Reasons for the shift in oropharyngeal flora in patients receiving invasive mechanical ventilation with endotracheal tubes include which of the following?

a. Lowered pH levels
b. Increase in mucus-producing cells
c. Decreased production of proteases
d. Decreased mucosal immunoglobulin A

ANS: D
The shift in flora is most likely due to a number of factors that compromise host defense mecha-nisms. These include comorbidities, malnutrition, reduced levels of mucosal immunoglobulin A, increased production of proteases, exposed and denuded mucous membranes, elevated airway pH, and an increased number of airway receptors for bacteria as a result of acute illness and pre-vious antimicrobial use.