Koo P, et al. – The researchers performed this work to measure the change in end–expiratory lung volume (EELV) following sleep onset and to assess the association between change in EELV and sleep–disordered breathing. They suggested that magnetometry provided a precise, unobtrusive, and continuous means to study lung volume changes during sleep. They observed that EELV declines from sleep onset, reaching its nadir during stage R sleep. The reduction in EELV in stage R sleep was correlated with lower mean oxygen saturation but was not related to greater sleep–disordered breathing.