Respiratory Acid base balance by Dr. Samreena
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Respiratory Acid base balance by Dr. Samreena Presentation Transcript

  • 1. Respiratory regulation of Acid-Base Balance DR. SUMREENA MANSOOR ASSISTANT PROF OF BIOCHEMISTRY DEPT OF BIOCHEMISTRY & MOLECULAR BIOLOGY
  • 2. pH Review
  • 3. The Body and pH
  • 4.
    • Acids are H + donors.
    • Bases are H + acceptors, or give up OH - in solution.
    • Acids and bases can be:
      • Strong – dissociate completely in solution
        • HCl, NaOH
      • Weak – dissociate only partially in solution
        • Lactic acid, carbonic acid
  • 5. Types of Acids in the Body
    • Volatile acids:
      • Can leave solution and enter the atmosphere.
      • H 2 C0 3 (carbonic acid).
      • Pco 2 is most important factor in pH of body tissues.
  • 6. Types of Acids in the Body
    • Fixed Acids:
      • Acids that do not leave solution.
      • Sulfuric and phosphoric acid.
      • Catabolism of amino acids, nucleic acids, and phospholipids.
  • 7. Types of Acids in the Body
    • Organic Acids:
      • Byproducts of aerobic metabolism, during anaerobic metabolism and during starvation, diabetes.
      • Lactic acid, ketones.
  • 8. Small changes in pH can produce major disturbances
    • Most enzymes function only with narrow pH ranges
    • Acid-base balance can also affect electrolytes (Na + , K + , Cl - )
    • Can also affect hormones
  • 9. The body produces more acids than bases
    • Acids take in with foods
    • Acids produced by metabolism of lipids and proteins
    • Cellular metabolism produces CO 2 .
    • CO 2 + H 2 0 ↔ H 2 CO 3 ↔ H + + HCO 3 -
  • 10. Henderson-Hasselbalch Equation
  • 11. APPLICATIONS OF HH EQUATION
    • Analysis of dissociation of the alanine in the same way as described for acetic acid
    • Use to calculate how pH of a physiologic solution responds to changes in the concentration of a week acid and/or it’s corresponding salt form.
    • Example Bicarbonate buffer system (How HCO 3 and CO 2 Influence pH)
  • 12. APPLICATIONS OF HH EQUATION
    • Useful for calculating ionic forms of acidic and basic drugs.
    • Acidic drug
    • HA H + +A -
    • Example: Aspirin
    • Basic drug
    • BH + B+H +
    • Example: Morphine
    • Drug can readily pass through the membrane if it is uncharged
  • 13. APPLICATIONS OF HH EQUATION
    • How much drug is found on either side of a membrane that separates two compartments that differ in pH, for example, the stomach (pH 1.0-1.5) and blood plasma (pH 7.4)
  • 14. Buffer Systems
    • Provide or remove H + and stabilize the pH.
    • Include weak acids that can donate H + and weak bases that can absorb H + .
    • Change in pH, after addition of acid, is less than it would be in the absence of buffer.
  • 15. Chemical Buffers
    • Act within fraction of a second.
    • Protein.
    • HCO 3 - .
    • Phosphate.
  • 16. Proteins
    • COOH or NH 2 .
    • Largest pool of buffers in the body.
    • pKa close to plasma.
    • Albumin, globulins such as Hb.
  • 17. Protein Buffers
    • Includes hemoglobin, work in blood
    • Carboxyl group gives up H +
    • Amino Group accepts H +
    • Glutamate, aspartate, histidine, arginine, lysine
    • Additional potentially charged groups in side chain
  • 18. Bicarbonate buffer
    • Sodium Bicarbonate (NaHCO 3 ) and carbonic acid (H 2 CO 3 )
    • Maintain a 20:1 ratio : HCO 3 - : H 2 CO 3
    • HCl + NaHCO 3 ↔ H 2 CO 3 + NaCl
    • NaOH + H 2 CO 3 ↔ NaHCO 3 + H 2 O
  • 19. HCO 3 -
    • pk= 6.1
    • Most important ECF buffer.
    • Present in large quantities.
    • Respiratory and renal systems act on this buffer system.
  • 20. Phosphate buffer
    • Major intracellular buffer
    • H + + HPO 4 2- ↔ H 2 PO4 -
    • OH - + H 2 PO 4 - ↔ H 2 O + HPO 4 2-
    • pk = 6.8
    • Better buffer in ICF (kidneys and bone)
  • 21. Rates of correction
    • Buffers function almost instantaneously
    • Respiratory mechanisms take several minutes to hours
    • Renal mechanisms may take several hours to days
  • 22.  
  • 23. Respiratory System
    • 2nd line of defense.
    • Acts within min. maximal in 12-24 hrs.
    • H 2 CO 3 produced converted to CO 2 , and excreted by the lungs.
    • Powerful, but works with volatile acids
    • Exhalation of carbon dioxide.
    • CO 2 + H 2 0 ↔ H 2 CO 3 ↔ H + + HCO 3 -
    • Body pH can be adjusted by changing rate and depth of breathing
  • 24. Renal system
    • Can eliminate large amounts of acid
    • Can conserve and produce bicarbonate ions
    • Most effective regulator of pH
    • If kidneys fail pH balance fails
  • 25. Urinary Buffers
    • Urine pH = 4.5
    • H + secreted into the urine tubule and combines with HPO 4 -2 or NH 3 .
    • HPO 4 -2 + H + H 2 PO 4 -2
    • NH 3 + H + NH 4 +
  • 26.  
  • 27. Acid-Base Imbalances
    • pH< 7.35 acidosis
    • pH > 7.45 alkalosis
    • The body response to acid-base imbalance is called compensation
    • May be complete if brought back within normal limits
    • Partial compensation if range is still outside norms.
  • 28. Compensation
    • If underlying problem is metabolic, hyperventilation or hypoventilation can help : respiratory compensation
    • If problem is respiratory, renal mechanisms can bring about metabolic compensation
  • 29. Acidosis
    • Principal effect of acidosis is depression of the CNS through ↓ in synaptic transmission
    • Generalized weakness
    • Deranged CNS function the greatest threat
    • Severe acidosis causes
      • Disorientation
      • Coma
      • Death
  • 30. Alkalosis
    • Alkalosis can cause
    • It can cause :
      • Nervousness
      • Muscle spasms or tetany
      • Convulsions
      • Loss of consciousness
      • Death
  • 31.  
  • 32. Respiratory Acidosis
    • Carbonic acid excess caused by blood levels of CO 2 above 45 mm Hg
    • Hypercapnia – High levels of CO 2 in blood
    • Chronic conditions:
      • Depression of respiratory center in brain that controls breathing rate – drugs or head trauma
      • Paralysis of respiratory or chest muscles
      • Emphysema
  • 33. Respiratory Acidosis
    • Acute conditions:
      • Adult Respiratory Distress Syndrome
      • Pulmonary edema
      • Pneumothorax
  • 34. Compensation for Respiratory Acidosis
    • Kidneys eliminate hydrogen ion and retain bicarbonate ion
    • Acute respiratory failure:
    • pH low,[HCO - 3 ] high normal, or slightly raised
    • Chronic respiratory failure:
    • pH normal or low depending upon chronicity,[HCO - 3 ] raised
  • 35. Signs and Symptoms of Respiratory Acidosis
    • Breathlessness
    • Restlessness
    • Lethargy and disorientation
    • Tremors, convulsions, coma
    • Respiratory rate rapid then gradually depressed
    • Skin warm and flushed due to vasodilatation caused by excess CO 2
  • 36. Treatment of Respiratory Acidosis
    • Restore ventilation
    • Treat underlying dysfunction or disease
  • 37.  
  • 38. Respiratory Alkalosis
    • Carbonic acid deficit
    • pCO 2 less than 35 mm Hg (hypocapnea)
    • Primary cause is hyperventilation
  • 39. Respiratory Alkalosis
    • Conditions that stimulate respiratory center:
    • Hysterical over breathing (overrides normal respiratory control)
    • Raised ICP (Which stimulate respiratory centre)
    • Hypoxia
    • Pulmonary edema
    • Lobar pneumonia
    • Pulmonary collapse or fibrosis
    • Excessive artificial ventilation
  • 40. Compensation of Respiratory Alkalosis
    • Compensatory fall in plasma [HCO - 3 ] tends to correct the pH
    • Pco 2 always reduced
    • [HCO - 3 ] low normal or low
    • pH raised (uncompensated or partly compensated) or normal (fully compensated)
  • 41. Treatment of Respiratory Alkalosis
    • Treat underlying cause
    • IV Chloride containing solution – Cl - ions replace lost bicarbonate ions
  • 42.  
  • 43. THANKS