論文の公開元へ健常者の体幹音響脈波を用いた要排尿時導出アルゴリズムの開発
概要
脊髄損傷者は尿意が消失して自力排尿も困難になる。その対処として適時に導尿することが推奨されているが、実際には容易ではない。我々は健常者の背部で検知した心拍動由来の体幹音響脈波(APW)から要排尿となる膀胱内尿量増加時点を導出するアルゴリズムを開発した。安静座位実験参加者のAPWを連続測定し、膀胱内尿量測定と尿意聴取を間欠的に行った。各人の測定APWから2方法で心拍動周期を求め、各々で心拍数の時間変化率を時系列で算出し、3つの極・超低周波領域のパワースペクトル(PS)を時系列で計6つ算出した。膀胱内尿量が増加した時の特徴的なPS波形を識別して、同様の波形が出現した時間帯を同定するアルゴリズムを作成した。有効実験参加者6名のデータからアルゴリズムが特徴的波形出現として同定した8時点を膀胱内尿量増加/尿意の高まりと比較したところ、真陽性が7時点、偽陽性が1時点(第一種過誤の危険率13%)となり、偽陰性(第二種過誤)はなかった。
Spinal cord injury makes a person lose the desire to urinate and leads to difficulty in voiding of urine.Catheterization at an opportune time is recommended as a coping technique, however, the practice is not easy. We have developed an algorithm for deriving the moment of a urine volume increase in the bladder until the need to void, using the acoustic pulse wave (APW) induced-heart beat via the body trunk detected at the back surface. The APW was continuously measured, and the urine volume in the bladder and subjective desire to urinate were acquired in an intermittent manner for each healthy experimental participant in a relaxed sitting position. Two time-series gradient heart rates were calculated from the heartbeat intervals calculated from each subject’s APW by two methods. Three ultra-low/very-low frequency band powers were calculated from each gradient heart rate, and total six time-series data were obtained from each subject. The characteristic waveforms of the band powers at the moment of a urine volume increase were distinguished. An algorithm was identified the moments that similar characteristic waveforms appeared. The determined algorithm derived eight identified moments among six eligible participants. Those were compared at each moment of the urine volume increase or the growing desire to urinate. Seven true-positive moments were confirmed, while one false-positive moment was confirmed (13% risk rate of type I error). There were no false-negative results (no errors of type II).
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