DR. TREVOR A. DAY

RESPIRATORY SINUS ARRHYTHMIA

Respiratory sinus arrhythmia (RSA) is a phenomenon whereby heart rate fluctuates in phase with the respiratory cycle. This is a normal phenomenon, prevalent in young healthy people, with its magnitude holding a relationship to autonomic nervous system health. Using simple ECG methods, we investigated RSA during tilt, exercise and normbaric and hypobaric (e.g., high altitude) hypoxia. Using various models to study RSA, we are interested in both the mechanisms underlying it, and the possibility utility of RSA in healthy individuals.

RESPIRATORY CHEMOREFLEXES

Central and peripheral respiratory chemoreceptors detect and respond to acute and chronic blood gas challenges (CO2 and O2). I am interested in eliciting and quantifying central and peripheral respiratory chemoreflexes in response to acute and chronic blood gas challenges in healthy human participants. We use hyperoxic rebreathing to elicit central chemoreflexes, and transient and steady-state tests to elicit peripheral chemoreflexes. We recently developed a novel index of steady-state chemoreflex drive, which we suggest accounts for contributions from both CO2 and O2, and both central and peripheral chemoreceptors. We are beginning to apply this new index to high altitude acclimatization.

HIGH ALTITUDE HYPOXIA

Ascent to high altitude imposes a chronic state of hypoxia on all organ systems. Chronic hypoxia can lead to acute mountain sickness, and it is unclear why some individuals are more tolerant than others with exposure. Solving this issue will have many applications, including trekking, climbing, exercise and military deployments to mountainous regions. I recently organized/co-organized three research expeditions to Everest Base Camp in Nepal (2016, 2017 and 2018) and an additional expedition to the Sierra Nevada Mountains in California, USA (2019). These expeditions have allowed me to investigate cardiorespiratory, cerebrovascular, hematological and acid-base acclimatization during incremental or rapid ascent to high altitude in native low-landers.

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August 2019 

Expedition Co-Organizer, Research Coordinator and Principle Investigator, California, USA

I co-organized a research expedition, co-led by Professor Richard Wilson from University of Calgary, to the renowned Barcroft laboratory (3800m) near White Mountain summit in the Sierra Nevada Mountains in California, USA, August 12-22, 2019. Along with their trainees, we collaborated with four additional principal investigators, including Drs. Ken O’Halloran (University College Cork, Ireland), Caroline Rickards (University of North Texas, TX, USA), Craig Steinback (University of Alberta, Canada) and Glen Foster (University of British Columbia, Canada). The 25 total participants included five paid trainees from MRU. We performed 12 studies related to high altitude acclimatization in humans over 10 days/nights at 3800m. 

May 2018 – June 2018

Expedition Co-Organizer, Research Coordinator and Principle Investigator, Himalaya, Nepal 

I co-organized a joint field-course and research expedition, co-led by Professor Tom Brutsaert from Syracuse University, NY, USA. Dr. Brutsaert and I organized the expedition using my previously-developed organizational infrastructure (e.g., ascent profile, local contacts), and I coordinated the research component of the expedition as in 2016 and 2017. The 29 participants included seven paid trainees from MRU, field-course students and collaborators. We performed high altitude fieldwork during incremental ascent to Everest Base Camp (5300m). 

May 2017 – June 2017 

Expedition Organizer, Research Coordinator and Principle Investigator, Himalaya, Nepal

I independently-organized a second high-altitude research expedition to Nepal. The 31 participants included 12 paid trainees from MRU, collaborators and students from other universities, industry partners and community members. We performed high altitude fieldwork during incremental ascent to Everest Base Camp (5300m). 

May 2016 – June 2016 

Expedition Organizer, Research Coordinator and Principle Investigator, Himalaya, Nepal

I developed a model of research incremental ascent to high altitude in the Nepal Himalaya, and independently-organized my first high-altitude research expedition. The 23 participants included nine paid trainees from MRU, collaborators and students from other universities, industry partners and community members. We performed high altitude fieldwork during incremental ascent to Everest Base Camp (5300m). 

February 2012 – June 2012

Collaborator, Kelowna, Canada and Himalaya, Nepal

This high-altitude research expedition to Nepal organized by Dr. Philip Ainslie, collaborator at UBC Okanagan. My MRU trainee and I were amongst 25 investigators and trainees from six countries participating in a number of studies related to acclimatization to high altitude at the Italian Pyramid Lab (5050m) in the Everest region in Nepal. Baseline testing at UBC Okanagan in early 2012. High altitude fieldwork was carried out in April-June 2012.

CENTRAL SLEEP APNEA

Central sleep apnea (CSA) is a phenomenon whereby people cycle between periods of no breathing (apnea) and over breathing (hyperventilation) during sleep. Up to 50% of congestive heart failure patients experience CSA, and it is universal at high altitude. I have recently been interested in using portable devices (e.g., accelerometry, portable polysomnography) to assess the incidence and severity of CSA in high altitude fieldwork, and link it to oxygenation during sleep at altitude.

ACID-BASE PHYSIOLOGY

Exposure to chronic hypoxia leads to sustained increases in ventilation, hypocapnia and respiratory alkalosis. Following prolonged hypocapnia, the kidneys begin eliminating bicarbonate, creating a compensatory metabolic acidosis, returning pH back to normal levels. Using arterial blood gas and urine pH data from our recent expeditions to high altitude, we are investigating (a) novel ways to analyze acid-base compensations, (b) the effects of renal compensation of cerebral blood flow in hypoxia and (c) the relationship between acid-base compensations and respiratory chemoreflex drive. Our recent data suggests that those with large renal responses better protect their pH with ascent, and this renal compensation is complete following 24-hours of rapid ascent to 3800m.