Sleep Apnea

Snoring & Sleep Apnea

What causes snoring?

Snoring is caused, fundamentally, by airway narrowing — causing high velocity airflow. This high velocity airflow imparts kinetic energy to the soft tissues of the upper airway, and eventually causes vibration of soft tissue (perceived as snoring). Therefore, snoring is an indicator of upper airway narrowing (anyone who snores, by definition, has upper airway narrowing).

As the airway lumen narrows, the air moving within the airway tube has to increase velocity in order to fill the lungs in the same amount of time as the normal respiratory cycle (in other words, people with airway narrowing do not take longer to inspire and expire than people without airway narrowing; lung volumes do not change — therefore, the air has to travel more quickly through these areas of anatomic upper airway narrowing in order to fill the lungs during the normal respiratory cycle).

Changes in airway pressures result (Venturi and Bernouli principles apply), and the high velocity airflow imparts kinetic energy to the soft tissues within the airway. This energy, over time, causes stretching or “pulling” of these soft tissues — eventually leading to “secondary elongation” of these various tissues (typically, the soft palate is the most unsupported or “compliant” portion of the upper airway, and that is why the soft palate typically becomes elongated first). Additionally, the lateral pharyngeal walls may also become ‘stretched’ over time.

These elongated tissues eventually become very “loose” and “floppy” (ie: compliant), and when the inherent tissue resistance to movement is overcome by the ongoing kinetic energy, vibration results. This vibration is what is perceived as snoring — and can be measured in terms of both frequency and intensity.

People are not born with long soft palates (primary elongation); instead, palates become “stretched-out” over many years of rapid airflow (secondary elongation).

It is important to realize, however, that the primary source of airway narrowing in these cases is typically NOT at the level of the soft palate. Instead, in the vast majority of patients, it is the tongue-base region in which the primary site of narrowing often occurs (in other words, the elongated and unsupported soft palate vibrates as a result of high velocity airflow produced by airway narrowing at another site within the airway).

While primary sites of airway narrowing will vary from patient to patient, upstream narrowing (often occurring in the nasal region) may also contribute to downstream collapse of the airway (ie: nasal obstruction may often contribute to tongue-base collapse — so-called “Starling Resistor Effect”). This is why it is often important to deal with areas of nasal obstruction as a pretext for solving problems occurring lower in the airway. Similarly, massively enlarged tonsils and adenoids (particularly in the pediatric population) may serve to affect airway narrowing and high velocity airflow — as well as contribute to further downstream narrowing.

People who suffer from very slight airway narrowing (ie: just enough to cause enough rapid airflow to cause snoring without frank closure of the airway) have a diagnosis of Primary Snoring. As the airway continues to collapse, however (with further rapid airflow until frank obstruction), snoring persists. This is why it is generally impossible to discern — out of all people who snore — who actually has sleep apnea versus primary snoring (in other words, all of these patients will snore). This is also why each person who snores truly requires some type of sleep study in order to discern the severity of their airway problem, and to discern whether snoring represents possible obstructive apnea.

How is snoring treated?

Based upon the above model, there are actually three fundamental ways to deal with snoring:

Removal of the vibrating soft tissues: This technique, described further here, requires the surgical removal of vibrating and redundant soft tissue- typically of the soft palate. This surgical technique, called “Uvulopalatopharyngoplasty” (or simply: “UPPP”) can be exceedingly painful, but may cause some temporary cessation of vibration (and thereby help- at least temporarily- with snoring). It is critically important to understand, however, that the fundamental problem of airway narrowing persists when isolated soft palate surgery is performed (typically occurring more proximally- at the level of the tongue base). This persistent site of airway narrowing causes continued rapid airflow- which over time, continues to impart kinetic energy to the remaining tissues, and eventually stretches the tissues back out, causing a return of snoring (typically seen 1-1.5 years following the UPPP procedure). In other words, the cycle noted above repeats itself. Many patients become extremely frustrated with the results of previously performed soft palate surgery for this reason- as their snoring often returns 1-1.5 years later after this painful surgery is performed.
Stiffening of the vibrating soft tissues: This technique, performed by many various techniques, aims to “stiffen” the loose redundant soft tissues by causing scarring of the soft palate (thereby diminishing soft tissue compliance). The “stiffened” tissue is therefore less willing to vibrate as a result of the rapidly flowing airstream. Somnoplasty, Coblation, Injection Snoreplasty, Electrocautery, Pillar Procedure, CAPSO- all affect scarring of the soft palate, which leads to temporary stiffening. While many patients will enjoy a temporary interval of improved snoring following these procedures, the same fundamental problem described above exists (ie: the primary site of airway narrowing has not been dealt with; therefore, high velocity airflow persists- and eventually recurrent soft tissue vibration and snoring return).
Expand the Airway: Airflow through the constricted portion of the upper airway is dictated by Pousille’s Equation- which, among other factors, relates flow of substances through a tube. Importantly, within Pousille’s mathematical equation, the radius is raised to the fourth power- meaning that very small changes to the radius of the tube at its narrowest point has a HUGE impact on airflow (doubling the radius of a tube at its narrowest point increases flow by a factor of 16!). Therefore, if the site of proximal airway narrowing can be expanded- (in some cases, even a very small amount), a tremendous increase in airflow will result (which will be very beneficial for patients with OSA). Besides this factor, another very important dynamic takes place with airway expansion: the velocity of airflow dramatically slows when the airway is expanded at its narrowest point (in other words, while more volume of airflow is achieved, this volume of air is now traveling at a much slower velocity of speed). With lower velocity of airflow, kinetic energy does not become imparted, hence there is no energy to affect soft tissue vibration.

Expansion of the airway is the fundamental mechanism for both CPAP and oral appliance therapy (nonsurgical therapies), and most tongue-base surgical procedures (including jaw advancement and hyoid suspension.)

« Previous - 1 2 3 - Next »