Content for  TR 22.826  Word version:  17.2.0

Ultrasound is an opportunity for emergency care in the ambulance. It significantly improves the management of prehospital care (first diagnosis, intervention and triage) and reduces the "door to diagnosis and therapy time", which is one of the most important factors in improving medical assistance and survival (as described in [27]):

• Examination must be rapid, not more than 2-3 minutes. For example, pre-hospital focused assessment with sonography in trauma usually takes no more than 3 minutes
• Identification of lung sliding to diagnosis pneumothorax, and the evaluation of abdominal aorta usually lasts less than 1 minute. Heart studies during cardiopulmonary resuscitation should be performed in 10 seconds during the rhythm check.
• The exam should answer specific yes/no questions, i.e., Is there a pneumothorax? Is there free fluid in the pleura, pericardium and peritoneum? Is there an aortic aneurism? Are the lungs wet or dry?
• Trauma, respiratory insufficiency, shock, cardiac arrest and severe abdominal pain, prior medical records should all be used to rule in or rule out an abdominal aortic aneurism
• Pre-hospital triage, airway management, obstetric emergencies

eMBB and URLLC will enable effective tele-guidance of an ambulance nurse by a remote expert to significantly improve diagnosis, treatment and compliance in a medical emergency. In this situation, ambulance nurses are able to obtain adequate ultrasound image capture and perform examinations as accurate as those performed by physicians. In addition, it allows to direct the patient to the specialized centre best suited to his condition, to inform the hospital team of the specific injuries (especially make all necessary preparations for the patient, e.g. prepare the OR and call all necessary medical staff), so as not to waste precious time between the time of the accident and that of the treatment and to ensure transport with greater safety. The hospital may be far away from the patient and ambulance, so a patient may not survive or will succumb permanent damage during transport if a real time interaction between paramedics and remote experts is not triggered immediately at the site of the intervention. Statistics from e.g. the National Health Service NHS in the United Kingdom show that emergency calls are classified in different categories, where the most critical ones are as follow:

• Category A Red 1 calls, that cover cardiac arrests and patients who are not breathing anymore.
• Category A Red 2 calls, which are serious but less immediately time critical and cover conditions like stroke and fits.

A study [10] carried over 5 years for approximately 1000 Red 1 calls per year shows that the straight-line ambulance journey distribution was ranging between 0 and 58 km with a median value of 5 km and that an increased distance was clearly associated with increased risk of death (7.7% died for straight-line distances between 10 and 20 km and 1% of absolute increase in mortality is associated with each 10 km increase in straight-line distance). In this use case, covering also category A Red 2 calls, we will assume a straight-line distance below < 50 km for the ambulance journey. Ultrasound can help to diagnose, monitor and provide image guidance for interventions for a variety of serious conditions related to Heart, Lung, Brain, Obstetrics and Abdomen. Also, ultrasound is useful for patient monitoring during transportation, e.g. to detect increasing pneumothorax [27]. One specific disease where early ultrasound examinations helps to reduce mortality rate is the aortic aneurysm. Aortic aneurysm is usually an asymptomatic process with the following associated risk factors: male sex, age above 55 years, tobacco, cholesterol and family history of aortic aneurysm. It is a rather common disease (especially for men above 60 years old - 4 to 8%) whose evolution is systematically fatal. In the United States, approximately 11,000 cases of abdominal aortic aneurysm rupture are described per year. Of these, it has been estimated that 30% are misdiagnosed. The overall mortality rate for patients with abdominal aortic aneurysm rupture is 80 to 95%. For those who arrive at the hospital, the mortality rate is 50 to 80%. Once patients come to the emergency room, early diagnosis significantly reduces mortality from 75% to 35%. The speed of the implementation of the therapeutic chain (emergency physician-anaesthesiologist and surgeon) is a determining factor in the chances of survival of a patient with a fissure syndrome. However, the diagnosis of rupture of an aortic aneurysm is a real challenge for doctors. Symptoms are most often initially non-specific but can progress abruptly to a state of shock. The most common symptom is abdominal pain, which is intense, diffuse or lateralised on the left-hand side. To help, ultrasound in the ambulance is a rapid and effective examination allowing to diagnose a fissured-type aortic syndrome especially in case of abdominal aortic aneurysm.

This test is reliable, efficient but however requires some level of expertise not always available on the site of the incident as many first responders have no, or only basic training in echography. This leads to having paramedics in the ambulance performing the echography with the assistance from a remote expert who is able to guide them through the examination procedure. Efficient support involves being able to track paramedics gestures with enough precision, therefore sets limits on the acceptable latency while going thought all equipment along the path from the ambulance to the monitor in front of the expert. In general, we consider here gestures executed at the speed of 30 cm/s and with an expected accuracy of 1cm which gives us a total imaging system latency of up to 35 ms. Along the same principles as depicted in clause 5.2.1.3, but considering there isn't any heavy processing at the application side, one ends up with a below 20 ms one way end-to-end latency from the echographer to the application at the remote expert site. In a conservative approach for estimation of the communication service availability, consecutive frame loss or delays beyond service defined constraints shall only occur with a very low probability for the duration of the examination.

Joe, 78 years old, fell in his basement. The fall detector in his Personal Emergency Response System device (PERS-device) alerted the call centre but as they could not get him to respond they dispatched an ambulance. The ambulance must be equipped with devices for monitoring, examination and guided interventions like e.g. ultrasound probe, physiological signals monitors and, portable 4K smart glasses. Also instant access to medical records is important to understand the patient's condition prior to the incident. The Emergency Room (ER) and a local MNO have business contract in place by which the ER can ask the MNO (through suitable APIs) to allocate the necessary high priority resources fulfilling SLAs suitable to the transport of medical data (with special care taken on medical data integrity and confidentiality) over a geographical area covering the site of the incident. Each needed equipment (ultrasound probe, monitoring scopes, 5G enable 4K smart glasses …) is:

1. Powered up,
2. Subscribed to 5G communication services fulfilling agreed SLAs,
3. Attached to the local MNO 5G network,
4. Provisioned with parameters allowing establishment of a secure communication link to an authenticated application in the ER and/or hospital in charge of sharing incident data with the authorized personnel

With the ambulance, Fred, the first-aid caregiver arrived on scene and found Joe in the basement. Joe is conscious but complains about intense abdominal pain.

1. To check for internal bleeding and lung punctures, Fred pulls out his portable Ultrasound-device (US-device), which directly starts streaming securely ultrasound-data (US-data) to the Emergency Room (ER) through a 5G communication service fulfilling agreed SLAs, where it is analysed by Marc, the sonographer on call. The 2D US-data is a 20fps 512x512 pixels uncompressed image stream encoded using 32bits per pixel.
2. To allow Marc to provide optimal instructions on placing the US-probe, Fred also streams live 4K video of Joe's abdomen through the 5G wireless camera mounted on his smart glasses. The video is encoded using 12 bits per pixel color coding (e.g. YUV 4:1:1 [28]), supports up to 60 fps and is compressed with lossy compression algorithm. Based on the video and US-streams, Marc provides instructions to Fred (possibly using a video communication link) how to move the US-probe to assess Joe's abdomen (as an option Marc may even control a robot in the ambulance for the ultrasound capture.). Interactions between Fred and Marc (incl. the 4K video stream and the return communication link) are supported by a second 5G communication service with suitable SLAs. Apart from moving, Marc is able to control the operation of the US-device, e.g. to tune remotely the beam-forming parameters.
3. Seeing the ultrasound stream, Marc concludes abdominal aortic aneurysm fissure by noticing fluid accumulation in Joe's abdomen and a heterogeneous rounded ultrasound structure with an anechoic image corresponding to the light of the vessel at its centre. Marc concludes that Joe's condition is critical. Marc tells Fred to ask the driver to get Joe to the nearest hospital at the highest possible speed. Also Marc coaches Fred to use his fist to apply pressure to a specific point based on ultrasound guidance on Joe's abdomen to limit the bleeding.
4. Upon arrival at the hospital, the staff is waiting, the OR has been prepared and Joe is rushed there for immediate surgery. Resources assigned to communication services allocated to the Emergency Room are now released by the MNO.

The surgeon replaces the aorta with a vascular prosthesis that is sewn to the healthy aorta above and below the aneurysm. The surgery procedure is fully successful and Joe is kept under continuous surveillance in the hospital during eight days.