Which of the following physiologic effects is the most immediate result stemming from the desiccation of mucous glands which, in turn, causes an increased viscosity of the mucus, produced by breathing a cool, dry gas via an artificial airway?

A. retained secretions
B. hyperthermia
C. atelectasis
D. refractory hypoxemia

?ANS: C
A. Incorrect response: When a patient breathes a cool, dry gas through an artificial airway, the physiologic response of retained secretions is caused by the structural problem of ciliary function loss, adversely affecting the mucociliary escalator.
B. Incorrect response: Breathing such a gas through an ETT or tracheostomy tube can cause hypothermia, not hyperthermia.
C. Correct response: Atelectasis develops as mucous viscosity increases because of the desiccation of mucous producing glands, caused by breathing cool, dry gas through an artificial airway.
D. Incorrect response: Refractory hypoxemia ensues from the development of atelectasis. Once the alveoli collapse, pulmonary capillary blood flow continues, and the blood perfusing these atelectatic alveoli does not participate in gas exchange. Therefore, blood leaving these atelectatic alveoli retains its mixed venous blood gas values.