Using high flow nasal cannulas to reduce mortality rates during COVID-19 04 May

The COVID-19 pandemic has just completed its second anniversary in 2022. With new viral mutations coming out nearly every few months, COVID-19 has essentially forced people to “live with it”. However, this has also put a significant strain on healthcare systems worldwide.

Overwhelmed healthcare facilities

As the infection spreads quickly amongst the population, critically ill patients are referred to hospitals in the hundreds, overwhelming available facilities and making it difficult to ensure quality care. Patients suffering from end-stage or advanced stages of coronavirus disease often need respiratory support due to the nature of the disease. In extreme cases, it requires ventilators to help them breathe.

This need for ventilators caused governments and hospitals to acquire and stockpile as many ventilators as possible, creating a worldwide shortage of ventilators against extremely high demand. Automobile companies and other manufacturers such as Ford and GM quickly adapted their production lines to produce thousands of ventilators each year on a war footing to meet this sudden demand.

Are ventilators causing higher mortality rates in COVID-19 patients?

Most patients with COVID-associated respiratory failure or respiratory distress require supplemental oxygen therapy. This is either provided through high-flow oxygen therapy or mechanical ventilation. Patients who cannot breathe independently require immediate invasive interventions such as ventilators.

However, during the first and second phases of the coronavirus outbreak, doctors would put hypoxic patients on ventilators early as the disease progressed very rapidly and dropped their saturation rates from 70-80% to nearly 40-50%.

Using HFNCs to reduce mortality rates

A study published in the Annals of the American Thoracic Society noted that early invasive mechanical ventilation caused higher-than-normal mortality rates and reduced the availability of ventilators for those who urgently needed them to survive.

The study also noted that using HFNC or high-flow nasal cannulas for those with respiratory distress delayed or eliminated the need to be intubated and put on mechanical ventilation. This meant that using HFNCs instead of invasive mechanical ventilation would cause fewer deaths than trying to put every patient with respiratory distress on invasive ventilation. Additionally, HFNCs also freed up ventilators, reducing the overall demand and the number of days without available ventilators by up to 11.8%.

To put this in numbers, a 250-bed hospital with 100 mechanical ventilators would see 130 fewer deaths if they had 33 high-flow nasal cannulas. Applying this strategy nationwide in the US resulted in 10,000–40,000 fewer deaths than if high-flow nasal cannula were not available. Additionally, this meant that hospitals could reserve ventilators for those patients where HFNC would be insufficient to avert death.

What is HFNC? How is it different from a ventilator?

High-flow oxygen therapy requires an HFNC or a high-flow nasal cannula to deliver oxygen to patients suffering from respiratory distress. High-flow oxygen therapy exceeds the standard human inspiratory flow rate (20-30 litres per minute) and can provide anywhere between 2-120 litres of oxygen per minute. A high-flow oxygen therapy setup includes:

  • Flow generator
  • Air-oxygen blender
  • Humidifier
  • Heated tube
  • Delivery device (HFNC)

As the flow rate of oxygen in HFNCs can be set accurately by medical professionals, the FiO2 or fraction of inspired oxygen can be nearly 90-100%, which is close to invasive mechanical ventilation.

Ventilators are an invasive, extensive apparatus that have all the components of an HFNC and include monitoring and control systems to ensure safe and controlled ventilation for patients. However, mechanical ventilation is invasive, and intubation can cause injury to the patient’s lungs, trachea or throat and, in extreme cases, cause fluid build-up, aspiration or other respiratory complications.

Why is high-flow oxygen therapy better than mechanical ventilation and non-invasive ventilation?

Mechanical ventilation, or the usage of ventilators requires patients to be sedated and intubated while on ventilators. Sedatives used for this purpose have severe and lasting side effects. Additionally, errors in ventilator calibration can cause weakness of the diaphragm, overinflation of the lungs and lead to ventilator-associated acute lung injury.

Non-invasive ventilators do not have the side effects of intubation. However, non-invasive ventilation requires a sealed face mask, nasal mask, mouthpiece or helmet for oxygenation. This can cause anxiety, claustrophobia, agitation, abdominal distention due to air swallowing, raised ICP and impaired nutrition. Additionally, both mechanical invasive ventilators and non-invasive ventilators require constant medical supervision.

HFNCs do not suffer from any of these side effects and can easily be used for patients that are not critically ill or are awaiting a ventilator. Delivering warmed, humid air on high flow to patients with mild respiratory distress, HFNCs can help patients breathe better comfortably, without the side effects of mechanical or non-invasive ventilation.

Final thoughts

Although mechanical ventilation remains the mainstay of treatment for critically ill patients suffering from acute respiratory failure, non-invasive therapies such as high flow oxygen therapy can help those with mild respiratory distress breathe better and even avoid mechanical ventilation. Using HFNCs helps healthcare facilities reduce ventilator shortages and provide better care to COVID-19 patients, helping them get out of the hospital faster.