The Hi-Lo Trial

The Hi-Lo Trial is comparing 30% vs 60% as initial oxygen concentration during stabilization of 23-28 week gestation preterm infants at birth.

Study Details

Oxygen is a vital element in the care of preterm infants and has been given more often than any other drug over the past 80 years. Despite this, we know very little about how much or how little oxygen is safe particularly at birth.

Preterm birth, or birth before 37 weeks’ gestation, is occurring in 8% of pregnancies in Canada. Preterm birth is associated with many health complications, particularly when the birth happens before 29 weeks’ gestation.

At this gestational age, the lungs are not fully developed and it is not uncommon for infants to have problems breathing at the time of birth. One complication that can arise is when an infant stops breathing and needs to be resuscitated. When preterm babies need to be resuscitated doctors must take special care because of the immaturity of the brain and lungs. Oxygen is used to resuscitate babies who need it, but unfortunately there is disagreement about the best oxygen concentration to use. Oxygen concentration is important because both too much and too little oxygen can cause brain injury.

Our trial aims to fill this knowledge gap by performing an international multi-center clinical trial to compare the effects of resuscitating babies less than 29 weeks’ gestational age with either a low oxygen concentration or a high oxygen concentration. The oxygen concentrations have been selected using the best available knowledge.

Our research fills a critical knowledge gap in the care of extremely preterm babies and will impact their survival both here in Canada and internationally.

Interested in joining our study?

The Hi-Lo Trial

We are working to improve the longevity of premature infant lives.

Study Phase & Randomize

In the initial study phase, hospitals will be randomized to either low or high oxygen concentration for 12 months and then the oxygen concentration will be switched to the other one.

Long-term Follow up

Once all the patients are recruited, we will perform neurodevelopmental follow-up at 18-24 months corrected age.


After the trial we will determine whether the babies resuscitated with lower oxygen or those resuscitated with higher oxygen have better survival and long-term health outcomes.

Hi-Lo Trial News

U of A medical researcher aims to help premature babies breathe easier

Neonatal specialist receives $2.2 million in federal funding to pinpoint oxygen mix needed to resuscitate preterm babies while minimizing long-term health risks.

Faculty projects garner $3.8 million in CIHR funding

Department of Pediatrics projects have successfully received a total of $3.8 million in funding from the 2019 Canadian Institute for Health Research fall awards. Find out more about the research projects.