Respiratory Volumes Problem Set

RESPIRATORY VOLUMES PROBLEM SET

1.  Jessie decides to go running. Assuming that this is mild exercise, what would her respiratory rate have to be in order for her to maintain an alveolar ventilation of 6.0 L/min? (Assume that Jessie’s tidal volume and anatomical dead space are those of an average individual) (3 pts)

VA = (VT-VD) x f

6.0 L/min = (500 ml/breath - 150 ml/breath) x f

6.0 L/min = 350 ml/breath x f

6.0 L/min / 0.350 L/breath = f

f = 17 breaths/min

2.  Peter experiences some shortness of breath during moderate levels of activity. He is checked out by a physician, and is told his lungs and heart appear to be fine, but he is sent for more testing. He goes through some respiratory diagnostic procedures that result in the following information:

Inspiratory capacity – 3865 ml

Inspiratory reserve volume – 3400 ml

Expiratory reserve volume – 950 ml

Respiratory rate – 14 breaths/min

Given this information, calculate Peter’s vital capacity. (2 points)

Vital Capacity = ERV + IC = 950 ml + 3865 ml = 4815 ml

Is his vital capacity approximately normal? (1 point)

Yes - average = 4600 ml, so he is approximately normal.

Peter’s physician decides to check his alveolar minute ventilation as well. Using the information above, and the accepted average volume of the anatomical dead space, calculate Peter’s alveolar minute ventilation. (2 points)

IC - IRV = VT VT = 3865 ml - 3400 ml = 465 ml/breath

VA = (VT-VD) x f VA = (465 ml/breath - 150 ml/breath) x 14 breaths/min = 4410 ml/min

Is his alveolar minute ventilation approximately normal? (1 point)

Yes - average would be between 4200 ml/min and 6300 ml/min