What effect does increasing O2 flow have on the thrope tube's ball position?

• A. The ball moves down
• B. The ball stays in place
• C. The ball moves up
• D. The ball oscillates

Answer: (C)

Increasing the oxygen flow through a flowmeter with a Thorpe tube design leads to an increase in the flow of gas in the tube, which in turn affects the position of the flow indicator, commonly a ball or a float. As the flow rate increases, the gas velocity also increases, creating a differential pressure that lifts the ball or float higher in the tube.

The design of the Thorpe tube ensures that the ball rises to a position that corresponds to the rate of flow being delivered. Since the ball is influenced by the force of the gas flowing upwards and the weight of the ball itself, an increase in the flow rate results in the ball moving upward to a new equilibrium position. This upward movement allows for a clear visual indication of the increased flow, which is essential for proper monitoring during anesthesia. Thus, the change in the ball's position is directly proportional to the change in gas flow.