Weaning from Mechanical Ventilation

Indications
Clinical Management
Patient Information
Audit
Evidence Base
Appendices

1. Indications

1.1 Background

The approach for weaning these patients is dependent on several factors

where the weaning is taking place
the level of supervision
the level of the patient's spinal cord injury
the neurological deficit
the age of the patient
the presence of premorbid respiratory disease
chest wall or pulmonary damage as a consequence of the trauma

In Salisbury spinal unit most patients are weaned on the open ward whilst other centres rely on intensive or high care facilities.

Immediately following injury patients with complete high spinal cord injuries only have working diaphragms and accessory muscles (assuming injury below C4/5, injuries above this level have different problems).

Intercostal muscles and abdominal muscles are paralysed and become initially flaccid. This has two implications, firstly active expiration is lost and coughing is impossible, (Roth et al 1997, Wang et al 1997) and secondly that chest wall compliance increases. On inspiration, diaphragmatic contraction leads to the negative intrathoracic pressure being transmitted to the compliant chest wall which is sucked in, causing ineffective lung expansion. This is known as paradoxical breathing (Lucke 1998, Menter et al 1997). The presence of fractured ribs will aggravate this. Over time as the joints and ligaments of the ribcage stiffen with the reduction in active movement this effect lessens (Axen et al 1985, Mansel and Norman 1990). The measurable consequences of this is a reduced vital capacity and FEV1/ PEFR (Linn et al 2000).

An initial VC of more than 1 litre is a favourable prognostic factor for weaning of patients. If the VC equals their expected tidal volume then they have no reserve and will need to be in ITU or HDU for monitoring and will probably require intubating and ventilating.

Inadequate lung expansion in these patients leads them to develop atelectasis and consolidation. Decreasing pulmonary compliance leads to increased work of breathing which these patients are unable to cope with. They often slip into respiratory failure after a few hours or days (Alderson 1999) which can be due to a combination of factors such as respiratory muscle or patient fatigue, lung complications or rising neurological level from spinal cord oedema.

The inability to clear secretions further promotes this process.

One point of note is that although VC invariably falls in the first 2-3 days following injury, it does eventually improve to above that of the immediate post injury measurement. This happens around the time that spasticity starts to appear, 6 days-6 weeks post injury. This is due to tone re-appearing in intercostal muscles, which help brace, the chest wall. It follows that attempts to wean will be more successful at this point. (Axen et al 1985, Mansel and Norman 1990).

1.1.1 Early tracheostomy - indications

Once ventilated there are a significant number of patients with these lesions who will take a considerable period to wean from the ventilator and, therefore, would benefit from a tracheostomy. Harrop et al 2004 found 69% of acute complete cervical injuries above C8 required tracheostomy. Como et al 2005 found that 100% of complete injuries at C5 and above, and 50% of complete C6 injuries required a tracheostomy. The same study reported that 7% of incomplete cervical injuries needed tracheostomies.

Advantages of early tracheostomy for weaning.

Allows the patient to be ventilated without sedation
When not sedated pressure support mode allows patient to have their own breathing pattern and continue to exercise respiratory muscles
Decreased dead space = decreased work of breathing (Bromley 1998)
Allows communication as mouth speech and lip reading possible without ET tube.
Allows oral fluids/ diet (when cuff down)
Aids secretion clearance
Cost of care decreases as patient can be nursed out of ITU

An important need for these patients is communication, and as soon as physiologically appropriate progress the patient to having periods of cuff deflation on the ventilator so that they can talk. If the deflated cuff is too bulky or the tube is too big then there is little airflow around it and speech is difficult. In this case the size and type of tube need to be reviewed.

Tracheostomy ICID & Spinal unit decannulation protocol

1.1.2 Relative Contraindications to tracheostomy

Anticipated anterior cervical surgery.
Recent anterior cervical surgery.

Early tracheostomy is recommended, as it is known that weaning may be a long process, and access for suction will be needed for some time after ventilator independence is achieved.

1.1.3 Clinical indications for commencing patient on the weaning protocol

The patient is haemodynamically stable without inotropic or vasopressor support.
Chest X-ray is clear.
Apyrexial, white cell count normal, no other infection indicators present.
The patient is requiring 30% or less inspired oxygen to achieve target saturation as determined by the consultant.
The patient requires 20cmsH2O peak inspiratory pressure or less to achieve tidal volumes of 7-15mls per kilo of preinjury body weight. N.B. Most patients whose peak pressure is above 20cms H2O need ITU measures to improve compliance.
The patient does not require more than 5 cms H2O PEEP
Unsupported vital capacity of at least 150mls.

1.2 Aim/purpose

To provide an evidence-based protocol, for use by staff on Avon ward of the spinal unit caring for spinal injured patients to ensure successful weaning from ventilatory support.

1.3 Patient/client group

Spinal cord injured patients who are receiving ventilatory support.

1.4 Exceptions/ contraindications

Unresolved paralytic ileus or abdominal distension causing diaphragm splinting.
Fever
Neurological changes
Sedative drugs
Electrolyte imbalance
Pain
Psychological disturbance
Lack of sleep

1.5 Options

1.5.1 Weaning with low vital capacity

There may be situations when the patient's VC does not meet the required minimum level but it may still be appropriate to attempt to wean them from ventilation. The patient must:

Fulfil the other indications for weaning
Have unsupported vital capacity greater than unsupported tidal volume, this is an indication that they have some reserve in their respiratory muscles.

In this case a Level 6 competent member of staff may in discussion with the consultant devise a 'bespoke' weaning programme which will need to be more conservative than the standard programme to reflect the patients' individual needs.

1.5.2 Long term ventilation weaning

If a patient is expected to continue to require long term ventilation it may still be appropriate to attempt to wean from the ventilator for short periods. Advantages of this are:

Improved safety in the event of disconnection.
Improved ease of mobility when transferring (e.g. bed to wheelchair, or showering etc).
Patient peace of mind.

In this instance the peak inspiratory pressure (PIP) would not be gradually reduced but the patient would start on PVFB or the T-Piece for increasing periods. This programme would be specifically devised by a level 6 competent member of staff.

1.5.3 Accelerated weaning

If a patient is consistently exceeding their target observations after a weaning episode they may be suitable for accelerated weaning. In this case a Level 6 competent member of staff may in discussion with the consultant devise a 'bespoke' weaning programme which will reflect the patients' individual needs.

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2. Clinical Management

2.1 Staff & equipment

Staff

A level 6 competent member of staff to lead weaning program.
Nurses or physiotherapists who are competent to level 4 in Section1: Understanding respiratory function, Section 2.1: Assessment and Monitoring; Section 3.1 Chest therapy and airway clearance techniques; Section 4.1: Tracheostomy Care ; Section 4.2: Tracheal suctioning; Section 6.1: Supported ventilation (BiPAP) ; and Section 7.1 Mechanical ventilation core skills (TBC).
Speech & Language Therapist to carry out the swallowing assessment.
Initiation of weaning should not be attempted if the nurse in charge deems that the nursing establishment is inadequate to safely undertake weaning.

Equipment

Low resistance ventilator with flow trigger and alarms to detect disconnection, apnoea and low minute ventilation (for e.g. Respironics BiPAP 'Synchrony') and circuitry.
Uninterrupted power supply (UPS) connected to the BiPAP.
Fisher Paykel humidification system.
Oxygen saturation monitor
Wrights respirometer
T-Piece circuit with cold water humidification system attached to oxygen or air as prescribed.
Speaking Valve – Portex 'Orator' or Rusch.
HME (Heat moisture exchange filter) (Thermovent T or 'Swedish nose')
Red decannulation bung.
Tracheostomy cuff manometer.
Weaning record charts.

2.2 Method/procedure

2.2.1 Weaning from ventilatory (BiPAP) support

Before initiating a weaning program, the procedure should be thoroughly explained to the patient and the family. The patient needs to consent and understand the procedure.
Wean the patient whilst flat in bed initially i.e. head and feet level; they must still be turned . Sitting the patient up is a mechanical disadvantage for tetraplegic patients. (Chen et al 1990, Mansel & Norman 1990). The exception to this is the patient with Central Cord Syndrome with preserved intercostal muscles but a paralyzed diaphragm.
Weaning is commenced by progressively reducing the level of pressure support. This is done incrementally with reductions of peak pressures by 2cms H20, initially for one hour 2-3 times a day(Tromans et al 1998). Respiratory rate, tidal volume /vital capacity and saturations are monitored at the start and end of these times. Weaning is progressively increased by half an hour to an hour at a time, depending on fatigue, until 24 hours is achieved. Then a new process is repeated, again, reducing the pressure by a further 2cms H20.
More arduous respiratory muscle training can be undertaken by turning the peak pressure down 6-8 cmsH20 pressure, initially for 10 breaths, monitoring the tidal volumes /vital capacity at the start and end of the procedure. (Tromans et al 1998) Or this can be slowly lengthened, bearing in mind that, in some patients, this may cause fatigue and in the partially innervated muscles it is not uncommon for it to take 2-3 days to recover from a period of fatigue.

The patient will spend therefore part of the day resting at the higher pressure levels, (optimum rest time is 2 hours) increasing periods of the day breathing with a slight reduction in pressure support and other periods with slightly more aggressive respiratory muscle training.

2.2.2 Weaning from T-piece support

When the level of pressure support is down to (12 cmsH2O) pressure, they can start to spend increasingly longer periods off the ventilator on a T-piece. It is unnecessary to go below 10-12 cmsH2O peak inspired pressure as this pressure generally does not overcome the resistance of the tubing and it is more difficult for the patient to breath on the ventilator.

This method of weaning is termed T-Piece weaning or progressive ventilator free breathing (PVFB). It is based on slowly increasing the periods of time that the patient spends breathing off the ventilator.

Advantages of PVFB weaning are: (Peterson et al 1994)

PVFB alternates periods of work with periods of rest and so offers the respiratory muscles the benefits of a training effect - both for strengthening and endurance.
Another advantage of PVFB weaning is the lower airway resistance of the T-Piece system thus reducing work of breathing (WOB).
PVFB weaning can begin very early in the individuals post injury period, with durations as brief as 1-2 mins. This allows the patient, family and staff to see and be encouraged by early incremental progress.
Social advantage of enabling the individual to commence 'trach talking' with a one way speaking valve designed to permit exhaled air to pass over vocal cords with periods of tracheostomy cuff deflation. They have often started talking on the BiPAP with the cuff down anyway and talking on the T-piece is harder work.

Eventually, by increasing the time off the ventilator by around the 24-hour period, the patient will wean. We aim for off all day with resting at night, then gradually reduce time of support at night.

Documented parameters for all weans:

Forced vital capacity (FVC)
Respiratory rate (RR)
Heart rate
Oxygen saturations
Minute Ventilation

2.2.3 Humidification

Aggressive humidification is beneficial to maintain mobility of secretions. Any drop in airways humidification leads to thickening of secretions and loss of lung compliance.

When the patient is receiving ventilatory support from the BiPAP they should have heated humidification. The heated humidification can be gradually replaced during T-piece weaning which is usually conducted using a cold water humidification system.

The continued use of the T-piece reduces airways resistance but this can be substituted for increasing periods with a Heat, moisture exchanger (HME) or Swedish nose.(Portex Thermovent T)

2.2.4 Tracheostomy weaning

Tracheostomy weaning must be addressed alongside ventilatory weaning and the two processes should go hand in hand.

Tracheostomy ICID & Spinal unit decannulation protocol.

Once the patient starts to be disconnected from the ventilator, the tracheostomy cuff can be let down to try and improve phonation. It is possible to deflate the cuff whilst on pressure support, depending on the alarms on the ventilator, to allow phonation. Unfortunately, many patients will find this uncomfortable for long periods, especially if trying to sleep.

Speaking valves (with cuff down) allow return of laryngeal reflexes and give back natural PEEP, they enable re-education of pharyngeal movement with improvement in swallowing and reduction in the risk of aspiration.

Once the patient has been disconnected from the ventilator for several days to a week, then changing the tracheostomy to a size smaller (uncuffed) will improve phonation but still allow access for airways toilet.

Once the patient can adequately breathe around the tracheostomy tube, occlusion with a red bung can be commenced for increasing periods.

Patients can have problems with over-aggressive humidification through speaking valves with condensation on the flap that may mean the valve doesn't work properly and may increase work of breathing.

The timing of decannulation is dependent on the need for access for airways toilet in terms of suction and the ability to clear the airways with assisted coughing.

The success of failure of weaning depends not only on the underlying pathological process but also the patience of those providing the treatment and the co-operation of the patient.

2.2.5 Swallowing assessment

SALT assessment is an essential part of the weaning of the tetraplegic patient from the ventilator as not only is pharyngeal movement impaired by the tracheostomy, but also by the cervical spine injury, possibly the stabilising surgery, the head neck rigidity following the injury. There is often a degree of bulbar involvement in the cervical spine injuries (not only those above C3) with aberration of both motor and sensory modalities. (Wolf and Meiners 2003, Neville et al 2005)

2.2.6 Important points of off ventilator weaning

Never exhaust / tire the patient. Watch for rises in heart rate and/or respiratory rate as signs of tiring. Blood gases may be useful.

Speaking valves are one way valves, which attach to tracheostomy tubes that allow patients to breathe in through the tracheostomy and out around the deflated cuff through their larynx. They have two uses in that they give the patients back their intrinsic PEEP and allow them to talk.

Successful weaning is very labour intensive. It can work without 1:1 or 1:2 nursing, but it does require a structured disciplined approach with patient manageable goals and documentation of progress to work outside of the ITU/HDU setting.

2.3 Potential complications / Risk Management

See Risk Assessment

2.4 After care

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3. Patient Information

We have accessed this pdf "Understanding and Managing Respiratory Complications after SCI"

4. Audit

Standards:

Aspect of Care	%	Exception	Definition
All staff involved with the weaning of spinal patients from ventilation will be aware of this protocol.	100%	None	See section 2.1 Staff questionnaire
All patients undergoing weaning will have target observations determined and recorded prior to commencement.	100%	None	Audit

Criteria	Main source of evidence	Alternative source of evidence	Met? Yes / No / N/A
Indications for weaning met?	Medical notes	Physio notes X ray records Nursing observation chart
Documented consent?	Medical notes	Physio notes
Were targets set and documented?	Weaning chart	Physio notes Medical notes
Did the weaning follow standard protocol or was it 'bespoke'?	Weaning chart	Medical notes Physio notes	Standard Bespoke Not met

Data Collection:

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5. Evidence Base

5.1 Sources of information

Alderson JD. 1999. Spinal cord injuries. Care of the Critically Ill. 15 (2) 48-52.

Axen K, Pineda H, Shunfenthal I, Haas F 1985 Diaphragmatic function following cervical cord injury: neurally mediated improvement. Archives of Physical Medicine and Rehabilitation 66(April): 219–222.

Chen C, Lien I, Wu M 1990 Respiratory function in patients with spinal cord injuries: effects of posture. Paraplegia 28: 81–86.

Chevrolet J, Deleamont P 1991. Repeated vital capacity measurements as predictive parameters for MV need and weaning success in Guillan Barre Syndrome AM rev resp dis 144.

Como JJ, Sutton ERH, McCunn M, Dutton R, Johnson S, Aarabi B, Scalea T 2005 Characterising the need for mechanical ventilation following cervical spinal cord injury with neurological deficit. Journal of Trauma, Injury Infection and Critical Care. 59 (4) 912 – 916.

Epstein SK, 2002 Weaning from mechanical ventilation. Respiratory care 47 (4) 454-468.

Harrop J, Sharan A, Scheid E, VaccaroA, Przybylski G, Trachesotomy placement in patients with complete cervical spinal cord injury: American Spinal Injuries Association Grade A. Journal Neurosurgery (Spine 1) 100 20-23.

Linn WM, Adkins RH, Gong H, Waters RL. 2000. Pulmonary Function in Chronic Spinal Cord injury: A Cross-Sectional Survey of 222 Southern California Adult Outpatients. Arch Phys Med Rehabil. 81 757-763.

Mahanes D, Lewis R. 2004 Weaning of the neuroligically impaired patient. Crtitical Care Nursing Clinics of North America. 16 387-393.

Mansel J, Norman J 1990 Respiratory complications and management of spinal cord injuries. Chest 97(6): 1446–1452.

Peterson W, Charlifue W, Gerhart A, Whiteneck G, 1994 Two mehtods of weanng persons with quadriplegia from mechanical ventilators. Paraplegia 32 98-103

Roth EJ, Lu A, Primack S, Oken J, Nussbaum S, Berkowitz M, Powley S. 1997. Ventilatory function in cervical and high thoracic spinal cord injury. Am J Phys Med & Rehabil. 76 (4) 262-267.

Thomas E, Paulson SS.1994. Protocol for Weaning the SCI Patient. SCI Nursing. 11 (2) 42-45.

Tromans AM, Mecci M, Barrett FH, Ward TA, Grundy DJ. 1998 The use of the BiPAP biphasic positive airway pressure system in acute spinal cord injury. Spinal Cord. 36, 481-484.

Wong AY, Jaeger RJ, Yarkony GM, Turba RM, 1997. Cough in spinal cord injured patients: the relationship between motor level and peak expiratory flow. Spinal Cord. 35 299-302.