Identifying NSTEMI made easier?
Chest pain is a frequent reason for contact with the emergency medical services (EMS). However, it has multiple aetiologies and only a small number of patients are having a myocardial infarction (MI). Risk-stratification for MI is important in order to initiate timely treatment but is typically based upon a 12-lead electrocardiogram (ECG). The limited sensitivity of a 12-lead ECG means that non-ST-elevation myocardial infarction (NSTEMI) can be difficult to identify—yet still requires timely intervention.
This Norwegian study aimed to evaluate the feasibility and diagnostic accuracy of prehospital acquisition of the combination of ECG, point-of-care Troponin T (TnT) testing and transthoracic echocardiography (TTE) by paramedics in identification of NSTEMI. The study ran for just over 2 years and included 253 patients who had called an ambulance with chest pain. In addition to the usual ECG, one ambulance was equipped with TnT testing and a TTE scanner. The TTE results were transferred to an in-hospital cardiologist for review. Paramedics received additional training in TnT testing and TTE scanning.
Of the 253 study patients, NSTEMI diagnosis based on an interpreted ECG, TnT result and interpretable TTE images, were possible in 217 (86%) of patients, suggesting that paramedics could feasibly carry out the tests. There was increased on-scene time; this was short for TnT (no times given) and a median of 11 minutes for TTE was recorded.
There were 22 (9%) patients with a discharge diagnosis of NSTEMI and 82% of these were identified in the prehospital phase. Six of those patients went to the local hospital and 16 were admitted to the percutaneous coronary intervention (PCI) hospital. Notably, time from first medical contact to coronary angiography was 137 minutes (IQR 96, 118) in the PCI hospital and 1147 minutes (IQR 160, 1343) in the local hospital. Overall, this study highlights that the identification of NSTEMIs in the prehospital setting is achievable. However, the small scale and specific demographics suggest a larger study is required to increase validity and generalisability.
Applying pressure to the usual care package
Continuous positive airway pressure (CPAP) provides ventilatory support without the need for an endotracheal tube and has been used increasingly as a treatment for acute respiratory failure (ARF) and alleviating respiratory distress in the hospital setting. Some ambulance services have introduced CPAP for use by paramedics in the prehospital setting. However, there is limited and inconclusive evidence of efficacy.
This randomised controlled trial set in Australia aimed to assess whether the prehospital use of CPAP by paramedics reduces breathlessness (dyspnoea score and Respiratory Rate (RR)) and reduces hospital length of stay in patients with severe respiratory distress attended by emergency medical services (EMS).
Patients were screened for eligibility by the attending study paramedic and were considered for enrolment if they were over 40 years of age with acute severe respiratory distress of non-traumatic origin, had a RR of >22 breaths/minute and were unresponsive to at least 5 minutes of initial treatment. A total of 708 patients were randomly assigned to usual care (n=346) or CPAP (n=362). Those randomised to CPAP had a greater reduction in dyspnoea scores (CPAP −3.5, IQR −5.2 to −2.0 vs usual care −1.0, IQR −3.0 to 0.0), and RR (CPAP −8.0, IQR −14.0 to −4.0 min-1 vs usual care −4.0, IQR −9.0 to 0.0 min-1). Notably, there was no difference in hospital length of stay.
There were 37 patients (10.3%), who were unable to tolerate CPAP and thus had it removed prehospitally following unrecorded periods of time. The reasons for failure to tolerate were well documented in 18 cases and included anxiety/claustrophobia, patient deterioration, and problems fitting the mask. The remaining 19 cases were recorded simply as ‘unable to be tolerated’.
Adverse events were rare. Therefore, in this study, the use of CPAP by EMS paramedics was more effective than usual care in reducing dyspnoea and tachypnoea in patients with acute respiratory distress, with no increased risk of adverse outcomes.