利用光學體積描記法（photoplethysmography）訊號的變化偵測陰莖勃起過程中血流動力學變化及應用於夜間陰莖勃起測試的可行性研究

彭元宏^1,4、蔡芳生²、張奕凱³、張宏江³、羅孟宗⁴、林澂⁴

¹天成醫院泌尿科、²台北慈濟醫院泌尿科、³國立台灣大學醫院院附設醫院泌尿部、⁴國立中央大學生醫科學與工程學系

The photoplethysmography (PPG) signal's change during the process of penile erection --- the implication on penile hemodynamics interpretation and the feasibility of detecting nocturnal penile tumescence (NPT)

Yuan-Hung Pong^1,4, Vincent FS Tsai², I-Kai Chang³, Hong-Chiang Chang³, Meng-Chung Lo⁴, Chen Lin⁴

¹Department of Urology, Ten Chen Hospital, Taoyuan 320, Taiwan.

²Department of Urology, Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, New Taipei 231, Taiwan.

³Department of Urology, National Taiwan University Hospital, Taipei 100, Taiwan.

⁴Department of Biomedical Sciences and Engineering, National Central University, Taoyuan 320,

Taiwan.

Purpose:

Prevailing erectile dysfunction needs objective assessment reflecting a patient's daily condition, such as a nocturnal penile tumescence (NPT) test. Prior literature ever reported the oxyhemoglobin (HbO) changes during the process of penile erection. Since oximetry measuring HbO is a non-invasive and easy method, we explored the change of photoplethysmography (PPG) signal (a common oximeter’s measuring method) during penile erection and speculated the related hemodynamics of penile erection for assessing the feasibility of detecting NPT with oximeters.

Materials and Methods:

68 men were enrolled with informed consents approved by the institute review board (NTUH-201907031RINA). Penile Doppler ultrasonography (PDUS) parameters, PPG signal, and retrospective historical chart reviews were collected and analyzed. PDUS and PPG were conducted 3 min after injection (PGE1) as mid-erection signals and then for the end-erection signals when patients reached rigid erection. Pearson’s correlation or Spearman’s rank correlation was applied for statistics.

Results:

There were no PDUS confirmed veno-occlusive dysfunction cases in this study. The amplitude of PPG signal decreased at end-erection compared with at mid-erection. The standardized amplitude difference (APD) index was defined as (amplitude at mid-erection - amplitude at end-erection) /  amplitude at mid-erection. APD index is positively correlated with international index of erectile function-5 (IIEF), erection hardness score (EHS), and resistive index (RI) (R=0.289, 0.522, 0.417 with p<.05) and negatively with end-diastolic velocity (EDV) (R=-0.553 with p<.05).

Conclusion:

The PPG signal changes during the process of penile erection and it correlates with IIEF, EHS, RI and EDV. The corresponding penile hemodynamics was speculated. Therefore, it is possible to monitor NPT by oximetry, which provides wearable and low-cost approaches to monitor NPT.