Obstructive Sleep Apnoea

Sleep Disorders Week

So I thought I'd do a quick #KYJ on Sleep Apnoea.

This is part 1 of 2.

There are two main types of Sleep Apnoea.  Central Sleep Apnoea (CSA), and 

Obstructive Sleep Apnoea (OSA).  As the name implies, OSA is a condition where soft tissues of the throat relax when sleeping, occluding or obstructing the airway. During periods of apnoea, oxygen levels in the blood fall (often dramatically -SpO2<75%).  While blood CO2 rises slightly, the effect of hypoxaemia is the most profound, and causes most of the acute sequelae. 

Let's just recap normal breathing stimulus.

Normally your brain stimulates you to take your next breath, based on a complex biofeedback mechanism.

When pH of the blood (and CSF) falls - acidosis; this is the primary trigger of breathing. Unlike you were probably taught, high CO2 isn't a direct stimulator of breathing, but it is secondary stimulant due to the fact that high plasma CO2 causes pH to fall (Carbonic or Respiratory Acidosis). So it is true to say high CO2 stimulates breathing, but indirectly through acidosis.

The second and more primitive stimulus to breathe is low plasma oxygen.  You were born with this mechanism, which you probably learned about when you were taught why a new born baby draws that first breath.   It is called "Hypoxic drive", but early in your infancy you switched to the high CO2/low pH trigger.  Called Hypercarbic drive, this mature lung, primary mechanism isn't in play during OSA, because CO2 doesn't dramatically rise.  You are asleep (or trying to), and at rest, you just don't make as much CO2.

So.  The Snorer is left with multiple obstructions, and apnoeas.  This leads to drop in plasma oxygen (hypoxaemia).  When oxygen falls low enough, the secondary hypoxic drive mechanism kicks in waking the snorer. They adjust position and inhale, restoring plasma oxygen levels.   The sleeper then drifts back to sleep with out realising that they woke up, and the whole cycle starts again.

Snoring is almost always present (even diagnostic).

Daytime tiredness morning headaches hunger and weight gain are common.

Poor concentration irritability and its extreme breathlessness on exertion, and ankle swelling which is the hallmark of right heart failure.

In its mildest form, people stop breathing every 5-12mins (5-14 episodes of apnoea/hour)

Moderate OSA is diagnosed at 15-30 Apnoea/hr

And severe OSA >30/hr.

That's an Apnoea every 1-2 mins.

Waking that often, causes the sufferer to feel like they are never well rested.  They may think they sleep all night, but realistically never completed important restorative sleep cycles, and this takes it toll on tissue healing, cell regeneration and hormone levels.

The body, in a constant state of stress, releases massive amounts of cortisol (our natural hydrocortisone) and Adrenaline driving up BP, and heart rate. While cortisol exerts its effects as glucose intolerance, insulin and leptin increase/resistance, obesity, atherosclerosis and T2 Diabetes, the adrenergic stress response contributes to the development of heart failure.

Just let that sink in for a minute.  Your snoring is causing your heart failure obesity and diabetes.

The age-old question of does a obesity cause OSA, or does OSA cause obesity is yet to be completely answered, but there is a biochemical body of evidence to suggest that poor sleep equals neurohormonal changes that lead to altered carbohydrate metabolism, and all the diseases linked to it.

You don't need to snore and snoring is the single most important feature of obstructive sleep apnoea. recognise it early nip it in the bud.   If you are sleeping next to that special someone who snores. Know this- it is not about your sleeplessness, it is about theirs.

Diagnosis :

Sleep studies are done to measure EEG , ECG and oxygen saturation, then when the moon is full a respiratory physician gazes at the cauldron of data and diagnoses OSA.

Treatment 

1. Surgery to remove or cauterise part of the soft palette.
2. Continuous positive airway pressure (CPAP) ,which blows air into the throat to splint the pharynx open. 
3. Jaw manipulation devices that thrust the lower jaw forward in an under-bite, while sleeping.  You remember from airway management courses that jaw thrust pulls tongue off the pharyngeal wall.
4. Tennis ball in a bum-bag.  Stops old mate rolling on his back and occluding his airway.

Big topic that we can't tackle comprehensively in one post.

Tomorrow (in our Sleep Week) we will look at Central Sleep Apnoea (CSA).

Hope you catch some zzzz! 

#ECT4Health 

ECT4Health