When we try to hold our breath for a long time the urge to take a deep breath begins very slowly, but as we continue to hold our breath the urge to take a breath gradually gets stronger and stronger.

Eventually we reach a point beyond which we can no longer resist the urge and we gasp for a lung full of fresh air.

The length of time that we can hold our breath depends upon the amount of carbon dioxide that is dissolved in our blood stream. The rate at which our metabolism is adding carbon dioxide to our blood depends upon the intensity of our physical activity.

To demonstrate this try the following simple experiment.

Things you'll need

(A) Experiment

Sitting

Sit very quietly for at least three minutes. Use a stop watch to time this accurately.

Then take one deep breath and hold it for only 15 seconds. (Not more than 15 seconds!)

How strong is the urge to take a breath after 15 seconds has elapsed?

Rate your ability to hold your breath after 15 seconds using the following six point scale:

1.very-easy
2.easy
3.somewhat-easy
4.slightly-difficult
5.difficult
6.very-difficult

Standing

Stand up for at least three minutes. Use a stop watch to time this accurately.

Then take one deep breath and hold it for only 15 seconds.

How strong is the urge to take a breath after 15 seconds has elapsed?

Rate your ability to hold your breath after 15 seconds using the following six point scale:

1.very-easy
2.easy
3.somewhat-easy
4.slightly-difficult
5.difficult
6.very-difficult

Jumping Jacks

Perform some vigorous activity ... jumping jacks, running on the spot, skipping etc. for at least three minutes. Use a stop watch to time this accurately.

Then take one deep breath and hold it for only 15 seconds.

How strong is the urge to take a breath after 15 seconds has elapsed?

Rate your ability to hold your breath after 15 seconds using the following six point scale:

1.very-easy
2.easy
3.somewhat-easy
4.slightly-difficult
5.difficult
6.very-difficult

Rest for 1-2 minutes between each of these activities

  • Ask the students to describe their experience.
  • Was is it easy, moderate or hard to perform the activity?
  • How was their drive to breath? (no drive, moderate or really strong)
  • Print out a copy of each of the charts (below) and summarize the class results for each activity.


Copy master
Copy master
Copy master

(B) Repeat

Repeat the same experiment as above but this time hyperventilate immediately before breath holding. To hyperventilate take three (3) large deep breaths and exhale fully. On the fourth breath, inhale and hold your breath for 15 seconds.

CAUTION

Excess hyperventilation can be extremely dangerous! DO NOT take more than three (3) deep breaths to hyperventilate!

Notes:

The drive to breathe is generally lower after hyperventilation because more CO2 has been removed from the circulatory system (blood stream). This increases the time it takes for the carbon dioxide in your blood stream to reach a level whereby you feel the strong urge to take a breath.

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Polar Science 2006
McMaster University YES I Can! Science Team
www.polar06.yesican-projects.ca