glycaemic control
what are the symptoms of sleep apnoea
- loud snoring
- daytime somnolence
- poor sleep quality
- morning headache
- decrease libido
- noctuira
- decrease cognitive performance
What are the complications of sleep apnoea
- pulmonary hypertension
- type II respiratory failure
What can cause snoring and sleep apnoea
- enrichment on pharynx - obesity, acromegaly, enlarged tonsils
- nasal obstruction - nasal deformities, rhinitis, polyps, adenoids
- respiratory depressant drugs - alcohol, sedatives, strong analgesics
What is central sleep apnoea and what is the difference to obstructive sleep apnoea
- Central sleep apnea (CSA) occurs when the brain temporarily fails to signal the muscles responsible for controlling breathing - more due to a communication error
- Obstructive sleep apnoea is due to a mechanical problem
What is used in a sleep study
- oximetry
- direct measurements of thoracic and abdominal movement to assess breathing
- electroencephalography to record patterns of sleep and arousal
what happens in oximetry in sleep apnoea
- oxygen saturations falls in a cyclical manner giving a sawtooth appearance to the tracing
Who should you refer urgently in adults who have obstructive sleep apnoea
- Who are sleepy whilst driving or working with machinery, or are employed in hazardous occupations (for example pilot or bus or lorry driver). Advise the person not to drive until they have been assessed by a specialist.
- With signs of respiratory failure or heart failure.
- With symptoms suggestive of severe obstructive sleep apnoea syndrome (OSAS) and coexistent chronic obstructive pulmonary disease.
who should you refer routinely in adults who have obstructive sleep apnoea
- with symptoms suggestive of OSAS and or accompanying Hepworth sleepiness questionnaire score of more than 10
What does the diagnosis of obstructive sleep apnoea require
The diagnosis of OSAS requires at least five episodes of apnoea, hypopnoea, or both events per hour of sleep.
When should patients inform the DVLA and stop driving with sleep apnoea
- They are diagnosed with OSAS, and the symptoms include sufficient sleepiness to impair driving.
- Prior to formal diagnosis, the person is reporting sufficient levels of sleepiness to impair driving, and there is a reasonable chance that this is due to a medical condition
What are the indications for mechanical ventilation in respiratory failure
- acute respiratory failure - respiratory rate greater than 40 breaths a minute, inability to speak, patient exhaustion, confusion, rising PaCO2
- acute ventilatory failure- due to myasthenia gravis, Guillain barre syndrome,, used when vital capacity has fallen to 10mL/kg or less
When is it no appropriate for ventilatory support and is appropriate for palliative measures in respiratory failure
- end of life care
- not going to make a difference
- advanced care planning
What is vesicular breathing
Longer inspiration than expiration
What is bronchial breathing
Longer expiration than inspiration
What does pleural rub sound like
Leather rubbing sound in inspiration and expiration
