In the face of the COVID-19 pandemic, in addition to lockdowns, curfews and economic upheaval, most planning centres and living rooms have been debating the shortage of ventilators and the need for critical care in the days to come.
We have seen heartbreaking scenes from Italy, Iran and New York, where many lives have been lost, hospitals are full and ventilators are in short supply. It is important to delve on these issues and develop rational approaches and solutions, in the Indian context, to an impending surge of critically ill patients.
The modern ventilator is an advanced medical device that performs the complex task of allowing a patient to survive respiratory illnesses in various settings. To ICU specialists, also known as intensivists, the ventilator is a powerful ally when managing patients who need critical care.
That said, intensivists understand more than anyone else that the ventilator can be a double edged sword as well. Its principal function is to sustain breathing for a critically ill patient until the underlying disease process improves (either spontaneously or with treatment). The ventilator is not a cure or a treatment by itself. It simply buys time for some treatment to work or for the body’s healing mechanisms to have a chance to act. In cases of severe illness, the machine may have to deliver a concentrated amount of oxygen (up to 100% O2) in contrast to 21% oxygen present in ambient air.
When we breathe in, we create a negative pressure in our chest cavity using the muscles in our chest wall and the diaphragm to suck air into the lungs. This is known as negative pressure ventilation. A ventilator on the other hand pushes air into the lungs and creates a positive pressure ventilation (PPV) system. A patient on a ventilator typically has a plastic breathing tube inserted into their mouth or airway to allow this to happen, rendering it an invasive therapy.
A COVID-19 related lung injury is typically classified as an acute respiratory distress syndrome (ARDS). The lung’s lining that participates in gas exchange is adversely affected in this disease. Contrast this with, say, polio, where the lung is often essentially normal but the muscles that support breathing are weak. In muscular disorders, simple ventilators – even those not using supplemental oxygen – would suffice. But with ARDS, where the lung lining is damaged, a patient will need supplemental oxygen in addition to mechanical ventilation.
Severely ill COVID-19 patients will need ventilators, and India will need to increase its ventilator capacity. Data from around the world suggests that a high percentage of these patients will unfortunately succumb to their illness. When mobilising resources such as equipment and personnel, the government would be prudent to consider easier strategies – ones that might allow doctors to save potentially hundreds of patients who don’t meet the evidence-based threshold for ventilator use.
One option is to produce high-flow devices en masse and ensure sufficient oxygen supply.
First, do no harm
While ventilators offer clear benefits, PPV is known to cause adverse effects in experimental and clinical models. It causes ventilator-induced lung injury (VILI) – a condition that doctors have known of for decades. Intensivists spend years in training to learn and understand various modalities that minimise VILI and optimise the chance of lung recovery. In ARDS, which afflicts a majority of the critically ill COVID-19 patients, the lungs are stiff and susceptible to injury from excessive pressure generated by ventilators.
The primary goals of mechanical ventilation are safety, comfort and eventual liberation from the device. Given these objectives, when low-cost ventilators with short development cycles reach the market, doctors are obviously going to be concerned. It is relatively easy to pressurise a breathing circuit but it takes years to perfect the safety and comfort systems that optimise patient outcomes. Similar concerns exist with using devices called splitters, which allow more than one patient to be ventilated by the same device. The skills needed to administer advanced mechanical ventilation are also in short supply. So when untrained workers use untested devices, especially in experimental ways, the risks to patients could be significant.
Once you combine this with the fact that COVID-19 patients who require mechanical ventilation are already at high risk of dying, the likeliest conclusion is that these patients must be put on a validated and reliable ventilator and treated by trained personnel, to the extent possible, to maximise their chances of recovery.
Ventilators also need significant clinical effort by a nursing team to reduce the chances of causing harm. Ventilator-associated pneumonia (VAP) is a common complication that occurs in about 30% of mechanically ventilated patients. The incidence of VAP is reduced by high-quality nursing care and strict protocols.
This expertise is not easy to impart to the vast majority of understaffed and under-skilled ICUs in India. It would be unfortunate for a large number of patients to be put on ventilators only for abnormally large numbers of them to succumb to VAP later. This story is not uncommon in India.
In ideal situations, with unlimited ventilators and skilled hands, there is no doubt that early invasive mechanical ventilation with high concentrations of oxygen and application of advanced techniques of ARDS care is the way to go.
In the absence of this, the other option often used is non-invasive ventilation (NIV), achieved by using a mask to deliver air under pressure. While NIV is easier to use compared to ventilators, there is still a chance of harm to the patient. It is also not easy to use with reduced or unskilled personnel. Records suggest NIV may not be very useful when used to treat COVID-19 patients with lung injury. Face masks are simple and commonplace but are not capable of delivering high flows or a therapeutic range of pressures to help patients with breathing.
Another way to deliver oxygen to critically ill patients, prior to them requiring invasive procedures, is via high-flow nasal cannulas (HFNCs). HFNCs require large amounts of oxygen to be available. So if oxygen supply can be maintained, HFNCs are easier, cheaper to deploy and place on patients, and have been recommended for use in COVID-19 patients with low oxygen levels as well.
Invasive ventilation with a mechanical ventilator
High-flow nasal cannula
Putting it all together
When dealing with respiratory failure due to hypoxemia (low oxygen level in the blood) at a pandemic scale, there are four ways to deliver respiratory assistance (see table below). We have made a few assumptions in our analysis here. First, we decided to be patient-centric with respect to risks and benefits. Second, we assumed that the treatment option should be easy to mass-produce or source and that oxygen is plentiful. Third, we keep in mind the heterogeneous levels of skill in India. For example, untrained staff with a complex device are likely to either use it ineffectively or, worse, cause inadvertent harm.
Most COVID-19 patients admitted to hospitals have mild to moderate ARDS. HFNCs have the potential to treat most of them with an evidence-based level of respiratory support. In an imperfect world, this may well be a suitable solution for India. HFNCs are more comfortable to wear for patients, offer more benefits than a simple mask and have significantly lower risk compared to NIVs or invasive ventilation. At least one study has shown that it may even reduce the risk of mechanical ventilation altogether. These benefits cannot be ignored in India.
Areas where COVID-19 patients are treated need to be well ventilated so that infectious aerosols are removed from the air. This is usually accomplished by artificial indoor ventilation that can clear a room’s entire volume at least 12 times per hour – the minimum requirement per WHO guidelines.
However, and quite alarmingly, most Indian ICUs only have a standard split air conditioner that does not have high-efficiency particulate air filters. This is a disease transmission catastrophe waiting to happen.
The process of putting a patient on a ventilator generates infectious aerosols as does using NIV and HFNCs. India may not have enough personal protective equipment (PPE) for its medical workers either. A PPE shortage plus recirculated air would subject these workers to extraordinarily high amounts of aerosols, increasing their chances of infection. This is an under-recognised risk and compromises our finite healthcare resource.
The amount of aerosol generated from HFNCs is low and not likely to be harmful if ventilation is adequate and protective measures are taken. Measures such as putting a surgical mask on the HFNC while in use and making sure healthcare providers wear proper PPE should help as well. Negative pressure rooms that prevent aerosol dispersion are strongly recommended but a pipe dream in India for now. Interestingly, WHO has indicated that in the right settings, natural ventilation can have air exchange rates that meet or exceed the standards set for indoor air quality.
Using natural ventilation in COVID-19 treatment units is pragmatic and safe when negative pressure rooms or artificial ventilation is not feasible. Given our temperate climate, India is in a unique position to leverage this.
Reading these facts in the context of Indian healthcare, the combination of HFNCs and naturally ventilated ‘open-air’ ICUs seems quite pragmatic. It maximises benefit to salvageable patients and optimises the safety of healthcare workers.
We should redouble our efforts to manufacture reliable ventilators and upgrade our facilities over the next few months. We laud the ingenuity and industriousness of our engineers and the endeavours of government and private enterprises in trying to make this happen. Our premier hospitals, with well-qualified doctors, can treat patients as well and as safely as anywhere in the world. However, based on predictions of how the virus will spread through India, hospitals and their personnel will exhaust their capacity. Even if India manages to get more ventilators, it is unlikely that we will have enough trained personnel and facilities to use them properly. We need simultaneous focus on more easily deployable and safe resolutions that address the need of the hour.
Dhruv Joshi and Dileep Raman are pulmonary and critical care specialists who trained in the US and now live in Bengaluru. They run a company that delivers critical care services remotely.