Respiratory Support For Children with Heart Disease

1. Respiratory Support For Children with Heart Disease Reference: Congenital Heart Disease in Infants and Children, Second Edition, 2006, publisher MOSBY, Elselvier

2. Factors that INCREASE PVR Increase PaCO2 Decrease pH Decrease ventilatory rate Decrease tidal volume Add CO2 or dead space Increase PEEP (overdistention) Atelectasis Pain Agitation Dopamine Epinephrine Factors that INCREASE Systemic Ventricle Afterload Increase SVR High-dose dopamine Epinephrine Norepinephrine Pain Agitation Factors the DECREASE PVR Decrease PaCO2 Increase pH Increase ventilatory rate Increase tidal volume Inspired oxygen Optimize lung volume (neither overdistention or atelectasis Inhaled nitric oxide Adequate analgesia Adequate sedation Muscle relaxation Milrinone Prostaglandin E1 (for ductal dependent PBF) Factors that DECREASE Systemic Ventricle Afterload Decrease SVR Milrinone Dobutamine (increases HR) Captopril, enalapril Nitroprusside (unpredictable effect) Adequate analgesia Adequate sedation

3. Mechanical Ventilation • Life saving tool • Complication risk: • Ventilator induced lung injury • Nosocomial pneumonia • Increases sedation requirements • ETT airway injury • Cardiovascular instability • Bottom line: Discontinue as soon as possible

4. Goals of Respiratory Support • Optimize oxygen delivery by: • Improved blood oxygen content (arterial sat%) • Decreased oxygen demand (▼work of breathing) • Improve Carbon Dioxide elimination Start Simple!!!

5. Initial Ventilator Settings FiO2 = 0.6-1.0 Vt= 6-8 mL/kg RR=15-35 breaths/min (age based) Ti=0.3-1.0 seconds (neonate/child, considering RR) Ti=0.75-1.5 seconds (Adult, considering RR) Peep=2-4 cm H20 Mode=SIMV/PS SaO2 < 85% Go to inadequate O2 Delivery algorithm Adequate O2 delivery Adequate CO2 Elimination PaCO2 > 50 mmHg Go to inadequate CO2 elimination algorithm Wean FiO2 to < 0.60 rapidly For SaO2 > 90-92% Wean RR for PaCO2 < 50 mmHG Cardiorespiratory status is stabilized Clinical/Radiograph/PFTs improving FiO2≤ 0.50, RR < 25, PEEP ≤ 6 cm H2O

6. Decreased SaO2 Differential Diagnosis Right-to-Left Intracardiac Shunt Diagnosis: No significant response to FiO2 of 1.0 Medical treatment directed at: Improving Oxygen Delivery Increase hemoglobin Increase cardiac output Improving Pulmonary Blood Flow Decrease pulmonary vascular resistance Improve right ventricular function Surgical treatment as indicated Intrapulmonary Shunt Diagnosis = P(A-a)O2 gradient Alveolar Hypoventiliation Diagnosis = No P(A-a)O2 gradient Increase FiO2 Increase VT  FiO2 Optimize PEEP Assess respiratory mechanics if no improvement Assess total volume delivery (6 ml/kg) Decelerating flow ventilation (i.e. Pressure control ventilation of pressure regulated volume control) if no improvement Reevaluate Complete PFTs Consider HFOV if no improvement Consider ECMO

7. Increased PaCO2 Differential Diagnosis Small Airway Obstruction Bronchospasm Increased Te Decreased RR, Increased VT Decreased Ti Bronchodilator therapy/Steroids Support spontaneous ventilation with pressure support up to 35 cm H2O and increased PEEP to decrease expiratory work of breathing and support active exhalation Sedation/paralysis Small Airway Obstructions/Alveolar Collapse Inadequate Effective Alveolar Ventilation Large Airway Obstruction Assess for ETT obstruction Suction/Physiotherapy Consider changing endotracheal tube Bronchoscopy Increase VT to 10 mL/kg If no improvement Increase RR (Monitor for “gas trapping” and intrinsic PEEP Consider decelerating flow ventilation (i.e., PCV, PRVC) If no improvement Increase sedation, add paralysis if no improvement Consider high-frequency ventilation

8. Weaning and Extubation Readiness

9. Clinical Criteria for Extubation Readiness • Ventilator settings “sufficiently” weaned • Patient awake • Intact airway reflexes • Hemodynamically stable • Secretions manageable

10. Summary of Current Pediatric/Adult Weaning Studies • Gradual weaning may not be necessary • No reliable extubation readiness test • T piece and PS can be equally effective ERT • Lower vent rate weans are inferior ERT • Weaning protocols = faster weaning in adults • Corticosteroids: Not as effective as we think?

11. Risks for Extubation Failure • Young age (<24 months) • Dysgenetic or syndromic condition • Chronic respiratory disorder • Chronic neurologic condition • Need to replace ETT at admission for any reason • Upper airway obstruction: 37% of failed extubations

12. Extubation Failure • Defined as re-intubation within 24-48 hours of extubation • Pediatric failures: 4-8% • Emergent reintubation risks: • Adult and Pediatric studies • Associated with high mortality rate • Increased potential for morbidity • Pediatric extubation failure=5 fold increase in the risk of death

13. Upper Airway Obstruction (UAO) • UAO is associated with failed extubation • Cuffed vs Uncuffed debate • Leak test: air leak is heard around ETT at low pressure (<20-25 cm H2O) • Poorly reproducible • High utilization rate despite inadequate evidence • Serial measurements superior to single

14. Non-invasive Ventilation

15. NIV Advantages • Positive pressure ventilation without the ETT • CPAP: Continuous positive airway pressure • Easy to utilize • Multiple applications: Only 4 tested with RCT • COPD exacerbations • Acute cardiogenic pulmonary edema • Facilitating extubation in COPD patients • Immunocompromised patients

16. NIV: When to use it? • Clinical State: • Sick but not moribound • Able to protect airway • Conscious and cooperative • Haemodynamically stable • No excessive respiratory secretions • Feeding issues?

17. Contra-indications to NIV • Facial burns/trauma • Recent facial or upper airway surgery • Fixed upper airway obstruction • Vomiting • Undrained pneumothorax

18. Setting Up NIV • Mode: CPAP versus BIPAP • EPAP: 4-5 cm H20 • IPAP: 12-15 cm H20 (increase to 20 cm H20) • Triggers: Maximum sensitivity • Back up rate: 15 breaths/min • Back up I:E ratio 1:3

19. Initiating NIV • Prepare for Plan B if NIV fails • Explain NIV to patient • Select mask and hold in place for several minutes prior to starting ventilator • Set up ventilator • Start NIV and hold mask on patient face • Place straps/headgear if mask tolerated • Reassess after a few minutes • Adjust as necessary • Recheck +/- blood gases in 1-2 hours

20. Clinical Assessment for Response: NIV • Chest wall movement • Coordination of respiratory effort with the ventilator • Accessory muscle recruitment • Heart rate • Respiratory rate • Patient comfort • Mental state

21. Troubleshooting NIV • Is the treatment of underlying condition optimal? • Have complications developed? • Pneumothorax, aspiration pneumonia, crepitus • PaCO2 still elevated? • Too much oxygen? • System leakage? Mask fit, chin strap, full face, circuit leaks • Is rebreathing occurring? Patency of expiratory valve, increase EPAP • Is patient synchronizing with ventilator? • Is ventilation adequate? • PaCO2 improves but PaO2 remains low • Increase FIO2 • Consider increasing EPAP (with bilevel)

22. Discussion