People who have sustained a high spinal cord injury often need MV if the spinal cord has been injured at or about the fourth cervical vertebra (C4) or higher, and the respiratory muscles are paralyzed. After rehabilitation and special breathing exercises, some individuals are able to breathe on their own for short periods, but, generally, they must use a ventilator for the rest of their lives.

 

Some people with high spinal cord injuries choose diaphragmatic or phrenic pacing to assist their breathing. This involves an operation to implant electrodes on the phrenic nerves connected to wire leads implanted subcutaneously (under the skin). An external transmitter activates the leads to deliver stimulating pulses to the phrenic nerves, causing the diaphragm to contract. Thus, no ventilator is needed, although many keep the tracheostomy open for suctioning.

 

Adults with sleep-disordered breathing syndromes such as obesity hypoventilation (underventilation) or infants and children with congenital central hypoventilation syndrome (CCHS) need to use MV only during the night. Children with CCHS may also be good candidates for diaphragmatic pacing.

 

There are some people who have severe exacerbations of chronic obstructive pulmonary disease (COPD), such as emphysema or chronic bronchitis, or severe cardiopulmonary conditions such as congestive heart failure or cor pulmonale, whose breathing is helped by MV.

 

Some individuals who have had tuberculosis can also benefit from using MV.

A ventilator is the equipment used to mechanically assist breathing by delivering air to the lungs. Many people may be familiar with ventilators in the hospital setting, such as the ICU, where large complex acute care ventilators are used. The ventilators used in the home are small, lightweight and portable; they can be mounted on wheelchairs or carts or put on a bedside stand. Most of these operate on household electric current. Many have internal batteries, can be operated with external batteries, and newer models features “hot swappable” batteries, extending the time a ventilator user can be away home.  It is advisable to have a backup battery or even a generator readily available in case of power outages or emergencies.

How does MV work?

The diaphragm is the primary muscle for inspiration, along with the intercostal muscles between the ribs. Other muscles of the chest, neck and shoulders play smaller roles. When these breathing muscles are weakened or paralyzed, breathing becomes difficult or impossible. A mechanical ventilator can take over the act of breathing completely or make breathing easier by assisting weakened respiratory muscles.

 

The muscles of the abdomen are important for breathing out (expiration) and for an effective cough. Weak expiratory muscles result in impaired cough and inability to clear secretions that can lead to respiratory infections and pneumonias. In certain neuromuscular diseases, the bulbar muscles – those responsible for swallowing, speech and coughing – can become progressively impaired. Cough can be assisted with the use of manual and/or mechanical methods. There are several cough assists device available, e.g., Comfort Cough™ (Seoil Pacific Group); CoughAssist E70, CoughAssist T70 (Philips Respironics); Mini Pegaso A-Cough, Mini Pegaso A-Cough Perc, Pegaso Cough, Pegaso A-Cough Perc (Dima Italia S.r.l.); Nippy Clearway (B & D Electromedical); Pulsar (Siare Engineering International Group S.r.l.); The Vital Cough™ System (Hill-Rom). 

How did mechanical ventilation develop?

What is negative pressure ventilation?

When the pressure around the chest is negative – lower than atmospheric pressure – the chest expands to allow air to enter the nose and mouth. Iron lungs enclose the whole body, except for the head, and create pressure changes between the chest and the encasing shell of the unit. Other forms of negative pressure ventilation, also known as body ventilators, include the chest shell or cuirass, Nu-Mo suit and Pulmo-wrap. The Porta-Lung™ is a small and more mobile version of the iron lung. Today, some people still use an iron lung, chest shell or Porta-Lung™.

 

All negative pressure ventilation systems provide MV noninvasively to the body – no surgical operation, such as a tracheotomy, is necessary.

Positive pressure – higher than atmospheric pressure – pushes air into the lungs. It can be administered either noninvasively via a wide variety of nasal, facial and oral masks, nasal pillows (small cushions that fit into the nostrils), and mouthpieces – with tubing attaching to the ventilator or invasively via tracheostomy.

 

Positive pressure ventilators were developed as a more effective breathing option instead of the larger, bulkier negative pressure devices.

 

Examples of equipment that deliver positive pressure ventilation are bilevel positive airway pressure ventilators, pressure support ventilators, multi-mode or combination ventilators and volume-cycled ventilators. See IVUN’s Home Ventilator Guide. 

 

The high flow of air from positive pressure may cause dryness in the nasal passages and upper airway, and humidifiers may help relieve symptoms of nasal stuffiness, dry mouth and thick nasal secretions.

 

An integrated humidifier is a feature of some of the ventilators.

What is noninvasive positive pressure MV?

In noninvasive positive pressure MV, tubing connects the ventilator to the person via an interface. Interfaces include a wide range of nasal, oral or facial masks, nasal pillows (small cushions that fit into the nostrils), and mouthpieces, lipseals or other oral appliances. The nasal and facial masks can be custom-made.

 

The advantages of noninvasive MV: avoids the need to create an opening in the neck (tracheotomy) that may become a site for infection and irritation, permits normal speech and swallowing (if unaffected by the neuromuscular disease), preserves sense of taste and smell, and reduces need for attendant/personal assistance, family caregivers or nursing care related to MV.

 

Disadvantages include having the mouth and/or nose covered by the interface, possible upper airway obstruction, inability/claustrophobia in tolerating the mask, and safety issues if 24-hour MV is needed. Noninvasive MV may not be successful, or no longer work, when secretions are heavy and when there is progressive impairment of the muscles responsible for swallowing, speech and coughing, i.e., the bulbar muscles.

 

An effective cough to remove secretions is vital to the success of noninvasive MV. Cough can be assisted with the use of manual and/or mechanical methods. There are several cough assists device available, e.g., Comfort Cough™ (Seoil Pacific Group); CoughAssist E70, CoughAssist T70 (Philips Respironics); Mini Pegaso A-Cough, Mini Pegaso A-Cough Perc, Pegaso Cough, Pegaso A-Cough Perc (Dima Italia S.r.l.); Nippy Clearway (B & D Electromedical); Pulsar (Siare Engineering International Group S.r.l.); The Vital Cough™ System (Hill-Rom).

 

Noninvasive positive pressure ventilation is an option for short-term as well as long-term MV.

What is invasive positive pressure MV?

Invasive ventilation is via an endotracheal tube or a tracheotomy (a surgical opening in the windpipe to create an airway through which a tracheostomy tube is placed and connected by tubing to a positive pressure ventilator). Some individuals, such as those with ALS or muscular dystrophy, are unable to use noninvasive MV due to bulbar muscle impairment and/or may not find it as effective as invasive ventilation, particularly if 24-hour ventilation is needed. There are several types of tracheostomy tubes available.

 

The advantages of tracheostomy positive pressure ventilation include direct access to the upper airway, avoidance of upper airway obstruction, a face free of a nasal or facial mask, and a more secure and safer system when 16- to 24-hour support is needed.

 

Disadvantages include potential infection, irritation around the tracheostomy, increased secretions upon initiation, increased caregiving due to removal of secretions by suctioning or a mechanical cough device, and more expensive equipment and related supplies. Special attention is needed for speech, such as the use of a speaking valve.

What is sleep-disordered breathing?

People with weak respiratory muscles often experience breathing abnormalities during sleep as the first indication of a problem. Signs include frequent arousals and fragmented sleep, and a reduction in the quality and efficiency of sleep. Underventilation typically occurs during REM sleep, leading to decreases in the level of oxygen saturation and increases in the carbon dioxide in the blood.

 

Apneas and hypopneas also occur. Apneas are defined as brief episodes when air stops moving in and out of the lungs during sleep for at least ten seconds; hypopneas are episodes when air movement is present but reduced. Some apnea episodes are considered normal; up to five per hour, but an increase in apnea episodes to more than ten per hour indicates the need for evaluation and treatment.

 

Obstructive sleep apnea (OSA), which is common in the general population, occurs when tissues in the throat collapse, intermittently blocking airflow during sleep. Central sleep apnea occurs when the brain fails to send appropriate signals to the body to initiate breathing, and there is neither airflow nor chest movement. Mixed apnea is a combination of central and obstructive factors occurring in the same episode of sleep apnea.

 

When sleep apnea is suspected, a sleep study in a sleep laboratory or through home sleep studies can confirm the diagnosis. In people with sleep apnea, the standard treatment is CPAP.

 

Individuals with respiratory muscle weakness who are experiencing nocturnal breathing problems should be evaluated by a pulmonologist who is experienced in neuromuscular disease to determine whether the cause of the problems is underventilation or sleep apnea or both. Underventilation is optimally managed with MV.

What is CPAP?

CPAP (continuous positive airway pressure) units provide a continuous flow of air under the same level of pressure during inhalation and exhalation to help keep the airway open. CPAP is the standard treatment for obstructive sleep apnea; however, it does not assist with breathing and is not considered ventilation. New auto-titrating CPAP units deliver varying levels of pressures based on the detection of sleep-disordered breathing events and can change pressure on a breath-by-breath basis.

What is a bilevel positive airway pressure ventilator?

Bilevel ventilators were developed by modifying CPAP to also provide inspiratory positive airway pressure (IPAP) to assist inspiration (breathing in). IPAP and expiratory positive airway pressure (EPAP) settings are adjusted separately. People with neuromuscular disease and weak diaphragmatic muscles often may have difficulty breathing in and need IPAP set higher than EPAP, e.g., an IPAP of 14 and an EPAP of 3. The difference between IPAP and EPAP is called the span, and in these cases should be at least 10.

 

Bilevel units are made by several manufacturers and are often generically referred to as BiPAP. The only bilevels that can be called BiPAP® are the units patented and registered by one manufacturer.

 

Bilevels are used primarily at night with a nasal, facial or oral mask, or nasal pillows. The FDA has not approved them for off-label use by people with tracheostomies.

 

Three modes are available with bilevel ventilators:

 

1. "S" or spontaneous breathing patterns that are sensed so that the unit switches between prescribed pressures;
    

2. "T" or timed mode that delivers IPAP and EPAP at a predetermined breathing rate;
    

3. "S/T" or spontaneous/timed that operates in spontaneous mode, but switches to timed mode (referred to as a backup rate) when breaths are not initiated by the individual.

 

People with neuromuscular disease should use a bilevel ventilator with a backup rate that can initiate breaths, particularly at night.

 

The advantages of bilevel ventilators are small size, light weight, lower cost and compensation for interface leaks. The disadvantages include lack of internal batteries, fewer alarms, and inadequate pressures for some people, use of more electricity to operate and discomfort from EPAP.

 

Examples include BiPAP AVAPS (Philips Respironics Inc.) and VPAP™ III ST-A with iVAPS (S9) (ResMed Corp.)

Volume-cycled ventilators deliver a preset volume of air during inspiration. Volume ventilators can deliver higher volumes and pressures than bilevel units, although the volume remains constant despite leaks. The pressure limit can be adjusted by increasing the volume and lowering the high-pressure alarm.

 

Volume-cycled ventilators can be used for breath stacking (adding one breath to another without exhaling) to enable deeper breaths for improved cough. They also have multiple alarms and internal batteries, but they are larger, heavier and more expensive than bilevel units, although they generally use less electricity to operate. If an individual needs 24-hour ventilation, a volume ventilator is recommended because it is approved by the FDA for this purpose and has the needed safety features.

 

Examples include LTV® 1100 (CareFusion BD) and the UniVent™ Eagle™ 754 (ZOLL).  The popular volume ventilators PLV®-100 (Respironics Inc.) and LP10 (Puritan Bennett) have been discontinued.

What is a pressure support ventilator?

Pressure support ventilators supplement the inspiratory effort of individuals who can breathe spontaneously by providing a preset amount of positive airway pressure throughout the complete inspiration. The tidal volume can vary from breath to breath. These ventilators also offer pressure control with the ventilator rather than the individual controlling the breathing rate.

 

Examples include Stellar™ 100, Stellar™ 150 (ResMed Corp.) and Vivo® 30, Vivo®40 (Breas).

What is a multi-mode ventilator?

The latest generation of ventilators, multi-mode, can provide many modes of ventilation, such as pressure support, pressure control, volume control, assist/control, SIMV (synchronized intermittent mandatory ventilation), bilevel pressure or CPAP.

 

Examples include LTV® series (CareFusion BD), HT50®, HT70, HT70+ (Newport Medical Instruments, a division of Covidien), iVent 201® (GE Healthcare), Trilogy 100, 200, 202 (Philips Respironics Inc).

The choice of a ventilation system in infants and children involves several factors such as the child's age; degree of respiratory impairment; need for positive end expiratory pressure (PEEP), pressure support and higher respiratory rates; and the resources and support systems at home.