In the early stages of the coronavirus pandemic, ventilators – or the sparsity thereof – caused a great deal of distress to healthcare professionals, politicians, and the British people. The bulk acquisition of these devices became a priority for the floundering government, wanting to reassure its citizens that they would have access to this seemingly life-saving technology should they need it. Indeed, news reports often showed ICUs packed with intubated patients being kept alive by the rhythmic propulsion of air into their lungs, which had failed to function unassisted. It seemed as though the number of ventilators per capita was an important predictor of a nation’s ability to tackle this crisis. But then, it all changed.
NHS reports soon showed that ventilated patients were unusually likely to die, with two-thirds of them not making it out of the ICU alive. Recently, doctors have refrained from using these machines, noting better patient outcomes. Ventilators aren’t entirely useless for the treatment of coronavirus-induced respiratory distress, but they offer diminishing returns as they don’t address the other important factor that determines pulmonary gas exchange: blood flow.
Keeping appropriate levels of oxygen in the blood – a big issue for acutely-ill COVID-19 patients – involves the close matching of ventilation (air flow) to perfusion (blood flow) in the individual air sacs of the lungs, the alveoli. From the beginning of this crisis, a huge focus was placed on ventilating patients who were struggling to breathe by themselves. Mechanical ventilators appeared to be absolutely essential in treating end-stage COVID-19 patients on ICUs. Whilst the ventilatory aspect was overwhelmingly addressed, perfusion of the lungs was mostly ignored. There is little benefit in ventilating a lung that is not well perfused – extra oxygen cannot be ‘picked up’ by the blood and carried to the rest of the body. Consider a train (the blood) coming into a station (the lung; or more specifically, one of its many alveoli): cramming the station’s platform with passengers (oxygen) is no good if the train is unable to reach the platform due to broken tracks.
In fact, autopsies have shown COVID-19 lungs to be full of clots (broken tracks), occluding alveolar blood flow and making the extra ventilation somewhat useless. These are presumably caused by inflammation of blood vessels and enhanced clotting pathways. Recent findings indicate that micro-clots are nine times as prevalent in COVID-19 lungs as in those of patients who succumbed to the flu. Pathologists in Italy started properly discovering these blockages around mid-March, by which point the disease had already ravaged through the country; only ten days earlier, ethical guidelines given to Italian doctors stated it may be necessary to withdraw care from critical patients, prioritising those with a better chance of survival. Considering the virus was so new and misunderstood, it seems surprising that post-mortem studies weren’t carried out sooner.
Naturally, anti-clotting drugs – anticoagulants – were suggested as a potential treatment for those affected by the disease. However, the medical community took too long to evaluate the efficacy of this intervention. There are, finally, ongoing trials aiming to assess just how beneficial this treatment could be. These show mixed results, but the consensus is that a higher level of anticoagulation is probably required for COVID-19 patients, compared to the standard dose that is traditionally administered on the ICU. A lot of these studies focus on advanced cases, where it is potentially too late as clots have already formed. At the end of April, the NHS commissioned a group of experts to provide clinical guidance on the use of anticoagulants in COVID-19 patients. The NHS is yet to release this guidance to its clinicians.
Although the effect of the novel coronavirus on the body is highly complex and multi-faceted, the initial rush to ventilate deteriorating patients may well have overshadowed other important aspects of the virus’ attack mechanism. How many more lives could have been saved without the blind focus on ventilators?
Image attribution: https://pixabay.com/photos/hospital-bed-doctor-surgery-1802679/