Dear all, Me and my co-authors are pleased to share our recent publication with you: Cauture, F., SterbaBoatwright, B., Miedler, S., Rocho-Levine, J., Harms, C. and Fahlman, A. (2019). Using Respiratory Sinus Arrhythmia to Estimate Inspired Tidal Volume in the Bottlenose Dolphin (Tursiops truncatus). Frontiers in Physiology 10. 128. doi: 10.3389/fphys.2019.00128 The article describes heart rate changes associated with breathing and uses these to assess how well they correlate with inspired tidal volume. In addition, once we correct the resting heart rate for the respiratory sinus arrhythmia (RSA) it appears that the resting heart rate at the surface is close to, or similar to the heart rate reported for diving dolphins. Consequently, without accounting for the RSA studies may incorrectly overestimate the importance of the dive response in diving dolphins. We realize this may be controversial but deserves further investigation. A B S T R A C T Man-made environmental change may have significant impact on apex predators, like marine mammals. Thus, it is important to assess the physiological boundaries for survival in these species, and assess how climate change may affect foraging efficiency and the limits for survival. In the current study, we investigated whether the respiratory sinus arrhythmia (RSA) could estimate tidal volume (VT) in resting bottlenose dolphins. For this purpose, we measured respiratory flow and electrocardiogram (ECG) in five adult bottlenose dolphins (Tursiops truncatus) at rest while breathing voluntarily. Initially, an exponential decay function, using three parameters (baseline heart rate, the change in heart rate following a breath, and an exponential decay constant) was used to describe the temporal change in instantaneous heart rate following a breath. The three descriptors, in addition to body mass, were used to develop a Generalized Additive Model (GAM) to predict the inspired tidal volume (VTinsp). The GAM allowed us to predict VTinsp with an average ( SD) overestimate of 3 2%. A jackknife sensitivity analysis, where 4 of the five dolphins were used to fit the GAM and the 5th dolphin used to make predictions resulted in an average overestimate of 2 10%. Future studies should be used to assess whether similar relationships exist in active Please feel free to download the article here (open access): https://www.frontiersin.org/article/10.3389/fphys.2019.00128 <https://www.frontiersin.org/article/10.3389/fphys.2019.00128> If you have additional questions or cannot download a copy of the paper, please send an email to: afahlman@whoi.edu Sincerely, Andreas