Final answer:
Positive End Expiratory Pressure (PEEP) is a therapeutic technique used to maintain a pressure above atmospheric levels in the lungs at the end of passive exhalation, aiding in keeping alveoli open and improving gas exchange.
Step-by-step explanation:
The term Positive End Expiratory Pressure (PEEP) refers to a mode of therapy used in mechanical ventilation to maintain a pressure in the lungs above atmospheric level at the end of passive exhalation. This pressure helps to keep the alveoli open, preventing their collapse (atelectasis), and improves the functional residual capacity (FRC) of the lungs, thereby enhancing the gas exchange process within the lungs. In a spontaneously breathing patient, PEEP can be achieved naturally through pursed-lip breathing, which creates backpressure in the airways, or it can be applied externally using mechanical ventilation.
The normal process of expiration is passive and relies on lung elasticity and the relaxation of inspiratory muscles, leading to increased intrapulmonary pressure and the exhalation of air. The pressure within the lungs, or intra-alveolar pressure, fluctuates with the breathing cycle but ultimately equilibrates with the atmospheric pressure.