Seismocardiography while sleeping at high altitude

Current advancements in sensor technology allow the prolonged assessment of the seismocadiogram (SCG) out of the laboratory setting. Aim of this study is to evaluate whether SCG, as measured by a recently proposed wearable device, can detect cardio-respiratory alterations during sleep in healthy subjects exposed to high altitude hypoxia. Sternal SCG, ECG, respiration and oxygen saturation were recorded by a smart garment (the MagIC-SCG system) in 6 volunteers at 4554 m asl during night sleep. Recordings were repeated at sea level in two subjects. Periods with and without sleep apneas (known to occur at high altitude) were selected for the analysis. SCG components associated to the first (S1) and second (S2) heart sound and the swing of low-frequency SCG were assessed in each segment. As compared with sea level data, SCG waves showed a larger S1 component and a larger low-frequency swing at high altitude. The magnitude of these features did not differ in data segments with and without sleep apneas. The recordings showed that our smart garment can assess SCG during sleep in extreme environment. Results suggest that 1) hypobaric hypoxia during sleep induces alterations in SCG parameters related to cardiac mechanics and 2) these alterations are not related to the occurrence of sleep apneas.