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Objective Patients with chronic respiratory failure requiring long-term oxygen therapy (LTOT) are at a risk of CO2 retention because of excessive oxygen administration. The CapnoEye™ is a novel portable capnometer that can measure end-tidal CO2 (EtCO2) noninvasively. This retrospective study evaluated the usefulness of this device. Methods EtCO2 was measured using the CapnoEye™. The EtCO2 and partial pressure of venous carbon dioxide (PvCO2) were analyzed, and other clinical data were assessed. Patients Sixty-one consecutive patients with chronic respiratory failure receiving LTOT in the outpatient department at the Japanese Red Cross Medical Center between July 2017 and March 2018 were retrospectively reviewed. Results There was a significant correlation between EtCO2 and PvCO2 (r=0.63) in the total study population as well as in the COPD group (r=0.65) and ILD group (r=0.67). The PvCO2 and EtCO2 gradient was correlated with only the body mass index in a multivariate analysis (p=0.0235). The EtCO2 levels on the day of admission were significantly higher than those in the same patients when they were in a stable condition (p=0.0049). There was a significant correlation between ΔEtCO2 and ΔPvCO2 (r=0.4). A receiver-operating characteristic curve analysis revealed the optimal cut-off EtCO2 value for identifying hypercapnia to be 34 mmHg (p=0.0005). Conclusion The evaluation of EtCO2 by the CapnoEye™ was useful for predicting PvCO2. The body mass index was identified as a possible predictor of the PvCO2 and EtCO2 gradient. An increase in EtCO2 may indicate deterioration of the respiratory status in patients with chronic respiratory failure receiving LTOT.

The cellular activation of the NLRP3 inflammasome is spatiotemporally orchestrated by various organelles, but whether lysosomes contribute to this process remains unclear. Here, we show the vital role of the lysosomal membrane-tethered Ragulator complex in NLRP3 inflammasome activation. Deficiency of Lamtor1, an essential component of the Ragulator complex, abrogated NLRP3 inflammasome activation in murine macrophages and human monocytic cells. Myeloid-specific Lamtor1-deficient mice showed marked attenuation of NLRP3-associated inflammatory disease severity, including LPS-induced sepsis, alum-induced peritonitis, and monosodium urate (MSU)-induced arthritis. Mechanistically, Lamtor1 interacted with both NLRP3 and histone deacetylase 6 (HDAC6). HDAC6 enhances the interaction between Lamtor1 and NLRP3, resulting in NLRP3 inflammasome activation. DL-all-rac-α-tocopherol, a synthetic form of vitamin E, inhibited the Lamtor1-HDAC6 interaction, resulting in diminished NLRP3 inflammasome activation. Further, DL-all-rac-α-tocopherol alleviated acute gouty arthritis and MSU-induced peritonitis. These results provide novel insights into the role of lysosomes in the activation of NLRP3 inflammasomes by the Ragulator complex.