Skip to Content

What is AHI (Apnea-Hypopnea Index)?(Understanding The Measurements)

What is AHI (Apnea-Hypopnea Index)?(Understanding The Measurements)

Obstructive sleep apnea, often known as OSA, is a prevalent sleep disease that is estimated to affect between 2 and 4 percent of the general population. People with OSA may encounter multiple partial or total airway blockages while sleeping. These episodes are referred to as hypopneas and apneas. In addition to these symptoms, you may also experience daytime tiredness, gasping or choking sounds, and loud snoring.

If you have just been diagnosed with sleep apnea or if you have undergone a sleep study, it is possible that an AHI value was included in your reports. Apnea-hypopnea index is abbreviated as AHI for convenience. When diagnosing patients with obstructive sleep apnea, medical professionals employ this scale.

AHI (Apnea-Hypopnea Index)

AHI (Apnea-Hypopnea Index)

The apnea-hypopnea index, often known as AHI, counts the number of breathing pauses during a given hour of sleep. If you suffer from sleep apnea, you might be more familiar with the term “events” per hour to refer to this statistic.

The apnea-hypopnea index, or AHI, is a tool that sleep specialists use to quantify the severity of their patients’ sleep apnea.

Your AHI will ultimately be used to calculate the pressure settings on your CPAP machine in order to reduce the number of times you experience apnea episodes.

Even if you are following the instructions for your CPAP therapy to the letter, you may find that the number of times you experience apneas has increased with time. This may be a very stressful situation when you have exhausted all the options available to you to control your sleep apnea. However, if you understand your AHI, you will be able to control your sleep apnea more effectively, resulting in increased CPAP compliance.

The AHI records the number of times during the night you experience pauses in your breathing and the number of times you experience bouts of breathlessness. The degree of sleep apnea is determined by adding all of these figures.

If your apnea-hypopnea index value is high, it indicates that you are not getting the deep sleep that is essential for maintaining your health. The easiest way to keep track of your AHI is to use a CPAP machine with an app that can record sleep data.

Measuring AHI

The apnea-hypopnea index, abbreviated as AHI, measures the number of apneas and hypopneas that occur during an individual’s typical hour of sleep. The severity of the condition can be determined by dividing the total number of apneic and hypopneic episodes that occurred during sleep by the total number of hours spent sleeping.

In order for apnea or hypopnea to be considered an event, it must last for at least ten seconds.

During a sleep study, also known as a polysomnogram, during which your doctor will monitor your brainwave activity, oxygen saturation levels, pulse rate, and breathing while you sleep, the AHI will be calculated. Polysomnography is normally carried out in a sleep laboratory; however, some individuals may be able to carry out a modified version of the procedure at home.

Even though the AHI is the major test used to diagnose OSA, your doctor may look at additional metrics to better understand how severe your OSA is. For instance, the measurement of how often your blood oxygen levels drop below normal for more than 10 seconds per hour is known as the ODI (oxygen desaturation index).

The concentration of carbon dioxide in the blood is yet another significant parameter, particularly for young infants. Even though the airway is not fully obstructed, a prolonged time of breathing at a capacity that is less than full can cause a buildup of carbon dioxide that can escalate to dangerously high levels.

Understanding the AHI Measurements for Adults and Children

Understanding the AHI Measurements for Adults and Children

The AHI is quantified numerically. The scores for adults are organized into three groups that correlate to varying OSA severity levels:

AHI of five or more occurrences per hour but fewer than 15 in one hour is considered mild.

AHI of 15 or more incidents per hour but fewer than 30 defines the condition as moderate.

A severe AHI is defined as at least 30 incidents occurring every hour.

In children, a diagnosis of obstructive sleep apnea may be made with an AHI of one or higher. This is in contrast to the cutoff for adults, which is five. This is because children have a quicker metabolic rate than adults, which requires them to breathe more quickly to sustain their lower lung capacity. Because of this, even a single episode of apnea might have a more significant effect on a kid.

The majority of sleep professionals believe that kids’ sleep apnea may be divided into three groups, although the classifications for adult sleep apnea are more standardized:

In children, a diagnosis of mild sleep apnea is possible if their AHI ranges from one to five occurrences per hour.

A child may be classified as having moderate sleep apnea if their AHI ranges from six to ten episodes per hour.

Children with an AHI greater than ten occurrences per hour may be at risk of being classified as having severe sleep apnea.

The AHI scale for children or adults can be utilized to diagnose AHI in adolescents.

AHI Drawbacks

Here are the major drawbacks of AHI.

1. Different Methods can be Used to Measure Hypopneas

Different Methods can be Used to Measure Hypopneas

The majority of knowledgeable individuals concur that the usual definition of apnea is a decrease in airflow of at least 90 percent. Hypopneas are more subjective than apneas because they occur when your airways collapse just partly. As a result, there is no universally accepted standard for defining hypopnea.

Hypopneas have been defined by specialists based on a specified percentage of reduced airflow, along with related shifts in blood oxygen levels or awakenings from sleep. These definitions have been the subject of experimentation. However, there is no single agreed-upon definition of hypopnea; hence, varying definitions might result in varied AHI values.

2. The Only Thing that the AHI Takes into Account is the Number of Respiratory Events

The only information that can be gleaned from the AHI is the frequency of pauses in breathing that occur while you are asleep. It does not shed light on any more significant aspects of that breathing incident that might indicate the severity of your OSA.

It does not demonstrate, for instance, how that break in breathing impacts the amounts of oxygen in your blood, which, if reduced frequently over time, may increase the risk of illnesses such as hypertension and diabetes.

The AHI does not take into account the length of time that an apnea or hypopnea occurs; rather, it just considers whether or not it lasts for at least 10 seconds. Therefore, people whose apneas linger for 30 seconds rather than 10 seconds are likely to have more severe repercussions as a result of their condition.

The AHI is an average that is obtained throughout the night. Therefore it does not indicate trends in breathing from hour to hour or correlations between sleep position and apneic occurrences.

This is due to the fact that the AHI represents an average. In addition, because the AHI is computed throughout the course of a single night in a sleep laboratory, it is possible that the result is not correct for a person whose AHI varies from night to night.

3. The AHI is Underestimated when Using Home Sleep Tests

The AHI is determined by home sleep tests depending on the overall recording time, compared to the entire sleep time assessed in a polysomnogram, which is measured with more precision. Consequently, home sleep studies frequently result in an underestimation of AHI by around 15 percent.

Because these limitations of the AHI have the potential to alter therapy, it is essential to be aware of them. For example, suppose clinicians just consider AHI when making therapy recommendations. In that case, they run the risk of ignoring other parts of the patient’s medical history as well as the symptoms that are associated with those characteristics.

For instance, standard OSA therapies may be less successful at lowering the risk of high blood pressure or other cardiovascular diseases in patients who have a high AHI but do not experience daytime sleepiness. Therefore, to provide a complete picture of obstructive sleep apnea (OSA), researchers are still arguing the most effective way to include additional diagnostic criteria such as daytime tiredness, oxygen saturation, and blood pressure.

Improve Your AHI Score

Ways to Improve Your AHI Score?

It’s possible that the pressure from the CPAP machine by itself won’t be enough to entirely get rid of all of your apneas and hypopneas. Even when you’re using your equipment, you may notice that your AHI is increasing at certain points throughout the day.

The good news is that there are several simple steps you may do to help lower your AHI.

1. Alter the Position in which You Sleep

Alter the Position in which You Sleep

Without making any adjustments to your pressure settings or equipment, you may reduce your AHI simply by altering the position in which you sleep—more specifically, by avoiding sleeping on your back. 

It is recommended by Sleep Care Online that you attempt to sleep on your side as often as possible because this sleep position lessens the likelihood of snoring and also improves blood circulation.

2. Replace the Cushion and the Headgear on Your Mask

Replace the Cushion and the Headgear on Your Mask

A greater AHI might be the result of older mask cushions and headgear that have been worn out. Make sure that your apparatus is properly cleaned and maintained at all times. In addition, ensure that you replace your headgear and mask cushions in accordance with the guidelines provided by the manufacturer. 

It is recommended that CPAP cushions be changed out once a month, and headgear should be changed out once every six months.

3. Change the Mask on Your CPAP Machine

Change the Mask on Your CPAP Machine

Your CPAP mask will ultimately start to wear down and may have leaks, much like your headgear, and mask cushions will eventually need to be replaced. After a certain amount of time, switching to a brand-new CPAP mask will provide the best results for your treatment with the device. About six to twelve months is the typical amount of time a mask is used. 

When replacing your CPAP mask, ensure you’re following the manufacturer’s guidelines.

4. Consider Wearing a Chinstrap or a Complete Face Mask

Consider Wearing a Chinstrap or a Complete Face Mask

Leaking from the lips is one of the most prevalent sources of air leaks! If you wear a nasal mask while you sleep but keep your mouth open, you will let some of the air out of your mouth even while the mask is on your nose. This may be avoided by using a full-face CPAP mask or a chin strap.

5. Ask Your Primary Care Provider or a Sleep Expert to Change the Pressure Settings on Your Device

Ask Your Primary Care Provider or a Sleep Expert to Change the Pressure Settings on Your Device

Your blood pressure demands may shift over time, particularly if there are major alterations to your health state, such as a loss or gain of a large amount of weight. Therefore, changing the pressure of your CPAP machine is something that should never be attempted without the guidance of a trained medical expert.

Final Note

An essential calculation known as the AHI is derived from a typical overnight sleep study known as a polysomnogram or from the results of sleep apnea testing performed in the patient’s home. As a part of these examinations, some sensors monitor airflow that is either positioned in the nose or close to the mouth.

Additionally, some belts are worn across the chest and stomach that expand in response to the act of breathing. Apnea episodes happen when the airway gets entirely clogged, and the mouth and nose record no airflow despite the chest and abdominal belts indicating that the individual is making an attempt to breathe.

Hypopnea is the condition that occurs when there is a reduction in airflow, even if it is just partial, but by at least 30 percent as determined based on a graph of the signal.

The AHI is also helpful for monitoring how well you respond to treatment with continuous positive airway pressure (CPAP). It is preferable to have a number that is lower than five incidents per hour, but the aim is to be within the typical range of occurrences.

When the parameters are optimized, reducing the AHI to 1 or 2 at the lowest is generally feasible.

Talk to your physician about the findings of the test and the treatment choices that would best meet your requirements if you have more questions about what the AHI implies for you specifically.

References