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Variation of respiratory and pulse events in multiple system atrophy
Yasuyoshi Ohshima1, Satoshi Hokari1, Asuka Nagai1
1Department of Respiratory Medicine and Infectious Diseases, Niigata University Graduate School of Medical and Dental Sciences, Niigata University, 1-757 Asahimachidori, Chuoku, Niigata City, Niigata 951-8510, Japan.
Introduction:
A study is eagerly awaited that will reveal the unknown mechanisms of multiple system atrophy (MSA), in which the risk of sudden death is the greatest during sleep. The blunted pulse response to nocturnal respiratory events suggests an abnormal cardiac response to a sleep-related breathing disorder. Patients with MSA have a lower pulse event index (PEI), despite a greater hypoxic burden and a similar frequency of respiratory events. However, the evidence is speculative and not directly proven, and many limitations require further study.
Methods:
We conducted a retrospective analysis of 26 patients with MSA who had undergone overnight oximetry between April 2016 and December 2022.
Results:
The median 4% oxyhemoglobin desaturation index (ODI) was 11.6/h, the 6-bpm PEI was 8.9/h, and the PEI/ODI ratio was as low as 0.91. There were three patients with suspected sudden death; all had low PEI/ODI ratios. The PEI/ODI ratio was followed over time in seven patients, all of whom had a decrease in the ratio. However, the PEI was higher than the ODI in 12/26 (46%) of the patients.
Conclusion:
A low PEI/ODI ratio, reflecting a blunted pulse response to nocturnal respiratory events in patients with MSA, may indicate a worse prognosis. This finding and the significance of the longitudinal decrease in the PEI/ODI ratio will require a prospective study.
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