Cardiopulmonary Function

Cardiopulmonary function is the interrelationship between the workings of the heart and lung organs. The most important function of the cardiopulmonary system is with respect to the flow and regulation of blood between the heart and the lungs, a process that centers upon the connection between the heart and the lungs made through the pulmonary artery.

The function of the cardiopulmonary system is best understood when contrasted with the two interrelated, cardio-centered systems. The cardiovascular system is the method by which the heart and the entire network of blood vessels function together to direct the flow of blood through out the body. The cardiorespiratory system is a specialized component of the larger cardiovascular works. The cardiorespiratory system describes the function of the heart in relation to the body's entire breathing mechanism, from the nose and throat to the lungs. These three systems function interdependently.

The bodily blood volume of the average healthy person is approximately 5.8-6.8 qt (5.5-6.5 l). The heart, in conjunction with the action of the blood vessels, powers blood through 60,000 mi (100,000 km) of the typical circulatory system, with between 5,280 and 6,340 qt (5,000-6,000 l) passing through the hearts chambers each day. Consequently, the efficiency of heart function will depend directly on the strength of the heart muscle. Aerobic exercise makes the heart stronger and better equipped to propel blood. The power of the heart and the clear, unobstructed pulmonary artery passages performing in concert permit the efficient movement of blood to and from the lungs, where useful oxygen and waste carbon dioxide are exchanged in the microscopic lung compartments known as the alveoli.

The most dangerous circumstance involving the cardiopulmonary system is a stoppage of the heart, known as sudden cardiac arrest, which prevents blood flow to the heart. Sudden cardiac arrest will generally lead to death if left unresolved for more than a few moments. Sudden cardiac arrest occurs approximately 1,000 times per day in the United States, and as frequently on a per capita basis through out the Western world. In many instances, especially for cases where the victim is over 35 years of age, the most common cause of sudden cardiac arrest is a form of coronary disease, a buildup of arterial plaque narrowing arteries and impeding blood flow to the heart.

Where the victim is under age 35, and an athlete, sudden cardiac arrest has generally one of two causes. In up to 80% of such occurrences, the athlete has a congenital heart defect (an abnormality that has been present since birth), undetected through prior physical examination. It has been estimated that between 200 and 300 athletes in the United States under the age of 25 die from sudden cardiac arrest that has a congenital cause every year. The most common of these defects is a thickening of the wall of the left side of the heart (the chamber that does most of the propulsion of blood out of the organ).

The other common cause of sudden cardiac arrest among younger athletes is heart arrhythmia, a condition in which the electrical system of the heart, which regulates heart beat, causes the heart muscle to quiver and then cease function. Sudden cardiac arrest rarely presents any symptom in advance of onset. The most common form of this condition is known as ventricular fibrillation.

Heart arrhythmia has a number of underlying conditions, including a larger-than-normal heart, a defect or blockage in a coronary artery, an inflammation of the heart muscle, or external influences such as the ingestion of a stimulant like cocaine, or a direct blow to the chest that causes heart trauma. For an athlete, while exercise is a proven cardioprotector, if one of these conditions is present the mechanisms of heart growth through exercise, coupled with increased exercise intensity, may in some circumstances lead to a sudden cardiac arrest. Such occurrences are rare when assessed in raw numbers of deaths per year, but the deaths of prominent athletes in the apparent peak of health and fitness never fail to resonate with the public. Major league baseball pitcher Steve Bechler, Cameroon soccer player Marc Vivien Foe, and basketball players Reggie Lewis and Hank Gathers are prominent athletic examples of death due to heart arrhythmia.

In an ideal circumstance, particularly prior to engaging in a high intensity training program, an athlete should have a complete physical, including the review of the athlete's personal risk factors such as a family history of heart disorder, or certain types of drug use, particularly stimulant use. This physical would also include an electrocardiogram, or ECG, a device that aids in the assessment of the regularity of heart function.

The most well known understanding of cardio-pulmonary function is cardiopulmonary resuscitation (CPR). CPR is an emergency procedure used to stimulate heart and lung function when the heart stops suddenly (cardiac arrest) and when a combination of external cardiac massage (rubbing the chest forcefully) and artificial respiration is used to revive the afflicted person. If successful (CPR is more likely to be successful if administered within the first four minutes of cardiac arrest), the flow of oxygen in and out of the lungs, with corresponding flow along the pulmonary artery to the heart muscle, will be achieved. Once CPR has been administered, a defibrillator will often be used to spur a resumption of a regular heart beat.

During a cardiac arrest, the organ at risk of permanent damage in the cardiopulmonary system is the heart, not the lungs. The lungs can survive an absence of respiration; the heart cannot survive an absence of oxygen-rich blood without a risk of the cells of the heart dying. Due to the nature of the construction of these cells, they cannot be regenerated in the same fashion as most other organs.

SEE ALSO Cardioprotection; Cardiorespiratory function; Cardiovascular system; Oxygen; Stimulants.