Objectives

Understand specific challenges of pediatric airway management in EMS
Review the limits of NIPPV therapy
Explain indications and contraindications for BIPAP/CPAP in pediatrics
Analyze specific cases for application of NIPPV in EMS

Introduction

Deployment of CPAP and BIPAP in EMS has evolved over the last decade and is arguably first line intervention for acute respiratory distress for multiple adult populations. Despite these advances, we have left children behind for no reason. Pediatric patients are well known for their ability to compensate until respiratory arrest, without a declining period, we often miss opportunities to intervene and alter patient outcomes. We have equipment; why not order smaller masks and start tomorrow? Not quite that fast, remember: "Kids are not small adults!"

A case study will guide us through use of BIPAP in an acute pediatric patient. You respond to the home of Jeremiah Williams, an eight-year-old male in acute respiratory distress. On arrival, you find your patient seated on the edge of the couch with a rapid respiratory rate and the following vital signs.

HR 138

RR 42

SpO2 84%

Temp 101.3F

Before we jump in to help our patients let's review anatomy and physiology of pediatric airways and pulmonary function.

Photo by Zdan Ivan
A boy making inhalation with a nebulizer at home.

Peds Airway Anatomy Review

Multiple differences from anatomical and physiological perspective along with pathological conditions require special attention when providing airway and respiratory management to pediatric patients.

Anatomical & Physiological differences

A large occipital lobe of pediatric patients versus adult changes axis of upper airway structures. The head flexes, (Figure 1), obstructing the airway, requiring thoracic manipulation to create a sniffing position. A towel can be placed behind shoulders and upper back placing occipital head and upper back at similar heights (Figure 2).

The tongue is relatively larger compared to pharynx size. The large tongue makes it more difficult to visualize the larynx even under direct laryngoscopy. A decreased level of consciousness due to sedation, head injury, toxin ingestion, metabolic disturbances and other nervous system dysfunctions are common causes of upper airway obstruction via tongue. ³

The epiglottis and larynx demonstrate additional anatomical differences. The epiglottis is large and floppy, and larynx is shaped like a funnel with the narrowest part of the airway at the cricoid cartilage. The larynx in a pediatric is only about five to seven centimeters (Figure 3.)

"Anatomy of Pediatric Airway with Severe Laryngomalacia." Nmal. 16 Sep 2013 7:46 EDT. Nucleus Medical Media. 20 Oct 2015
Figure 3

The position of ribs (horizonal) and geometric shape (barrel-shaped) of the thoracic cavity reduce intercostal contractions in driving ventilation. Pediatrics patients rely on diaphragmatic movement, compared to intercostal muscles in adults. The diaphragm has proportionately less type 1 muscle fibers, allowing for fatigue. ³

The thoracic cage in pediatric patients is more compliant, allowing children to sustain blunt force trauma without fractures. The pulmonary space is less compliant and prone to pneumothoraces with increased positive pressure. ³

Understand anatomical and physiological differences of pediatric patients allows the EMS provider to recognize when a child is in extremis, appreciate physiologic limitations and apply appropriate interventions.

Airway Assessment

A pediatric patient with airway concern requires a rapid assessment, using the pediatric assessment triangle (PAT). The patient's appearance, work of breathing and skin color and condition are evaluated to gauge degree of distress. The PAT should be completed on approaching the patient, promptly pinpointing:

Accessory muscle use
Nasal flaring
Intercostal retractions
Grunting or noisy breath sounds

While your team starts assessing the patient, a focused pediatric pulmonary history should be obtained from a parent or family member. The SAMPLE mnemonic is helpful in obtaining basic information followed by PACES and symptomatic assessment.

Preemie (lung problems at birth)

Asthma and or bronchiolitis history

Congenital medical problems (cardiovascular or neuromuscular defects)

Environmental exposures (smokers in home)

Sibling who had SIDS

Cough
Sputum
Dyspnea
Hemoptysis
Wheezing

Back to our case, Jeremiahs' older brother provides a brief history, including the following;

Increased shortness of breath in the past 24 hours
Hx of asthma
Hx of "lung problems" at birth
Wheezing and coughing for the past week, however this increased dramatically when a house down the street caught fire 24 hours prior.

You apply oxygen and establish IV access in his left forearm without resistance from Jeremiah. The monitor shows ST in the 130's and EtCO2 of 28mmHg. A small volume nebulizer treatment is started, and your partner is drawing up RSI medications. You realize that you will be intubating this child now or later. In effort to avoid intubation or pre-oxygenate for intubation, pending treatment, you elect to start BIPAP. Your partner chimes in "are we doing rescue therapy or pre-oxygenation?" Good question.

Types of NIPPV — BIPAP Versus CPAP

Non-Invasive Positive Pressure Ventilation (NIPPV) includes continuous positive airway pressure (CPAP) and Bi-level positive airway pressure (BiPAP). Many of us are familiar with CPAP as this has been the "go to therapy" for CHF and COPD patients over the past decade. CPAP works by applying a set amount of pressure (measured in cmH20) into patient airways by mask. Think about the last time your siren stopped working and you stuck your head out the window to provide that "weeeee-wooooo" sound. The pressure you felt when you opened your mouth is similar to CPAP. Now while your partner is laughing uncontrollable, you are still able to inhale, exhale and make that "weeee-woooo" sound. CPAP uses air as a stent, keeping airways open while allowing inhalation and exhalation. ^1,3

BiPAP, as the name implies, provides inspiratory pressure (IPAP) and expiratory pressure (EPAP). IPAP is triggered when the patient "pulls negative pressure" (begins inspiration) and provides a set amount of pressure. A standard setting in pediatrics is 10 to 20cmH20. EPAP is equivalent to CPAP in providing a constant set pressure stenting the airway open. Recalling our earlier example with your head out the window and mouth open. Imagine your partner alternating between 60mph and 130mph, the slower speed is CPAP or EPAP and the faster equates to IPAP. The vehicle is always in motion and thus a constant state of pressure (EPAP/CPAP) is always present.

Physiologic Limits of NIPPV — Child Versus Machine

Each time we approach a patient in respiratory distress we should be asking ourselves a central question: Is this a ventilation, perfusion or diffusion problem? A ventilation problem revolves around air moving into and out of the lungs. Diseases that restrict or impeded this movement, such as asthma, foreign body aspiration and COPD fall into this category. Diffusion refers to gas exchange, is CO2 able to move from pulmonary circulation to alveoli and O2 from alveoli to pulmonary circulation. Alveoli in pneumonia are filled with infection and prevent or impeded diffusion. Finally, perfusion refers to adequate pump and vascular function. Is blood able to service the lungs properly. A pulmonary embolism creates a shunt, alveoli are bypassed from circulation preventing diffusion. Patients often have diffusion, perfusion and ventilation pathology concurrently. Understanding what we are treating on a cellular level allows us to target management. ^3,5

BIPAP has limits, based on disease pathology and patient. Before we review limitations, understanding pathophysiology of BIPAP is essential. Pressure in airways increases transpulmonary pressure consequently ventilating lungs. This in turn reduces right-to-left shunt, decreases work of breathing and reduces left ventricular (LV) transmural pressure, reducing afterload. Let's break this down one component at a time. A Right-to-Left shunt occurs when blood passes through pulmonary circulation without diffusion. This can transpire in various diseases and reduces red blood cells that grab oxygen and let go of CO2. Think about alveoli filled with pus/infection, despite having circulation no gas exchange takes place. BIPAP reduces "work," or metabolic expenditure of breathing, by reducing muscle involvement. Children use their diaphragm more than intercostal muscles. The diaphragm has fewer Type 1 muscle fibers compared to intercostal muscles. This is crucial because Type 1 muscle fibers provide less resistance to fatigue. Transmural LV pressure (LV afterload) is equal to left ventricle (LV) chamber pressure minus intrathoracic pressure (pressure in chest cavity). Intrathoracic pressure is normally a negative number as we breathe by negative pressure. When we increase intrathoracic pressure with BIPAP, this reduces LV afterload and improves cardiac function. Now that we understand BIPAP physiology, a review of limitations is necessary. ^3,5

BIPAP is able to provide 100% O2 and a fair amount of pressure to patients with settings similar to ventilation. Therapy also requires patient cooperation and no vomiting. Emesis during BIPAP carries a high probability of aspiration and subsequent sepsis. Prior to starting, patients need to be able to protect their airway and work with BIPAP and provider. Pediatric patients are susceptible to pneumothoaces with increased pressure and children can be difficult in starting this therapy. Children with poor lung or cardiac function prior to an acute illness may require intubation and mechanical ventilation. This is truly dependent on the patient and clinical picture. Children with a tracheostomy are candidates for BIPAP, however this is beyond prevue of this article. The decision to use BIPAP versus Intubation in the field is difficult and dependent on each clinical case. One significant advantage of BIPAP is pre-oxygenation for intubation. A child who is placed on BIPAP in hopes of rescue therapy declines, time spent on BIPAP provides superior oxygenation compared to Non-rebreather or Bag-valve-mask ventilation. It's now time for a review of indications for use.

Indications in EMS

Respiratory complaints in children are frequent and several commonly seen diseases with acute exacerbation will benefit from BIPAP therapy.

Asthma involves airway inflammation and restriction, complicated by bronchospasm. BIPAP provides an airway "stent" maintaining patency and provides oxygenation. Asthma exacerbations may last hours to days, with inflammation that requires mechanical ventilation. Early and aggressive intervention in acute asthma exacerbation who fail first-line treatments improves outcomes. This is the most common use of BIPAP in children and should be first line in patients who are not progressing, are high-risk and or have a poor predicted clinical outcome.⁴

Duchenne's, spinal muscular atrophy and congenital muscular dystrophy are three common neuromuscular diseases effecting respiration. While pathophysiology of these diseases differs, four main components altering respiration are universal. The ability to swallow and airway protection, upper airway weakness may cause obstructions (OSA), absent or ineffective cough prevents mucus clearing and a weak diaphragm reduces tidal volume. BIPAP works as "muscle" resolving these issues, albeit temporarily. An EMS provider encountering a patient a pulmonary problem (pneumonia) who has a neuromuscular disease may be a candidate for rescue BIPAP. ²

Cystic fibrosis (CF) is a genetic disorder affecting chloride that causes mucus to accumulate in airways leading to chronic cough, wheezing and frequent pulmonary infections. A CF child with a pulmonary infection often requires early and aggressive treatment to prevent intubation, including BIPAP.

Obstructive Sleep Apnea (OSA) is divided into central and obstructive. Central sleep apnea is a function of abnormal brain signals to respiratory muscles. Obstructive patterns in children often involves tonsils, adenoids and childhood obesity. OSA is more common in children with neuromuscular diseases, musculoskeletal abnormalities, down syndrome and cerebral palsy. A specific underlying condition is not "required" to deploy BIPAP, however the conditions above have data to support improved patient outcomes. ⁴

Equipment, Settings and Alarms

BIPAP's come in all shapes, sizes and capabilities, however main settings are detailed below and will be found on most units. Where do we start? Settings are based on clinical picture, however as a general guide, most patients on rescue therapy require 60-100% O2, a rate that correlates with age and pressure settings correlated to age and size. The following table details limits of pressure followed by definitions and alarms.

Age	EPAP Max	IPAP (5-10cm H20 over EPAP)
Infant	7-8cm H20	12-18cmH20
Toddler	8-10cm H20	13-20cmH20
Adolescent	10-12cm H20	15-20cmH20

IPAP - Inspiratory pressure, or the amount of support the device provides during inhalation.

IPAP - CO2 removal and chest expansion

EPAP - Expiratory pressure, or the amount of support the device provides when exhaling. This pressure helps to hold the throat and lung muscles more open to make the next breath easier.

EPAP - oxygenation — titrated off spo2

Rate - The minimum amount of ventilations in a minute the machine will deliver.

I-time - Inspiratory time, or the length of each breath. Most machines are set at a minimum and maximum time, in the range of ½ to 1 ½ seconds.

Trigger - Sensitivity at which the machine will detect negative pressure from the patient.

Rise Time - Amount of time for machine to change from EPAP to IPAP

Pressure Support - Equals IPAP-EPAP

FiO2 Expressed as a percentage of inhaled oxygen

Alarms

High pressure — Normally set 10cmH20 over IPAP
Low Pressure - Usually 0-3
Time delay — The amount of time before the alarm sounds
Apnea — Time of apnea before alarm sounds
- Infant 10-15 seconds
- Toddler 15-20 seconds
- Adolescent 20-30 seconds
Low Minute Volume — Least min volume before alarm will sound. It's always based on the patient.
High Respiratory Rate — Patient and machine rate
Low rate alarm — Minimum amount of respirations per minute

Sizing and Fitting

Obtaining a quality seal starts with mask selection. Three basic types of mask are available, nasal, nasal pillows and full mask, with multiple manufactures that supply various sizes in each. A facemask is often viewed as claustrophobic to patients, however, may provide a tighter seal (depending on anatomy). Nasal masks require less pressure and are associated with fewer apnea-hypopnea index (AHI). This is a measurement used in OSA sleep studies.

The manufacturer of each mask type provides a paper cutout for sizing patients and should be followed based on their recommendations. The nasal and nasal pillows mask is applied by placing them over the nose (into the nares) and allowing the patient to breathe through their mouth during fitting. BIPAP should be on and at low settings, allowing the patient to ease into pressure. The straps on the mask should be taunt without overtightening, avoiding pinching skin or pushing nose and face posterior. Face masks are applied by rolling the bottom of the mask up from chin to forehead and securing straps.

Once a mask is in place and BIPAP started check for leaks by listening for air and feeling air on the patients' face. Place a single finger on top of the mask at leak and push down gently until leak dissipates and secure mask again. All masks should be snug without excessive pressure. A mask with increased pressure on a child's face will cause pain, skin injury and possible skin breakdown.

Coaching the patient

A child in respiratory distress is often in a state of panic. The first step for first responders is do not panic. Take a deep breath and engage the child at their level. This means level eye-to-eye contact and speaking with reassurance. Explain the machine, mask and anticipated sensations. You may place the mask over their arm to allow them to feel air and pressure. Choose a mask, follow steps above and remain in close eye contact with the patient.

Returning to Jeremiah on the couch, BIPAP has been started at 15/7 and .60 with a rate of 12. After a few minutes he starts to relax and work with the BIPAP, you note a decrease in his work of breathing. He is moved to the cot and a second in-line nebulizer is started and EtCO2 rises to 32mmHg. Upon arrival in the ER the nurse comments "last time we had to intubate him." BIPAP is a valuable and underutilized tool in EMS, specifically in pediatric patients. The ability to prevent intubation and truly rescue a child is within our grasp. As EMS providers, we need to move toward educating, training and purchasing NIPPV for all patients.

References

Abramo, T., Williams, A., Mushtaq, S., et al. (2017). Paediatric ED BiPAP continuous quality improvement programme with patient analysis: 2005-2013. BMJ open, 7(1), e011845. doi:10.1136/bmjopen-2016-011845.
Ersu R, Narang I, Sockrider M, Breathing problems in children with neuromuscular diseases. American Thoracic Society. 2015.
Fedor K. Noninvasive respiratory support in infants and children. Respiratory Care. 2017; June Vol 62(6):699-717.
Lakusta,J., Duff, J., Novak,C. (2018) Non-invasive ventilation in pediatric medicine. PedsCases Podcast Script. http://pedscases.com/sites/default/files/NIV.pdf
Pediatric Acute Lung Injury Consensus Conference Group. Pediatric acute respiratory distress syndrome: consensus recommendations from the Pediatric Acute Lung Injury Consensus Conference. Pediatr Crit Care Med 2015;16(5):428-439.
Nucleus Medical Media. "Anatomy of Pediatric Airway with Severe Laryngomalacia." Nmal. 16 Sep 2013 7:46 EDT. Nucleus Medical Media. 20 Oct 2015.

Airway & Respiratory