The Valsalva maneuver is a simple technique that involves breathing out of the nose and mouth while they are closed. This raises the pressure inside the chest and middle ear, and can equalize pressure in the ears and help reduce some heart arrhythmias. Although rare, ear damage can sometimes occur when blowing too hard with the Valsalva maneuver. Ear “popping” sensations are usually felt at the start of the Valsalva maneuver, but to also get the cardiac benefits, the maneuver must continue for 10-15 seconds. The modified Valsalva maneuver involves laying flat with the legs elevated for 15 seconds after exhaling against closed airways for 15 seconds. This modification improves the heart rate in patients with certain types of arrhythmias, and it can be done anytime, anywhere — nothing is needed to perform the Valsalva maneuver. SVT, or supraventricular tachycardia, is a type of fast heart beat that can sometimes be serious and requires medical treatment.
Variance is a measure of statistical dispersion about the mean. The larger the variance, the further individual values of the random variable (observations) tend to be from the mean, or average. Variance exists between individuals of a species for a multitude of traits, including dentition. A number of different genetic, environmental, and mechanical factors may be at the root of this variance. Even in cases of monozygotic twins, dental variation is seen in their individual dentition. This may be due to epigenetic factors, environmental variances, and different phylogenetic influences. Variance in dentistry can also be found in the measurements taken by different tools. Each tool used is calibrated per industry standards but subtle differences in each individual tool will result in minor, or sometimes major, variances. Careful calibration prior to use, proper tool cleaning and maintenance, and proper tool storage and care will help diminish the likelihood of extreme variance between tools.
Vascular endothelial growth factor (VEGF), also called vascular permeability factor (VPF), is a specific type of protein known as a signal protein that encourages the body’s creation of blood vessels. When cells release this protein, it “signals” the body to take action — in the case of VEGF, either by angiogenesis or vasculogenesis. Angiogenesis is the creation of new blood vessels from existing vasculature, while vasculogenesis is the creation of the circulatory system in the embryo. The vascular endothelial growth factor protein is critical to human survival as it’s the protein that restores the supply of oxygen to tissues that have become hypoxic, or suffered a loss of oxygen. Most often, this occurs after cells become injured or to repair muscle after exercise. However, VEGF expression can also result in the formation of new blood vessels to circumvent ones that are blocked, a process called collateral circulation. Overexpression of VEGF can lead to disease.
All parts of the body require oxygen to function, which is carried to the cells via blood vessels or the vascular supply. The heart and lungs require a great deal of oxygen, while other parts of the body, like bone, require less. However, bone can also cease to function without an adequate supply of oxygen. In an average long bone, oxygenated blood is supplied by either periosteal vessels, epiphyseal vessels, or a nutrient artery. By having three systems in place, one can take over the function of the other if it becomes blocked or damaged in some way. If bone tissue does not receive enough oxygen, a process known as avascular necrosis or osteonecrosis occurs. This is the death or decay of the bone due to a lack of oxygenated blood. Osteonecrosis can cause the bone to become brittle, breaking into small pieces and eventually crumbling or collapsing if left untreated.