Acid-Base Balance: Role of the Lungs PDF

ACID-BASE BALANCE: ROLE of the LUNGS Dr. Alper YILDIRIM [email protected]  Acid-base balance refers to - “the regulation of free hydrogen-ion (H+) concentration in the body fluids” Derangements of hydrogen and bicarbonate...

ACID-BASE BALANCE: ROLE of the LUNGS Dr. Alper YILDIRIM [email protected]  Acid-base balance refers to - “the regulation of free hydrogen-ion (H+) concentration in the body fluids” Derangements of hydrogen and bicarbonate concentrations in body fluids are common in disease processes.  Source of Acidity CO2 + H2O CA H2CO3 CA H+ + HCO3- Source of Acidity  Acid – Base disturbances Davenport Diagram Respiratory Acidosis and Alkalosis A Davenport diagram illustrating the transition from respiratory acidosis to respiratory alkalosis.  The regulation of H+ balance The major source of H+ CO2 + H2O CA H2CO3 CA H+ + HCO3-  The regulation of H+ balance The Henderson-Hasselbalch equation is used to calculate how changes in CO2 and HCO3− affect pH: HCO3- controlled by kidney function pH = CO2 controlled by lung function Three lines of defense against changes in [H+] operate to maintain the [H+] of the body fluids at a nearly constant level (pH 7.4) despite unregulated input: 1. Chemical buffer systems 2. Respiratory mechanism of pH control 3. Renal mechanism of pH control  Ventilation Can Compensate for pH Disturbances The major source of H+ CO2 + H2O CA H2CO3 CA H+ + HCO3- Hypoventilation Hyperventilation Change in extracellular fluid pH caused by increased or decreased rate of alveolar ventilation, expressed as times normal  Pulmonary Ventilation Increased H+ concentration stimulates respiration à increased alveolar ventilation decreases H+ concentration é [H+] é Alveolar ventilation which of the of the fallowing is right about respiration high concentrations of hydrogen trigger hyperventaltion - respiratory system is a negative feed back mechanism in hypoventelation we have increased co2 levels all ê PCO 2 The respiratory system acts as a typical negative feedback controller of H+ concentration.  Respiratory acid-base regulation Acts at a moderate speed Activated when the chemical buffer systems alone are unable to minimize Requires a few minutes to be initiated Respiratory system serves as the second line of defense- – if a deviation in [H+] is not swiftly and completely corrected by the buffer systems Respiratory compensation Peripheric Chemoreceptors  Central Chemoreceptors be careful that h does not penetrate the bbb.  Respiratory Acidosis Common Causes of Respiratory Acidosis Signs and Symptoms of (Hypoventilation) Respiratory Acidosis Impaired Gas Exchange Headache, Type B chronic obstructive pulmonary disease Tachycardia, (COPD) End-stage type A COPD Cardiac dysrhythmias, Bacterial pneumonia Neurologic abnormalities Severe asthma episode such as blurred vision, Pulmonary edema tremors, vertigo, Acute (adult) respiratory distress syndrome disorientation, Impaired Neuromuscular Function lethargy, or somnolence. Guillain–Barré syndrome Chest injury or surgery (pain limits ventilation) Hypokalemic respiratory muscle weakness Severe kyphoscoliosis Respiratory muscle fatigue Impaired Respiratory Control (Brainstem) Respiratory depressant drugs (opioids, barbiturates)  Respiratory Alkalosis Common Causes of Respiratory Alkalosis Signs and Symptoms of (Hyperventilation) Respiratory Alkalosis Increased neuromuscular Hypoxemia excitability. Acute pain Paresthesias (numbness and Anxiety, psychological distress tingling) Prolonged sobbing Increasing membrane Initial portion of acute asthma episode excitability in both central Alcohol withdrawal and peripheral neurons Stimulation of the brainstem (salicylate overdose, Altered brain cell function, meningitis, head injury, gram-negative sepsis) causing excitation and/or confusion You are responsible Guyton & Hall Textbook of Medical Physiology 13th Edition pages 410-415 Summary of the major chemical inputs that stimulate ventilation