1. AS Academic Tutorial 6 Spirometer calculations and exam technique.

2. Using a spirometer to measure breathing volumes and rate http://advancedsciences.cambridge.org/oc r/biology_1/animation/8827http://advancedsciences.cambridge.org/oc r/biology_1/animation/8827

3. Labelling the Spirometer Trace Tidal Volume Vital Capacity Inspiratory Reserve Volume Expiratory Reserve Volume

4. Calculations On our college paper, 4 small squares = 1 dm 3 for volume calculations. (see previous slide or your sheet – how many small squares = 1 dm 3 ?) Rate of breathing = 1 mm = 1 second (on our kymographs). Therefore 8 breaths in 20 mm, (so 20 seconds) = 8 in 1 second and 8 x 60 in 60 s. 20 20 = 24 breaths per minute.

5. Calculate: tidal volume, vital capacity, inspiratory reserve volume, expiratory reserve volume, breathing rate at rest and finally during exercise.

6. Answers Volume: 6 small squares = 1 dm 3 or 1000 cm 3, so 1 square = 1000 = 166.6 cm 3 6 Time: 3 small squares = 5 s, so 1 square = 5 = 1.66 s 3 Tidal Volume = 4 squares = 4 x 166.6 = 666.6 cm 3 Vital Capacity = 4 dm 3 from graph Inspiratory Reserve Volume = 8 x 166.6 = 1332.8 cm 3 or 1.3 dm 3 Expiratory Reserve Volume = 12 x 166.6 = 1.9 dm 3 Breathing Rate during exercise = 4 breaths in 10 s so 0.4 in 1 s, and 0.4 x 60 in 1 min = 24 breaths per min. Breathing Rate at rest = 2 breaths in 10 s, so half the rate during exercise, so 12 breaths per min.

7. Remember the CO 2 is removed as you breath, so the total volume decreases in proportion to the volume of O 2 used up by aerobic respiration. Calculate the O 2 absorbed as shown by trace A and B. A B Oxygen is used up by respiration and the same volume of carbon dioxide produced. However, soda lime absorbs carbon dioxide, so the total volume of air drops by the volume of oxygen used up.

8. Calculate the O 2 absorbed as shown by trace A. From x axis, 11 mm = 20 s So, 1 s = 11 = 0.55 mm 20 As distance along x = 63 mm, 63 = 115 s time along x. 0.55 From y axis, 11 mm = 1000 cm 3 So, 1 mm = 1000 = 90.9 cm 3 11 So 10 mm drop in trace = 10 x 90.9 = 909 cm 3 oxygen used up over 115 s. 909 = 7.9 cm 3 per s and 7.9 x 60 cm 3 per min = 474 cm 3 per min. 115 NOW YOU CALCULATE TRACE B!

9. Answers to B trace From x axis, 8 mm = 10 s So, 1 s = 8 = 0.8 mm 10 As distance along x = approx 48 mm, how many 0.8 in 48? = 60 s or 1 min. From y axis, 17 mm = 1000 cm 3 So, 1 mm = 1000 = 58.8 cm 3 17 So 12 mm drop in trace = 12 x 58.8 = 706 cm 3 oxygen used up over 1 min = 706 cm 3 per min.

10. Now for some exam questions…..