Blood flow velocity is a measurement of the rate at which blood moves through a particular vessel. A number of factors can influence the rate of blood flow, making this measurement an important part of clinical diagnosis in some circumstances, as changes in velocity can indicate the presence of particular medical issues. Using imaging equipment such as an ultrasound, it is possible to actually see the blood flow velocity in a specific area of concern.
The circulatory system is a pressurized system. Every time the heart beats, it pushes blood out into the body, and the blood is forced through a series of valves to reach the extremities before returning to the heart. The body uses a variety of techniques to keep blood moving, ranging from harnessing gravity to contracting muscles to squeeze the blood through.
If a patient has a low blood velocity, it can mean that he or she will suffer loss of blood flow in some areas of the body, as the blood will be moving too slowly to get where it needs to go. The decreased rate of flow can also lead to deoxygenation, as less blood will be reaching certain areas, and therefore those areas will be starved of oxygen. Stroke patients often experience a radical decline in blood flow, which leads to cell death in the brain as cells are deprived of the oxygen they need.
Blood flow velocity can also be too high, causing other types of health problems. Vessels could burst or become severely compromised, for example, just like a balloon pops when someone tries to force too much air in too quickly. In either case, it is necessary to determine the cause of the problem, and to address it so that the patient will become hemodynamically stable.
One of the obvious factors which influences blood flow rate is heart health and blood pressure. Stable blood pressure and a healthy heart will maintain a consistent level of blood flow, at a steady rate. Changes in the health of the heart or the blood pressure can lead to changes in blood flow rate. The total surface area of the vessel the blood is moving through is also a factor: the larger the surface area, the slower the blood will move. Resistance to blood flow, such as that caused by a closed valve, is something else that can influence the rate at which blood flows through the body.