This review article was presented in the 7th International joint cardiovascular congress held on Feb 28-29, 2019, in Convention Center, Shahid Rejaee Heart Hospital, Tehran, Iran

1. ABG
INTERPRETATION
Reza Nejat, M.D.,
Anesthesiologist, FCCM,
Former Assistant Professor, SBMU
Bazarganan Hospital

2. ABG INTERPRETATION
 Recommendations for
Physiotherapy in the ICU
 Acute lobar atelectasis ♣♣
 Positioning in severe ARDS
 Side lying improves 0xygenation
 Continuous rotational therapy
 Facilitating weaning:
 decreases length of stay in the ICU or
hospital, and reduces mortality or
morbidity**
 Preventing loss of joint range or soft-
tissue length**

3. ABG INTERPRETATION
The physiotherapy treatment:
 prevents and reduces potential
pulmonary complications:
Hypoventilation,
Hypoxemia,
Infection,
Restore muscular and pulmonary
function as fast as possible.

4. ABG INTERPRETATION
 The side effects of
physiotherapy:
 Metabolic
 Hemodynamic
 ICP↑

5. ABG INTERPRETATION
Physiotherapy should be offered:
 to a variety of medical
respiratory conditions:
 Management of breathlessness
and symptom control,
 Mobility function improvement
or maintenance,
 Airway clearance
 Cough enhancement or support.

6. ABG INTERPRETATION
 Endotracheal suctioning:
 a mean 56% increase inVO2 from
baseline.
 Suctioning in the gravity-assisted
drainage position:
 Increases in the metabolic stress
 Requires an increased effort to cough,
given the altered diaphragmatic and
abdominal muscle position.

7. ABG INTERPRETATION
 What should be done during
physiotherapy:
 Monitor hemodynamic status
 Sedation before physiotherapy
 Pre-oxygenation, sedation, and
reassurance before suction
 Monitor ICP and CPP*

8. ABG INTERPRETATION
 Contra-indications of CPT:
 Pulmonary edema,
 congestive heart failure,
 Distended abdomen,
 pregnancy, obesity, and ascites,
 Severe surgical emphysema,
 Neuromuscular disease
 Aneurysm or decrease in
circulation of main blood vessels

9. ABG INTERPRETATION
 Contra-indications of CPT:
 Untreated tension pneumothorax
 Unstable cardiovascular disorders
 Dyspnea, orthopnea
 Undiagnosed chest pain.
 Chronic obstructive pulmonary
disease with cor pulmonale,
orthopnea, dyspnea on exertion
 Active cases of tuberculosis

10. ABG INTERPRETATION
 Accurate and timely
interpretation of ABG and an
acid–base disorder can be
lifesaving,
 The establishment of a
correct diagnosis may be
challenging

11. ABG INTERPRETATION
 ABG interpretation:
 Assessment of Blood
Oxygenation Status
 Assessment of Acid-Base
Status

12. ABG INTERPRETATION
 Assessment of ABG
1. careful clinical evaluation
2. assess oxygenation
3. determine pH (Acidosis vs
Alkalosis)
4. consider the respiratory
component
5. consider the metabolic
component
6. consider the possibility of a
mixed acid–base disturbance

13. ABG INTERPRETATION
 signs and symptoms
 vital signs (which may indicate shock or sepsis),
 neurologic state
 signs of infection (e.g., fever),
 pulmonary status (respiratory rate, Kussmaul
respiration, cyanosis, clubbing of the fingers)
 gastrointestinal symptoms (vomiting and
diarrhea)
 pregnancy,
 diabetes,
 heart, lung, liver, and kidney disease,
 medications (e.g., laxatives, diuretics,
topiramate, or metformin)

14. ABG INTERPRETATION
 Assessment of ABG
1. careful clinical evaluation
2. determine the primary acid–base disorder
3. consider the metabolic component
4. consider the possibility of a mixed metabolic
acid–base disturbance
5. note the serum osmolal gap in any patient with
an unexplained high anion-gap acidosis
6. evaluate the respiratory component
7. determine the cause of the identified processes

15. ABG INTERPRETATION
 Respiratory insufficiency:
 Low FiO2
 Hypoventilation
 𝑷𝒂𝑪𝑶𝟐 = 𝑽𝑪𝑶𝟐/𝑽𝑨, 𝑽𝑪𝑶𝟐
 V/Q mismatch
 Shunt
 (𝑷 𝑨 𝑶 𝟐 − 𝑷 𝒂 𝑶 𝟐)/𝟐𝟎
 Diffusion
 DLCO

16. ABG INTERPRETATION
 𝑷 𝒂 𝑶 𝟐 < 𝟓𝟓 𝒎𝒎𝑯𝒈
 Memory defect, impaired judgement
 𝑷 𝒂 𝑶 𝟐 < 𝟒𝟎 𝒎𝒎𝑯𝒈
 Tissue damage
 𝑷 𝒂 𝑶 𝟐 < 𝟑𝟎 𝒎𝒎𝑯𝒈
 Unconsciousness
 𝑷 𝒂 𝑶 𝟐 < 𝟐𝟎 𝒎𝒎𝑯𝒈
 Death

17. ABG INTERPRETATION
Clinical features of
Hypoxemia Hypercapnia
Cyanosis Flapping tremor of hands
Tachypnea Tachypnea
Tachycardia→arrhythmia→bradycardia Tachycardia
Peripheral vasoconstriction Peripheral vasodilation
warm hands/ headache
Restlessness→confusion→coma drowsiness→hallucination→coma
Sweating

18. ABG INTERPRETATION
 𝑷 𝑨 𝑶 𝟐 = 𝑭𝒊𝑶𝟐 × (𝑩𝑷– 𝑷𝑯 𝟐 𝑶)– (𝑷 𝒂 𝑪𝑶 𝟐/𝑹)
 𝑷 𝑨 𝑶 𝟐 = 𝑭𝒊𝑶𝟐 × (𝑩𝑷– 𝑷𝑯 𝟐 𝑶)– 𝟏. 𝟐𝟓𝑷 𝒂 𝑪𝑶 𝟐
 BP=760mmHg, FiO2=?, 𝑷𝑯 𝟐 𝑶=47mmHg , R=0.8
 If FiO2=21%
 𝑷 𝑨 𝑶 𝟐 = 𝟏𝟎𝟓 − 𝟏. 𝟐𝟓𝑷 𝒂 𝑪𝑶 𝟐

19. ABG INTERPRETATION
 In normal subjects:
 𝑷 𝒂 𝑶 𝟐 = 𝑭𝒊 𝑶 𝟐 × 𝟓
 120 RULE:
 𝑷 𝒂 𝑶 𝟐 + 𝑷 𝒂 𝑪𝑶 𝟐=𝟏𝟒𝟎 ± 𝟏𝟎
 <120 venous admixture
 PaO2/FiO2
 Normal 100/0.21=500
 200< PaO2/FiO2<300 MILD ARDS
 100< PaO2/FiO2<200 MODERATE ARDS
 PaO2/FiO2<100 SEVERE ARDS
 (on PEEP=5cmH2O)

20. ABG INTERPRETATION
(Alveolar-Arterial)O2= 𝑷 𝑨 𝑶 𝟐 − 𝑷 𝒂 𝑶 𝟐:
 Young 5-10mmHg
 Old 15-20mmHg
 Increases with increase in FiO2
For every decade, the alveolar–arterial
difference increases by 2 mm Hg
 𝑷 𝑨 𝑶 𝟐 − 𝑷 𝒂 𝑶 𝟐 = (𝒂𝒈𝒆/𝟒) + 𝟒
 𝑷 𝑨 𝑶 𝟐 − 𝑷 𝒂 𝑶 𝟐 = 𝟐. 𝟓 + (𝟎. 𝟐𝟏 × 𝒂𝒈𝒆 𝒊𝒏 𝒚𝒆𝒂𝒓𝒔)
 𝑷 𝒂 𝑶 𝟐 = 𝟏𝟎𝟎 − (𝒂𝒈𝒆 × 𝟎. 𝟐𝟓)

21. ABG INTERPRETATION
 SpO2/FiO2=235
 PaO2/FiO2=200
 SpO2/FiO2=315
 PaO2/FiO2=300

22. ABG INTERPRETATION
 Assessment of ABG
1. careful clinical evaluation
2. determine the primary acid–base disorder
3. consider the metabolic component
4. consider the possibility of a mixed metabolic
acid–base disturbance
5. note the serum osmolal gap in any patient with
an unexplained high anion-gap acidosis
6. evaluate the respiratory component
7. determine the cause of the identified processes

23. ABG INTERPRETATION
 Based on the iso-hydric principle,
this system characterizes acids as
hydrogen-ion donors and bases
as hydrogen-ion acceptors
 The hydrogen-ion concentration
is tightly regulated because
changes in hydrogen ions alter
virtually all protein and
membrane functions

24. ABG INTERPRETATION
Acidosis
 the hydrogen-ion concentration ⇈
Alkalosis
 the hydrogen-ion concentration ⇊

25. ABG INTERPRETATION
 Normal plasma concentration of
hydrogen ions
 very low 40 nmol/L
 pH
 the negative logarithm of the hydrogen-
ion concentration, −log [𝑯+
]
 used in clinical medicine to indicate acid–
base status.
 “acidemia”
 Plasma pH is abnormally low (acidic)
 “alkalemia”
 Plasma pH is abnormally high (alkaline)

26. ABG INTERPRETATION
 the Henderson–Hasselbalch equation
 (𝑯 𝟐 𝑶 + 𝑪𝑶 𝟐 ↔ 𝑯 𝟐 𝑪𝑶 𝟑 ↔ 𝑯+ + 𝑯𝑪𝑶 𝟑
−
) →→ 𝒌 =
𝑯+ [𝑯𝑪𝑶 𝟑
−
]
𝑯 𝟐 𝑪𝑶 𝟑
 𝒑𝑯 = 𝒑𝑲 + log𝟏𝟎 ([𝑯𝑪𝑶 𝟑
−
] / [𝟎. 𝟎𝟑 × (𝑷𝒂𝑪𝑶 𝟐)])
 𝑯𝑪𝑶 𝟑
−
= 𝒑𝒓𝒐𝒕𝒐𝒏 𝒂𝒄𝒄𝒆𝒑𝒕𝒐𝒓 = 𝑩𝑨𝑺𝑬 (𝑲𝑰𝑫𝑵𝑬𝒀)
 𝑪𝑶 𝟐 = 𝒑𝒓𝒐𝒕𝒐𝒏 𝒅𝒐𝒏𝒐𝒓 = 𝑨𝑪𝑰𝑫 (𝑳𝑼𝑵𝑮)
 𝒑𝑯 = 𝒑𝑲 + log𝟏𝟎 ([𝑩𝑨𝑺𝑬] / [𝑨𝑪𝑰𝑫])
 𝒑𝑯 = 𝒑𝑲 + log𝟏𝟎 ([𝒌𝒊𝒅𝒏𝒆𝒚] / [𝒍𝒖𝒏𝒈])

27. ABG INTERPRETATION
 𝒑𝑯 = 𝒑𝑲 + log𝟏𝟎 ([𝒌𝒊𝒅𝒏𝒆𝒚] / [𝒍𝒖𝒏𝒈])
 𝒑𝑯 = 𝒑𝑲 + log𝟏𝟎 ([𝒎𝒆𝒕] / [𝒓𝒆𝒔𝒑])
ACIDOSIS:
 Respiratory
 Metabolic
ALKALOSIS:
 Respiratory
 Metabolic

28. ABG INTERPRETATION
 Met Acidosis:
  pH and  𝑯𝑪𝑶 𝟑
−
 Met Alkalosis:
  pH and  𝑯𝑪𝑶 𝟑
−
 Resp Acidosis:
  pH and  𝑷𝒂𝑪𝑶 𝟐
 Resp Alkalosis:
  pH and  𝑷𝒂𝑪𝑶 𝟐

29. ABG INTERPRETATION
 Metabolic acidosis
 pH <7.35 and [𝑯𝑪𝑶 𝟑
−
] 24 mmol/liter
 Secondary (respiratory) response:
𝑷𝒂𝑪𝑶 𝟐 = 𝟏. 𝟓 × [𝑯𝑪𝑶 𝟑
−
] + 𝟖 ± 𝟐 𝒎𝒎 𝑯𝒈
or
𝑷𝒂𝑪𝑶 𝟐 = [𝑯𝑪𝑶 𝟑
−
] + 𝟏𝟓 𝒎𝒎 𝑯𝒈
 Complete secondary adaptive response
within 12–24 hr

30. ABG INTERPRETATION
 Metabolic alkalosis
 𝒑𝑯 > 𝟕. 𝟒𝟓 and [𝑯𝑪𝑶 𝟑
−
] >24 mmol/liter
 Secondary (respiratory) response:
𝑷𝒂𝑪𝑶 𝟐 = 𝟎. 𝟕 × ([𝑯𝑪𝑶 𝟑
−
] − 𝟐𝟒) +
𝟒𝟎 ± 𝟐 𝒎𝒎 𝑯𝒈
or
𝑷𝒂𝑪𝑶 𝟐 = [𝑯𝑪𝑶 𝟑
−
] + 𝟏𝟓 𝒎𝒎 𝑯𝒈
or
𝑷𝒂𝑪𝑶 𝟐 = 𝟎. 𝟕 × [𝑯𝑪𝑶 𝟑
−
] + 𝟐𝟎 𝒎𝒎 𝑯𝒈
 Complete secondary adaptive response
within 24–36 hr

31. ABG INTERPRETATION
 Respiratory acidosis
pH <7.35 and 𝑷𝒂𝑪𝑶 𝟐>40 mm Hg
Secondary (metabolic) response
Acute:
𝑷𝒂𝑪𝑶 𝟐 10 mm Hg = [𝑯𝑪𝑶 𝟑
−
]  1mmol/liter
Chronic:
𝑷𝒂𝑪𝑶 𝟐 10 mm Hg = [𝑯𝑪𝑶 𝟑
−
]  2-5mmol/liter
Complete secondary adaptive response
within 2–5 days

32. ABG INTERPRETATION
 Respiratory alkalosis
pH >7.45 and 𝑷𝒂𝑪𝑶 𝟐<40 mm Hg
Secondary (metabolic) response
Acute:
𝑷𝒂𝑪𝑶 𝟐 10 mm Hg = [𝑯𝑪𝑶 𝟑
−
]  1mmol/liter
Chronic:
𝑷𝒂𝑪𝑶 𝟐 10 mm Hg = [𝑯𝑪𝑶 𝟑
−
]  2-4mmol/liter
Complete secondary adaptive response
within 2–5 days

33. ABG INTERPRETATION
 Assessment of ABG
1. careful clinical evaluation
2. determine the primary acid–base disorder
3. consider the metabolic component
4. consider the possibility of a mixed metabolic
acid–base disturbance
5. note the serum osmolal gap in any patient with
an unexplained high anion-gap acidosis
6. evaluate the respiratory component
7. determine the cause of the identified processes

34. ABG INTERPRETATION

35. ABG INTERPRETATION
 Calculation of the anion gap:
{ 𝑵𝒂 + + 𝑲 + + 𝑪𝒂 𝟐+
+ 𝑴𝒈 𝟐+
+
𝑯+ } + 𝒖𝒏𝒎𝒆𝒂𝒔𝒖𝒓𝒆𝒅 𝒄𝒂𝒕𝒊𝒐𝒏𝒔 𝑼𝑪 =
𝑪𝒍−
+ 𝑯𝑪𝑶 𝟑
−
+ 𝑪𝑶 𝟑
𝟐−
+ 𝑶𝑯−
+
𝒂𝒍𝒃𝒖𝒎𝒊𝒏 + 𝒑𝒉𝒐𝒔𝒑𝒉𝒂𝒕𝒆 + 𝒔𝒖𝒍𝒇𝒂𝒕𝒆 +
𝒍𝒂𝒄𝒕𝒂𝒕𝒆+ 𝒖𝒏𝒎𝒆𝒂𝒔𝒖𝒓𝒆𝒅 𝒂𝒏𝒊𝒐𝒏 (𝑼𝑨)
𝑨𝒏𝒊𝒐𝒏 𝑮𝒂𝒑 = 𝑼𝑨 − 𝑼𝑪
= [𝑵𝒂+] − ([𝑪𝒍−] + [𝑯𝑪𝑶 𝟑
−
])
= 12-16meq/l (depends on K)

36. ABG INTERPRETATION
 High anion-gap metabolic acidosis
GOLD MARRK
1. Glycols [ethylene and propylene],
2. 5-oxoproline [pyroglutamic acid],
3. l-lactate,
4. d-lactate,
5. methanol,
6. aspirin,
7. renal failure,
8. rhabdomyolysis,
9. ketoacidosis

37. ABG INTERPRETATION

38. ABG INTERPRETATION
Normal Anion Gap Acidosis:
GI or Urinary 𝑯𝑪𝑶 𝟑
−
loss
Urinary Anion GAP:
([𝑵𝒂+
] + [𝑲+
]– [𝑪𝒍−
])
neGUTive GI (diarrhea), PRTA
Positive in RF, DRTA, Hypoaldosteronism

39. ABG INTERPRETATION
Metabolic Alkalosis:
Gastric fluid loss
Diuretic
Urinary Chloride:
<25mmol/L
>40mmol/L (hypo K, Hyper Aldos)

40. ABG INTERPRETATION
 www.rezanejat.com

41. ABG INTERPRETATION
 A case report:
82 year-old male with diarrhea
BP: 87/45 mmHg, Chest Pain
past medical hx:
coronary artery disease,
hypertension,
COPD,
Type 2 DM,
chronic kidney disease,

42. ABG INTERPRETATION
 A case report:
After being admitted in ER he
vomited and went through cardiac
arrest; BLS and ACLS were done.
Epinephrine, Bicarbonate, Calcium
ROSC after CPR

43. ABG INTERPRETATION
 A case report:
LaboratoryTest Results:
Before CPR After CPR
𝑁𝑎+
140 149
𝐾+
6.3 5.2
𝐶𝑙− 101 97
𝐻𝐶𝑂3
−
22 𝑁𝐴
𝑝𝐻 7.21 7.15
𝑃𝑎 𝑂2 58 120
𝑃𝑎 𝐶𝑂2 46 36

44. ABG INTERPRETATION
 A case report:
Interpretation:
𝑷 𝒂 𝑶 𝟐 = 𝟏𝟎𝟎 − (𝒂𝒈𝒆 × 𝟎. 𝟐𝟓)
𝑷 𝒂 𝑶 𝟐 = 𝟏𝟎𝟎 − (𝟖𝟐 × 𝟎. 𝟐𝟓)
𝑷 𝒂 𝑶 𝟐 = 𝟏𝟎𝟎 − 𝟏𝟖 = 𝟖𝟐 𝒎𝒎𝑯𝒈

45. ABG INTERPRETATION
 A case report:
Interpretation:
𝑷 𝒂 𝑶 𝟐 = 𝟏𝟎𝟎 − (𝒂𝒈𝒆 × 𝟎. 𝟐𝟓)
𝑷 𝒂 𝑶 𝟐 = 𝟏𝟎𝟎 − (𝟖𝟐 × 𝟎. 𝟐𝟓)
𝑷 𝒂 𝑶 𝟐 = 𝟏𝟎𝟎 − 𝟏𝟖 = 𝟖𝟐 𝒎𝒎𝑯𝒈

46. ABG INTERPRETATION
 A case report:
Interpretation:
 Delta gap = (∆AG) - (∆𝐻𝐶𝑂3
−
)
 Delta gap = = [𝑵𝒂+
] − ([𝑪𝒍−
] + [𝑯𝑪𝑶 𝟑
−
]) − 𝟏𝟐 − (𝟐𝟒 − ([𝑯𝑪𝑶 𝟑
−
])
 Delta gap = = [𝑵𝒂+
] − ([𝑪𝒍−
] + 𝟑𝟔)
 Interpretation of the generated gap:
 -6 = Mixed high and normal anion gap acidosis
 -6 to 6 = Only a high anion gap acidosis exists
 over 6 = Mixed high anion gap acidosis and metabolic alkalosis

47. ABG INTERPRETATION
 A case report:
Interpretation:
Type 2 respiratory insufficiency
Anion gap metabolic acidosis and
metabolic alkalosis

48. ABG INTERPRETATION
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