Final answer:
Adding PEEP to positive pressure ventilation increases functional residual capacity and improves oxygenation.
Step-by-step explanation:
The purpose of adding PEEP (positive end-expiratory pressure) to positive pressure ventilation is to increase functional residual capacity (FRC) and improve oxygenation. PEEP is a therapy used in mechanical ventilation to keep the alveoli in the lungs open during expiration, preventing them from collapsing completely. It increases lung volume and helps to recruit and open up previously closed airways, thus improving oxygenation.