Noninvasive Ventilation Procedures

Updated: Dec 21, 2015
  • Author: Suneel Kumar Pooboni, MD, , FRCPCH, FRCP(Edin), FCCP; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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Overview

Overview

Noninvasive ventilation (NIV) can be defined as a ventilation modality that supports breathing without the need for intubation or surgical airway. Noninvasive ventilation (see the video below) is a popular method of adult respiratory management in both the emergency department and the intensive care unit (ICU), and it has gained increasing support in the care of pediatric patients. Besides avoiding the adverse effects of invasive ventilation, noninvasive ventilation has the added advantage of patient comfort. Noninvasive ventilation delivers mechanically assisted breaths without the placement of an artificial airway and has become an important mechanism of ventilator support both inside and outside the ICU. [1, 2, 3]

Noninvasive Ventilation. Video courtesy of Therese Canares, MD, and Jonathan Valente, MD, Rhode Island Hospital, Brown University.

Noninvasive ventilation is further subdivided into negative pressure ventilation (NPV) and noninvasive positive pressure ventilation (NIPPV); the latter includes continuous positive airway pressure (CPAP) and bilevel positive airway pressure (BiPAP). This article addresses all of these methods and briefly discusses heliox therapy.

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Indications

Neonates and infants

Noninvasive ventilation (NIV) is indicated in neonates and infants as follows:

  • Weaning from ventilator
  • Preventing collapse of the lung
  • Minimal need for respiratory support, with good respiratory drive

Pediatric

Noninvasive ventilation (NIV) is indicated in pediatric patients as follows:

Adults

Noninvasive ventilation (NIV) is indicated in adults patients as follows:

  • Bilateral pneumonia
  • Acute congestive heart failure with pulmonary edema
  • Neuromuscular disorders
  • Acute lung injury
  • Weaning from ventilator (A 2009 meta-analysis indicated that noninvasive ventilation, as a method of weaning critically ill adults from invasive ventilation, was significantly associated with reduced mortality and ventilator-associated pneumonia. The net clinical benefits of this method have not yet been determined. [5] )
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Contraindications

Absolute contraindications

Absolute contraindications to noninvasive ventilation are as follows:

  • Respiratory arrest or unstable cardiorespiratory status
  • Uncooperative patients
  • Inability to protect airway (impaired swallowing and cough)
  • Trauma or burns involving the face
  • Facial, esophageal, or gastric surgery
  • Apnea (poor respiratory drive)
  • Reduced consciousness

Relative contraindications

Relative contraindications to noninvasive ventilation are as follows:

  • Extreme anxiety
  • Morbid obesity
  • Copious secretions
  • Need for continuous or nearly continuous ventilatory assistance
  • Lack of respiratory drive
  • Diseases with air trapping, such as asthma (In a child on continuous positive airway pressure (CPAP) therapy, periodic monitoring is required. If the clinical condition and arterial blood gases deteriorate despite CPAP support, intubation should be considered.)
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Anesthesia

Mild sedation and analgesia may be required to keep the patient comfortable.

Anxiolytics may be helpful for patients experiencing claustrophobia due to the facial mask or for patients with increased respiratory rates secondary to anxiety.

However, extreme caution must be exercised when using sedative agents in the setting of respiratory difficulty, as it may depress respiratory drive and lead to hypercarbia or respiratory failure, thereby requiring intubation. The respiratory effort of the patient must be maintained.

Patients generally are cooperative and do well with explanation of the application procedure.

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Equipment

Available drivers/ventilators

  • Ventilators (examples shown in the images below)
    Bilevel positive airway pressure (BiPAP) vision ve Bilevel positive airway pressure (BiPAP) vision ventilator.
    NIPPY ventilator (B&D Electromedical, Warwickshire NIPPY ventilator (B&D Electromedical, Warwickshire, UK).
  • Negative pressure ventilator

Interface appliances

  • Nasal/nasopharyngeal prongs (examples shown in the images below)
    Nasal and nasopharyngeal prongs for continuous pos Nasal and nasopharyngeal prongs for continuous positive airway pressure (CPAP).
    Nasal prongs. Nasal prongs.
  • Nasopharyngeal tube for continuous positive airway pressure (CPAP), as shown below
    Continuous positive airway pressure (CPAP) tubing. Continuous positive airway pressure (CPAP) tubing.
  • Nasal mask
  • Face mask
  • Head mask, as shown below
    Head mask as interface. Head mask as interface.
  • Cuirass, as shown below
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Positioning

Noninvasive positive pressure ventilation (NIPPV) setup

Positioning for facemask or nasal mask application is as follows [6] :

  • Seat the patient in a bed or chair in a 30-90 º upright position.
  • Position the mask so that the nasal portion of the mask fits just above the junction of the nasal bone and cartilage.
  • A strap is needed to maintain correct position of most interfaces and is important for patient comfort. Simple disposable Velcro straps are most often used. Fasten the straps so that 1-2 fingers can pass between the headgear and the face. Take note that erosion of nasal bridge and nasal cartilage can occur with long-term use.

Positioning for nasal prong application is as follows:

  • Nasal prongs should fill the nasal openings completely without stretching the skin or putting undue pressure on the nares. The corrugated tubing should not be touching the patient’s skin.
  • Make sure no lateral pressure is exerted on the septum; such pressure could pinch or twist the septum.

Consider the following when stting up the machine:

  • Humidifier: Use a disposable humidifier top with a 1-L bag of water attached. Adequate humidity prevents drying of secretions.
  • Oxygen flow: A gas flow of 6-10 L/min is delivered via a blender. This amount of gas flow provides adequate pressure to wash out carbon dioxide in the system, compensate for normal air leakage from tubing connections, and generate adequate pressure.
  • Occlude the pressure line connection port with the white plug provided. This completes the NIPPV circuit.
  • For continuous positive airway pressure (CPAP), set the default pressure at 4-6 cm H 2 O. Pressures of 10 cm H 2 O or greater may be used on an individual basis, depending on the patient's pathophysiology. Remember to check the water level and adjust for evaporation, as required.
  • For bilevel positive airway pressure (BiPAP), common settings are inspiratory positive airway pressures (IPAP) of about 15 cm H 2 O and expiratory positive airway pressures (EPAP) of about 5 cm H 2 O. See the BiPAP section below for more details.
  • Suction the airway, if needed, prior to application of facemask.
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Technique

Noninvasive positive pressure ventilation

Because of its versatile applications, noninvasive positive pressure ventilation (NIPPV) is currently used for respiratory diseases, neuromuscular diseases, chronic obstructive pulmonary disease (COPD), congestive heart failure (CHF), and diaphragmatic weakness. [7, 8, 9, 10, 11, 12] NIPPV should be used to help buy time while other modalities are used to correct underlying medical problems. It may be used to delay or avoid tracheal intubation in some patients with acute respiratory distress. [13, 14] Ease of administration and portability, as well as the ability to eliminate obstructive sleep apneas, make NIPPV the first choice among noninvasive ventilation (NIV) modes.

Therapy with NIPPV is most often begun in the emergency department (ED), and acute pulmonary edema and exacerbation of COPD are the most common indications. [15] However, NIPPV is also used in the intensive care unit (ICU) setting for acute respiratory failure. Additional uses have included weaning patients from invasive ventilation. NIPPV with BiPAP in patients who have undergone cardiac bypass or valve repair surgeries has been shown to improve oxygenation after extubation as compared to nasal oxygen alone. [16]

Continuous positive airway pressure

Ventilator mode

  • A continuous positive airway pressure (CPAP) ventilator delivers air at a constant pressure during inspiration and expiration.
  • The patient must be able to breathe spontaneously.

Use

  • CPAP is mainly used for hypoxemic respiratory failure, such as in acute pulmonary edema. It prevents alveolar collapse and facilitates oxygen delivery to pulmonary capillaries. CPAP increases the functional residual capacity (FRC) and opens collapsed alveoli, which, in turn, enhances gas exchange and oxygenation.
  • CPAP reduces left ventricular transmural pressure, therefore increasing cardiac output. Hence, it is very effective for treatment of acute pulmonary edema and is considered the modality of first choice in these patients. Pressures usually are limited to 5-15 cm of H 2 O. Each patient’s requirements must be reviewed in light of his or her disease process and disease pathophysiology. Caution is advised in patients with borderline low blood pressure; they may become hemodynamically unstable, as one of the disadvantages of CPAP is reduced venous return.
  • In the ED and ICU, CPAP is generally administered using a facemask, creating a seal over the mouth and nose, as shown in the images below. However, a smaller mask can be used in some cases, covering just the nose. For patients who require CPAP at home on a nightly basis because of nocturnal hypoxemia due to episodes of obstructive sleep apnea, nasal prongs provide a pneumatic splint that holds the upper airway open. CPAP provides positive airway pressure throughout all phases of spontaneous ventilation.
    Continuous positive airway pressure (CPAP) adminis Continuous positive airway pressure (CPAP) administered on an adult patient.
    Continuous positive airway pressure (CPAP) adminis Continuous positive airway pressure (CPAP) administered on a child.

Bilevel positive airway pressure

Ventilator mode

  • Bilevel positive airway pressure (BiPAP) is pressure-limited ventilation. Predetermined inspiratory pressure is delivered, which can cause different tidal volumes, depending on the resistance of the respiratory system. BiPAP has the advantage of leak compensation. It is preferred for most short-term applications because pressure-limited modes are better tolerated than volume-limited modes.
  • BiPAP comes in the following 3 types:
    • Pressure support: The ventilator delivers air at a set pressure during inspiration each time a patient initiates a breath.
    • Pressure control: The ventilator automatically delivers a set number of breaths per minute at a set pressure.
    • Bilevel positive airway pressure: The ventilator delivers different pressures during inspiration and expiration. If necessary, this mode can fully ventilate the patient.

Use

  • BiPAP provides 2 levels of positive pressure: inspiratory positive airway pressure (IPAP) and expiratory positive airway pressure (EPAP). This is highly beneficial in patients with respiratory fatigue or failure. During exhalation, pressure is variably positive. Airflow in the circuit is sensed by a transducer and is augmented to a preset level of ventilation. Cycling between inspiratory and expiratory modes may be triggered by the patient's breaths or may be preset. BiPAP helps in improving patient comfort.
  • BiPAP is a particularly effective respiratory modality when patients are not improving sufficiently on CPAP alone. Not only does it provide the benefit of CPAP by providing increased airway pressure during expiration, but it adds inspiratory assistance that may further reduce the work of breathing and assist with augmenting the ventilator in patients at risk for hypercapnea (eg, patients with COPD).
  • Patients may tire from breathing against resistance, even as it helps prevent alveoli from closing.
  • A common practice is to use initial IPAP settings of 10-12 cm H 2 O pressure and EPAP settings of 5-7 cm H 2 O, and then adjust IPAP to 15-20 cm H 2 O, depending upon the response over the next hour or so.
  • In conditions such as lung collapse or pulmonary edema, the initial EPAP may have to be high. However, an EPAP that is too high can lead to reduced preload. Hence, a balance in adjusting the ventilatory settings is desirable. Back-up rates can be chosen according to the age of the patient. The fraction of inspired oxygen (FiO 2) is another useful variable in titrating the response to oxygenation.

Volume-limited ventilation

Ventilator mode

  • In volume-limited ventilation, a predetermined tidal volume or minute volume is delivered each time a patient takes a breath.
  • This leads to varying peak inspiratory pressures, depending on the resistance of the respiratory system.

Use

  • In this mode, ventilators usually are set in assist-control mode with high tidal volume (10-15 mL/kg) to compensate for air leaks. Interfaces can be selected to suit the comfort of the patient.
  • This mode is suitable for obese patients or patients with chest wall deformities (ie, patients who need high inflation pressure) and for patients with neuromuscular diseases who need high tidal volumes for ventilation.

Negative pressure ventilation

The prototype negative pressure ventilation (NPV) was the iron lung, shown below, which was first used in 1928 but most famously used during the polio epidemics of 1950s.

Iron lung (photo courtesy of Kansas Historical soc Iron lung (photo courtesy of Kansas Historical society).

A Hayek oscillator, shown below, is a more recently developed negative pressure ventilator that applies high-frequency oscillation by using an airtight cuirass (a jacket of flexible foam sealed to fit around the chest and abdomen). [17] It is designed to provide negative pressure during inspiration and positive pressure during expiration, creating controlled ventilation, including high-frequency chest wall oscillation.

Hayek oscillator. Hayek oscillator.
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Pearls

Pearls include the following:

  • Noninvasive ventilation should ensure maintenance of functional residual capacity.
  • Noninvasive ventilation should be the first line of respiratory therapy in carefully selected clinical problems.
  • Noninvasive ventilation helps avoid associated adverse side effects of invasive ventilation (eg, ventilator-associated pneumonias, excessive sedation, barotrauma, and volutrauma).
  • Vital signs, clinical profile, and blood gases should be monitored carefully, especially in the first few hours after initiating noninvasive ventilation therapy. This allows early recognition of signs of lack of improvement and timely consideration of the need for intubation in selected cases.
  • Negative pressure ventilation mimics physiological ventilation.
  • Heliox therapy may be useful in patients with a selected group of obstructive airway diseases such as reactive airways disease.
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Complications

Noninvasive positive pressure ventilation (NIPPV) has relatively few complications when compared with invasive ventilation.

Patients must be monitored carefully for worsening respiratory distress, tachypnea, and deteriorating blood gases.

Inadequate clearance of respiratory secretions may pose a problem, especially since the seal must be maintained.

Noninvasive ventilation (NIV) should be used with extreme caution in patients with pulmonary processes (eg, a lobar pneumonia) that affect only one side of the lungs. Note the following:

  • In such cases, NIV primarily ventilates the good lung, producing increased pressure on that side, which leads to decreased blood flow to the healthy lung and increased pulmonary blood flow to the affected lung, or area of lower pressure.
  • This can lead to a relative decrease in gas exchange.

As it is extremely important for the air seal to be tight, most complications are related to local skin effects, especially with long-term use. Note the following:

  • These include ulceration and pressure necrosis at the application sites of appliances such as masks, straps, or nasal prongs.
  • Protective synthetic coverings (eg, CombiDERM ACD, ConvaTec DuoDERM CGF control gel formula dressing) may help prevent skin breakdown and ulceration on the bridge of the nose.
  • Eye irritation and pain or congestion of the nasal sinuses may occur.

Distension of the stomach due to aerophagia and aspiration secondary to vomiting while on negative pressure ventilation (NPV) are additional concerns. Note the following:

  • When gastric distension occurs, a nasogastric tube can be used to relieve the distension while still allowing the mask to seal.
  • Adverse hemodynamic effects from NPV are unusual, although preload reduction and hypotension may occur. [18, 19]
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Noninvasive Ventilation and Heliox Adjunct Therapy

The medical use of heliox as a breathable gas for respiratory disease was first introduced in 1934 by Barach. Since then, heliox has been studied in various upper and lower airway conditions by many investigators. Vineet et al conducted a computerized bibliographic search of available clinical material on the properties of helium and its applications in pediatric intensive care. [20]

Noninvasive positive pressure ventilation (NIPPV) can be used to treat patients with upper airway obstructions such as those caused by glottic edema following extubation. In this situation, NIPPV can be combined with aerosolized medication and/or heliox.

Heliox administration is most effective in conditions involving density-dependent increases in airway resistance, especially when used early in an acute disease process. Substituting helium for nitrogen in a gas mixture changes the physical properties of the inhaled gas, decreasing gas density and increasing laminar air flow in the airway.

Heliox therapy also appears to be beneficial in chronic obstructive pulmonary disease (COPD) exacerbations. Jaber et al demonstrated that heliox during noninvasive pressure support ventilation improved pH level, PaCO2 level (partial pressure of carbon dioxide in arterial gas), and work of breathing in patients with acute exacerbation of COPD. [21] It may also improve clinical tolerance and potentially further reduce the need for invasive ventilation in selected patients.

Gainnier et al reported that in their randomized, prospective study in adults, the helium-oxygen mixture decreases the work of breathing in patients with COPD who are mechanically ventilated. [19] Hence, the helium-oxygen mixture may be useful in reducing the burden of ventilation.

For effective results, heliox should be used in a combination ratio of 60 parts helium to 40 parts oxygen or 79 parts helium to 21 parts oxygen.

Heliox can be administered as a nebulization or via ventilator, though not all ventilators have the ability to add heliox.

Some of the medical conditions in which heliox may be useful include the following:

Continuing heliox therapy for hours has cost implications, as the heliox cylinders (shown below) run out reasonably quickly. Any beneficial effect of heliox should become evident in a relatively short period.

Heliox cylinders. Heliox cylinders.
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