Cerebrovascular and blood pressure responses during voluntary apneas are larger than rebreathing

Marullo, Anthony L.; Bruce, Christina D.; Pfoh, Jamie R.; Chauhan, Uday V.; Abrosimova, Maria; Berg, Emily R. Vanden; Skow, Rachel J.; Davenport, Margie H.; Strzalkowski, Nicholas D. J.; Steinback, Craig D.; Day, Trevor A.

doi:10.1007/s00421-021-04864-5

Cited by 2 publications

(2 citation statements)

References 31 publications

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“…Thus, it seems as if apnea is a more potent initiator of sympathetic nervous activity to the spleen than the chemoreceptor stimulation provided by rebreathing. This conclusion is in line with the observations that sympathetic responses, such as increases in TPR and MAP, are greater during apnea than during rebreathing, both in the present study and the studies by Badrov et al (2017) and Marullo et al (2022) . Also, Steinback et al (2010) found that apnea induced peripheral vasoconstriction and a pressor response, with a muscle sympathetic nerve activity response, which were all attenuated during rebreathing, further lending support to the notion that apnea could be more effective in triggering sympathetically-induced splenic contraction than rebreathing.…”

Section: Discussionsupporting

confidence: 93%

“…The MAP did however increase significantly more during apnea than during rebreathing, an expected effect of the attenuated rise in TPR during rebreathing. Similar findings have previously been reported ( Badrov et al, 2017 ; Marullo et al, 2022 ), and this further support that continued respiratory movements attenuate the sympathetic responses to apnea. It is likely that the increase in cardiac afterload, by the observed increases in arterial pressure in the present study, contributed to the reduction in SV during the apneas and rebreathing periods.…”

Section: Discussionsupporting

confidence: 91%

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Splenic contraction and cardiovascular responses are augmented during apnea compared to rebreathing in humans

et al. 2023

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The spleen contracts during apnea, releasing stored erythrocytes, thereby increasing systemic hemoglobin concentration (Hb). We compared apnea and rebreathing periods, of equal sub-maximal duration (mean 137 s; SD 30), in eighteen subjects to evaluate whether respiratory arrest or hypoxic and hypercapnic chemoreceptor stimulation is the primary elicitor of splenic contraction and cardiovascular responses during apnea. Spleen volume, Hb, cardiovascular variables, arterial (SaO2), cerebral (ScO2), and deltoid muscle oxygen saturations (SmO2) were recorded during the trials and end-tidal partial pressure of oxygen (PETO2) and carbon dioxide (PETCO2) were measured before and after maneuvers. The spleen volume was smaller after apnea, 213 (89) mL, than after rebreathing, 239 (95) mL, corresponding to relative reductions from control by 20.8 (17.8) % and 11.6 (8.0) %, respectively. The Hb increased 2.4 (2.0) % during apnea, while there was no significant change with rebreathing. The cardiovascular responses, including bradycardia, decrease in cardiac output, and increase in total peripheral resistance, were augmented during apnea compared to during rebreathing. The PETO2 was higher, and the PETCO2 was lower, after apnea compared to after rebreathing. The ScO2 was maintained during maneuvers. The SaO2 decreased 3.8 (3.1) % during apnea, and even more, 5.4 (4.4) %, during rebreathing, while the SmO2 decreased less during rebreathing, 2.2 (2.8) %, than during apnea, 8.3 (6.2) %. We conclude that respiratory arrest per se is an important stimulus for splenic contraction and Hb increase during apnea, as well as an important initiating factor for the apnea-associated cardiovascular responses and their oxygen-conserving effects.

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Section: Discussionsupporting

confidence: 93%

Section: Discussionsupporting

confidence: 91%

Splenic contraction and cardiovascular responses are augmented during apnea compared to rebreathing in humans

et al. 2023

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On the use and misuse of cerebral hemodynamics terminology using transcranial Doppler ultrasound: a call for standardization

Skow

Brothers

Claassen

et al. 2022

American Journal of Physiology-Heart and Circulatory Physiology

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Cerebral hemodynamics (e.g., cerebral blood flow) can be measured and quantified using many different methods, with Transcranial Doppler ultrasound (TCD) being one of the most commonly utilized approaches. In human physiology, the terminology used to describe metrics of cerebral hemodynamics are inconsistent, and in some instances technically inaccurate; this is especially true when evaluating, reporting, and interpreting measures from TCD. Therefore, this perspectives article presents recommended terminology when reporting cerebral hemodynamic data. We discuss the current use and misuse of the terminology in the context of using TCD to measure and quantify cerebral hemodynamics and present our rationale and consensus on the terminology that we recommend moving forward. For example, one recommendation is to discontinue use of the term "cerebral blood flow velocity" in favor of "cerebral blood velocity" with precise indication of the vessel of interest. We also recommend clarity when differentiating between discrete cerebrovascular regulatory mechanisms, namely cerebral autoregulation, neurovascular coupling, and cerebrovascular reactivity. This will be a useful guide for investigators in the field of cerebral hemodynamics research.

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Cerebrovascular and blood pressure responses during voluntary apneas are larger than rebreathing

Cited by 2 publications

References 31 publications

Splenic contraction and cardiovascular responses are augmented during apnea compared to rebreathing in humans

Splenic contraction and cardiovascular responses are augmented during apnea compared to rebreathing in humans

On the use and misuse of cerebral hemodynamics terminology using transcranial Doppler ultrasound: a call for standardization

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