In the field of respiratory clinical practice, the importance of measuring carbon dioxide (CO₂) concentrations cannot be overemphasized. Within the body, assessment of the arterial partial pressure of CO₂ (PaCO₂) has been the gold standard for many decades. Non-invasive assessments are usually predicated on the measurement of CO₂ concentrations in the air, usually using an infrared analyzer, and these data are clearly important regarding climate changes as well as regulations of air quality in buildings to ascertain adequate ventilation. Measurements of CO₂ production with oxygen consumption yield important indices such as the respiratory quotient and estimates of energy expenditure, which may be used for further investigation in the various fields of metabolism, obesity, sleep disorders, and lifestyle-related issues. Measures of PaCO₂ are nowadays performed using the Severinghaus electrode in arterial blood or in arterialized capillary blood, while the same electrode system has been modified to enable relatively accurate non-invasive monitoring of the transcutaneous partial pressure of CO₂ (PtcCO₂). PtcCO₂ monitoring during sleep can be helpful for evaluating sleep apnea syndrome, particularly in children. End-tidal PCO₂ is inferior to PtcCO₂ as far as accuracy, but it provides breath-by-breath estimates of respiratory gas exchange, while PtcCO₂ reflects temporal trends in alveolar ventilation. The frequency of monitoring end-tidal PCO₂ has markedly increased in light of its multiple applications (e.g., verify endotracheal intubation, anesthesia or mechanical ventilation, exercise testing, respiratory patterning during sleep, etc.).

Background: Recently, the concept of respiratory sarcopenia has been advocated, but evidence is lacking regarding which respiratory parameters are appropriate indicators. Therefore, we investigated the association between sarcopenia, respiratory function, and respiratory muscle strength to identify the most appropriate parameters for respiratory sarcopenia.Methods: We included 124 older adults (67 men, 57 women; average age 77.2 ± 8.3 years) requiring long-term care/support who underwent Day Care for rehabilitation. Handgrip strength, usual gait speed, and skeletal muscle mass were measured using bioelectrical impedance analysis. Participants were then diagnosed with sarcopenia using the algorithm of the Asian Working Group for Sarcopenia 2019. Parameters of respiratory function (forced vital capacity, forced expiratory volume in one second [FEV1.0], FEV1.0%, and peak expiratory flow rate) and respiratory muscle strength (maximal expiratory pressure [MEP] and maximal inspiratory pressure) were also measured according to American Thoracic Society guidelines. Respiratory parameters significantly related to sarcopenia were identified using binomial logistic regression and receiver operating characteristic analyses.Results: Seventy-seven participants were classified as having sarcopenia. Binomial logistic regression analysis showed that MEP was the only respiratory parameter significantly associated with sarcopenia. The cut-off MEP value for predicting sarcopenia was 47.0 cmH₂0 for men and 40.9 cmH₂0 for women.Conclusions: The most appropriate parameter for assessing respiratory sarcopenia may be MEP, which is an indicator of expiratory muscle strength, rather than FVC, MIP, or PEFR, as suggested in previous studies. Measuring MEP is simpler than measuring respiratory function parameters. Moreover, it is expected to have clinical applications such as respiratory sarcopenia screening.

Background: Among community-dwelling older adults who require long-term care and use outpatient rehabilitation services, we aimed to examine the characteristics of patients who discontinued using outpatient rehabilitation services to prevent exposure to COVID-19 and the effects of this discontinuation on patient frailty. Methods: Participants were 119 older adults (69 males, 50 females; average age 77.3 ± 8.3 years) requiring long-term care who used outpatient rehabilitation services. Our outpatient rehabilitation service involved day care for older adults undergoing rehabilitation including pick-up and drop-off services under the long-term care insurance system. They were divided into two groups: participants who discontinued using outpatient rehabilitation services and participants who continued their use. To find the factors associated with this discontinuation, binomial logistic regression analysis was performed, in which the following independent variables were used: gender, age, height, weight, long-term care level, grip strength, and normal walking speed. Frailty status was investigated in April 2020 and again in September 2020 through interviews and telephone surveys utilizing the Frailty Screening Index. Results: Women and normal walking speed were independent factors associated with the discontinuation of outpatient rehabilitation due to COVID-19. According to the results of the Frailty Screening Index, similar tendencies were exhibited in both April and September. The discontinued group indicated that they were getting less exercise and having stronger feelings of fatigue than the continuing group. Conclusions: The findings are in accordance with other studies indicating that women are more likely to employ prevention measures against COVID-19, as seen among the community-dwelling older adults requiring long-term care who used outpatient rehabilitation services. People with higher levels of physical function were also likely to refrain from using outpatient rehabilitation services. Results further suggested that the discontinued group had more frailty-related factors (i.e., low physical activity and strong exhaustion) than the continuing group.

This study investigated the relationship between eye frailty and physical, social, and psychological/cognitive weaknesses among older adults in Japan. The participants were 192 community-dwelling older adult women. We measured handgrip strength, walking speed, and skeletal muscle mass; additionally, their physical, social, and psychological/cognitive frailties were surveyed using questionnaires. Eye frailty self-checks were used to assess eye frailty. Exploratory and confirmatory factor analyses were employed to verify the validity of the eye frailty self-checks. Eye frailty prevalence and related factors were investigated by conducting a binomial logistic regression analysis, with eye frailty as the dependent variable. The factor analysis results showed that a model could be constructed with the two factors of visual acuity or contrast and visual field. The model’s goodness of fit was acceptable, supporting the validity of the self-checking construct. The Kihon checklist was the only variable with a significant relationship to eye frailty. Regarding the relationship between eye frailty and subordinate items of the Kihon checklist, social withdrawal [odds ratio (OR) 2.437, 95% confidence interval 1.145–5.188], cognitive function (OR 2.047, 95%CI 1.051–3.984), and depressed mood (OR 1.820, 95%CI 1.163–2.848) were significant. Eye frailty can be considered a factor reflecting the existence of social and psychological/cognitive frailties.

The coronavirus (COVID-19) pandemic significantly affected the physical and mental functions in older adults, resulting in “corona-frailty”. This 2-year prospective study characterized changes in quantitative measures and corona-frailty among a cohort of community-dwelling older women. Changes were evaluated using face-to-face interactions with 39 Japanese women (mean age: 76.1 ± 5.9) in 2019 (pre-pandemic baseline) and 2021 (follow-up during the pandemic). Quantitative measurements of handgrip strength, walking speed, calf circumference, body composition, and background factors were evaluated. Body weight and trunk muscle mass significantly decreased at follow-up. Multiple regression analysis, using change in trunk muscle mass as the dependent variable and background factors as independent variables, identified that decrease in trunk muscle mass was associated with “being robust at baseline” and answering “Yes” to the question of “Do you go out less frequently compared with last year”? The 2-year trunk muscle mass change for each baseline frailty stage showed a significant decrease only in the robust group (−8.0%). The decrease in trunk muscle mass might be related to pandemic-induced lifestyle restraint, suggesting that robust older adults who are healthy and active should take measures that focus on trunk muscles to avoid “corona-frailty”.