COVID-19 Manual Section 4: Biomedical solutions to Covid-19

Introduction

This section provides an overview of how biomedical engineering is contributing to the management of the COVID-19 pandemic

Justification

The use of medical devices in the COVID pandemic is the unfortunate indication that the patients are displaying severe respiratory distress symptoms and need a form of assistance to breathe.

Treatment mechanisms

Oxygen

The first form for mild respiratory insufficiency is usually the supply of extra oxygen through a nasal cannula or a more intrusive face mask. Most of the time, the oxygen comes in the form of cylinders, either small for portability or large for stationary patients and longer-term supply.

Oxygen concentrators represent an attractive alternative to tanks although this is not typically in use while caring for COVID-19 patients in hospital settings. Oxygen concentrators extract oxygen from the air on demand and supply it directly to the patient. Concentrators come in a variety of sizes from a portable shoulder bag form factor, to higher capacity stationary machines for patients who need oxygen 24/7.

Variants of oxygen supply include high flow nasal oxygen (HFNO) which delivers warmed and humidified oxygen, to avoid the drying of airways, at high flow rates - typically tens of litres/min) at body temperature and up to 100% RH and 100% oxygen.

Continuous Positive Airway Pressure (CPAP)

The next step up in treating COVID-19 patients is Continuous Positive Airway Pressure (CPAP) which is initially intended to prevent airways collapse in sleep apnoea patients, but has been shown to be beneficial to COVID patients if applied early enough in the progression of the disease.

A well fitted face mask is an essential component of a CPAP system and as such it is quite intrusive. CPAP is only appropriate for patients who are capable of some breathing strength as CPAP effectively opposes some resistance to expiration. Variants exist that either automatically adjust the level of pressure to the patients breathing characteristics (APAP) or have different levels of pressure for inspiration and expiration (BiPAP). CPAP usually supplies (filtered) air to the patient but most masks have a port for supplementing the supply with oxygen.

Ventilators

Patients who cannot breathe spontaneously need to be put on ventilator. Ventilators are capable of replacing the breath function and patients in an advanced state of respiratory distress are usually intubated and sedated at the beginning of the treatment.

Ventilators are complex systems providing the healthcare professionals with a lot of flexibility to adapt the assisted breathing settings and to be able to wean recovering patients off the ventilator gradually. Modern ventilators are typically closed loop pressure controlled and capable of detecting spontaneous breathing to synchronise assistance for recovering patients. They also enable the control of the composition of the gas the patient breathes from normal air to 100% oxygen, usually taking their supply from the hospital’s gas supply network but can also be coupled to oxygen tanks or oxygen concentrators if used in a setting where there is no gas network.

Ventilator Challenge UK

Back in March, pandemic modelling predicted that the UK could have an insufficient number of ventilators to cope with the upsurge of patients in intensive care units (ICU) requiring them. The Government launched the Ventilator Challenge, a nation-wide call to industry and academia to help mitigate the potential shortfall.

This saw a lot of consortia being formed developing new CPAP and more or less featured new ventilator designs or looking for ways to scale up the production capacity of existing ventilator models already manufactured and approved in the UK.

Ultimately, the need was thankfully less than initially anticipated, the production scale up efforts were sufficient and none of the new designs were put through the emergency approval process. This remains a fantastic demonstration of what the country's engineering community is capable of when faced with such a challeng3.

Patient monitoring

An essential element of the ICU equipment is the monitoring equipment. These keep track of some of the patient vitals, especially when they are ventilated and sedated but also during their recovery phase to ensure the regime of ventilation is optimised for their condition. Ventilators already provide their set of patient parameters, but usually patient monitors are separate devices as they continue to be useful after the patient can resume breathing on their own unassisted.

One of the key parameters for COVID-19 patient is the amount of oxygen in their bloodstream (SpO2), measured by pulse oximetry which uses optics within a finger clamp. Pulse oximetry tends to be used for the duration of the patient’s stay in ICU.

Modern patient monitors provide many more patient parameters all the way to breathing waveforms to enable clinicians to fine tune their care of the patients.

Innovating in a pandemic

Beyond the Ventilator Challenge mentioned above, the pandemic inspired engineers around the country to many innovations. This section list only a few of the innovations the authors are aware if and doesn’t mean to single them out from all the great work which is taking place.

Bioengineers at DNA Nudge developed the COVID Nudge< test from scratch during the pandemic.

A team at Imperial College in London developed JAMVENT, a low-cost emergency ventilator, developed in response to the COVID-19 outbreak. Its design is based on simple pneumatic components, but it is able to perform all the tasks required of an ICU ventilator for COVID-19 patients.

Management of the pandemic in hospitals

Personal protective equipment

The COVID-19 pandemic has evidenced the fragility of society and the need for effective and practical ways to protect it. For the general public, the use of face masks as personal protection equipment (PPE) remain the most practical line of defence against SARS-CoV-2 as well as other respiratory viral infections.

However, for the wide range of multidisciplinary health care workers more protection is required, as surgical or respirator masks, and these are not intended to be worn for so long as is required in an NHS shift. There is an environmental cost to these disposable items, they do not fit all face shapes, the mask-face seal can be broken while talking, and they apply pressure to the sensitive face skin which can cause discomfort and tissue injury.

From the patients' and carers' perspectives, they also obscure the face, which disadvantages people with hearing impairments who rely on lip reading - as well as a human face being reassuring.

Therefore, there is great need to develop new practical PPE technologies that can protect the population while ensuring a functioning society.  Several groups of engineers have been developing enhanced PPE technologies including powered air purifying respirators (PAPRs), similar to the commercially available devices were in short supply or removed from sale at the start of the pandemic.

These have the benefits:

  • being potentially more protective, as all the breathed air is filtered
  • because they include a hood which protects the face from droplets and self-infection by touching; avoiding mechanical loads on the delicate facial skin
  • being cleanable and reusable, so presenting a lower potential cost, and less plastic waste
  • being a more inclusive device, as they should fit all users, and permit lip reading and the care benefits of seeing your healthcare worker's face.

One example, the 'PeRSo' device, has received approval by HSE and BSI and was used in University Hospital Southampton in the first wave of the pandemic. The engineers involved released the design and specification Open Source.

Role of clinical engineers

Clinical engineers are pivotal in the use of technology as part of patient care, from procurement, to maintenance but also, and this is a little less known, working with clinician to produce innovative devices to enable novel treatments.

Rather than attempting to do them justice in many words, the reader is encouraged to watch the feature hosted by Vivienne Parry, that was put together by IPEM and IFBM for the recent Clinical Engineering Day 2020.

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Sylvain Jamais

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