7.2 Pediatric NIV, Interfaces & Failure Recognition

7.2 Pediatric NIV, Interfaces & Failure Recognition

Pediatric Bi-Level Noninvasive Positive Pressure Ventilation (Bi-Level NIV)

In older infants, children, and adolescents, bi-level positive airway pressure (BiPAP) is indicated for acute hypoxemic or hypercapnic respiratory failure secondary to status asthmaticus, acute viral bronchiolitis, pneumonia, or neuromuscular weakness (e.g., Spinal Muscular Atrophy, Duchenne Muscular Dystrophy).

Pressure Settings & Titration Equations

Bi-level NIV delivers two discrete pressure levels:

1. Inspiratory Positive Airway Pressure (IPAP): Provides inspiratory assist above EPAP.
2. Expiratory Positive Airway Pressure (EPAP): Supplies baseline distending pressure.

Select starting pressures from age, interface, diagnosis, prior support, synchrony, leak, comfort, and the device or unit protocol; titrate rather than applying one universal pair.

Driving Pressure (Pressure Support, PS) = IPAP - EPAP

• Ventilation (CO2 Clearance): Increasing pressure support (PS) may increase tidal volume and ventilation, but patient effort, leak, compliance, resistance, dead space, and synchrony also matter. If a child demonstrates acute hypercapnic respiratory acidosis (PaCO2 > 55 mmHg):
  • Increase IPAP while holding EPAP constant: This widens the driving pressure (Delta P), directly increasing delivered Vt and clearing CO2.
  • Example: Increasing settings from 12/6 cmH2O (PS = 6) to 16/6 cmH2O (PS = 10) increases tidal volume.
• Oxygenation (PaO2 / SpO2): Governed by EPAP and FiO2. EPAP restores FRC and recruits collapsed alveoli.
  • For oxygenation: Titrate FiO2 and EPAP to the prescribed target and recruitability. If EPAP rises, IPAP may also need adjustment to preserve adequate support, but tidal volume is not guaranteed to remain constant; reassess leak, effort, ventilation, and hemodynamics.

Pediatric Interfaces

• Oro-Nasal (Full-Face) Mask: Covers both nose and mouth; ideal for mouth-breathing children or acute respiratory distress.
• Total Face Mask: Covers the entire face from forehead to chin; minimizes facial pressure points and is well tolerated in anxious or agitated pediatric patients.

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Table 7.1.1: Clinical Comparison of Noninvasive Interfaces

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Indications, Failure Criteria & Complications

Clinical Indications

• Neonatal RDS (early CPAP can support lung volume and reduce the need for invasive ventilation in selected infants).
• Post-extubation bridge in neonates and pediatrics to prevent atelectasis.
• Apnea of Prematurity (AOP) refractory to caffeine citrate.
• Moderate-to-severe acute viral bronchiolitis (RSV).
• Cardiogenic pulmonary edema and atelectasis.

Recognizing NIV Failure

Noninvasive support must not delay necessary endotracheal intubation. Escalate for a worsening trajectory using the patient’s ordered targets and pathway; concerning findings include:

1. Severe Work of Breathing: Worsening tachypnea, severe intercostal/subcostal retractions, sternal indrawing, marked nasal flaring, or expiratory grunting (Silverman-Andersen retraction score >= 7).
2. Refractory Hypoxemia: Inability to maintain the patient-specific saturation target despite rising FiO2 and appropriately titrated distending pressure.
3. Intractable Apnea: Frequent or severe apnea and bradycardia episodes requiring vigorous tactile or manual bag-mask resuscitation.
4. Uncompensated Respiratory Acidosis: Progressive hypercapnia and acidemia despite an adequate interface and a monitored trial of support; no single gas cutoff applies to every diagnosis.

Critical Complications

• Gastric Distension ("CPAP Belly"): High distending pressures force gas down the esophagus into the stomach, elevating the diaphragm, decreasing lung compliance, and increasing aspiration risk. Consider gastric decompression when distension impairs breathing or feeding, using the prescribed tube and drainage method; continuous or intermittent suction is not automatic.
• Air Leak Syndromes: Pulmonary interstitial emphysema (PIE), pneumothorax, and pneumomediastinum secondary to alveolar overdistension.
• Columellar and Nasal Skin Necrosis: Preventable through meticulous barrier application and rotation.

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Worked Clinical Calculation: Bi-Level NIV Titration

Clinical Scenario

A 2-year-old child (weight 12 kg) with severe acute viral bronchiolitis is receiving bi-level NIV with settings:

• IPAP = 12 cmH2O
• EPAP = 6 cmH2O
• FiO2 = 0.40

Current Arterial Blood Gas (ABG):

• pH = 7.27
• PaCO2 = 59 mmHg
• PaO2 = 82 mmHg
• HCO3- = 26 mEq/L
• SpO2 = 96%

Step-by-Step Clinical Analysis

1. Analyze the Acid-Base Defect: The patient exhibits acute uncompensated respiratory acidosis (pH < 7.35, elevated PaCO2). Oxygenation is adequate (PaO2 > 80 mmHg, SpO2 96% on FiO2 0.40).
2. Identify the Physiological Target: Alveolar minute ventilation must be augmented to clear CO2. In bi-level NIV, tidal volume is determined by the pressure support: PS = IPAP - EPAP = 12 - 6 = 6 cmH2O.
3. Formulate the adjustment: Increasing IPAP while holding EPAP constant raises pressure support and may increase tidal volume. A protocol-directed trial from IPAP 12 to 15 cmH2O with EPAP 6 raises PS from 6 to 9 cmH2O; reassess exhaled volume, leak, synchrony, effort, gas exchange, gastric distension, and tolerance rather than assuming PaCO2 will normalize.

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NPS Exam Traps Callout Box: Noninvasive Ventilation & CPAP

[!WARNING] NPS Exam Trap 1: Columella Compression vs. Prong Sizing If an exam question depicts an infant on bubble CPAP whose nasal septum is blanching or reddened, never choose "tighten the bonnet straps" or "advance the prongs deeper." The correct answer is to immediately reposition the prongs to leave a 1 to 2 mm clearance, ensure prongs are not oversized, and apply a hydrocolloid skin barrier or alternate to a nasal mask.

NPS Exam Trap 2: Cessation of Bubbles in Bubble CPAP When bubbling suddenly stops in a bubble CPAP circuit, do not jump to increasing the water depth! Increasing water depth changes the set pressure. Cessation of bubbling can reflect inadequate source flow, disconnection, obstruction, a major leak, or loss of the interface seal. Assess the infant first, then trace the circuit and verify prescribed flow and water depth. Address mouth leak only with an approved, safely fitted strategy and ongoing airway observation.

NPS Exam Trap 3: Adjusting Bi-Level for Hypercapnia vs. Hypoxemia For hypercapnia, increasing IPAP relative to EPAP may increase support; for hypoxemia, titrate FiO2 and EPAP to recruitability. After either change, reassess exhaled volume, leak, synchrony, effort, CO2, oxygenation, and hemodynamics.