Sleep apnea + sleep breathing disorders Flashcards
Define hypopnea, obstructive apnoea & respiratory effort related arousals (RERA)
Hypopnoea: A breathing sleep disorder classified by a 30% reduction in flow lasting greater than 10s, associated with a greater than 3% reduction in SpO2, symptoms such as snoring, gasping, or waking up feeling unrefreshed.
OSA: defined as a 90% reduction in flow for greater than 10s, not associated with blood desaturation, sleep disorder characterized by repeated interruptions in breathing during sleep due to partial or complete obstruction of the upper airways
RERA: An arousal from sleep due to a sequence of breaths that last greater than 10s, RERAs are characterized by an increase in the effort to breathe, which causes the person to partially wake up to restore normal breathing.
Describe the pathophysiology of OSA
OSA can occur up to 60 times an hour, involves a complex interaction between the upper airway anatomy, neurological control of breathing, and muscle tone during sleep. obstruction leads to intermittent hypoxia (low oxygen levels) and hypercapnia (elevated carbon dioxide levels), triggering arousals from sleep. It contributes to a wide range of cardiovascular, metabolic, and cognitive complications.
Describe the risk factors
& diagnosis for OSA
6% of adults have severe OSA. Diagnosis:
1. Gather patient history
2. Use Epworth sleepiness scale
3. Use a bed partner questionnaire
4. Overnight oximetry suitable for those at high risk of OSA
5. Polysomnography is the standard test used to diagnose OSA, but equipment is expensive and needs a hospital stay.
6. Polygraphy study is more accurate than oximetry alone
Risk factors include
1. increasing age
2. Being a male
3. obesity, BMI greater than 25
4. Neck circumference
5. smoking, alcohol
6. pregnancy
7. Supine sleeping position, causes tongue to fall back and block airway
What are the daytime & nighttime symptoms for OSA
Daytime:
1. daytime sleepiness
2. Morning headache
3. Dry mouth on waking
4. Memory/concentration problems
5. Mood/personality changes
Nighttime:
1. Loud snoring
2. witnessed apnoea by partner
3. Waking up choking
4. disrupted sleep/insomnia
5. sweating
What do people suffering OSA have an increased prevalence of?
OSA has been shown to cause cognitive impairment, hypertension, & increased mortality from CVD’s
Increased prevalence of type 2 diabetes,
Describe the risk factors for upper airway collapse
- Excess fat deposits within bony structure in upper airways, as it increases intraluminal pressure
- Excess fat & tissue around upper airways, as it causes narrowing and increased resistance
- Physical deformities in bone structure surrounding upper airways causes an increase in intraluminal pressure
- Muscle weakness of upper airways e.g. trauma
Describe the use of oximetry and polygraphy on sleep report
Oximetry is used to measure total number of oxygen desaturations per hour
Mean O2 sats are measured
Polygraphy calculates AHI (apnoa & hypopnoea index) which is the number of A’s & H’s per hour
Pulse rises are also measured, greater than 15 increased per hour is significant.
False positive and negative are common
How do we determine the severity of sleep apnoea
We use a scale of AHI
1. none/minimal severity is an AHI less than 5
2. Mild severity is between 5-15 according to AHI
3. Moderate severity is between 15-30
4. Severe is greater than 30
Describe positional OSA
Describe as being present when the AHI is in the supine position is twice of that in the non-supine position.
Significant positional OSA is when the supine AHI is twice of that of the non-supine
Exclusive positional OSA is above the criteria & AHI is less than 5 in non-supine position
Describe the treatment of OSA
Weight loss, 10-15% weight loss can improve sleep apnoea symptoms by 50%
CPAP machine (continuous positive airway pressure)
Positional therapy
Surgery
Hypoglossal nerve stimulation
Mandibular advancement splints
Describe the use of CPAP for treatment of OSA
Produces positive intraluminal pressure, it inhibits the suction affect maintaining a positive transmural pressure and therefore a patent airway.
CPAP pressures should be titrated for each patient to ensure pressure is good enough to prevent apnoea’s
Pressures are in range between 4-20cm H2O as higher pressures are hard to tolerate.
CPAP machines can ramp up pressure gently during 1st hour so patients can get used to flow rate
Describe the need for patient compliance when using CPAP
Patients must use CPAP for a least 4hrs a night, a lifelong treatment. Patients may be required to inform DVLA and cannot drive until they receive effective treatment. Equipment use is recorded, there is a card or remote download.
Patients may not like CPAP machines as they are noisy & intrusive. They dislike the feel of airflow in the face. It may be difficult to seal leaks. patients may feel claustrophobic. patients may have skin problems due to air pressure can cause skin damage.
Name the types of CPAP masks
- Nasal mask
- Full face
- Nasal pillow
- Total face
- Hybrid
Describe mandibular advancement splint as a treatment for OSA
Oral splint (mouthguard) worn at night to prevent airway collapse by maintaining jaw position.
Position the lower jaw down and fowards.
Limitations: Only effective in mild/moderate OSA, requires the teeth to be in good condition, it can be uncomfortable e.g., jaw/tooth pain
Describe the use of surgery as a treatment for OSA
Only used if there is an anatomical problem that can be resolved.
e.g., removal of nasal polyps or tonsils
Excess tissue in the upper airways can also be removed
Describe the need for alternative treatment for OSA
Weight loss may be unrealistic for those with OSA as they may lack the energy to engage with exercise, use of CPAP would be better
MAS can be good for mild/moderate OSA but less useful for severe OSA, A CPAP is preferred
Changes in position can be effective if CPAP cannot be tolerated by patient
Describe the use of upper airway stimulation in treatment for OSA
By stimulating the upper airways it prevents it from collapsing during breathing as airways remain open.
To do this a pulse generator is implanted in the chest which processes breathing data and provides stimulation, the sensor detects how often the person if breathing, and if intervention is needed
Name sleep related breathing disorders
Central sleep apnoea
Nocturnal hypoventilation
Obesity hypoventilation syndrome
Describe central sleep apnea
Describe the regulation of breathing via chemoreceptors
Role of chemorecpetors is to maintain blood pH, suffcient levels of O2 and CO2 in the blood, Based on the signals they send, the body adjusts the rate and depth of breathing to maintain homeostasis.
Peripheral chemorecptors are involved in pH, PaO2 & PaCO2
Central chemoreceptors are involved in PaCO2 and breathing regulation, they send signals to the respiratory centers in the brainstem to increase the rate and depth of breathing. This helps to expel excess CO2, raise the pH, and restore a balanced blood gas composition.
Describe influence of sleep on chemoreceptors
Central chemoreceptors have a reduced sensitivity to CO2 levels during sleep. This means the brain becomes less responsive to rising CO2 levels when a person is asleep compared to when they are awake. This leads to hypoventilation, where CO2 builds up in the blood.
Peripheral chemoreceptors remain more sensitive to oxygen levels, especially when they drop during sleep, and can trigger an increase in breathing rate and depth.
Tidal volume drops in NREM sleep & by 25% in REM sleep
Describe the affect of chemoreceptor control on central sleep apnoea
CSA is caused by a defciency in the sensitivity of central chemoreceptors, they fail to respond to high CO2 in the blood, this leads to periods of apnoea as the body does not adjust to remove excess CO2
There is an apnoea threshold which is the lowest level of CO2 in which the apnoea can occur.
Treatment of OSA using CPAP can reduce CSA
Describe the causes of central sleep apnoea
- HF can cause increased chemosensitivity leads to loops of hyperventilation & hypoventilation
- Loss in ventilatroy drive during NREM sleep as CO2 is dependant, this can occur due to damage to the brainstem
- Loss of chemoreceptor drive by mixed sleep apnoea leads to central apnoea,
- Unstable ventilatory control at altitude, hypoxia increases ventilation
Describe the daytime & nighttime symptoms of CSA
Daytime:
1. fatigue/sleepiness
2. morning headache
3. memory/concentration problems
4. Mood/personality changes
Nighttime:
1. waking up gasping for air
2. witnessed apnoeas
3. restlessness/insomnia
4. absent/mild snoring
Describe the diagnosis of CSA and treatment
Diganosis: Polygraphy & oximetry
Treatment:
1. treat the underlying cause e.g., treat HF
2. Use a CPAP
3. Supplemental O2
4. Diaphragmatic pacing
Describe obesity hypoventilation syndrome
is a condition in which obesity leads to impaired breathing during sleep and, often, during wakefulness. It is characterized by chronic hypoventilation resulting in hypercapnia and hypoxia. This condition is closely associated with severe obesity, often defined by a BMI of 30 or higher
Excess fat in abdomen/ chest can restrict the expansion of the lungs and the movement of the diaphragm, leading to reduced TV. The muscles responsible for breathing are weakened, making it harder to generate the force required to maintain normal ventilation. This can result in shallow and inefficient breathing.
have a PaCO2 of greater than 6kPa, indicating daytime hypercapnia, as well as nocturnal ventilation
Explain daytime hypercapnia in OHS
Obesity causes mechanical restriction leading to reduced TV, ventilation is less effective resulting in higher PaCO2 & low PaO2
central respiratory drive can be impaired, body is less responsive to rising CO2 levels in the blood.
In OHS, the sensitivity to CO2 is often reduced, so the body’s natural response to elevated CO2 is blunted. This reduces the body’s ability to increase ventilation and expel excess CO2, leading to a buildup of CO2 in the bloodstream.
Reduced lung compliance, meaning the lungs become stiffer and less able to expand fully during breathing. This decreases the efficiency of gas exchange due to excess fat
Explain nocturnal ventilation in OHS
refers to the impaired breathing that occurs during sleep in individuals with obesity, contributing to hypoxia and hypercapnia in the blood.
The lose the drive to breathe
During sleep, the body’s natural compensatory mechanisms for low oxygen or high CO2 are less responsive. The reduced muscle tone during sleep further weakens the diaphragm and respiratory muscles, leading to inefficient ventilation and a buildup of CO2 in the bloodstream.
Describe the symptoms, diagnosis and treatment of OHS
Symptoms: can vary/non-specific
hypercapnia (increased PaCO2) and low SpO2 during sleep, daytime fatigue, morning headaches, peripheral oedmea, nocturnal sweating & unexplained polycythaemia
Diagnosis:
1. History: assess the patient’s weight, symptoms, and any previous diagnoses of obesity, sleep apnea, or respiratory issues
2. Polysomnography is often used to rule out sleep apnea and determine the severity of sleep-disordered breathing.
3. ABG testing is essential for diagnosing hypercapnia (elevated CO2) and hypoxia (low oxygen) during wakefulness.
4. Nocturnal pulse oximetry to measure overnight oxygen saturation.
Treatment:
1. Positive pressure ventilation with CPAP or BiPAP devices to maintain airway patency and improve ventilation.
2. Oxygen therapy for supplemental oxygen during sleep.
3. Weight loss to alleviate the mechanical burden on the respiratory system.
