BGA interpretation-Chest in selected location.pptx

BGA analysis

1. Blood Gas Analysis Interpretation Nur Rahmi Ananda Pulmonology Division, Internal Medicine Department, Faculty of Medicine, Public Health and Nursing UGM

2. Blood Gas Analysis To assess: Disorder of Gas Exchange Acid-Base Balance

3. Pulmonary Gas Exchange : the basics P O 2 : partial pressure of O 2 PaO 2 : partial pressure of O 2 in arterial blood PCO 2 : partial pressure of CO 2 PaCO 2 : partial pressure of CO 2 in arterial blood Gases move from the areas of higher partial pressure to lower partial pressure

4. Respiratory System: Gas Exchange and Regulation of Breathing, http:// droualb.faculty.mjc.edu /Course%20Materials/Physiology%20101/Chapter%20Notes/Fall%202011/chapter_17%20Fall%202011.htm

5. Hennessey I & Japp AG, 2007. Arterial Blood Gases Made Easy. Churchill Livingstone, Elsevier PaCO2 is controlled by ventilation and the level of ventilation is adjusted to maintain PaCO2 within tight limits

6. Haemoglobin Oxygen Saturation The amount of O 2 in blood depends on 2 factors : Hb concentration : this determines how much O 2 blood has the capacity to carry Saturation of Hb with O 2 ( SO 2 ) : this is the percentage of available binding sites on Hb contain an O 2 molecules (how much the carrying capacity is being used)

7. Hb-O 2 saturation Hennessey I & Japp AG, 2007. Arterial Blood Gases Made Easy. Churchill Livingstone, Elsevier

8. PO 2 is not the amount O 2 in blood but is the driving force for saturating Hb with O 2 The higher PO 2 , the higher SO 2 , but the curve is not linear When Hb approaches maximal O 2 saturation, further increases in PO 2 do not significantly increase blood O 2 content

9. 3 major factors that dictate the PaO 2 : Alveolar ventilation - impaired ventilation : PaO 2 to fall, and PaCO 2 to rise Matching of ventilation with perfusion (V/Q) - V/Q missmatch allows poorly oxygenated blood to re enter the arterial circulations  lowering PaO2 and SaO2 - V/Q missmatch do not lead to increase PaCO2 3. Concentration of O2 in inspired air (FiO 2 )

10. Range of ventilation-to-perfusion (V/Q) relationships. https:// nursekey.com /nursing-management-respiratory-failure-and-acute-respiratory-distress-syndrome/

11. Hennessey I & Japp AG, 2007. Arterial Blood Gases Made Easy. Churchill Livingstone, Elsevier

12. Disorder of Gas Exchange Hypoxia : any state in which tissues receive an inadequate supply of O2 to support normal aerobic metabolism Hypoxemia : any state in which the O 2 content of arterial blood is reduced Impaired oxygenation : reduced transfer of O 2 from lung to bloodstream (low PaO 2 ; PaO 2 < 80 mmHg) Respiratory Impairment - Type 1 - Type 2

13. Type 1 Respiratory Impairment Low PaO2 with normal or low PaCO2 PaCO2 often low due to compensatory hyperventilation V/Q mismatch usually responsible Pulse oximetry can be used as an alternative to repeated ABG sampling to monitor progress Common causes : pneumonia, pulmonary embolism, pneumothorax, pulmonary oedema , acute asthma, acute respiratory distress syndrome, fibrosing alveolitis , chronic obstructive pulmonary disease

14. Severity of type 1 respitarory impairment Hennessey I & Japp AG, 2007. Arterial Blood Gases Made Easy. Churchill Livingstone, Elsevier

15. Type 2 Respiratory Impairment High PaCO 2 (hypercapnia) and is due to inadequate alveolar ventilation PaO 2 is usually low, but may be normal if the patient is on supplemental O 2 Supplemental O2 improves hypoxemia, but not hypercapnia Treatment also include measures to improve ventilation (e.g. reversal of sedation, relief airway obstruction, assisted ventilation) Cannot replaced by pulse oximetry to monitor progress

16. Type 2 Respiratory Impairment Common cause COPD, exhaustion, flail chest injury, kyphoskoliosis , opiate/benzodiazepine toxicity, inhaled foreign body, neuromuscular disorder, obstructive sleep apneu Clinical Signs of hypercapnia Confusion, flapping tremor, warm extremities, drowsiness, bounding pulse, headache

17. Hennessey I & Japp AG, 2007. Arterial Blood Gases Made Easy. Churchill Livingstone, Elsevier

18. Pocket ICU Management, Interpretation of Arterial Blood Gases, https :// anesth.unboundmedicine.com /anesthesia/view / PaO2/FiO2 The PaO2 rises with increasing FiO2. Inadequate or decreased oxygen exchange decreases the ratio. Normal PaO2/FiO2 is >400 mmHg Approximate PaO2 by multiplying FiO2 by 5 ( eg , FiO2 = 21%, then PaO2 = 100 mmHg ) A-a Gradient PaO2 is dependent on alveolar oxygen (PAO2), which is influenced by the FiO2, barometric pressure (high altitude), PaCO2 increase (respiratory depression), and the gradient between alveolar and arterial oxygen tension, which can be increased by ventilation and perfusion mismatch. A-a = (Pb-PH2O) x FiO2 – (PaCO2/0.8) Normal is < 10 mmHg

19. 2. Acid Base Balance: The basics Hennessey I & Japp AG, 2007. Arterial Blood Gases Made Easy. Churchill Livingstone, Elsevier

20. Equations that is crucial to understand acid-base balance: H 2 O + CO 2 ←→ H 2 CO 3 ←→ H + + HCO3 -

21. Compensation

22. Disorder pH Primary problem Compensation Metabolic acidosis ↓ ↓ in HCO 3 - ↓ in PaCO 2 Metabolic alkalosis ↑ ↑ in HCO 3 - ↑ in PaCO 2 Respiratory acidosis ↓ ↑ in PaCO 2 ↑ in [HCO 3 -] Respiratory alkalosis ↑ ↓ in PaCO 2 ↓ in [HCO 3 -]

23. Rule of compensation Respiratory acidosis   Acute : [HCO 3 - ] increase by 1 mEq /L for every 10 mmHg increase in paCO 2  above 40. Chronic : [HCO 3 - ] increase by 3.5 mEq /L for every 10 mmHg increase in paCO 2  above 40. Respiratory alkalosis   Acute : [HCO 3 - ] decrease by 2 mEq /L for every 10 mmHg decrease in paCO 2  below 40. Chronic : [HCO 3 - ] decrease by 5 mEq /L for every 10 mmHg decrease in paCO 2  below 40.

24. Compensated metabolic asidosis expected paCO 2  is calculated as : paCO 2  = [1.5 × HCO 3 + 8] ± 2

25. If metabolic asidosis , assess the anion gap Anion Gap Anion gap = ( Na +  + K + ) - [ Cl -  + HCO 3 - ] Normal : 10-18 mmol /l

26. SLUM DOG is useful mnemonic for clues to a high anion gap . S alicylate poisoning; L actic acidosis (hypoxia, hypoperfusion ); U raemia (renal failure); M edication ( antidiabetics — metformin ; antimicrobials — linezolid, anti-seizure opiramate ); D iabetic or alcoholic ketoacidosis; O rganic acids (metabolic disease in children, pyroglutamic acidemia G as and heavy metal poisoning (CO, CO2, cyanide , iron, arsenic). Arterial Blood Gases, Proceedings of Singapore Healthcare  Volume 20  Number 3  2011

27. ABC is useful mnemonic for clues to a low anion gap. A lbumin ( haemorrhage , nephrotic syndrome, intestinal obstruction, liver cirrhosis, multiple myeloma); B icarbonate ; C hloride. Arterial Blood Gases, Proceedings of Singapore Healthcare  Volume 20  Number 3  2011

28. GRIM is a useful mnemonic for providing clues to a normal anion gap . G astrointestinal (chronic diarrhoea , uretero -colonic and pancreatic fistula); R enal tubular disease (proximal and distal tubular acidosis); I atrogenic (calcium chloride, total parenteral nutrition ); M ineralocorticoid deficiency (Addison’s disease ) Arterial Blood Gases, Proceedings of Singapore Healthcare  Volume 20  Number 3  2011

29. Rapid Interpretation : Step by step Assess the internal consistency of the values using the Henderseon-Hasselbach equation : [ H+] =  24(PaCO 2 )            [ HCO 3 -] If the pH and the [H+] are inconsistent, the ABG is probably not valid.

30. PH Approximate [H+] ( mmol /L) 7.00 100 7.05 89 7.10 79 7.15 71 7.20 63 7.25 56 7.30 50 7.35 45 7.40 40 7.45 35 7.50 32 7.55 28 7.60 25 7.65 22

31. 2. Assess pulmonary exchange and acid base status independently !!!

32. Assessing pulmonary Gas exchange Hennessey I & Japp AG, 2007. Arterial Blood Gases Made Easy. Churchill Livingstone, Elsevier

33. Acid base disorder Hennessey I & Japp AG, 2007. Arterial Blood Gases Made Easy. Churchill Livingstone, Elsevier

34. Pocket Medicine, 4 th edition

35. Exercises 1 A 25 year old man, with no significant past medical history, presents to the emergency department with a 2 day history of fever, productive cough and worsening breathlessness. Examination : He is hot and flushed with temperature of 39,3 oC. He does not appear distressed but is using accessory muscles of respiration. There is diminished chest expansion on the left with dullness to percussion, bronchial breathing and coarse crackles in the left lower zone posteriorly. Pulse : 104x/min BP : 110/70 mmHg : 28 x/min SaO2 (room air) : 89%

36. Arterial blood gas On room air pH 7.5 PCO2 28.1 PO2 57.8 HCO3 23.9 BE -0.5 SPO2 88.7 %

37. Exercise 2 A 78 year old male on a surgical ward is found unresponsive, having returned, a few hours previously, from a complicated open cholecystectomy. Review of his chart reveals he has received three 10 mg injections of morphine since returning to the ward, in addition to the morphine delivered by his patient-controlled analgesia device. The patient is unresponsive with shallow respirations and bilateral pinpoint pupils. Pulse 90 beat/min BP 98/64 mmHg RR 5 breath/min SaO2 99%

38. ABG: on 28% O2 pH 7.18 H + 65.4 PCO2 62 mmHg PO2 87 mmHg HCO3 22.4 BE -1.5 SPO2 99%

39. Exercise 3 A 35 year old woman with type 1 diabetes is brought to the emergency department by ambulance after being found in her house severely unwell. Following a discussion with her husband it emerges she has not been eating for the past few days due to vomiting illness and, a precaution has also been omitting her insulin. On examination she appears drowsy and peripherally shut down, with very dry mucous membranes. Her breath smells of acetone and her respirations are deep and sighing. Pulse 130 beat/min RR 26 beat/min BP 110/60 mmHg

40. pH 7.05 on 10 L O2 by mask PCO2 11 mmHg PO2 187 HCO3 6.0 BE -25.2 SPO2 99.8 %

41. Thank you