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A cough only works if you can take a big breath in, close your throat, and push hard. Illness or injury affecting the breathing muscles can take away one or more of those steps, and mucus then stays in the lungs and turns into a chest infection. An assisted cough supplies the missing part — someone pushes on your tummy or ribs as you cough, or a machine gives you a bigger breath first. Glossopharyngeal breathing, sometimes called frog breathing, is a skill you can learn yourself: you gulp air with your mouth and tongue, stacking several gulps to fill your lungs before you cough. Both are taught by a physiotherapist, and both work best when you and your family have practised them before you get sick.
Definition
An assisted cough is any technique that supplies the part of the cough a person can no longer generate themselves — either the deep breath in, or the force of the push out, or both. Glossopharyngeal breathing (also called frog breathing, or GPB) is a self-directed technique in which the mouth, tongue and throat are used as a pump to gulp air into the lungs, stacking several mouthfuls on top of one another to reach a volume the breathing muscles alone could never achieve.
Both belong to the same clinical problem: a cough that is too weak to clear the airway. Neither is a treatment for the underlying disease. They are mechanical substitutes for muscle, and for people with progressive neuromuscular conditions they are among the interventions that most directly prevent hospital admission.
How a normal cough works
An effective cough has four phases, and weakness in any one of them will reduce the result:
| Phase | What happens | Muscles | What goes wrong |
|---|---|---|---|
| Inspiration | A deep breath to 85–90% of total lung capacity, putting the expiratory muscles on stretch and storing elastic recoil | Diaphragm, external intercostals, accessory muscles | Inspiratory weakness — a small breath in means a weak cough out, however strong the abdominals |
| Compression | The glottis closes for about 0.2 seconds while the expiratory muscles contract, raising intrathoracic pressure | Vocal folds, abdominals | Bulbar weakness — the glottis cannot seal, so no pressure builds |
| Expulsion | The glottis opens and air leaves at high velocity, shearing mucus off the airway wall | Abdominals, internal intercostals | Expiratory weakness — the classic reason peak cough flow falls |
| Relaxation | Recoil and the next breath reposition secretions further up the airway | — | Fatigue — the second and third coughs are weaker than the first |
Airway clearance is not achieved by a single heroic cough but by a sequence: the mucus is walked up the bronchial tree over several efforts. This is why a person who can produce one adequate cough but fatigues immediately is still at risk.
Measuring a weak cough
Peak cough flow (PCF) is the single most useful measurement, taken with a peak flow meter and a mask or mouthpiece during a maximal cough effort. Two thresholds guide practice:1,2
- Below 270 L/min — the cough is adequate when well, but will fail during a chest infection, when secretions increase and muscle strength falls. This is the point at which assisted cough techniques should be taught, and equipment considered, before they are needed.
- Below 160 L/min — the cough is inadequate to clear the airway at all. Mechanical assistance is required, and this threshold also predicts failure of extubation and of decannulation.
Maximal inspiratory and expiratory pressures, vital capacity (including supine vital capacity, which unmasks diaphragm weakness) and maximum insufflation capacity complete the picture. A drop of more than 20% in vital capacity from sitting to supine points to diaphragmatic involvement.
Who needs cough assistance
- Neuromuscular disease — Duchenne and other muscular dystrophies, spinal muscular atrophy, motor neurone disease/ALS, myasthenia in crisis, Guillain–Barré syndrome, post-polio syndrome.
- Spinal cord injury — particularly at or above T6, where the abdominal muscles are wholly or partly denervated. Cervical injuries lose intercostal support as well.
- Advanced restrictive chest wall disease — severe kyphoscoliosis, thoracoplasty.
- Critical illness and prolonged ventilation — ICU-acquired weakness produces exactly the same mechanical failure, usually reversibly.
- Post-operative and post-traumatic pain — where the cough is inhibited rather than weak. Here analgesia is the primary treatment and manual support is an adjunct; see flail chest and sternal precautions.
Manually assisted cough
The physiotherapist (or a trained carer) adds an external force to the expulsive phase, timed precisely to the patient's own effort. The patient takes the deepest breath they can, or is given one by a resuscitation bag, ventilator or mechanical insufflator; on their cue — usually a spoken “one, two, cough” — the assistant compresses.
The three common hand placements
- Abdominal thrust — the heel of the hand or the forearm on the abdomen below the xiphisternum, with an inward and upward thrust as the patient coughs. The most effective placement for isolated abdominal weakness. Avoid immediately after abdominal surgery, in pregnancy, with an unstable spine, or where an inferior vena cava filter has recently been placed.
- Costophrenic (lateral) assist — hands over the lower lateral ribs, squeezing inwards and downwards. Useful where an abdominal push is contraindicated, and easier for a smaller assistant with a larger patient.
- Anterior chest compression — one hand over the upper chest and one over the abdomen, compressing both. Effective in tetraplegia.
Self-assisted techniques matter just as much, because they can be used the moment they are needed. A person in a wheelchair can throw the trunk forward over folded arms as they cough, or pull against the wheelchair frame, or use a fist under the ribs. Independence in self-assisted coughing predicts whether the technique is actually used at home.
Breath stacking and lung volume recruitment
Where the limiting factor is the breath in rather than the push out, the volume must be built up before the cough. Three methods do this:
- Lung volume recruitment (LVR) with a resuscitation bag — consecutive insufflations delivered through a mouthpiece or mask with a one-way valve, held with the glottis closed until the person cannot take more. The resulting volume is the maximum insufflation capacity, which is typically well above the vital capacity.3
- Glossopharyngeal breathing — the same result achieved without equipment, described below.
- Mechanical insufflation–exsufflation — a device that delivers a positive-pressure breath and then rapidly reverses to negative pressure, generating a cough-like flow. Covered in full in the cough assist guide. Combining MI-E with a manual abdominal thrust produces higher flows than either alone.4
Regular lung volume recruitment is not only used before coughing. Performed daily, it appears to maintain chest wall and lung compliance in people whose tidal volumes are permanently small, and it is recommended as routine practice once vital capacity falls below about 60% predicted.5
Glossopharyngeal breathing in detail
Glossopharyngeal breathing was described in poliomyelitis survivors in the early 1950s, who worked it out largely for themselves.6 The mouth, tongue, soft palate, pharynx and larynx are used together as a piston: a mouthful of air is trapped, the glottis opens briefly and the air is injected into the trachea, then the glottis closes to hold it. Repeating the movement stacks successive gulps.
How it is taught
- Begin seated and upright, with the mouth closed and the nose clear. Practise the movement without air first, in front of a mirror — the sequence is jaw down and tongue down to draw air in, lips close, tongue and jaw rise to push it back.
- Add one gulp at a time, exhaling between attempts. Most people manage a stroke volume of 40–200 mL per gulp.
- Build to 6–10 gulps in a run. A run of 10 well-executed gulps can add a litre or more to the inspired volume.
- Practise short and often — a few minutes several times a day. It is a motor skill, and it takes most people days to weeks, not minutes.
What it is used for
- Raising peak cough flow before a cough — the most common clinical use.
- Voice and speech — more air per phrase means longer sentences and greater volume, which for someone with a very low vital capacity changes how much they can participate in a conversation.
- Ventilator-free breathing time — some people with high cervical injury or advanced neuromuscular disease use GPB to sustain themselves off the ventilator for minutes to hours, which is both a quality-of-life gain and a safety margin during equipment failure.
- Maintaining chest wall mobility — a self-administered form of lung volume recruitment that needs no device, no power supply and no assistant.
Glossopharyngeal breathing depends on intact bulbar musculature and a competent glottis. In bulbar-onset motor neurone disease, advanced bulbar involvement in any condition, or where the glottis cannot seal, GPB will not work — and for the same reason mechanical insufflation–exsufflation is less effective. This is precisely the group in whom secretion management is hardest and in whom saliva control, positioning and early discussion of goals of care matter most.7
Cautions and contraindications
| Consideration | Why it matters |
|---|---|
| Undrained pneumothorax, or a recent one | Absolute contraindication to both breath stacking and MI-E until resolved and reviewed. See pneumothorax. |
| Bullous emphysema | Insufflation pressures may rupture a bulla. |
| Unstable spine, rib fractures, flail segment | Manual thrusts must be modified or avoided; use a lateral rather than abdominal assist and coordinate with the surgical or trauma team. |
| Recent abdominal surgery, abdominal aortic aneurysm, pregnancy, IVC filter | Avoid abdominal thrust; use costophrenic or anterior chest compression. |
| Osteoporosis | Fracture risk with vigorous manual compression — grade the force. |
| Uncontrolled reflux, impaired swallow, recent meal | Aspiration risk with insufflation and with abdominal thrusts. Time treatment away from feeds and sit upright. |
| Haemodynamic instability, uncontrolled arrhythmia, raised intracranial pressure | Positive pressure and Valsalva effects reduce venous return and raise intracranial pressure. |
| Recent barotrauma or bronchopleural fistula | Discuss with the treating medical team before any positive-pressure technique. |
Fitting it into an airway clearance session
Assisted cough is the final step, not the first. A typical sequence for someone with neuromuscular weakness and retained secretions:
- Bronchodilator if prescribed, and optimise position — upright or gravity-assisted, according to which region is affected.
- Loosening and mobilising phase — breathing techniques the person can manage, or an oscillating device, or manual techniques.
- Lung volume recruitment — breath stacking, LVR bag or glossopharyngeal breathing to reach maximum insufflation capacity.
- Assisted cough — manual thrust, MI-E, or MI-E with a manual thrust, repeated in short sets with rests.
- Reassess: auscultation, oxygen saturation, work of breathing, and what actually came up.
Sessions are short and repeated rather than long and exhausting; fatigue is the limiting factor, and an over-long session reduces the effectiveness of everything that follows. During a chest infection, frequency rises — sometimes hourly — and this is the point at which a family who have been taught the techniques in advance can keep someone out of hospital.
Training carers and families
These techniques are almost always delivered at home by someone other than a health professional. Effective teaching means: hands-on practice with feedback, not a leaflet; a written plan stating what to do when well and what to do when unwell, with the escalation threshold spelled out; equipment checks; and review at least annually, or whenever function changes. Peak cough flow measured at each review provides an objective trigger for escalating the plan, and gives families a number they can understand.
Role of the physiotherapist
Cough assistance is core physiotherapy practice and is largely physiotherapy-led. The contribution runs across four areas. Measurement: peak cough flow, vital capacity sitting and supine, and maximum insufflation capacity, tracked over time so that decline is anticipated rather than discovered during an admission. Selection and teaching: matching technique to the pattern of weakness — inspiratory, expiratory, bulbar or mixed — and teaching the patient and their carers to competence. Escalation planning: a written sick-day plan, and referral for MI-E, non-invasive ventilation or specialist review at the right time. Advocacy: making sure a person whose cough is failing is not discharged, extubated or decannulated without the equipment and training they need, and that the treating team understands that a peak cough flow below 160 L/min is a clinical finding with consequences.
Evidence summary
Framing. Cough augmentation is one of the few areas of cardiorespiratory physiotherapy where the physiological rationale is unambiguous, the measurements are simple and reproducible, and the outcome that matters — avoided hospital admission and avoided respiratory failure — is plausibly modifiable. What the literature lacks is large randomised trials, for the usual reasons: small, heterogeneous populations, an intervention that cannot be blinded, and clinical equipoise that most clinicians do not feel. The evidence base is therefore built on physiological studies, cohort comparisons and protocolised care series, and it is consistent.
Peak cough flow thresholdsBach's work established the flows on which practice still rests. In neuromuscular disease, unassisted peak cough flow correlates poorly with vital capacity alone but predicts secretion-related complications; assisted flows generated by manual thrust, breath stacking or MI-E are substantially higher than unassisted flows in the same individual.1 A PCF below 160 L/min was associated with failure to clear secretions and with extubation and decannulation failure, and a threshold of 270 L/min when well was proposed to identify those who will fall below 160 L/min during an intercurrent infection.2 These are cohort-derived thresholds, not trial endpoints, and they perform less well in bulbar disease and in children — but they remain the most practical clinical triggers available.
Protocolised respiratory managementThe strongest outcome signal comes from before-and-after and comparative series in which cough augmentation was one component of a protocol including nocturnal non-invasive ventilation, oximetry-guided clearance and avoidance of tracheostomy. Tzeng and Bach reported markedly lower rates of pneumonia and respiratory failure in neuromuscular patients managed by such a protocol than in historical and concurrent comparison groups.8 Sancho and colleagues showed MI-E to be effective in ALS without bulbar involvement, and progressively less effective as bulbar dysfunction advanced — the clearest demonstration that upper airway competence, not device pressure, is the limiting variable.7 European Neuromuscular Centre and ERS guidance now recommend routine lung volume recruitment once vital capacity falls below approximately 60% predicted, and cough augmentation when PCF falls below 270 L/min.5,9
Glossopharyngeal breathingGPB has a small but coherent literature. Described in poliomyelitis in 1951,6 it was subsequently shown in cervical spinal cord injury to increase vital capacity and peak cough flow after structured training, with gains maintained where practice continued.10 Trials are small and unblinded, and skill acquisition is highly variable — a substantial minority of learners never achieve a useful stroke volume. Its unique value is that it requires no device: it is available during a power failure, in the community, and to people for whom equipment funding is slow.
Physiotherapy implications- Measure peak cough flow at every review in any patient with neuromuscular weakness or high spinal cord injury. It takes under a minute and it is the number that drives the plan.
- Teach techniques before the threshold is crossed. A family learning an assisted cough for the first time during an acute infection will not do it well.
- Combine rather than choose: breath stacking or insufflation to raise volume, then a manual thrust timed to the cough, generates higher flows than any single component.4
- Assess bulbar function explicitly. Where the glottis cannot seal, both GPB and MI-E lose effectiveness, and the plan must shift towards saliva management, positioning, suction and honest goals-of-care conversation.
- A PCF below 160 L/min is a red flag against extubation or decannulation without a cough augmentation plan in place — make this explicit in the notes and at the ward round.
Ask which phase of the cough has failed, because the answer determines the technique. Weak inspiration is treated by adding volume; weak expiration by adding force; an incompetent glottis cannot be treated by either and needs a different plan. Then ask who will deliver the technique at 2 a.m. on a Sunday, because a technique that only a physiotherapist can perform will not be used when it is most needed. Finally, resist the temptation to treat the number rather than the patient: a person with a PCF of 200 L/min who mobilises, has no secretions and is clinically well needs a plan and a review, not daily treatment.
Evidence gapsThere are no adequately powered randomised trials of manually assisted cough against usual care with admission or pneumonia as the endpoint, and none are likely. Optimal dose and frequency of prophylactic lung volume recruitment are unknown. Paediatric thresholds are extrapolated from adult data and are probably wrong. The comparative effectiveness of GPB against LVR-bag breath stacking has not been formally tested, and predictors of who will learn GPB successfully have not been identified. Finally, the interaction between cough augmentation and non-invasive ventilation — which matters most, and in what order they should be introduced — remains unsettled.
References & evidence base
- Bach JR. Mechanical insufflation-exsufflation: comparison of peak expiratory flows with manually assisted and unassisted coughing techniques. Chest 1993;104:1553–62.
- Bach JR, Saporito LR. Criteria for extubation and tracheostomy tube removal for patients with ventilatory failure: a different approach to weaning. Chest 1996;110:1566–71.
- Kang SW, Bach JR. Maximum insufflation capacity. Chest 2000;118:61–5.
- Chatwin M, Toussaint M, Gonçalves MR, et al. Airway clearance techniques in neuromuscular disorders: a state of the art review. Respir Med 2018;136:98–110.
- Toussaint M, Chatwin M, Gonçalves MR, et al. 228th ENMC International Workshop: airway clearance techniques in neuromuscular disorders. Neuromuscul Disord 2018;28:289–98.
- Dail CW. Glossopharyngeal breathing by paralyzed patients. Calif Med 1951;75:217–18.
- Sancho J, Servera E, Díaz J, Marin J. Efficacy of mechanical insufflation-exsufflation in medically stable patients with amyotrophic lateral sclerosis. Chest 2004;125:1400–5.
- Tzeng AC, Bach JR. Prevention of pulmonary morbidity for patients with neuromuscular disease. Chest 2000;118:1390–6.
- Bott J, Blumenthal S, Buxton M, et al. Guidelines for the physiotherapy management of the adult, medical, spontaneously breathing patient. Thorax 2009;64(Suppl 1):i1–51.
- Nygren-Bonnier M, Wahman K, Lindholm P, et al. Glossopharyngeal pistoning for lung insufflation in people with cervical spinal cord injury. Spinal Cord 2009;47:418–22.
References are numbered in citation order (Vancouver/BMJ style) and were current at the time of writing. Guidelines are living documents — verify against the latest version before clinical use.
Clearing mucus well is a skill rather than a machine. We match a technique to your lungs and your routine, then coach it until you can do it at home on a bad morning.
Corrections: If something on this page is wrong, out of date or unclear, we want to know. Email reception@inspireclinic.au with the page name and what you believe is incorrect. Substantive corrections are made promptly, and the guide’s version and last-updated date are changed to reflect it.