Saddleback Journal of Biology - Saddleback College

Fall 2009 Biology 3B Paper
The measurements of the TV (volume of air
exhaled when taking a normal and unforced breath),
ERV (volume of the additional air that can be forced
out after a normal TV), and VC (maximum volume of
air completely exhaled after taking in a complete and
deep breath) were measured by having each subject
exhale into a disposable cardboard mouthpiece
attached to the bell spirometer. To deflect possible
measurement errors, all subjects were asked to firmly
place their lips around the cardboard mouthpiece to
minimize the amount of air escaped through gaps
between the subjects’ mouths and the cardboard
mouthpieces. If a subject’s TV was measured as being
greater than or equal to 1.0 L or the subject appeared to
have been forcing his breath, the measurement was
retaken. Using Microsoft Excel, a one-tailed t-test
assuming unequal variances was performed on the
collected data to compare the average VC, TV, ERV,
and IRV of each group.
Results
After running the collected data from both
groups through Microsoft Excel, the t-test revealed that
there is no significant difference between the average
VCs of the smoking and nonsmoking groups
(p=0.091). The nonsmoking group was observed to
have an average VC of 4.46L ±0.22 (±SE, N=10) and
the smoking group was observed to have an average
VC of 4.07L ±0.18 (±SE, N=10) (Figure 1).
Mean Vital Capacity (L)
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
Smoking Males
Nonsmoking Males
Figure 1. Compared mean vital capacity values of
nonsmoking and smoking males. There was no
significant difference between the two groups. Error
bars represent ±SE.
The average TV for nonsmoking males was
0.50 L + 0.04 (+SE, N=10). The average TV for
smoking males was 0.53 L + 0.07 (+ SE, N=10) A onetailed
t-test revealed that the average TV for
nonsmoking males was not significantly higher than
the average TV for smoking males (p=0.380). The
average ERV for nonsmoking males was 2.44 L + 0.22
(+SE, N=10). The average ERV for smoking males
was 2.24 L + 0.21 (+ SE, N=10) A one-tailed t-test
revealed that the average ERV for nonsmoking males
was not significantly higher than the average ERV for
smoking males (p=0.261). The average IRV for
nonsmoking males was 1.52 L + 0.22 (+SE, N=10).
The average IRV for smoking males was 1.31 L + 0.18
(+ SE, N=10) A one-tailed t-test revealed that the
average IRV for nonsmoking males was not
significantly higher than the average IRV for smoking
males (p=0.233).
Discussion
The results show that although there is a
difference between the VC of nonsmoking and
smoking males, the difference did not reach the level of
significance. No significant differences were also
found when comparing the average TV, ERV, and IRV
between the smoking and nonsmoking groups. There
were some factors that could have been considered
during this experiment. Because of the equipment used,
the collected data depended upon each subject fully
understanding the action they were being asked to
perform. If a subject misinterpreted the type of
exhalation desired, then the results may have been
negatively affected. Also, increased selectivity of
subjects in this experiment would have been beneficial.
Because there was an observed correlation between the
size of the subjects and the volume of the VC, the
results may have reflected the relationship of the
variance of height and weight and the VC. The small
sample size in each group may have also reflected the
results. Given the time period in which this experiment
was performed, strict selectivity may be an unrealistic
accomplishment. If a future study should be
constructed, some improvements will be made
including: a larger sample size to better represent the
population, observance of subjects over a longer period
of time to document hypothesized values as smoking
use continues, tests to validate the health of the
subjects, a computerized spirometer to reduce
measurement errors, and add a test to view the
diffusion rates of carbon monoxide (CO) into and out
of the blood.
Although the results did not show a significant
difference in lung capacity, this does not suggest that
smoking males have the equivalent lung function as
nonsmoking males. It simply shows that smoking
males have the capability to uptake the same volume of
air as nonsmoking males. Studies show that the
diffusion rate of gases through the lungs and into the
blood stream decreases when tobacco smoke is inhaled
(Fidan et al., 2004, Janson et al., 200l, Prediletto et al.,
2007, Rizzi et al., 2004, Taylor et al., 2002, and Tzani
et al., 2008). Research from Tzani et al., (2008) shows
that there is a significant difference in the diffusion rate
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Saddleback Journal of Biology
Spring 2010