In summary, these changes collectively lead to reduced ventilation and secretion clearance, along with an increased work of breathing.

For an acute, motor-complete NLI at T6 or above, but especially at C5 and above, significant respiratory function changes occur due to neuromuscular weakness and paralysis, compounded by the presence of spinal shock, as well as autonomic nervous system (ANS) disruption. Key respiratory muscles affected include the intercostal, abdominal and diaphragm muscles.

At this time, weakened or paralysed respiratory muscles present with flaccidity and increased compliance due to spinal shock. This affects diaphragm positioning and function, as well as breathing mechanics. Ultimately, this results in reduced ventilation and secretion clearance. Paradoxical breathing can also develop, which is very inefficient and increases the work of breathing.

For more information on respiratory function changes following SCI, refer to Respiratory changes.

Without adequate and timely intervention, the combination of hypoxaemia, hypercapnia and respiratory fatigue is a key precursor to the onset of respiratory failure. In addition to this, chronic hypoventilation also contributes to sleep-disordered breathing, compounded by any other obstructive and central factors.

Many lung volume augmentation techniques are clinically practised today by physiotherapists. They have evolved over decades, in the treatment of post-surgical and neuromuscular conditions, including SCI. While there is considerable clinical experience in the use of these interventions, there has been limited scientific study of their efficacy in the management of SCI respiratory dysfunction.

In 2022, The Australian and New Zealand Clinical Practice Guidelines: For Physiotherapy Management of People with Spinal Cord Injury were developed, providing evidence-based recommendations where possible, or consensus-based opinion statements.

The process completed systematic reviews and SCI professional peer consultation to address physiotherapy enquiry questions, presented in a PICO (Participant, Intervention, Comparison and Outcome) format. The outcomes are presented as either evidence or consensus statements and form the new clinical practice guidelines. Those which are relevant to the management of respiratory function following SCI, have been incorporated into the “Lung Volume Augmentation” and “Secretion Management” sections. They will be presented using the following colour variations banners.

The Australian and New Zealand Physiotherapy Guidelines for people with SCI states:

Evidence: Weak for recommendation

Guideline

The Australian and New Zealand Physiotherapy Guidelines for people with SCI states:

Consensus: Weak for recommendation

Guideline

The Australian and New Zealand Physiotherapy Guidelines for people with SCI states:

Consensus: Strong for recommendation

Guideline

The Australian and New Zealand Physiotherapy Guidelines for people with SCI states:

Consensus: Weak against recommendation

Guideline

Intrapulmonary Percussive Ventilation (IPV) devices deliver aerosolised medication, to address sputum hydration and viscosity, via high-frequency bursts of low-pressure gas—typically 100-300 cycles per minute. This creates oscillating inspiratory and expiratory airway pressures, ranging from 10-40 cmH₂O. This expands the lungs and internally vibrates and dilates the peripheral airways—similar to the external technique of percussion—for the purpose of dislodging sputum.

For the user, it may enable a more efficient, consistent and customised experience in comparison to the traditional manual therapy. For therapists and carers, it may reduce the manual handling risks associated with repetitive strain injuries.

IPV has been more commonly used in the treatment of chronic pulmonary diseases, including cystic fibrosis and bronchiectasis, as well as degenerative neuromuscular conditions. However, some mechanical insufflation exsufflation (MI-E) devices used in SCI respiratory management, are now providing the addition feature of IPV, called a “Percussor mode”. This effectively broadens the scope of the MI-E device to provide sputum mobilisation (peripheral ACT), in addition to its familiar role in lung volume and cough augmentation (proximal ACT).

Available interfaces include mouthpiece and face mask, with some also permitting attachment to tracheostomy and endotracheal tubes. However, similar to MI-E devices offering burst NIV and IPPB modes, the attached circuit is required to have an expiratory valve/leak port to prevent CO₂ rebreathing during longer use (disconnect user from MI-E device when treatment is complete).

• Some circuits have a switch valve on the circuit to open or close when changing between modes (MI-E mode (closed) and IPPB, NIV, IPV (open)).
• Some circuits have the exhalation valve/leak port as an extra attachment (it is normally preferable to operate with 2 circuits: 1 circuit dedicated to MI-E and another circuit dedicated to the other modes)

Given IPV can generate high frequency and airway pressures, cautious clinical introduction would be important, to minimise the risk of barotrauma in the acute phase of SCI management or when introducing to a person with a chronic SCI who has reduced airway and chest wall compliance.

More time is needed to determine the clinical utility of this feature for sputum mobilisation in SCI respiratory management, including how to optimise the provided parameters e.g. inspiratory pressure (e.g. 0-70 cmH₂0), frequency (e.g. 10-780 CPM) and the inspiratory to expiratory ratio (typically ranging 1:5 to 5:1).

However, a clinical trial of IPV, may otherwise be appropriate in the acute and chronic phase of SCI management:

• if there is a high sputum load and MI-E is not being effective on its own
• to reduce therapist and carer manual handling and the risk of repetitive strain injuries, related to percussion
• if percussion is otherwise not tolerated, but also not contraindicated.

There are other distinct therapies which provide chest wall vibration and oscillations, via unique devices. This includes high frequency chest wall oscillations (HFCWO) and high frequency chest wall compression (HFCWC). Using inflatable chest vests and wraps which are externally applied, it generates an external vibration with compression—similar to the external technique of expiratory vibrations with compression—for the purpose of dislodging sputum.

For the user, it may enable a more efficient, consistent and customised experience in comparison to the traditional manual therapy. For therapists and carers, it may reduce the manual handling risks associated with repetitive strain injuries.

While again not commonly used for sputum mobilisation in SCI respiratory management, some MI-E devices are now providing accessory options which provide additional features referred to as HFCWO (along with HFCWC). Similar to IPV, this effectively broadens the scope of the MI-E device to provide sputum mobilisation (peripheral ACT), in addition to its familiar role in lung volume and cough augmentation (proximal ACT).

Newer designs favour use of an inflatable wrap, and this may also be easier to apply when an adult user is supine.

Inclusion of HFCWO would not be considered appropriate during the acute phase of SCI management, when a person is ventilator dependent, has unstable spinal and chest wall injuries, significant pain or at high risk of respiratory fatigue. It would also not be appropriate if there were concerns regarding risk of spinal or chest wall fracture in a person with a chronic SCI.

More time is needed to determine the clinical utility of this accessory for sputum mobilisation in SCI respiratory management, including how to optimise the provided parameters e.g. oscillations (e.g. 50-900 bpm/0.83-15Hz), compression (e.g. 5-70cm H₂0) and the inspiratory to expiratory ratio (typically 1:1). In addition to this, while NIV support is commonly provided when HFWCO is used in paediatric populations with neuromuscular disease, it is unknown if ventilation support may be required in adult populations with SCI. Issues such as the increased work of breathing and altered lung/chest wall compliance following SCI in the acute versus chronic stage post-injury will be important to address.

However, a clinical trial of MI-E with the addition of HFCWO, may otherwise be appropriate in the sub-acute and chronic phase of SCI management:

• if there is a high sputum load and MI-E is not being effective on its own
• to reduce therapist and carer manual handling and the risk of repetitive strain injuries, related to expiratory vibrations with compression.

The Australian and New Zealand Physiotherapy Guidelines for people with SCI states:

Consensus: Weak against recommendation

Positive expiratory pressure devices should not be provided to improve secretion clearance in people with SCI who have expiratory muscle weakness.

Positive expiratory pressure (PEP) therapy can be delivered using a handheld device or integrated into an inspiratory muscle trainer. It may also be combined with a nebuliser or connected in-line with a mechanical ventilator circuit. Varied inspiratory lung volumes are used to apply forceful, sustained exhalation against a fixed or oscillating resistance pressure—typically between 10-20 cmH₂O.

PEP generates a positive pressure within the lungs and splints open the airways during the expiratory phase of breathing. It aims to improve alveolar collateral ventilation, while enhancing functional residual capacity and minimising dynamic airway collapse during forced exhalation.

PEP therapy is more commonly used in the treatment of chronic pulmonary diseases, including cystic fibrosis and bronchiectasis, rather than sputum mobilisation in SCI respiratory management.

In the presence of significant respiratory muscle weakness following SCI, the technique is very difficult to perform effectively. There is also a heightened risk of creating barotrauma, worsening hypercapnia or exacerbating respiratory fatigue for a person in the acute phase of SCI management.

For these reasons, the use of PEP is not recommended as a peripheral ACT for a person with SCI, who has expiratory muscle weakness during acute management.

However, if respiratory muscle function improves, PEP therapy may otherwise be appropriate in the sub-acute and chronic phase of SCI management where:

• the risk of respiratory fatigue is minimal
• there is a high sputum load and risk of airway collapse
• the user has some degree of expiratory muscle function and is appropriate to commence expiratory muscle training.

Similar to the effect of chest wall strapping (CWS), autogenic drainage (AD) uses the effect of expiratory flow at low lung volumes. AD does not use a device. Rather it requires a range of inspiratory lung volumes to be achieved, followed by varying forced expiratory flow rates, across three distinct stages of breathing. By generating different exhalation pressures, autogenic drainage mobilises sputum from small peripheral airways, toward larger central airways—while also minimising dynamic airway collapse during exhalation.

Effective performance requires coaching, along with a sufficiently high sputum load to provide the necessary auditory feedback to the user. It also requires significant and sustained expiratory muscle control.

Because AD involves repeated inspiratory efforts and forced exhalations, it is likely to become fatiguing for a person with an acute SCI. Significant respiratory muscle weakness also makes this technique difficult to perform effectively.

AD breathing techniques are more commonly used in the treatment of chronic pulmonary diseases, including cystic fibrosis and bronchiectasis, rather than SCI respiratory management.

However, if respiratory muscle function is adequate, AD breathing may otherwise be appropriate in the sub-acute and chronic phase of SCI management where:

• the risk of respiratory fatigue is minimal
• there is a high sputum load and risk of airway collapse
• the user has some degree of expiratory muscle function and is able to respond to the necessary coaching.

1. The MI-E device uses compressed air +/- oxygen and is typically pressure-controlled, but time-cycled.
2. The operator sets various parameters including whether treatment will be insufflation +/- exsufflation, as well as the maximum pressures and time for insufflation +/- exsufflation, the insufflation flow rate or rise time and inspiratory trigger sensitivity.
3. The operator initiates mechanical insufflation using the device toggle switch (on the device, hand remote or foot pedal) via an appropriate circuit and interface attached to the user.
4. A positive pressure breath is delivered by the device (typically 20 to 40 cmH₂O), up to the user’s maximal insufflation capacity (MIC). This supports lung volume augmentation with minimal effort from the user.
5. Expiration occurs passively through the attached circuit with nil exhalation valve/leak port (unless using the following other non-MI-E modes on the same device).
6. A series of insufflation breaths is delivered for lung volume augmentation and sputum mobilisation; a mechanical assisted cough can then be triggered by rapidly reversing airflow to generate negative pressure (typically –20 to –40 cm H₂O). This sudden shift in pressure simulates a cough, without requiring active effort from the user. The effectiveness of the cough is enhanced by increasing the pressure gradient between insufflation and exsufflation, thereby increasing forced tidal volume and peak expiratory flow. A manual assisted cough (MAC) can be applied simultaneously to further improve cough effectiveness.
7. While optimal MI-E dosage and frequency has not been determined yet, a typical MI-E treatment session may be repeated cycles of 3 pre-therapy breaths, 2 exsufflations, 2 post-therapy breaths. Other treatment approaches may consist of cycling between insufflation and exsufflation, with a exsufflation cough as needed.

Modes may include:

• manual– allows the operator greater control over insufflation and exsufflation timing and pressures
• automatic– enables pre-programmed cycle for consistent, repeatable therapy—suitable for unsupervised use by trained clinicians and carers
• IPPB– supports programmed lung volume recruitment initiated by the user when needed
• burst NIV– provides EPAP typically used before or after treatment for respiratory rest, while maintaining any lung volume recruitment; it is not intended for continuous ventilatory support and will be time limited e.g. <15 minutes; it is not for users with a tracheostomy or endotracheal tube
• Intrapulmonary Percussive Ventilation (IPV) or “Percussor Mode”– provides airway percussion therapy with settings for frequency (e.g. 10-780 CPM), pressure (e.g. 0-70 cmH₂0) and I:E ratios (e.g. 1:5 to 5:1)
• High Frequency Chest Wall Oscillations (HFCWO)– typically using an inflatable chest wrap to provide external chest wall percussion with settings for frequency (e.g. 50-900 bpm), pressure (e.g. 5-70 cmH₂0) and I:E ratios (typically 1:1).

Circuit design must be appropriate to the mode, as well as the actual device.

• Most MI-E devices use a single lumen circuit, although dual lumen may be required, ensuring there is no contamination between insufflation and exsufflation debris
• Manual and automatic MI-E modes use standard MI-E circuits which have no exhalation valve/leak ports, to allow for delivery of negative pressure delivered in short treatment sessions (disconnect user from MI-E device when each short treatment session is complete)
• In contrast, IPPB, NIV and IPV modes require a circuit with an exhalation valve/leak port, to prevent CO₂ rebreathing during longer use (disconnect user from MI-E device when treatment is complete).
  • Some circuits have the exhalation valve/leak port as an extra attachment (it is normally preferable to operate with 2 circuits: 1 circuit dedicated to MI-E and another circuit dedicated to the other modes)
  • Some circuits have a switch valve on the circuit to open or close when changing between modes (MI-E mode (closed) and IPPB, NIV, IPV (open)).

Additional features may include:

• interface options such as a non-vented mask (preferred) versus mouthpiece, and sometimes a tracheostomy or endotracheal tube connector
• options for ambient air, and sometimes supplemental oxygen via an entrainment port and/or humidification
• recorded measures of volume and exsufflation flow rate, pulse oximetry for monitoring during treatment sessions
• real time pressure wave and bar graphs for feedback during treatment sessions
• real time capacity to record or adjust treatment sessions
• parameter variations may include
  • insufflation and exsufflation pressures and time ratios, with some providing an option for stepped insufflation
  • pause time between insufflation and exsufflation/cough
  • flow rate or rise time options for each insufflation
  • sensitivity trigger options for insufflation
  • synchrony options for insufflation or exsufflation/cough
  • airway oscillations on insufflation, exsufflation or both with a selection range for frequency (e.g. 4-20 Hz) and amplitude (e.g. 1-10 cmH₂0)
  • EPAP on pause breath
  • options for pre-therapy and post-recruitment breaths
  • number of pre-save programs for different types of therapies, including when well and unwell.

Additional accessories may include:

• option of a stand as well as mask holders
• internal battery (e.g. 3-4 hr capacity) in addition to external power supply
• hand remote or foot pedal
• pulse oximeter.

Additional variations may include:

• overall weight of device
• device handle, carry bag etc.
• customisation of screen colours, or orientation of screen for visualisation
• touch screen versus button operation, including varying sensitivity and ease of navigation
• connectivity e.g. ethernet, USB, USB C, HDMI port, flash drive, wifi, bluetooth
• remote control access e.g. app to adjust device settings via a mobile phone
• data download processes i.e. simple vs multi-stage
• access to compliance summary/user log
• safety prompts about correct circuit +/- external valve/leak port
• terminology and use of positive (+) and negative (-) numbers for insufflation and exsufflation
• provision of user quick reference guides and online resources.

Recommendations for use include:

• during the initial use of MI-E carefully monitor oxygen and heart rate settings to ensure safety; if there is a high sputum load, it may be advisable to have suction and resuscitation equipment ready
• start pressure settings low and seek user feedback, while monitoring chest wall expansion to determine adequacy of pressure settings; typically start insufflation with 15 cmH₂0 and increase in 5 cmH₂0 increments (unless the user is also accessing NIV, then start insufflation NIV IPAP +5 cmH₂0 and increase in 5 cmH₂0 increments)
• keep exsufflation pressure 5-10 cmH₂0 more negative than insufflation pressure to maintain a pressure gradient that biases sputum mobilisation
• progressively increase pressures until efficacy is achieved, remembering the delivered tidal volume varies depending on airway resistance, lung compliance, and circuit integrity
• individually adjust inspiratory and expiratory time/rise/pressures for each user, matching their normal breathing pattern and optimising comfort
• if adding oscillations, adjust insufflation and exsufflations pressures to factor in the additional pressure overlay; however, there is little evidence this is a useful feature when compared to options with percussor modes
• if there are concerns about chest wall and spine bone mineral density, or chest wall and lung compliance, start with lower flow rates and pressures; also opt for IPV mode rather than use HFCWO
• measures of volume and peak flow rate are not always accurate and represent gas decompression in the device circuit, so also compare to pressure-wave forms as well as observations of the chest wall and sound of the cough effectiveness
• when the user is spontaneously breathing, use of a non-vented face mask is preferable to a mouthpiece
• MI-E use may be an option for ventilated users, but extreme caution is required to reduce the risk of volutrauma/barotrauma. In these cases:
  • it may be safer to leave the invasive airway cuff deflated and permit some leakage, rather than inflating to maximise pressure delivery to the lung periphery
  • inspiratory pressure settings may need to be carefully increased to account for increased airway resistance, dead space and leakage.

The following are examples of published flowcharts for the safe introduction and titration of basic MI-E parameters in adults with neuromuscular disease, including SCI. It is also important to note that device pressure and volume readings may not accurately indicate the lung volume augmentation or peak cough flow achieved. Rather subjective reports from the user and objective assessment of chest wall expansion and the sound of the cough should also inform titration.

A video demonstrating MI-E therapy is here.

A video with MI-E therapy FAQ is here.

More information about MI-E can be found here.

The MAC technique requires the operator to have CORRECT hand positioning, directional force, co-ordination and cueing.

A variety of hand or forearm positions can be utilised, typically with a thrust given at the abdomen +/- compression on the chest wall.

The number of operators may vary from 1 to 3, depending on the needs and size of the person with SCI.

A video demonstrating MI-E therapy is here.

A video demonstrating lung volume augmentation prior to MAC technique in sitting is here.

More information about MAC can be found here.

A video demonstrating MI-E + MAC therapy is here.