Human Spirometry
HS-4-1
Experiment HS-4: Lung Volumes
and Heart Rate
Background
Breathing is a function that can be performed both
voluntarily and involuntarily. When exercising and recov-
ering from exercise, the depth and rate of breathing are
adjusted by the autonomic nervous system. The portions
of the autonomic nervous system that control heart rate,
circulation, muscle tension, and many other bodily
functions are influenced by conscious breathing.
While breathing normally, heart rates usually increase
during inhalation and decrease during exhalation. This
cyclic change in heart rate, that is driven by breathing, is
known as
Respiratory Sinus Arrhythmia
(RSA).
The diaphragm, the large muscle between the thoracic
and abdominal cavities, is the primary motive force for
pulmonary ventilation. During inhalation, the diaphragm
contracts and moves downward creating negative
pressure in the thoracic cavity. This negative pressure
pulls more blood into the major veins in the chest, which
improves venous return to the heart and increases the
amount of blood entering the right side of the heart. If
more blood is entering the heart, more blood needs to be
pumped out of the heart. The solution for moving more
blood is an increase in the heart rate. The increase in
heart rate is controlled through the integration of infor-
mation from the organ systems involved in the cardio-
vascular system. Conversely, as the diaphragm relaxes
during exhalation, the pressure in the thoracic cavity
becomes less negative, venous return decreases, less
blood enters the heart, and the heart rate can decrease.
Studies have shown that respiratory sinus arrhythmia
(RSA) is more prominent in younger than older adults.
RSA prominence, measured by the difference between
the minimum and maximum heart rates in a breathing
cycle, decreases by 10% per decade between ages 20
and 70. RSA prominence is also related to aerobic
conditioning. It has been observed that well-trained
athletes have higher RSA prominence than is normally
expected for their age group. It has been suggested that
RSA prominence would be a good measure of aerobic
fitness
In this experiment, you will determine the heart rate
and RSA prominence of a subject breathing at rest. You
will also determine the effect of apnea, different
inhalation volumes, and the movement of the muscles
involved in breathing on heart rate. To make valid
comparisons from exercise to exercise, the exercises in
this lab need to be performed by the same subject.
Equipment Required
PC Computer
IWX/214 data acquisition unit
USB cable
IWX/214 power supply
PT-104 Pulse transducer
SP-304 Spirometer
FH-300 Spirometer flow head and plastic tubes
IWX/214 Setup
1
Place the IWX/214 on the bench, close to the computer.
2
Check Figure T-1-1 in Chapter 1 for the location of the USB
port and the power socket on the IWX/214.
