What happened to all the ventilators? : COVID19 Demystified

This article was reviewed by Dr. Phil Lange, one of our subject matter experts.

This research was conducted by scientists at the University of Washington, the Virginia Mason Medical Center, and the Swedish Medical Center (all in Seattle, WA).

The paper we will be demystifying today can be found here, if you’d like to follow along.

TL;DR

Researchers followed 24 patients in ICU care in Seattle that were diagnosed with COVID-19. Most patients had symptoms for a week before arriving at the hospital. Once they arrived, most of them had a cough but only half had a fever. 18 patients were put on invasive mechanical ventilators and by the end of the study, only 6 had been taken off their ventilators. Of the 24 patients, 12 died, 5 were discharged from the hospital, 4 were moved from the ICU to another part of the hospital and 3 continued to receive ventilation in the ICU. The earliest a patient was taken off a ventilator was 8 days. These symptoms and numbers are similar to those reported by China.

Introduction

By now you’ve hopefully picked up on the clue that this website focuses solely on SARS-CoV-2 and Covid-19. Well, surprise surprise, so is this article! In this study, researchers looked at critically ill patients with Covid-19 in Seattle to report their characteristics and outcomes. This is a more epidemiology focused study in contrast to the recent biological science studies we’ve been focusing on. Epidemiology is a branch of science that looks at patterns and determinants of health and disease.

Methods

To conduct this study, researchers included data from 24 adults (18+) who were admitted to ICUs (Intensive Care Unit) in 9 hospitals in the Seattle metropolitan area between February 24th and March 9th. All participants were confirmed to have Covid-19 through a positive RT-PCR assay (for more information about what this acronym means read here!). Pregnant women, prisoners and children were not included in this study.

Results

Demographic and clinical characteristics of the patients

Average age of patients: 64 (from 23 to 97)
63% of patients were men
Average duration of symptoms before hospital admission: 7±4 (this means that 95% of patients had symptoms for about 3 to 11 days before being admitted to the hospital)
None of the patients had recently travelled to China, South Korea, Iran or Italy
16 (67%) patients were admitted from home and 6 (25%) were from a skilled nursing facility
The most common symptoms when patients arrived at the hospital were: shortness of breath and cough
12 (50%) patients had a fever when they arrived at the hospital
14 (58%) patients had diabetes
5 (21%) patients had chronic kidney disease
3 (14%) patients had asthma
5 (22%) patients were current or former smokers
8 (33%) patients had more than one condition

Laboratory and radiologic findings

75% of patients had low levels of lymphocytes in their blood (read about what lymphocytes are here)
23 patients had chest radiographs and all showed bilateral pulmonary opacities (this happens when the ratio between gas to soft tissue decreases)

Microbiologic results

Researchers also tested 23 patients’ samples for other respiratory viruses; none of the patients were infected with another virus on top of SARS-CoV-2
To double-check, researchers also tried culturing (growing) bacteria from 15 patients, all were negative
To TRIPLE check, researchers also tested the blood samples from 20 patients, still, all were negative for other viruses

Respiratory failure and shock

18 (75%) patients were put on invasive mechanical ventilation (this is the machine you might have seen on shows like Grey’s Anatomy where patients are hooked up to a machine to help them breathe. Invasive means that the tube is put down their breathing tube, which is called the trachea)
For these patients, their oxygen ratios indicated moderate-to-severe Acute Respiratory Distress Syndrome (ARDS). ARDS is when you suddenly (acutely) have an onset of hypoxemia (low oxygen level in blood)

Outcomes

By the end of the testing period (March 23^rd, 2020), 12 (50%) patients had died, 4 (17%) patients were moved from the ICU to another part of the hospital, 3 (13%) were still in the ICU receiving mechanical ventilation and 5 (21%) had been discharged.
62% of patients over the age of 65 died
37% of patients under the age of 65 died
The median length of stay in the hospital for survivors was 17 days, 14 days in the ICU
The median duration that patients were put on mechanical ventilation was 10 days
6 patients were taken off mechanical ventilation by March 23^rd
Take a look at figure 2 of the article on page to see detailed outcomes of patients 1 to 24!

Discussion

The biggest takeaway from this study was that overall, outcomes for all patients that received ICU care were poor. The patients included in this study all had respiratory symptoms that were similar to those reported in China, including the average duration of time patients presented symptoms before being admitted to the ICU (7 days). Although most of the patients had a cough when they arrived at the hospital, only half had a fever. Therefore, the researchers suggest that waiting around for fever may delay the whole diagnosis process.

The case fatality in this study was 50% since of the 24 patients, 12 died. Indeed, this number is also similar to numbers from Chinese hospitals. Although most of the deaths occurred in older people (65+), 37% of deaths still occurred in patients that were considered quite young.

The earliest a patient was taken off mechanical ventilation, of the 6 that were taken off, was 8 days. This is important because it suggests that if someone is put on a ventilator due to Covid-19, it may be days or even weeks until they are extubated.

Three of the patients who had mild asthma had received systemic glucocorticoids for their asthma, 1 week before being admitted to the ICU. All 3 of these patients we put on invasive mechanical ventilation. This is interesting because previous studies indicate that when patients who are on glucocorticoid treatment are infected with viruses similar to SARS-CoV-19 (like SARS-CoV and MERS), they had higher levels of virus in their blood, were sick for longer and had worse outcomes.

Limitations

The first limitation of this study is that not all patients underwent all the same clinical tests. For example, only 15 patients’ samples were sent for bacterial culture.
This study stopped on March 23^rd, 2020, however, some patients were still in the hospital at this time and their final outcomes weren’t included in this study. This means that some of the numbers in this study could be overestimating or underestimates.
This study only included 24 patients. As said in our previous demystified articles, it is difficult to look at a small sample size and determine if the findings can be generalized across the population to all critically ill patients.
Finally, this study only took into consideration critically ill patients who were admitted to the ICU. For all we and the researchers know, there could have been equally critically ill patients who chose not to go into the ICU and instead chose palliative care.

Overall, this study highlights lots of important things: although age may be a trend we’re seeing in this pandemic, there are still significant numbers of younger people who are being admitted to the ICU and dying (37%), however these numbers must be read in the context that the majority of patients included in this study had underlying conditions such as diabetes. Also, the researchers suggest that fever may not be the best indicator for Covid-19 since only half of the patients included in this study had one when they arrived at the hospital to be admitted. Also, it shows why the demand for ventilators got to where it is. If you can imagine most patients admitted the ICU being on a ventilator for 8+ days each, you can see why hospitals quickly started to run out. As this pandemic roars on, these data are important to keep in mind to better prepare and meet the needs of the healthcare system!