Respiratory Failure (RF) by 7ROYwz6

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									Respiratory Failure (RF)


Prof. Omer Alamoudi, MD, FRCP,
         FCCP,FACP
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
 Arterial Blood Gases (ABG)
 Normal values at sea level
 pH          7.35-7.45         ↓pH        Acidosis
 PaO2        >70 mmHg            ↑pH      Alkalosis
                                  ↓ PaO2   Hypoxemia
 PaCO2       35-45 mmHg
                                  ↑PaCO2 Hypercapnia
 HCO3        22-28 mmol/l        ↓pH+ ↑PaCO2 R. acidosis
                                      ↑HCO3
                                ↑pH+↓PaCO2 R.Alkalosis
 Minute ventilation = Tidal          ↓HCO3
  volume X Respiratory rate
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
Classification of RF

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

  Acute RF                    Chronic RF
  Develops over minutes to    Develops over days
   hours                       ↑ in HCO3
  ↓ pH quickly to <7.2        ↓ pH slightly
  Example; Pneumonia          Polycythemia, Corpulmonale
                               Example; COPD
  Pathophysiologic causes of Acute RF

●Hypoventilation

●V/P mismatch

●Shunt

●Diffusion
  abnormality
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
  Pathophysiologic causes of Acute RF

●Hypoventilation

●V/P mismatch

●Shunt

●Diffusion
  abnormality
    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
  Pathophysiologic causes of Acute RF

●Hypoventilation

●V/P mismatch

●Shunt

●Diffusion
  abnormality
    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%
  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
  Pathophysiologic causes of Acute RF

●Hypoventilation

●V/P mismatch

●Shunt

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

Chronic bronchitis, emphysema       Chronic bronchitis,emphysema
Pneumonia, pulmonary edema          Severe asthma, drug overdose
Pulmonary fibrosis                  Poisonings, Myasthenia gravis
Asthma, pneumothorax                Polyneuropathy, Poliomyelitis
Pulmonary embolism,                 Primary ms disorders
Pulmonary hypertension              1ry alveolar hypoventilation
Bronchiectasis, ARDS
                                    Obesity hypoventilation synd.
Fat embolism, KS, Obesity
                                    Pulmonary edema, ARDS
Cyanotic congenital heart disease
                                    Myxedema, head and cervical
Granulomatous lung disease
                                       cord injury
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
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
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
Distinction between Noncardiogenic (ARDS)
and Cardiogenic pulmonary edema




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

         Indications
             Severe Hypoxemia
             Altered mental status
      Importance
         precise O2 delivery to the lungs

         remove secretion

         ensures adequate ventilation
 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%
     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
Management of ARF
 Oxyhemoglobin
dissociations curve




                      60mmHg
 Management of ARF
 4 – Mechanical
  ventilation
 Indications
      Persistence hypoxemia
       despite O2supply
      Decreased level of
       consciousness
      Hypercapnia with severe
       acidosis (pH< 7.2)
     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
   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
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
    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
   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
    relax smooth ms

 Diuretics (pulmonary edema)
    Frusemide, Metalzone
   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
  Management of ARF

 7 - Treatmentof the
  underlying causes
 Physiotherapy
      Chest percussion to
       loosen secretion
      Suction of airways
       Help to drain secretion
      Maintain alveolar
       inflation
      Prevent atelectasis, help
       lung expansion
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
     Complications of ARF
 Pulmonary                            Infections
    Pulmonary embolism                   Nosocomial infection
    barotrauma                           Pneumonia, UTI,
    pulmonary fibrosis (ARDS)             catheter related sepsis
    Nosocomial pneumonia              Renal
 Cardiovascular                          ARF (hypoperfusion,

    Hypotension, ↓COP
                                           nephrotoxic drugs)
                                          Poor prognosis
    Arrhythmia
                                       Nutritional
    MI, pericarditis
                                          Malnutrition, diarrhea
 GIT
                                           hypoglycemia,
    Stress ulcer, ileus, diarrhea,        electrolyte disturbances
     hemorrhage
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
Quiz
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