Transcript Early Detection and Management of Respiratory Failure

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 PaCO2 > 50 mm of Hg
or PaO2 < 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
1. Upper airways obstruction:
> Laryngomalacia
> Subglottic stenosis
> Laryngotracheobronchitis
> Tracheitis & Epiglottitis
> Retropharyngeal / Peritonsillar abscess
> Acute hypertrophic tonsillitis
> Diphtheria
> foreign body, trauma, vocal cord palsy
2. Lower airway obstruction:
> Bronchiolitis, Asthma, Foreign body
3. Alveolar and pleural disease:
> pneumonia, pulmonary edema, effusion
empyma, pneumothorax, ARDS
4. 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:
1. PaO2
2. PaCO2
3. Alveolar-Arterial PO2 Gradient
P(A-a)O2 Gradient = PIO2 – PaCO2 / R
where PiO2 = partial pressure of inspired air,
R = 0.8
4. Hyperoxia Test
PaO2 / PaCO2
• Normal value depends on :
a. Position of patient during sampling
b. Age of patient
• PaO2 (Upright) = 104.2 -- 0.27 x age (Yrs)
• PaO2 (Supine) = 103.5 – 0.47 x age (Yrs)
• PaCO2 : normal value= 35-45 mm of Hg
unaffected by age/ positioning
Alveolar-Arterial O2 gradient
• Normal P(A-a)O2 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
1.
2.
3.
4.
Low PiO2 ~ at high altitude
Hypoventilation ~ Normal A-a gradient
Low V/Q mismatch ~ A-a gradient
R/L shunt ~ A-a gradient
Hypoventilation-Diagnosis
• PaO2
• PaCO2 is always increased
• A-a gradient is normal (≤ 10 mm of Hg)
• Hyperoxia Test : dramatic rise in PO2
V/Q mismatch- Diagnosis
• PaO2
• A-a gradient is
• PaCO2 may or may not be elevated
• Hyperoxia test : Dramatic rise in PaO2
R-L shunt: diagnosis
• PaO2 is
• PaCO2 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 PaO2 and
PaCO2 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
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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 PaO2.
• 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: O2 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
1. PaO2< 55 mm Hg or PaCO2 > 60 mm Hg
despite 100% oxygen therapy.
2. Deteriorating respiratory status despite
oxygen and Nebulization therapy
3. Anxious, sweaty lethargic child with
deteriorating mental status.
4. 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 PaCO2 to rise into the 60-70
mm of Hg range, as long as the patient is
adequately oxygenated (SaO2> 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.