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Early Detection And Management Of Respiratory Failure
 

Early Detection And Management Of Respiratory Failure

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    Early Detection And Management Of Respiratory Failure Early Detection And Management Of Respiratory Failure Presentation Transcript

    • Early Detection and Interventions in Respiratory Failure Dr Nigam Prakash Narain
    • Definition: Respiratory Failure
      • Defined as inadequate gas exchange due to pulmonary or non-pulmonary causes leading to hypoxemia, hypercarbia or both.
      • Documented by PaCO 2 > 50 mm of Hg or PaO 2 < 50-60 mm of Hg .
    • Status of ABG
      • Arterial Blood Gas analysis: single most important lab test for evaluation of respiratory failure .
    • Respiratory Failure: Causes
      • Upper airways obstruction:
      • > Laryngomalacia
      • > Subglottic stenosis
      • > Laryngotracheobronchitis
      • > Tracheitis & Epiglottitis
      • > Retropharyngeal / Peritonsillar abscess
      • > Acute hypertrophic tonsillitis
      • > Diphtheria
      • > foreign body, trauma, vocal cord palsy
      • Lower airway obstruction:
      • > Bronchiolitis, Asthma, Foreign body
      • Alveolar and pleural disease:
      • > pneumonia, pulmonary edema, effusion
      • empyma, pneumothorax, ARDS
      • CNS causes:
      • > Infections, injury, trauma, seizures
      • > tetanus, SMA, Polio
      • > AIDP, Phrenic nerve injury
      • > Myasthenia gravis, botulism,
      • > Muscle dystrophies, Polymyositis
      • > Congenital myopathies, muscle fatigue
    • Respiratory failure: clinical manifestations
      • Tachypnea
      • Exaggerated use of accessory muscles
      • Intercostal, supraclavicular and subcostal retractions
      • In neuromuscular disease, the signs of respiratory distress may not be obvious
      • In CNS disease, an abnormally low respiratory rate, and shallow breathing are clues to impending respiratory failure
    • Presentation
      • Three distinctive clinical profiles have been suggested in children:
      • 1. Mechanical dysfunction of airways
      • 2. Neuromuscular dysfunction
      • 3. Breathing control dysfunction
      • A rapid assignment to one of these profiles facilitates early diagnosis and treatment
    • Profile 1: Mechanical dysfunction of airways
      • Most common type
      • Results from alterations in the mechanical properties of the airways, lung parenchyma or chest wall.
      • Present with typical signs of respiratory distress:
      • increased effort, Tachypnea, retractions, accessory muscle use, nasal flaring, adventitious breath sounds, grunting
    • Profile 2: neuromuscular disease
      • Results from myopathies involving resp muscles or polyneuropathies / phrenic nerve injuries
      • Associated with an increased neural output, but is not effectively translated into effective contractions
      • Tachypnea, shallow respiratory efforts and profound dyspnea are characteristic
    • Profile 3: Alteration in control of breathing
      • Usually results from CNS injury / developmental deficits
      • Ondine’s curse, Apnea of prematurity, CNS injury / depression
      • Associated with decreased neural output to resp muscles, thus signs of respiratory distress are unusual, even with significant respiratory compromise
    • Evaluation of Respiratory failure
      • The following parameters are important in evaluation of respiratory failure:
      • PaO 2
      • PaCO 2
      • Alveolar-Arterial PO 2 Gradient
      • P(A-a)O 2 Gradient = P I O 2 – PaCO 2 / R
      • where P i O 2 = partial pressure of inspired air,
      • R = 0.8
      • Hyperoxia Test
    • PaO 2 / PaCO 2
      • Normal value depends on :
      • a. Position of patient during sampling
      • b. Age of patient
      • PaO 2 (Upright) = 104.2 -- 0.27 x age (Yrs)
      • PaO 2 (Supine) = 103.5 – 0.47 x age (Yrs)
      • PaCO 2 : normal value= 35-45 mm of Hg
      • unaffected by age/ positioning
    • Alveolar-Arterial O 2 gradient
      • Normal P(A-a)O 2 gradient: 5-10 mm of Hg
      • A sensitive indicator of disturbance of gas exchange.
      • Useful in differentiating extrapulmonary and pulmonary causes of resp. failure.
      • For any age, an A-a gradient > 20 mm of Hg is always abnormal.
    • Causes of Hypoxemia
      • Low P i O 2 ~ at high altitude
      • Hypoventilation ~ Normal A-a gradient
      • Low V/Q mismatch ~ A-a gradient
      • R/L shunt ~ A-a gradient
    • Hypoventilation-Diagnosis
      • PaO 2
      • PaCO 2 is always increased
      • A-a gradient is normal ( ≤ 10 mm of Hg)
      • Hyperoxia Test : dramatic rise in PO 2
    • V/Q mismatch- Diagnosis
      • PaO 2
      • A-a gradient is
      • PaCO 2 may or may not be elevated
      • Hyperoxia test : Dramatic rise in PaO 2
    • R-L shunt: diagnosis
      • PaO 2 is
      • PaCO 2 is usually normal
      • A-a gradient is
      • Hyperoxia Test : Poor / No response
    • Hypercapnia : Causes
      • Hypoventilation
      • Severe low V/Q mismatch: major mechanism of hypercapnia in intrinsic lung disease.
    • Status of ABG
      • It is not possible to predict PaO 2 and PaCO 2 accurately using clinical criteria.
      • Thus, the diagnosis of Respiratory failure depends on results of ABG studies.
    • Respiratory failure: Interventions
      • Supportive therapy
      • Specific therapy
    • Supportive therapy
      • Secure the airway
      • Pulse oximetry
      • Oxygen: by mask, nasal cannula, head box
      • Proper positioning
      • Nebulization if indicated
      • Blood sampling: Routine, electrolytes, ABG
      • Secure IV line
      • CXR: upright AP & lateral views
    • Hypoxemic / Non - Hypercapnic respiratory failure
      • The major problem is PaO 2.
      • If due to low V/Q mismatch; oxygen therapy.
      • If due to pulmonary intra-parenchymal shunts (ARDS), assisted ventilation with PEEP may be needed.
      • If due to intracardiac R-L shunt: O 2 therapy is of limited benefit. Surgical t/t is needed.
    • Hypercapnic Respiratory failure
      • Key decision is whether mechanical ventilation is required or not.
      • In Acute respiratory acidosis: Mechanical ventilation must be strongly considered.
      • Chronic Resp acidosis: patient should be followed closely, mech ventilation is rarely required.
      • In acute-on-chronic respiratory failure, the trend of acidosis over time is a crucial factor.
    • Mechanical Ventilation: Indications
      • PaO 2 < 55 mm Hg or PaCO 2 > 60 mm Hg despite 100% oxygen therapy.
      • Deteriorating respiratory status despite oxygen and Nebulization therapy
      • Anxious, sweaty lethargic child with deteriorating mental status.
      • Respiratory fatigue: for relief of metabolic stress of the work of breathing
    • Mechanical Ventilation: Strategies
      • Non-Invasive Ventilation: CPAP / BIPAP
      • Invasive Ventilation: SIMV, A/C, PAV
      • Other approaches to mechanical ventilation:
      • a. High frequency ventilation (HFV)
      • b. Permissive Hypercapnia
      • c. Prone positioning
      • d. ECMO
    • HFV
      • 3 types: Oscillatory, Jet & Flow interruption
      • Very small tidal volumes are used (<1ml/kg), very rapid rates (150-1000 bpm) and lower mean airway pressures are used.
      • This approach is used to minimize the possibility of barotrauma to airways.
      • Used if conventional ventilation fails to improve gas exchange
    • Permissive Hypercapnia
      • Allows the PaCO 2 to rise into the 60-70 mm of Hg range, as long as the patient is adequately oxygenated (SaO 2 > 92%), and able to tolerate the acidosis.
      • This strategy is used to limit the amount of barotrauma and volutrauma to the patient.
    • Prone positioning
      • Positioning the patient in the prone position has been shown to improve oxygenation and reduce ventilator induced lung injury.
      • However, the outcome may not be improved.
    • ECMO
      • Used in the treatment of newborns and small infants with life threatening, refractory respiratory failure, unresponsive to mechanical ventilation.
      • Inhales nitric oxide may improve oxygenation by reducing increased pulmonary vascular resistance.
      • Inhaled NO is now being used in place of ECMO in NICU in some centers.