Approximately 50 to 60 percent of a human’s body weight is from water. The percentage varies based on several factors. For instance, fat holds very little water while muscle is about 75 to 77 percent water. The obese couch potato may contain 50 percent or less in water weight. On the other hand, a fit muscular person may have 60 to 65 percent of water in body weight.

The water in the body can be compared to swimming pool water. Swimming pools are strictly monitored to keep the water at a certain pH balance. The water should not be too acidic nor too alkalitic. The fluid in the human body must stay within normal ranges also. Th normal pH balance in the human body is 7.35 to 7.45, (which is basically neutral). If the pH gets low (acidosis) or high (alkalosis) there will be specific problems that could be life threatening.

The water in the human body is further broken down into specific categories. Intracellular fluid (ICF) is water actually contained inside cells. Extracellular fluid (ECF) is water outside the cells. Combined, ICF and ECF equal 60 percent on average of the total body weight. Extracellular fluid is further broken down into interstitial fluid, plasma, bone, connective tissue, and transcellular fluid. Interstitial fluid, primarily located in the lymphatic system, equals about 12 percent of body weight. Plasma, basically the liquid portion of the blood, equals about 4.5 percent of body weight. Connective tissue accounts for about 4.5 percent, with the smallest amount of 1.5 percent being composed of transcellular fluid.

The body has several different ways to ensure that the pH balance stays in the normal range of 7.35 to 7.45. These are referred to as buffer systems. Through normal day to day activity in the body, acids are formed as waste products that need to be neutralized or eliminated. Some of the acids are released with CO2 from exhaling; others are excreted via the kidneys. These systems work together in the healthy human body to keep the pH level within normal ranges.

If for some reason the buffering systems fail or are hindered, the pH balance will be upset. Either too much or too little of the acids will be neutralized. The causes of this can be as simple as the flu or as complications from trauma, disease or serious illness. Once the body senses the pH is out of kilter, it will attempt to compensate to correct the problem. The conditions for when this happens are known as acidosis or alkalosis. These are further broken down into either metabolic or respiratory in nature. This includes metabolic acidosis, respiratory acidosis, metabolic alkalosis, and respiratory alkalosis.

One of the chief buffers in the blood is bicarbonate, which helps neutralize acids. This is like taking an antacid for heartburn. Metabolic acidosis is caused by the loss of bicarbonates or an increased production of acids. Some causes for bicarbonate loss can be severe diarrhea, drug intoxication or abuse, or severe illness. Some causes for increased acid production include serious illness or injuries, and decreased blood flow. An example of this is when you leg "falls asleep". Blood flow is decreased allowing acid to build up. Upon standing, blood flow is restored. The tingly pin and needle sensation is caused from the excess acid in the tissues. The acid is then neutralized resulting in the pin and needle sensation subsiding.

Respiratory acidosis is usually caused by insufficient respirations or air exchange. This can be caused by head or chest trauma and respiratory diseases such as emphysema. In cases of emphysema, the lungs cannot perform normally due to an increase of dead air space. Acidosis develops slowly over a period of time. These are usually treated with bronchodilators and small amounts of oxygen to increase air exchange in the lungs. With a severe decrease in breathing caused by trauma or respiratory arrest, the amount of acid quickly increases. Adequate measures need to be taken to treat the cause.

Metabolic alkalosis occurs when too much acid is excreted from the body. This can be caused by eliminating too much fluid by frequent urination, by excessive vomiting, or various diseases. If the body becomes too alkalitic, the nervous system and the heart can be affected. The heart may speed up and become irritable while breathing slows in order to compensate. By slowing respirations, less acid is "blown off" from the lungs. This is in contrast to hyperventilation often seen in metabolic acidosis. Metabolic alkalosis is treated based on findings from laboratory tests.

Respiratory alkalosis is caused when the body is stressed. Some of the causes include shock, sepsis, trauma and asthma. Too much acid is "blown off" from increased respirations or hyperventilation. In cases of hyperventilation of psychogenic origin, the increase in alkalosis causes the tingly sensation around the mouth and in the fingertips. Because of hyperventilation, blood is slowed to the brain so the respiratory center tells the body to increase respirations. In psychogenic hyperventilation, the symptoms of tingling and feeling of smothering continue to worsen. Treatment of respiratory alkalosis is basically to treat the cause. This can include the simple paper bag method for psychogenic hyperventilation, to using sedation to slow respiration. By slowing the breathing, the blood flow is returned to the brain. This allows the respiratory center to regulate itself and get the levels back to normal. Interesting, in psychogenic hyperventilation, if the person continues to hyperventilate, they often pass out. Respirations slow and return to normal, in turn the body gets back to normal.