Pediatric Respiratory Failure Treatment & Management

Management of acute respiratory failure begins with a determination of the underlying etiology. While supporting the respiratory system and ensuring adequate oxygen delivery to the tissues, initiate an intervention specifically defined to correct the underlying condition. For example, a patient with status asthmaticus is given supplemental oxygen to treat hypoxemia, but corticosteroids and beta-agonist drugs are also given to treat the underlying pathology.

See the following Medscape Drugs & Diseases articles for specific treatment: Pediatric Acute Respiratory Distress Syndrome, Pediatric Pneumonia, Pediatric Asthma, and Pediatric Status Asthmaticus.

Extrathoracic airway support

For partial upper-airway obstruction (eg, from anesthesia or acute tonsillitis), place a nasopharyngeal airway to provide a passageway for air. ^[10] An oropharyngeal airway can be used temporarily in the unconscious patient.

For extrathoracic airway obstruction, as in croup, the following measures may be helpful:

• Racemic epinephrine 2.25% (an aerosolized vasoconstrictor) or an equivalent dose of L-epinephrine

• Systemic corticosteroids: To decrease airway edema

• Heliox (helium and oxygen gas mixture): To decrease the work of breathing

• Inspired humidity: To liquefy secretions

• Nebulized hypertonic (3%) saline

Heliox has a helium concentration of 60-80% and thus has a density lower than that of air; it improves breathing by reducing turbulent airflow through a narrowed area. A limiting factor in the use of Heliox is that it typically contains oxygen in the same concentration as room air, and some patients may require higher concentrations of oxygen.

Consultations

Consultations may be indicated with the following:

• Neurologist, for neuromuscular weakness evaluation

• Cardiologist, if left-sided valvar obstruction or cardiomyopathy is suspected

• Pulmonologist, for chronic pulmonary diseases

• Otorhinolaryngologist, for evaluation of foreign-body aspiration or anatomic abnormality

• Anesthesiologist, if a difficult airway is anticipated

• Surgeon (otorhinolaryngologist or pediatric), if surgical airway may indicated

Endotracheal intubation is occasionally needed to maintain airway patency in certain cases (eg, epiglottitis, thermal burns to the airway, severe croup). In general, uncuffed tubes are used in children younger than 8 years because the subglottic trachea surrounded by the cricoid cartilage is the narrowest part of the pediatric airway.

Cuffed endotracheal tubes are typically preferred over uncuffed endotracheal tubes in the pediatric population ^{[11, 12, 13]} (cuffs provide a seal against the tracheal wall), particularly those with a high volume and low pressure, as well as a standard internal-to-external diameter ratio and clear length markers. ^{[14, 15]} Several studies have concluded that the incidence of postextubation stridor and subglottic stenosis are not increased with high-volume, low-pressure cuffed endotracheal tubes. ^{[16, 17, 18]}

The appropriate endotracheal tube size is generally based on the age of the child. In neonates and infants younger than 6 months, a cuffed endotracheal tube with an inner diameter (ID) of 3.5-4 mm is appropriate. In infants aged 6-12 months, a cuffed tube with a 4-4.5 mm ID is appropriate. A useful bedside or field guideline for appropriate endotracheal tube size is approximately the size of the patient’s fifth finger.

In children older than 1 year, the following formula can be used: Tube size (ID in millimeters) = (age in years + 16)/4

The mnemonic MSOAPP can be used to remember the preparation essential for a safe tracheal intubation procedure, as follows:

• M - Monitors (heart rate, blood pressure, pulse oximetry, capnography for CO₂ detection)

• S - Suction and catheters

• O - Oxygenation with a bag-valve mask

• A - Apparatus (laryngoscope, endotracheal tubes appropriate for the patient's age and a half-size smaller and larger, stylets, oral airways)

• P - Pharmacy (medications for amnesia and paralysis)

• P = People (respiratory therapist, nurse, a skilled set of hands)

In adults, confirming proper sizing is accomplished by allowing the breathing circuit pressure to rise until air leaking around the tube can be auscultated, ideally approximately 15-18 cm water; the endotracheal tube cuff is then inflated.

As noted, in infants and children, a cuffed endotracheal tube that has high volume and low pressure is commonly used. ^{[14, 15]} It is important to place the proper-diameter endotracheal tube to optimize ventilatory support. Colorimetric end tidal CO2 detection is the most reliable method of confirmation of endotracheal tube placement. ^[19] Radiographic confirmation is also advisable, with the distal tip ideally positioned midway between the thoracic inlet and the carina.

Oxygen therapy

The initial treatment for hypoxemia is to provide supplemental oxygen. High-flow (>15 L/min) oxygen delivery systems include a Venturi-type device that places an adjustable aperture lateral to the stream of oxygen. Oxygen is mixed with entrained room air, and the amount of air is adjusted by varying the aperture size. The oxygen hoods and tents also supply high gas flows.

Low-flow (< 6 L/min) oxygen delivery systems include the nasal cannula and simple face mask.

Humidified high-flow nasal cannula therapy

In the last decade, HHFNC has been shown to be a safe, tolerable, available/portable, and easily manageable noninvasive ventilatory support in children with respiratory failure, as well as a viable alternative to nasal continuous positive airway pressure (nCPAP). ^{[8, 20]}

Indications for use of HHFNC in infants and children include the following ^[20] :

• Acute bronchiolitis
• Asthma
• Congenital heart diseases
• Obstructive sleep apnea
• Pneumonia

No single universally accepted definition is available for what constitutes humidified high-flow nasal cannula (HHFNC) therapy in neonates; however, a widely used and reasonable definition is optimally warmed (body temperature) and humidified respiratory gases delivered by nasal cannula at flow rates of 2-8 L/min. ^[21] Temperature, gas flow, and fraction of inspired oxygen (FiO2) are three independent parameters that must be adjusted on the basis of the pediatric patient's characteristics. ^[20] Venanzi et al indicate the idea temperature should be 34ºC in this population (range 34-37ºC); with a flow setting of up to 60 L/min (based on body weight: 1-2 L/kg/min); and an FiO2 setting for a goal of 95-97% saturation. ^[20]

Continuous positive airway pressure

CPAP may be indicated if lung disease results in severe oxygenation abnormalities such that an FiO₂ greater than 0.3 is needed to maintain a PaO₂ greater than 60 mm Hg. This modality aids in the unloading of fatigued respiratory muscles and prevention of collapse of peripheral small airways during exhalation. ^[8]

CPAP in pressures from 3-10 cm water is applied to increase lung volume and may redistribute pulmonary edema fluid from the alveoli to the interstitium.

CPAP enhances ventilation to areas with low V/Q ratios and improves respiratory mechanics. ^[8] Furthermore, CPAP may be of benefit in locales where invasive ventilatory support is not available.

If a high concentration of FiO₂ is needed and if the patient does not tolerate even short periods of discontinued airway pressure, positive-pressure ventilation should be administered.

Noninvasive positive-pressure ventilation (NPPV)

Noninvasive positive-pressure ventilation (NPPV) refers to assisted ventilation provided with nasal prongs or a face mask instead of an endotracheal or tracheostomy tube. This therapy can be administered to decrease the work of breathing and to provide adequate gas exchange.

NPPV can be given by using a volume ventilator, a pressure-controlled ventilator, or a device for bilevel positive airway pressure (BIPAP or bilevel ventilator) (see the image below). As with CPAP, BIPAP also unloads fatigued respiratory muscles and prevents collapse of peripheral small airways during exhalation. ^[8]

The RAM cannula, developed by a clinician at the Children’s Hospital of Los Angeles, provides the comfort and ease of a nasal cannula and, when attached to a ventilator circuit, can deliver true noninvasive positive-pressure ventilation in both the conventional mode and the high-frequency mode. Currently, it is the only device that has this capability.

Inspiratory pressure support is a ventilator modality in which increased circuited pressure during inspiration boosts the patient's effort. However, the patient's effort, as reflected by sensitive measurement of the circuit gas flow, triggers both the beginning and end of the inspiratory phase of the mechanical cycle.

It is crucial to closely monitor patient response once NIPPV is initiated owing to the potential for treatment failure within 1-6 hours of starting NIPPV in the setting of persistent hypoxemia and tachypnea. ^[8]

Potential drawbacks of noninvasive ventilation include inappropriate delay of the start of mechanical ventilation via endotracheal tube. ^[22] In addition, gastric distention can occur, with possible pulmonary aspiration.

The severity of the patient's disease limits the use of this technique. Prolonged wearing of the facial interface can lead to nasal congestion, facial reddening, eye irritation, or ulceration of the nasal bridge. If periodic relief from the face mask or nasal prongs is unavailable for several days, tracheal intubation is necessary and safer.

Conventional mechanical ventilation

Mechanical ventilation increases minute ventilation and decreases dead space. This approach is the mainstay of treatment for acute hypercapnia and severe hypoxemia. Conventional mechanical ventilation optimizes lung recruitment, increases mean airway pressure and functional residual capacity, and reduces atelectasis between breaths.

A primary strategy for mechanical ventilation should be the avoidance of high peak inspiratory pressures and the optimization of lung recruitment. In adults with ARDS, a strategy to provide low tidal volume (6 mL/kg) with optimized positive end-expiratory pressure (PEEP) offers a substantial survival benefit compared with a strategy for high tidal volume (12 mL/kg).

According to the permissive hypercapnia strategy in ARDS, arterial CO₂ is allowed to rise to levels as high as 100 mm Hg while the blood pH is maintained above 7.2 by means of intravenous administration of buffer solutions. This is done to limit inspiratory airway pressure to values below 35 cm water.

PEEP should be applied to a point above the inflection pressure such that alveolar distention is maintained throughout the ventilatory cycle.

Inverse ratio ventilation

During positive pressure ventilation, the inspiratory phase is prolonged in excess of the expiratory phase. This increases mean airway pressure and improves oxygenation during severe acute lung disease. Inverse ratio ventilation is a nonphysiologic pattern for breathing; therefore, these patients are administered heavy sedation and paralysis.

Airway pressure release ventilation (APRV)

Airway pressure release ventilation (APRV) is a relatively new form of inverse-ratio ventilation in which a continuous gas flow circuit is used. This method allows the patient to breathe spontaneously throughout the ventilatory cycle.

In concept, APRV applies a continuous airway pressure (P_high) identical to that of CPAP to maintain lung volume and promote alveolar recruitment. In addition, a time-cycled release phase lowers the set pressure (P_low) to augment ventilation.

Clinical and experimental studies with APRV demonstrate improvements in gas exchange, cardiac output, and systemic blood flow. Some data suggest reduced use of sedatives and neuromuscular blockers. ^[23]

High-frequency oscillatory ventilation (HFOV)

High-frequency oscillatory ventilation (HFOV) combines small tidal volumes (smaller than the calculated airway dead space) with frequencies of 15 Hz to minimize the effects of elevated peak and mean airway pressures.

HFOV has proven benefit in improving the occurrence and treatment of air-leak syndromes associated with neonatal and pediatric acute lung injury.

Prone positioning

Prone positioning reduces compliance of the thoracoabdominal cage by impeding the compliant rib cage. Gases should distribute toward the sternal and anterior diaphragmatic regions that become dependent on prone positioning. Improved homogeneity of ventilation improves oxygenation. This measure may cause a redistribution of blood flow, improving the V/Q match.

Researchers in a multicenter randomized controlled clinical trial concluded that prone positioning did not significantly reduce ventilator-free days, mortality, or time to recovery in pediatric patients with acute lung injury. ^[24]

Inhaled nitric oxide

Nitric oxide (NO) is an endogenous free radical that mediates smooth muscle relaxation throughout the body. When delivered by means of inhalation, the potential benefit of NO is to improve ventilation to perfusion matching by enhancing pulmonary blood flow to well-ventilated parts of the lung.

This therapy is relatively safe because hemoglobin inactivates it quickly and because does not cause systemic vasodilation leading to hypotension. However, methemoglobin and nitrogen dioxide (NO₂) levels should be monitored.

Inhaled NO is being studied for use in type I respiratory failure; in 1999, the FDA approved its use in neonates with hypoxic respiratory failure and evidence of pulmonary hypertension. Research continues on the value of inhaled NO for other pulmonary conditions, such as bronchopulmonary dysplasia, as well as possible roles for other mediators of pulmonary vasodilation, such as sildenafil and bosentan.

Administration of exogenous surfactant

Surfactant is an endogenous complex of lipids and proteins that lines the walls of alveoli and promotes alveolar stability by reducing surface tension. Relative surfactant deficiency and inactivation are variably present as a consequence of many lung diseases.

Exogenous surfactant replacement is of clear benefit to improve respiratory mechanics and oxygenation in the neonatal respiratory distress syndrome (RDS). Its role in severe lung injury in other pediatric populations or adults is still being investigated. Researchers in a multicenter randomized blinded clinical trial concluded that exogenous surfactant replacement in pediatric acute lung injury decreased mortality but that it had no effect on ventilator-free days. ^[25]

One deterrent to surfactant administration is the need for endotracheal intubation for its delivery. An intriguing pilot study recently completed suggests that exogenous surfactant may be successfully administered via placement of a laryngeal mask airway (LMA), rather than an endotracheal tube. ^[26]

Complications of mechanical ventilation

In a spontaneously breathing patient with high minute ventilation, care must be taken to maintain that level if tracheal intubation is required. The purpose is to avoid a sudden increase in PaCO₂ that could contribute to hemodynamic instability or cardiopulmonary arrest.

Tracheal intubation may lead to upper-airway edema and difficult extubation, especially in patients with chronic illness and a limited baseline pulmonary reserve.

Ventilator-induced lung injury (VILI) may occur secondary to alveoli overdistention (volutrauma). Air-leak syndromes, pneumothorax, or pulmonary interstitial emphysema may occur secondary to elevated inspiratory pressures. Prolonged mechanical ventilation can lead to diaphragmatic atrophy and contractile dysfunction, termed ventilator-induced diaphragmatic dysfunction (VIDD), and VILI from positive pressure ventilation (PPV) (but not negative pressure ventilation [NPV]) may play a role in the development of VIDD. However, a recent study in rats showed no difference in the occurrence of VIDD with PPV versus NPV. ^[27]

Posthypercapnic alkalosis can occur in patients with chronic hypercapnia if PaCO₂ is rapidly reduced with mechanical ventilation. The kidneys have a relatively slow mechanism to correct the bicarbonate excess. The metabolic alkalosis can be treated by replacing chloride or by increasing renal bicarbonate excretion with acetazolamide.

Extracorporeal life support (ECLS)/extracorporeal membrane oxygenation (ECMO)

In ECLS/ECMO, blood is removed from the patient, passed through an artificial membrane where gas exchange occurs, and is returned to the body by either the arterial (venoarterial [VA]) or venous (venovenous [VV]) system. This type of respiratory support has increasingly evolved over the years for use in infants with respiratory failure who have a higher risk and more heterogenous group of underlying conditions. ^[28] VV ECLS has become the preferred method for patients of all age groups who do not require cardiac support.

If a patient has moderate-to-severe oxygenation issues, the decision to transfer him or her to a tertiary care center for potential rescue therapy with ECLS/ECMO should be made within the first 5 days of acute illness.

A relatively recent form of ECLS/ECMO is extracorporeal carbon dioxide removal (ECCO2R), in which the goal is to minimize respiratory acidosis in those with acute hypoxemic or acute hypercapnic respiratory failure. ^[29] Although ECCO2R is of increasing interest, the associated technical complications and lack of high-quality evidence warrant greater investigations.