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AS Academic Tutorial 6

AS Academic Tutorial 6. Spirometer calculations and exam technique. Using a spirometer to measure breathing volumes and rate. http://advancedsciences.cambridge.org/ocr/biology_1/animation/8827. Labelling the Spirometer Trace. Expiratory Reserve Volume. Tidal Volume. Vital Capacity.

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AS Academic Tutorial 6

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

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

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

  4. Calculations On our college paper, 4 small squares = 1 dm3 for volume calculations. (see previous slide or your sheet – how many small squares = 1 dm3?) 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 dm3 or 1000 cm3, so 1 square = 1000 = 166.6 cm3 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 cm3 • Vital Capacity = 4 dm3 from graph • Inspiratory Reserve Volume = 8 x 166.6 = 1332.8 cm3 or 1.3 dm3 • Expiratory Reserve Volume = 12 x 166.6 = 1.9 dm3 • 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 CO2 is removed as you breath, so the total volume decreases in proportion to the volume ofO2 used up by aerobic respiration. B A 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. Calculate the O2 absorbed as shown by trace A and B.

  8. Calculate the O2 absorbedas 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 cm3 • So, 1 mm = 1000 = 90.9 cm3 11 • So 10 mm drop in trace = 10 x 90.9 = 909 cm3 oxygen used up over 115 s. • 909 = 7.9 cm3 per s and 7.9 x 60 cm3 per min = 474 cm3 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 cm3 • So, 1 mm = 1000 = 58.8 cm3 17 • So 12 mm drop in trace = 12 x 58.8 = 706 cm3 oxygen used up over 1 min = 706 cm3 per min.

  10. Now for some exam questions…..

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