"Airflow
through the nasal passages is normally asymmetrical because of alternating
changes in nasal resistance in each nostril. The mechanism involves changes in sympathetic tone to the venous erectile tissue of the nasal mucosa; increased
sympathetic vasoconstriction causing resistance to fall. The total nasal
resistance to airflow remains fairly constant as changes between the nasal
passages tend to be reciprocal so that the patient is usually unaware of the
phenomenon.....The reason for its existence is uncertain. A simple explanation
is that it permits one side of the nose to go through a rest period and recover
from the minor trauma of conditioning the inspired air."
For this
exercise you'll need to carry around with you a small, clean mirror. You're
going to hold the mirror underneath your two nostrils, so that it's just touching
your upper lip. Leave it there as you normally inhale and exhale a few times --
don't change your pattern of breathing (see the figure on the left below). This
will produce two "clouds" of condensation on the mirror, one
associated with each nostril (see the figure on the right below). Judge which
"cloud" is larger, left or right, and record that judgment along with
the time of day you made it. Sometimes the judgment will be very easy (the
differences will be obvious), but other times the differences may be subtle.
Also, because the "borders" of the condensation cloud taper off
gradually, you're going to have to adopt some criterion for what constitutes
"the edges" of each cloud and you'll need to apply that criterion
each and every time you make judgments.
Repeat this
exercise every 20 minutes during a 12-hour period, so that you'll accumulate a
total of 36 pairs of measurements. If it is impossible to make judgments at the
appropriate time then do so as soon as possible after that and make a note when
that judgment was made. After you've collected your data, plot the results in
the form of a graph: time will be plotted along the horizontal axis and
"larger nostril" will be plotted along the vertical axis (see example
graph below). If you're like 80% of people, the graph will fluctuate over time
(meaning that when one patch of condensation is small the other will be large,
and vice versa). From this graph you should be able to extract your nasal
cycle: this is the duration of time it takes for you to go through one complete
cycle of diameter change.
