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Wednesday, May 18, 2011

Sleep Apnea

The Greek term "apnea" literally means "without breath." So when someone stops breathing, even for a short period of time while supposedly sleeping, this is what we refer to as sleep apnea. This "apnea" results in the patient not getting enough air to the lungs.

People with sleep apnea quit breathing repeatedly during the hours of sleep, often hundreds of times, according to the American Sleep Apnea Association. It's a disease that is more common than most people think, and many who have it are unaware they have it.

According to Egans Fundamentals of Respiratory Care, the scientific definition, and the one most medical professionals go by, is cessation of breathing for 10 seconds or longer. Likewise, it's diagnosed as 30 or more episodes of apnea in a six hour period

Symptoms of sleep apnea usually include:
  • Excessive daytime sleepiness
  • Fatigue
  • Loud snoring
  • Restless sleep
  • Morning headaches
  • Irritability
  • Mood swings
  • Depression
  • Learnign difficulties
  • Memory difficulties (Continued drops in oxygen cause loss of brain tissue)
  • Sexual dysfunction
These symptoms are secondary to the patient constantly waking up during the night. Usually the patient doesn't even know he (or she) is waking up. And this results in "unexplainable" exhaution during the day.

A common sign of sleep apnea is snoring at night, periods were it looks like the person isn't breathing (apnea), and the feeling you need to smack the person in order to wake him up. This "poor quality" sleep results in tiredess during the daytime.

These patients have a hard time staying awake in school, at meetings, or while simply sitting around the house or office. In this way, it can effect your day to day living.

A greater concern is that it can effect your health in other ways too, such that when a person stops breathing, or takes inadequate breaths, oxygen levels (PO2) may drop to critical levels, and this places a strain on the heart.

As hypoxia occurs, the heart starts to beat faster in an effort to pick up more oxygen. The only time this wouldn't occur is if the heart is already weakened due to other conditions, or due to
In this sense, those with sleep apnea are at high risk for:
  • Cardiovascular disease (due to constant drops in oxygen)
  • Stroke
  • High blood pressure (does not drop while sleeping)
  • Arrhythmias
  • Diabetes
  • Sleep deprived driving accidents (due to lack of adequate sleep)
Likewise, if apnea periods are long enough, this can result in chronic hypoxia and chronic carbon dioxide retention (high CO2).

The diagnosis is usually made based on an evaluation and history of the patient and anyone who might be present with the patient while he is sleeping, such as a spouse. Diagnosis is generally made based on symptoms noted by the patient and family members.

Once it's believed the patient has sleep apnea, a sleep study is required to confirm the diagnosis, and to determine appropriate treatment. (see sleep study and treatment below).

There are three types of sleep apnea:

1. Obstructive (OSA): This is the most common. The soft tissue of the upper airway (throat) collapses and when the brain signals the body to take in a breath, it doesn't go in. Instead an effort is made, and perhaps a loud snore or gasp. This prevents oxygen from getting to the lungs, and results in hypoxemia (low oxygen to the blood) and hypoxia (low oxygen to the tissues).

This most commonly effects males ages 40-65, and may effect as much as 8% of the population, particularly obese males with large necks with little muscle tone. It's also more common in the elderly as opposed to young people.

Also of significance, about 20% of people diagnosed with OSA also have COPD. Hypoxia that occurs with COPD coupled with OSA may speed up the development of right heart failure.

Those at high risk for this include:
  • Smokers
  • Obese (the risk rises as weight rises)
  • Age
  • Diabetes (3 times the risk)
  • Enlarged tonsils
  • Enlarged adenoid
  • Excessive pharyngeal tissue
  • Goiter
  • Large tongue
  • Micrognathia
  • Myotonic Dystrophy
  • Shy-Drager Syndrome
  • Hypothyroidism
  • Accromegally
  • Males (8 times the risk as females)
Usually these patients go to sleep lying on their backs and fall into a light sleep, and this is eventually followed by a deeper sleep.  In the deeper sleep the muscles and tissues of your body relax, and this is when the tissues in the throats of OSA patients collapse and thus block the airway.  The patient then reverts back into a light sleep and is easily awakened.

This can happen hundreds of times during the night.  When these patients wake in the morning they know they have been lying down for 8 hours, yet they don't remember waking up a bunch of times in the night.  The result is feeling tired all day.

2. Central: The airway is not blocked, but the does not send the usual signal to take in a breath. This is also called Cheyne-Stokes Respiration. Breathing has the following pattern: none... fastter... faster... faster... very fast... slower... slower... slower... slower... none...
Genrally, breathing cycles between periods of hyperpnea (rapid breathing), apnea and hypopnea (slow breathing). If the period of apnea (pause) is long enough, the patient's oxygen level can drop significantly.

3. Mixed: A combination of obstructive and central sleep apnea.  Symptoms of this disease have been recorded in the annuls of history for thousands of years.

There are two other types of sleep apnea that are often used:

4. Pickwickian Syndrome*: This is used to describe patients who are very obese and excess fat tissue on the chest wall and below the diaphragm prevents the lungs from becoming fully expanded. This results in shallow and ineffective breathing. This is often accompanied with obstructive sleep apnea. The term was coined in 1957 to describe the cardiorespiratory effects of ineffective breathing due to obesity.

It was about 1970 when it was determined by scientists that there was more to this condition than just obesity. They determined that these patients presented with daytime sleepiness, flaccid upper airway tissue, and respiratory abnormalities during sleep. It was from here that sleep apnea was defined as a diagnosis and divided into OSA and CSA.

Another reason Pickwickian Syndrome doesn't always apply to sleep apnea is because in some cases sleep apnea is present is patients who are not obese.

However, from time to time, you'll still see Pickwickian as a diagnosis. Yet, thechnically speaking, Pickwickian is not a form of sleep apnea, just a condition that usually presents with it.

5. Ondine's Syndrome**: According to German folklore, the nymph Ondine falls in love with a mortal who becomes unfaithful to her. When this happens, the king of the nymphs places a curse on the mortal. The curse is such that instead of breathing automatically without thinking about it, the mortal will have to think about it. If he doesn't make a conscious effort to breath -- as if he falls asleep -- he will stop breathing. If he forgets to breathe he will die.

This is the earliest description of Central Sleep Apnea and should not be used. Instead...

6. Congenital Central Hypoventilation Syndrom (CCHS)**: This is used to describe people (particularly newborns) who have periods of hypoventilation and hypoxemia without any cardiac or neuromuscular disease. They breathe normal while awake, and hypoventilate while sleeping. While hypoxemia and hypercapnia progress during hours of sleep, there is no natural inclination to wake up when CO2 gets high enough as in OSA.

However, CCHS is still often called Ondine's Curse, and still it's just another way of describing CSA.

Cardiac and pulmonary effects***:  While apnea is occuring the patient is not drawing in oxygen (O2) and not exhaling carbon dioxide (CO2), so oxygen in the blood drops (hypoxemia) and CO2 in the blood rises (hypercarbia).

Secondary to hypoxemia, the heart slows down (bradycardia).  This is the body's natural response to decrease the body's oxygen consumption when there is less oxygen available.  Once breathing resumes, the heart increases (tachycardia), and this is the body's natural tendency to find oxygen.

Systemic and pulmonary blood pressure rises during periods of apnea, probably due to hypoxemia.  This is where most cardiac dysrhymias occur, and it is also believed that it is probably a life threatening cardiac arrythmia caused by hypoxemia that causes OSA and CSA patients to die in their sleep.

Likewise, about 10% of sleep apnea patients have high blood pressure.

Conclusion:  Sleep apnea is a serious condition that may result in day time sleepiness that may effect the every day life of the patient, and may even result in premature death.  It may be up to family members and/ or the physician to recognize the symptoms, and knowing that obese men with thick necks are most at risk

More References:

*Guilleminault C, Eldridge FL, Simmon FB, et al: "Sleep apnea syndrome-Can it induce hemodynamic changes," West J. Med, 123: 7-16, July 1975


***Wilkins, Robert L, Dexter, James R, "Respiratory Disease:  Principles of Patient Care," page 313, 1993

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