Welcome to the Plague Pit – issue number 13

A few weeks ago, I said I’d write about what happens to seriously ill COVID-19 patients. These are the ones with lungs so badly affected by the disease that they require help from a mechanical ventilator to get the oxygen they need to survive.

The way that oxygen normally gets into the body, and what happens to it when it gets there, is the domain of physiologists.

It all starts with physiology

Physiology, or how the body works, is a major subject for students studying for the basic medical degree – the MB BS. Even after doctors qualify, physiology is so important that many of us are tested again and again on it as we specialize. The FRCA, MRCP and FRCS examination curricula (respectively for anaesthetists, physicians and surgeons) all include large sections on the subject.

The Physiological Society is the professional organization for experimental physiologists, founded nearly 150 years ago. Charles Darwin was one of their first Honorary Members. Several Members since then have won Nobel Prizes, some of them for experimental work involving oxygen.

The Society’s website currently has a ‘COVID-19 Hub’, featuring an expert panel of scientists and clinicians who are tackling questions submitted online by others on the frontline. The Society also have a podcast about the disease, one in an excellent regular series (https://www.physoc.org/explore-physiology/podcast/).

Even without COVID-19, anaesthetists like me need to know physiology better than most because we manipulate it, second by second, during every surgical anaesthetic we give. Senior anaesthetists often examine trainee surgeons on physiology in their oral examinations, held at the Royal College of Surgeons.

We also have to teach it. So here goes…..

Let the machine do the work

Breathing – or inspiration, at least – means work. Breathing with COVID-19 is especially hard work.

The diaphragm is the muscle – domed at rest – that internally separates the chest cavity from the abdominal one. Inspiration happens when the diaphragm contracts and flattens. This means that the pressure inside the chest falls below atmospheric pressure. If the tubes between lungs and the outside (the ‘airway’) are clear, air is drawn down the pressure gradient into the alveoli. These are the air sacs in the lungs, whence oxygen passes into the blood.

85% of the work of inspiration is done by the diaphragm – the rest, by intercostal muscles that draw the ribcage up and out. The energy spent in breathing equals the respiratory rate multiplied by the work required for each breath. Deep breaths require more work than shallow ones. And for a breath of given volume, the work is increased by conditions that:

(1) obstruct the flow of air

(2) make the lungs stiff

(3) interfere with the movement of the ribs and diaphragm

COVID-19 patients have a lot of things going on. The virus causes a rise in temperature. Metabolic reactions in the body’s cells speed up accordingly, releasing more carbon dioxide into the blood (‘hypercarbia’). Both fever and hypercarbia cause a reflex increase in breathing rate and volume i.e. more work.

The lung infection may result in low blood oxygen concentrations (‘hypoxia’), as discussed in an earlier issue. Hypoxia also causes a reflex rise in breathing rate and volume. And lungs stiff with viral damage are harder to move – more work, again. Add in smoking and obesity – both conditions which can increase respiratory effort and impede oxygenation –  and you can see why patients with these risk factors are well represented among COVID-19 patients on ICU.

Even if the question of limited resources is left aside, the decision to intubate the trachea and mechanically ventilate a COVID-19 patient is not taken lightly. According to national data, 50% of such patients will die. While this figure reflects the disease, not the ventilation, doctors have naturally attempted other established treatments for respiratory failure. These include Continuous Positive Airway Pressure (CPAP) facemasks.

https://en.wikipedia.org/wiki/Continuous_positive_airway_pressure

These tight-fitting masks enable us to administer oxygen continuously to a patient’s mouth and/or nose, using special machines to control the pressure carefully. The technique helps to relieve the patient of some of the effort of inspiration, and to prevent collapse of alveoli that might otherwise occur during expiration. Its use in COVID-19 patients seems to be of limited help, however, and it carries the risk of spraying infected droplets over staff and other patients nearby. Intubation and ventilation is the only effective alternative – and first choice for most.

This week, I spoke to one of the TUBE team, the anaesthetists responsible for emergency intubation of COVID-19 patients. The reasons for intubation and ventilation are the same as they are in other patients: hypoxia, hypercarbia, exhaustion, cardiac arrest – or a combination of the above. Except for those on the point of death, patients require an anaesthetic for intubation. And though some patients are confused and delirious by this stage, many are still fully conscious at the time they are assessed.

This has personal consequences that are sometimes hard to bear. We are aware that half these patients will not survive. It is likely that even with the most skilful use of sedative drugs on ICU, the most seriously ill may not be able to communicate effectively with anyone after intubation and before they pass away.

Many of the critical COVID-19 patients in urgent need of ventilation in my hospital have their closest family members overseas. It is impossible to describe the emotional impact on participants –  and to a much, much lesser extent, on bystanders – of a mobile phone conversation between patient and overseas spouse, immediately before emergency intubation of uncertain outcome.          

Clothes maketh the man

The newspapers are full of images of healthcare staff in full gowns with long sleeves to prevent them acquiring COVID-19 from infected patients. Their attire contrasts sharply with workwear before the epidemic.

The ‘bare below the elbows’ policy (BBE) was adopted a few years ago by some UK hospitals and is ostensibly a measure to reduce infection transmission. BBE requires staff in clinical areas to expose their bare forearms and remove wristwatches. For male doctors, BBE is often combined a ‘no ties’ rule. Bowties are usually permitted.

There has never been any convincing study to show that BBE reduces hospital-acquired infection rates.[1] This being the case, its imposition a few years ago on a generation of doctors reared on ‘evidence-based medicine’ was unpopular. The implementation of BBE in many institutions –  and its zealous enforcement by non-medical staff, who were encouraged to challenge offending doctors – generated considerable resentment.

This may explain why the (normally courteous) surgeon in the video below is so angry about BBE – and furious about Prime Minister David Cameron’s unnecessary and potentially infectious visit to his patients. One measure commonly used to compare the performance of orthopaedic surgeons is the proportion of the joints they replace that become infected – a disastrous complication.

(https://www.youtube.com/watch?v=WIQWaBbURlY)

BBE eventually gained acceptance in my own Trust after a senior consultant microbiologist toured hospital departments, one by one. In a series of refreshing doctor-to-doctor meetings, he openly conceded the lack of evidence for BBE per se. He convinced us that its strength lay not in its clinical, but its symbolic impact. Combined with genuinely effective measures – like doctors washing their hands more – he argued successfully that BBE was a highly visible public indicator of our desire to reduce hospital-acquired infections.

Personal grooming

It’s hard for doctors to keep up personal appearances in a lockdown.

As hairdressers isolate, many of my elegant middle-aged colleagues – male and female – are showing their roots for the first time. Younger consultants have been obliged to adopt the ‘haystack’ style. Patients struggling for breath with extreme COVID-related hypoxia may have other priorities.

Nevertheless, how doctors look has often been the subject of academic interest –  because patients feel strongly about it. [3] A notorious paper about preoperative visits by anaesthetists, published soon after I became one, put short hair high among the attributes patients find desirable. [3]

Medical schools have long sought to curb the tonsorial excesses of students, though there have always been rebels. Below is a partial transcript of my interview with an eminent retired doctor a few years ago. He’s describing a Council meeting at St Bartholomew’s Medical School in 1970, which he attended as a Reader in Surgery (a post with teaching responsibilities):

“One day in the School Council they were complaining about students with long hair down to here you see. And they said,

‘The patients don’t like it you know.’

So I … I mean, you weren’t really supposed to talk until you were about 45 as a consultant there, I was only about 33 or so. Anyway, I said,

‘Well, have you asked the patients?’

‘No, of course not.’

‘Well, I have, I’ve asked 56 and they all said the same thing; they didn’t care how long it was, as long as it was clean and so long as they’re nice to us.’

Well, they didn’t like that. And then I said,

‘Oh, by the way, could I just point out… ‘ <interviewee chuckles>

There was a portrait on the wall of Lord Lister….”

Joseph Lister, surgeon. Could do with a trim?

Shave and a haircut

In the COVID-19 emergency, there have been some creative ideas from medical staff needing a haircut. Suggestions in one Twitterfeed include a role for surgeons proficient in robot-assisted surgical techniques (RAS). (https://en.wikipedia.org/wiki/Robot-assisted_surgery).

Robots are used in some laparascopic procedures, notably prostatectomy. The machines are very expensive and the advantages claimed over traditional open surgery are disputed. Best evidence suggests these may be limited to shorter hospital stay and fewer blood transfusions. [4]

Typically RAS surgeons control the instruments inside the patient’s abdomen from a booth in the same operating theatre. Some, however, have used RAS to operate on patients from hundreds of miles away. [5] It shouldn’t be too tricky, then, for socially-distancing surgeons with robotic scissors to sort out a ‘do’ for a customer two metres away.

They’re not as busy as they were before COVID-19 – and they were originally barber surgeons, after all. https://en.wikipedia.org/wiki/Barber_surgeon).

Less fancifully, enterprising Casualty doctors in my own institution have set up shop. There are lots of electric hair clippers in Casualty for preparation of the skin around scalp wounds that need stitching. Occasionally, the clippers have a bigger job to do

Patients with a head injury are sometimes unconscious because they have bled into or around the brain. This blood (an ‘intracranial haemotoma’) can cause a rise in pressure, damaging uninjured parts of the brain. The pressure can sometimes be relieved, and the secondary damage prevented, with a craniotomy. In this emergency operation, neurosurgeons cut a flap into the skull, elevate it and remove the haematoma. Preparation for the skin incision includes a partial or complete head-shave.

One sign of rising intracranial pressure after head injury is seen in the eye – namely widening of one pupil or ‘unilateral pupillary dilatation’. It’s thought to be due to compression of one of the nerves to the eye, as it travels inside the skull. Its significance has been appreciated for centuries. The story is told in a paper in the journal Medical History, with some appropriately gruesome drawings of early neurosurgical techniques. [6]

Some people are unfortunate to be born with unilateral pupillary dilatation, despite having a normal brain. There is an apocryphal story about a neurosurgeon with this condition. He was concerned that he might somehow become unconscious for non-traumatic reasons, and receive an unnecessary craniotomy from overzealous colleagues.

He is said to have had his head shaved and a tattoo applied above the hairline. This would become invisible once the hair grew back, and remain so unless he was shaved for emergency craniotomy. The tattoo read:

‘Check the brain scan. I have a congenitally dilated right pupil’

Casualty Department staff at my hospital are filling quiet moments by offering appointments to shear desperate colleagues in a vacant plaster room. Donations from grateful customers go to domestic violence charities and amount to more than £2000 so far. Let’s hope no-one goes for anything too exotic.

The Good Soldier

[1] Godbout EJ. Bare below the elbows in an academic medical center. Am J Infect Control. 2019 Aug;47(8):1030-1031.

[2] Petrilli CM et al. Understanding patient preference for physician attire: a cross-sectional observational study of 10 academic medical centres in the US. BMJ Open 2018;8:e021239. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5988098/

[3] Sanders LD et al. The impact of the appearance of the anaesthetist on the patient’s perception of the pre-operative visit. Anaesthesia 1991;46:1056-8. https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2044.1991.tb09923.x

[4] https://www.cochrane.org/CD009625/PROSTATE_laparoscopic-and-robotic-assisted-versus-open-radical-prostatectomy-treatment-localised-prostate

[5] https://www.bbc.com/future/article/20140516-i-operate-on-people-400km-away

[6] Flamm ES. The dilated pupil and head trauma 1517-1867. Med Hist 1972;16(2):194-9. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1034966/