Generally, the lungs work quickly to regulate the PaCO2 levels and cause a quick change in the pH. As the respiratory rate decreases or becomes more shallow, less CO2 is removed causing increased acid (H+) levels in the blood and decreased pH (so the blood becomes more acidic). CO2 forms an acid in the blood that is regulated by the lungs by changing the rate or depth of respirations.Īs the respiratory rate increases or becomes deeper, additional CO2 is removed causing decreased acid (H+) levels in the blood and increased pH (so the blood becomes more alkaline). PaCO2 is the partial pressure of arterial carbon dioxide in the blood. The kidneys excrete bicarbonate (base) in the urine and retain hydrogen ions (acid). Conversely, when the pH is too high (i.e., during alkalosis), the respiratory rate decreases to retain acid in the form of CO2. The kidneys excrete additional hydrogen ions (acid) in the urine and retain bicarbonate (base). For example, when the pH is too low (i.e., during acidosis), the respiratory rate quickly increases to eliminate acid in the form of carbon dioxide (CO2). The lungs are essential for maintaining pH and the kidneys also play a role. The body has several mechanisms for maintaining blood pH. These by-products create extra hydrogen ions (H+) in the blood that need to be balanced and kept within normal range as described earlier. Hydrogen ions are by-products of the metabolism of substances such as proteins, fats, and carbohydrates. A high pH, greater than 7.45, occurs in alkalosis when the blood has a low hydrogen ion concentration. A low pH, less than 3.5, occurs in acidosis when the blood has a high hydrogen ion concentration. The pH of blood is a measure of hydrogen ion concentration. A blood pH of less than 7.35 is considered acidic, and a blood pH of more than 7.45 is considered alkaline. Normally, the blood has a pH between 7.35 and 7.45. A neutral pH is 7, which is the same pH as water. PH is a scale from 0-14 used to determine the acidity or alkalinity of a substance. If arterial blood flow is adequate, warmth and color should return to the hand. Pressure is released from the ulnar artery to check if blood flow is adequate. When performing the Allen test, pressure is held on both the radial and ulnar artery below the wrist. This is done by performing the Allen test. Prior to collecting blood gases, it is important to ensure the patient has appropriate arterial blood flow to the hand.