Respiratory Support For Children with Heart Disease

Reference: Congenital Heart Disease in Infants and Children, Second Edition, 2006, publisher MOSBY, Elselvier

Factors that INCREASE PVRIncrease PaCO2Decrease pH Decrease ventilatory rate Decrease tidal volume Add CO2 or dead spaceIncrease PEEP (overdistention)AtelectasisPainAgitationDopamineEpinephrine

Factors the DECREASE PVRDecrease PaCO2Increase pH Increase ventilatory rate Increase tidal volumeInspired oxygenOptimize lung volume (neither overdistention or atelectasisInhaled nitric oxideAdequate analgesiaAdequate sedationMuscle relaxationMilrinoneProstaglandin E1 (for ductal dependent PBF)

Factors that INCREASE Systemic Ventricle AfterloadIncrease SVR High-dose dopamine Epinephrine Norepinephrine Pain Agitation

Factors that DECREASE Systemic Ventricle AfterloadDecrease SVR Milrinone Dobutamine (increases HR) Captopril, enalapril Nitroprusside (unpredictable effect) Adequate analgesia Adequate sedation

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

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!!!

Initial Ventilator Settings

FiO2 = 0.6-1.0Vt= 6-8 mL/kgRR=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 H20Mode=SIMV/PS

SaO2 < 85%Go to inadequate O2

Delivery algorithm

Adequate O2 deliveryAdequate CO2 Elimination

PaCO2 > 50 mmHgGo to inadequate CO2 elimination algorithm

Wean FiO2 to < 0.60 rapidlyFor SaO2 > 90-92%

Wean RR for PaCO2 < 50 mmHG

Cardiorespiratory status is stabilizedClinical/Radiograph/PFTs improvingFiO2 ≤ 0.50, RR < 25, PEEP ≤ 6 cm H2O

Decreased SaO2 Differential Diagnosis

Right-to-Left Intracardiac ShuntDiagnosis: No significant response to FiO2 of 1.0Medical treatment directed at: Improving Oxygen Delivery Increase hemoglobin Increase cardiac output Improving Pulmonary Blood Flow Decrease pulmonary vascular resistance Improve right ventricular functionSurgical treatment as indicated

Intrapulmonary ShuntDiagnosis = P(A-a)O2 gradient

Alveolar HypoventiliationDiagnosis = No P(A-a)O2 gradient

Increase FiO2

Increase VT

FiO2

Optimize PEEPAssess 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

ReevaluateComplete PFTsConsider HFOV

if no improvement

Consider ECMO

Increased PaCO2 Differential Diagnosis

Small Airway ObstructionBronchospasm

Increased Te

Decreased RR, Increased VT

Decreased Ti

Bronchodilator therapy/SteroidsSupport spontaneous ventilation with pressure support up to 35 cm H2O and increased PEEP to decrease expiratory work of breathing and support active exhalationSedation/paralysis

Small Airway Obstructions/Alveolar CollapseInadequate Effective Alveolar Ventilation

Large Airway Obstruction

Assess for ETT obstructionSuction/PhysiotherapyConsider changing endotracheal tubeBronchoscopy

Increase VT to 10 mL/kg

If no improvement

Increase RR (Monitor for “gas trapping” and intrinsic PEEPConsider decelerating flow ventilation (i.e., PCV, PRVC)

If no improvement

Increase sedation, add paralysis

if no improvement

Consider high-frequency ventilation

Weaning and Extubation Readiness

Clinical Criteria for Extubation Readiness

• Ventilator settings “sufficiently” weaned

• Patient awake

• Intact airway reflexes

• Hemodynamically stable

• Secretions manageable

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?

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

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

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

Non-invasive Ventilation

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

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?

Contra-indications to NIV

• Facial burns/trauma

• Recent facial or upper airway surgery

• Fixed upper airway obstruction

• Vomiting

• Undrained pneumothorax

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

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

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

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)

Discussion