Stand behind patient and place your hands behind the sternomastoid and feel the scalene muscles during quiet respiration. If the muscle contraction is palpable during quiet tidal breathing, the accessory muscles are in use.
The body uses different accessory breathing muscles for breathing in and breathing out. Inspiration means breathing in or inhalation. The accessory muscles of inspiration lift the third, fourth, and fifth ribs to increase space for air in the lungs.
The rib cage muscles, including the intercostals, the parasternals, the scalene and the neck muscles, mostly act on the upper part of the rib cage (pulmonary rib cage) and are both inspiratory and expiratory. The abdominal muscles act on the abdomen and the abdominal rib cage and are expiratory.
Accessory Muscles
The accessory expiratory muscles are the abdominal muscles: rectus abdominis, external oblique, internal oblique, and transversus abdominis.
The diaphragm is the major muscle responsible for breathing. It is a thin, dome-shaped muscle that separates the abdominal cavity from the thoracic cavity. During inhalation, the diaphragm contracts, so that its center moves caudally (downward) and its edges move cranially (upward).
During an asthma attack greater pressure is needed to push air through the bronchus. This results in the increased use of accessory muscles to breathe. These muscles are attached to the ribs, shoulders and neck. This extra work results in sweating, fatigue and airway irritation.
Dysfunctional Breathing and the Kinetic Chain
For example, individuals who possess an upper crossed syndrome (rounded shoulders, forward head) typically exhibit overactivity/tightness of the upper trapezius, scalenes, sternocliedomastoid, levator scapulae, and pectoralis minor (secondary respiratory muscles) (5).
Accessory muscle use/retractions.
The chest appears to sink in just below the neck, under the breastbone, or between the ribs with each breath as a way of trying to bring more air into the lungs.
Asking the child to take deep breath (“big breaths”) auscultate the front and back of the chest. Compare right to left in a 'Z' pattern. Note any noises such as wheezing or crackles on the inspiratory or expiratory phase of the respiration cycle. Document your findings.
To test for paradoxical breathing, a person can lie on their back and take a deep breath. The chest and abdomen should expand when they inhale and contract when they exhale. If the chest and abdomen contract while inhaling and expand while breathing out, a person may have paradoxical breathing.
These accessory muscles of inspiration include the sternocleidomastoid, pectoralis minor and major, serratus anterior, latissimus dorsi, and serratus posterior superior muscles.
Symptoms and signs — The clinical features of respiratory muscle weakness are those associated with inadequate ventilation, ineffective cough, and bulbar dysfunction.
Tight muscles can absolutely cause breathing difficulty. There are certain muscles involved in both the exhalation and inhalation process. If any of these muscles become tight, overused or develop trigger point activity (commonly referred to as a knot in the muscle) then this muscle's function may be inhibited.
Wheezes are heard more commonly during expiration because the airways normally narrow during this phase of respiration. Wheezing during expiration alone is generally indicative of milder obstruction than if present during both inspiration and expiration, which suggests more severe airway narrowing.
During an asthma attack, the muscles around the airways tighten, or “spasm” (like when you make a fist), and the lining inside the airways swells or thickens, and gets clogged with lots of thick mucous. This makes the airways much skinnier than usual so it is harder to move air in and out of the air sacs.
Respiratory muscle fatigue is caused by excessive effort relative to the strength and endurance of the respiratory muscles.
Diaphragm. The diaphragm is a musculotendinous structure that separates the thoracic and abdominal cavities. It is the muscle that is primarily responsible for respiration.
ACCESSORY MUSCLE ACTIVITY
Dynamic hyperinflation and air trapping in COPD patients place the diaphragm and intercostal muscles in a mechanically disadvantageous position. Because of this, the diaphragm and intercostals are unable to provide adequate ventilation, leading to the recruitment of accessory muscles.
The most important muscle of inspiration is the diaphragm; however, the external intercostals assist with normal quiet breathing. Contraction of the diaphragm increases the space in the thoracic cavity and the lungs fill with air from the external environment.
There are two main groups of inspiratory muscles: principal and accessory. Principal muscles are used regardless of the level of breathing required, while accessory muscles are only used during forced breathing. For example, during heavy exercise and because of some respiratory conditions such as Asthma.
Paradoxical breathing is when the chest expands during inhalation and the abdomen is drawn inwards and then during exhalation the abdomen is pushed outwards. A new BPD classification, proposed by the authors of this commentary, is associated with a startle reflex.
Paradoxical breathing during weakness or paralysis of the diaphragm is described as a "seesaw" motion between the chest wall and the abdominal wall. As the chest expands, abdominal organs move up and seemingly behind the sternum, causing the abdominal wall to contract.
Seesaw motion is a type of paradoxical respiration, suggesting impaired gas exchange that might require mechanical ventilation. Seesaw motion suggests or predicts respiratory failure due to diaphragmatic or respiratory muscle fatigue.