Accessory muscle breathing means using muscles other than those typically used for breathing to take in and expel air. One example is the subclavius — between the collarbone and the top rib — which usually stabilizes the rib cage.
People with certain medical conditions and young children with muscles that are not yet fully developed may find it difficult to take in enough air using only their primary breathing muscles.
In this case, they must rely on additional, or accessory, muscles to help them breathe.
This article discusses what accessory muscles are and when and why the body may use them.
Most people can breathe without thinking about it. This is an involuntary action.
However, individuals can also take deliberate breaths. For instance, during breathing practices, such as during yoga or childbirth. This makes breathing more of a voluntary action.
Learn more about lung function here.
Involuntary breathing requires airway resistance muscles, which
- the skeletal muscles of the tongue
- the hyoglossus, styloglossus and stylohyoid muscles
- the glottis
- the larynx
- the pharynx
- smooth bronchi muscles
Accessory muscles, such as the sternocleidomastoid and scalene muscles, help stabilize the rib cage. Other muscles
- abdominal muscles
- upper trapezius
- internal intercostals
- posterior inferior
The body uses different accessory breathing muscles for breathing in and breathing out.
Inspiration means breathing in or inhalation. The accessory muscles of inspiration
Accessory muscles of inspiration
- the sternocleidomastoid
- the upper trapexius
- the serratus anterior
- the latissimus dorsi
- the iliocostalis thoracis
- the subclavius
Expiration means breathing out or exhalation and is typically a passive process.
Accessory muscles of expiration
- internal intercostals
- abdominal muscles
- quadratus lumborum
- serratus anterior
- serratus posterior inferior
- latissimus dorsi
For a person in good health, the accessory muscles are not active during regular breathing.
However, they may use these muscles when taking a deliberately deep breath. For example, they can involve them when swimming underwater or forcefully expelling air to blow out birthday cake candles.
If someone has a condition that makes breathing more difficult, the body may automatically activate the accessory muscles during typical breathing. Different life stages may also influence accessory muscle breathing.
It is common to use the accessory muscle to help compensate for respiratory conditions leading to hypoxemia, a lower than typical level of oxygen in the blood, or hypercapnia, when the blood’s carbon dioxide level rises above typical levels.
A person can also use the muscle for systemic conditions that lead to metabolic acidosis, which is when there is excessive acid in their bodily fluids.
COPD is an umbrella condition that makes it more difficult to breathe. It may force the body to activate accessory muscles for expiration.
This leaves the muscles unable to move enough air into and out of the lungs, leading to the use of accessory muscles.
When examining a person with shortness of breath during end-of-life care, doctors look for abnormalities in their breathing rate.
Additionally, the area between their ribs and neck can sink in when they try to breathe in.
The researchers explained that the diaphragm of a newborn is not as strong and more likely to fatigue compared with that of an older child or adult.
When this fatigue sets in, the newborn’s body recruits the accessory muscles to help them keep breathing.
Young children are also more prone to:
- losing oxygen from their blood
- airway obstruction
- fatigue or collapse of the lung
Additionally, their intercostal muscles are not yet properly developed, so they are not as effective in their role as breathing accessory muscles.
If a person appears to be working harder than usual to breathe, it is important to contact a doctor as soon as possible. The doctor will aim to find and treat any underlying causes.
If a person with COPD is using their accessory muscles to help them breathe, their doctor may recommend a technique called pursed-lip breathing.
This breathing technique may help them breathe out
Accessory muscle breathing means using muscles other than those people typically use for breathing to take in and expel enough air.
The body uses certain muscles, including the diaphragm, for inhalation, whereas exhalation is more of a passive process.
Accessory muscle breathing may result from deliberate breathing practices or strenuous exercise. It may also be due to a health condition.
People should contact a doctor as soon as possible if a person appears to be working harder than usual to breathe.