One of the fundamental tenets of ambulance practice is the amelioration of patients' symptoms. Effective and timely treatment whilst in the ambulance can have a significant and positive impact on the prognosis of patients who are transported to the emergency department (ED) (Ducros et al, 2011).
Calls to patients suffering from difficulty in breathing (DIB) secondary to congestive heart failure (CHF) comprise a significant portion of emergency ambulance crews' workload. Indeed, heart failure is a worldwide major cause of mortality and morbidity, with its acute exacerbation being a leading reason for the hospitalisation and intensive therapeutic treatment of patients aged >65 years in the USA, Europe and Australasia (Fonarrow, 2008).
Continuous positive airway pressure (CPAP) is an established in-hospital therapy for the treatment of multiple aetiologies of breathlessness, primarily for acute cardiogenic pulmonary oedema (ACPE) due to acute exacerbations of CHF, but also (amongst others): exacerbations of chronic obstructive pulmonary disease (COPD), asthma and pneumonia (Gray et al, 2009; Wesley et al, 2011).
The use of CPAP as an adjunctive treatment for ACPE patients in front-line ambulances has been proven to improve patient outcome, preventing them from reaching the ‘point of no return’ and a downward spiral into total respiratory failure. In turn, this reduces the number of patients that will eventually require endotracheal intubation (ETI) (both pre-hospitally where available, and postadmission). This obviates further and more invasive therapies, such as the requirement for ongoing mechanical ventilation. Avoiding the need for intubation also prevents exposing the patient to the possible acquisition of hospital-acquired infection (HAI); the need for long term intensive care unit (ICU) admission (with concurrent cost/expense) and ultimately reduces mortality (Peter et al, 2006; Allen and O'Connor, 2007; Hsieh, 2012).
It is therefore appropriate to consider the benefits of any therapies that will reduce suffering and improve outcome for such a large group. This article will discuss current UK ambulance practice and examine the issues surrounding the introduction and use of CPAP as an adjunctive therapy in the treatment of ACPE, secondary to acutely exacerbated CHF, whilst also briefly discussing its use in other aetiologies of breathlessness.
Current practice
Current UK ambulance guidelines (Joint Royal Colleges Ambulance Liaison Committee (JRCALC), 2013) advocate the use of nitrates (in particular, glyceryl trinitrate) as the first-line treatment of ACPE. Nitrates act to reduce both preload and afterload to the heart, reducing overall cardiac workload. Whilst noting that furosemide administration has been standard treatment for ACPE for many years, the guidelines acknowledge that there is very little ‘high level’ evidence for or against its use in the treatment of ACPE. Furosemide is recommended for use only secondary to nitrates. Owing to the possibility of misdiagnosis (due to heterogeneity of symptoms), if a wheeze is present on auscultation, beta-agonists (salbutamol) may also be given in order to take into account the bronchodilation requirements of co-morbid COPD/asthma patients. Oxygen administration is recommended in patients whose oxygen saturation levels (Sp02) are <93%. The problem here is that purely increasing the fraction of inspired oxygen (FiO2) does not increase the rate of gaseous exchange in the case of collapsed airways/atelectasis, as the affected alveoli don't contain any air (Scottish Intensive Care Society, 2013). CPAP therapy corrects this by re-inflating the collapsed airways (Mattera, 2011).
JRCALC guidelines acknowledge that CPAP is recommended for pre-hospital use by experts in the respiratory field and advocate its use (where available) in the treatment of ACPE. They further acknowledge its positive effects on reducing the severity of acute left ventricular failure (LVF), improvement in survival to hospital discharge, reduction in intubation rates, and fewer complications in patient condition associated with its use. Despite this, the equipment is not currently included as standard equipment on front-line UK ambulances.
Overseas use
Ambulance CPAP has been used in other countries for a considerable time. In Europe, it has been used pre-hospitally in Finland for 20 years, with additional trials recording its successful use in France and the Netherlands (Kallio et al, 2003; Plaisance et al, 2007; Dieperink et al, 2009; Ducros et al, 2011). It is used most extensively in Canada and the United States (Wesley et al, 2011). A recent Canadian study into the use of pre-hospital CPAP canvassed 50 American states regarding its use by their emergency medical services (EMS). Of the 26 states that had implemented paramedic-led CPAP treatment within their EMS, 13 had further sanctioned its use by non–paramedic qualified emergency medical technician (EMT) level crews (Cheskes et al, 2012).
How does CPAP work?
CPAP works by placing a simple, tight-fitting positive pressure mask over the patient's mouth and nose. This off-loads the patient's respiratory effort, gives them a resistance to breathe against, and reduces their work of breathing by increasing positive end expiratory pressure (PEEP) above that of atmospheric air pressure (normal physiological PEEP is 5 cmH2O).
Patients often attempt to increase this ‘back-pressure’ themselves by breathing out through pursed lips. The extra pressure acts as a splinting force and prevents further atelectasis from developing, whilst opening collapsed alveolar structures. It also reduces pulmonary oedema due to this increased alveolar pressure pushing fluid through the alveolar wall and back into the pulmonary capillary bed. The increased intrathoracic pressure generated by CPAP reduces cardiac workload and circulatory congestion. The patient's shunt/ventilation/perfusion (V/Q) mismatch is reduced, and areas of the lungs that are either adequately perfused with blood, but are not ventilated due to alveolar collapse, or are ventilated but not well perfused due to poor pulmonary blood flow, become available again for gaseous exchange, leading to an increase in oxygen saturation level and a concurrent reduction in carbon dioxide levels.
The equipment is oxygen driven, which improves the FiO2 available to the patient, further increasing Sp02 levels (Kallio et al, 2003; Kumar and Clark, 2009; Mattera, 2011).
Early application of CPAP has a marked effect
Some of the most compelling evidence for the use of CPAP in emergency ambulance care was provided in a randomised French study by Plaisance et al (2007). This research involved the initial assessment of 176 patients with ACPE, of whom 52 were subsequently excluded from the trial due to co-morbid conditions. This trial was divided into three successive 15-minute periods, with observations being taken at the end of each period. Each patient was randomised to receive CPAP either immediately, together with standard therapy, for 15 minutes (63 patients), with CPAP then being withdrawn, or to receive standard therapy alone for the first 15 minutes (61 patients), followed by CPAP for the next 15 minutes. For the final 15 minutes, neither group received CPAP. Observations of heart rate, respiratory rate, dyspnoea clinical score (Table 1), blood pressure and arterial blood gases were taken after each of the three 15-minute periods. The trial established that only 15 minutes of CPAP resulted in reductions in patients' DCS and increased blood PH (they became less acidotic). Beneficial reductions in respiratory rate, heart rate and systolic blood pressure were also noted. Further requirement for ETI was also assessed, with only one patient of the early CPAP cohort being intubated compared to eight in the late CPAP cohort. Of the 10 patients from this study who died during their subsequent hospital stay, two were from the early CPAP cohort and eight from the late cohort. This study reinforces the efficacy of CPAP as a treatment for ACPE, whilst further demonstrating improved outcome associated with its early application.
| Dyspnoea evaluated by the patient | Points |
|---|---|
| None | 0 |
| Light | 1 |
| Marked | 2 |
| Severe | 3 |
| Auscultation rates/intensity | |
| None | 0 |
| Light | 1 |
| Marked | 2 |
| Severe | 3 |
| Cyanosis: | |
| No | 0 |
| Yes | 1 |
| Accessory respiratory muscles use | |
| None | 0 |
| Light | 1 |
| Marked | 2 |
| Important | 3 |
| Total | /10 |
In a Canadian randomised study by Thompson et al (2008) into the effectiveness of out-of hospital CPAP use by recently trained ambulance crews, the requirement to perform ETI either in the field or post-hospital admission was the primary outcome measure. In the non-CPAP group, 50% of patients required intubation and 35.35% died (12/34), as against a 20% intubation rate 14% died (5/35) in the CPAP group.
CPAP benefits
Initial beneficial effects of CPAP application include rapid improvements in oxygen saturation, with commensurate therapeutic reductions in heart rate, work of breathing respiratory rate and both systolic and diastolic blood pressure.
Studies have shown benefits from first-line CPAP use in exacerbations of COPD and also in asthma (some equipment groups have a facility for in–line nebulisation by the simple addition of a T–piece into the pressure circuit). Due to its ability to re-inflate alveoli, and aid in the dispersal of the fluid they contain, thereby increasing the amount physical surface available for gaseous exchange, CPAP has also proved beneficial in the treatment of community acquired pneumonia (CAP) and other pulmonary infections (Cosentini et al, 2010).
CPAP use has been associated with reduced length of hospital stay, the prevention of ICU admissions through its timely use, and a reduction in intubation requirements of up to 60% in acutely exacerbated patients. This reduction in ETI results in fewer complications in treatment, with a much-reduced risk of HAI and consequently improved rates in survival to hospital discharge. Another benefit to the patient is in preventing the chance of them becoming ventilator dependent, and the subsequent difficulty in weaning them from such high dependency and costly facility (Wesley et al, 2011).
The financial cost of CPAP
Hubble et al (2008) conducted a study to estimate the cost-effectiveness of CPAP, as part of an urban emergency medical service (EMS) system, in the treatment of pre-hospital ACPE. Total costs of the implementation of CPAP therapy, to include equipment, consumables and staff training were $89 (£54) per individual application. Hubble used the assumption that CPAP would be used on four out of every 1 000 patients attended, and expected that 0.75 patients lives would be saved per 1 000 attended, at a cost of $490 (£299) per life saved. Further, it was expected that CPAP use would result in one less intubation for every 6 patients treated, reducing the cost of hospitalisation by $4 075 (£2 484) per year for every use. Hospital records indicated that each intubated and mechanically-ventilated patient would require an additional 4.98 days of hospitalisation. It was assumed that these additional days were all ventilator days, resulting in additional costs of $24 986 (£15 229). Net annual savings, after the deduction of CPAP implementation costs, were assessed as $489 031 (£298 062). The study therefore concluded that pre-hospital CPAP treatment in an urban EMS system appeared to be cost effective (Hubble et al, 2008).
In a cooperative arrangement in Houston, Texas, a hospital organisation bought CPAP systems for local EMS systems at an initial implementation cost of $250 000 (£152 374). They assessed that they had fully recouped these costs six months later due to a reduction in ICU admissions credited to CPAP use (Hewitt and Persse, 2009).
Diagnostic accuracy
Varying levels of diagnostic accuracy have been reported in trials of pre-hospital CPAP. Of note, the misdiagnosis rate in the study by Kallio et al (2003) was 31%. In this study, patients were diagnosed with ACPE and treated with CPAP by experienced ambulance physicians in a mobile intensive care unit.
Hubble et al (2006) argue that the heterogeneity of ACPE symptoms, often confused with those of exacerbated COPD and pneumonia, means that a measure of pre-hospital misdiagnosis is inevitable. The study further argues that it would be unreasonable to expect paramedics to have a better diagnostic accuracy than that proven in physician–led studies.
It is therefore acknowledged that an element of misdiagnosis and therefore misapplication of CPAP is inevitable in the field. Dieperink et al (2009), whose CPAP study correctly assessed 26 of its 32 patients as suffering from ACPE (an 81% success rate), noted no untoward effects in the patients to whom CPAP treatment was applied and whose dyspnoea was subsequently proved to be of different aetiology.
In 2005, the EMS crews of Bellingham and Whatcom County, in Washington State, USA, adopted CPAP for use in patients suffering from respiratory distress secondary to acute heart failure. When the difficulties of exacting an accurate diagnosis of ACPE were recognised, they simply implemented a new protocol. They used available literature to support their addition of COPD, asthma and several other conditions to the list of those that could be treated with CPAP (Wayne, in Wesley et al, 2011).
Adverse effects
Hubble et al (2006) notes that in a cohort of 120 CPAP-treated patients, four (3.3%) became hypotensive, with a systolic blood pressure <90 mmHg, two patients (1.6%) suffered a degree of gastric distention, and 23 patients (19%) were initially intolerant to the CPAP mask—but only one patient had to have therapy discontinued as a result. In Plaisance et al (2007), where 124 patients were treated with CPAP, none of the above side effects were noted. Plaisance et al further cite that this lack of serious side effects, coupled with its efficacy when used as an early intervention, lends strength to its recommendation for CPAP use as a first-line therapy both in hospital and pre-hospitally.
An added advantage of CPAP as a therapy is that it can simply be withdrawn in the event of any adverse effects (such as hypotension/gastric distension/mask intolerance/vomiting) without the need (as with some drug treatments) for the given dose to take its course.
Training requirements
A 2012 Canadian study evaluated the feasibility of CPAP use by basic life support trained staff—primary care paramedics (PCPs)—by comparing their compliance in its correct use with that of advanced care paramedics (ACPs), who are advanced life support trained. These paramedics, who all worked within two selected EMS organisations, completed the same training. The training consisted of a pre–course self-study programme, followed by a six-hour anatomy and physiology revision package. This revision concentrated on airway anatomy and the physiology of ACPE and COPD. Training staff from each of the two participating EMS organisations were themselves trained on the specifics of the equipment they would be using by in-hospital respiratory specialists. This training was then cascaded to front-line staff. Mask fitting, patient tolerance of the devices and equipment troubleshooting were all covered/demonstrated. Paramedics were obliged to undertake both written and practical assessment scenarios, using manikins and their colleagues and to practise the fitting of equipment.
Standard application protocols were established, and the study results showed a combined (PCP and ACP) compliance rate with these protocols of 76.8%, as used on 302 patients. This study was designed to assess the compliance of crews with the established CPAP protocol, but also positively demonstrates the practicality of its use by various grades of ambulance clinician (Cheskes et al, 2012). Interestingly, the value of CPAP as a treatment method can be taken as already presumed by the commissioners of this study, as its primary end point was solely concerned with staff adherence to the published indications for its use.
Ease of use and practicality
In Thompson et al (2008), the practicality of rural CPAP use is questioned due to the presumed requirement for prohibitive quantities of bottled oxygen.
Dieperink et al (2007) and Taylor et al.(2008) allay these fears, giving the O2 requirements of their CPAP equipment as 5–20 litres per minute dependent on CPAP demand. They used a two-litre cylinder, pressurised at 200 bar and containing 700 litres of O2 whilst outside the vehicle, and transferred to one of a pair of vehicle–mounted 15-litre cylinders, each containing 3 000 litres of gas, when on board the ambulance. Vehicle supply was adequate to maintain CPAP for 60 minutes. Given the comparable O2 stocks on UK ambulances, current gas stock should prove sufficient even in the most rural of cases.
Modern CPAP equipment is portable and easy to use, with no reported complications in its usage during ambulance trials. In some States in the USA, it is cleared for use by non-ALS trained ambulance crews.
Readily available and proven training programmes, as established by other ambulance organisations, mean that set-up costs are minimised. There is no requirement for the adaptation of vehicles due to the simple nature of the commercially available equipment.
There are several commercially available CPAP equipment groups that fulfil the requirements of ambulance use, but no specific recommendation as to manufacturer is made in this article.
Conclusions
The well-documented physiological improvements associated with early CPAP use, together with the reported consequent reductions in demand on hard-pressed and expensive long-term clinical care this use brings about, make a very strong case for its expeditious introduction to front–line ambulances. It has been shown in this article that its introduction is justified both clinically and financially.
Current JRCALC guidance on the treatment of heart failure tells us: ‘CPAP should be utilised where equipment and suitably trained personnel are available’ (JRCALC, 2013).
The training burden for its introduction would be negligible, as initial education of front-line staff could be carried out as part of the ongoing annual essential education programme. Trainee staff could have it included as part of their training in the management of respiratory conditions.
Bespoke protocols for CPAP use can easily be developed from the multitude of examples already in use by other emergency care providers.
Furthermore, and from a public perspective, current failure to implement what is widely acknowledged as a relatively inexpensive and effective therapy, recommended by a national guiding body for the treatment of a prominent health condition, could lead to allegations of unprofessional oversight, sub-optimal/poor patient care, and possibly even negligence.