A new device can deliver oxygen directly to the bloodstream intravenously


A team of researchers from Harvard Medical School and Boston Children’s Hospital has developed a device to help patients experiencing refractory hypoxemia. In their paper published in Proceedings of the National Academy of Sciences, the group describes their new device and how well it worked when tested on human blood and blood inside of live rats.

Refractory hypoxemia is a condition sometimes experienced by patients on ventilators – it is generally due to acute respiratory distress syndrome.

Less oxygen makes the trip from the lungs into the bloodstream, leading to organ damage and sometimes death. Current treatment often involves the use of an extracorporeal membrane oxygenation (ECMO) machine.

Our group has developed and tested three major generations of oxygen-filled microparticles, each with defined benefits and drawbacks as an injectable oxygen carrier. DSPC = 1,2-distearoyl-sn-glycero-3-phosphocholine; PLGA = poly(lactic-coglycolic acid); DASh = dextran acetate succinate (with a high degree of substitution); ACA = asphyxial cardiac arrest; DO2 = oxygen delivery.

It extracts most of a patient’s blood, removes carbon dioxide, adds oxygen and then pumps it back into the patient. Because ventilators can damage lungs, and because access to ECMO machines is limited (and risk of infection is high), the researchers developed a new machine that can add oxygen directly to blood while it is still inside the patient.

The new machine works by first infusing oxygen into a liquid solution. That solution travels through a series of ever-smaller nozzles, reducing the size of the bubbles down to micron scale.

The bubbles, the researchers note, are smaller than red blood cells. Next, the bubbles get a coating of a lipid membrane that is similar to some types of natural cell membranes.

This prevents toxicity and also keeps the bubbles from sticking together. The resulting solution is then injected directly into a patient’s bloodstream. Once inside, the lipids dissolve, releasing the oxygen into the bloodstream. They are tiny enough that they will not block any blood vessels.

The researchers tested their machine on human donor blood and in rats and found it passed as a proof of concept. In human blood, their machine could increase blood oxygen saturation from 15% to over 95% within seconds to minutes. And they increased saturation from 20% to 50% inside of rats.

They acknowledge that it is not yet ready for testing in humans. They plan to continue with tests on larger animals before testing on humans.

The role of extracorporeal membrane oxygenation (ECMO) support for patients with cardiopulmonary failure due to coronavirus disease 2019 (COVID-19) is evolving. A prominent feature of COVID-19 in critically ill patients is acute respiratory distress syndrome (ARDS). Early in the pandemic, data on ECMO use was limited, and guidance was offered based on best practices at the time.1–4 Very limited case series available at the onset of the pandemic seemed to indicate poor survival for patients with ARDS placed on ECMO.5 However, the role of ECMO for COVID-19–related ARDS and other indications has become more apparent as the pandemic unfolds and evidence is generated.

A multicenter French study of 83 patients with COVID-19–related ARDS managed with ECMO revealed an estimated 60 day mortality of 31%.6 Subsequently, data from the Extracorporeal Life Support Organization (ELSO) Registry reported an estimated cumulative incidence of in-hospital mortality 90 days after ECMO initiation of 37.4%. This report included 1,035 patients with COVID-19 who received ECMO in 36 countries.7 An additional observational study reported 45% mortality for 1,531 patients from 177 centers in Europe and Israel.8

According to prepandemic historical data from the ELSO registry, venovenous (V-V) ECMO results in an approximate mortality of 40%, venoarterial (V-A) 55%, and extracorporeal cardiopulmonary resuscitation (ECPR) 71%. Mean V-V run duration is generally longer (12 days) than V-A (7 days).9 For patients with COVID-19, mortality is similar to historical V-V ECMO mortality; however, mortality is still being determined with ongoing data collection and may be increasing.10 Median (14 days7 and 20 days6) and mean (18 days8) run duration appears to be longer.

In the great majority (>90%) of reported cases, V-V ECMO was utilized for COVID-19.6–8 Some patients with COVID-19 develop myocarditis, massive pulmonary embolism, stress cardiomyopathy, arrhythmias, and acute coronary syndrome,11–13 which may require mechanical circulatory support such as V-A ECMO. Data on V-A ECMO for COVID-19 are limited in the ELSO Registry study and may be found in small case series, making the utility of V-A ECMO for COVID-19–related cardiogenic shock less clear.6–8,14 As a general guide to practice, we recommend the use of ECMO for patients with COVID-19 and severe cardiopulmonary failure who meet traditional criteria and when appropriate resources are available.15

Given the paucity of available data when prior ECMO guidelines were published,1,4 this guideline has been created to summarize currently available literature and offer recommendations to update select areas within the previous guidelines.4 This document will focus on care specific to COVID-19 patients receiving ECMO and recommended alterations in the utilization of ECMO during a pandemic. We recommend referral to existing guidelines for general ECMO practices.2

reference link : https://journals.lww.com/asaiojournal/Fulltext/2021/05000/Extracorporeal_Membrane_Oxygenation_for_COVID_19_.3.aspx

referenc elink :More information: Ashwin Kumar Vutha et al, A microfluidic device for real-time on-demand intravenous oxygen delivery, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2115276119


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