What do we call any portion of the airway that does not contain air and cannot participate in gas exchange?

The term used to describe any portion of the airway that does not contain air and cannot participate in gas exchange is "dead space." In the human respiratory system, dead space refers to areas where air is present but is not involved in the exchange of oxygen and carbon dioxide. This includes parts of the respiratory tract where air does not reach the alveoli, such as the trachea and bronchi, or portions of the lung that are ventilated but not perfused with blood.

Understanding dead space is crucial in emergency medical situations, as it impacts the efficiency of breathing and gas exchange. When assessing a patient's respiratory status, recognizing the significance of dead space can help EMTs determine the adequacy of ventilation and guide their interventions.

The other options do not convey the same meaning. Alveoli are the tiny air sacs where gas exchange occurs, ventilation refers to the process of moving air in and out of the lungs, and bronchioles are smaller branches of the respiratory tract that lead to alveoli. None of these terms encompass the concept of non-functional or non-gas exchanging portions of the airway like dead space does.