Assessing chemoreflexes and oxygenation in the context of acute hypoxia: Implications for field studies

Swallow-breathing coordination during incremental ascent to altitude

“…Additionally respiratory rate, heart rate, mean arterial pressure (MAP), truenormalV˙ I , SpO 2 , P ET CO 2 and steady-state chemoreflex drive (SS-CD) were measured. The SS-CD was computed by calculating a stimulus index (SI; P ET CO 2 /SpO 2 ), and then comparing minute ventilation against SI (Bruce CD, 2018; Pfoh et al, 2017). A repeated measures ANOVA was used to determine differences in swallow motor pattern and respiratory parameters across the three elevations with significance at p ≤ 0.05, and if significance was met the LSD post-hoc test was used.…”

“…Incremental ascent to high altitudes (>2,000m) produces hypoxia (low O 2 ) induced hyperventilation, resulting in hypocapnia (low CO 2 ) (Huang et al, 1984; Weil, 1986). As climbers acclimatize to high altitude they can reach a new “steady-state chemoreflex drive” in which balance is achieved between hypoxia and hypocapnia, while ventilation parameters can return to near baseline conditions (Bruce CD, 2018; Pfoh et al, 2017). Additionally, healthy individuals that are not acclimatized to high altitude conditions can have changes in pulmonary mechanics due to interstitial pulmonary edema, which can be accompanied with accumulation of fluid within and around the airway walls (Cremona et al, 2002; Pratali et al, 2010; Schoene et al, 1988).…”

Coordination of airway protective behaviors and swallow: effects of afferent feedback and sex.

“…Additionally respiratory rate, heart rate, mean arterial pressure (MAP), V̇I, SpO2, PETCO2 and steady-state chemoreflex drive (SS-CD) were measured. The SS-CD was computed by calculating a stimulus index (SI; PETCO2/SpO2), and then comparing minute ventilation against SI (Bruce CD, 2018;Pfoh, Steinback, Berg, Bruce, & Day, 2017). A repeated measures ANOVA was used to determine differences in swallow motor pattern and respiratory parameters across the three elevations with significance at p ≤ 0.05, and if significance was met the LSD posthoc test was used.…”

“…The changes in swallow and swallow-breathing coordination were also accompanied by changes/adaption of the chemoreflexes driving breathing. It is known that these reflexes become more dynamic as individuals acclimatize to their respective environment (Pfoh, Steinback, Berg, Bruce, & Day, 2017) (Steinback & Poulin). To asses this adaptation, Pfoh and colleagues (2017) created an index of steady-state chemoreflex drive (SS-CD), taking into account resting ventilation indexed against the overall contributions of both low O2 and low CO2 during exposure to hypoxia.…”

“…Incremental ascent to high altitudes (>2,000m) produces hypoxia (low O2) induced hyperventilation, resulting in hypocapnia (low CO2) (Huang, Alexander, Grover, Maher, McCullough, McCullough, Moore, Sampson, Weil, & Reeves, 1984;Weil, 1986). As climbers acclimatize to high altitude they can reach a new "steady-state chemoreflex drive" in which balance is achieved between hypoxia and hypocapnia, while ventilation parameters can return to near baseline conditions (Bruce CD, 2018;Pfoh, Steinback, Berg, Bruce, & Day, 2017). Additionally, healthy individuals that are not acclimatized to high altitude conditions can have changes in pulmonary mechanics due to interstitial pulmonary edema, which can be accompanied with accumulation of fluid within and around the airway walls (Cremona, Asnaghi, Baderna, Brunetto, Brutsaert, Cavallaro, Clark, Cogo, Donis, & Lanfranchi, 2002;Pratali, Cavana, Sicari, & Picano, 2010;Schoene, Swenson, Pizzo, Hackett, Roach, Mills Jr, Henderson Jr, & Martin, 1988).…”