# Using electrical impedance tomography to estimate tidal volume in bottlenose dolphins and cape fur seals in seawater and on land

## TL;DR

This study shows that electrical impedance tomography can track lung function in marine mammals both on land and in water.

## Contribution

EIT is validated as the first non-invasive imaging method for measuring tidal volume in marine mammals in seawater.

## Key findings

- EIT reliably estimated tidal volume in bottlenose dolphins and Cape fur seals on land and in water.
- EIT produced dynamic images of regional ventilation patterns in marine mammals.
- Variability in EIT measurements was linked to belt placement, body position, and electrode contact.

## Abstract

Marine mammals possess specialized respiratory adaptations that enable efficient gas exchange and resilience to extreme pressures during diving, yet direct observation of lung mechanics under pressure has been logistically challenging. Electrical impedance tomography (EIT) measures real-time changes in thoracic impedance, and provides continuous, regional maps of pulmonary air distribution. We validated EIT for estimating tidal volume (VT) in bottlenose dolphins (Tursiops spp.) and Cape fur seals (Arctocephalus pusillus) both on land and in water. EIT reliably tracked VT in both taxa, showing strong within-trial consistency, with between-trial variability attributable to belt placement, body position and electrode contact. EIT also generated dynamic functional images of regional ventilation, revealing spatial and temporal patterns of lung filling and emptying. These results demonstrate that EIT is the first non-invasive imaging method validated for marine mammals in seawater, representing a critical step toward visualizing lung function during diving.

Summary: A validation of electrical impedance tomography (EIT) for marine mammals demonstrates its first successful use in seawater, a major step toward underwater physiological applications.