No abstract

The autonomic nervous system may be disturbed in chronic respiratory failure. We tested the hypothesis that there is increased sympathetic activity in patients with chronic hypoxemia. Furthermore, we examined the effect of short-term oxygen on muscle sympathetic nerve activity (MSNA) in these patients. We performed microneurography of the peroneal nerve in 11 patients with hypoxemia due to chronic obstructive pulmonary disease (COPD, n = 6) or lung fibrosis (n = 5) and in 11 healthy subjects matched for age and sex. MSNA was measured during normal breathing in all subjects. In eight patients and in seven control subjects, MSNA was also measured during nasal oxygen (4 L/min). MSNA was higher in the patients with chronic respiratory failure compared with the healthy subjects during normal breathing (61 +/- 5 versus 34 +/- 2 bursts/min, mean +/- SEM; p = 0.0002, paired t test). During oxygen administration, MSNA decreased from 63 +/- 6 to 56 +/- 6 bursts/min in the patients (p = 0.0004, ANOVA); there was no change in sympathetic activity in the control subjects. For the first time, there is direct evidence of marked sympathetic activation in patients with chronic respiratory failure. This is partly explained by arterial chemoreflex activation and may play an important role in the pathogenesis of the disease.

Body plethysmography allows to assess functional residual capacity (FRC(pleth)) and specific airway resistance (sRaw) as primary measures. In combination with deep expirations and inspirations, total lung capacity (TLC) and residual volume (RV) can be determined. Airway resistance (Raw) is calculated as the ratio of sRaw to FRC(pleth). Raw is a measure of airway obstruction and indicates the alveolar pressure needed to establish a flow rate of 1 L s(-1). In contrast, sRaw can be interpreted as the work to be performed by volume displacement to establish this flow rate. These measures represent different functional aspects and should both be considered. The measurement relies on the fact that generation of airflow needs generation of pressure. Pressure generation means that a mass of air is compressed or decompressed relative to its equilibrium volume. This difference is called "shift volume". As the body box is sealed and has rigid walls, its free volume experiences the same, mirror image-like shift volume as the lung. This shift volume can be measured via the variation of box pressure. The relationship between shift volume and alveolar pressure is assessed in a shutter maneuver, by identifying mouth and alveolar pressure under zero-flow conditions. These variables are combined to obtain FRC(pleth), sRaw and Raw. This presentation aims at providing the reader with a thorough and precise but non-technical understanding of the working principle of body plethysmography. It also aims at showing that this method yields significant additional information compared to spirometry and even bears a potential for further development.

There is no clear evidence as to how maximal inspiratory mouth pressure (PI,max) should be measured, although plateau pressures sustained for 1 s and measured at residual volume (RV) are usually recommended.Peak and plateau PI,max were measured at RV and at functional residual capacity (FRC) in 533 healthy subjects (aged 10-90 yrs) in order to comparably test all PI,max measurements for their predictors, reproducibility and normal values.Plateau pressures accounted for 82.0-86.3% of peak pressures. Peak and plateau pressures measured at FRC accounted for 84.3-90.5% of pressures at RV, and were highly correlated. Age was negatively predictive and weight and body mass index positively predictive of PI,max, but regression parameters were low. All PI,max measurements were comparable when calculating regression parameters, between-subject variability and reproducibility.In conclusion, peak and plateau maximal inspiratory mouth pressure are comparably useful for the assessment of inspiratory muscle strength and can be reliably measured at functional residual capacity and at residual volume. Regression equations are of low impact in predicting normal values due to the weak influence of demographic and anthropometric factors and to the high unexplained between-subject-variability. Agerelated 5th percentiles can indicate the lower limit of the normal range. Eur Respir J 2004; 23: 708-713.

This document is a revision of the guideline for diagnosis and treatment of COPD that replaces the version from 2007. A multitude of recent reports regarding risk factors, diagnosis, assessment, prevention and pharmacological as well as non-pharmacological treatment options made a major revision mandatory. The new guideline is based on the GOLD document taking into account specifics in Germany and Austria.