Human SpirometryHS-4-1Experiment HS-4: Lung Volumes and Heart RateBackgroundBreathing 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 fitnessIn 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 RequiredPC ComputerIWX/214 data acquisition unitUSB cableIWX/214 power supplyPT-104 Pulse transducerSP-304 SpirometerFH-300 Spirometer flow head and plastic tubesIWX/214 Setup1Place the IWX/214 on the bench, close to the computer.2Check Figure T-1-1 in Chapter 1 for the location of the USB port and the power socket on the IWX/214.