The Effect of Dry and Humid Hot Air Inhalation on Expired Relative Humidity During Exercise

Turner, Nina L.; Parker, John N.; Hudnall, Judy

doi:10.1080/15298669291359618

Cited by 5 publications

(4 citation statements)

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“…Expired air temperature varies considerably for different mammals and birds (e.g., 39) and with T a and RH (15), so it could modulate respiratory EWL. RH of expired air is generally assumed to be 100% (saturated) at expired air temperature (e.g., 10,20), but has been measured at less than 100% for camels (40), ostrich (55), sheep (20), and humans (46), so desaturation of expired air is one conceivable mechanism for reducing respiratory EWL.…”

Section: Discussionmentioning

confidence: 99%

Physiological responses of a rodent to heliox reveal constancy of evaporative water loss under perturbing environmental conditions

Cooper

Withers

2014

American Journal of Physiology-Regulatory, Integrative and Comp

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Total evaporative water loss of endotherms is assumed to be determined essentially by biophysics, at least at temperatures below thermoneutrality, with evaporative water loss determined by the water vapor deficit between the animal and the ambient air. We present here evidence, based on the first measurements of evaporative water loss for a small mammal in heliox, that mammals may have a previously unappreciated ability to maintain acute constancy of total evaporative water loss under perturbing environmental conditions. Thermoregulatory responses of ash-grey mice (Pseudomys albocinereus) to heliox were as expected, with changes in metabolic rate, conductance, and respiratory ventilation consistent with maintaining constancy of body temperature under conditions of enhanced heat loss. However, evaporative water loss did not increase in heliox. This is despite our confirmation of the physical effect that heliox augments evaporation from nonliving surfaces, which should increase cutaneous water loss, and increases minute volume of live ash-grey mice in heliox to accommodate their elevated metabolic rate, which should increase respiratory water loss. Therefore, mice had not only a thermoregulatory but also a hygroregulatory response to heliox. We interpret these results as evidence that ash-grey mice can acutely control their evaporative water loss under perturbing environmental conditions and suggest that hygroregulation at and below thermoneutrality is an important aspect of the physiology of at least some small mammals.

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Section: Discussionmentioning

confidence: 99%

Physiological responses of a rodent to heliox reveal constancy of evaporative water loss under perturbing environmental conditions

Cooper

Withers

2014

American Journal of Physiology-Regulatory, Integrative and Comp

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“…A metabolic simulator does not fully mimic human exercise; for example, it uses dry gasses, while expired human breaths contain ~75% relative humidity during exercise in typical room conditions. 44 Similarly, the temperature of the simulator gasses is lower (typically room temperature of ~21°C vs. ~28-30°C in expired human gas during exercise in typical laboratory room conditions 44,45 ), and the simulated breathing pattern is different (stable sinusoidal vs. individual human breathing patterns, with its natural fluctuations in volume, pressure and breathing frequency). 46 A tertiary aim was, therefore, to verify the results obtained during the simulation experiments by comparing all systems against each other during a steady-state cycling test in welltrained individuals.…”

Section: Introductionmentioning

confidence: 99%

Accuracy of respiratory gas variables, substrate, and energy use from 15 CPET systems during simulated and human exercise

Van Hooren,

Souren,

Bongers

2023

Scandinavian Med Sci Sports

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PurposeVarious systems are available for cardiopulmonary exercise testing (CPET), but their accuracy remains largely unexplored. We evaluate the accuracy of 15 popular CPET systems to assess respiratory variables, substrate use, and energy expenditure during simulated exercise. Cross‐comparisons were also performed during human cycling experiments (i.e., verification of simulation findings), and between‐session reliability was assessed for a subset of systems.MethodsA metabolic simulator was used to simulate breath‐by‐breath gas exchange, and the values measured by each system (minute ventilation [V̇E], breathing frequency [BF], oxygen uptake [V̇O2], carbon dioxide production [V̇CO2], respiratory exchange ratio [RER], energy from carbs and fats, and total energy expenditure) were compared to the simulated values to assess the accuracy. The following manufacturers (system) were assessed: COSMED (Quark CPET, K5), Cortex (MetaLyzer 3B, MetaMax 3B), Vyaire (Vyntus CPX, Oxycon Pro), Maastricht Instruments (Omnical), MGC Diagnostics (Ergocard Clinical, Ergocard Pro, Ultima), Ganshorn/Schiller (PowerCube Ergo), Geratherm (Ergostik), VO2master (VO2masterPro), PNOĒ (PNOĒ), and Calibre Biometrics (Calibre).ResultsAbsolute percentage errors during the simulations ranged from 1.15%–50.3% for V̇E, 1.05–3.79% for BF, 1.10%–17.5% for V̇O2, 1.07%–18.3% for V̇CO2, 0.62%–14.8% for RER, 5.52%–99.0% for Kcal from carbs, 5.13%–133% for Kcal from fats, and 0.59%–12.1% for total energy expenditure. Between‐session variation ranged from 0.86%–22.4% for V̇O2 and 1.14%–20.2% for V̇CO2, respectively.ConclusionThe error of respiratory gas variables, substrate, and energy use differed substantially between systems, with only a few systems demonstrating a consistent acceptable error. We extensively discuss the implications of our findings for clinicians, researchers and other CPET users.

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“…In particular, because waterpipe smoke passes through the water prior to inhalation, it may be more humid than cigarette smoke, thus potentially affecting our measurements. We intend to address this issue in the future by measuring humidity in the lab and expired smoke, but this factor is likely to have limited influence on our results (mainly on the larger PM 10 particles), given known particle properties and the modulating influence of the respiratory tract on expired air humidity (Turner, Parker, & Hudnall, 1992;Wilson & Suh, 1997).…”

Section: Discussionmentioning

confidence: 96%

Waterpipe-associated particulate matter emissions

Maziak

Rastam

Ibrahim

et al. 2008

Nicotine & Tobacco Res.

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Waterpipe tobacco smoking is increasingly common worldwide, and evidence about its harmful effects to smokers is emerging. However, no studies have investigated the potential exposure of nonsmokers to waterpipe smoke. We measured particulate matter (PM) emissions (PM2.5, PM10) before and during laboratory sessions in which 20 individuals used a waterpipe to smoke tobacco and 20 individuals smoked a cigarette (10 for each particle-size/smoking-method), as well as 10 waterpipe and 10 cigarette smoldering sessions (i.e., without a smoker). A TSI-SidePak aerosol monitor obtained PM2.5, PM10 background, smoking, and maximum levels. Mean PM2.5 rose 447% for waterpipe (from 48 microg/m3 background to 264 microg/m3 smoking), and by 501% for cigarettes (from 44 microg/m3 to 267 microg/m3), whereas mean PM10 rose by 563% for waterpipe (from 55 microg/m3 to 365 microg/m3), and by 447% for cigarettes (from 52 microg/m3 to 287 microg/m3) (p<.05 for all). The increase in PM during cigarette smoking was due primarily to PM2.5, given that the proportion of PM2.5 from total PM10 increase was 95% compared with 70% for waterpipe (p<.05). Maximum PM2.5 was 908 microg/m3 for waterpipe and 575 microg/m3 for cigarettes, whereas maximum PM10 was 1052 microg/m3 for waterpipe and 653 microg/m3 for cigarettes. Mean PM2.5 and PM10 smoldering levels did not differ from background for waterpipe but were significantly higher for cigarettes (PM2.5: 33-190 microg/m3; PM10: 42-220 microg/m3). Policymakers considering clean air regulations should include waterpipe tobacco smoking, and the public should be warned about this source of smoke exposure.

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The Effect of Dry and Humid Hot Air Inhalation on Expired Relative Humidity During Exercise

Cited by 5 publications

References 0 publications

Physiological responses of a rodent to heliox reveal constancy of evaporative water loss under perturbing environmental conditions

Physiological responses of a rodent to heliox reveal constancy of evaporative water loss under perturbing environmental conditions

Accuracy of respiratory gas variables, substrate, and energy use from 15 CPET systems during simulated and human exercise

Waterpipe-associated particulate matter emissions

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