Which of the following is the most determinant of cough effectiveness?

The effectiveness of a cough is primarily influenced by the depth of inhalation. When a person inhales deeply, it allows for greater lung expansion and increased volume of air to be expelled during the cough reflex. A deep inhalation prepares the lungs to generate a higher intrathoracic pressure, which can enhance the force and velocity of the expelled air. This is essential for clearing secretions and irritants from the airways.

A shallow cough, which would occur with insufficient depth of inhalation, can lead to ineffective clearance of airway obstructions or retained secretions. Therefore, maximizing the depth of inhalation is crucial for an effective cough, making it the most determinant factor in this context.

While factors like FRC size, maximum inspiratory pressure (MIP), and spontaneous tidal volume (VT) are important for overall pulmonary function, they do not directly impact the immediate effectiveness of a cough in the same way that the depth of inhalation does.