Introduction to the special issue: The state of acid-base physiology in a changing world

The human body maintains a narrow pH range regulated through acid-base balance. This balance is crucial as changes in the hydrogen ion concentration can disrupt cell membrane stability, alter protein structures, and change enzyme activities. The normal pH of arterial blood is 7.4, venous blood and interstitial fluid is 7.35, and intracellular fluid averages 7.0.
When the pH of arterial blood rises above 7.45, it results in a condition called alkalosis. Conversely, a drop below 7.35 leads to...

The human body maintains a precise pH range of arterial blood between 7.35 and 7.45. Deviations result in either acidosis (pH < 7.35) or alkalosis (pH > 7.45). These conditions are further classified as respiratory or metabolic disorders based on their underlying cause.
Respiratory Acidosis and Alkalosis
Respiratory acidosis occurs due to an increase in the partial pressure of carbon dioxide PCO2 in the blood. It often arises from shallow breathing or impaired gas exchange caused by...

The acid-base reaction class has been studied for quite some time. In 1680, Robert Boyle reported traits of acid solutions that included their ability to dissolve many substances, to change the colors of certain natural dyes, and to lose these traits after coming in contact with alkali (base) solutions. In the eighteenth century, it was recognized that acids have a sour taste, react with limestone to liberate a gaseous substance (now known to be CO2), and interact with alkalis to form neutral...

Acid-base homeostasis is essential for maintaining normal physiological activities in humans. The pH of various body fluids is strictly regulated because it is critical for the optimal activity of enzymes involved in metabolic reactions. Enzymes are basically proteins, so, any significant change in pH can affect their structure and activity. In humans, pH is regulated using three primary mechanisms— chemical buffer systems, respiratory regulation, and renal regulation.
Respiratory...

Diagnosing acid-base imbalances involves systematically analyzing arterial blood samples, focusing on three key measurements: pH, bicarbonate (HCO3−) concentration, and carbon dioxide partial pressure (PCO2). This analysis follows a four-step process that helps identify the imbalance's underlying cause and nature.
First, the pH level is assessed to determine whether the blood pH is normal (7.35–7.45), low (acidosis), or high (alkalosis).
Next, the PCO2  and...

For an ideal solution, the pH is defined as the negative logarithm of the hydrogen ion concentration. For a non-ideal solution, an accurate measurement of the pH must consider the negative logarithm of the hydrogen ion activity rather than concentration. In such a solution, the pH can be more accurately defined as the negative logarithm of a product of the hydrogen ion concentration and its activity coefficient.
In solutions of very low ionic strength—for example, pure water—the...