Final answer:
Exhaling with the glottis partially closed is a technique used in forced breathing to increase positive end-expiratory pressure, engaging accessory muscles to actively expel air from the lungs and help improve oxygenation.
Step-by-step explanation:
Exhaling with the glottis partially closed is a technique that increases positive end-expiratory pressure (PEEP). This is part of forced breathing, or hyperpnea, which is common during activities requiring active regulation of breathing such as exercise. The epiglottis is a leaf-shaped piece of elastic cartilage in the larynx that helps prevent food from entering the trachea. Expiration, or exhalation, is defined as the process by which air leaves the lungs. The expiratory reserve volume (ERV) is the additional air that can be forcefully exhaled after a normal tidal exhalation.
During normal exhalation, air leaves the lungs passively, without the need for muscular effort, due to the elasticity of lung tissue causing the lung to recoil. However, during forced exhalation, accessory muscles such as the internal intercostals and abdominal muscles engage to help expel air from the lungs. By partially closing the glottis, an individual can create a higher resistance to the air leaving the lungs, thereby increasing the pressure within the lungs at the end of expiration, known as PEEP. PEEP is beneficial in certain respiratory therapies as it can help keep the alveoli open and improve oxygenation.