Which of the following is a sign of effective ventilation?

Effective ventilation can be identified by certain observable physical signs. One of the most definitive signs is the visible rise and fall of the chest. This indicates that air is effectively being moved into and out of the lungs, allowing for gas exchange to occur. When the chest rises during inhalation and falls during exhalation, it confirms that the ventilatory process is functioning properly and that adequate air is reaching the alveoli in the lungs.

In contrast, the absence of breath sounds may indicate an obstruction in the airway or that air is not reaching the lungs, rendering it an unreliable indicator of effective ventilation. A rapid heart rate can be a physiological response to insufficient oxygenation or stress but does not necessarily reflect effective ventilation itself. Lastly, a persistent cough is typically a reflex action in response to irritation or obstruction within the respiratory system and does not indicate effective ventilation, as it can sometimes suggest that ventilation is compromised.

Thus, the visible rise and fall of the chest directly correlates with the effectiveness of ventilation and is a clear indicator of proper breathing mechanics.