Airway, Respiration, and Ventilation Study Guide for the EMT Test

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General Information

Questions in this area on the EMT test concern everything related to the process of breathing. You’ll need to know the parts of the body that make breathing possible and how each one functions. You need to be able to use techniques and equipment appropriately during an emergency, when it is necessary to make breathing possible or more easily achieved. Here are the most important things you need to study. Be sure you thoroughly understand each topic and seek further information in your textbook about specific procedures. Also, know the meaning and significance of all of the terms listed.

Respiratory System Anatomy

The respiratory system is divided into two sections, the upper airway and the lower airway. All the structures of both sections play a role in breathing and gas exchange.

Upper Airway

The upper airway is made up of the mouth, or oral cavity, the nose, tongue, jaw, larynx, and pharynx. The main function of the upper airway is to serve as a passage for air to be inhaled and exhaled out of the lungs. The upper airway also humidifies and heats the air.

Terms/Concepts to Know: respiratory system, nasopharynx, trachea

Lower Airway

The lower airway consists of the trachea and the lungs. The trachea divides into the right and left mainstem bronchi. The bronchi branch into the right and left lung. The lungs are further divided into lobes. The left lung consists of two lobes, the upper and lower. The right lung is composed of the upper, middle, and lower lobes. Each lobe is made up of millions of alveoli, which are tiny air sacs where gas exchange occurs.

Terms/Concepts to Know: thyroid cartilage, cricoid cartilage, cricothyroid membrane, alveoli

Differences in Child and Adult Airways

There are several differences between a child’s airway and an adult’s. Overall, a child’s upper and lower airways, which include the nose, mouth, and trachea, are smaller and more flexible than an adult’s. Smaller structures may mean an airway obstruction occurs easier in a child than an adult. Although a child’s tongue is also smaller proportionally, it takes up more space.

Respiratory System Physiology

The physiology of the respiratory system includes respiration and ventilation. The process of both respiration and ventilation is involuntary, which means it is done reflexively, without the person thinking about it. It’s important to understand the difference between ventilation, oxygenation, and respiration.


Ventilation in simple terms refers to breathing. It involves the act of inhaling air in and exhaling air out of the lungs. Ventilation requires structures, such as the diaphragm and intercostal muscles, to work together and contract, allowing for inhalation. During exhalation, the muscles relax. If ventilation is inadequate, oxygenation will also be insufficient and the need for ventilatory assistance should be assessed.

Terms/Concepts to Know: inhalation, exhalation, partial pressure, dyspnea


Oxygenation refers to the delivery of oxygen into the hemoglobin in the blood cells. Oxygen is needed for the organs and tissues of the body to function properly. Oxygenation can be disrupted due to various physiological states, as well as being at high altitudes and in places where the percentage of oxygen in the air is decreased, such as a confined space. Signs of poor oxygenation include confusion, tachypnea, and cyanosis.

Terms/Concepts to Know: hypoxia, hypoxic drive, cyanosis, tachypnea


The cells in the body require oxygen and the removal of carbon dioxide. Respiration refers to gas exchange that occurs in the lungs. Oxygen is received through inhalation and carbon dioxide is removed through exhalation. Physiological processes, including diffusion, allow respiration to occur. Adequate ventilation is essential for proper respiration to take place. But even if ventilation is acceptable, it does not guarantee that gas exchange at the cellular level is sufficient.

Terms/Concepts to Know: external respiration, surfactant, cellular respiration

Respiration Pathophysiology

Respiration is more complicated than it may seem. Various systems of the body work together for adequate respiration to occur, but it can be disrupted due to a variety of factors.

Nervous System Factors

The nervous system plays a role in respiration. Chemoreceptors in the nervous system monitor the pH of the spinal fluid, as well as the level of oxygen and carbon dioxide in the body. Based on those levels, the nervous system sends signals to the respiratory centers in the brain to change the respiratory rate or depth of breathing.

Terms/Concepts to Know: chemoreceptors

Ventilation/Perfusion Ratio and Mismatch

The ventilation and perfusion ratio refers to air flowing into the lungs and blood going to the lungs. The two variables should be matched. Insufficient gas exchange is often caused by a mismatch in the perfusion to ventilation ratio.

Pulmonary Ventilation Factors

Pulmonary factors that affect adequate ventilation can be intrinsic or extrinsic. Intrinsic factors may include allergic responses, lung infections, and the blockage of the flow of air in and out of the lungs, such as when the tongue is blocking the airway. Extrinsic factors can include blockage of the airway due to a foreign body or trauma to the chest or airway.

Terms/Concepts to Know: hypercapnia

Respiration Factors

Both internal and external conditions can affect respiration. External factors include altitude and the partial pressure of oxygen. Carbon monoxide in the environment can also affect proper respiration. Internal factors involve diseases and conditions that decrease the surface area of the portion of the lung involved in gas exchange. Examples include COPD, infection, and pulmonary edema.

Terms/Concepts to Know: intrapulmonary shunting

Circulatory Compromise

Conditions that affect circulation also play a role in efficient respiration. Certain conditions can decrease oxygenation at the tissues. An interruption of blood flow to the tissues can be due to a pulmonary embolism, tension pneumothorax, or a variety of traumatic injuries. In other instances, cardiac problems may prevent the heart from effectively pumping oxygenated blood to the tissues and organs of the body.

Terms/Concepts to Know: tension pneumothorax, pulmonary embolism

Assessment of Patient

Assessing a patient’s breathing is one of the first steps in providing care. When performing a respiratory assessment, several factors must be considered.

Adequate versus Abnormal Breathing

There are several factors to consider when determining adequate breathing. Respiratory rate should be assessed to determine if it is abnormally high or low. The patient’s “work of breathing” should also be evaluated, including whether the breathing is labored. The depth of breathing and the patient’s level of consciousness also needs to be assessed.

Terms/Concepts to Know: work of breathing, labored breathing, retractions, agonal gasps, Cheyne-Stokes, apnea, ataxic respirations

Respiration Assessment

Even if breathing appears normal, gas exchange may still be inadequate. In a prehospital setting, using a pulse oximeter is one way to assess oxygenation. A brief patient assessment of respiration should also include determining level of consciousness, which can be affected if the patient is hypoxic or if carbon dioxide levels are too high. Skin color, specifically a bluish tint to the skin, lips, and nails, also indicates problems oxygenating.

Terms/Concepts to Know: pulse oximetry, capnography, end-tidal \(Co_2\)


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