Which of the following findings is most closely associated with increased airway resistance?

Increased airway resistance is primarily characterized by the difficulty of airflow through the airways, which can lead to various physiological adaptations and clinical signs. Accessory muscle use is a direct response to increased airway resistance, as patients may struggle to breathe efficiently. When the airways are obstructed or narrowed, the body compensates by recruiting additional muscle groups, such as the sternocleidomastoid and scalene muscles, to facilitate breathing. This is especially evident during expiration, which can become labored in the presence of obstructive airway diseases such as asthma or chronic obstructive pulmonary disease (COPD).

The other findings do not directly indicate increased airway resistance. Reduced SpO2, for instance, may result from various conditions including but not limited to airway resistance—it signifies hypoxemia but does not specifically implicate it. Altered P50, on the other hand, refers to changes in hemoglobin's affinity for oxygen, and while it can be affected by various physiological factors or conditions, it does not correlate directly with airway resistance. Increased PetCO2 reflects issues related to ventilation and may occur with inadequate gas exchange, potentially in the context of compromised ventilation but does not specifically point to increased airway resistance. Thus, the use of accessory muscles is the