Closed system respirometry may underestimate tissue gas exchange and bias the respiratory exchange ratio (RER)

Malte, Christian Lind; Nørgaard, Simon; Wang, Tobias

doi:10.1016/j.cbpa.2015.10.026

Cited by 13 publications

(10 citation statements)

References 17 publications

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“…The prolonged lack of steady state is particularly relevant to studies involving repetitive exposures with short intervals, such as intermittent hypoxia, where CO 2 stores are unlikely to be restored between individual exposures if these are in the order of minutes to a few hours. The progressive build-up of CO 2 during hypercapnia is also relevant to respirometry, where the rate of CO 2 excretion is likely to be underestimated (Malte et al, 2016b).…”

Section: Discussionmentioning

confidence: 99%

“…The slow transient adjustment of CO 2 stores leading to RER values different from steady state may also lead to erroneous interpretations regarding tissue CO 2 production and hence RQ of the tissues if assuming a steady state (Malte et al, 2016b). The tendency for this may be greatest during hypoventilation, where time constants are long due to the low ventilation rates (Fig.…”

Section: Implications For Experimental Designmentioning

confidence: 99%

“…The magnitude and temporal development of these changes depend critically on the ventilatory and circulatory responses (Malte et al, 2016b), but, although ventilatory responses to hypercapnia and hypoxia have been described in many reptiles (for reviews see Milsom, 1991;Shelton et al, 2010;Wang et al, 1998), the associated transients in bodily gas stores have not been quantified. Consequently, it is not clear how long it takes to achieve a steady state for gas exchange, i.e.…”

Section: Introductionmentioning

confidence: 99%

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The long road to steady state in gas exchange: metabolic and ventilatory responses to hypercapnia and hypoxia in Cuvier’s dwarf caiman

Malte

Wang

2016

Journal of Experimental Biology

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Animals with intermittent lung ventilation and those exposed to hypoxia and hypercapnia will experience fluctuations in the bodily O 2 and CO 2 stores, but the magnitude and duration of these changes are not well understood amongst ectotherms. Using the changes in the respiratory exchange ratio (RER; CO 2 excretion divided by O 2 uptake) as a proxy for changes in bodily gas stores, we quantified time constants in response to hypoxia and hypercapnia in Cuvier's dwarf caiman. We confirm distinct and prolonged changes in RER during and after exposure to hypoxia or hypercapnia. Gas exchange transients were evaluated in reference to predictions from a twocompartment model of CO 2 exchange to quantify the effects of the levels of hypoxia and hypercapnia, duration of hypercapnia (30-300 min) and body temperature (23 versus 33°C). For hypercapnia, the transients could be adequately fitted by two-phase exponential functions, and slow time constants (after 300 min hypercapnia) concurred reasonably well with modelling predictions. The slow time constants for the decays after hypercapnia were not affected by the level of hypercapnia, but they increased (especially at 23°C) with exposure time, possibly indicating a temporal and slow recruitment of tissues for CO 2 storage. In contrast to modelling predictions, elevated body temperature did not reduce the time constants, probably reflecting similar ventilation rates in transients at 23 and 33°C. Our study reveals that attainment of steady state for gas exchange requires considerable time and this has important implications for designing experimental protocols when studying ventilatory control and conducting respirometry.

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Section: Discussionmentioning

confidence: 99%

Section: Implications For Experimental Designmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The long road to steady state in gas exchange: metabolic and ventilatory responses to hypercapnia and hypoxia in Cuvier’s dwarf caiman

Malte

Wang

2016

Journal of Experimental Biology

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“…On this basis, minimal error is obtained by assuming RER=0.85, restricting the maximum possible error to ±3.2% (Vleck, 1987). Prolonged closure of the metabolic system can cause more substantial errors of approximately 10-13% because of the greater storage capacity of organismal water for CO 2 than for O 2 (Malte et al, 2016).…”

Section: Respiratory Exchange Ratio and O 2 Limitationmentioning

confidence: 99%

Measuring metabolic rates of small terrestrial organisms by fluorescence-based closed-system respirometry

Tomlinson

Dalziell

Withers

et al. 2018

Journal of Experimental Biology

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We explore a recent, innovative variation of closed-system respirometry for terrestrial organisms, whereby oxygen partial pressure ( ) is repeatedly measured fluorometrically in a constant-volume chamber over multiple time points. We outline a protocol that aligns this technology with the broader literature on aerial respirometry, including the calculations required to accurately convert O depletion to metabolic rate (MR). We identify a series of assumptions, and sources of error associated with this technique, including thresholds where O depletion becomes limiting, that impart errors to the calculation and interpretation of MR. Using these adjusted calculations, we found that the resting MR of five species of angiosperm seeds ranged from 0.011 to 0.640 ml g h, consistent with published seed MR values. This innovative methodology greatly expands the lower size limit of terrestrial organisms that can be measured, and offers the potential for measuring MR changes over time as a result of physiological processes of the organism.

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“…18 to 1.3 kPa. Inducing progressive hypoxia using this method increases CO 2 levels as the fish respire (Malte et al ., ; Snyder et al ., ). A degree of hypercapnia must therefore have been present in the water during our experiments (Hughes, ; Keys, ; Piiper & Scheid, ; Piiper et al ., ), but due to the fast induction of hypoxia this is not believed to have affected our results (Regan & Richards, ).…”

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confidence: 99%

Are all bony fishes oxygen regulators? Evidence for oxygen regulation in a putative oxygen conformer, the swamp eel Synbranchus marmoratus

Svendsen

Johansen²,

Bushnell

et al. 2019

Journal of Fish Biology

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Closed system respirometry may underestimate tissue gas exchange and bias the respiratory exchange ratio (RER)

Cited by 13 publications

References 17 publications

The long road to steady state in gas exchange: metabolic and ventilatory responses to hypercapnia and hypoxia in Cuvier’s dwarf caiman

The long road to steady state in gas exchange: metabolic and ventilatory responses to hypercapnia and hypoxia in Cuvier’s dwarf caiman

Measuring metabolic rates of small terrestrial organisms by fluorescence-based closed-system respirometry

Are all bony fishes oxygen regulators? Evidence for oxygen regulation in a putative oxygen conformer, the swamp eel Synbranchus marmoratus

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