The circulatory system consists of the cardiovascular and lymphatic systems. The cardiovascular system is made up of the heart, blood, and blood vessels. The lymphatic system consists of lymph, lymph nodes, lymph vessels, the tonsils, the spleen, and the thymus gland. The circulatory system is responsible for transporting oxygen, water, and nutrients (such as sugar and vitamins) throughout the body. It also carries away wastes (such as carbon dioxide) produced by body cells to the lungs, kidneys, or skin for removal from the body.
The heart is divided into four chambers. The two upper chambers are the right and left atria. The atria receive blood from the body and lungs. The right atrium receives blood that is low in oxygen from the body. The left atrium receives blood rich in oxygen from the lungs. The two lower chambers of the heart are the right and left ventricles. The ventricles are larger and have thicker walls than the atria because their function is to pump blood to the lungs and body. The right ventricle pumps blood to the lungs. The left ventricle pumps blood to the body.
The liquid portion of the blood is called plasma. Plasma carries blood cells throughout the body. The formed elements of the blood are the red blood cells, white blood cells, and platelets. Red blood cells pick up oxygen in the lungs and transport it to body cells. The red blood cells then gather up carbon dioxide and transport it to the lungs, where it is removed from the body when we exhale. White blood cells attack and destroy germs that enter the body. Platelets are irregularly shaped blood cells that have a sticky surface. When a blood vessel is damaged and starts to bleed, platelets gather at the site of the injury. They begin to stick to the opening of the damaged vessel and seal the vessel, stopping the flow of blood.
Blood vessels that carry blood away from the heart to the rest of the body are called arteries. Arteries have thick walls because they transport blood under high pressure. Vessels that return blood to the heart are called veins. The walls of veins are much thinner than the walls of arteries. Because the pressure in veins is low, veins contain one-way valves that help keep the blood flowing toward the heart. Capillaries are the smallest and most numerous of the blood vessels. They are very thin and connect arteries and veins. They move oxygen, nutrients, and waste products between blood and body cells through their walls.
When the heart stops, the patient is said to be in cardiac arrest. The signs of cardiac arrest include sudden unresponsiveness, absent breathing, and no signs of circulation. Organ damage begins quickly after the heart stops. Sudden cardiac death is the unexpected loss of life occurring either immediately or within 1 hour of the onset of cardiac symptoms. Brain damage begins 4-6 minutes after the patient suffers a cardiac arrest. Brain damage becomes irreversible in 8-10 minutes.
Chest compressions are used to circulate blood when the heart is not beating. Chest compressions are combined with rescue breathing to oxygenate the blood. The combination of rescue breathing and external chest compressions is called cardiopulmonary resuscitation (CPR).
The Chain of Survival is the ideal series of events that should take place immediately after recognizing an injury or the onset of sudden illness. The chain consists of four steps:
Early access
Early CPR
Early defibrillation
Early advanced cardiac life support
When a cardiac arrest occurs, CPR must be started as early as possible. However, even with the best CPR, CPR provides only about one third of the normal blood flow to the heart and brain. By itself, CPR is not enough to help someone survive a cardiac arrest. CPR can keep oxygen-rich blood flowing to the heart and brain until the arrival of an automated external defibrillator (AED) and advanced care. An AED is a machine that analyzes the patient's heart rhythm for any abnormalities. It administers an electric shock through the patient's chest to the heart.
The steps of CPR include
Checking the patient's level of responsiveness
Use the AVPU scale to quickly check the patient's level of responsiveness (mental status). For chest compressions to be effective, the patient must be positioned on a firm, level surface. If you find the patient in bed, move him or her to the floor. Place the patient's arms at his or her sides. Once the patient is lying face up, position yourself at the patient's side, so that you can provide rescue breathing and chest compressions if necessary.
A = Airway
If the patient is unresponsive and you do not suspect trauma, open the airway using the head tilt-chin lift maneuver. If you suspect trauma, open the airway using the jaw thrust without head tilt.
B = Breathing
After you have made sure that the patient's airway is open, assess his or her breathing. Look for the rise and fall of the chest. Listen and feel for air movement from the patient's nose or mouth. If the patient is not breathing, begin rescue breathing using a pocket mask or a mouth-to-barrier device.
C = Circulation
Use the carotid artery to check the pulse of an unresponsive adult or child older than 1 year of age. Feel for a brachial pulse in an unresponsive infant. Feel for a pulse for about 10 seconds and look for other signs of circulation, such as coughing or movement in response to your rescue breaths. If there is no pulse or signs of circulation, you must begin chest compressions.
