Question

In this lab, you will be breathing into a 5 L mixing chamber. The mixing chamber will start with “regular” air (20.93 vol% O₂, 0.04 vol% CO₂, and 79.03 vol% N₂). You will inhale air through your nose (which is exposed to “regular” air) and exhale through your mouth into the mixing chamber. As your exhaled air is added into the chamber, an equal volume of air leaves the other end of the chamber so that the system remains at atmospheric pressure.   Assume that the chamber is well-mixed.

1. Predict and explain the shape of the graph for percent of O₂ in the mixing chamber versus time over a 2-min interval for normal breathing. Repeat for percent of CO₂ in the mixing chamber versus time.

Keep in mind the following points as you sketch the plot:

1. What is the volume of each exhaled breath as compared to the volume of air in the mixing chamber?
2. What is a regular breathing rate?
3. Has there been a gas concentration “plateau” by 2 min? In other words, will the concentration of gases in the mixing chamber be the same as the concentration of gases leaving your mouth by 2 min?
4. The x- (time) axis and y- (concentration) axis should be the correct magnitude.

Answer 1

Calculate the volume of oxygen in 5L chamber after every exhale as shown in table below.. each exhale will have 16% oxygen concentration or a depletion by 5% from 21% of the air already in chamber. Similarly for CO2, the exhale percentage will increse to 4% from the original 0.04%

Oxygen% Volume in 5L CO2% Vol of CO2 in 5 Breath(Se ehaled ai chamber ehaed air 5l chamber 0.0020 0.0021 0.0022 0.0022 0.0023 0.0024 0.0025 0.0026 0.0027 0.0028 0.0030 0.0031 0.0032 0.0033 0.0035 0.0036 0.0037 0.0039 0.0041 0.0042 0.0044 0.0046 0.0047 0.0049 0.0051 1.00 0.95 0.90 0.86 0.81 16% 16% 16% 16% 16% 16% 16% 16% 16% 16% 16% 16% 16% 16% 16% 16% 0.73 0.66 0.63 0.54 0.42 16% 16% 16% 16% 16% 16% 100 105 110 0.36 1 2 120 0.31

The graphs for O2 and CO2 are as attached below

1.2 1.1 0.9 Σ 0.8 0.6 0.5 0.4 0.3 0.2 0.1 TIME (SEC)

Vol of CO2 in 5l chamber 0.0060 0.0050 0.0040 0 W 0.0030 0.0020 0.0010 0.0000 TIME(SEC)