Fine bubbles (FBs) have attracted significant attention in several research fields. Although some reports have argued that FB dispersion is useful as an oxygen (gas) carrier, only a few reports have examined its properties as an oxygen carrier using experimental data. As one of the reasons for this, there are no standard methods for measuring the oxygen content in FB dispersions. Conventional oxygen measurement methods have certain drawbacks in accuracy or speed; thus, it is difficult to use oxygen content as the primary outcome. In this study, we introduce a Clark-type polarographic oxygen electrode device (OXYG1-PLUS) for oxygen measurement, allowing the dilution of FB dispersion without the influence of ambient air and the adhesion of FBs on the electrode surface due to its special shape. First, the accuracy of our dilution method was evaluated using pure water as a sample, and it was confirmed that our method could measure with an accuracy of ±0.5 mg/L from the results with conventional dissolved oxygen meters. Second, the oxygen content in FB dispersion was evaluated with our method and a chemical titration method (Winkler's method), and it was found that our method could measure the oxygen content in FB dispersions quantitively. This method satisfies the easiness (4 steps) and quickness (within 8 min) for a wide range of oxygen contents (0 to 332 mg/L, theoretical range) with low coefficient variation (< 4.7%) and requires a small sample volume (50-500 μL); thus, it is a useful method for measuring the oxygen in FB dispersions.

<title>Abstract</title>
Severe respiratory disorder induced by pulmonary inflammation is one of the causes of acute respiratory distress syndrome, which still has high mortality. It is crucial to remove causative substances and inflammatory mediators early in order to inhibit the progression of pulmonary inflammation. Total alveolar lavage (TAL) may avert the inflammatory response by eliminating causative substances in certain inflammatory lung diseases. We developed an efficient TAL system and examined the efficacy of short-term TAL treatment performed for acute lung injury models of rats. In the first experiment with a severe lung injury model, 15 rats were divided into 3 groups: sham group, mechanical gas ventilation (MGV) treatment group, and TAL treatment group. The treatments were conducted for 5 min, 20 min after the provocation of inflammation. Two days after treatment, the TAL and MGV treatment groups exhibited significant differences in blood oxygen levels, mean arterial pressure, weight-loss ratio, and inflammatory cytokine levels in the lungs. In contrast, almost no differences were observed between the TAL treatment and sham groups. In the second experiment with a lethal lung injury model, the TAL treatment dramatically improved the survival rate of the rats compared to the MGV treatment groups (<italic>p</italic> = 0.0079). Histopathological analysis confirmed pronounced differences in neutrophil accumulation and thickening of the interstitial membrane between the TAL and MGV treatment groups in both experiments. These results indicate that as little as 5 min of TAL treatment can protect rats from acute lung injury by removing causative substances from the lungs.

In humans, the inhalation of warm steam has been reported to decrease the respiratory rate. However, the effects of warm steam inhalation on sleep have not been studied closely. This study aimed to examine the effects of warm steam inhalation before bedtime on subsequent sleep quality. The participants included 17 adult men with mild sleep difficulties and anxiety. All experiments were conducted in the participants’ homes. The participants were instructed to wear a warm steam-generating mask or sham mask over the nose and mouth for 15 minutes immediately before habitual bedtime and were then allowed to sleep until their habitual waking time. The functional mask provided approximately 600 mg of steam for 10 minutes and maintained an interior temperature of 38–40°C for 15 minutes. We evaluated the participants’ electrocardiograms and subjective moods while wearing the mask. During sleep, electroencephalograms (EEGs) were recorded using a single-channel portable device. In the morning, each participant was instructed to report their sleep details subjectively using a visual analog scale. At bedtime, the subjects’ subjective apprehension of the next day was reduced significantly under steam inhalation, compared with the sham condition. Compared to the sham condition, steam inhalation before bedtime was associated with a higher EEG delta power density during the first third of sleep episodes and better subjective sleep quality in the morning. These results suggest that safe and easy inhalation of warm steam via a steam-generating mask improves psychological relaxation and sleep.

Micro/nano-bubbles are practical nanomaterials designed to increase the gas content in liquids. We attempted to use oxygen micro/nano-bubble dispersions as an oxygen-rich liquid as a means for total liquid ventilation. To determine the oxygen content in the bubble dispersion, a new method based on a spectrophotometric change between oxy- and deoxy-hemoglobin was established. The oxygen micro/nano-bubble dispersion was supplied to an experimental total ventilation liquid in anesthetic rats. Though the amount of dissolving oxygen was as low as 6 mg/L in physiological saline, the oxygen content in the oxygen micro/nano-bubble dispersion was increased to 45 mg/L. The positive correlation between the oxygen content and the life-saving time under liquid ventilation clearly indicates that the life-saving time is prolonged by increasing the oxygen content in the oxygen micro/nano-bubble dispersion. This is the first report indicating that the oxygen micro/nano-bubbles containing a sufficient amount of oxygen are useful in producing oxygen-rich liquid for the process of liquid ventilation.