Which of the following is a key sign of respiratory distress in patients?

The key sign of respiratory distress in patients is the use of accessory muscles during breathing. This indicates that the patient is experiencing difficulty in breathing, requiring additional muscle involvement beyond the diaphragm and intercostal muscles. Healthy breathing relies primarily on these muscles; however, when a patient is in respiratory distress, they may engage neck and shoulder muscles to assist with inhalation, indicating their struggle to obtain enough oxygen. This observable physical effort is a clear indication that the respiratory system is under stress and not functioning effectively.

Other factors such as rapid heart rate, low oxygen saturation, or excessive coughing can be associated with respiratory issues but are not as direct a sign of distress. Rapid heart rate may occur due to a variety of reasons, including anxiety or other medical conditions, while low oxygen saturation is a consequence of respiratory issues rather than an observable physical sign. Excessive coughing can indicate irritation or inflammation within the airway but does not necessarily reflect the immediate mechanical effort of breathing that the use of accessory muscles signifies. Therefore, recognizing the use of accessory muscles is crucial in evaluating the patient's respiratory status and determining the urgency of medical intervention.