EMR – Emergency Medical Responder

The respiratory system serves as the body's mechanism for gas exchange. Oxygen enters the body through inhalation and travels to the lungs where it diffuses into the bloodstream. Carbon dioxide, a metabolic waste product, moves from the blood into the lungs and exits through exhalation. Understanding this system is fundamental for emergency medical responders because respiratory compromise is one of the most time-sensitive emergencies you will encounter.

The respiratory system consists of two main divisions. The upper airway includes the nose, mouth, pharynx, and larynx. The lower airway includes the trachea, bronchi, bronchioles, and alveoli. Each structure plays a specific role in moving air and facilitating gas exchange.

The nose and mouth serve as entry points for air. The nose warms, humidifies, and filters incoming air through its mucous membranes and hair-like structures called cilia. The mouth serves as an alternative entry point, especially during periods of increased oxygen demand such as exercise or respiratory distress.

The pharynx is a muscular tube extending from the base of the skull to the esophagus. It consists of three regions: the nasopharynx behind the nose, the oropharynx behind the mouth, and the laryngopharynx near the larynx. The pharynx serves as a shared pathway for both air and food.

The larynx, commonly called the voice box, sits at the top of the trachea. It contains the vocal cords and the epiglottis, a flap of tissue that prevents food and liquid from entering the airway during swallowing. The larynx also contains the glottic opening, which is the narrowest part of the adult airway.

The trachea is a tube approximately 10 to 12 centimeters long supported by C-shaped cartilage rings. These rings keep the airway open while allowing the esophagus behind it to expand during swallowing. The trachea divides into the right and left main bronchi at a point called the carina.

The bronchi branch repeatedly into smaller tubes called bronchioles. These eventually terminate in tiny air sacs called alveoli. The alveoli are surrounded by capillaries and serve as the site of gas exchange. Adult lungs contain approximately 300 million alveoli, providing a massive surface area for oxygen and carbon dioxide transfer.

Normal breathing, also called eupnea, is an automatic process controlled by the brainstem. The medulla oblongata and pons contain respiratory centers that regulate breathing rate and depth based on carbon dioxide levels, oxygen levels, and blood pH.

The primary stimulus for breathing in healthy individuals is rising carbon dioxide levels in the blood. Chemoreceptors in the brain and major blood vessels detect this increase and signal the respiratory centers to increase breathing rate and depth. This mechanism is called the hypercapnic drive.

Normal respiratory rates vary by age. Adults typically breathe 12 to 20 times per minute. Children aged 1 to 8 years breathe 15 to 30 times per minute. Infants breathe 25 to 50 times per minute. These rates increase during exertion, fever, pain, or emotional stress.

Normal breathing has specific characteristics you should recognize. Breathing should be quiet and effortless. The chest should rise and fall symmetrically with each breath. There should be no use of accessory muscles such as the neck, shoulder, or abdominal muscles. The skin should be pink and warm, indicating adequate oxygenation.

Tidal volume refers to the amount of air moved in and out of the lungs during a normal breath. Adult tidal volume is approximately 500 milliliters. Minute volume is the total amount of air moved in one minute, calculated by multiplying tidal volume by respiratory rate. Normal adult minute volume is approximately 6 to 8 liters per minute.

The mechanics of breathing involve the diaphragm and intercostal muscles. During inhalation, the diaphragm contracts and moves downward while the intercostal muscles contract and move the ribs outward and upward. This increases the volume of the thoracic cavity, creating negative pressure that draws air into the lungs. Exhalation is normally passive, occurring when the diaphragm and intercostal muscles relax and the elastic recoil of the lungs pushes air out.

Adequate breathing is characterized by a normal respiratory rate for age, regular rhythm, adequate depth evidenced by chest rise, bilateral breath sounds, and normal skin color. You should assess breathing by looking at chest movement, listening for breath sounds and air movement, and feeling for air from the nose and mouth.

Inadequate breathing presents with abnormal respiratory rates, irregular rhythm, shallow depth, unequal or diminished breath sounds, and abnormal skin color such as pallor, cyanosis, or mottling. Patients with inadequate breathing may also demonstrate altered mental status, use of accessory muscles, nasal flaring, and retractions.