Anatomical backgrounds on gas exchange parameters in the lung

Many problems regarding structure-function relationships have remained unsolved in the field of respiratory physiology. In the present review, we highlighted these uncertain issues from a variety of anatomical and physiological viewpoints. Model A of Weibel in which dichotomously branching airways are incorporated should be used for analyzing gas mixing in conducting and acinar airways. Acinus of Loeschcke is taken as an anatomical gas-exchange unit.Although it is difficult to define functional gas-exchange unit in a way entirely consistent with anatomical structures, acinus of Aschoff may serve as a functional gas-exchange unit in a first approximation. Based on anatomical and physiological perspectives, the multiple inert-gas elimination technique is thought to be highly effective for predicting ventilation-perfusion heterogeneity between acini of Aschoff under steady-state condition. Changes in effective alveolar P_(O2), the most important parameter in classical gas-exchange theory, are coherent with those in mixed alveolar P_(O2) decided from the multiple inert-gas elimination technique. Therefore, effective alveolar-arterial P_(O2) difference is considered useful for assessing gas-exchange abnormalities in lung periphery.However, one should be aware that although alveolar-arterial P_(O2) difference sensitively detects moderately low ventilation-perfusion regions causing hypoxemia, it is insensitive to abnormal gas exchange evoked by very low and high ventilation-perfusion regions. Pulmonary diffusing capacity for CO (D_(LCO))and the value corrected for alveolar volume (V_(AV)), i.e., D_(LCO)/V_(AV) (K_(CO)), are thought to be crucial for diagnosing alveolar-wall damages. D_(LCO)-related parameters have higher sensitivity to detecting abnormalities in pulmonary microcirculation than those in the alveolocapillary membrane. We would like to recommend four categories derived from combining behaviors of D_(LCO) with those of K_(CO) for differential diagnosis on anatomically morbid states in alveolar walls:type-1abnormality defined by decrease in both D_(LCO) and K_(CO); type-2 abnormality by decrease in D_(LCO) but increase in K_(CO); type-3 abnormality by decrease in D_(LCO) but restricted rise in K_(CO); and type-4 abnormality by increase in both D_(LCO) and K_(CO).

Effect of pulmonary rehabilitation on oxidative stress in patients with pulmonary diseases

Exercise-training-based pulmonary rehabilitation has been confirmed to be effective in improving the activities of daily living (ADL) and relieving the dyspnea of chronic obstructive pulmonary disease (COPD) patients. Exercise training increases the antioxidant capacity of COPD patients, but since strenuous exercise and acute exercise loading have the opposite effect and increase oxidative stress, it is important to establish exercise training conditions that efficiently raise antioxidant capacity without increasing oxidative stress. Research on oxidative stress during exercise training by COPD patients has been pursued from that standpoint, but in recent years the targets of research on respirator diseases other than COPD have been expanding. In this article we will therefore review the results of research that has been conducted thus far on the effect of pulmonary rehabilitation on oxidative stress, including the results obtained at our own institution.

Classical regression equations of spirometric parameters are not applicable for diagnosing spirometric abnormalities in adipotic adults

The prevalence of overweighing and obese adults (defined as "adipotic" adults),has markedly increased over the world. A remarkable increase in the adipotic population urgently needs developing the regression equations for predicting spirometric parameters (SPs), which are specifically applicable to adipotic adults.Unfortunately, however, the reliable equations suitable for adipotic adults have not been reported to date. Recently, Yamaguchi et al have proposed the quantitative method to estimate the effects of adiposity on deciding the SPs incorporating with age-specific contributions of various explanatory,independent variables such as age (A), standing height (H), body weight (BW),and fat fraction of body mass(F). Extending the method proposed by Yamaguchi et al, we attempted to elaborate the novel regression equations applicable for diagnosing the spirometric abnormality in adipotic adults. For accomplishing this purpose, never-smoking, adipotic adults with body mass index (BMI) over 25 kg/m^2 and no respiratory illness were recruited from the general population in Japan (n = 3696, including men: 1890 and women: 1806). Introducing the four explanatory variables of A, H, BW, and F, gender-specific and age-dependent regression equations that allowed for prescribing the SPs in adipotic adults were constructed. Comparing the results obtained for non-adipotic adults (i.e., those with normal BMI), the negative or positive impact of height on SPs was preserved in adipotic adults, as well. However, the negative impact of age on SPs was blunted in adipotic men and the positive effect of BW on SPs was impeded in adipotic men and women. The fat fraction of body mass-elicited negative impact on SPs vanished in adipotic women. These results indicate that the regression equations of SPs for adipotic adults differ significantly from those for nonadipotic adults, leading to the conclusion that the regression equations for nonadipotic adults should not be used while judging the spirometric abnormalities in adipotic adults.