Arterial Oxygen Saturation: A Vital Sign?

ABSTRACT: The physical examination is a key part of a continuum that extends from the history of the present illness to the therapeutic outcome. An understanding of the pathophysiological mechanism behind a physical sign is essential for arriving at the correct diagnosis. Early detection of deteriorating physical/vital signs and their appropriate interpretation is thus the key to achieve correct and timely management. By definition, vital signs are "the signs of life that may be monitored or measured, namely pulse rate, respiratory rate, body temperature, and blood pressure." Vital signs are the simplest, cheapest and probably the most inexpensive information gathered bedside in outpatient or hospitalized patients. The pulse oximeter was introduced in the 1980s. It is an accurate and non-invasive method for the measurement of arterial hemoglobin oxygen saturation (SaO2). Pulse oximetry-based arterial oxygen saturation can be effectively used bedside in in-hospital and ambulatory patients with diagnosed or suspected lung disease. The present pandemic of COVID-19 should be considered as a wake-up call. Articles related to arterial oxygen saturation and its importance as a vital sign in patient care were searched online especially in PubMed. Available studies were studied in full length and data was extracted. Discussion: A. Clinical Utility of Oxygen Saturation Monitoring: There are many studies reporting the clinical applicability and usefulness of pulse oximetry in the early detection of hypoxemic events during intraoperative and postoperative periods. B. Role of clinical expertise accompanied by knowledge of physiology: A diagnostic sign is useful only if it is interpreted accurately and applied appropriately while evaluating a patient. The World Health Organisation also appreciates these facts and published "The WHO Pulse Oximetry Training Manual." Understanding the physiology behind and overcoming limitations of the diagnostic sign by clinical expertise is important. While using pulse oximetry, a clinician needs to keep in mind the sigmoidal nature of the oxygen-Hb dissociation curve. Considering these benefits of SaO2 measurement, there have been several references in the past to consider oxygen saturation as the fifth vital sign. In the present pandemic oxygen saturation i.e., SpO2 (arterial oxygen saturation) measured by pulse oxymeter, has been the single most important warning and prognostic sign be it for households, offices, street vendors, hospitals or governments. Measurement of trends of SaO2 added with respiratory rate will provide clinicians with a holistic overview of respiratory functions and multidimensional conditions associated with hypoxemia.

Racial Disparities in Pulse Oximeter Device Inaccuracy and Estimated Clinical Impact on COVID-19 Treatment Course.

Arterial blood oxygen saturation as measured by pulse oximetry (peripheral oxygen saturation (SpO2)) may be differentially less accurate for people with darker skin pigmentation, which could potentially affect the course of coronavirus disease 2019 (COVID-19) treatment. We analyzed pulse oximeter accuracy and its association with COVID-19 treatment outcomes using electronic health record data from Sutter Health, a large, mixed-payer, integrated health-care delivery system in Northern California. We analyzed 2 cohorts: 1) 43,753 non-Hispanic White (NHW) or non-Hispanic Black/African-American (NHB) adults with concurrent arterial blood gas oxygen saturation/SpO2 measurements taken between January 2020 and February 2021; and 2) 8,735 adults who went to a hospital emergency department with COVID-19 between July 2020 and February 2021. Pulse oximetry systematically overestimated blood oxygenation by 1% more in NHB individuals than in NHW individuals. For people with COVID-19, this was associated with lower admission probability (-3.1 percentage points), dexamethasone treatment (-3.1 percentage points), and supplemental oxygen treatment (-4.5 percentage points), as well as increased time to treatment: 37.2 minutes before dexamethasone initiation and 278.5 minutes before initiation of supplemental oxygen. These results call for additional investigation of pulse oximeters and suggest that current guidelines for development, testing, and calibration of these devices should be revisited, investigated, and revised.

Non-invasive monitoring of carboxyhemoglobin during hyperbaric oxygen therapy.

Introduction: This study aimed to assess the capability of a pulse CO-oximeter to continuously monitor carboxyhemoglobin (COHb) during hyperbaric oxygen (HBO2) therapy. We estimated limits of agreement (LOA) between blood gas analysis and pulse CO-oximeter for COHb during HBO2 therapy in patients suffering from acute CO poisoning. Furthermore, we did a medicotechnical evaluation of the pulse CO-oximeter in hyperbaric conditions. Methods: We conducted a prospective, non-clinical, observational study in which we included n=10 patients with acute CO poisoning referred for HBO2 therapy. We did five repeated measurements of COHb for each patient during the HBO2 therapy. Bland-Altman analysis for multiple observations per individual was used to assess the agreement. The a priori LOA was ±6% for COHb. For the medicotechnical evaluation continuous measurements were obtained throughout each complete HBO2 therapy. The measurements were visually inspected and evaluated. Results: The Bland-Altman analysis showed that the pulse CO-oximeter overestimated COHb by 2.9 % [±1.0%] and the LOA was ±7.3% [±1.8%]. The continuous measurements by pulse CO-oximetry showed fluctuating levels of COHb and summarized saturations reached levels above 100%. Measurements were not affected by changes in pressure. Conclusion: To our knowledge, this study is the first to assess LOA and demonstrate use of a non-invasive method to measure COHb during HBO2 therapy. The pulse CO-oximeter performed within the manufactures reported LOA (±6%) despite hyperbaric conditions and was unaffected by changes in pressure. However, summarized saturations reached levels above 100%.

Effect of opaque wraps for pulse oximeter sensors: randomised cross-over trial.

BACKGROUND: Evidence is lacking as to whether ambient light or phototherapy light could interfere with pulse oximeter performance. METHODS: In this randomised cross-over trial, we recruited neonates of gestation >24 weeks. Consented infants were randomly assigned to either pulse oximeter sensor with opaque wrap or without opaque wrap. Nellcor and Masimo sensors were applied simultaneously to different feet for 10 min of recording. Infants were crossed over to the other intervention for a further 10 min, totalling 20 min recording per infant. Primary outcome was faster acquisition of data with shielding of pulse oximeter sensor as compared with not shielding. RESULTS: A total of 96 babies were recruited. There was no difference in primary outcome of time taken to display valid data between the two groups (opaque wrap: 12.73±3.1 s vs no opaque wrap: 13.16±3.3 s, p=0.27). There was no difference in any of the secondary outcomes (percentage of valid data points, percentage of time saturation below target, and so on) between the two groups in both pulse oximeters. Masimo sensor readings displayed a higher mean oxygen saturation (mean difference of 2.85, p=0.001) and lower percentage of time saturation below 94% (mean difference of -27.8, p=0.001) than Nellcor in both groups. There was no difference in any of the outcomes in babies receiving phototherapy (n=21). CONCLUSION: In this study, shielding the pulse oximeter sensor from ambient light or phototherapy light did not yield faster data acquisition or better data quality. TRIAL REGISTRATION NUMBER: ISRCTN10302534.

Use of overnight pulse oximetry and a type 3 sleep study to titrate hypoglossal nerve stimulation therapy.

NONE: This is a case series of 3 patients with moderate-severe OSA who were PAP-intolerant and underwent implantation of the hypoglossal nerve stimulator. All patients recorded baseline overnight pulse oximetry without the hypoglossal nerve stimulator and at least 1 night at each hypoglossal nerve stimulator setting as they up-titrated the device at home. Because of the impact of the novel coronavirus on sleep laboratories, all patients proceeded directly to type 3 sleep studies performed at a single setting determined by a combination of self-reported improvement and pulse oximetry data.

The Effect of Lotus Position on Dyspnoea Management in Intensive Care Unit.

OBJECTIVE: To determine the effect of lotus position on dyspnea management. METHODS: The case-control study was conducted from June to November 2016 at a training and research hospital in Istanbul, Turkey, and comprised patients with lung disease in an intensive care unit. The patients were divided into an experimental group who were exposed to lotus position for dyspnoea management, while the control group was subjected to Orthopnoeic position. Data was collected using a patient description form, and the Medical Research Council Scale. Respiratory rate, oxygen saturation, heart rate and blood pressure for all subjects were noted. SPSS 22 was used for data analysis. RESULTS: Of the 35 subjects, 17(48.5%) were cases and 18(51.4%) were controls. The overall mean age was 61.48±15.51 years. There was a significant improvement in the intra-group respiratory rate, oxygen saturation, heart rate and systolic blood pressure in both groups (p<0.05). Patients in both groups were similar in their vital signs both before and after the intervention (p>0.05). CONCLUSIONS: Both lotus and Orthopnoeic positions significantly improved dyspnoea-related variables, and lotus position was as effective as Orthopnoeic position.

Nicotine enhances auditory processing in healthy and normal-hearing young adult nonsmokers.

RATIONALE: Electrophysiological studies show that systemic nicotine narrows frequency receptive fields and increases gain in neural responses to characteristic frequency stimuli. We postulated that nicotine enhances related auditory processing in humans. OBJECTIVES: The main hypothesis was that nicotine improves auditory performance. A secondary hypothesis was that the degree of nicotine-induced improvement depends on the individual's baseline performance. METHODS: Young (18-27 years old), normal-hearing nonsmokers received nicotine (Nicorette gum, 6mg) or placebo gum in a single-blind, randomized, crossover design. Subjects performed four experiments involving tone-in-noise detection, temporal gap detection, spectral ripple discrimination, and selective auditory attention before and after treatment. The perceptual differences between posttreatment nicotine and placebo conditions were measured and analyzed as a function of the pre-treatment baseline performance. RESULTS: Nicotine significantly improved performance in the more difficult tasks of tone-in-noise detection and selective attention (effect size = - 0.3) but had no effect on relatively easier tasks of temporal gap detection and spectral ripple discrimination. The two tasks showing significant nicotine effects further showed no baseline-dependent improvement. CONCLUSIONS: Nicotine improves auditory performance in difficult listening situations. The present results support future investigation of nicotine effects in clinical populations with auditory processing deficits or reduced cholinergic activation.

Osteopathic Manipulation Treatment Improves Cerebro-splanchnic Oximetry in Late Preterm Infants.

Background: To evaluate the effectiveness/side-effects of osteopathic manipulation treatment (OMT) performed on the 7th post-natal day, on cerebro-splanchnic oximetry, tissue activation and hemodynamic redistribution in late preterm (LP) infants by using near infrared spectroscopy (NIRS). Methods: Observational pretest-test study consisting in a cohort of 18 LPs who received OMT on the 7th post-natal day. NIRS monitoring was performed at three different time-points: 30 min before (T0), (30 min during (T1) and 30 min after OMT (T2). We evaluated the effects of OMT on the following NIRS parameters: cerebral (c), splanchnic (s) regional oximetry (rSO2), cerebro-splanchnic fractional tissue oxygen extraction (FTOE) and hemodynamic redistribution (CSOR). Results: crSO2 and cFTOE significantly (P < 0.001) improved at T0-T2; srSO2 significantly (P < 0.001) decreased and sFTOE increased at T0-T1. Furthermore, srSO2 and sFTOE significantly improved at T1-T2. Finally, CSOR significantly (P < 0.05) increased at T0-T2. Conclusions: The present data show that OMT enhances cerebro-splanchnic oximetry, tissue activation and hemodynamic redistribution in the absence of any adverse clinical or laboratory pattern. The results indicate the usefulness of further randomized studies in wider populations comparing the effectiveness of OMT with standard rehabilitation programs.

The Effects of Modified Pursed Lips Breathing on Oxygenation Status in Children.

Respiratory disease in children can contribute to damaged alveoli, frailty of respiratory muscles, reduced lung function, impaired gas exchange, and gas retention in the airway. Such condition may lead to disruption of oxygen status. This study aimed to examine the effects of modified pursed lips breathing (PLB) by blowing into a water-filled bottle through a straw and a party whistle on the oxygenation status in children with oxygenation problems. This study used a quasi-experiment method with a pretest-posttest without a control group design approach. The sample consisted of 32 school-aged children and adolescents who were divided into two intervention groups. Group 1 underwent modified PLB by blowing into a water-filled bottle through a straw and Group 2 was provided with modified PLB by blowing a party whistle. The intervention was conducted one time in a day, in a rest time, for 10 min. The results showed that modified PLB by blowing into a water-filled bottle through a straw was more effective in reducing respiratory rate (RR) and improving oxygen saturation (SpO2) than modified PLB by blowing a party whistle. Modified PLB intervention by blowing into a water-filled bottle through a straw improved the oxygenation status of children affected by oxygenation problems. This intervention can be implemented as an independent nursing intervention to improve children's oxygenation status.

Highly sensitive electron paramagnetic resonance nanoradicals for quantitative intracellular tumor oxymetric images.

Purpose: Tumor oxygenation is a critical parameter influencing the efficacy of cancer therapy. Low levels of oxygen in solid tumor have been recognized as an indicator of malignant progression and metastasis, as well as poor response to chemo- and radiation therapy. Being able to measure oxygenation for an individual's tumor would provide doctors with a valuable way of identifying optimal treatments for patients. Methods: Electron paramagnetic resonance imaging (EPRI) in combination with an oxygen-measuring paramagnetic probe was performed to measure tumor oxygenation in vivo. Triarylmethyl (trityl) radical exhibits high specificity, sensitivity, and resolution for quantitative measurement of O2 concentration. However, its in vivo applications in previous studies have been limited by the required high dosage, its short half-life, and poor intracellular permeability. To address these limitations, we developed high-capacity nanoformulated radicals that employed fluorescein isothiocyanate-labeled mesoporous silica nanoparticles (FMSNs) as trityl radical carriers. The high surface area nanostructure and easy surface modification of physiochemical properties of FMSNs enable efficient targeted delivery of highly concentrated, nonself-quenched trityl radicals, protected from environmental degradation and dilution. Results: We successfully designed and synthesized a tumor-targeted nanoplatform as a carrier for trityl. In addition, the nanoformulated trityl does not affect oxygen-sensing capacity by a self-relaxation or broadening effect. The FMSN-trityl exhibited high sensitivity/response to oxygen in the partial oxygen pressure range from 0 to 155 mmHg. Furthermore, MSN-trityl displayed outstanding intracellular oxygen mapping in both in vitro and in vivo animal studies. Conclusion: The highly sensitive nanoformulated trityl spin probe can profile intracellular oxygen distributions of tumor in a real-time and quantitative manner using in vivo EPRI.

Bispectral Analysis to Enhance Oximetry as a Simplified Alternative for Pediatric Sleep Apnea Diagnosis.

This study aims at assessing the bispectral analysis of blood oxygen saturation (SpO2) from nocturnal oximetry to help in pediatric sleep apnea-hypopnea syndrome (SAHS) diagnosis. Recent studies have found excessive redundancy in the SAHS-related information usually extracted from SpO2, while proposing only two features as a reduced set to be used. On the other hand, it has been suggested that SpO2 bispectral analysis is able to provide complementary information to common anthropometric, spectral, and clinical variables. We address these novel findings to assess whether bispectrum provides new non-redundant information to help in SAHS diagnosis. Thus, we use 981 pediatric SpO2 recordings to extract both the reduced set of features recently proposed as well as 9 bispectral features. Then, a feature selection method based on the fast correlationbased filter and bootstrapping is used to assess redundancy among all the features. Finally, the non-redundant ones are used to train a Bayesian multi-layer perceptron neural network (BYMLP) that estimate the apnea-hypopnea index (AHI), which is the diagnostic reference variable. Bispectral phase entropy was found complementary to the two previously recommended features and a BY-MLP model trained with the three of them reached high agreement with actual AHI (intra-class correlation coefficient = 0.889). Estimated AHI also showed high diagnostic ability, reaching 82.1%, 81.9%, and 90.3% accuracies and 0.814, 0.880, and 0.922 area under the receiver-operating characteristics curve for three common AHI thresholds: 1 e/h, 5 e/h, and 10 e/h, respectively. These results suggest that the information extracted from the bispectrum of SpO2 can improve the diagnostic performance of the oximetry test.

Accuracy of Pulse Oximetry Screening for Critical Congenital Heart Defects after Home Birth and Early Postnatal Discharge.

OBJECTIVE: To assess the accuracy of pulse oximetry screening for critical congenital heart defects (CCHDs) in a setting with home births and early discharge after hospital deliveries, by using an adapted protocol fitting the work patterns of community midwives. STUDY DESIGN: Pre- and postductal oxygen saturations (SpO2) were measured ≥1 hour after birth and on day 2 or 3. Screenings were positive if the SpO2 measurement was <90% or if 2 independent measures of pre- and postductal SpO2 were <95% and/or the pre-/postductal difference was >3%. Positive screenings were referred for pediatric assessment. Primary outcomes were sensitivity, specificity, and false-positive rate of pulse oximetry screening for CCHD. Secondary outcome was detection of noncardiac illnesses. RESULTS: The prenatal detection rate of CCHDs was 73%. After we excluded these cases and symptomatic CCHDs presenting immediately after birth, 23 959 newborns were screened. Pulse oximetry screening sensitivity in the remaining cohort was 50.0% (95% CI 23.7-76.3) and specificity was 99.1% (95% CI 99.0-99.2). Pulse oximetry screening was false positive for CCHDs in 221 infants, of whom 61% (134) had noncardiac illnesses, including infections (31) and respiratory pathology (88). Pulse oximetry screening did not detect left-heart obstructive CCHDs. Including cases with prenatally detected CCHDs increased the sensitivity to 70.2% (95% CI 56.0-81.4). CONCLUSION: Pulse oximetry screening adapted for perinatal care in home births and early postdelivery hospital discharge assisted the diagnosis of CCHDs before signs of cardiovascular collapse. High prenatal detection led to a moderate sensitivity of pulse oximetry screening. The screening also detected noncardiac illnesses in 0.6% of all infants, including infections and respiratory morbidity, which led to early recognition and referral for treatment.

Clinical chameleons: an emergency medicine focused review of carbon monoxide poisoning.

Carbon monoxide (CO) is a colorless, odorless gas that is found in the environment, in the home, and in the human body as a normal part of mammalian metabolism. Poisoning from CO, a common exposure, is associated with significant morbidity and mortality if not recognized and treated in a timely manner. This review evaluates the signs and symptoms of CO poisoning, conditions that present similar to CO poisoning, and an approach to the recognition and management for CO poisoning. CO poisoning accounts for thousands of emergency department visits annually. If not promptly recognized and treated, it leads to significant morbidity and mortality. CO poisoning poses a challenge to the emergency physician because it classically presents with non-specific symptoms such as headache, dizziness, nausea, and vomiting. Due to nonspecific presentations, it is easily mistaken for other, more benign diagnoses such as viral infection. The use of specific historical clues such as exposure to non-conventional heat sources or suicide attempts in garages, as well as the use of targeted diagnostic testing with CO-oximetry, can confirm the diagnosis of CO poisoning. Once diagnosed, treatment options range from observation to the use of hyperbaric oxygen. CO poisoning is an elusive diagnosis. This review evaluates the signs and symptoms CO poisoning, common chameleons or mimics, and an approach to management of CO poisoning.

The Effect of Swaddling on Pain, Vital Signs, and Crying Duration during Heel Lance in Newborns.

To determine the effect of swaddling on pain, vital signs, and crying duration during heel lance in the newborn. This was a randomized controlled study of 74 (control: 37, experiment: 37) newborns born between December 2013 and February 2014 at the Ministry of Health Bagcilar Training and Research Hospital. An information form, observation form, and Neonatal Infant Pain Scale were used as data collection tools. Data from the pain scores, peak heart rates, oxygen saturation, total crying time, and duration of the procedure were collected using a video camera. Newborns in the control group underwent routine heel lance, whereas newborns in the experimental group underwent routine heel lance while being swaddled by the researcher. The newborns' pain scores, peak heart rates, oxygen saturation values, and crying durations were evaluated using video recordings made before, during, and 1, 2, and 3 minutes after the procedure. Pain was assessed by a nurse and the researcher. No statistically significant difference was found in the characteristics of the two groups (p > .05). The mean pain scores of swaddled newborns during and after the procedure were lower than the nonswaddled newborns (p < .05). In addition, crying duration of swaddled newborns was found to be shorter than the nonswaddled newborns (p < .05). The average preprocedure peak heart rates of swaddled newborns were higher (p < .05); however, the difference was not significant during and after the procedure (p > .05). Although there was no significant difference in oxygen saturation values before and during the procedure (p > .05), oxygen saturation values of swaddled newborns were higher afterward (p < .05). For this study sample, swaddling was an effective nonpharmacologic method to help reduce pain and crying in an effort to soothe newborns. Although pharmacologic pain management is the gold standard, swaddling can be recommended as a complementary therapy for newborns during painful procedures. Swaddling is a quick and simple nonpharmacologic method that can be used by nurses to help reduce heel stick pain in newborns.

A novel method to precisely detect apnea and hypopnea events by airflow and oximetry signals.

Sleep apnea hypopnea syndrome (SAHS) affects people's quality of life. The apnea hypopnea index (AHI) is the key indicator for diagnosing SAHS. The determination of the AHI is based on accurate detection of apnea and hypopnea events. This paper provides a novel method to detect apnea and hypopnea events based on the respiratory nasal airflow signal and the oximetry signal. The method uses sliding window and short time slice methods to eliminate systematic and sporadic noise of the airflow signal for improving the detection precision. Using this algorithm, the sleep data of 30 subjects from the Huaxi Sleep Center of Sichuan University (HSCSU) and the Teaching Hospital of Chengdu University of Traditional Chinese Medicine (THCUTCM) were auto-analyzed for detecting the apnea and hypopnea events. The total predicted apnea and hypopnea events were 8470. By manual investigation, the sensitivity and positive predictive value (PPV) of detecting apnea and hypopnea events were 97.6% and 95.7%, respectively. The sleep data of 28 subjects form HSCSU were auto-diagnosed SAHS according to the AHI. The sensitivity and PPV were 92.3% and 92.3%, respectively. This is an effective and precise method to diagnose SAHS. It can fit the home care SAHS screener.

Use of near-infrared spectroscopy (NIRS) in cerebral tissue oxygenation monitoring in neonates.

Near-infrared spectroscopy (NIRS) is a technology capable of non-invasive, continuous measuring of regional tissue oxygen saturation (StO2). StO2 represents a state of hemodynamic stability, which is influenced by many factors. Extensive research has been done in the field of measuring StO2 of various organs. The current clinical availability of several NIRS-based devices reflects an important development in prevention, detection and correction of discrepancy in oxygen delivery to the brain and vital organs. Managing cerebral ischemia remains a significant issue in the neonatal intensive care units (NICU). Cerebral tissue oxygenation (cStO2) and cerebral fractional tissue extraction (cFTOE) are reported in a large number of clinical studies. This review provides a summary of the concept of function, current variability of NIRS-based devices used in neonatology, clinical applications in continuous cStO2 monitoring, limitations, disadvantages, and the potential of current technology.

Combined spiroergometry and 31 P-MRS of human calf muscle during high-intensity exercise.

Simultaneous measurements of pulmonary oxygen consumption (VO2 ), carbon dioxide exhalation (VCO2 ) and phosphorus magnetic resonance spectroscopy (31 P-MRS) are valuable in physiological studies to evaluate muscle metabolism during specific loads. Therefore, the aim of this study was to adapt a commercially available spirometric device to enable measurements of VO2 and VCO2 whilst simultaneously performing 31 P-MRS at 3 T. Volunteers performed intense plantar flexion of their right calf muscle inside the MR scanner against a pneumatic MR-compatible pedal ergometer. The use of a non-magnetic pneumotachograph and extension of the sampling line from 3 m to 5 m to place the spirometric device outside the MR scanner room did not affect adversely the measurements of VO2 and VCO2 . Response and delay times increased, on average, by at most 0.05 s and 0.79 s, respectively. Overall, we were able to demonstrate a feasible ventilation response (VO2 = 1.05 ± 0.31 L/min; VCO2 = 1.11 ± 0.33 L/min) during the exercise of a single calf muscle, as well as a good correlation between local energy metabolism and muscular acidification (τPCr fast and pH; R2 = 0.73, p < 0.005) and global respiration (τPCr fast and VO2 ; R2  = 0.55, p = 0.01). This provides improved insights into aerobic and anaerobic energy supply during strong muscular performances.

Effects of Antioxidant Supplements (BioPQQ™) on Cerebral Blood Flow and Oxygen Metabolism in the Prefrontal Cortex.

Pyrroloquinoline quinone (PQQ) is a quinone compound originally identified in methanol-utilizing bacteria and is a cofactor for redox enzymes. At the Meeting of the International Society on Oxygen Transport to Tissue (ISOTT) 2014, we reported that PQQ disodium salt (BioPQQ™) improved cognitive function in humans, as assessed by the Stroop test. However, the physiological mechanism of PQQ remains unclear. In the present study, we measured regional cerebral blood flow (rCBF) and oxygen metabolism in prefrontal cortex (PFC), before and after administration of PQQ, using time-resolved near-infrared spectroscopy (tNIRS). A total of 20 healthy subjects between 50 and 70 years of age were administered BioPQQ™ (20 mg) or placebo orally once daily for 12 weeks. Hemoglobin (Hb) concentration and absolute tissue oxygen saturation (SO2) in the bilateral PFC were evaluated under resting conditions using tNIRS. We found that baseline concentrations of hemoglobin and total hemoglobin in the right PFC significantly increased after administration of PQQ (p < 0.05). In addition, decreases in SO2 level in the PFC were more pronounced in the PQQ group than in the placebo group (p < 0.05). These results suggest that PQQ causes increased activity in the right PFC associated with increases in rCBF and oxygen metabolism, resulting in enhanced cognitive function.