Tribute to Dr. Takuo Aoyagi, inventor of pulse oximetry.

INTRODUCTION: Dr. Takuo Aoyagi invented pulse oximetry in 1974. Pulse oximeters are widely used worldwide, most recently making headlines during the COVID-19 pandemic. Dr. Aoyagi passed away on April 18, 2020, aware of the significance of his invention, but still actively searching for the theory that would take his invention to new heights. METHOD: Many people who knew Dr. Aoyagi, or knew of him and his invention, agreed to participate in this tribute to his work. The authors, from Japan and around the world, represent all aspects of the development of medical devices, including scientists and engineers, clinicians, academics, business people, and clinical practitioners. RESULTS: While the idea of pulse oximetry originated in Japan, device development lagged in Japan due to a lack of business, clinical, and academic interest. Awareness of the importance of anesthesia safety in the US, due to academic foresight and media attention, in combination with excellence in technological innovation, led to widespread use of pulse oximetry around the world. CONCLUSION: Dr. Aoyagi's final wish was to find a theory of pulse oximetry. We hope this tribute to him and his invention will inspire a new generation of scientists, clinicians, and related organizations to secure the foundation of the theory.

Age and sex-related differences in dose-dependent hemodynamic response to landiolol hydrochloride during general anesthesia.

OBJECTIVE: Landiolol hydrochloride is a new ultra-short-acting beta(1)-adrenergic receptor blocking agent that is used for patients with tachycardia during general anesthesia. The hemodynamic response to a beta-adrenergic receptor blocking agent is generally dependent on the subject. In the present investigation we investigated the effects of age and sex on the hemodynamic response to different doses of landiolol. METHODS: Following a persistence of tachycardia for more than 1 min, landiolol was infused at 0.03125, 0.0625 and 0.125 mg kg(-1) min(-1) for 1 min followed by 0.01, 0.02 and 0.04 mg kg(-1)min(-1) for 10 min in groups L, M and H, respectively. Heart rate (HR), systolic (sBP) and diastolic blood pressure (dBP) were recorded each minute during the procedure. The respective changes were evaluated using logistic analysis with the equation Y(t) = p + (q - p)/[1 + exp {4m/(q - p))(k - t)}], where p, q, m and k indicate the upper asymptote, lower asymptote, maximum slope and time at the maximum slope. RESULTS: Parameters q and k for HR in group H were smaller than those in group L, whereas the parameters for sBP and dBP were unchanged among the three groups. Parameter q for HR in group H decreased with age of the patient. There was no significant difference in the landiolol-induced change in HR between males and females. CONCLUSION: The hemodynamic response to landiolol is reliably modeled by the logistic function, especially in terms of HR. Landiolol causes a rapid and dose-dependent decrease in HR, whereas landiolol-induced changes in sBP and dBP are independent of dose. The landiolol-induced decrease in HR becomes larger with aging, but shows no sex difference. The logistic model may be useful for studying hemodynamic responses to landiolol based on age and sex differences, and may allow development of an improved monitoring system. IMPLICATION STATEMENT: The logistic function reliably represents the hemodynamic responses to landiolol. Landiolol reduces HR rapidly and in a dose-dependent manner whereas landiolol-induced changes in sBP and dBP are independent of dose. A larger decrease in HR is caused by landiolol in elderly patients, but there is no sex difference in the landiolol-induced change in HR.

Age and sex analyses of out-of-hospital cardiac arrest in Osaka, Japan.

OBJECTIVE: To determine effective interventional targets for out-of-hospital cardiac arrests by analyzing the distribution characteristics of arrest patients according to age and sex with special emphasis on ventricular fibrillation (VF). METHODS: All patients who suffered out-of-hospital cardiac arrest in Osaka Prefecture, Japan during 2 years, were prospectively recorded based on the Utstein style. The number and the incidence rate of cases of arrest, witnessed arrest, and witnessed VF were evaluated according to age and sex. The percentage of resuscitation attempts in arrest cases was also calculated. RESULTS: We recorded 10139 consecutive out-of-hospital cardiac arrest cases. Resuscitation was attempted in 97.0% of 10139 and showed no significant differences by age and sex. The incidence rate of cardiac arrests increased exponentially with age. Men showed a significantly higher incidence rate of out-of-hospital arrests than women in every age group. Most of the witnessed VF cases showed cardiac a aetiology and were predominantly observed in men in their 50s, 60s and 70s. The incidence rates of witnessed VF were also greater in them. CONCLUSION: Our study provides evidence that there are significant age and sex related epidemiological differences in cardiac arrests and we need to understand them better. Strategies that focus on high yielded patients, those in witnessed VF, should be pursued. These efforts should be expected to yield sex and age related differences in survivors.

Changes of electroencephalographic bicoherence during isoflurane anesthesia combined with epidural anesthesia.

BACKGROUND: The authors previously reported that, during isoflurane anesthesia, electroencephalographic bicoherence values changed in a fairly restricted region of frequency versus frequency space. The aim of the current study was to clarify the relation between electroencephalographic bicoherence and the isoflurane concentration. METHODS: Thirty elective abdominal surgery patients (male and female, aged 34-77 yr, American Society of Anesthesiologists physical status I-II) were enrolled. After electroencephalogram recording with patients in an awake state, anesthesia was induced with 3 mg/kg thiopental and maintained with oxygen and isoflurane. Continuous epidural anesthesia with 80-100 mg/kg 1% lidocaine was also administered. Using software they developed, the authors continuously recorded the FP1-A1 lead of the electroencephalographic signal and expired isoflurane concentration to an IBM-PC compatible computer. After confirming the steady state of each isoflurane (end-tidal concentration at 0.3, 0.5, 0.7, 0.9, 1.1, 1.3, and 1.5%), electroencephalographic bicoherence values were calculated. RESULTS: In a light anesthetic state, electroencephalographic bicoherence values were low (generally < or = 15.0%). At increased concentrations of isoflurane, two peaks of electroencephalographic bicoherence emerged along the diagonal line (f1=f2). The peak emerged at around 4.0 Hz and grew higher as isoflurane concentration increased until it reached a plateau (43.8 +/- 3.5%, mean +/- SD) at isoflurane 0.9%. The other peak, at about 10.0 Hz, also became significantly higher and reached a plateau (32.6 +/- 9.2%) at isoflurane 0.9%; at isoflurane 1.3%, however, this peak slightly decreased. CONCLUSION: Changes in the height of two electroencephalographic bicoherence peaks correlated well with isoflurane concentration.

Effects of four volatile anesthesics on postanesthetic ventilation: a comparison of halothane, enflurane, isoflurane, and sevoflurane.

To investigate the effects of four volatile anesthetics (halothane, enflurane, isoflurane, and sevoflurane) on postanesthetic ventilation and levels of consciousness, we enrolled 24 patients undergoing tympanoplasty in this study. Anesthesia was maintained with 67% nitrous oxide and one of four volatile anesthetics. We measured end-tidal carbon dioxide concentration (CETco2), minute volume ([Formula: see text]) and respiratory rate (RR), and determined the volatile anesthetic concentration in whole arterial blood (CBAnesth) and arterial carbon dioxide tension (Paco2) at 20 min and 2h after tracheal extubation. We also observed the level of consciousness (awake, drowsy, and asleep) before the measurement. Ventilatory variables were similar among the four groups at 20 min, although the ratio of volatile anesthetic concentration in the alveoli to the minimum alveolar concentration (MAC) (CAAnesth/MAC ratio) calculated from CBAnesth in the halothane group was twice those in the other groups. In the halothane group, Paco2 was significantly higher, and[Formula: see text] and RR were significantly lower compared with the isoflurane and sevoflurane groups at 2h. Halothane tended to prolong the recovery of levels of consciousness. We conclude that isoflurane and sevoflurane provide clinical advantages over halothane on postanesthetic ventilation and recovery of levels of consciousness.

Responses of interleukin-6 and tumor necrosis factor during and after cardiac surgery undergoing cardiopulmonary bypass and pancreatoduodenectomy.

To evaluate the effect of cardiopulmonary bypass on immunological function, we measured interleukin-6 (IL-6) and tumor necrosis factor (TNF) in 12 patients undergoing cardiac surgery during and after cardiopulmonary bypass, and in 10 patients with pancreatoduodenectomy. Plasma IL-6 levels were determined using the Human Interleukin 6 ELISA Kit, and TNF levels were determined using a highly sensitive sandwich enzyme immunoassay. In patients with cardiac surgery, plasma levels of IL-6 and TNF increased during cardiopulmonary bypass, and in patients with pancreatoduodenectomy, IL-6 and TNF levels significantly increased at the end of intraabdominal manipulation. These results suggest that endotoxin may have activated the immune system and stimulated cytokine production after pancreatoduodenectomy and during bypass.