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Respiratory Failure
and Role of ABGs in ICU
(Presenter: Dr Hasheela T. U. N)
Components of the respiratory system
Gas-exchange (Interface)organ
• Lungs (parenchyma)
• Blood vessels (pulmonary and
bro...
Definition
:- a syndrome in which the respiratory system
fails in one or both of its gas exchange functions
i.e. oxygenati...
Normal value HYPOXEMIA
PaO₂ 80 - 100mmHg ( 11 - ... kPa) < 60mmHg (< 8 kPa) on R.A.
< 80mmHg (<11 kPa) on FiO² > 40%
Norma...
CLASSIFICATION
HYPOXAEMIC (TYPE I)
• Failure of oxygenation
↓
HYPOXEMIA without
HYPERCAPNIA
VENTILATORY (TYPE II)
• Respir...
CLASSIFICATION
HYPOXAEMIC TYPE I
ABG CHANGES:
• PaO₂ ↓
(< 60 mmHg / 8.0 kPa)
• PaCO₂ normal or ↓
(<50 mmHg /6.7 kPa)
• PA-...
Causes
Hypoxaemic (Type I)
• Pneumonia
• ARDS
• Pulmonary fibrosis
• Asthma
• COPD
• Pnemothorax
• PE
• Obesity
• Pulmonar...
Pathophysiology
HYPOXAEMIC TYPE I
• 1. (V/Q) mismatch
• 2. True Shunt
• 3. Diffusion Impairment
• 4. Reduced Inspired Oxyg...
Pathophysiology
• Alveolar-arterial PO₂ gradient (‘A–aDO₂’):
PA-aO₂ = PAO₂ - PaO₂
[Normal range: (< 15-20 mmHg)]
(Also, “A...
Alveolar gas equation variables definitions
Quantity Description Sample value
pAO2
The alveolar partial
pressure of oxygen...
CLINICAL PRESENTATION
RF may be preceded by signs of respiratory distress:
• Tachypnoea (>25/min)
• Breathlessness
• Gaspi...
Pre-terminal Signs
• Bradycardia, dysrhythmias, hypotension
• Bradypnoea or silent chest
• Decreased L.O.C
DIAGNOSTICS
1) VITAL SIGNS AND INSPECTION
(BP, O₂ Sat, RR, T°C, LOC, airway patency)
• Fever, tachycardia, tachypnea → Inf...
DIAGNOSTICS
2) NEUROLOGICAL EXAMINATION
• Depressed mental status (lethargy or coma) → Central drive failure
• Pupillary c...
DIAGNOSTICS
3) Head and Neck
• Stridor, drooling → upper airway obstruction
4) Chest
• Pattern of respiratory muscle contr...
DIAGNOSTICS
Laboratory Testing
1. Arterial Blood Gas (ABG)
ABGs are required very early and should be
obtained as soon as ...
DIAGNOSTICS
Normal values of arterial blood gases
(at R.A., sea level, 37°C)
DIAGNOSTICS
Interpretative remarks:
• PaO₂ < 60mmHg(8kPa) →HYPOXEMIA
• PaCO₂ > 50 mmHg(6.7 kPa) →HYPERCAPNIA
• pH < 7.35 →...
DIAGNOSTICS
Interpretative remarks:
• ↓PaO₂ → TYPE I (Hypoxemic) RF
• ↑PaCO₂, ↓pH →Acute TYPE II (Hypercapnic) RF
• ↑PaCO₂...
DIAGNOSTICS
Interpretative remarks:
• The "50–50 rule" of intubating is OUTDATED!
• Respiratory acidosis (pH<7.20–7.25) is...
DIAGNOSTICS
2. Complete Blood Count (CBC)
• Leukocytosis → infection
• Anemia (dyspnea,↓O₂ transport to tissues, but in is...
DIAGNOSTICS
Imaging and Other Tests
• CXR
• (Pneumonia, atelectasis, pulmonary oedema, evidence of chronic
lung disease, t...
Principles of treatment
• Emergency treatment should follow principles of
cardiopulmonary resuscitation (C-A-B);
• Ensure ...
Principles of treatment (Cont…)
• All patients with acute VF not responding to simple
measures in an emergency room, clini...
Principles of treatment (Cont…)
• Consider non-invasive ventilatory support:
• CPAP: continous positive airway pressure
• ...
Principles of treatment (Cont…)
• DRUGS:
• Respiratory stimulants (eg. Doxapram) (rarely used)
• Antidote for sedative ove...
***************The End***************
THANK YOU!!!
References
1. Hanley M. E., Welsh. H., Current Diagnosis & Treatment in Pulmonary
Medicine,1st ed. Denver, Colorado, Septe...
Respiratory failure   role of abg's in icu
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Respiratory Failure(Type1&2) defined

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Respiratory failure role of abg's in icu

  1. 1. Respiratory Failure and Role of ABGs in ICU (Presenter: Dr Hasheela T. U. N)
  2. 2. Components of the respiratory system Gas-exchange (Interface)organ • Lungs (parenchyma) • Blood vessels (pulmonary and bronchial) Ventilatory pump • Thoracic wall • Respiratory muscles • Brainstem and cortex • Anterior horn cells (S.C.) • Phrenic nerves and other nerves
  3. 3. Definition :- a syndrome in which the respiratory system fails in one or both of its gas exchange functions i.e. oxygenation and/or carbon dioxide elimination, such that the levels of arterial oxygen (PaO₂) and carbon dioxide (PaCO₂) partial pressures cannot be maintained within their normal ranges.
  4. 4. Normal value HYPOXEMIA PaO₂ 80 - 100mmHg ( 11 - ... kPa) < 60mmHg (< 8 kPa) on R.A. < 80mmHg (<11 kPa) on FiO² > 40% Normal value HYPERCAPNIA PaCO₂ 35 - 45mmHg ( … - 6.0 kPa) > 50mmHg (> 6.7 kPa)
  5. 5. CLASSIFICATION HYPOXAEMIC (TYPE I) • Failure of oxygenation ↓ HYPOXEMIA without HYPERCAPNIA VENTILATORY (TYPE II) • Respiratory “PUMP” FAILURE ↓ HYPOXEMIA and HYPERCAPNIA
  6. 6. CLASSIFICATION HYPOXAEMIC TYPE I ABG CHANGES: • PaO₂ ↓ (< 60 mmHg / 8.0 kPa) • PaCO₂ normal or ↓ (<50 mmHg /6.7 kPa) • PA-aO₂ ↑ VENTILATORY TYPE II ABG CHANGES: • PaO₂ ↓ (< 60 mmHg / 8.0 kPa) • PaCO₂ ↑ (> 50 mmHg /6.7 kPa) • PA-aO₂ normal • pH↓ (Acidosis)
  7. 7. Causes Hypoxaemic (Type I) • Pneumonia • ARDS • Pulmonary fibrosis • Asthma • COPD • Pnemothorax • PE • Obesity • Pulmonary Hypertension Hypercapnic (Type II) • COPD / Severe Asthma • Drug Overdose (Opiates benzodiazepines,) • CNS Injury (SCI, CVA) • Primary muscle disorders (Duchenne muscular dystrophy) • Neuromuscular junction disorders (eg. Myasthenia gravis) • Anatomical chest deformities (eg. Kyphoscoliosis, Flail chest) • Obesity Hypo-ventilatory (Pickwickian) syndrome
  8. 8. Pathophysiology HYPOXAEMIC TYPE I • 1. (V/Q) mismatch • 2. True Shunt • 3. Diffusion Impairment • 4. Reduced Inspired Oxygen Concentration ↓ ↑ A-a PO₂ gradient ↓ HYPOXAEMIA VENTILATORY TYPE II 1. Respiratory “PUMP” FAILURE ↓ Inadequate alveolar ventilation ↓ CO₂ Accumulation ↓ HYPERCAPNIA
  9. 9. Pathophysiology • Alveolar-arterial PO₂ gradient (‘A–aDO₂’): PA-aO₂ = PAO₂ - PaO₂ [Normal range: (< 15-20 mmHg)] (Also, “A–aDO₂” < [age in years/4] + 4) NB: ↑ “A–aDO₂” → ↑ “Dead Space” Alveolar gas equation: • Useful in differentiating btw Hypoxia due to Lung pathology vs external factors
  10. 10. Alveolar gas equation variables definitions Quantity Description Sample value pAO2 The alveolar partial pressure of oxygen (pO2) 107 mmHg (14.2 kPa) FIO2 The fraction of inspired gas that is oxygen (expressed as a decimal). 0.21 PATM The prevailing atmospheric pressure 760 mmHg (101 kPa) pH2O The saturated vapour pressure of water at body temperature and the prevailing atmospheric pressure 47 mmHg (6.25 kPa) paCO2 The arterial partial pressure of carbon dioxide (pCO2) 40 mmHg (4.79 kPa) RER The respiratory exchange ratio 0.8
  11. 11. CLINICAL PRESENTATION RF may be preceded by signs of respiratory distress: • Tachypnoea (>25/min) • Breathlessness • Gasping or pursed lip breathing • Tight chest • Sweating, clamminess • Agitation • Sitting or hunched posture • Sense of impending doom • Inability to complete a sentences • Cyanosis • HYPOXAEMIA Sats<92% • HYPERCAPNEA
  12. 12. Pre-terminal Signs • Bradycardia, dysrhythmias, hypotension • Bradypnoea or silent chest • Decreased L.O.C
  13. 13. DIAGNOSTICS 1) VITAL SIGNS AND INSPECTION (BP, O₂ Sat, RR, T°C, LOC, airway patency) • Fever, tachycardia, tachypnea → Infection • Fever, lethargy → CNS infection /septic encephalopathy • ↑Pulsus paradoxus (>10 mmHg) → Asthma or COPD • Ethanol odour → Intoxication
  14. 14. DIAGNOSTICS 2) NEUROLOGICAL EXAMINATION • Depressed mental status (lethargy or coma) → Central drive failure • Pupillary constriction (miosis) “pinpoint pupils” → Opiate overdose (Severe hypercarbia causes miosis as well) • Sensory deficits → Polyneuropathy (e.g. GBS) • Muscle fasciculations → Motor neuron diseases (e.g. ALS)
  15. 15. DIAGNOSTICS 3) Head and Neck • Stridor, drooling → upper airway obstruction 4) Chest • Pattern of respiratory muscle contraction, chest diameter and intergrity (Flail chest), presence of abnormal breath sounds 5) Abdomen • Normal abdominal wall movement during inspiration is outward, inward movement with inspiration is paradoxical and suggests diaphragmatic fatigue.
  16. 16. DIAGNOSTICS Laboratory Testing 1. Arterial Blood Gas (ABG) ABGs are required very early and should be obtained as soon as possible after C-A-B has been assessed.
  17. 17. DIAGNOSTICS Normal values of arterial blood gases (at R.A., sea level, 37°C)
  18. 18. DIAGNOSTICS Interpretative remarks: • PaO₂ < 60mmHg(8kPa) →HYPOXEMIA • PaCO₂ > 50 mmHg(6.7 kPa) →HYPERCAPNIA • pH < 7.35 → ACIDOSIS • pH >7.45 → ALKALOSIS
  19. 19. DIAGNOSTICS Interpretative remarks: • ↓PaO₂ → TYPE I (Hypoxemic) RF • ↑PaCO₂, ↓pH →Acute TYPE II (Hypercapnic) RF • ↑PaCO₂, slightly↓pH, ↑HCO₃⁻ → Chronic TYPE II (Hypercapnic) RF
  20. 20. DIAGNOSTICS Interpretative remarks: • The "50–50 rule" of intubating is OUTDATED! • Respiratory acidosis (pH<7.20–7.25) is an indication ventilatory support. • Interpretation of an inadvertent venous blood gas (VBG) must be avoided. • Elevated HCO⁻₃ is evidence of chronic respiratory acidosis.
  21. 21. DIAGNOSTICS 2. Complete Blood Count (CBC) • Leukocytosis → infection • Anemia (dyspnea,↓O₂ transport to tissues, but in isolation will not cause ventilatory failure. 3. Lumbar Puncture (LP) • (essential in cases of suspected CNS infection or GBS) 4. Serum Chemistries • (↓Ca,Mg,PO⁻ may contribute to respiratory muscle fatigue) 5. Toxicology Tests 6. Pulmonary Function Tests
  22. 22. DIAGNOSTICS Imaging and Other Tests • CXR • (Pneumonia, atelectasis, pulmonary oedema, evidence of chronic lung disease, tumours, chest wall and pleural abnormalities) • CT Scan • (tumours, parenchymal lung disease, pleural and chest wall disease) • MRI • (encephalitis, brain stem pathology, and spinal cord injury) • ECG • (evidence of chronic lung disease, left ventricular failure or valve disease)
  23. 23. Principles of treatment • Emergency treatment should follow principles of cardiopulmonary resuscitation (C-A-B); • Ensure patent airway • Administer oxygen to maintain sats >90% • Correct hypoperfusion/anaemia followed by treatment of underlying (reversible) causes: • Acidosis/Alkalosis • Hypovolemia • Hypoxia • Pneumothorax • Pulmonary embolism
  24. 24. Principles of treatment (Cont…) • All patients with acute VF not responding to simple measures in an emergency room, clinic, or hospital ward setting should be monitored in an intensive/intermediate care unit. • Inhaled bronchodilators should be administered to all patients with bronchospasm. • Fever reduction with acetaminophen will decrease CO₂ production. • Avoid excessive caloric intake (which increases CO₂ production)
  25. 25. Principles of treatment (Cont…) • Consider non-invasive ventilatory support: • CPAP: continous positive airway pressure • BiPAP: Biphasic positive airway pressure • Evaluate patient for the need of Endotracheal intubation and mechanical ventilation (e.g. in cases of severe respiratory failure with PaO2 less than 50 mmHg).
  26. 26. Principles of treatment (Cont…) • DRUGS: • Respiratory stimulants (eg. Doxapram) (rarely used) • Antidote for sedative overdose » Opioids → naloxone » Benzodiazepines → flumazenil • Physiotherapy to mobilise secretions.
  27. 27. ***************The End*************** THANK YOU!!!
  28. 28. References 1. Hanley M. E., Welsh. H., Current Diagnosis & Treatment in Pulmonary Medicine,1st ed. Denver, Colorado, September 2003. 2. Kim E. Barrett, Susan M. Barman, Scott Boitano, and Heddwen L. Brooks, Ganong's Review of Medical Physiology, 24th ed., Singapore,2012. 3. BMJ Publishing Group Limited, BMJ Best Practice, 2015 http://bestpractice.bmj.com (accessed 13-04-2015).

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