When a subject is totally immersed in water while holding his breath, a loss of buoyancy occurs.This phenomenon can be demonstrated by resting the subject on 1 pan of a balance, the loss of buoyancy being reflected as a gain in weight on the balance. This gain in weight (or loss of buoyancy) was first observed by us while determining body density by an underwater weighing method (1). This gain ...

Background Cardiac magnetic resonance imaging (CMRI) for infants and young children typically requires sedation. General anaesthesia can eliminate motion artefact and permits controlled ventilation with breath-holding during imaging to limit respiratory artefact, but this technique typically requires frequent changes in respiratory support that may impair pulmonary function, and pauses in image...

The purpose of this study was to investigate how fast three-dimensional (3D) MR image quality is affected by breath-holding and to develop an optimal breath-holding strategy that minimizes artifact in the event of an incomplete breath-hold. A computer model was developed to study variable-duration breath-holds during fast 3D imaging. Modeling was validated by 3D gradient-echo imaging performed ...

Background Cardiac MRI requires a steady cardiac rhythm for ECGgating, and multiple breath-holds to minimize respiratory artifacts. By employing a non-Cartesian parallel imaging in form of through-time radial GRAPPA [1], accelerated imaging can be performed with temporal resolutions of < 50 ms, obviating the need for gating or breath-holding. breath-holding. We tested the hypothesis that volume...

BACKGROUND Transfer factor of the lung for carbon monoxide (TLCO) was measured by a new method based on analysis of the ratio of the concentrations of carbon monoxide to an inert gas (methane) relative to lung volume during a constant exhalation. Since this new technique is based solely upon exhalation, anomalies associated with inspiration and breath holding do not affect results. Additionally...

A substantial portion of sinus arrhythmia in conscious humans appears to be caused by the CO2-dependent central respiratory rhythm. Under some circumstances, therefore, sinus arrhythmia might indicate the presence of the central respiratory rhythm. Humans can voluntarily modify their central respiratory rhythm (e.g., by pacing breathing or by delaying or advancing breaths), but it is not clear ...