Transcript Respiratory Failure

Respiratory Failure
Kenney Weinmeister M.D.
Definition
• Demand overwhelms the capacity of the
system
• Hypoxemia: PaO2 < 60 mmHg
• Hypercarbia: PaCO2 > 49 mmHg
Alveolar-arterial Oxygen Tension
Difference
• PAO2 = FIO2 x atmos. pres. - PaCO2/R
• PAO2 = 150 - PaCO2/0.8
• P(A-a) O2 gradient = 2.5 + 0.21 x age (yr)
Duration of Hypercarbia
• Acute minutes to hours
– Acute Change in pH = .008 x change PCO2
• Chronic days
– Chronic Change in pH = .003 x change PCO2
• Mixed
– Change in pH is >.003 <.008
Hypoxemic Respiratory Failure
• Hypoventilation
– Normal A-a gradient
• V/Q mismatch
– Elevated A-a gradient
• Significantly improves with !00% oxygen
• Right to left shunts
– Elevated A-a gradient
• Does not significantly improve with 100% oxygen
Hypercapnic Respiratory Failure
• Hypoventilation
– Extrapulmonary disorders
• Severe V/Q mismatch
Extrapulmonary Respiratory
Failure
• Hypoxemic with normal A-a gradient
• Hypercarbic acute or chronic
–
–
–
–
–
–
CNS
PNS
Respiratory muscles
Chest Wall
Pleura
Upper Airways
Central Nervous System Causes
of Respiratory Failure
•
•
•
•
•
Drugs
Hypothyroidism
Brainstem injury or tumor
Primary alveolar hypoventilation
Central sleep apnea
Peripheral Nervous System
Causes of Respiratory Failure
•
•
•
•
•
•
•
Spinal cord
Tetanus
Strychnine
ALS
Guillain Barre Synd.
Shellfish
Bilateral phrenic nerve
palsy
• Diptheria
• Pseudocholinesterase
deficiency
• Myasthenia Gravis
• Eaton-Lambert
• Botulism
• Organophosphate
poisoning
Respiratory Muscle Dysfunction
•
•
•
•
•
Muscular dystrophies
Myotonic dystrophies
Polymyositis
Periodic paralysis
Electrolyte disorders
Chest Wall and Pleural Disorders
•
•
•
•
•
•
Kyphoscoliosis
Obesity hypoventilation
Flail chest
Fibrothroax
Thoracoplasty
Ankylosing spondylitis
Upper Airway Obstruction
• Acute epiglottitis
• Bilateral vocal cord
paralysis
• Acute laryngeal edema
• Tracheal stenosis
– Anaphylaxis
– Trauma
• Tracheomalasia
• Foreign body
• Tumors
aspiration
• Retropharyngeal
hemorrhage
Pulmonary Causes of Respiratory
Failure
• Lower airway
– Asthma, COPD
• Parenchymal
– Pulm. Edema, infections, interstitial lung dz
• Pulmonary vasculature
– PE, Primary pulmonary hypertension
Options for Ventilation
• Noninvasive positive pressure ventilation
• Invasive positive pressure ventilation
• Negative pressure ventilation
Noninvasive Positive Pressure
Ventilation
• Continuous positive airway pressure
– Hypoxemia
– Functional airway obstruction
• Bilevel positive airway pressure
– Hypercarbia
– COPD
– Neuromuscular or chest wall disorders
Invasive Positive Pressure
Ventilation
•
•
•
•
Acute decompensation
Fail NIPPV
Mechanical Airway obstruction
Protect airway
Negative Pressure Ventilation
• Chronic respiratory failure
• Neuromuscular disease
• No functional airway obstruction
Conclusion
• Differentiate type of respiratory failure
– Hypoxemic vs hypercarbia
– Hypoventilation vs V/Q mismatch
• Determine if chronic or acute
• Most often acute respiratory failure due to
V/Q mismatch