ARTERIAL BLOOD GASES By Dr Y.N MAURYA M.B.B.S  D.C.H   Medical Officer   Deen Dayal Upadhyay Hospital  Govt.  of  NCT New ...
ARTERIAL BLOOD GASES <ul><li>Arterial blood  gas  sampling  is a medical technique used to check gas levels in the  blood ...
A.B.G SAMPLE COLLECTION <ul><li>ULNER,RADIAL BRACHIAL DORSALIS PEDIS FEMORAL ARTERIES CAN BE USED. </li></ul><ul><li>ARTER...
MODIFIED ALLEN’S TEST <ul><li>1 .  INSTRUCT PATIENT TO CLENCH HIS FIST </li></ul><ul><li>2.  USING YOUR FINGER APPLY OCCLU...
MODIFIED ALLEN’S TEST <ul><li>4. RELEASE THE OCCLUSIVE PRESSURE ON ULNER ARTERY & NOTICE FLUSHING OF HAND WITHIN 7-10 SEC....
SAMPLE SIZE  &  PRECAUTION <ul><li>ABOUT 2 ml  BLOOD IN AIR TIGHT HEPARINISED SYRINGE/ VIAL </li></ul><ul><li>GLASS CAPILL...
CONTRAINDICATION  FOR  ARTERIAL  PUNCTURE <ul><li>INFECTION AT SITE. </li></ul><ul><li>ALLEN’S  TEST  NEGATIVE. </li></ul>...
SpO 2   and  SaO 2 <ul><li>SpO 2  and SaO 2  are often used interchangeably, but they  are not same </li></ul><ul><li>When...
SpO 2   and  SaO 2 <ul><li>SpO 2   ==   HbO 2 </li></ul><ul><li>HbO 2  +  Hb </li></ul><ul><li>SaO 2  ==   HbO 2 </li></ul...
O 2  Saturation & Pulse oximetry <ul><li>We can know arterial blood gases and arterial oxygen saturation from ABG machine ...
O 2  DISSOCIATION CURVE
O 2  Saturation & Pulse oximetry <ul><li>ABG machine  calculates  o 2  saturation based on pH, PaCO 2, temp,by using norma...
O 2  Saturation & Pulse oximetry <ul><li>If we can know arterial blood gases and arterial oxygen saturation with help of A...
O 2  Saturation & Pulse oximetry <ul><li>ADVANTAGE OF PULSE OXIMETRY </li></ul><ul><li>Noninvasive </li></ul><ul><li>Porta...
Principle of Pulse oximetry <ul><li>It is based on different absorption coefficients of oxyHb  & deoxyHb for  different wa...
Principle of Pulse oximetry Absorption Spectrum of Hemoglobin
Pulse  Oximetry <ul><li>1)Pulse oximeter emits two wavelength of lights (red  & infrared)  from  Xenon LED. These lights a...
Pulse  Oximetry <ul><li>4)Accuracy depends on </li></ul><ul><li>a ) % of dysfunctional Hb. </li></ul><ul><li>b ) age of LE...
Pulse  Oximetry <ul><li>There are two types of probes </li></ul><ul><li>1 ) Transmission probe……Finger type </li></ul><ul>...
Hypoxia & Pulse  Oximetry <ul><li>Hypoxic hypoxia…. </li></ul><ul><li>Register low saturation </li></ul><ul><li>Anaemic hy...
SaO 2   and  Pulse  CO- Oximetry <ul><li>Pulse oximeter do’t measure methemoglobin  & carboxyHb.So becomes inaccurate in t...
SaO 2   and  oxygen  content <ul><li>Tissues need a requisite amount of oxygen molecules for metabolism.  Neither the PaO ...
Oxygen dissociation curve:  SaO 2  vs. PaO 2   O 2  content
The Key to Blood Gas Interpretation : <ul><li>Equation   Physiologic Process </li></ul><ul><li>1)  PaCO 2  equation  Alveo...
PaCO 2  equation <ul><li>PaCO 2  =0.863V CO 2 /V A </li></ul><ul><li>V CO 2 ,ml of CO2 produced/ min;  V A, alveolar venti...
Alveolar Gas Equation <ul><li>PAO 2  = PIO 2  - PaCO 2 /R  ,  R= resp.  quotient  </li></ul><ul><li>PAO 2  = PIO 2  - PaCO...
Alveolar Gas Equation   PAO 2  =   FIO 2  (P B  – 47 mm Hg) - 1.2 (PaCO 2 ) <ul><li>Except in a temporary unsteady state, ...
P(A-a)O 2 <ul><li>P(A-a)O 2  is the alveolar-arterial difference in partial pressure of oxygen. it  actually  results from...
Ventilation-Perfusion imbalance <ul><li>A normal amount of ventilation-perfusion (V-Q) imbalance accounts for the normal P...
Henderson - Hasselbalch equation <ul><li>Weak acid ionizes as,  </li></ul><ul><li>HA=H + + A - </li></ul><ul><li>pH = pK+ ...
  Causes of low PaO 2 <ul><ul><li>NON-RESPIRATORY P(A-a)O 2 Cardiac right to left shunt Increased </li></ul></ul><ul><ul><...
NORMAL A.B.G VALUES <ul><li>HB  --  12-15gm/dl </li></ul><ul><li>HCT  --  35-55 </li></ul><ul><li>FIO2  ----- </li></ul><u...
ABG Interpretation <ul><li>First, does the patient have an acidosis or an alkalosis. </li></ul><ul><li>Second, what is the...
ABG Interpretation <ul><li>It would be extremely unusual for either the respiratory or renal system to overcompensate </li...
Abnormal Values <ul><li>pH < 7.35 </li></ul><ul><li>Acidosis (metabolic and/or respiratory) </li></ul><ul><li>pH > 7.45 </...
Putting It Together -  Respiratory <ul><li>So, </li></ul><ul><li>paCO 2  > 45 with a pH < 7.35 represents a  respiratory a...
Putting It Together -  Metabolic <ul><li>And </li></ul><ul><li>HCO 3  < 22 with a pH < 7.35 represents a  metabolic acidos...
Compensation <ul><li>The body’s attempt to return the acid/base status to normal (i.e. pH closer to 7.4) </li></ul><ul><li...
Compensation Decrease  4 mmol/L 0.17 Chr. Resp. Alk. (10 Decr. in PaCO2) Decrease  2  mmol/L 0.08 Ac. Resp. Alk. (10 Decr....
HOW KNOW THE DISORDER > 26 > 45 ~ Normal Compensated > 26 > 45 > 7.45 Partly Compensated > 26 Normal > 7.45 Acute Metaboli...
 
Effectiveness of Oxygenation <ul><li>Further evaluation of the arterial blood gas requires assessment of the effectiveness...
Causes of Hypoxemia <ul><li>Inadequate inspiratory partial pressure of oxygen </li></ul><ul><li>Hypoventilation </li></ul>...
Assessment of Gas Exchange <ul><li>Alveolar-arterial O 2  tension difference </li></ul><ul><ul><li>A-a gradient </li></ul>...
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Arterial Blood Gases

  1. 2. ARTERIAL BLOOD GASES By Dr Y.N MAURYA M.B.B.S D.C.H Medical Officer Deen Dayal Upadhyay Hospital Govt. of NCT New Delhi- 64
  2. 3. ARTERIAL BLOOD GASES <ul><li>Arterial blood gas sampling is a medical technique used to check gas levels in the blood . It typically involves using a thin needle and syringe to puncture an artery , This technique is commonly used on patients whose breathing is controlled by a mechanical respirator or who are having serious difficulties with breathing. </li></ul>
  3. 4. A.B.G SAMPLE COLLECTION <ul><li>ULNER,RADIAL BRACHIAL DORSALIS PEDIS FEMORAL ARTERIES CAN BE USED. </li></ul><ul><li>ARTERIAL LINE ---- FREQUENT SAMPLING </li></ul><ul><li>INTERMITENT STAB---INFREQ. SAMPLING </li></ul><ul><li>UNDER FULL ASEPTIC CONDITION </li></ul><ul><li>IF ULNER/RADIAL ART IS USED --- MODIFIED ALLEN’S TEST </li></ul>
  4. 5. MODIFIED ALLEN’S TEST <ul><li>1 . INSTRUCT PATIENT TO CLENCH HIS FIST </li></ul><ul><li>2. USING YOUR FINGER APPLY OCCLUSIVE PRESSURE ON BOTH RADIAL & ULNER ARTERY </li></ul><ul><li>3. WHILE APPLYING OCCLUSIVE PRESSURE TO BOTH ARTERY,HAVE THE PATIENT RELAX HIS HAND.BLANCHING OF PALM &FINGER SHOULD OCCUR </li></ul>
  5. 6. MODIFIED ALLEN’S TEST <ul><li>4. RELEASE THE OCCLUSIVE PRESSURE ON ULNER ARTERY & NOTICE FLUSHING OF HAND WITHIN 7-10 SEC.THIS DENOTE THAT ULNER ARTERY SUPPLY IS ADEQUATE &IT’S SAFE TO PRICK RADIAL ARTERY. IF IT DOES’T OCCUR IT MAENS ULNER ARTERY SUPPLY IS NOT SUFFICIENT & RADIAL ARTERY IS NOT SAFE TO PRICK. </li></ul>
  6. 7. SAMPLE SIZE & PRECAUTION <ul><li>ABOUT 2 ml BLOOD IN AIR TIGHT HEPARINISED SYRINGE/ VIAL </li></ul><ul><li>GLASS CAPILLARY CAN ALSO BE USED </li></ul><ul><li>COTINUOUS AGITATION BY ROLLING </li></ul><ul><li>FIO2 SHOULD BE WRITTEN ON SAMPLE </li></ul>
  7. 8. CONTRAINDICATION FOR ARTERIAL PUNCTURE <ul><li>INFECTION AT SITE. </li></ul><ul><li>ALLEN’S TEST NEGATIVE. </li></ul><ul><li>ON ANTICOAGULANT THERAPY. </li></ul><ul><li>SEVERE PERIPHERAL VASCULAR DISEASE. </li></ul><ul><li>DISTAL TO SURGICAL SHUNT. </li></ul>
  8. 9. SpO 2 and SaO 2 <ul><li>SpO 2 and SaO 2 are often used interchangeably, but they are not same </li></ul><ul><li>When O 2 saturation is measured by pulse oximeter..... SpO 2 </li></ul><ul><li>When O 2 saturation is measured by CO- oximeter..... SaO 2 </li></ul><ul><li>SpO 2 is also called functional arterial O 2 saturation and SaO 2 as fractional arterial O 2 saturation </li></ul><ul><li>Only true CO-oximeter can determine an accurate value for SaO 2 </li></ul>
  9. 10. SpO 2 and SaO 2 <ul><li>SpO 2 == HbO 2 </li></ul><ul><li>HbO 2 + Hb </li></ul><ul><li>SaO 2 == HbO 2 </li></ul><ul><li>HbO 2 + Hb+COHb+MetHb+SfHb+COSfHb </li></ul><ul><li>SaO 2 == SpO 2 [1-SaCO]… ( Nellcor equation ) </li></ul><ul><li>Non functional Hb is 2-3 % </li></ul><ul><li>In heavy smoaker it may be up to 15 % </li></ul>
  10. 11. O 2 Saturation & Pulse oximetry <ul><li>We can know arterial blood gases and arterial oxygen saturation from ABG machine with help of O 2 DISSOCIATION CURVE . </li></ul>
  11. 12. O 2 DISSOCIATION CURVE
  12. 13. O 2 Saturation & Pulse oximetry <ul><li>ABG machine calculates o 2 saturation based on pH, PaCO 2, temp,by using normal adult o 2 dissociation curve </li></ul><ul><li>o 2 dissociation curve in presence of </li></ul><ul><li>1) fetal Hb ,low 2,3 DPG……curve shifts Lt </li></ul><ul><li>2)sickle cell, chr. Hypoxia, cyanotic H D, chr. Asthama, high altitude…. curve shifts Rt. And ABG machine becomes inaccurate </li></ul>
  13. 14. O 2 Saturation & Pulse oximetry <ul><li>If we can know arterial blood gases and arterial oxygen saturation with help of ABG machine, then what is need of pulse oximeter ? </li></ul>
  14. 15. O 2 Saturation & Pulse oximetry <ul><li>ADVANTAGE OF PULSE OXIMETRY </li></ul><ul><li>Noninvasive </li></ul><ul><li>Portability </li></ul><ul><li>Continuous monitoring </li></ul><ul><li>Ease of use (no calibration) </li></ul><ul><li>Rapidity (warn decr. in saturation before sign and symptom) </li></ul>
  15. 16. Principle of Pulse oximetry <ul><li>It is based on different absorption coefficients of oxyHb & deoxyHb for different wavelength of lights ( BEER’S LAW ) </li></ul><ul><li>For oxyHb & deoxyHb 805nm is isobestic point. </li></ul><ul><li>Above 805 nm oxyHb absorbs more light than deoxyHb & below it deoxyHb absorbs more light than oxyHb. Because of this fact by using two wavelength of lights actual o 2 saturatn level can be measured. </li></ul><ul><li>Pulse oximeter uses two wavelength of light red(660nm) and infrared (950nm). </li></ul>
  16. 17. Principle of Pulse oximetry Absorption Spectrum of Hemoglobin
  17. 18. Pulse Oximetry <ul><li>1)Pulse oximeter emits two wavelength of lights (red & infrared) from Xenon LED. These lights are sensed by photodiodes just opposite to LED or adjacent to LED. </li></ul><ul><li>2)It measures %saturation of deoxyHb with O 2 ( not PaO 2 ) based on absorption spectrum of Hb in pulsatile arterial blood . </li></ul><ul><li>3) Sensitivity rapidly decreases at SpO 2 >90% </li></ul><ul><li>4) Normally in blood dysfunctional Hb is 2-3% hence all oximeters are standardized against known standard CO-oximeter & adjusted, so that it can display SpO 2 close to SaO 2. </li></ul>
  18. 19. Pulse Oximetry <ul><li>4)Accuracy depends on </li></ul><ul><li>a ) % of dysfunctional Hb. </li></ul><ul><li>b ) age of LED. (Aging of LEDcauses change in peak wavelength). </li></ul><ul><li>c ) LED from same batch & same manufacturer may vary by 30nm in peak wavelength. </li></ul><ul><li>d ) Good red & infrared waveform i.e signal strength (tissues are easily penetrated by infrared but not so easily by red. Thus red waveform is lost first, this is why false reading is given when signal is weak) </li></ul>
  19. 20. Pulse Oximetry <ul><li>There are two types of probes </li></ul><ul><li>1 ) Transmission probe……Finger type </li></ul><ul><li>2 ) Reflectance probe…… Rectal type </li></ul><ul><li>Do’t provide accurate reading in CO-poisoning, methemoglobinemia, decreased cut. perfusion, strong vasoconstriction, deep pigmentation, nail polish, intravascular dye, movement, venous pulsation, infrared heating lamp & strong colored lights. </li></ul><ul><li>ECG synchronization technique can be used to remove movement artifact. </li></ul>
  20. 21. Hypoxia & Pulse Oximetry <ul><li>Hypoxic hypoxia…. </li></ul><ul><li>Register low saturation </li></ul><ul><li>Anaemic hypoxia …. </li></ul><ul><li>Normal saturation </li></ul><ul><li>Circulatory hypoxia… </li></ul><ul><li>Low signal strength </li></ul><ul><li>Histotoxic hypoxia… </li></ul><ul><li>Normal saturation </li></ul>
  21. 22. SaO 2 and Pulse CO- Oximetry <ul><li>Pulse oximeter do’t measure methemoglobin & carboxyHb.So becomes inaccurate in these cases. </li></ul><ul><li>IL-282 CO-oximeter is gold standard for o 2 saturation measurement. </li></ul><ul><li>Pulse CO-oximeter emits at least four wavelength of light which measures oxyHb, deoxyHb, methemoglobin & carboxyHb </li></ul><ul><li>For infants pulse oximeter is more useful because CO-oximeter show false elevation of CO-Hb .(fetal Hb absorb more than two wavelength of lights) </li></ul>
  22. 23. SaO 2 and oxygen content <ul><li>Tissues need a requisite amount of oxygen molecules for metabolism. Neither the PaO 2 nor the SaO 2 tells how much oxygen is in the blood. It is provided by the oxygen content, CaO 2 (units = ml O 2 /dl). CaO 2 is calculated as: CaO 2 = quantity O 2 bound + quantity O 2 dissolved to hemoglobin in plasma CaO 2 = (Hb x 1.34 x SaO 2 ) + (.003 x PaO 2 ) </li></ul><ul><li>Hb = hemoglobin in gm%; 1.34 = ml O 2 that can be bound to each gm of Hb; SaO 2 is percent saturation of hemoglobin with oxygen; .003 is solubility coefficient of oxygen in plasma: .003 ml dissolved O 2 /mm Hg PO 2 . </li></ul>
  23. 24. Oxygen dissociation curve: SaO 2 vs. PaO 2 O 2 content
  24. 25. The Key to Blood Gas Interpretation : <ul><li>Equation Physiologic Process </li></ul><ul><li>1) PaCO 2 equation Alveolar ventilation </li></ul><ul><li>1) Alveolar gas equation Oxygenation </li></ul><ul><li>2) Oxygen content equation Oxygenation </li></ul><ul><li>3) Henderson-Hasselbalch equation Acid-base balance </li></ul>
  25. 26. PaCO 2 equation <ul><li>PaCO 2 =0.863V CO 2 /V A </li></ul><ul><li>V CO 2 ,ml of CO2 produced/ min; V A, alveolar ventilation </li></ul><ul><li>V A is increased ……. PaCO 2 decreases </li></ul><ul><li>V A is decreased …. …PaCO 2 increases </li></ul>
  26. 27. Alveolar Gas Equation <ul><li>PAO 2 = PIO 2 - PaCO 2 /R , R= resp. quotient </li></ul><ul><li>PAO 2 = PIO 2 - PaCO 2 / O.8 </li></ul><ul><li>PAO 2 = PIO 2 - 1.2 (PaCO 2 ), </li></ul><ul><li>PIO 2 = FIO 2 (P B – 47 mm Hg) </li></ul><ul><li>PAO 2 = FIO 2 (P B – 47 mm Hg) - 1.2 (PaCO 2 ) </li></ul>
  27. 28. Alveolar Gas Equation PAO 2 = FIO 2 (P B – 47 mm Hg) - 1.2 (PaCO 2 ) <ul><li>Except in a temporary unsteady state, alveolar PO 2 (PAO 2 ) is always higher than arterial PO 2 (PaO 2 ). Thus, </li></ul><ul><li>If FIO 2 & P B are constant , as PaCO 2 increases both PAO 2 and PaO 2 will decrease (hypercapnia causes hypoxemia). </li></ul><ul><li>If P B & PaCO 2 are constant , as FIO 2 decreases both PAO 2 and PaO 2 will decrease (suffocation causes hypoxemia). </li></ul><ul><li>If PaCO 2 & FIO 2 are constant , as P B decreases (e.g., with altitude), both PAO 2 and PaO 2 will decrease (mountain climbing causes hypoxemia). </li></ul>
  28. 29. P(A-a)O 2 <ul><li>P(A-a)O 2 is the alveolar-arterial difference in partial pressure of oxygen. it actually results from gravity-related blood flow changes within the lungs (normal ventilation-perfusion imbalance). </li></ul><ul><li>PAO 2 is always calculated , based on FIO 2 , PaCO 2 and barometric pressure. </li></ul><ul><li>PaO 2 is always measured , in a ‘blood gas machine’. </li></ul><ul><li>Normal P(A-a)O 2 ranges from @ 5 to 25 mm Hg at room air (it increases with age). A higher P(A-a)O 2 means the lungs are not transferring oxygen properly from alveoli into the pulmonary capillaries. Except for right to left cardiac shunts, an elevated P(A-a)O 2 signifies some sort of problem within the lungs. </li></ul><ul><li>If P(A-a)O 2 is negative---there is error in calculation/measurement </li></ul>
  29. 30. Ventilation-Perfusion imbalance <ul><li>A normal amount of ventilation-perfusion (V-Q) imbalance accounts for the normal P(A-a)O 2 . </li></ul><ul><li>Most common cause of low PaO 2 is an abnormal degree of ventilation-perfusion imbalance Virtually all lung disease lowers PaO 2 via V-Q imbalance, e.g., asthma, pneumonia, atelectasis, pulmonary edema, COPD. </li></ul><ul><li>Diffusion barrier is seldom a major cause of low PaO 2 (it can lead to a low PaO 2 during exercise). </li></ul>
  30. 31. Henderson - Hasselbalch equation <ul><li>Weak acid ionizes as, </li></ul><ul><li>HA=H + + A - </li></ul><ul><li>pH = pK+ log[A - ] / [HA] </li></ul>
  31. 32. Causes of low PaO 2 <ul><ul><li>NON-RESPIRATORY P(A-a)O 2 Cardiac right to left shunt Increased </li></ul></ul><ul><ul><li>Decreased PIO 2 Normal Low mixed venous oxygen content* Increased </li></ul></ul><ul><ul><li>RESPIRATORY Pulmonary right to left shunt Increased Ventilation-perfusion imbalance Increased Diffusion barrier Increased Hypoventilation (increased PaCO 2 ) Normal </li></ul></ul><ul><ul><li>*Unlikely to be clinically significant unless there is right to left shunting or ventilation-perfusion imbalance </li></ul></ul>
  32. 33. NORMAL A.B.G VALUES <ul><li>HB -- 12-15gm/dl </li></ul><ul><li>HCT -- 35-55 </li></ul><ul><li>FIO2 ----- </li></ul><ul><li>PaO2 – 80(60)-100mmHg </li></ul><ul><li>PaCO2 – 35-45mmHg </li></ul><ul><li>pH – 7.35-7.45 </li></ul><ul><li>K+ -- 3.5-4.5 mmol/L </li></ul><ul><li>Na+ -- 135-145 mmol/L </li></ul><ul><li>HCO3ˉ -- 22-26 mmol/L </li></ul><ul><li>BE -- ±2 mmol </li></ul><ul><li>SaO 2 -- >90% </li></ul>
  33. 34. ABG Interpretation <ul><li>First, does the patient have an acidosis or an alkalosis. </li></ul><ul><li>Second, what is the primary problem – metabolic or respiratory. </li></ul><ul><li>Third, is there any compensation by the patient – respiratory compensation is immediate while renal compensation takes time. </li></ul>
  34. 35. ABG Interpretation <ul><li>It would be extremely unusual for either the respiratory or renal system to overcompensate </li></ul><ul><li>The pH determines the primary problem </li></ul><ul><li>After determining the primary and compensatory acid/base balance, evaluate the effectiveness of oxygenation </li></ul>
  35. 36. Abnormal Values <ul><li>pH < 7.35 </li></ul><ul><li>Acidosis (metabolic and/or respiratory) </li></ul><ul><li>pH > 7.45 </li></ul><ul><li>Alkalosis (metabolic and/or respiratory) </li></ul><ul><li>paCO 2 > 45 mm Hg </li></ul><ul><li>Respiratory acidosis (alveolar hypoventilation) </li></ul><ul><li>paCO 2 < 35 mm Hg </li></ul><ul><li>Respiratory alkalosis (alveolar hyperventilation) </li></ul><ul><li>HCO 3 < 22 meq/L </li></ul><ul><li>Metabolic acidosis </li></ul><ul><li>HCO 3 > 26 meq/L </li></ul><ul><li>Metabolic alkalosis </li></ul>
  36. 37. Putting It Together - Respiratory <ul><li>So, </li></ul><ul><li>paCO 2 > 45 with a pH < 7.35 represents a respiratory acidosis </li></ul><ul><li>paCO 2 < 35 with a pH > 7.45 represents a respiratory alkalosis </li></ul><ul><li>For a primary respiratory problem, pH and paCO 2 move in the opposite direction </li></ul><ul><ul><li>For each deviation in paCO 2 of 10 mm Hg in either direction, 0. 08 pH units change in the opposite direction </li></ul></ul>
  37. 38. Putting It Together - Metabolic <ul><li>And </li></ul><ul><li>HCO 3 < 22 with a pH < 7.35 represents a metabolic acidosis </li></ul><ul><li>HCO 3 > 26 with a pH > 7.45 represents a metabolic alkalosis </li></ul><ul><li>For a primary metabolic problem, pH and HCO 3 are in the same direction, and paCO 2 is also in the same direction </li></ul>
  38. 39. Compensation <ul><li>The body’s attempt to return the acid/base status to normal (i.e. pH closer to 7.4) </li></ul><ul><li>Primary Problem Compensation </li></ul><ul><li>respiratory acidosis metabolic alkalosis </li></ul><ul><li>respiratory alkalosis metabolic acidosis </li></ul><ul><li>metabolic acidosis respiratory alkalosis </li></ul><ul><li>metabolic alkalosis respiratory acidosis </li></ul>
  39. 40. Compensation Decrease 4 mmol/L 0.17 Chr. Resp. Alk. (10 Decr. in PaCO2) Decrease 2 mmol/L 0.08 Ac. Resp. Alk. (10 Decr. in PaCO2) Increase 3.5 mmol/L 0.03 Chr. Resp. Acid. (10 Incr. in PaCO2) Increase 1 mmol/L 0.08 Ac. Resp. Acid. (10 Incr. in PaCO2) CHANGE IN HCO3 DECR. IN pH DISORDER Inc. 0.5-1/ 1 Inc in HCO3 PaCO2=0.7(HCO3ˉ)+20±1.5 Met.Alkalosis Dec. 1-1.5/1Dec in HCO3ˉ PaCO2=1.5(HCO3ˉ)+8±2 Met.Acidosis Change inPaCO2/ Change in HCO3 PaCO2 DISORDER
  40. 41. HOW KNOW THE DISORDER > 26 > 45 ~ Normal Compensated > 26 > 45 > 7.45 Partly Compensated > 26 Normal > 7.45 Acute Metabolic Alkalosis < 22 < 35 ~ Normal Compensated < 22 < 35 < 7.35 Partly Compensated < 22 Normal < 7.35 Acute Metabolic Acidosis < 22 < 35 ~ Normal Compensated < 22 < 35 > 7.45 Partly Compensated Normal < 35 > 7.45 Acute Respiratory Alkalosis > 26 > 45 ~ Normal Compensated > 26 > 45 < 7.35 Partly Compensated Normal > 45 < 7.35 Acute Respiratory Acidosis HCO 3 ˉ PaCO 2 pH
  41. 43. Effectiveness of Oxygenation <ul><li>Further evaluation of the arterial blood gas requires assessment of the effectiveness of oxygenation of the blood </li></ul><ul><li>Hypoxemia – decreased oxygen content of blood - paO 2 less than 60 mm Hg and the saturation is less than 90% </li></ul><ul><li>Hypoxia – inadequate amount of oxygen available to or used by tissues for metabolic needs </li></ul>
  42. 44. Causes of Hypoxemia <ul><li>Inadequate inspiratory partial pressure of oxygen </li></ul><ul><li>Hypoventilation </li></ul><ul><li>Right to left shunt </li></ul><ul><li>Ventilation-perfusion mismatch </li></ul><ul><li>Incomplete diffusion equilibrium </li></ul>
  43. 45. Assessment of Gas Exchange <ul><li>Alveolar-arterial O 2 tension difference </li></ul><ul><ul><li>A-a gradient </li></ul></ul><ul><ul><li>PAO 2 -PaO 2 </li></ul></ul><ul><ul><li>PAO 2 = FIO 2 (PB - PH 2 O) - PaCO 2 /RQ* </li></ul></ul><ul><li>arterial-inspired O 2 ratio </li></ul><ul><ul><li>PaO 2 /FIO 2 </li></ul></ul><ul><ul><li>P/F ratio </li></ul></ul><ul><li>*RQ=respiratory quotient= 0.8 </li></ul>
  44. 46. THANK YOU
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