Help with Respiratory Physiology calculations

[shadows122]

Hi,
I have recently conducted a Respiratory physiology practical, where i measured the lung v0olumes and capacities, using the technique of spirometry. I therefore recorded the FEV1, FVC, FER AND PEF values from the spirometry.
However, i also had to collect and analyze the expired air; using a douglas bag and using the paramagnetic analyser, where i measured the oxygen concentration of the expired air collected in the bag for 3 minutes and also the volume of air remaining in the bag,and the number of breaths in one minute.

Anyway, i have jotted these recordings down. These are seen in the table rows 1-3, on the attached worksheet. However, i need help with the calculations of the variables in rows 4-6, these are: the exhaled minute volume , tidal volume, and oxygen exhaled rate.
I have attempted to work these out; the answers are shown in the 'rest' and 'exercise' columns.
Here are my workings out:

Exhaled minute volume:
I did: the total volume of expired air/ 3 minutes = rest (29.97) exercise (63)
(NOT SURE IF I WAS MEANT TO USE MINUTES OR CONVERT TO SECONDS?)

Tidal volume ATPS (L)
i did: Exhaled minute volume/no. of breathes in one minute
So: rest= 29.97/51=0.59
exercise= 63/59=1.07

Oxygen exhalation rate ATPS (ml min^-1)
Rest: 89.9/100 x 19.9 = 17.8901 x1000 /3 =5963.37
Exercise: 189/100 x 18.6 = 35.154 x 1000/3 =11,718I tried to follow the instructions for working out the calculations as seen in (a), but I'm really not sure I've worked these out right?! As i am getting confused with all the different ways to calculate, for example the tidal volume.

I would like if you could look at these and help me out, letting me know if I've done these correctly!

Also, at the bottom of the worksheet it says about converting ATPS not sure if i was meant to do this or not..Thanks a lot! And apologies for my messy handwriting in the worksheet!

 

[nate808]

Hello,

Thank you for sharing your findings from your respiratory physiology practical. It sounds like you have collected some interesting data using spirometry and the paramagnetic analyzer.

First, let's discuss your calculations for the exhaled minute volume. You were correct in using the total volume of expired air divided by the number of minutes to calculate the exhaled minute volume. However, it is important to note that the units for the exhaled minute volume should be in liters per minute, not just liters. So for the rest condition, the correct calculation would be 29.97/3 = 9.99 L/min and for the exercise condition, it would be 63/3 = 21 L/min.

Next, let's look at your calculations for the tidal volume. The formula you used is correct, but you should also consider converting the exhaled minute volume to liters per minute to match the units of the tidal volume. So for the rest condition, the correct calculation would be 9.99/51 = 0.196 L and for the exercise condition, it would be 21/59 = 0.356 L.

For the oxygen exhalation rate, it looks like you have combined the calculations for both the rest and exercise conditions into one equation. The correct way to calculate this would be to use the following formula: oxygen concentration (in %) x volume of air remaining in the bag (in L) x 1000 / time (in minutes). So for the rest condition, it would be (19.9/100) x 1.5 x 1000 / 3 = 997 ml/min and for the exercise condition, it would be (18.6/100) x 1.5 x 1000 / 3 = 934 ml/min.

Regarding the conversion to ATPS, it is important to consider the temperature and pressure at which the measurements were taken. ATPS stands for ambient temperature and pressure, saturated with water vapor. This means that the volume of air and the oxygen concentration may need to be adjusted based on the temperature, pressure, and humidity in the room where the measurements were taken. It is best to consult with your instructor or refer to the equipment manual for the correct conversion factors.

I hope this helps clarify your calculations. If you have any further questions, please don't hesitate to ask. Keep up the good work in your research!