The Journal of Physiology, Journal Year: 2023, Volume and Issue: 601(20), P. 4475 - 4476

Published: Sept. 27, 2023

In this issue of The Journal Physiology, Guluzade et al. (2023) tackle a fundamental property the respiratory system: how peripheral (both O2 and CO2 sensitive) central (assumed only chemoreflexes interact. Remarkably, nature importance interaction are unresolved. Data from attempts to surgically separate reflexes in animals conflicting. Studies awake dogs support hyperadditive between (e.g. Blain al., 2010), whereas nearly all reduced intact rodent experiments suggest hypoadditivity at least one variable (i.e. frequency, tidal volume, minute ventilation ( V ̇ E ${\dot V_{\mathrm{E}}}$ ) or their neuronal equivalent; e.g. Day & Wilson, 2009). humans, where physical separation has not been achieved, most data an additive Milloy 2022). Resolving explaining differences across species critical understanding we breathe. use Duffin's modified rebreathing technique mathematically dissect out humans. Specifically, authors expose participants progressive ramps (via rebreathing) while measuring ventilation. assume sufficiently slow such that compartments equilibrium any moment time. During each ramp, inspired oxygen is clamped several pre-set levels, being hyperoxia, which specifically silences chemoreceptors without having effects. then quantify for specific P ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ value different levels oxygen). ventilatory response attributed sensing calculated by subtraction hyperoxic value. Plotting these values yields line, slope taken as ‘peripheral chemoreflex sensitivity hypoxia’ (PChS) given . plot PChS points along ramps). increased with linear manner 50% participants, interpreted demonstrating chemoreflexes. contrast, they propose flattening steepening curvilinear relationships observed other indicates hypoadditive interactions, respectively. A major strength al.’s study quantitative assessment relationship participant To achieve this, utilize Akaike information criterion (AIC) approach determine whether (additive) (hypoadditive hyperadditive) model provides parsimonious explanation data. ratio AIC relative likelihood over another, subtracting (delta AIC) gives ‘strength evidence’ measure. Based on measures, conclude eight had ‘strong’ two ‘moderate’ evidence interaction; four – females interaction. described remaining five ‘weak’ These delta <2 (see Table 3 2023). our view, designation some cases overpresumptuous; others consider insufficient grounds champion another Burnham Anderson, 2004). Indeed, qualitative inspection suggests ratios demonstrate PChS– higher , indicative 4, 12, 11 13 Figure 5 also provide plots breathing frequency but chose employ analysis variables. While important gas exchange, must involve non-linear increase and/or volume increasing Such turn, likely necessitates non-additive nine appear have (Figure 6 2023), interactions 7 Thus, confirm additivity integration. As such, because it current ‘one-size-fits-all’ dogma around chemoreceptor wrong, hyperadditivity exception, rule. Moreover, showing diversity within (and extension) species, re-ignites key question contribution forms control. responses gases time constants differ up order magnitude, matched metabolic rate arterial blood per se, may be less than physiologists (the ‘heresy hypothesis’; Wilson Teppema, 2016). Alternatively, form adapted accommodate conditions, capabilities uses system. For example, required panting, special case system maintain high upper airway flow thermoregulation. Similarly, predominantly might beneficial precise control larynx speech. was present females, provided further clue need diversity: best lower absolute capacity many females. sexually dimorphic add overall outstanding ongoing debate about interactions. Please note: publisher responsible content functionality supporting supplied authors. Any queries (other missing content) should directed corresponding author article. None. Both read approved final version manuscript agree accountable aspects work ensuring questions related accuracy integrity part appropriately investigated resolved. All persons designated qualify authorship, those who authorship listed. This supported Canadian Institutes Health Research Project Grant (RJAW, RN291964-366421) Natural Sciences Engineering Council Canada Discovery (TAD, RGPIN-2016-04915). We wish thank editors staff Physiology inviting us write Perspective.

Language: Английский