Oxygen therapy and sleep apnoea Flashcards
what are oxygen sources
Oxygen cylinders Wall supply Oxygen concentrators Liquid oxygen Delivered in Litres per minute
what are oxygen cylinders
Widely available (home and institutions) Various sizes Limited length of supply Suitable for limited/short duration treatment Relatively expensive Supply 100% oxygen
what is a wall supply
In hospital only
Central supply in piped clinical areas
May not be available in all areas (eg clinic rooms)
Supply 100% oxygen
what are oxygen concentrators
Mains operated machine Molecular sieve – removes nitrogen Oxygen predominant gas so >90% oxygen Use in home or when out Regional suppliers with franchise for installation and support
what is liquid oxygen and its uses
More highly compressed
Larger gaseous volume
Allow higher flow rate
Well-developed in US and parts of Europe
what are patients interfaces
For spontaneously breathing patients
Nasal cannulae
Uncontrolled masks (Hudson, non rebreathe)
Controlled (fixed percentage – ventur) masks
how does oxygen reach patient via interfaces
Litres per minute or percentage inspired oxygen
what is nasal cannula
Usually well tolerated Accepts flow rates 1-4 l per min Delivers 24-40% O2 % delivered depends on multiple factors Used for mild hypoxemia, not critically ill Can dry out nose
what are uncontrolled masks
Simple face mask Hudson mask Delivers 30-60% O2 Flow rate 5-10 l/min Mix of O2, room air and exhaled air in mask Used less often
what are uncontrolled masks (non rebreathe)
Delivers 85-90% oxygen with 15L flow rate
Bag one way valve stops mixing with room air and patient rebreathing expired air
Used in acutely unwell patients (step down ASAP)
what is a Venturi mask
Controlled oxygen
Venturi valve allows delivery of a fixed concentration of oxygen
how is oxygen a drug
Can save lives with oxygen but can also do harm
How given depends on clinical circumstances and patients medical background (eg COPD)
Oxygen should be prescribed on drug chart with target oxygen saturations
what are the clinical indications for oxygen use
used for hypoxaemia, not breathlessness
Acutely hypoxaemic patients
Chronically hypoxaemia COPD patients with acute exacerbation
Chronically hypoxaemic COPD patients who are stable
Palliative use in advanced malignancy (sats <90% and breathless, often multifactorial)
what are the target oxygen saturations
Normal young adult 96-98% Over 70 94-98% Target for most 94-98% Balance of what is normal and safe Target for those at risk of hypercapnic respiratory failure is 88-92% - lower for some
what is acute breathlessness with hypoxaemia a risk of
Risk is acute hypoxaemia leads to acute cardiac dysrhythmia and organ failure
Treatment with maximal oxygen, high flow uncontrolled mask (first line), alter flow and delivery device when stable
what needs to be considered besides giving oxygen
Not just about oxygen
Secure and maintain airway patency
Enhance circulation (volume, anaemia, CO)
Avoid/reverse resp depressants
Establish reason for hypoxaemia and treat
If not improving, may need ventilation
Who is at risk of hypercapnia if given high dose oxygen
Chronic hypoxic lung disease (COPD, CF)
Chest wall disease
Neuromuscular disease
Obesity related hypoventilation
how are chronically hypoxaemia patients with COPD who have acute exacerbation treated
Maintain modest oxygenation whilst preventing CO2 retention and acidosis
Deliver oxygen by fixed percentage venturi mask starting at 24%
Target 88-92%
how can response to oxygen treatment be assessed
Arterial blood gases, check frequently
pO2 <10, pCO2 falling from peak to maintained <6, pH increasing/maintained >7.35
adjust dose of oxygen accordingly
not improving=non invasive ventilation
if a patients is not improving why shouldn’t you use nasal cannulae
potentially dangerous as actual inspired oxygen percentage varies according to patients respiratory characteristics
uncontrolled therapy
how is oxygen prescribed
target O2 sat range, the delivery device and the dose (flow rate or percentage inspired oxygen)
may have an oxygen treatment card with recommended O2 sats/prescription
what is LTOT
Long term oxygen therapy
For some COPD patients
Specialist assessment – in patients stable state and no sooner than 4 weeks after an exacerbation
what are the LTOT indications
COPD pO2 <7.3kPa or 7.3-8kPa with a complicating disorder
how is LTOT provided
Provided with an oxygen concentrator
Regional concentrator supply service
O2 treatment for >15 hours per day
what are the benefits of LTOT
Improved long term survival Prevention of deterioration in pulmonary hypertension Reduction of polycythaemia (raised Hb) Improved sleep quality Increased renal flow Reduction in cardiac arrythmias Improved quality of life
what is portable oxygen in terms of LTOT
Improves breathlessness in some patients
May extend duration of LTOT
BUT most patients breathlessness is not due to low pO2
Weight of cylinders
Duration of supply
what is sleep apnoea
Apnoea (cessation of airflow for 10 seconds or longer)
Central – resp control centre – no resp effort
Obstructive: collapse of pharyngeal airway during sleep (cont of respiratory effort)
OSA 5 or more obstructive apnoeas per hour
what is hypopnea
reduction in airflow by 50% accompanied by desaturation of 4% and or arousal from sleep
what is the prevalence of apnoea
2% adult women and 4% adult men, increasing incidence
what are the risk factors of apnoea
Male sex Obesity Neck circumference Smoking Alcohol/sedative use Craniofacial abnormalities Pharyngeal abnormalities Some medical conditions like hypothyroidism or pregnancy) Sleeping supine
what is the pathophysiology of apnoea
nasal: polyps or deviated septum
enlarge tonsils
pharynx: dec in neuromuscular tone or caliber, inc in resistance
inc soft tissue: eg obesity or hyperthyroidism
abnormal chin: micronathia, retognathia
normal tongue relaxation and any causes of marcoglossia
what happens in sleep apnoea
sleep
muscles/tissues relax (pharyngeal airway)
collapse and obstruction of airway - snoring
apnoea
arousal
muscle tone returns and airway clears
resumption of breathing
what are the clinical features of sleep apnoea
Snoring Nocturnal choking/waking with a start Unrefreshing/restless sleep Morning dry mouth or headaches Excessive daytime sleepiness (difficulty concentrating, irritability or mood changes, sleeping at inappropriate times) Nocturia
what are the complications of apnoea
Cor pulmonale (right heart failure 2ndry resp distress) Secondary polycythaemia
what are investigations of apnoea
Repetitive apnoeas and symptoms of sleep fragmentation
Epworth sleepiness scale or sleep studies (eg polysomnography via sensors and monitoring technician)
what is the epworth sleepiness scale
list of 8 situations, asked to rate from 0- no chance of drifting off to 3 - almost definitely driving off
over 10- apnoea/concerning
how is apnoea diagnosed
Uses apnoea/hypopnea index AHI= apnoeas + hypopneas / total sleep time in hours Mild 5-14 per hpur (= saigns/symptoms) Mod 15-30 Severe more than 30 Or oxygen desaturation index
what are consequences of OSA
Increased risk of accidents Associated with Hypertension Type 2 diabetes IHD HF Stroke Cardiac arrythmias Death
How is OSA managed
Goals Resolve signs and symptoms of OSA Improve sleep quality Normalise AHI and oxygen saturations Multi-disciplinary approach
how can patients managed their OSA
Patient education eg driving Behavioural change Weight loss Avoid sleeping supine Avoid alcohol Treat contributing problems Review medications eg sedating drugs or those causing weight gain
How can OSA be treats
Mandibular advancement devices
CPAP
surgery
what are mandibular advancement devices
Hold soft tissues of oropharynx forward, mild to mod OSA, patient pref, failed CPAP
how is surgery used to treat apnoea
most effective if severe, correctable, obstructing lesion
Tonsillar or adenoid hypertrophy, craniofacial abnormalities
what is CPAP
Continuous positive airway pressure (device generates airflow > positive pressure delivered via mask, intraluminal pharyngeal pressure > surrounding pressure, pharynx stays open)
When is CPAP used
Patients with mild OSA and additional co morbidities
“ and high risk profession
Patients with moderate/severe OSA regardless of symptoms
Not mild with no additional risk factors who aren’t excessively sleepy
what are the benefits of CPAP
Symptoms resolve
Decrease in apnoea/hypopnea, daytime sleepiness and risk road accidents
Increase quality of life
Normalise BP
What are the issues with CPAP
Adherence
Airway drying or irritation (can humidify)
Mask issues (air leak or comfort)
Normally life long treatment
