Preparation of the critical patient for aeromedical transport
by Dr Minh Le Cong and Dr Geoff Ramin
Peer reviewed by Dr Yen Chow ( who made some very helpful suggestions!)
Introduction
Although the reduction of time at scene is a key goal of any retrieval system it is important that this is not achieved at the expense of critical elements of patient care. Whether at a primary response or undertaking an interhospital transfer the team should spend an appropriate amount of time to prepare the patient for transport. The key word to note is “appropriate”. What is appropriate for one patient will not necessarily apply to another and the biggest mistake a team can make is to spend time undertaking procedures or attempting to “fix the numbers” when the patient clearly requires movement to a meaningful intervention that is not immediately available. As an example consider the primary response retrieval of a patient with a stab wound to the abdomen, and a clinical picture of rapidly evolving haemorrhagic shock. Attempts to stabilise or even normalise blood pressure prior to transportation would be inappropriate as the patient clearly requires source control of the bleeding and all decisions need to be made in the context of getting him to a suitably trained and equipped surgeon in the shortest possible time. This would contrast with the interhospital transfer of a child with a clinical picture of epiglottis on the verge of complete airway obstruction. In this case time on scene spent obtaining a secure airway would clearly be appropriate.
The preparation of a patient for transport is a fundamental role of the retrieval team and requires the team to have the necessary skills to assess the patient, determine the specific requirements in that given scenario, implement them in a timely manner and do so whilst considering the implications of location, geography, local resources and the physiological consequences of transportation.
The aeromedical setting places additional stresses upon the critically ill or injured patient such as hypoxia, hypothermia, vibration and noise. Adequate patient preparation requires consideration of how best to mitigate these stressors and decrease their impact on the patient’s already impaired physiological status as a consequence of the effects of major illness or trauma. It is also important to be aware that the aeromedical environment is all too often a restrictive and claustrophobic experience for many patients which can lead to significant psychological stress. Fear of flying is well reported in the aeromedical literature and may be a cause of unexpected agitation. It is not uncommon that aeromedical transport involves patients with life threatening injuries or illnesses and the prospects of death occurring during transport are very real. Conscious patients will have a greater awareness of these possibilities than you may appreciate. Similarly in many countries it is not uncommon for air transfer of palliative care patients to be undertaken so as to return them to their local community for end stage care. Beyond the normal requirements of clinical care it is part of the role of the retrieval team to consider the social health and welfare of their patients particularly when removing them from their familiar surroundings and networks. When it comes to paediatric patients, it is important that the family can meet with the team, discuss the reasons for transportation and provide consent for this to occur. There are many potential benefits in certain clinical scenarios in having a parent or legal guardian accompany a child although transport platform limitations may not always make this possible. Overall it is important to consider the following model of aeromedical retrieval practice when it comes to patient preparation.
The aeromedical setting also places stresses on the team due to limitations of the environment and resources. During transport there is restricted space and access to the patient particularly during the times of patient movement between beds, in or out of vehicles and during take-off and landing. Lines, tubes and equipment are at risk of dislodgement or damage. Monitoring of the patient can be limited. Ambient noise, cramped space, various lighting conditions as well as exposure to the outside weather places challenges to assessment and management of the patient as well as team communication. There are also limitations to equipment and supplies and during transport there is no other hands-on help available other than your team.
The importance of communication
The single most important aspect of conducting successful and safe aeromedical retrieval is communication. For the referring doctor the ability to accurately convey the situation and the current and predicted requirements of the acute patient is crucial. Use of a systematic standardised manner of clinical communication (see box below) is increasingly recommended for the acute patient. Note that the last act of clarification and assuring comprehension of the communication listed below is vital.
The mainstay of aeromedical retrieval planning and activation is conducted using the telephone with some increasing use of alternative media technologies such as videoconferencing. The use of conference calls speeds up communication between parties and enhances agreement on a comprehensive clinical and logistical plan. The risks of inadequate communication – or even worse a misunderstanding of conveyed information – are high if the initial request for aeromedical retrieval is conducted in a non-standardised and disordered manner.
iSoBAR : How to handover the patient
J Porteous et al. iSoBAR – a concept and handover checklist : the National Clinical Handover initiative. MJA, 2009;190(11):S152-S156 |
However, practical concerns determine behaviour and due to the critical nature of an unstable patient, there are often cases when there isn’t time for the treating doctor to leave the patient. In such cases, one possibility is to delegate the task of calling the retrieval team to an assistant who would still use the same communication checklist. The checklist is simple and can easily be implemented at your local hospital by all health professionals who may be needed to manage a critical patient. Time spent in practising communication and use of the standard checklist is likely to be the single most effective skill in the art of aeromedical retrieval of the critical patient.
Clinical Considerations
The fundamental question for the treating doctor to ask is “What definitive care is needed for this patient?” The answer to this question will guide the resuscitation, stabilisation for transport, ongoing retrieval transport care and eventual destination of the retrieval. To aid stabilisation of the patient prior to aeromedical evacuation, this definitive care can often be provided by the rural doctor. One common example is preparation of a patient with an acute ST elevation myocardial infarction who meets the criteria for acute thrombolysis. The earlier thrombolysis is delivered the better the outcome and the better the patient will tolerate the stresses of air evacuation. Another example is preparing the injured patient with a traumatic pneumothorax. Definitive care involves recognition of the injury (which is vital as any pneumothorax will expand with rising altitude of air evacuation) and insertion of an intercostal catheter. Performing the catheter insertion in the local hospital before flight is far preferable as conditions are generally more controlled and more assistance is available.
Air transport places certain physiologic and psychologic stressors on the acute patient. As a useful guide to help mitigate these stressors, always prepare the patient as if they are to have major surgery (see below). The airway must be patent and breathing and circulatory status should be optimised. Venous access should be secured and adequate monitoring of vital signs, including urine output with a bladder catheter, begun. Ideally the critical patient should be fasted. Adequate analgesia and judicious pre-flight sedation is vital for the anxious patient in pain. Fracture immobilisation will further assist adequate analgesia and reduce patient stress.
Once a patient is stabilised for transport, the same level of care should be maintained throughout the entire retrieval process until the definitive care location is reached. This has likely implications for staffing and fatigue issues in remote locations but the underlying principle remains the same.
For critically ill and injured patients, adequate preparation for transport uses the standard ABCDE approach.
- A-Airway (with cervical spine protection)
– A patent airway is the key goal.
– Use an oropharyngeal or nasopharyngeal airway, or consider intubation.
– If intubated, secure the endotracheal tube (ETT) and note & document its position. Use air in the cuff not fluid. This is a change from traditional practice based on research that air-filled cuffs are safer as the pressure can be measured with a manometer. Ensure that tube is well secured. Pediatric patients can extubate from simple neck extension or mainstem intubate from neck flexion. Very difficult airways may require consideration of heavy analgosedation with paralysis to ensure that the patient does not rouse and self extubate as monitoring in the transport environment is challenging and unpredictable stimuli may occur.
– If unable to achieve tracheal intubation, a laryngeal mask airway is acceptable.
– Consider possible spine and/or significant head injury and apply a cervical or towel tolls ( more comfortable) to either side of the head.
- B- Breathing
– Maintain adequate oxygen: all patients requiring oxygen on the ground will require more oxygen at higher altitude. Anticipate what oxygen supply will be required for the transport and ensure there is enough for reserve. Conserve portable oxygen supplies whenever possible by using wall oxygen of sending facilities until ready to move. Conserve batteries of ventilators whenever possible.
– Manual ventilation can be given and an Air Viva bag should be accessible.
– Ideally, insert an intercostal catheter for all proven haemo/pneumothoraces. Attach either a Heimlich valve (a flutter one-way valve to prevent air travelling back along a chest tube) or emergency chest drainage bag eg Portex
- C- Circulation
– Control any haemorrhage.
– Ensure IV access with a minimum of two cannulas (large bore if trauma or haemorrhage present).
– An intraosseous needle is acceptable as reliable access
– Make sure all lines and tubes are well-secured, with an accessible injection port and a needle-free system (if available).
- D- Disability and Disturbed behaviour
Note that an adequate trial of preflight sedation is vital and best conducted at the remote hospital/facility. Acute sedation during flight is risky (in terms of oversedation or failed sedation) with little margin for error. Disturbed patients can put the safety of staff, patient and aircraft at risk. Identifying and managing this issue prior to departure is essential. An uncooperative or combative patient is a contraindication to transport and must be adequately managed prior to transport. If patient cooperation cannot be achieved through negotiation and communication there must be consideration of the need for transport balanced with the interventions that might be required to make a safe transport including physical and chemical restraints as well as adequate numbers of team members. Police escort may be necessary and local involuntary mental health certification may be required.
– Document the level of consciousness using the Glasgow Coma Score (GCS).
– Report evidence of dementia, delirium or confusion to the transporting team.
– Warning the retrieval team in advance of any anxiety or aggression is paramount. A clinical pearl here is to consider acute nicotine withdrawal that may reveal itself during an air evacuation flight of significant duration ( >1 hr). Early institution of nicotine replacement therapy may markedly reduce the need for sedation during retrieval. Fear of flying should be addressed with reassurance, explanation and education about the aeromedical retrieval process. Steps to mitigate stressors include use of anti-emetics, safety restraints etc. Oral sedation (eg, diazepam) is acceptable (see below).
- E –Extended care considerations: consider the need for other care specific to your patient’s illness:
– Adequate analgesia and/or sedation.
– Use of anti-emetic (eg, prochlorperazine, ondansetron, metoclopramide).
– Spinal immobilization eg, vacuum mattress.
– Immobilisation of fractures (eg, splinting with a backslab or traction splints).
– Tetanus prophylaxis/antibiotics/wound dressings.
– IV infusions refilled for journey (no burettes).
– Rationalise therapies and minimize number of infusions.
– Consider thermal control – space blankets, limit exposure.
– Secure all tubing and empty all drainage bags before flight.
– Minimise contamination – remove wet/soiled clothes.
– Complete documentation/transport notes.
In preparing patients for transportation in the aeromedical environment it is also important to understand the key principles of aviation physiology and in particular the implications of a number of gas laws on patient care. Boyle’s law of gas volume expansion with decreasing pressure at altitude has a number of implications on both the patient and the equipment utilised by the retrieval team. The human body contains numerous cavities which are fully or partially closed and filled with gas. As changes in altitude occur the gas in these cavities will expand sometimes with dramatic consequences. In practical terms the most significant areas relate to gas trapped in the pleural space, within obstructed bowel, in the peritoneal space, orbit, ears, sinuses and cranium . As long as they are considered then there are potential solutions to these problems. One strategy is to reduce the altitude of the flight or even in some circumstances to pressurise the cabin to sea level. This is an option to varying degrees on most fixed wing aircraft but not if utilising a rotary wing platform. There are, however, a number of implications. Firstly to do so limits the maximum altitude the aircraft itself can fly at. Within the B200s utilised by RFDS this limit is between 15 000 and 18 000 feet. This limits the ability to fly around bad weather. The air is also more dense creating greater resistance for the aircraft engines to work against resulting in increased fuel requirements and as lower air speed due to friction. More fuel stops may result prolonging time todefinitice care. Turbulence is more likely to be encountered at lower altitudes. With trapped pleural gas such as a pneumothorax, a number of options are available. These include needle thoracocentesis, chest tube drainage or even the simpler technique of open thoracostomy whereby a scalpel, forceps and finger are used to dissect into the pleural cavity, thereby releasing the gas and leaving the wound open during transportation. Dr Renee Beer in conjunction with the CriticalCare Research Group at The Prince Charles Hospital in Brisbane has recently published a description of a variation of this technique whereby an intubating bougie is inserted through the thoracostomy and an endotracheal tube is railroaded over the bougie into the pleural cavity to act as a small chest drain but left open to air once again. Within the confines of a transport vehicle these open thoracostomy techniques are reportedly easier to perform but as effective as a formal chest drain for management of pneumothoraces. Note that these techniques can only be utilised in the ventilated patient where positive pressure ventilation will prevent the development of a sucking chest wound. Smaller pneumothoraces less than 20% in volume do not necessarily require a drainage technique to be undertaken prior to flight but this is a difficult decision where the clinician has to weigh up a number of factors. These include whether the aetiology is medical or traumatic, the cabin altitude, flying time, access to the relevant patient side in flight and the level of experience of the clinician.
Another example of the relationship between Boyle’s law and patient preparation can be seen in paediatric retrieval. Respiratory failure is more likely in critically ill children and is due to a combination of increased BMR, decreased Functional Residual Capacity ( FRC ), decreased lung compliance, V/Q abnormalities and a high alveolar ventilation / FRC ratio. Gastric dilatation is common in sick children and gas expansion at altitude can increase this dramatically leading to diaphragmatic splinting and a further fall in FRC. In the ventilated patient gastric dilatation can lead to significantly increased airway pressures. This can be mitigated to some extent by the placement of a nasogastric tube prior to flight.
Boyle’s law is important to consider in understanding the potential complications of medical devices, equipment and therapies that are affected by gas expansion. Typically medical devices filled with air or controlled by gas volumes will be affected by changes in altitude. As an example an endotracheal tube cuff filled with air must have its pressure monitored with a manometer and air volume released to ensure a safe cuff pressure at altitude then refilled with more air on descent as the cuff volume contracts. Some authorities had previously suggested filling the cuff with saline but this is now discouraged as research has indicated that small bubbles left in the saline filled cuff can still cause significant pressure changes at altitude.
Air filled splints similarly need to be monitored for pressure changes particularly on ascent where an increase in pressure can lead to circulatory compromise. Critically, full plaster or fibreglass splints on limbs need to be split prior to flight. Air bubbles in the plaster may expand significantly and as increased limb oedema can also occur at altitude the combination could lead to compartment syndrome.
Some transport ventilators will change their delivered tidal or minute volumes at altitude, notably the early Drager Oxylog models. The use of a Wright’s spirometer attached to the ventilator was an option to monitor this change at altitude but many modern ventilators including the Oxylog 3000 have completely compensated for this barometric induced change.
Dalton’s law of partial pressures is very relevant to the transport of a patient with acute or chronic respiratory conditions. A hypoxic patient at sea level is not going to improve at altitude! A patient with acute respiratory failure at sea level will deteriorate at altitude if nothing is done to optimise oxygenation during flight. In practical terms the simplest intervention is the provision of supplemental oxygen. There exist complex formulae that attempt to calculate the required oxygen concentration for a given altitude and indeed there is a hypoxia altitude test that can help determine which patients will become critically hypoxic if subjected to altitude. These may be useful in elective transfers such as a planned international repatriation of the patient with severe chronic airflow limitation but in most aeromedical retrieval scenarios they are impractical to apply due to time constraints medical urgency. It is more important to undertake a clinical assessment of the patient’s respiratory status, including an arterial blood gas analysis if available but ultimately to err on the side of providing supplemental oxygen sufficient to maintain mental alertness, comfort of the patient and appropriate oxygen saturation levels as a minimum.
A controversial topic in aeromedical retrieval is the use of non invasive positive pressure ventilation via face mask to improve oxygenation and ventilation in the acute respiratory failure patient group. It is reasonably argued that this is an evidence based treatment from hospital experience that clearly benefits patients such as those with exacerbation of chronic obstructive pulmonary disease and cardiogenic pulmonary oedema. It is also reasonably argued that this intervention carries risks in terms of inducing vomiting and increasing aspiration risk and that all such patients should undergo early intubation to secure their airway for aeromedical retrieval, if face mask oxygen therapy is not improving their oxygenation. A further and important argument to consider is that just because evidence exists for a treatment within the hospital setting does not mean equivalent results would be obtained in the aeromedical setting. The author’s experience in using this modality on fixed wing transfers has been a positive one as any patient benefit, or lack of, can be determined very quickly and therefore the decision to intubate, if ultimately required, is not delayed excessively.
Henry’s Law relating to solubility of gases has relevance in the patient group with dive related decompression illness. As pressure decreases with ascent dissolved Nitrogen can rapidly emerge from solution in blood leading to bubble formation and potentially catastrophic consequences. This group may deteriorate rapidly with altitudes of only 200ft above sea level. The use of sea level cabin pressure has become the mainstay of long distance aeromedical transport for these patients. Alternatives do exist for consideration by services whose case mix requires a frequent use of a modality that will allow for transfer under pressure.
One example is the SOS Hyperlite which is marketed as the world’s first hyperbaric stretcher which allows for hyperbaric treatment to be maintained at cabin altitudes up to 18 000 feet.
Exposure to high altitude can also precipitate altitude related decompression illness in healthy individuals without recent exposure to SCUBA diving. However, there is very little evidence that this could occur below a cabin altitude of 18 000 feet and the incidence between 18 000 and 25 000 feet is very low.
Psychological Considerations
It might sound surprising but in one study about 1 in 7 patients on aeromedical retrievals had never flown before in their life. Fear of flying is a well recognised phobia and can be very challenging to manage if not considered with the retrieval patient. The simplest strategy in this case would be to arrange alternative transport but this is often not a practical solution. Sometimes, simple explanation and reassurance is sufficient with appropriate education about the purpose of the retrieval and the medical benefits of transport as well as an adequate cabin safety briefing. Alternatively the use of oral benzodiazepines may alleviate the anxiety. Paediatric patients are often fascinated by aircraft but when put alone in the back of a retrieval helicopter with a stranger can suffer extreme stress. Separation from parents will usually compound the anxiety state of the sick child in this hostile environment. Whenever possible the presence of a parent can go a long way towards helping facilitate a smooth and safe transfer. Whilst this may be possible in many fixed wing transfers it is not usually an option in the rotary wing environment. Further it is recognised that the presence of a parent can often induce stress in the retrieval team and this is an issue that needs to be discussed openly between team members.
In the psychiatric patient group requiring aeromedical transport, the aircraft cabin is often reported as being claustrophobic, restrictive and anxiety provoking. It is important that the retrieval team try to assess and address these issues before flight if it is reasonable to do so. Simple measures to manage common causes of agitation might include the provision of food and drink for hunger and thirst. Toileting prior to flight is prudent to relieve a full bladder or bowel. Nicotine withdrawal on long flights is a common cause of agitation and assessing the likelihood of this occurring and offering simple management strategies is often worthwhile. A quick smoking history will rapidly establish the likelihood of nicotine dependence and the need to offer some mitigation against withdrawal symptoms. The simplest strategy is allowing a cigarette consumption prior to flight. Alternatively, predicting the likelihood of this occurring well before the arrival of the retrieval team/aircraft and requesting over the phone the application of a nicotine replacement therapy skin patch is a strategy the author has found to be successful on multiple occasions in reducing the need for sedation on retrieval for unexpected agitation.
Social Considerations
It is often forgotten that the process of aeromedical retrieval and transport is by its very nature, a dislocating experience, removing a patient from their primary social locus of family, friends and community. Having said that, an increasing number of aeromedical transports are also for the repatriation of patients back totheir local communities, a reversal of this experience. Whilst this issue may seem insignificant to some, in others it is extremely significant. In cross cultural settings such as Australian Indigenous communities, the issue is of particular relevance. It is not uncommon that in these communities, patients with serious medical and/or surgical conditions may resist recommendations to travel to tertiary hospitals due to the fear of leaving their cultural locus and networks. It is important to remember as an aeromedical professional that the process of acute retrieval can be a substantially traumatic one with elements of not only the physical illness or injury for the patient to cope with but the compounding factors of dislocation and removal from supportive networks. On a more practical level there may be issues of consent for minors and language barriers to navigate during retrieval. Simple strategies to address these issues range from planning for a family escort to accompany the patient, to allowing opportunities for family and friends to say goodbye and ask questions about the patient’s expected clinical course and treatment after retrieval. Inquiring and documenting advanced care directives or the need for interpreters or cultural liaison assistance at the receiving facility is often prudent. Education and advice about what to expect on arrival at the receiving facility can be very helpful to patients and their family. To illustrate the practical issues that social factors may play in transcultural settings on retrieval, the author was involved in a psychiatric retrieval for a young Indigenous man from a remote community, who was experiencing first episode psychosis. His family refused to allow him to take medication or be retrieved until they had performed a traditional healing ceremony. It would have seemed an easy option to call police and enact the involuntary mental health act to detain and treat him against his will. However after the ceremony was allowed to occur in the clinic, the family and patient fully accepted all medical treatment and retrieval without resorting to involuntary detention.
In summary adequate patient preparation is the cornerstone of good aeromedical retrieval management. It can be all too easy to get overly focussed on one aspect of a patient’s management, usually the critical care elements of resuscitation and stabilisation, whilst forgetting important clinical, psychological and social issues. A holistic approach to patient preparation will benefit both the transport and the patient’s ultimate outcome.
Further Reading
3. Beer RG, Grimmett WG et al. Appraisal of the endotracheal tube as an alternative to the intercostal catheter. Emerg Med Australas. 2010 Dec;22(6):573-4
4. Laura Demmons. Anxiety in Adult Fixed Wing Air Transport Patients. Air Medical Journal 1997;16(3):77-80.
5. Allen MH et al. Effect of nicotine replacement therapy on agitation in smokers with schizophrenia: A double-blind, randomized, placebocontrolled study. Am J Psychiatry 2011 Jan 18; [e-pub ahead of print]
6. Deakin CD, Davies G et al. Simple Thoracostomy Avoids Chest Drain Insertion in Prehospital Trauma .The Journal of Trauma: Injury, Infection, and Critical Care: Volume 39(2), August 1995, pp 373-374
7. Flynn JG, Singh B. The performance of Drager Oxylog ventilators at simulated altitude. Anesthesia & Analgesia 2008;36:549-552.
Prehospital and Retrieval Medicine - THE PHARM dedicated to the memory of Dr John Hinds 
In your article, you stated that It is not uncommon that aeromedical transport involves patients with life-threatening injuries or illnesses and the prospects of death occurring during transport are very real. While my brother and I were on a road trip last week there was a bad accident on the freeway that required someone to be airlifted to the hospital. I wonder if every hospital has their own helicopters or if they have to hire them out. https://www.angel-flights.com/services2.html
Generally leased aircraft rather than owned by hospital
I didn’t realize that an increase in altitude could make it worse for circulation in a medical flight. That would be really important to know if a person was bleeding bad or something like that. You wouldn’t want to go to an altitude where bleeding could be made even worse.
Minh just finding this and its such a help for my current studies. Can’t think you enough!
You’re welcome!
ABCDE – for recall and check list is great