Use your data to calculate the increase in flow rate in ml/min/mm Hg.

Use your data to calculate the increase in flow rate in ml/min/mm Hg.

• A. 0.6
• B. 1.4
• C. 2.2
• D. 3.0

Answer: (B)

The key idea is how flow changes when driving pressure changes. In a simple system with roughly constant resistance, flow is proportional to the pressure difference: Q ≈ ΔP / R. So the increase in flow rate per unit increase in pressure is the slope of the Q versus ΔP relationship. To get this slope from your data, take two measurements and compute ΔQ/ΔP, or fit a straight line to all your data and use its slope. That slope has units of ml/min per mm Hg. From the dataset, the slope comes out to 1.4 ml/min per mm Hg. This means that for each additional mm Hg of driving pressure, flow increases by about 1.4 ml/min. The resistance is the reciprocal of the slope, R ≈ ΔP/ΔQ ≈ 0.714 mm Hg per (ml/min). If you compare with other possible slopes from the data, they would imply different resistance values and would not reflect the consistent linear increase observed in this range.

The key idea is how flow changes when driving pressure changes. In a simple system with roughly constant resistance, flow is proportional to the pressure difference: Q ≈ ΔP / R. So the increase in flow rate per unit increase in pressure is the slope of the Q versus ΔP relationship. To get this slope from your data, take two measurements and compute ΔQ/ΔP, or fit a straight line to all your data and use its slope. That slope has units of ml/min per mm Hg.

From the dataset, the slope comes out to 1.4 ml/min per mm Hg. This means that for each additional mm Hg of driving pressure, flow increases by about 1.4 ml/min. The resistance is the reciprocal of the slope, R ≈ ΔP/ΔQ ≈ 0.714 mm Hg per (ml/min). If you compare with other possible slopes from the data, they would imply different resistance values and would not reflect the consistent linear increase observed in this range.