CPAP vs BiPAP: How to Choose the Right Airway Therapy

The CPAP vs BiPAP choice comes down to pressure. CPAP delivers one continuous pressure through breathing in and out, while BiPAP delivers a higher pressure on inspiration and a lower one on expiration. CPAP is the standard first machine for obstructive sleep apnoea; BiPAP is usually reserved for patients who cannot tolerate CPAP. Neither stands alone: lifestyle change and, where there is a structural block, surgery are used alongside them.

Dr. Trisha Srivastava, Consultant, ENT, Artemis Hospitals, Gurugram, India, makes the combination principle central to her practice. The treatment options for snoring and obstructive sleep apnoea, in her words, are not independent of each other: they are provided in combination, depending on how severe the patient's symptoms are. This article explains how each option works and how the choice is made. It assumes a diagnosis has been reached; the steps from questionnaire to sleep study are covered in how obstructive sleep apnoea is diagnosed, and the underlying science in the complete guide to the science behind snoring.

Not every snoring patient needs surgery

A common fear among patients is that a referral for snoring leads straight to an operation. Dr. Srivastava is direct on this: not every patient who comes in with snoring is advised surgery. It is not a matter of fixing the nose or removing the tonsils for everyone. The plan follows from what the examination finds and how severe the sleep apnoea is.

She frames the cause as structural, physiological or both. Where examination finds a clear anatomical obstruction in the nose, nasopharynx or oropharynx, the patient can be shown that the block is the reason for the snoring and the poor sleep, and that fixing it will help. Her example is a lean individual with a badly deviated septum: correct the septum and the problem is sorted. Where nothing structural is at fault, the problem is often weight and a thick neck, and the first treatment is lifestyle change.

Lifestyle change: the first stage of sleep apnoea treatment

Lifestyle modification is the first stage of treatment in Dr. Srivastava's practice. She points to the sedentary pattern of modern working life, long hours in a chair at a laptop, as a driver of the obesity she sees in snoring patients.

Her lifestyle advice is specific:

• Lead a more active life and build exercise into every day.
• Be careful about diet, cutting down on fatty and unhealthy food.
• Try to reduce weight.

Exercise matters even when nothing else is wrong. In many patients, she notes, the palate is not bulky and the nose is clear, but the neck is thick, and a thick neck is itself one of the reasons people develop obstructive sleep apnoea. Fat around the neck lets the airway collapse when muscle tone falls during sleep.

For a very obese patient, her sequence is to advise lifestyle change and weight loss first, then reassess, and only then decide on further treatment: the patient may become a CPAP user or undergo surgery as required. For patients with mild obstructive sleep apnoea, lifestyle modification can come before any machine; in moderate or severe disease, guidelines combine weight loss with PAP or another primary treatment rather than waiting for it to work.

Alcohol and sleep

Doctors in the session asked whether a glass of wine at night helps. Dr. Srivastava's view is that it does not: alcohol disrupts sleep and causes dryness, and she knows of no textbook or literature showing that wine helps. Alcohol in the evening also relaxes the muscles that hold the throat open, so it worsens both snoring and obstructive sleep apnoea. Avoiding alcohol in the hours before sleep is standard advice for people who snore.

What a PAP machine does

A positive airway pressure (PAP) machine is, in Dr. Srivastava's description, an airway splint. In obstructive sleep apnoea the upper airway narrows or closes during sleep, typically at the retropalatal level (behind the soft palate) or at the base of the tongue. The machine delivers pressurised air through a mask worn over the nose or face, and the pressure holds the airway open so the obstruction does not happen. Because it works by air pressure rather than a physical device in the throat, it is called a pneumatic splint.

PAP treats the airway only while it is worn. It does not change the anatomy, so the benefit depends on using it every night.

CPAP vs BiPAP: the key difference

The difference between the two machines lies in how pressure is set across the breathing cycle.

CPAP (continuous positive airway pressure) gives the same air pressure throughout. It does not matter whether the patient is breathing in or out: the pressure remains constant, splinting the airway open continuously.

BiPAP (bilevel positive airway pressure) has two settings, one for the inspiratory phase and one for the expiratory phase, and they are set differently depending on where the problem lies. Dr. Srivastava's example is a patient who needs a pressure of around 8 on inspiration but only around 4 on expiration; the machine is set accordingly. Pressures on these machines are measured in centimetres of water.

In summary:

• Pressure pattern: CPAP holds one fixed pressure; BiPAP alternates between a higher inspiratory and a lower expiratory pressure.
• Typical role: CPAP is the usual starting therapy for obstructive sleep apnoea; BiPAP is used when a patient cannot manage CPAP.
• Comfort: the lower expiratory pressure on BiPAP can make breathing out against the machine easier for patients who need high pressures.

A third variant, auto-adjusting PAP (APAP), changes its pressure through the night in response to the airway, within a set range. Current guidelines accept either fixed CPAP or APAP to start treatment in adults; BiPAP is not routinely used as first-line therapy for uncomplicated obstructive sleep apnoea.

Why many patients stop using CPAP

Dr. Srivastava is candid about the main weakness of PAP therapy. The mask is worn on the face all night, and many people do not like the sensation of pressurised air and stop using the machine. Many patients who cannot handle a CPAP machine are moved to BiPAP.

Nasal anatomy compounds the problem. If the patient has a badly deviated septum, the pressure has to be set high to get past that obstruction, and high pressures are harder to tolerate. In those cases, she says, surgery becomes important. Correcting nasal obstruction lowers the pressure the machine needs and improves tolerance of PAP.

Adherence is measured, not assumed. Use for at least four hours a night on at least 70% of nights is the widely used benchmark for adequate CPAP adherence.

Who needs a CPAP or other PAP machine?

Positive airway pressure is the standard treatment for moderate and severe obstructive sleep apnoea in adults, and it is also recommended for patients with milder disease who have excessive daytime sleepiness, impaired quality of life or hypertension. Dr. Srivastava describes the patients at the severe end: those whose oxygen saturation falls into the 70s and even the 60s during sleep. In her practice, a PAP machine is also the option for patients who do not want any surgical intervention, or who are grossly unfit to undergo one.

Sleep apnoea surgery by level of obstruction

Surgery is matched to the level at which the airway is blocked, as shown on examination and, for the palate, on drug-induced sleep endoscopy.

The nose: septoplasty and turbinoplasty

For nasal obstruction, the operations are septoplasty and turbinoplasty, which Dr. Srivastava describes as fairly basic ENT procedures.

• Septoplasty straightens a deviated nasal septum, the partition between the two sides of the nose.
• Turbinoplasty reduces enlarged turbinates, the ridges on the side walls of the nose that swell with allergy and congestion.

These operations matter beyond snoring itself, because a clear nose lowers the pressure a PAP machine needs.

The oropharynx: tonsillectomy

If the patient has very large tonsils, tonsillectomy removes them and widens the oropharynx.

The palate: palatoplasty

Palatoplasty is the specialised surgery for sleep-disordered breathing at the level of the soft palate. Dr. Srivastava explains its aim: to open up the retropalatal space, the airway behind the soft palate. The surgeon uses sutures to reposition the palatal muscles, with suspension and sling techniques, so that the space opens not only from front to back but also from side to side, and the patient breathes better at night.

One specialised procedure she presented is barbed pharyngoplasty, which uses barbed sutures to reposition and suspend the palatal muscles. At her institute, drug-induced sleep endoscopy is performed in the operating theatre immediately before surgery to evaluate the retropalatal area and decide which type of palatoplasty the patient needs.

Children: adenotonsillectomy

In children, the usual causes are enlarged adenoids and tonsils, and the treatment Dr. Srivastava provides is their removal. The adenoids are cleared from the nasopharynx using coblation. The effects of untreated sleep apnoea on a child's growth and school performance are described in the complete guide to the science behind snoring.

How to choose between CPAP, BiPAP and surgery

The decision combines three inputs: how severe the sleep apnoea is, where the airway is blocked, and what the patient is willing and fit to undergo. In practice:

1. Every patient with excess weight or a sedentary life is advised lifestyle change, first on its own in mild disease and alongside other treatment in moderate or severe disease.
2. A patient with a correctable structural block, such as a deviated septum, large tonsils or a narrow retropalatal space, is considered for targeted surgery.
3. A patient with moderate or severe sleep apnoea, or one who declines or cannot undergo surgery, is offered PAP, starting with CPAP and moving to BiPAP if CPAP cannot be tolerated.
4. Options are combined: nasal surgery to make PAP easier, or weight loss before reassessing the need for a machine.

Doctors' questions from the session, including the comparison of CPAP with BiPAP and the role of alcohol, are answered in the Live Discussion. Dr. Srivastava's practice is described on her profile.