Final answer:
To determine the minimum flow rate that will meet the patient's inspiratory demand, calculate the minute ventilation and the flow rate from the device. The calculated flow rate should not be lower than the current flow rate from the device. So, the correct option is
D. 8 L/min
Step-by-step explanation:
To determine the minimum flow rate that will meet the patient's inspiratory demand, we need to calculate the minute ventilation.
The minute ventilation is the amount of air that the patient inhales in one minute.
It can be calculated by multiplying the tidal volume by the respiratory rate.
In this case, the tidal volume is 700 mL and the respiratory rate is 30/min.
So the minute ventilation is 700 mL x 30/min = 21,000 mL/min.
The heated aerosol therapy device is set at 40% entrainment.
This means that 40% of the inspired air will come from the device, while the remaining 60% will come from room air.
The flow rate from the device is 15 L/min.
Since we need to meet the patient's inspiratory demand, we only need to calculate the flow rate coming from the device.
The flow rate from the device can be calculated by multiplying the minute ventilation by the fraction of inspired air coming from the device. In this case, the minute ventilation is 21,000 mL/min and the fraction of inspired air coming from the device is 0.4.
So the flow rate from the device is 21,000 mL/min x 0.4 = 8,400 mL/min. To convert mL/min to L/min, divide by 1000.
Therefore, the flow rate from the device is 8.4 L/min.
Since the flow rate from the device is already 15 L/min, which is higher than the calculated flow rate of 8.4 L/min, it means that the patient's inspiratory demand can be met with the current flow rate.
Therefore, the minimum flow rate that will still meet the patient's inspiratory demand is 15 L/min.
Therefore, the correct option is D. 8 L/min