Unrestrained Acoustic Plethysmograph for Measuring Tidal Volume in Mice

Reynolds, Jeffrey; Frazer, David G.

doi:10.1007/s10439-006-9159-8

Cited by 13 publications

(16 citation statements)

References 17 publications

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“…Because of the complexity of factors involved in the quantitative interpretation of an open-flow plethysmographic signal (12,29,38,43,50), this determination of estVT and estV E provided a semiquantitative index that is represented in the units that are appropriate for direct measurements of tidal volume and minute ventilation.…”

Section: Discussionmentioning

confidence: 99%

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Acetazolamide suppresses the prevalence of augmented breaths during exposure to hypoxia

Bell¹,

Haouzi²

2009

American Journal of Physiology-Regulatory, Integrative and Comp

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Augmented breaths, or "sighs," commonly destabilize respiratory rhythm, precipitating apneas and variability in the depth and rate of breathing, which may then exacerbate sleep-disordered breathing in vulnerable individuals. We previously demonstrated that hypocapnia is a unique condition associated with a high prevalence of augmented breaths during exposure to hypoxia; the prevalence of augmented breaths during hypoxia can be returned to normal simply by the addition of CO(2) to the inspired air. We hypothesized that counteracting the effect of respiratory alkalosis during hypocapnic hypoxia by blocking carbonic anhydrase would yield a similar effect. We, therefore, investigated the effect of acetazolamide on the prevalence of augmented breaths in the resting breathing cycle in five awake, adult male rats. We found a 475% increase in the prevalence of augmented breaths in animals exposed to hypocapnic hypoxia compared with room air. Acetazolamide treatment (100 mg/kg i.p. bid) for 3 days resulted in a rapid and potent suppression of the generation of augmented breaths during hypoxia. Within 90 min of the first dose of acetazolamide, the prevalence of augmented breaths in hypoxia fell to levels that were no greater than those observed in room air. On cessation of treatment, exposure to hypocapnic hypoxia once again caused a large increase in the prevalence of augmented breaths. These results reveal a novel means by which acetazolamide acts to stabilize breathing and may help explain the beneficial effects of the drug on breathing stability at altitude and in patients with central forms of sleep-disordered breathing.

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Section: Discussionmentioning

confidence: 99%

“…Animals were monitored in each condition for 20 -25 min. with its experimental benefits and limitations, has been discussed at length (29,38,43,50).…”

Section: Equipmentmentioning

confidence: 99%

Acetazolamide suppresses the prevalence of augmented breaths during exposure to hypoxia

Bell¹,

Haouzi²

2009

American Journal of Physiology-Regulatory, Integrative and Comp

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“…Rather it provides a pneumogram that results from a complex set of respiratory related changes that occur during the inspiration and expiration of respired gases. The technical aspects of this methodology and related techniques have been critically discussed in detail elsewhere (31,38,49,59). As such, our determinations of respiratory indexes of tidal volume and minute ventilation are semiquantitative and represented throughout the manuscript as estVT and est, respectively, where "est" is estimated, to clearly reflect this fact.…”

Section: Methodsmentioning

confidence: 99%

“…The main advantages of this technique are that fact that it is noninvasive so animals can be studied repeatedly across several days of intervention, and several hours of continuous monitoring at a given time are easily performed. However, plethysmography provides indirect measurements, and as with any form of this monitoring approach important technical limitations on the data should be realized and this has been the topic of extensive study and discussion elsewhere (31,38,49,59). Our animal monitoring provided an indirect index of tidal volume and minute ventilation which we have referred to as estVT and estV E, respectively.…”

Section: Peripheral Chemoreflex Stimulation Can Trigger Abs Despite Tmentioning

confidence: 99%

The “other” respiratory effect of opioids: suppression of spontaneous augmented (“sigh”) breaths

Bell

Elizabeth

Haouzi

2011

Journal of Applied Physiology

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The purpose of this study was to examine the effects of a clinically relevant opioid on the production of augmented breaths (ABs) in unanesthetized animals breathing normal room air, using a dosage which does not depress breathing. To do this we monitored breathing noninvasively, in unrestrained animals before and after subcutaneous injection of either morphine, or a saline control. The effect of ketamine/xylazine was also studied to determine the potential effect of an alternative sedative agent. Last, the effect of naloxone was studied to determine the potential influence of endogenous opioids in regulating the normal incidence of ABs. Morphine (5 mg/kg) had no depressive effect on breathing, but completely eliminated ABs in all animals in room air (P = 0.027). However, when animals breathed hypoxic air (10% O(2)), animals did express ABs, although their incidence was still reduced by morphine (P < 0.001). This was not a result of sedation per se, as ABs continued at their normal rate in room air during sedation with ketamine. Naloxone had no effect on breathing or AB production, and so endogenous opioids are not likely involved in regulating their rate of production under normal conditions. Our results show that in unanesthetized animals breathing normal room air, a clinically relevant opioid eliminates ABs, even at a dose that does not cause respiratory depression. Despite this, hypoxia-induced stimulation of breathing can facilitate the production of ABs even with the systemic opioid present, indicating that peripheral chemoreceptor stimulation provides a potential means of overcoming the opioid-induced suppression of these respiratory events.

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“…Reynolds and Frazer (10) recently suggested a novel approach to unrestrained plethysmography using an acoustic resonance approach. In their method, a mouse is enclosed in a chamber similar in dimension to that used in barometric plethysmography.…”

Section: Small Animal Plethysmography; Helmholtz Resonatormentioning

confidence: 99%

Acoustic plethysmography measures breathing in unrestrained neonatal mice

Daubenspeck

Li²,

Nattie³

2008

Journal of Applied Physiology

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Measurement of breathing volumes in neonatal mice is of growing importance in order to characterize the influence of development and genetic modifications on respiratory control to evaluate hypotheses concerned with human infant deficits that may affect sudden infant death syndrome, for example. Current techniques require undesirable physical constraints or incur possible artifacts specific to very small animals. We have examined the utility of a recently proposed approach using an acoustic resonance procedure that does not require undue physical constraint beyond placement in the acoustic plethysmograph. We show here that this approach can be applied to baby mice 5 days after birth and that it can be accurately calibrated. In addition, this approach should be useful to study unrestrained neonatal mice under conditions where body temperature approaches environmental temperature and barometric plethysmography cannot be used.

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Unrestrained Acoustic Plethysmograph for Measuring Tidal Volume in Mice

Cited by 13 publications

References 17 publications

Acetazolamide suppresses the prevalence of augmented breaths during exposure to hypoxia

Acetazolamide suppresses the prevalence of augmented breaths during exposure to hypoxia

The “other” respiratory effect of opioids: suppression of spontaneous augmented (“sigh”) breaths

Acoustic plethysmography measures breathing in unrestrained neonatal mice

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