1. Respiratory Failure (RF)
Prof. Omer Alamoudi, MD, FRCP, FCCP,FACP

2. Respiratory Failure (RF)
Normal ABG
Definition
Classification of RF
Distinction between Acute and Chronic RF
Pathophysiologic causes of Acute RF
Diagnosis of RF
Causes
Clinical presentation
Investigations
Management of RF

3. Arterial Blood Gases (ABG) Normal values at sea levelpH
PaO2 >70 mmHg
PaCO mmHg
HCO mmol/l
Minute ventilation = Tidal volume X Respiratory rate
↓pH Acidosis
↑pH Alkalosis
↓ PaO2 Hypoxemia
↑PaCO2 Hypercapnia
↓pH+ ↑PaCO2 R. acidosis
↑HCO3
↑pH+↓PaCO2 R.Alkalosis
↓HCO3

4. Respiratory Failure (RF)
Definitions
Clinical conditions in which PaO2 < 60 mmHg while breathing room air or a PaCO2 > 50 mmHg
Failure of oxygenation and carbon dioxide elimination
Acute and chronic
Type 1 or 2

5. Classification of RF Type 1 Type 2 Hypoxemic RF **
PaO2 < 60 mmHg with normal or ↓ PaCO2
Associated with acute diseases of the lung
Pulmonary edema (Cardiogenic, noncardiogenic (ARDS), pneumonia, pulmonary hemorrhage, and collapse
Type 2
Hypercapnic RF
PaCO2 > 50 mmHg
Hypoxemia is common
Drug overdose, neuromuscular disease, chest wall deformity, COPD, and Bronchial asthma

6. Distinction between Acute and Chronic RF
Acute RF
Develops over minutes to hours
↓ pH quickly to <7.2
Example; Pneumonia
Chronic RF
Develops over days
↑ in HCO3
↓ pH slightly
Polycythemia, Corpulmonale
Example; COPD

7. Pathophysiologic causes of Acute RF
●Hypoventilation
●V/P mismatch
●Shunt
●Diffusion abnormality

8. Pathophysiologic causes of Acute RF 1 - Hypoventilation
Occurs when ventilation ↓ 4-6 l/min
Causes
Depression of CNS from drugs
Neuromuscular disease of respiratory ms
↑PaCO2 and ↓PaO2
Alveolar –arterial PO2 gradient is normal
COPD

9. Pathophysiologic causes of Acute RF
●Hypoventilation
●V/P mismatch
●Shunt
●Diffusion abnormality 9

10. Pathophysiologic causes of Acute RF 2 -V/Q mismatch
Most common cause of hypoxemia
Low V/Q ratio, may occur either from
Decrease of ventilation 2ry to airway or interstitial lung disease
Overperfusion in the presence of normal ventilation e.g. PE
Admin. of 100% O2 eliminate hypoxemia

11. Pathophysiologic causes of Acute RF
●Hypoventilation
●V/P mismatch
●Shunt
●Diffusion abnormality 11

12. Pathophysiologic causes of Acute RF 3 -Shunt
The deoxygenated blood bypasses the ventilated alveoli and mixes with oxygenated blood → hypoxemia
Persistent of hypoxemia despite 100% O2 inhalation
Hypercapnia occur when shunt is excessive > 60%

13. Pathophysiologic causes of Acute RF 3 – Causes of Shunt
Intracardiac
Right to left shunt
Fallot’s tetralogy
Eisenmenger’s syndrome
Pulmonary
A/V malformation
Pneumonia
Pulmonary edema
Atelectasis/collapse
Pulmonary Hge
Pulmonary contusion

14. Pathophysiologic causes of Acute RF
●Hypoventilation
●V/P mismatch
●Shunt
●Diffusion abnormality 14

15. Pathophysiologic causes of Acute RF 4 - Diffusion abnormality
Less common
Due to
abnormality of the alveolar membrane
↓ the number of the alveoli
Causes
ARDS
Fibrotic lung disease

16. Diagnosis of RF 1 – Clinical (symptoms, signs)
Hypoxemia
Dyspnea, Cyanosis
Confusion, somnolence, fits
Tachycardia, arrhythmia
Tachypnea (good sign)
Use of accessory ms
Nasal flaring
Recession of intercostal ms
Polycythemia
Pulmonary HTN, Corpulmonale, Rt. HF
Hypercapnia
↑Cerebral blood flow, and CSF Pressure
Headache
Asterixis
Papilloedema
Warm extremities, collapsing pulse
Acidosis (respiratory, and metabolic)
↓pH, ↑ lactic acid

17. Diagnosis of RF 2 – Causes
1 – CNS
Depression of the neural
drive to breath
Brain stem tumors or vascular abnormality
Overdose of a narcotic, sedative
Myxedema, chronic metabolic
alkalosis
Acute or chronic hypoventilation
and hypercapnia

18. Diagnosis of RF 2 – Causes
2 - Disorders of peripheral
nervous system, Respiratory ms, and Chest wall
Inability to maintain a level of minute ventilation appropriate for the rate of CO2 production
Guillian-Barre syndrome, muscular dystrophy, myasthenia gravis, KS, morbid obesity
Hypoxemia and hypercapnia

19. Diagnosis of RF 2 – Causes
3 - Abnormities of the airways
Upper airways
Acute epiglotitis
Tracheal tumors
Lower airway
COPD, Asthma, cystic fibrosis
Acute and chronic hypercapnia

20. Diagnosis of RF 2 – Causes
4 - Abnormities of the alveoli
Diffuse alveolar filling
hypoxemic RF
Cardiogenic and noncardiogenic pulmonary edema
Aspiration pneumonia
Pulmonary hemorrhage
Associate with Intrapulmonary shunt and increase work of breathing

21. Diagnosis of RF 3 – Common causes
Hypercapnic RF
Hypoxemic RF
Chronic bronchitis,emphysema Severe asthma, drug overdose Poisonings, Myasthenia gravis Polyneuropathy, Poliomyelitis Primary ms disorders 1ry alveolar hypoventilation Obesity hypoventilation synd. Pulmonary edema, ARDS Myxedema, head and cervical cord injury
Chronic bronchitis, emphysema Pneumonia, pulmonary edema Pulmonary fibrosis Asthma, pneumothorax Pulmonary embolism, Pulmonary hypertension Bronchiectasis, ARDS Fat embolism, KS, Obesity Cyanotic congenital heart disease Granulomatous lung disease

22. Diagnosis of RF 3 - Investigations
ABG
CBC, Hb
Anemia → tissue hypoxemia
Polycythemia → chronic RF
Urea, Creatinine
LFT → clues to RF or its complications
Electrolytes (K, Mg, Ph) → Aggravate RF
↑ CPK, ↑ Troponin 1 → MI
↑CPK, normal Troponin 1 → Myositis
TSH → Hypothyroidism

23. Diagnosis of RF 3 - Investigations
Chest x ray → Pulmonary edema → ARDS
Echocardiography → Cardiogenic pulmonary edema
→ ARDS
→ PAP, Rt ventricular hypertrophy in CRF
■ PFT- (FEV1/ FVC ratio)
Decrease → Airflow obstruction
Increase → Restrictive lung disease

24. Diagnosis of RF 3 - Investigations
ECG → cardiac cause of RF
→ Arrhythmia due to hypoxemia and severe acidosis
■ Right heart catheterization to measure
●Pulmonary capillary wedge pressure (PCWP)
● Normal → ARDS (<18 mmHg)
● Increased → Cardiogenic pulmonary edema

25. Distinction between Noncardiogenic (ARDS) and Cardiogenic pulmonary edema

26. Distinction between Noncardiogenic (ARDS) and Cardiogenic pulmonary edema
Tachypnea, dyspnea, crackles
Aspiration, sepsis
3 to 4 quadrant of alveolar flooding with normal heart size, systolic, diastolic function
Decreased compliance
Severe hypoxemia refractory to O2 therapy
PCWP is normal <18 mm Hg
Cardiogenic edema
Tachypnea, dyspnea, crackles
Lt ventricular dysfunction, valvular disease, IHD
Cardiomegaly, vascular redistribution, pleural effusion, perihilar bat-wing distribution of infiltrate
Hypoxemia improved on high flow O2
PCWP is High >18 mmHg

27. Management of ARF

28. Management of ARF ICU admition 1 -Airway management Indications
Endotracheal intubation:
Indications
Severe Hypoxemia
Altered mental status
Importance
precise O2 delivery to the lungs
remove secretion
ensures adequate ventilation

29. Management of ARF 2 -Correction of hypoxemia
O2 administration via nasal prongs, face mask, intubation and Mechanical ventilation
Goal: Adequate O2 delivery to tissues
PaO2 = > 60 mmHg
Arterial O2 saturation >90%

30. Management of ARF 3- Correction of hypercapnia
Control the underlying cause
Controlled O2 supply
1 -3 lit/min, titrate according O2 saturation
O2 supply to keep the O2 saturation >90% but <93 to avoid inducing hypercapnia
COPD-chronic bronchitis, emphysema 30

31. Management of ARF
Oxyhemoglobin
dissociations curve
60mmHg 31

32. Management of ARF 4 – Mechanical ventilation Indications
Persistence hypoxemia despite O2supply
Decreased level of consciousness
Hypercapnia with severe acidosis (pH< 7.2)

33. Management of ARF 4 - Mechanical ventilation Increase PaO2 Lower PaCO2
Rest respiratory ms (respiratory ms fatigue)
Ventilator
Assists or controls the patient breathing
The lowest FIO2 that produces SaO2 >90% and PO2 >60 mmHg should be given to avoid O2 toxicity

34. Management of ARF 5 -PEEP (positive End-Expiratory pressure
Used with mechanical ventilation
Increase intrathoracic pressure
Keeps the alveoli open
Decrease shunting
Improve gas exchange
Hypoxemic RF (type 1)
ARDS
Pneumonias

35. Management of ARF 6 - Noninvasive Ventilatory support (IPPV)
Mild to moderate RF
Patient should have
Intact airway,
Alert, normal airway protective reflexes
Nasal or full face mask
Improve oxygenation,
Reduce work of breathing
Increase cardiac output
AECOPD, asthma, CHF

36. Management of ARF 7 - Treatment of the underlying causes
After correction of hypoxemia, hemodynamic stability
Antibiotics
Pneumonia
Infection
Bronchodilators (COPD, BA)
Salbutamol
reduce bronchospasm
airway resistance 36

37. Management of ARF 7 - Treatment of the underlying causes
Anticholinergics (COPD,BA)
Ibratropium bromide
inhibit vagal tone
relax smooth ms
Theophylline (COPD, BA)
improve diaphragmatic contraction
Diuretics (pulmonary edema)
Frusemide, Metalzone

38. Management of ARF 7 - Treatment of the underlying causes
Methyl prednisone (COPD, BA, acute esinophilic pn)
Reverse bronchospasm, inflammation
Fluids and electrolytes
Maintain fluid balance and avoid fluid overload
IV nutritional support
To restore strength, loss of ms mass
Fat, carbohydrate, protein

39. Management of ARF 7 - Treatment of the underlying causes Physiotherapy
Chest percussion to loosen secretion
Suction of airways
Help to drain secretion
Maintain alveolar inflation
Prevent atelectasis, help lung expansion

40. Management of ARF 8 - Weaning from mechanical ventilation
Stable underlying respiratory status
Adequate oxygenation
Intact respiratory drive
Stable cardiovascular status
Patient is a wake, has good nutrition, able to cough and breath deeply

41. Complications of ARF GIT Pulmonary Pulmonary embolism barotrauma
pulmonary fibrosis (ARDS)
Nosocomial pneumonia
Cardiovascular
Hypotension, ↓COP
Arrhythmia
MI, pericarditis
GIT
Stress ulcer, ileus, diarrhea, hemorrhage
Infections
Nosocomial infection
Pneumonia, UTI, catheter related sepsis
Renal
ARF (hypoperfusion, nephrotoxic drugs)
Poor prognosis
Nutritional
Malnutrition, diarrhea hypoglycemia, electrolyte disturbances

42. Prognosis of ARF Mortality rate for ARDS → 40%
Younger patient <60 has better survival rate
75% of patient survive ARDS have impairment of pulmonary function one or more years after recovery
Mortality rate for COPD →10%
Mortality rate increase in the presence of hepatic, cardiovascular, renal, and neurological disease

43. Quiz

44. Thank you