The Department of Health (DH) approximates that 835 000 people have been diagnosed with chronic obstructive pulmonary disease (COPD) in England to date (DH, 2010), but it also estimates that over 3 000 000 people living in the UK are currently suffering with the disease. Emergency calls to patients suffering with acute exacerbation of COPD (AECOPD) account for a large portion of 999 call outs and it remains the second most common cause of emergency admission to hospital and the fifth largest cause of re-admission to hospital in England (DH, 2010).
In 2008 the British Thoracic Society (BTS) released new guidelines regarding oxygen use in the adult patient; providing evidenced–based guidance on how oxygen should be delivered to all adult patients, advocating the importance of appropriate oxygen therapy that included the potential risks of giving too much oxygen to the patient (BTS, 2008). Traditionally, there has been an instilled belief among ambulance staff that oxygen can do no harm (New, 2006), and therefore the flow rate of oxygen in the past has been tailored by each individual paramedic at thier discretion. This belief is currently being dispelled, as clinicians are developing the skills to review journal articles and understand the evidence and reasoning behind the changes in practice. It has been acknowledged in a recent audit that the use of oxygen to prevent hypoxia has improved and is being managed well with the use of pulse oximetry (Matthews, 2010/xref>). During 2009, the Joint Royal Colleges Ambulance Liaison Committee ( JRCALC) incorporated the suggested changes by the BTS into to their pre-hospital guidelines of oxygen administration, therefore reinforcing the need for change. Despite these changes in practice, could further steps (such as air driven nebulisation) be incorporated into pre-hospital treatment to provide a more appropriate care package for a patient presenting with an AECOPD that may be at risk of hypercapnic respiratory failure (type 2) due to over oxygenation.
COPD is a lung disease characterised by chronic obstruction of lung airflow that interferes with normal breathing and is not fully reversible (World Health Organization (WHO), 2012). During an acute exacerbation infection can be noted alongside signs and symptoms including, an audible wheeze, tachypnoea, use of accessory muscles, peripheral oedema, increased cyanosis and/or confusion (BTS, 1997). Respiratory failure is placed into two classifications; type 1 is hypoxia without hypercapnia and with an arterial pressure of oxygen (Pao2) of < 60 mmHg on room air, and type 2 is hypoxia with an arterial partial pressure of carbon dioxide (PaCO2) of > 50 mmHg on room air (British Medical Journal (BMJ), 2011).
Obviously, diagnosis cannot be confirmed until arrival in the emergency department when an arterial blood gas (ABG) can be taken. This does not mean, however, that pre-hospital clinicians should not be aware of the differences and the risk of this type of failure when treating an AECOPD. The BTS guidelines (BTS, 2008) recommend the use of an oxygen alert card that is given to any patient known to have had an episode of hypercapnic respiratory failure, or is at high risk, to ensure the correct amount of oxygen be given during emergency treatment. In a small study undertaken by Gooptu et al (2006), patients who were readmitted following distribution of an alert card where found to be less acidotic overall, following ABG results, suggesting that a card system along side patient and medical staff education could be used as an effective tool. It was also suggested that a larger study would be required, and would prove beneficial in determining whether the issue of the alert cards would have any effects on mortality rates, length of hospitalisation or the requirement of invasive or non-invasive ventilation.
‘This does not mean, however, that pre-hospital clinicians should not be aware of the differences and the risk of this type of failure when treating an AECOPD’
Current practice
Currently in the pre-hospital setting, recognised treatment of an AECOPD can incorporate the monitoring of oxygen saturation levels using pulse oximetry, aiming to keep the patient within the target ranges of 88 % and 92 % blood–oxygen saturation levels ( JRCALC, 2006; BTS, 2008).
Nebulisers can also be used for administration of bronchodilator therapies such as salbutamol and ipratropium bromide. These drugs are delivered via a nebuliser mask which is connected to a compressed air source, and compressed air is blasted through the liquid drug at a high pressure, the nebuliser then converts the liquid medication into aerosol droplets which are subsequently inhaled into the lungs.
Oxygen can be administered by a variety of delivery systems, including nasal cannula, standard and non-re-breather masks, which are classed as uncontrolled systems. While a venturi mask delivers a controlled oxygen concentration to the patient by drawing in a controlled amount of room air (21 % oxygen) and the required amount of oxygen from the cylinder. This is dictated by the flow rate to achieve an accurate delivery of 24 %, 28 %, 31 %, 35 % or 40 % oxygen to the patient. A study undertaken by Agusti et al (1999) concluded the venturi mask to be more effective in the accurate delivery of oxygen than a nasal cannula and the BTS advocate their use in the treatment of patients with AECOPD (BTS, 2008).
Are we over oxygenating?
At the time of writing this article, the author's locality of practice supply only nasal cannulas, standard and non-rebreather masks to deliver oxygen, and only stock oxygen cylinders to deliver nebulised drugs in the treatment of an AECOPD patient. Potential difficulties arise in administering controlled oxygen during pre-hospital treatment when administration of bronchodilators by nebulisation is required due to the oxygen flow rate being increased.
A standard nebuliser mask requires six to eight litres per minute (l pm) of oxygen connected to the device to enable the conversion of the liquid medication into a suitable mist to be inhaled. This process inevitably results in the administration of high-concentration oxygen therapy during the period of nebulisation. The BTS (2008) guidelines note that compressed air should be available for treatment of COPD patients but recommends that if this is not the case, oxygen-driven nebulisation should be limited to six-minute periods. This may limit the risk of hypercapnia to some extent, but it does not overcome the risks associated with the treatment, such as the need for frequent administration of nebulised drugs over long journey times. There is also potential for nebuliser masks to be inadvertently left in place for longer periods, as often the drug administration will not be completed within this six–minute guideline.
A quantitative study, designed by Edwards et al (2011), produced results showing that two oxygen driven bronchodilator nebulisations given in succession resulted in a significant rise in transcutaneous carbon dioxide tension (Ptc, CO2) compared with air-driven nebulisation in subjects with stable severe COPD. This study was designed to replicate the initial pre-hospital management approach to AECOPD. The conclusion summarised that the administration of bronchodilators via oxygen driven nebulisers resulted in increased hypercapnia in patients with severe COPD. Findings from this study suggested that pre-hospital health professionals need access to air-driven nebulisers to provide the most appropriate treatment for patients presenting with an AECOPD.
These points were also highlighted in an earlier audit of pre-hospital oxygen therapy. It was noted that ambulance crews could not administer a controlled amount of oxygen to patients with AECOPD requiring nebulised drugs, due to lack of equipment and that air driven nebulisers were not available (Mathews, 2010). Further studies also note a significant increase in complications during admission of patients that had received high concentration oxygen, suggesting that the use of controlled oxygen in AECOPD is an important therapeutic issue (Denniston et al. 2002; Durrington et al, 2005).
Evidence for oxygen delivery in AECOPD is available over several years alongside guideline changes, therefore raising the question; ‘why do pre-hospital health professionals not have access to appropriate driving gases for nebulisers, alongside accurate oxygen delivery devices?’ This question highlights the need for further research to collate information from ambulance trusts to understand their views and reasoning further.
Until such time, it could be hypothesised that there are several barriers to implementation, such as cost, infection control, training and suitable space within the ambulance to hold the new equipment. In any area of healthcare, cost is always a key component, however, these barriers should be overcome, especially in areas where it can be demonstrated that there will be an improvement in patient care.
Recommendations for practice
Delivery of nebulised drugs with air as the driving gas can be achieved in the pre-hospital environment with either a cylinder of compressed air or a compressor unit, this piece of equipment eing responsible for pressurising the air to produce the aerosol. These compressors require a power source, either via a mains electric supply or a rechargeable battery. With an initial outlay cost ranging between £40 and £320 (Nebulisers Direct, 2012) per unit and ongoing maintenance, training requirements and safe storage on the ambulance, this would not be the most financially viable method of implementing air driven nebulisers on board a front line vehicle.
While using a cylinder of compressed air would be easier to implement and minimal training would be required. In the authors experience the amount of compressed air cylinders required on each ambulance would be lower than cylinders of oxygen, as the compressed air will only be used during treatment of an AECOPD. Delivery of the compressed air cylinders could be included in current gas deliveries to station, therefore minimising expenditure. Currently, the average price for a cylinder of compressed oxygen is about £5.95 for 460 litres, with a compressed cylinder of air holding 640 litres costing £4.77 (British Oxygen Company (BOC), 2012). Storage facilities are already in place on the vehicles to safely store gas cylinders so implementing the compressed air cylinder into the vehicle should not be a barrier.
Although clear labelling of flow meters and cylinders within the ambulance is required. It is essential the ambulance clinician can differentiate between the oxygen and air outlets/cylinders, inappropriate delivery of the wrong gas could have serious implications to the patient. The risk for the incorrect gas to be administered, could be mitigated with a degree if initial training, and this could easily be achieved with individual learning packs. Patients would continue to receive treatment with individual disposable masks so there would be no increase in the risk of infection, while allowing oxygen treatment to be controlled during nebulisation with the use of a nasal cannula and maintaining oxygen saturations at the recommended target range. This would allow the patient to receive the appropriate nebuliser drug therapy, while minimising complications of hypoxia and the risk of hypercapnia from excessively high oxygen concentration.
Current practice within the ambulance service needs to be challenged, implementation of these changes would be in line with recommended practice in the BTS guideline (2008) for the treatment of AECOPD. While allowing the ambulance clinician to fulfil their registrant duties as Health Care Professional Council (HCPC) by acting in the best interests of the service user by following evidence–based practice (HCPC, 2008).
Conclusions
COPD is a chronic condition that affects thousands of people across the UK. During acute exacerbations of this disease, contact with a pre-hospital HCP is likely, assessment and treatment will commence immediately, and during this time ambulance clinicians will be solely responsible for the patient's clinical needs until arrival at definitive care. As discussed above controlled oxygen delivery alongside pulse oximetry is improving, but the prevention of over oxygenation is unable to be managed sufficiently due to the difficulties of achieving the same targets while the patient is receiving bronchodilators, due to lack of appropriate equipment and driving gases. The time spent in an ambulance can vary. Patients in rural locations may have very long journey times and encounter the need for repeated nebuliser treatments. Appropriate treatment should be a priority and the amount of oxygen delivered during treatment with bronchodilators is evidently just as important.
It appears evident that simple changes, such as air driven nebulisers could be used to improve the treatment of patients suffering an AECOPD while in the pre-hospital environment. Best practice suggests that oxygen saturations should be maintained between 88 % and 92 % during treatment and conveyance of a patient with an AECOPD to definitive care from the pre-hospital environment (BTS, 2008).
Therefore, drug treatment delivered via air– driven nebulisation alongside supplementary oxygen to prevent hypoxia, delivered via nasal cannula would improve overall patient outcome. This may incur a slight outlay in monetary terms but the cost would be minimal in comparison to the overall improved treatment AECOPD patients receive. As a result, this transition could potentially reduce in-hospital complications and improve patient outcomes with a consequent reduction in long–term costs to the NHS.