Tuesday 28th July 2020

COVID-19 therapy – from an aerosol expert´s perspective

Dr Voshaar, you warned very early on against deploying mechanical ventilation too early and too readily in COVID-19 patients. What shape does your therapy take and what do you do differently?

Of the 60 COVID-19 patients we have had, 57 only received non-invasive ventilation support with a mask or CPAP and were not intubated. Only one patient with a severe pre-existing neurological condition, one with pre-existing heart failure and acute viral myocarditis on top of that and one patient with asbestosis received mechanical ventilation. One of these patients died. The other two have since been taken off the ventilation and are on the road to recovery.

The standard therapy for all COVID-19 patients included close monitoring of the laboratory parameters D-dimer, LDH IL-6, BNP, and troponin daily or every other day. Every single COVID-19 patient in the Bethanien Hospital in Moers was given an inhalation therapy with 0.9% saline solution to reduce the viral load in the air they exhale. Some were given a mixture of salbutamol and physiological saline solution via a nebuliser. Physiotherapy, and PEP therapy in particular, was also an important component in the management of COVID-19 infections. As is similar with CPAP, the active use of a PEP system helps improve gas exchange, avoid or reopen microatelectases and mobilise secretions to promote secretolysis.

How did this prompt a rethink among attending physicians on an international scale?

Initially, there was a very heated and public debate on mechanical ventilation. Of course, worldwide the strategy was early intubation. It became quite absurd at times. Again and again, colleagues reported that patients had even been persuaded to be intubated. There was then much agreement internationally. Still, although there is now a widespread tendency to try to increase oxygen saturation without intubation, for example by conventional O2 administration using a nasal cannula or HighFlow systems, which also generate a slight PEEP, the indication for invasive mechanical ventilation is still being established far too early. In my view, we should not be basing the decision whether or not to intubate on individual parameters, such as O2 saturation or the Horovitz index.

In your hospital, which measures did you take to protect patients, colleagues, and nursing staff against infection?

We implemented a comprehensive hygiene policy in our hospital. When it came to PPE, we paid special attention to ensuring that the masks fit snuggly. The COVID-19 patients were put into single rooms with very restricted access. We communicated with patients using an intercom system and an app, and they were all constantly monitored via video. Non-vented masks were used for non-invasive and CPAP ventilation. All patients inhaled physiological saline solution to reduce the emission of bioaerosols in the air. Even though we did not practise it, the use of an exhalation filter, such as the PARI Filter Valve Set can generally be recommended for nebuliser therapy. All these measures worked well. Even though we had over 50 COVID-19 patients and acted as a supraregional testing centre, we did not have a single inhouse infection among our 1600 hospital staff.

Although we already know about this from flu, the risk of SARS-CoV2 airborne transmission was not taken into account for a long time. What considerations did you factor in from the very start?

Transmission via virus-loaded bioaerosols patients exhale appeared to be probable and plausible from the day one. My team and I realised this at a very early stage because we do, after all, have 30 years of experience in aerosol medicine and have always kept up with the latest expertise. Then there was a growing number of reports of SARS-CoV2 transmission that could not be explained by smear or droplet infection alone. The creation of what we call bioaerosols essentially depends on how deep someone is breathing, so singing, for example, can increase the risk of virus transmission.

With nebuliser therapy, on the other hand, we can assume that not much more virus-loaded aerosol will be generated than it is when the patient simply exhales. Nebulisation with isotonic saline solution even helps stem the spread of the virus.

How does the protective effect of isotonic saline solution help prevent a virus from spreading?

Based on a study by Edwards, a working group of clinicians and aerosol experts, it was discovered that inhalation of 0.9% NaCl solution can reduce the emission of bioaerosols by 72%. The German Society for Pneumology and Respiratory Medicine also included this in their position paper on the state of the art application of respiratory support.

It is assumed that bioaerosols are formed in the very tiny airways, the bronchioles, and alveoli. Very small aerosols are released by exhalation by a process called microburst, where very tiny bubbles rupture or where closed smaller airways reopen.

It is the change in physical properties that explains the protective mechanism provided by inhalation of physiological saline solution. Isotonic NaCl forms a thin film with high surface tension on the mucosal membranes of the airways. This promotes the production of relatively large aerosols whose size does not allow them to be exhaled when we breathe out. As a result of this, these droplets remain in the lungs and so fewer virus-loaded aerosols are released by exhalation. This makes the patient less infectious and the risk of transmission is reduced. In combination with an exhalation filter or a PEP system, I see the use of inhalation therapy as not only safe but helpful. In this constellation, inhalation therapy lends itself to continued use at home too.

What makes a good nebuliser system? What is important for COVID-19 therapy?

When selecting a suitable nebuliser system it is, in my view, very important that the device is easy to handle and very robust. A high aerosol output and a stable and adequate particle spectrum are also relevant features, as these ultimately determine how much of the dose reaches the lungs within which timeframe.

Do you have any advice you would like to pass on to your colleagues working in outpatient settings?

In the less severe cases of COVID-19 or for virus infections in general, to clarify the diagnosis and coordinate the therapy, a partnership with an experienced clinician who is willing to provide information is certainly advantageous. Severe cases should only be admitted to hospitals that already have the appropriate experience.

Colleagues working in an outpatient setting should be involved in the follow-up and encourage patients take care of themselves for 4-6 weeks after the infection and continue to take prophylactic heparin, as there is the risk of late onset thrombosis and pulmonary embolism. Otherwise, I can only advise that my colleagues look after themselves to ensure they do not catch COVID-19.

Dr Voshaar, thank you very much for the interview.

NOTE: The interview with Dr. Voshaar was conducted on July 28, 2020. The statements were made on the basis of the information available at that time.

The interview in full length

Federal Health Minister Jens Spahn and Minister President of North Rhine-Westphalia Armin Laschet visited the Bethanien Hospital in Moers and the aerosol expert Dr. Thomas Voshaar to praise and acknowledge his concept for the treatment of Covid-19 patients*. We were able to talk to chief physician Dr. Thomas Voshaar in advance about his therapy concept for Covid-19 patients. Watch the video in full length here. 

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