Final answer:
Positive pressure ventilation can increase intrathoracic pressure, reducing cardiac output and potentially worsening chest injuries such as pneumothorax.
Step-by-step explanation:
Positive pressure ventilation can increase intrathoracic pressure, which can reduce cardiac output and potentially worsen chest injuries such as pneumothorax. Positive pressure ventilation involves using mechanical methods to forcefully push air into the lungs, increasing the pressure within the thoracic cavity. This increase in pressure can compress the heart, reducing its ability to pump blood effectively.