Sleep Disordered Breathing

Question 1

What is the crux of the problem of obstructive sleep apnea?

Answer 1

The airway can be thought of as plumbing and while some portions are bound by bone, the nasopharynx and oropharynx are muscles so they can be collapsed which is the crux of the problem for obstructive sleep apnea.

Question 2

True or False: As you get older or gain weight, there is a narrowing of the upper airway (oropharynx)

Answer 2

True

Question 3

What’s going on here?

Answer 3

As you have a narrowing of your upper airway (shown as an increase supraglottic resistance), you have more electromyography activity (muscles increase tonic output to keep from collapsing)

Question 4

What happens to the upper airway in sitting vs. supine position? (particularly when sleeping)

Answer 4

When supine, everything in the front of our throat falls to the back. Particularly the tongue. This narrows the airway and increases resistance to airflow.

An infection may cause swelling and also cause narrowing of the airway. Or if you have alcohol before you sleep, your muscle tone will be decreased and this also narrows the airway.

Question 5

What is the effect of sleep on the upper airway?

Answer 5

A lot of protective mechanisms are lost.

Inspiratory premotor activation decreases, tonic premotor activation decreases, and reflex driven muscle activation is lost.

Question 6

What are P_crit, P_US, P_DS, zone 1, 2, and 3 for airway collapse?

Answer 6

P_crit is the pressure of the collapsed part of the airway

P_US is the pressure upstream to the collapse

P_DS is the pressure downstream to the collapse

Zone 1 is when P_crit > P_US > P_DS and the airway is completely occluded.

Zone 2 is when P_US > P_crit > P_DS . In Zone 2, the airway is narrowed but not collapsed. Pressure upstream is able to overcome the narrowing and this is the physics of snoring.

Zone 3 is when P_US > P_DS > P_crit and the airway is open

Question 7

What happens to P_AO2 , P_ACO2, P_aO2, and P_aCO2 when there is airway collapse?

Answer 7

There is a loss of ventilation during airway collapse so

P_AO2 and P_aO2 go down, P_ACO2 and P_aCO2 go up

Question 8

What is the upper airway recruitment threshold?

Answer 8

This is the threshold or magnitude of stimuli necessary (negative pressure, increased CO₂, or decreased O₂) required to elicit a response from upper airway dilator muscles to adequately overcome P_crit

Question 9

What is the arousal threshold?

Answer 9

This is the magnitude of stimuli (negative pressure, increased CO₂, or decreased O₂) needed in order to trigger an arousal (waking up).

Question 10

What is loop gain?

Answer 10

Loop gain is the magnitude of ventilatory response to stimuli.

Once you arouse, you are in a deficit where your O₂ is low and CO₂ is high. You have to hyperventilate to correct this. Patients can have loop gain that doesn’t match the deficit (can either hyperventile or hypoventilate)

Question 11

What is the issue with patients with high upper airway recruitment threshold?

Answer 11

These patients have longer duration of obstructive events because it takes a greater stimuli for them to recruit their dilator muscles

Question 12

What is the issue with patients with low arousal threshold?

Answer 12

These patients have low threshold for arousal which causes them to wake frequently, hyperventilate frequently, which causes hypocapnia (low CO₂), which can actually cause a decrease in upper airway muscle tone. A decrease in upper airway muscle tone will cause more obstruction in the oropharynx (upper airway). So, this leads to cyclic episodes of obstructive events.

Question 13

What is the issue with patients that have high loop gain?

Answer 13

These patients have a greater sensitivity to CO₂ and O₂ stimuli, so they hyperventilate which causes hypocapnia (low CO₂) which causes decreased upper airway muscle tone which causes collapse of the oropharynx. Again, this leads to cyclic episodes of obstructive events.

Question 14

What is central sleep apnea/Cheyne-Strokes Respiration?

Answer 14

People with central sleep apnea/Cheyne-strokes respiration are overly sensitive to CO₂ stimuli when sleeping which causes them to hyperventilate and overcompensate by blowing off too much CO₂. This causes long periods of central apnea where the brain just thinks that it doesn’t have to breathe anymore because the CO₂ was blown down so much.

This can be very disruptive and can lead to disruption of sleep and daytime symptoms.

Question 15

Answer 15

C. P_crit > P_US > P_DS

Zone 1

Question 16

For sleep disorder breathing, does collapse happen on inspiration or expiration?

Answer 16

Inspiration

Question 17

What is apnea? What are the 3 types?

Answer 17

Cessation of nasal and oral airflow for a duration of at least 10 seconds. There are 3 types of apnea: central, obstructive, and mixed.

Central - cessation or reduction of airflow that occurs in association with the abscence of ventilatory efforts

Obstructive - cessation or reduction of airflow that occurs despite the persistence of ventilatory efforts

Mixed - cessation or reduction of airflow with an initial central component and terminal obstructive component.

Question 18

What is hypopnea?

Answer 18

Reduction of airflow or amplitude of thoraco-abdominal movement by at least 30% from baseline for at least 10 seconds in duration and accompanied by oxyhemoglobin desaturation of 4% or more

Question 19

What are apnea index and apnea-hyopopnea index?

Answer 19

Apnea index is the number of apneas per hour of sleep time.

Apnea-hypopnea index (AHI) is the number of apneas plus hypopneas per hour of sleep time.

Question 20

True or False: We all snore occassionally

Answer 20

True

Question 21

For habitual snoring, do men or women snore more?

Answer 21

Men. (44% of men vs 28% of women)

Question 22

What is upper airway resistance syndrome?

Answer 22

It is a syndrome that about 9% of people have where the resistance to airflow leads to arousals. (Oxygen levels don’t fall and there is no collapse)

Question 23

Is obstructive, mixed, or central apnea most common?

Answer 23

Obstructive (85%)

Mixed (14%)

Central (1%)

Question 24

True or False: There is probably a higher prevalence of sleep apnea than we know about because of people who don’t present with symptoms

Answer 24

True

Question 25

What is cheyne-stokes breathing and what kind of people are more prone to this pattern of breathing?

Answer 25

Cheyne–Stokes respiration is an abnormal pattern of breathing characterized by progressively deeper and sometimes faster breathing, followed by a gradual decrease that results in a temporary stop in breathing called an apnea. The pattern repeats, with each cycle usually taking 30 seconds to 2 minutes. It is an oscillation of ventilation between apnea and hyperpnea with a crescendo-diminuendo pattern, and is associated with changing serum partial pressures of oxygen and carbon dioxide.

About 40-50% of patients with history of heart failure and 10% of patients with history of stroke have cheyne-stokes respiration.

Question 26

Sleep apnea morbidity and mortality is associated with increased risk of what?

Answer 26

Obesity

Cardiovascular disease (pulmonary HTN, CAD, HTN, HF, CVA, hyperlipidemia, diabetes mellitus/DM)

Motor Vehicle Crash

Question 27

When should you perform a sleep history? (3)

Answer 27

1. High risk patient screening
2. Routine health maintenance exam
3. Patient reports symptoms

Question 28

Who should be a included in the high risk population screening for sleep studies?

Answer 28

Morbidly obese (BMI greater than 35)

CHF

Atrail fibrillation (in order to properly treat A. fib patients, you need to address their sleep apnea if they have it)

Treatment refractory hypertension

Type 2 diabetes

Nocturnal dysarhythmias

CVA

Pulmonary HTN

High-risk driving populations

Preoperative for bariatric surgery

Question 29

For routine health maintenance exams, what questions should be asked to investigate for sleep apnea? (5)

Answer 29

Is the patient obese?

Is the patient retrognathic? (overbite anatomy)

Does the patient complain of daytime sleepiness?

Does the patient snore?

Does the patient have hypertension?

Question 30

In what demographics is sleep apnea most prevalent in?

Answer 30

More commonly in males

Increased prevalence as people age up to 6th and 7th decades of life

Prevalence is greater in minority populations (asians can have sleep apnea at lower BMIs)

Question 31

What past medical history events increase chance of sleep apnea?

Answer 31

Chronic rhinitis

Acromegaly

Neuromuscular disorder

Amyloidosis

Upper airway anatomic abnormalities

Genetic syndromes (e.g. 80-90% of Down syndrome patients develop sleep apnea)

Question 32

True or False: family history of sleep apnea is irrelevant

Answer 32

False. If your parents have sleep apnea, you are more likely to have it too. You look like your parents on the outside, and you look like them on the inside too.

Question 33

What social history increases risk of sleep apnea?

Answer 33

Smoking (inflammation) and drinking (decreased muscle tone)

Question 34

What medications can cause someone to be more susceptible to sleep apnea?

Answer 34

Sedative-hypnotics and opioids. These put patients at high risk for both obstructive and central sleep apnea.

Question 35

What are the sleep apnea symptoms?

Answer 35

Excessive daytime sleepiness

Witnessed apneas

Snoring

gasping/choking at night

nonrefreshing sleep

memory loss

decreased concentration

decreased libido

irritability

decline in performance at work or school

nocturia (waking up to pee) or enuresis (inability to control urination)

• attention deficit (in children)*
• hyperactivity (in children)*

Question 36

What is the epworth sleepiness scale?

Answer 36

A questionairre asking about likelihood of falling asleep during normal activities

Question 37

What can be done on physical exam to examine the oropharynx?

Answer 37

Mallampati Classification system

This can help determine someone’s risk of sleep apnea

Question 38

How can neck circumference be used to assess sleep apnea?

Answer 38

If a man has a neck circumference greater than 17 inches or a woman has greater than 16 inches

Question 39

True or False: If a patient has sleep apnea symptoms, you should do a sleep test

Answer 39

True

Question 40

How are sleep studies done?

Answer 40

In-lab study

EEG - brain waves

EMG - muscle movement

Belts around stomach and chest to measure breath effort

ECG - heart

They are quite cumbersome and costly.

Question 41

What is a benefit of doing a split night study?

Answer 41

One part of the night is for diagnosis and another part of the night is therapeutic

Question 42

How are home sleep tests done?

Answer 42

They are diagnostic only and a patient is sent home with a belt to put around their chest, stomach, oxygen sensor for the finger and and oxygen tubing for the nose.

Question 43

Home sleep tests should not be done in what kind of patients?

Answer 43

Patients with cardiopulmonary comorbidities because of confounding. Home sleep test won’t be accurate enough.

Question 44

After a sleep study has been done, what is the AHI cutoff for doing treatment?

Answer 44

If AHI is greater than or equal to 5 and a patient has symptoms, they are treated for sleep apnea.

Or if a patient has AHI greater than 15 without symptoms, they are treated for sleep apnea.

The cutoffs are different for pediatrics.

Question 45

Answer 45

E. polysomnography

Polysomnography is a comprehensive recording of the biophysiological changes that occur during sleep.

Question 46

How do you treat obstructive sleep apnea?

Answer 46

General measures: sedative avoidance, smoking cessation, correction of precipitating conditions (e.g. hypothyroidism).

Weight reduction

Positional therapy (e.g. tennis-ball-sock in shirt for supine sleep apnea)

Oxygen therapy (particularly for central sleep apnea at altitude. takes away need to hyperventilate)

Pharmacotherapy

Positive airway pressure

Oral devices

Upper airway surgery

Nerve stimulation

Question 47

What is PAP therapy?

Answer 47

Positive airway pressure therapy.

This is the most effective and gold standard treatment for sleep apnea. It is a mechanical solution to a mechanical problem. Airway pressure keeps airways open in the P_Crit

Question 48

What oral appliances are there to help with sleep apnea?

Answer 48

Tongue retainer and mandibular repositioner

Question 49

What are the surgical options for obstructive sleep apnea treatment?

Answer 49

Tracheostomy (for very severe sleep apnea)

This is a percutaneous tracheal opening distal to the pharynx that bypasses the area of upper airway obstruction.

This is indicated for patients with severe life-threatening OSA who are intolerant or unresponsive to other types of therapy

Maxillomandibular advancement

Advancement of both the maxilla and mandible. This enlarges the retrolingual and retropalatal airway. Positive response rates in up to 90% of cases but this procedure can cause regular pain so it’s not an operation that’s commonly recommended.

UvuloPalatoPharyngoPlasty (UPPP or UP3)

Excision of uvula, posterior portion of the soft palate, redundant pharyngeal tissue, tonsils, and tonsilar pillars. This is less effective than CPAP therapy and we hardly send patients for this operation anymore. The problem here is that the issue is usually with the tongue and not the soft palate.

Tonsillectomy and adenoidectomy

Removal of tonsils and adenoids. This may be effective in children with OSA due to adenotonsillar enlargement but this doesn’t really help adults. In adults, OSA is typically because a combination of issues including obesity and other things. In children, it’s typically more of an anatomical problem as children are less often morbidly obese with other OSA risk factors. That is why this is typically a solution for kids but not adults.

Question 50

How is nerve stimulation used to help with OSA?

Answer 50

Similar to a pacemaker, a device is implanted that has wires going to the intercostal muscles to sense respiratory effort and a wire that goes to the tongue which can cause the tongue to contract to keep the airway open. This is new and has a long way to go before it becomes common practice

Question 51

Answer 51

B. Tonsillectomy and adenoidectomy