Assessment of cerebral blood flow in patients with multiple chemical sensitivity using near-infrared spectroscopy—recovery after olfactory stimulation: a case–control study

Azuma, Kenichi; Uchiyama, Iwao; Tanigawa, Mari; Bamba, Ikuko; Azuma, Michiyo; Takano, Hirohisa; Yoshikawa, Toshikazu; Sakabe, Kou

doi:10.1007/s12199-015-0448-4

Cited by 16 publications

(25 citation statements)

References 49 publications

(65 reference statements)

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“…This approach is based on the assumption that changes in flow are proportional to changes in velocity only if the diameter of the middle cerebral artery remains constant. Also, the blood flow velocity in the middle cerebral artery can reflect global CBF rather than local CBF [22,23]. On the other hand, a previous study reported that the diameter of the middle cerebral artery can change over a wide range of ETCO 2 (approximately 23-46 Torr) [24].…”

Section: Discussionmentioning

confidence: 99%

The relationship between widespread changes in gravity and cerebral blood flow

Ogawa

Yanagida

Ueda

et al. 2016

Environ Health Prev Med

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Objectives We investigated the dose-effect relationship between wide changes in gravity from 0 to 2.0 Gz (D0.5 Gz) and cerebral blood flow (CBF), to test our hypothesis that CBF has a linear relationship with levels of gravity. Subjects and methods Ten healthy seated men were exposed to 0, 0.5, 1.0, 1.5, and 2.0 Gz for 21 min, by using a tilt chair and a short-arm human centrifuge. Steady-state CBF velocity (CBFV) in the middle cerebral artery by transcranial Doppler ultrasonography, mean arterial pressure (MAP) at the heart level (MAP Heart ), heart rate, stroke volume, cardiac output and respiratory conditions were obtained for the last 6 min at each gravity level. Then, MAP in the middle cerebral artery (MAP MCA ), reflecting cerebral perfusion pressure, was estimated. Results Steady-state CBFV decreased stepwise from 0.5 to 2.0 Gz. Steady-state heart rate, stroke volume, estimated MAP MCA and end-tidal carbon dioxide pressure (ETCO 2 ) also changed stepwise from hypogravity to hypergravity. On the other hand, steady-state MAP Heart and cardiac output did not change significantly. Steady-state CBFV positively and linearly correlated with estimated MAP MCA and ETCO 2 in most subjects. ConclusionThe present study demonstrated stepwise gravity-induced changes in steady-state CBFV from 0.5 to 2.0 Gz despite unchanged steady-state MAP Heart . The combined effects of reduced MAP MCA and ETCO 2 likely led to stepwise decreases in CBFV. We caution that a mild increase in gravity from 0 to 2.0 Gz reduces CBF, even if arterial blood pressure at the heart level is maintained.

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Section: Discussionmentioning

confidence: 99%

The relationship between widespread changes in gravity and cerebral blood flow

Ogawa

Yanagida

Ueda

et al. 2016

Environ Health Prev Med

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“…These results also suggest that past strong exposure activates the PFC during olfactory stimulation in patients with MCS, and strong OFC activation persists after stimulus exposure [17]. Thus, the chemical-sensitive state of patients with MCS might remain due to repeated daily exposure, eventually leading to intolerance to odorous chemicals [17]. …”

Section: Introductionmentioning

confidence: 97%

“…In particular, patients with MCS were demonstrated to peculiarly react to sensory stimuli, with activation of brain areas connected with motivational and emotional processing of the information. We also demonstrated activation in the prefrontal cortex (PFC) during olfactory stimulation [16] and in the orbitofrontal cortex (OFC) [17] following olfactory stimulation in patients with MCS using several different odorants using near-infrared spectroscopy (NIRS) imaging. These results suggest that prefrontal information processing associated with odor-processing neuronal circuits and memory and cognition processes from past hazardous chemical exposure play significant roles in the pathology of MCS [16,17].…”

Section: Introductionmentioning

confidence: 99%

“…We also demonstrated activation in the prefrontal cortex (PFC) during olfactory stimulation [16] and in the orbitofrontal cortex (OFC) [17] following olfactory stimulation in patients with MCS using several different odorants using near-infrared spectroscopy (NIRS) imaging. These results suggest that prefrontal information processing associated with odor-processing neuronal circuits and memory and cognition processes from past hazardous chemical exposure play significant roles in the pathology of MCS [16,17]. These results also suggest that past strong exposure activates the PFC during olfactory stimulation in patients with MCS, and strong OFC activation persists after stimulus exposure [17].…”

Section: Introductionmentioning

confidence: 99%

“…These results suggest that prefrontal information processing associated with odor-processing neuronal circuits and memory and cognition processes from past hazardous chemical exposure play significant roles in the pathology of MCS [16,17]. These results also suggest that past strong exposure activates the PFC during olfactory stimulation in patients with MCS, and strong OFC activation persists after stimulus exposure [17]. Thus, the chemical-sensitive state of patients with MCS might remain due to repeated daily exposure, eventually leading to intolerance to odorous chemicals [17].…”

Section: Introductionmentioning

confidence: 99%

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Association of Odor Thresholds and Responses in Cerebral Blood Flow of the Prefrontal Area during Olfactory Stimulation in Patients with Multiple Chemical Sensitivity

Azuma¹,

Uchiyama²,

Tanigawa³

et al. 2016

PLoS ONE

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Multiple chemical sensitivity (MCS) is a disorder characterized by nonspecific and recurrent symptoms from various organ systems associated with exposure to low levels of chemicals. Patients with MCS process odors differently than controls do. Previously, we suggested that this odor processing was associated with increased regional cerebral blood flow (rCBF) in the prefrontal area during olfactory stimulation using near-infrared spectroscopic (NIRS) imaging. The aim of this study was to investigate the association of odor thresholds and changes in rCBF during olfactory stimulation at odor threshold levels in patients with MCS. We investigated changes in the prefrontal area using NIRS imaging and a T&T olfactometer during olfactory stimulation with two different odorants (sweet and fecal) at three concentrations (zero, odor recognition threshold, and normal perceived odor level) in 10 patients with MCS and six controls. The T&T olfactometer threshold test and subjective assessment of irritating and hedonic odors were also performed. The results indicated that the scores for both unpleasant and pungent odors were significantly higher for those for sweet odors at the normal perceived level in patients with MCS than in controls. The brain responses at the recognition threshold (fecal odor) and normal perceived levels (sweet and fecal odors) were stronger in patients with MCS than in controls. However, significant differences in the odor detection and recognition thresholds and odor intensity score between the two groups were not observed. These brain responses may involve cognitive and memory processing systems during past exposure to chemicals. Further research regarding the cognitive features of sensory perception and memory due to past exposure to chemicals and their associations with MCS symptoms is needed.

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Exposure limits for indoor volatile substances concerning the general population: The role of population-based differences in sensory irritation of the eyes and airways for assessment factors

Kleinbeck,

Wolkoff

2024

Arch Toxicol

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Assessment factors (AFs) are essential in the derivation of occupational exposure limits (OELs) and indoor air quality guidelines. The factors shall accommodate differences in sensitivity between subgroups, i.e., workers, healthy and sick people, and occupational exposure versus life-long exposure for the general population. Derivation of AFs itself is based on empirical knowledge from human and animal exposure studies with immanent uncertainty in the empirical evidence due to knowledge gaps and experimental reliability. Sensory irritation in the eyes and airways constitute about 30–40% of OELs and is an abundant symptom in non-industrial buildings characterizing the indoor air quality and general health. Intraspecies differences between subgroups of the general population should be quantified for the proposal of more ‘empirical’ based AFs. In this review, we focus on sensitivity differences in sensory irritation about gender, age, health status, and vulnerability in people, based solely on human exposure studies. Females are more sensitive to sensory irritation than males for few volatile substances. Older people appear less sensitive than younger ones. However, impaired defense mechanisms may increase vulnerability in the long term. Empirical evidence of sensory irritation in children is rare and limited to children down to the age of six years. Studies of the nervous system in children compared to adults suggest a higher sensitivity in children; however, some defense mechanisms are more efficient in children than in adults. Usually, exposure studies are performed with healthy subjects. Exposure studies with sick people are not representative due to the deselection of subjects with moderate or severe eye or airway diseases, which likely underestimates the sensitivity of the group of people with diseases. Psychological characterization like personality factors shows that concentrations of volatile substances far below their sensory irritation thresholds may influence the sensitivity, in part biased by odor perception. Thus, the protection of people with extreme personality traits is not feasible by an AF and other mitigation strategies are required. The available empirical evidence comprising age, lifestyle, and health supports an AF of not greater than up to 2 for sensory irritation. Further, general AFs are discouraged for derivation, rather substance-specific derivation of AFs is recommended based on the risk assessment of empirical data, deposition in the airways depending on the substance’s water solubility and compensating for knowledge and experimental gaps. Modeling of sensory irritation would be a better ‘empirical’ starting point for derivation of AFs for children, older, and sick people, as human exposure studies are not possible (due to ethical reasons) or not generalizable (due to self-selection). Dedicated AFs may be derived for environments where dry air, high room temperature, and visually demanding tasks aggravate the eyes or airways than for places in which the workload is balanced, while indoor playgrounds might need other AFs due to physical workload and affected groups of the general population.

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Assessment of cerebral blood flow in patients with multiple chemical sensitivity using near-infrared spectroscopy—recovery after olfactory stimulation: a case–control study

Cited by 16 publications

References 49 publications

The relationship between widespread changes in gravity and cerebral blood flow

The relationship between widespread changes in gravity and cerebral blood flow

Association of Odor Thresholds and Responses in Cerebral Blood Flow of the Prefrontal Area during Olfactory Stimulation in Patients with Multiple Chemical Sensitivity

Exposure limits for indoor volatile substances concerning the general population: The role of population-based differences in sensory irritation of the eyes and airways for assessment factors

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