Noninvasive Ventilation Procedures Technique

Updated: Apr 26, 2018
  • Author: Suneel Kumar Pooboni, MD, , FRCPCH, FRCP(Edin), FCCP; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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Technique

Approach Considerations

Noninvasive ventilation (NIV; see the video below) is a popular method of adult respiratory management in both the emergency department (ED) and the intensive care unit (ICU), and it is increasingly used in the care of pediatric patients. NIV is divided into two main types: negative-pressure ventilation (NPV) and noninvasive positive-pressure ventilation (NIPPV). NIPPV is further subdivided into continuous positive airway pressure (CPAP) and bilevel positive airway pressure (BiPAP).

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

The following should be kept in mind in the provision of NIV:

  • NIV should ensure maintenance of functional residual capacity (FRC)
  • NIV should be the first line of respiratory therapy for carefully selected clinical problems
  • NIV helps avoid associated adverse side effects of invasive ventilation (eg, ventilator-associated pneumonia, excessive sedation, barotrauma, and volutrauma)
  • Vital signs, clinical profile, and blood gases should be monitored carefully, especially in the first few hours after initiation of NIV; this allows early recognition of signs of lack of improvement and timely consideration of the need for intubation in selected cases
  • NPV mimics physiologic ventilation
  • Heliox therapy may be useful in patients with a selected group of obstructive airway diseases (eg,  reactive airways disease)
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Noninvasive Positive-Pressure Ventilation

Because of its versatile applications, NIPPV is currently used for respiratory diseases, neuromuscular diseases, chronic obstructive pulmonary disease (COPD), congestive heart failure (CHF), and diaphragmatic weakness. [9, 10, 11, 12, 13, 14, 15, 16]  It 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. [17, 18]  Ease of administration and portability, as well as the ability to eliminate obstructive sleep apnea (OSA), make NIPPV the first choice among NIV modes.

NIPPV is most often begun in the ED, and acute pulmonary edema and exacerbation of COPD are the most common indications. [19]  However, NIPPV is also used in the 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 surgery has been shown to improve oxygenation after extubation as compared with nasal oxygen alone. [20]

Continuous positive airway pressure

Ventilator mode

A 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 (eg, in acute pulmonary edema). It prevents alveolar collapse and facilitates oxygen delivery to pulmonary capillaries. CPAP increases the FRC and opens collapsed alveoli, and this, in turn, enhances gas exchange and oxygenation.

CPAP reduces left ventricular transmural pressure, thereby 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 H2O. 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, who may become hemodynamically unstable; one of the disadvantages of CPAP is reduced venous return.

In the ED and the ICU, CPAP is generally administered via a face mask, with a seal created over the mouth and nose (see the images below). In some cases, however, a smaller mask can be used that covers just the nose. For patients who require CPAP at home on a nightly basis because of nocturnal hypoxemia due to episodes of OSA, 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 adult patient.
Continuous positive airway pressure (CPAP) adminis Continuous positive airway pressure (CPAP) administered on child.

Bilevel positive airway pressure

Ventilator mode

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 involves the following three modes:

  • 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
  • BiPAP - The ventilator delivers different pressures during inspiration and expiration; if necessary, this mode can fully ventilate the patient

Use

BiPAP provides two forms 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 also adds inspiratory assistance that may further reduce the work of breathing and assist with augmenting the ventilator in patients at risk for hypercapnia (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 settings of 10-12 cm H2O for IPAP and 5-7 cm H2O for EPAP and then to adjust IPAP to 15-20 cm H2O, 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. Backup rates can be chosen according to the age of the patient. The fraction of inspired oxygen (FiO2) 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.

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Negative-Pressure Ventilation

The prototypical NPV device was the iron lung (see the image below), which was first used in 1928 but is best known for its role during the polio epidemics of the 1950s.

Iron lung. Photo courtesy of Kansas Historical Soc Iron lung. Photo courtesy of Kansas Historical Society.

The Hayek oscillator (see the image below) is a more recently developed NPV device that applies high-frequency oscillation by using an airtight cuirass (a jacket of flexible foam sealed to fit around the chest and abdomen). [21]  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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Heliox Adjunct Therapy

The medical use of heliox (a low-density misture of helium and oxygen) as a breathable gas in the treatment of 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. [22]

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, heliox, or both.

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 COPD exacerbations. Jaber et al demonstrated that administering heliox during noninvasive pressure support ventilation led to improvements in pH level, arterial oxygen tension (PaCO2), and work of breathing in patients with acute exacerbation of COPD. [23]  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 decreased the work of breathing in patients with COPD who were mechanically ventilated. [24]  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 significant cost implications, in that the heliox cylinders (see the images 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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Complications

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.

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

It is extremely important for the air seal to be tight, and the skin may be affected. Most complications are related to local skin effects, especially with long-term use. 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.

Distention of the stomach due to aerophagia and aspiration secondary to vomiting during NPV are additional concerns. When gastric distention occurs, a nasogastric tube can be used to relieve the distention while still allowing the mask to seal.

Adverse hemodynamic effects from NPV are unusual, though preload reduction and hypotension may occur. [25, 24]

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