RESPIRATORY SYSTEM and ACID BASE Arif HM Marsaban Rudyanto Sedono Department of Anesthesiology and Intensive Therapy Faculty of medicine University of Indonesia Dr Cipto Mangunkusumo General Hospital Jakarta 1
Topic relevance Acid base definition Respiratory system and acid base Respiratory acidosis Respiratory alkalosis 2
Definition of Acid-base balance Acid-base balance: Acid-base balance refers to the mechanisms the body uses to keep its fluids close to neutral ph (that is, neither basic nor acidic) so that the body can function normally or maintain normal metabolic process. 3
ACID-BASE.. [H + ] ph 4
ph created by Soren Peter Sorensen chemist from Denmark in 1909, it s mean negative logarithm from hydrogen concentration. The noted of ph mean : potenz (power) of Hydrogen. 5
Normal = 7.40 (7.35-7.45) Viable range = 6.80-7.80 Acidosis ph < 7.35 Alkolosis ph > 7.45 6
Acid-base status can be determined by 2 method : 1. Henderson-Hasselbalch equation 2. Stewart approach 7
Henderson-Hasselbalch ph = pk a + log 10 [ HCO 3 - ] α PCO 2 Base Acid HCO 3 - = metabolic component PCO 2 = respiratory component An increased or decreased of one value will be compensated by the increased or decreased of the other value 8
Stewart approach Independent variable Dependent variable PCO 2 SID ph A TOT 9
Stewart approach Depends on : 1. PCO 2 2. SID = Na + + K + + Ca 2+ + Mg 2+ - Cl - - other strong ion = normal value 40 meq/l 3. A TOT = total weak inorganic phosphate, protein serum, albumin PCO 2 = respiratory component SID & A TOT = metabolic component Other strong ion = lactate -, SO 4 -- 10
Respiratory component that involve in the acidbase system is PCO 2 11
Respiratory System Provide sufficient oxygen for cell metabolism and excreted carbon dioxide as waste product of metabolism 12
Free air: PiO2 : 20.9 % x 760 = 159 mmhg PiCO2 : 0.04 % x 760 = 0.3 mmhg PiN2 : 78.6 % x 760 = 597mmHg ALVEOLUS PiH2O : 0.46 % x 760 = 3.5 mmhg Diffusion process N2 PAN2: 573 mmhg PAO2: 104 mmhg H2O PAH2O: 47 mmhg PACO2: 40 mmhg Lung capillary O2 PaO2: 40 mmhg CO2 PaCO2: 45 mmhg O2 CO2 CO2 PaCO2: 40 mmhg PaO2: 104 mmhg O2 13
Respiratory system maintain PCO 2 35 45 mmhg Acute respiratory disturbances move the value up ( respiratory acidosis ) or down ( respiratory alkalosis ) As respiratory compensation do to metabolic disorder, minute ventilation can increase to compensated metabolic acidosis and minute ventilation suppressed to compensated metabolic alkalosis 14
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Respiratory Acidosis When CO 2 elimination is inadequate relative to the rate of tissue production Increased [ H + ] and [ HCO 3 - ] No change in SID and there for no change in SBE If PCO 2 remain increased, active compensatory mechanisms are activated and SID increased to restore [ H + ] toward normal Primarily compensation is removal Cl from the body by the kidney 16
Acute respiratory acidosis can be caused by CNS suppression, neuromuscular diseases, airway and parenchymal lung disease Chronic respiratory acidosis often caused by chronic lung disease, chest wall disease, central hypoventilation and chronic neuromuscular disease 17
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Treatment Supplemental oxygen If there are signs of respiratory muscle fatigue, mechanical ventilation should be instituted before respiratory failure occurs Chronic hypercapnia require treatment when there is acute deterioration Restoration of the patient s baseline PCO 2 or a target PCO 2 of 60 mmhg 19
Rapid infusion of NaHCO 3 can induce acute respiratory failure if alveolar ventilation is not increased to adjust for the increased CO 2 load NaHCO 3 works by increasing the plasma [ Na + ] Reduce CO 2 production by reduce carbohydrate load in the nutrition, lowering temperature, sedation for anxious patient and treat the shivering 20
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Respiratory Alkalosis May be the most frequently encountered acid base disorder Salicylate intoxication, early sepsis, hepatic failure, hypoxic respiratory disorders, pregnancy, pain and anxiety 22
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Normal values of arterial blood gas analyses ph : 7.35 7.45 PCO2 : 35 45 mmhg PO2 : > 80 mmhg HCO3 : 22 28 meq/l BE : -5 - +5 O2Sat : 95 98% 24
Thank You 25