Apnea – A Word with Many Uses

Obstructive Sleep Apnea is a very common malady. It is familiar to many and is frequently a subject of both social and medical conversations. Individuals not engaged in frequent work with Apnea conditions may be confused by its usage and rightly so. Discussions and writings about the subject can use the term with different meanings.  When used by professionals, it can also be used in various ways. It has a physiologic technical meaning; it is used as a proper name of medical conditions; and, it has a common usage that is less specific.

The word – apnea – comes from the Latin and Greek languages. The Latin ‘a + pnea’ means without breath and the Greek ‘apnoia’ means without pain. The Webster dictionary defines apnea as ”Transient cessation of respiration”. Webster’s definition fits well with the current technical use of the word, but fails to show the scope of the word’s use that has increased over the past half-century with the recognition of the associated clinical conditions.

Webster’s definition fits well with the current technical use of the word, but fails to show the scope of the word’s use…

The word is used technically to label a cessation of breathing. Sleep testing, in facilities or at home, and physiologic monitoring of hospital patients can identify periods when no air is going in or out of the nose or mouth. No breaths can be measured. These events are called Apneas.  

The word is used technically to label a cessation of breathing.

The addition of chest movement measurements during these apnea events further defines these periods of apnea.  If the breathing efforts are persistent during an apnea episode, the event is labeled an Obstructive Apnea. If no breathing efforts are being made by the chest, the pump that moves air in and out, the apnea is caused by the lack of chest effort and is called a Central Apnea.  It is called central because breathing effort by the chest is controlled, started and adjusted, by the Central Nervous System.  If the breathing problem is associated with both partially reduced chest movement and total cessation of movement, it is labeled a Mixed Apnea.   As we can see, the technical apnea breathing events are further defined as obstructive, central or mixed.

‘Apnea’ is used as part of the proper name of medical conditions

‘Apnea’ is used as part of the proper name of medical conditions. These conditions were described and first recognized approximately a half-century ago, but probably have been affecting mankind for our entire history. Obstructive Sleep Apnea is the first of these. When breathing is blocked or partially blocked for 10 seconds at least five times per hour, a diagnosis of the clinical syndrome of Obstructive Sleep Apnea is established.

Central Sleep Apnea is the clinical condition where the primary form of apneas measured is central.  It is established when a certain percentage of the physiologic apneas recorded on testing are the central type.  Central Sleep Apnea can be the result of multiple medical issues that range from cardiovascular problems to neurologic conditions.  It can be rarely seen on its own and not associated with other medical problems.  

A third commonly accepted diagnostic term is Complex Sleep Apnea.  This diagnostic group represents individuals with obstructive sleep apnea treated with CPAP whose breathing events do not resolve when they are treated. Their Apnea Hypopnea Index remains high. However, on repeated testing with CPAP, the breathing events are now predominantly Central Apneas. The CPAP treatment caused a change from Obstructive Apnea events to Central Apnea events. This type of medical condition is called Complex Sleep Apnea.

The term Apnea Hypopnea Index (AHI) may be new to some, but it is very important that it is understood. The ‘Apnea’ referred to is the physiologic measured Apneas. ‘Hypopnea’ is a partial obstructive breathing event measured on testing.  They have the same secondary effects as apnea events but without the total cessation of airflow. The AHI is a calculated number representing the total events (Apnea and Hypopneas) per hour. 

The AHI is the measurement on a diagnostic sleep test that determines if an apnea condition of some type is present.  With a patient on therapy, it is the number that is followed by the physician to determine how well the therapy is working.  It is measured on most CPAP machines and can be reviewed by the patient on a day-by-day basis.  The AHI on a diagnostic test is and has been the measurement to determine the severity of sleep apnea conditions for many years. The AHI is an example of the technical use of the word apnea.

…the common use of the term Apnea is far less specific…

Finally, the common use of the term Apnea is far less specific than the uses we have reviewed. Often, the word is used to encompass a broad range of the field. In writings and conversations, it will be used by an author as a single word to cover all, or one, of the apnea medical conditions – obstructive sleep apnea, central sleep apnea and complex sleep apnea. When discussing Obstructive Sleep Apnea conversationally, most will speak about apnea, meaning obstructive sleep apnea.  The most simple descriptive of its common use is as a substitute for the clinical conditions associated with breathing problems during sleep.

What we have covered.

1. Apnea is technically an absence of breaths (no airflow at the nose and mouth). 

2. Apnea, used technically, during sleep is further defined by its features to be obstructive, central or mixed.

*Obstructive apnea

*Central apnea

*Mixed apnea

3. Apnea is used in the formal name of medical conditions including:

*Obstructive Sleep Apnea

*Central Sleep Apnea

*Complex Sleep Apnea

4. Apnea, used in its technical manner, is a component of the Apnea Hypopnea Index measurement used to judge the severity of the problem.

5. Apnea’s common use is as a general term covering one or all of the clinical conditions 

RGH June 29, 2020