Interpretation of Arterial Blood Gases (ABG)

Interpretation of Arterial Blood Gases (ABG) Prof. Dr. W. Vincken Head Respiratory Division Universitair Ziekenhuis Brussel (UZ Brussel) Vrije Universiteit Brussel (VUB) 29-3-2015 W Vincken - UZ Brussel - VUB 1

ABG: puncture Patient At rest for 5-15 Minimize anxiety/pain (hyperventilation) A. radialis puncture at non-dominant side Allen test Strictly aseptic 29-3-2015 W Vincken - UZ Brussel - VUB 2

ABG: puncture Syringe Glass > plastic (gas-permeable) Polypropylene > polystyrol Dry heparin Max 5% of sample volume Draw blood slowly up (avoid hemolysis) 29-3-2015 W Vincken - UZ Brussel - VUB 3

ABG: puncture Remove air bubbles before mixing/cooling Mix sample thoroughly turn 5 x up and down slowly and roll horizontally for 5 Immediate transport (within 10 ) If not: Store at 0-4 C in icewater Do not store directly on ice (hemolysis) 29-3-2015 W Vincken - UZ Brussel - VUB 4

Before interpretation of ABG Make/take note of F I O 2 : room air (0.21) or under O 2 therapy Body posture: sitting or supine At rest or during exercise 29-3-2015 W Vincken - UZ Brussel - VUB 5

ABG: parameters Parameters of oxygenation P a O 2 S a O 2 P A-a O 2 29-3-2015 W Vincken - UZ Brussel - VUB 7

ABG: parameters Parameters of oxygenation Parameters of alveolar ventilation and acid-base status P a O 2 S a O 2 P A-a O 2 P a CO 2 ph [HCO 3- ] Base Excess (BE) 29-3-2015 W Vincken - UZ Brussel - VUB 8

ABG: normal values Parameters of oxygenation P a O 2 100 mmhg* [105 (age/3)] S a O 2 > 97 % P A-a O 2 <10 mmhg (up to 20 mmhg in elderly) *7.5 mmhg = 1 kpa 29-3-2015 W Vincken - UZ Brussel - VUB 9

ABG: normal values Parameters of alveolar ventilation and acid-base status P a CO 2 40 mmhg (35 45 mmhg) ph 7.4 (7.35 7.45) [HCO 3- ] 24 mmol/l Base Excess (BE) 0 mmol/l 29-3-2015 W Vincken - UZ Brussel - VUB 10

Abnormal ABG: hyperoxemia High P a O 2 No pathophysiological substrate (except mild hyperoxemia in extreme alveolar hyperventilation) Usually indicates sampling error (air in blood sample) or high F I O 2 (oxygen administration) 29-3-2015 W Vincken - UZ Brussel - VUB 11

Abnormal ABG: hypoxemia Low P a O 2 Desaturation : low S a O 2 29-3-2015 W Vincken - UZ Brussel - VUB 12

Hypoxemia calculate P A-a O 2 Hypoxemia with P A-a O 2 = respiratory failure type I = oxygenation (lung) failure Hypoxemia with normal P A-a O 2 = respiratory failure type II = ventilatory (pump) failure 29-3-2015 W Vincken - UZ Brussel - VUB 15

Hypoxemia: calculate the Alveolo-arterial PO 2 gradient P A-a O 2 (mmhg) = P A O 2 - P a O 2 P A O 2 is calculated using the alveolar gas equation P A O 2 = P I O 2 [P A CO 2 / R] P A O 2 = [(P b - P H 2O) x F I O 2 ] [P a CO 2 / 0.8] P A O 2 = [(760-47) x 0.21] [P a CO 2 x 1.25] P A O 2 = 149 [P a CO 2 x 1.25] P a O 2 and P a CO 2 are measured (ABG) Normal P A-a O 2 < 5 10 mmhg (up to 20 mmhg in elderly) 29-3-2015 W Vincken - UZ Brussel - VUB 17

Hypoxemia: 3 main causes P A-a O 2 = P A O 2 P a O 2 P a O 2 = P A O 2 P A-a O 2 (1) Reduced P A O 2 (2) Increased P A-a O 2 (3) Reduced P v O 2 29-3-2015 W Vincken - UZ Brussel - VUB 18

Hypoxemia (1): due to reduced P A O 2 * P a O 2 = P A O 2 P A-a O 2 P A O 2 = P I O 2 [P A CO 2 / R] P A O 2 = [( P b - P H 2O) x F I O 2 ] [P A CO 2 / R] Reduced P I O 2 Reduced P b : high altitude Reduced F I O 2 : inhalation of hypoxic gas mixtures Increased P A CO 2 = hypercapnia = Ventilatory failure or Type II Respiratory Failure * and normal P A-a O 2 29-3-2015 W Vincken - UZ Brussel - VUB 19

Hypoxemia (2): due to increased P A-a O 2 P a O 2 = P A O 2 P A-a O 2 = Failure of the lung as a gas exchanger = Intrapulmonary mechanism/cause of hypoxemia = Oxygenation failure or Type I Respiratory Failure Ventilation/perfusion mismatch Diffusion limitation Right Left shunt 29-3-2015 W Vincken - UZ Brussel - VUB 20

Hypoxemia (2): Oxygenation failure Ventilation/Perfusion mismatch (R>L shunt-like effect of regions with low V/Q ratio) obstructive lung diseases (COPD, asthma, ) parenchymal lung disease (pneumonia, atelectasis, ILD, ) vascular lung disease 29-3-2015 W Vincken - UZ Brussel - VUB 21

Hypoxemia (2): Oxygenation failure Diffusion limitation (with exercise and reduced transit time of RBCs in pulmonary capillaries) increased thickness of alveolocapillary membrane Interstitial lung diseases reduced surface area of alveolocapillary membrane Emphysema 29-3-2015 W Vincken - UZ Brussel - VUB 22

Hypoxemia (2): Oxygenation failure Anatomic R L shunt (leads to refractory hypoxemia) intracardiac (ASD, VSD, ) intrapulmonary (A-V malformations, fistulas) 29-3-2015 W Vincken - UZ Brussel - VUB 23

Hypoxemia: consequences (1) Desaturation central cyanosis Chemoreceptor stimulation Central respiratory drive Output respiratory muscles V E and WOB : dyspnea V A and hypocapnia & respiratory alkalosis 29-3-2015 W Vincken - UZ Brussel - VUB 29

Hypoxemia: consequences (2) Tissue hypoxia organ disfunction: CNS, CV, kidneys anaerobic metabolism lactic acidosis Pulmonary vasoconstriction pulmonary hypertension cor pulmonale & right heart failure Increased renal erythropoetin production secondary polycythemia 29-3-2015 W Vincken - UZ Brussel - VUB 30

Abnormal ABG: hypercapnia High P a CO 2 (> 45 mmhg) Respiratory acidosis : low ph (< 7.35) ph = pk + log [HCO 3- ] / 0.03 x PCO 2 29-3-2015 W Vincken - UZ Brussel - VUB 31

Hypercapnia: 4 main causes P a CO 2 = VCO 2 / V A VCO 2 = CO 2 production V A = alveolar ventilation = V E - V D (1) Increased VCO 2 (2) Reduced V A (reduced V E and normal V D ) (3) Increased V D (4) Severe V/Q mismatching 29-3-2015 W Vincken - UZ Brussel - VUB 35

Hypercapnia (1): increased VCO 2 P a CO 2 = VCO 2 / V A Exercise with extreme effort Fever and other hypermetabolic states in patients unable to increase V E and V A, e.g., mechanically ventilated patient 29-3-2015 W Vincken - UZ Brussel - VUB 36

Hypercapnia (2): reduced V A P a CO 2 = VCO 2 / V A Reduced V A = alveolar hypoventilation = Ventilatory failure or Type II respiratory failure Any hypoxemia is secondary to hypercapnia, i.e., the P A-a O 2 is normal Extrapulmonary mechanism/cause of hypoxemia: Severe UAO Failure of the ventilatory pump 29-3-2015 W Vincken - UZ Brussel - VUB 37

Hypercapnia (2): Failure of the ventilatory pump (a) Reduced respiratory drive (central controller) CNS disorders Drug (illicit or not) overdose Metabolic disorders Obesity-hypoventilation syndrome (Pickwick syndrome) Central alveolar hypoventilation (Ondine s curse, ) 29-3-2015 W Vincken - UZ Brussel - VUB 39

Hypercapnia (2): Failure of the ventilatory pump (b) Dysfunction of respiratory neuromuscular apparatus Motor neurons (ALS, poliomyelitis, ) Peripheral nerve (Guillain-Barré, phrenic neuropathy, ) Myoneural junction (myastenia, drugs, ) Muscle (myopathy, metabolic disorders, malnutrition, ) 29-3-2015 W Vincken - UZ Brussel - VUB 40

Hypercapnia (2): Failure of the ventilatory pump (c) Chest wall disorders including severe obesity Kyphoscoliosis TBC sequellae incl. thoracoplasty Severe obesity 29-3-2015 W Vincken - UZ Brussel - VUB 41

Hypercapnia: consequences Hypoxemia with normal P A-a O 2 P a O 2 decreases with 1.25 mmhg/mmhg P a CO 2 increase Respiratory acidosis: reduced ph If persistent: HCO 3- retention by the kidneys increased [HCO 3- ] and positive BE the reduced ph will increase towards 7.4 (normal) but not overshoot it ph = pk + log [HCO 3- ] / 0.03 x PCO 2 ph = pk + log [ HCO 3- ] / 0.03 x PCO 2 Compensatory metabolic alkalosis Acutely, Δ HCO 3- = 0.1 x Δ P a CO 2 Chronically, Δ HCO 3- = 0.35 x Δ P a CO 2 29-3-2015 W Vincken - UZ Brussel - VUB 44

Clinical signs of hypercapnia CNS: cerebral vasodilatation increased cerebral Q intracranial hypertension headache, papilledema asterixis lethargy, confusion progressing to coma carbonarcosis Peripheral vasodilatation full bounding pulses with warm, cherry-red skin 29-3-2015 W Vincken - UZ Brussel - VUB 45

Abnormal ABG: hypocapnia Low P a CO 2 (< 35 mmhg) Respiratory alkalosis: high ph (> 7.45) ph = pk + log [HCO 3- ] / 0.03 x PCO 2 29-3-2015 W Vincken - UZ Brussel - VUB 47

Hypocapnia: 1 main mechanism P a CO 2 = VCO 2 / V A Increased V A = alveolar hyperventilation 29-3-2015 W Vincken - UZ Brussel - VUB 48

Hypocapnia ~ alveolar hyperventilation: causes Stimulation of chemoreceptors Hypoxemia Metabolic acidosis Pulmonary J-receptor stimulation Interstitial/parenchymal lung diseases Tissue hypoxia Anemia, CO-, sulf- or methb Sepsis, hypotension, shock (also stimulation of baroreceptors) Fever, thyrotoxicosis, strenuous exercise Psychogenic : hyperventilation syndrome = diagnosis of exclusion 29-3-2015 W Vincken - UZ Brussel - VUB 49

Hypocapnia: consequences Respiratory alkalosis: increased ph If persistent: HCO 3- excretion by the kidneys reduced [HCO 3- ] and negative BE (= base deficit) increased ph will decrease towards (but not below) 7.4 ph = pk + log [HCO 3- ] / 0.03 x PCO 2 ph = pk + log [ HCO 3- ] / 0.03 x PCO 2 Compensatory metabolic acidosis Acutely, Δ HCO 3- = 0.2 x Δ P a CO 2 Chronically, Δ HCO 3- = 0.5 x Δ P a CO 2 29-3-2015 W Vincken - UZ Brussel - VUB 50

Abnormal ABG: acid-base disorders Acidosis: low ph Respiratory Metabolic Alkalosis: high ph Respiratory Metabolic 29-3-2015 W Vincken - UZ Brussel - VUB 51

Metabolic acidosis ph = pk + log [ HCO 3- ] / 0.03 x PCO 2 ph due to HCO 3- and negative BE (base deficit), due to Acid [H + ] accumulation (and buffering by HCO 3- ) renal failure diabetes mellitus: ketoacidosis tissue hypoxia/hypoperfusion (shock): lactic acidosis intoxications: ASA, antifreeze, methanol, paraldehyde Loss of HCO 3 - diarrhea 29-3-2015 W Vincken - UZ Brussel - VUB 52

Metabolic acidosis If persistent, the ph (hence increase in [H + ]) leads to: chemoreceptor stimulation increased central respiratory drive increased V E and V A : hyperventilation hypocapnia the low ph rises towards normal (not exceeding 7.4) compensatory respiratory alkalosis Δ P a CO 2 = 1 à 1.3 x Δ HCO 3 - ph = pk + log [ HCO 3- ] / 0.03 x PCO 2 ph = pk + log [ HCO 3- ] / 0.03 x PCO 2 29-3-2015 W Vincken - UZ Brussel - VUB 53

Metabolic alkalosis ph = pk + log [ HCO 3- ] / 0.03 x PCO 2 ph due to HCO 3- and positive BE, due to HCO 3- accumulation Excessive ingestion of alkali Drug intake: diuretics, corticosteroids Cushing syndrome Hypokalemia Loss of acid Loss of gastric acid: prolonged vomiting, nasogastric suction Via kidneys 29-3-2015 W Vincken - UZ Brussel - VUB 54

Metabolic alkalosis If persistent, the ph (hence reduction in [H + ]) leads to: reduced chemoreceptor stimulation reduced central respiratory drive reduced V E and V A : hypoventilation hypercapnia the increased ph will decrease towards normal (but not below 7.4) compensatory respiratory acidosis Δ P a CO 2 = 0.6 x Δ HCO 3 - ph = pk + log [ HCO 3- ] / 0.03 x PCO 2 ph = pk + log [ HCO 3- ] / 0.03 x PCO 2 29-3-2015 W Vincken - UZ Brussel - VUB 55

Arterial Blood Gases : main use Note sampling conditions Careful sampling and handling Detection of Respiratory Failure Detection of Acid-Base disturbances 29-3-2015 W Vincken - UZ Brussel - VUB 56

Interpretation of ABG Oxygenation Look at P a O 2 and S a O 2 Calculate P A-a O 2 Alveolar ventilation Look at P a CO 2 Acid-Base status Look at ph, HCO 3- and BE 29-3-2015 W Vincken - UZ Brussel - VUB 57

Thank you for listening Hope you learned something, or at least enjoyed it Prof. Dr. W. Vincken Head Respiratory Division UZ Brussel, VUB 29-3-2015 W Vincken - UZ Brussel - VUB 58

Interpretation of ABG 10 examples 29-3-2015 W Vincken - UZ Brussel - VUB 59

Interpretation of ABG : example 1 P a O 2 mmhg 69 S a O 2 % 91 P A-a O 2 mmhg calculate P a CO 2 mmhg 60 ph 7.2 HCO - 3 meq/l 24 BE meq/l 0 29-3-2015 W Vincken - UZ Brussel - VUB 60

Interpretation of ABG : example 1 P a O 2 mmhg 69 S a O 2 % 91 P A-a O 2 mmhg 149 60x1.25 69 = 5 P a CO 2 mmhg 60 ph 7.2 HCO - 3 meq/l 24 BE meq/l 0 29-3-2015 W Vincken - UZ Brussel - VUB 61

Interpretation of ABG : example 1 P a O 2 mmhg 69 Hypoxemia S a O 2 % 91 Desaturation P A-a O 2 mmhg 5 Normal P a CO 2 mmhg 60 ph 7.2 HCO - 3 meq/l 24 BE meq/l 0 29-3-2015 W Vincken - UZ Brussel - VUB 62

Interpretation of ABG : example 1 Oxygenation Reduced P a O 2 and S a O 2 69/91% = mild hypoxemia and arterial desaturation Normal P A-a O 2 5 = hypoxemia is due to Ventilatory failure = Failure of the respiratory air pump, or Reduced P A O 2, or Reduced P v O 2 29-3-2015 W Vincken - UZ Brussel - VUB 63

Interpretation of ABG : example 1 P a O 2 mmhg 69 Hypoxemia S a O 2 % 91 Desaturation P A-a O 2 mmhg 5 Normal P a CO 2 mmhg 60 Hypercapnia ph 7.2 Acidosis HCO 3 - meq/l 24 Normal BE meq/l 0 Normal 29-3-2015 W Vincken - UZ Brussel - VUB 64

Interpretation of ABG : example 1 P a O 2 mmhg 69 Hypoxemia S a O 2 % 91 Desaturation P A-a O 2 mmhg 5 Normal Type II RF P a CO 2 mmhg 60 Hypercapnia Respiratory ph 7.2 Acidosis Acidosis HCO - 3 meq/l 24 Normal Acute BE meq/l 0 Normal 29-3-2015 W Vincken - UZ Brussel - VUB 65

Interpretation of ABG : example 2 P a O 2 mmhg 69 S a O 2 % 91 P A-a O 2 mmhg calculate P a CO 2 mmhg 60 ph 7.37 HCO - 3 meq/l 34 BE meq/l + 10 29-3-2015 W Vincken - UZ Brussel - VUB 66

Interpretation of ABG : example 2 P a O 2 mmhg 69 S a O 2 % 91 P A-a O 2 mmhg 149 60x1.25 69 = 5 P a CO 2 mmhg 60 ph 7.37 HCO - 3 meq/l 34 BE meq/l + 10 29-3-2015 W Vincken - UZ Brussel - VUB 67

Interpretation of ABG : example 2 P a O 2 mmhg 69 Hypoxemia S a O 2 % 91 Desaturation P A-a O 2 mmhg 5 Normal P a CO 2 mmhg 60 ph 7.37 HCO - 3 meq/l 34 BE meq/l + 10 29-3-2015 W Vincken - UZ Brussel - VUB 68

Interpretation of ABG : example 2 P a O 2 mmhg 69 Hypoxemia S a O 2 % 91 Desaturation P A-a O 2 mmhg 5 Normal P a CO 2 mmhg 60 Hypercapnia ph 7.37 Minimal acidosis HCO - 3 meq/l 34 Increased BE meq/l + 10 Positive 29-3-2015 W Vincken - UZ Brussel - VUB 69

Interpretation of ABG : example 2 P a O 2 mmhg 69 Hypoxemia S a O 2 % 91 Desaturation P A-a O 2 mmhg 5 Normal Type II RF P a CO 2 mmhg 60 Hypercapnia Respiratory ph 7.37 Minimal acidosis Acidosis HCO 3 - meq/l 34 Increased Chronic BE meq/l + 10 Positive Compensatory metabolic alkalosis 29-3-2015 W Vincken - UZ Brussel - VUB 70

Interpretation of ABG : example 3 P a O 2 mmhg 99 S a O 2 % 98 P A-a O 2 mmhg calculate P a CO 2 mmhg 30 ph 7.50 HCO - 3 meq/l 24 BE meq/l 0 29-3-2015 W Vincken - UZ Brussel - VUB 71

Interpretation of ABG : example 3 P a O 2 mmhg 99 S a O 2 % 98 P A-a O 2 mmhg 149 30x1.25 99 = 12.5 P a CO 2 mmhg 30 ph 7.50 HCO - 3 meq/l 24 BE meq/l 0 29-3-2015 W Vincken - UZ Brussel - VUB 72

Interpretation of ABG : example 3 P a O 2 mmhg 99 Normal S a O 2 % 98 Normal P A-a O 2 mmhg 12.5 Normal P a CO 2 mmhg 30 Hypocapnia ph 7.50 Alkalosis HCO 3 - meq/l 24 Normal BE meq/l 0 Normal 29-3-2015 W Vincken - UZ Brussel - VUB 73

Interpretation of ABG : example 3 P a O 2 mmhg 99 Normal S a O 2 % 98 Normal P A-a O 2 mmhg 12.5 Normal P a CO 2 mmhg 30 Hypocapnia Respiratory ph 7.50 Alkalosis Alkalosis HCO - 3 meq/l 24 Normal Acute BE meq/l 0 Normal 29-3-2015 W Vincken - UZ Brussel - VUB 74

Interpretation of ABG : example 4 P a O 2 mmhg 99 S a O 2 % 98 P A-a O 2 mmhg 12.5 P a CO 2 mmhg 30 ph 7.42 HCO - 3 meq/l 20 BE meq/l - 4 29-3-2015 W Vincken - UZ Brussel - VUB 75

Interpretation of ABG : example 4 P a O 2 mmhg 99 Normal S a O 2 % 98 Normal P A-a O 2 mmhg 12.5 Normal P a CO 2 mmhg 30 ph 7.42 HCO - 3 meq/l 20 BE meq/l - 4 29-3-2015 W Vincken - UZ Brussel - VUB 76

Interpretation of ABG : example 4 P a O 2 mmhg 99 Normal S a O 2 % 98 Normal P A-a O 2 mmhg 12.5 Normal P a CO 2 mmhg 30 Hypocapnia ph 7.42 Minimal alkalosis HCO 3 - meq/l 20 Reduced BE meq/l - 4 Negative 29-3-2015 W Vincken - UZ Brussel - VUB 77

Interpretation of ABG : example 4 P a O 2 mmhg 99 Normal S a O 2 % 98 Normal P A-a O 2 mmhg 12.5 Normal P a CO 2 mmhg 30 Hypocapnia Respiratory ph 7.42 Minimal alkalosis Alkalosis HCO 3 - meq/l 20 Reduced Chronic BE meq/l - 4 Negative Compensatory metabolic acidosis 29-3-2015 W Vincken - UZ Brussel - VUB 78

Interpretation of ABG : example 5 P a O 2 mmhg 60 S a O 2 % 88 P A-a O 2 mmhg calculate P a CO 2 mmhg 32 ph 7.49 HCO - 3 meq/l 24 BE meq/l 0 29-3-2015 W Vincken - UZ Brussel - VUB 79

Interpretation of ABG : example 5 P a O 2 mmhg 60 S a O 2 % 88 P A-a O 2 mmhg 149 32x1.25 60 = 49 P a CO 2 mmhg 32 ph 7.49 HCO - 3 meq/l 24 BE meq/l 0 29-3-2015 W Vincken - UZ Brussel - VUB 80

Interpretation of ABG : example 5 P a O 2 mmhg 60 Hypoxemia S a O 2 % 88 Desaturation P A-a O 2 mmhg 49 Increased P a CO 2 mmhg 32 ph 7.49 HCO - 3 meq/l 24 BE meq/l 0 29-3-2015 W Vincken - UZ Brussel - VUB 81

Interpretation of ABG : example 5 Oxygenation reduced P a O 2 and S a O 2 60/88% = hypoxemia and arterial desaturation Increased P A-a O 2 49 = hypoxemia is due to Oxygenation failure Failure of the lung as a gas exchanger Intrapulmonary disease Ventilation/perfusion mismatch Diffusion limitation Right>Left shunt 29-3-2015 W Vincken - UZ Brussel - VUB 82

Interpretation of ABG : example 5 P a O 2 mmhg 60 Hypoxemia S a O 2 % 88 Desaturation P A-a O 2 mmhg 49 Increased P a CO 2 mmhg 32 Hypocapnia ph 7.49 Alkalosis HCO 3 - meq/l 24 Normal BE meq/l 0 Normal 29-3-2015 W Vincken - UZ Brussel - VUB 83

Interpretation of ABG : example 5 P a O 2 mmhg 60 Hypoxemia S a O 2 % 88 Desaturation P A-a O 2 mmhg 49 Increased Type I RF P a CO 2 mmhg 32 Hypocapnia Respiratory ph 7.49 Alkalosis Alkalosis HCO - 3 meq/l 24 Normal Acute BE meq/l 0 Normal 29-3-2015 W Vincken - UZ Brussel - VUB 84

Interpretation of ABG : example 6 P a O 2 mmhg 60 S a O 2 % 88 P A-a O 2 mmhg 49 P a CO 2 mmhg 32 ph 7.42 HCO - 3 meq/l 18 BE meq/l - 6 29-3-2015 W Vincken - UZ Brussel - VUB 85

Interpretation of ABG : example 6 P a O 2 mmhg 60 Hypoxemia S a O 2 % 88 Desaturation P A-a O 2 mmhg 49 Increased P a CO 2 mmhg 32 ph 7.42 HCO - 3 meq/l 18 BE meq/l - 6 29-3-2015 W Vincken - UZ Brussel - VUB 86

Interpretation of ABG : example 6 P a O 2 mmhg 60 Hypoxemia S a O 2 % 88 Desaturation P A-a O 2 mmhg 49 Increased Type I RF P a CO 2 mmhg 32 Hypocapnia ph 7.42 Minimal alkalosis HCO 3 - meq/l 18 Reduced BE meq/l - 6 Negative 29-3-2015 W Vincken - UZ Brussel - VUB 87

Interpretation of ABG : example 6 P a O 2 mmhg 60 Hypoxemia S a O 2 % 88 Desaturation P A-a O 2 mmhg 49 Increased Type I RF P a CO 2 mmhg 32 Hypocapnia Respiratory ph 7.42 Minimal alkalosis Alkalosis HCO 3 - meq/l 18 Reduced Chronic BE meq/l - 6 Negative Compensatory Metabolic acidosis 29-3-2015 W Vincken - UZ Brussel - VUB 88

Interpretation of ABG : example 7 P a O 2 mmhg 92 S a O 2 % 94 P A-a O 2 mmhg calculate P a CO 2 mmhg 40 ph 7.27 HCO - 3 meq/l 16 BE meq/l - 7 29-3-2015 W Vincken - UZ Brussel - VUB 89

Interpretation of ABG : example 7 P a O 2 mmhg 92 S a O 2 % 94 P A-a O 2 mmhg 149 40x1.25 92 = 7 P a CO 2 mmhg 40 ph 7.27 HCO - 3 meq/l 16 BE meq/l - 7 29-3-2015 W Vincken - UZ Brussel - VUB 90

Interpretation of ABG : example 7 P a O 2 mmhg 92 Normoxemia S a O 2 % 94 Normal P A-a O 2 mmhg 7 Normal P a CO 2 mmhg 40 ph 7.27 HCO - 3 meq/l 16 BE meq/l - 7 29-3-2015 W Vincken - UZ Brussel - VUB 91

Interpretation of ABG : example 7 P a O 2 mmhg 92 Normoxemia S a O 2 % 94 Normal P A-a O 2 mmhg 7 Normal P a CO 2 mmhg 40 Normocapnia ph 7.27 Acidosis HCO 3 - meq/l 16 Reduced BE meq/l - 7 Negative 29-3-2015 W Vincken - UZ Brussel - VUB 92

Interpretation of ABG : example 7 P a O 2 mmhg 92 Normoxemia S a O 2 % 94 Normal P A-a O 2 mmhg 7 Normal P a CO 2 mmhg 40 Normocapnia Acute ph 7.27 Acidosis Acidosis HCO - 3 meq/l 16 Reduced Metaboli c BE meq/l - 7 Negative 29-3-2015 W Vincken - UZ Brussel - VUB 93

Interpretation of ABG : example 8 P a O 2 mmhg 100 S a O 2 % 97 P A-a O 2 mmhg calculate P a CO 2 mmhg 30 ph 7.37 HCO - 3 meq/l 16 BE meq/l - 7 29-3-2015 W Vincken - UZ Brussel - VUB 94

Interpretation of ABG : example 8 P a O 2 mmhg 100 S a O 2 % 97 P A-a O 2 mmhg 149 30x1.25 100 = 12 P a CO 2 mmhg 30 ph 7.37 HCO - 3 meq/l 16 BE meq/l - 7 29-3-2015 W Vincken - UZ Brussel - VUB 95

Interpretation of ABG : example 8 P a O 2 mmhg 100 Normoxemia S a O 2 % 97 Normal P A-a O 2 mmhg 12 Normal P a CO 2 mmhg 30 ph 7.37 HCO - 3 meq/l 16 BE meq/l - 7 29-3-2015 W Vincken - UZ Brussel - VUB 96

Interpretation of ABG : example 8 P a O 2 mmhg 100 Normoxemia S a O 2 % 97 Normal P A-a O 2 mmhg 12 Normal P a CO 2 mmhg 30 Hypocapnia ph 7.37 Minimal acidosis HCO 3 - meq/l 16 Reduced BE meq/l - 7 Negative 29-3-2015 W Vincken - UZ Brussel - VUB 97

Interpretation of ABG : example 8 P a O 2 mmhg 100 Normoxemia S a O 2 % 97 Normal P A-a O 2 mmhg 12 Normal P a CO 2 mmhg 30 Hypocapnia Compensatory Respiratory ph alkalosis 7.37 Minimal acidosis Acidosis HCO 3 - meq/l 16 Reduced Metabolic BE meq/l - 7 Negative 29-3-2015 W Vincken - UZ Brussel - VUB 98

Interpretation of ABG : example 9 P a O 2 mmhg 95 S a O 2 % 96 P A-a O 2 mmhg calculate P a CO 2 mmhg 40 ph 7.50 HCO - 3 meq/l 32 BE meq/l + 8 29-3-2015 W Vincken - UZ Brussel - VUB 99

Interpretation of ABG : example 9 P a O 2 mmhg 95 S a O 2 % 96 P A-a O 2 mmhg 149 40x1.25 95 = 4 P a CO 2 mmhg 40 ph 7.50 HCO - 3 meq/l 32 BE meq/l + 8 29-3-2015 W Vincken - UZ Brussel - VUB 100

Interpretation of ABG : example 9 P a O 2 mmhg 95 Normoxemia S a O 2 % 96 Normal P A-a O 2 mmhg 4 Normal P a CO 2 mmhg 40 ph 7.50 HCO - 3 meq/l 32 BE meq/l + 8 29-3-2015 W Vincken - UZ Brussel - VUB 101

Interpretation of ABG : example 9 P a O 2 mmhg 95 Normoxemia S a O 2 % 96 Normal P A-a O 2 mmhg 4 Normal P a CO 2 mmhg 40 Normocapnia ph 7.50 Alkalosis HCO 3 - meq/l 32 Increased BE meq/l + 8 Positive 29-3-2015 W Vincken - UZ Brussel - VUB 102

Interpretation of ABG : example 9 P a O 2 mmhg 95 Normoxemia S a O 2 % 96 Normal P A-a O 2 mmhg 4 Normal P a CO 2 mmhg 40 Normocapnia Acute ph 7.50 Alkalosis Alkalosis HCO - 3 meq/l 32 Increased Metabolic BE meq/l + 8 Positive 29-3-2015 W Vincken - UZ Brussel - VUB 103

Interpretation of ABG : example 10 P a O 2 mmhg 83 S a O 2 % 91 P A-a O 2 mmhg calculate P a CO 2 mmhg 50 ph 7.43 HCO - 3 meq/l 32 BE meq/l + 8 29-3-2015 W Vincken - UZ Brussel - VUB 104

Interpretation of ABG : example 10 P a O 2 mmhg 83 S a O 2 % 91 P A-a O 2 mmhg 149 50x1.25 83 = 4 P a CO 2 mmhg 50 ph 7.43 HCO - 3 meq/l 32 BE meq/l + 8 29-3-2015 W Vincken - UZ Brussel - VUB 105

Interpretation of ABG : example 10 P a O 2 mmhg 83 Normoxemia S a O 2 % 91 Borderline P A-a O 2 mmhg 4 Normal P a CO 2 mmhg 50 ph 7.43 HCO - 3 meq/l 32 BE meq/l + 8 29-3-2015 W Vincken - UZ Brussel - VUB 106

Interpretation of ABG : example 10 P a O 2 mmhg 83 Normoxemia S a O 2 % 91 Borderline P A-a O 2 mmhg 4 Normal P a CO 2 mmhg 50 Hypercapnia ph 7.43 Minimal alkalosis HCO 3 - meq/l 32 Increased BE meq/l + 8 Positive 29-3-2015 W Vincken - UZ Brussel - VUB 107

Interpretation of ABG : example 10 P a O 2 mmhg 83 Normoxemia S a O 2 % 91 Borderline P A-a O 2 mmhg 4 Normal P a CO 2 mmhg 50 Hypercapnia Compensatory Respiratory ph acidosis 7.43 Minimal alkalosis Alkalosis HCO 3 - meq/l 32 Increased Metabolic BE meq/l + 8 Positive 29-3-2015 W Vincken - UZ Brussel - VUB 108

Definition of Respiratory Failure Abnormal Arterial Blood Gases Hypoxemia with P a O 2 < 60 mmhg without or with Hypercapnia with P a CO 2 > 50 mmhg Without ABGs No Diagnosis of RF 29-3-2015 W Vincken - UZ Brussel - VUB 109

Classification of Respiratory Failure According to type of onset/duration Acute Respiratory Failure Chronic Respiratory Failure Acute on Chronic Respiratory Failure 29-3-2015 W Vincken - UZ Brussel - VUB 110

Classification of Respiratory Failure According to type of ABG abnormality Respiratory Failure Type I Hypoxemia with (due to) increased P A-a O 2 Normocapnia or hypocapnia Respiratory Failure Type II Hypoxemia with (due to) hypercapnia Normal P A-a O 2 29-3-2015 W Vincken - UZ Brussel - VUB 111

Classification of Respiratory Failure According to type of ABG abnormality Type I RF ~ Oxygenation Failure Failure of the lung as a gas exchanger (O 2 and CO 2 ) Increased P A-a O 2 Type II RF ~ Ventilatory Failure Failure of the respiratory system as an air pump Normal P A-a O 2 Mixed Failure 29-3-2015 W Vincken - UZ Brussel - VUB 112

Oxygenation Failure Reduced P a O 2 (hypoxemia) Increased P A-a O 2 Reduced P a CO 2 (hypocapnia) Increased ph (respiratory alkalosis) If persistent: compensatory metabolic acidosis (renal bicarbonate excretion) Acutely, Δ HCO 3- = 0.2 x Δ P a CO 2 Chronically, Δ HCO 3- = 0.5 x Δ P a CO 2 29-3-2015 W Vincken - UZ Brussel - VUB 113

Oxygenation Failure Abnormal Chest X-Ray Diffuse pulmonary diseases Localised pulmonary diseases Normal Chest X-Ray Anatomic R>L shunts Asthma (except for hyperinflation) Pulmonary embolism/vascular disease 29-3-2015 W Vincken - UZ Brussel - VUB 114

Ventilatory Failure Increased P a CO 2 (hypercapnia) Reduced ph (respiratory acidosis) Reduced P a O 2 (pro rata hypoxemia) Normal P A-a O 2 If persistent: compensatory metabolic alkalosis (renal bicarbonate retention) Acutely, Δ HCO 3- = 0.1 x Δ P a CO 2 Chronically, Δ HCO 3- = 0.35 x Δ P a CO 2 29-3-2015 W Vincken - UZ Brussel - VUB 115

Classification of Respiratory Failure Type I Type II Acute Hypoxemia with Hypoxemia with Chronic increased P A-a O 2 Hypocapnia Respiratory alkalosis Hypoxemia Hypocapnia Compensated respiratory alkalosis Due to HCO 3- excretion and metabolic acidosis normal P A-a O 2 Hypercapnia Respiratory acidosis Hypoxemia Hypercapnia Compensated respiratory acidosis Due to HCO 3- retention and metabolic alkalosis 29-3-2015 W Vincken - UZ Brussel - VUB 116

Classification of Respiratory Failure Acute P a O 2 P A-a O 2 P a CO 2 ph Chronic P a O 2 P A-a O 2 P a CO 2 ph HCO 3 - BE Type I Low High Low High Low High Low High normal Low negative Type II Low Normal High Low Low Normal High Low normal High positive 29-3-2015 W Vincken - UZ Brussel - VUB 117

Thank you for listening Hope you learned something, or at least enjoyed it Prof. Dr. W. Vincken Head Respiratory Division UZ Brussel, VUB 29-3-2015 W Vincken - UZ Brussel - VUB 118