Cough Assist Machine: How to Use It Step-by-Step

A cough assist machine, formally called a mechanical insufflation-exsufflation (MI-E) device, works by first pushing air deep into your lungs and then rapidly reversing to pull air out, mimicking the two phases of a natural cough. It is primarily prescribed for people whose respiratory muscles are too weak to cough effectively on their own, most often those living with neuromuscular conditions like ALS, muscular dystrophy, or spinal cord injuries.¹ Using the device correctly matters because small differences in technique, timing, and pressure settings can significantly affect how well it clears secretions. The steps themselves are straightforward once you understand the logic behind them.

What the Machine Actually Does to Your Lungs

A normal cough involves taking a deep breath in, briefly closing the vocal cords to build pressure, and then explosively releasing that pressure to blast air (and mucus) out of the airways. When the muscles responsible for breathing in or pushing air out are weak, each phase of this sequence suffers. The inhale is shallow, the pressure buildup is poor, and the expulsive force is too low to move secretions. Techniques like breath stacking, where you take several small breaths on top of each other before coughing, and manually assisted coughing can help, but they eventually stop being enough for some people.²

The cough assist machine replaces the weak muscles mechanically. During the insufflation phase, it delivers positive pressure to inflate the lungs more fully than the person could manage alone. During exsufflation, it rapidly switches to negative pressure, pulling air out at high speed and dragging mucus along with it. The swing from positive to negative pressure is what generates the cough-like airflow. One study found that unassisted cough peak flow in patients with respiratory muscle weakness averaged roughly 96 liters per minute, while MI-E alone brought that up to about 177 liters per minute.³ That jump can mean the difference between clearing a plug of mucus and leaving it sitting in the airway.

Step-by-Step Use With a Face Mask

Most people use the cough assist machine through an oronasal face mask, the kind that covers both the mouth and nose. Here is the general sequence, though your respiratory therapist may customize the details based on your condition and comfort.

Position yourself: Sit upright or recline at about 45 degrees. Being too flat makes it harder for secretions to travel upward and out. If you are in bed, raise the head of the bed.
Check the circuit: Make sure the tubing is connected from the machine to the mask (or tracheostomy adapter). Inspect the tubing for cracks or kinks. Attach a bacterial filter if your care team recommends one.
Set the pressures: The manufacturer’s recommended starting point is +40 cmH₂O for insufflation and −40 cmH₂O for exsufflation.⁴ In practice, clinicians often start lower and titrate upward, especially for first-time users or children.
Set the timing: Typical insufflation and exsufflation times each range from about one to four seconds. A common starting point is around two seconds for each phase, with a brief pause in between.
Apply the mask: Press the mask firmly against the face, creating a tight seal. Air leaks around the mask edges reduce the pressure reaching the lungs and weaken the cough effect. Some people find it easier to have a caregiver hold the mask in place.
Begin the cycle: Depending on the mode, the machine may cycle automatically or require you to trigger each breath manually. During insufflation, relax and let the air fill your lungs. During exsufflation, try to cough actively as the machine pulls air out. Coordinating your cough effort with the negative pressure phase boosts the peak flow.
Repeat in sets: A typical session involves four to six insufflation-exsufflation cycles, followed by a rest period of about 30 seconds to a minute. Repeat the cycle set two to four times, or until secretions are cleared and breathing feels easier.
Clear secretions: After each set, suction the mouth or have the person spit out any mucus that has been brought up. If using the device through a tracheostomy, suction through the tube as needed between sets.

The exact number of cycles and sets is not fixed. Your clinician will adjust the routine based on how much mucus you are producing, how tired you get during sessions, and whether you are using the machine for daily maintenance or to manage an acute respiratory infection.

Choosing Between Auto and Manual Mode

Most modern cough assist machines offer at least two modes. In automatic mode, the machine cycles through insufflation, exsufflation, and pause on its own according to the time settings you have programmed. In manual mode, the operator controls when to deliver each phase, typically by toggling a lever or pressing buttons. Some devices also offer a triggered mode, where the machine senses the patient’s own breathing effort and delivers insufflation in sync with it.

A survey of European centers treating children with neuromuscular disorders found that auto mode was used in about 71% of cases, triggered insufflation in about 21%, and manual mode in only 8%.⁵ Auto mode is convenient for home use because it frees up the caregiver’s hands and establishes a predictable rhythm. Manual mode gives more control over timing, which can be useful when a patient needs extra time on the insufflation phase or when coordinating with an abdominal thrust.

Getting the Pressure Settings Right

While the textbook starting point is symmetric pressures around +40/−40 cmH₂O, many patients end up on asymmetric settings where the insufflation and exsufflation pressures differ. In the European pediatric survey, asymmetric pressures were just as common as symmetric ones, and both insufflation and exsufflation pressures increased with the child’s age.⁵ Settings in that survey ranged from as low as +10 to as high as +50 cmH₂O on the insufflation side, and from −10 to −60 cmH₂O on exsufflation.

The timing of each phase matters too. Average insufflation and exsufflation times in pediatric clinical use were each roughly two seconds, but ranged from one to four seconds, and asymmetric timing was common. A longer insufflation time gives the lungs more time to fill, which can increase the volume of the subsequent cough. A slightly shorter exsufflation time makes the airflow faster and more forceful. Your respiratory therapist will adjust these variables based on what generates the best cough peak flow for you without causing discomfort.

There is a reason pressures are titrated carefully rather than simply cranked to maximum. Higher pressures do not always translate to better outcomes, and pushing too hard carries risks. In one case report, a patient developed bilateral pneumothorax on the third day after MI-E was introduced.⁶ Although pneumothorax from MI-E is rare, it illustrates why settings should be individualized rather than assumed from general recommendations.

Combining the Machine With Manual Techniques

You do not have to rely on the machine alone. Combining MI-E with a manual abdominal thrust, where a caregiver pushes firmly inward and upward on the abdomen during the exsufflation phase, can further boost cough effectiveness. In patients with respiratory muscle weakness, unassisted cough peak flow averaged about 96 L/min, MI-E alone brought it to roughly 177 L/min, and adding a manual thrust on top of MI-E pushed it up to about 202 L/min.³ That combination was the most effective strategy tested.

The technique requires coordination. The caregiver needs to time the abdominal thrust to coincide precisely with the machine’s switch from positive to negative pressure. Mistiming it, or pushing during insufflation, is counterproductive. This is one of the skills that benefits most from hands-on training with a respiratory therapist.

Using the Machine Through a Tracheostomy

When a patient has a tracheostomy, the cough assist machine connects directly to the tracheostomy tube instead of using a face mask. This eliminates the mask-seal problem but introduces a different one: the narrow bore of the artificial airway creates resistance that reduces the peak expiratory flow the machine can generate. Bench testing has shown that the narrower the inner diameter of the artificial airway, the lower the peak flow for a given expiratory pressure.⁷

Despite this limitation, MI-E can still be effective through a tracheostomy. A study measuring lung insufflation capacity and cough peak flow in patients with tracheostomies or glottic dysfunction found that assisted cough peak flows using the device were significantly higher than unassisted cough peak flows.⁸ The device essentially substitutes for the glottis’s role in building up pressure before a cough, which is relevant because many tracheostomy patients have compromised glottic function.

However, one study comparing different mechanically assisted coughing approaches found that in the tracheostomy group specifically, there were no significant differences between techniques, and cough peak flow did not increase as readily as it did in patients using a face mask.⁹ If you are using MI-E through a tracheostomy and it feels like it is not working well, this may be part of the explanation, and it is worth discussing with your care team whether adjusting settings or adding manual techniques might help.

What Happens in the Airway During a Cycle

One concern with MI-E is whether the rapid pressure changes cause anything unusual in the throat and larynx. Research using real-time imaging of the larynx during MI-E found that healthy participants showed normal airway responses: the vocal folds and surrounding structures opened (abducted) during both insufflation and exsufflation, with some tightening of the throat wall during exsufflation, which is a normal reflex. In some participants, the vocal folds moved inward (adducted) partway through a cycle, and some showed backward movement of the tongue base or epiglottis during insufflation.¹⁰

Why does this matter practically? If a patient seems to be gagging, choking, or not getting good airflow during MI-E, one possible explanation is that the upper airway structures are partially closing in response to the pressure. This can sometimes be addressed by lowering the inspiratory flow rate, adjusting the timing, or pausing to let the patient relax before the next cycle. If the problem persists, the clinician may need to investigate whether there is an underlying swallowing or laryngeal issue affecting how the airway responds.

Safety Concerns and Who Should Not Use It

MI-E is generally considered safe when used at appropriate settings, but certain conditions make it risky. People with a known or suspected pneumothorax, bullous emphysema (large air-filled sacs in the lungs prone to rupture), or recent barotrauma should not use the device without careful medical evaluation. The bilateral pneumothorax case mentioned earlier involved a hospitalized patient, and while the treating physicians noted the complication was rare, they recommended that clinicians specifically consider pneumothorax risk before initiating MI-E.⁶

During each session, monitoring heart rate, respiratory rate, and oxygen saturation is standard practice in clinical settings. One randomized trial in mechanically ventilated adults with pneumonia specifically tracked hemodynamic indices and blood gas parameters during cough assist use to ensure the device was not destabilizing the patients.¹¹ At home, you may not have full monitoring equipment, but a pulse oximeter is inexpensive and gives you a basic read on oxygen levels and heart rate. If oxygen saturation drops significantly during a session, or if the person develops chest pain or increased distress, stop the session and contact your healthcare provider.

How It Compares to Conventional Secretion Clearance

If you or a family member is being offered MI-E, you might wonder whether it is truly better than the alternatives. The evidence is mixed, depending on the population and what you are comparing it to. In mechanically ventilated adults, one study found that the volume of secretions cleared by the cough assist device versus conventional tracheal suctioning was not significantly different.¹² In children with cerebral palsy, MI-E did not shorten hospital stays overall compared to conventional chest physiotherapy, but among the subgroup with atelectasis (collapsed lung segments), therapy time was about a day shorter with MI-E, and no complications were observed.¹³

The real advantage of MI-E tends to show up in people whose cough is severely weak. When cough peak flow drops below a critical threshold, manual techniques alone cannot generate enough force to clear mucus effectively. MI-E fills that gap. For people with ALS and other progressive neuromuscular diseases, maintaining airway clearance helps prevent and treat respiratory tract infections, which are a major cause of hospitalization and decline.¹⁴

Comfort, Especially in Children

Comfort is not a minor issue. If the experience is unpleasant enough, people (especially children) may resist using the device, which defeats the purpose. Research on children with neurodisabilities found that different MI-E strategies produced notably different comfort scores. The strategy that generated the highest cough peak flow was also the least comfortable, with a mean comfort score of about 4.7 on a 10-point scale, compared to about 2.9 and 3.2 for gentler approaches.¹⁵ Using a lower inspiratory flow rate predicted improved comfort, though it also reduced the cough flow somewhat.

This creates a genuine trade-off. Clinicians and caregivers need to find the sweet spot where the settings are effective enough to clear secretions but tolerable enough for the person to cooperate session after session. In younger children, starting with lower pressures and slower flows and gradually increasing as the child acclimates often works better than jumping straight to the “optimal” clinical settings.

Training and Home Use

Most people learn to use the cough assist machine through a one-to-two-hour hands-on session with a clinician or respiratory therapist, either in the clinic or at home. A study of both new and established home MI-E users found that both groups were highly confident in using the device, rating their confidence around 8 to 9 out of 10. Users consistently rated hands-on practice and caregiver training as more valuable than written materials.¹⁶

The weak link, however, was follow-up. Most people in that study reported a lack of specific ongoing support, which left them uncertain about whether they were using the device correctly or whether it was actually working. This is a real gap in care. Over time, a person’s disease may progress, their settings may need adjustment, and their technique may drift. If you are using MI-E at home and have not had a follow-up review in a while, it is worth asking your respiratory clinic to reassess your settings and technique. The initial training session gets you started, but periodic check-ins keep the therapy optimized.

Adapting Settings for Children

Pediatric use of MI-E follows the same basic principles as adult use, but the settings need to be scaled down, and the evidence guiding those settings is thinner. The European survey of pediatric centers found that MI-E settings varied enormously: insufflation pressures ranged from +10 to +50 cmH₂O, and exsufflation pressures from −10 to −60 cmH₂O, across children aged from 4 months to nearly 18 years. Both pressures and timing increased with age.⁵ The authors specifically noted that pediatric guidelines for optimal MI-E settings are lacking, and the wide variation between centers reflects genuine uncertainty in the field.

For parents and caregivers of children using MI-E, this means that the settings prescribed by one clinic may differ substantially from what another clinic would recommend, and neither is necessarily wrong. The key is to work closely with your child’s respiratory team, observe how the child responds (both in terms of cough effectiveness and comfort), and communicate any concerns about tolerance. Higher insufflation pressure and older age were associated with higher cough peak flows in children, but higher pressures also reduced comfort in some kids, so the calibration is individual.¹⁵

Cleaning and Maintenance

The machine itself does not require much maintenance beyond wiping down the exterior and checking the filter. The tubing, mask, and any adapters, however, are in direct contact with airway secretions and need regular cleaning. Most manufacturers recommend washing these components in warm soapy water after each use, rinsing thoroughly, and allowing them to air dry. Bacterial filters should be replaced according to the manufacturer’s schedule, which is typically every one to two weeks or sooner if visibly soiled. If the device is shared between patients in a clinical setting, single-patient circuits and filters are standard infection-control practice.

Over time, tubing can become stiff or develop small cracks that create leaks. A leak in the circuit reduces the pressure reaching the lungs and weakens the cough effect, so it is worth inspecting the tubing periodically and replacing it when it starts to degrade. If the machine itself seems to be underperforming or making unusual sounds, contact the equipment supplier for a maintenance check rather than adjusting settings upward to compensate.

1
Journal of Clinical Medicine. Mechanical Insufflation-Exsufflation: Considerations for Improving Clinical Practice
2
European Respiratory Society (ERS). How to use a mechanical insufflator–exsufflator “cough assist machine”
3
Yonsei Medical Journal. A Comparison of Cough Assistance Techniques in Patients with Respiratory Muscle Weakness
4
PubMed Central. Setting Mechanical Insufflation-Exsufflation (MI-E) Pressures for Amyotrophic Lateral Sclerosis (ALS) Patients to Improve Atelectasis and Reduce Risk of Pneumothorax
5
PubMed. The clinical use of mechanical insufflation-exsufflation in children with neuromuscular disorders in Europe
6
Respiratory Medicine Case Reports. Mechanical insufflation-exsufflation-related bilateral pneumothorax
7
PubMed. Performance of the coughassist insufflation-exsufflation device in the presence of an endotracheal tube or tracheostomy tube: a bench study
8
Journal of Rehabilitation Medicine. Cough assistance device for patients with glottis dysfunction and/or tracheostomy
9
PubMed Central. Cough peak flow with different mechanically assisted coughing approaches under different conditions in patients with neuromuscular disorders
10
CHEST. Airflow Resistance and Pressure Transmission in the Upper Airway and Larynx During Mechanical Insufflation-Exsufflation
11
Immunopathopathology Perspectives. Effect of a cough assist device on hemodynamic status and oxygen saturation in mechanically ventilated adults with pneumonia
12
PubMed Central. Comparison of Mechanical Insufflation–Exsufflation and Endotracheal Suctioning in Mechanically Ventilated Patients: Effects on Respiratory Mechanics, Hemodynamics, and Volume of Secretions
13
PubMed. Mechanical Insufflation-Exsufflation Versus Conventional Chest Physiotherapy in Children With Cerebral Palsy
14
PubMed Central. Airway Clearance Strategies and Secretion Management in Amyotrophic Lateral Sclerosis
15
PubMed Central. Mechanically assisted cough strategies: user perspectives and cough flows in children with neurodisability
16
PubMed Central. Education Experiences of Adult Subjects and Caregivers for Mechanical Insufflation-Exsufflation at Home