acid base

• The body maintains acid-base balance within a narrow pH range to ensure proper biological processes.
• Small pH changes can significantly alter biological processes.
• The first line of defense against pH changes is through buffers that neutralize excess hydrogen ions (H+).
• The respiratory system responds by controlling carbon dioxide (CO2) levels, and the renal system controls bicarbonate (HCO3-) to neutralize it.
• Many diseases can disrupt this balance, leading to imbalances that can cause further health problems.
• pH expresses hydrogen ion concentration; decreased pH means increased acidity, while increased pH indicates alkalinity.

Plasma pH

• Plasma pH is normally between 7.35 and 7.45.
• Solutions exceeding a pH of 7.0 are alkaline or basic, and those below 7.0 are acidic.
• Acidosis occurs when blood pH drops below 7.35, while alkalosis happens when it rises above 7.45.
• The formation of carbonic acid (H2CO3) from CO2 in tissues influences blood pH.
• Renal and respiratory compensations can move pH closer to normal but may not resolve underlying issues.

Carbon Dioxide Transport

• Most carbon dioxide diffuses into red blood cells.
• Some carbon dioxide remains dissolved in plasma.
• Roughly a quarter binds to hemoglobin.
• Most is converted to carbonic acid by carbonic anhydrase.
• Hydrogen ions are buffered by molecules like hemoglobin.
• Bicarbonate moves out of RBCs in exchange for chloride ions.
• Buffers, such as plasma proteins, hemoglobin, and amino acids, maintain blood pH within the 7.35-7.45 range by absorbing H+.

PCO2 and Blood pH

• As carbon dioxide levels increase, H+ and bicarbonate ions are released, decreasing pH.
• Converseley as carbon dioxide decreases, blood pH increases.

Chemoreceptors

• Central chemoreceptors in the medulla sense H+ levels, which reflect CO2 levels.
• Peripheral chemoreceptors in the carotid and aortic bodies detect oxygen and H+ levels.
• Both central and peripheral chemoreceptors play an important role in ventilation

Blood pH and Temperature on Hb Saturation

• With decreased blood pH, more oxygen is released, shifting the oxygen-hemoglobin saturation curve to the right.
• When temperature increases, more oxygen is release, shifting the oxygen-hemoglobin saturation curve to the right.

The Cause of Respiratory Acidosis

• Hypoventilation is the primary cause of respiratory acidosis.
• Arterial carbon dioxide rises, leading to respiratory acidosis.
• Common causes include controller failure to respond to carbon dioxide, anesthesia, asthma/COPD, and infections.

The Relationship of Pco₂ and Buffer

• If carbon dioxide production is not matched by the respiratory system, this leads to fluctuations in H+ and pH.
• Chemical buffer systems minimize fluctuations in pH by adjusting H+.

Transport in the PCT

• The proximal convoluted tubule plays a role in the transport of acids to maintain homeostasis.

Compensations

• An example of this is acidosis. In an acidic state the body goes through compensations.
• The kidneys secrete H+, and blood buffer and bicarbonate reserve also play a role to balance out the pH.

Acid-Base Disorders

• Respiratory acidosis arises from an increased pressure of carbon dioxide, involving conditions that impair gas exchange.
• Respiratory alkalosis is caused by decreased pressure of carbon dioxide, often due to hyperventilation.
• Renal system corrects these imbalances through hydrogen and bicarbonate ion excretion or reabsorption.
• Metabolic acidosis is linked to fall in bicarbonate, caused by lactic acidosis, ketoacidosis, or bicarbonate loss.
• Metabolic alkalosis is associated with elevation in bicarbonate, caused by excessive vomiting or high intake of bicarbonate.
• The respiratory system compensates by hyperventilation to reduce carbon dioxide levels.
• Normal alveolar capillary gas exchange occurs rapidly via diffusion.

Clinical Assesment

• Assess pH
• Check PCO2
• Check HOC3