Body plethysmography--its principles and clinical use

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.

[Systemic manifestations and comorbidities in patients with chronic obstructive pulmonary disease (COPD) and their effect on clinical state and course of the disease--an overview of the cohort study COSYCONET]

BACKGROUND AND RATIONALE

The integrated project COSYCONET, as part of the competence network ASCONET funded by the BMBF, has the aim to investigate the relationship between the pulmonary disorder, comorbidities and systemic inflammation in patients with chronic obstructive pulmonary disease (COPD) by adopting cross-sectional as well as longitudinal analyses.

METHODOLOGICAL APPROACH

COSYCONET includes a number of projects addressing the issue of comorbidities at the basic science level. Its core project, however, is the establishment of a cohort of patients with COPD, which is compared with two population-based control cohorts. The COPD cohort will include 3,000 patients, among them 1,500 with severity according to GOLD category I/II and 1,500 with category III/IV. Patients will be recruited in study centers covering all major regions of Germany, and this will be achieved in close cooperation with pneumologists from private practices. After recruitment, patients will be studied upon an initial visit as well as 6 and 18 months later. Each visit includes a comprehensive battery of functional tests and questionnaires that aim at assessing the state of the disease as accurately and completely as feasible, comprising lung function and the individual pattern and risk factors of comorbidities including cardiovascular disorders, metabolic disorders, osteoporosis, exercise capacity, acticity and mental status. In addition blood samples will be taken and asservated in a biobank in order to assess markers of systemic inflammation and aging as well as organ-specific markers. Moreover morphological information on the lung as available from HR-CT pictures that have not been specifically taken for the study will be analysed semi-quantitatively in a central facility and standardised manner.

Effects of cigarette smoke extract and nicotine on bronchial tone and acetylcholine-induced airway contraction in mouse lung slices

BACKGROUND

Tobacco smoke is a key risk factor for chronic obstructive pulmonary disease, but it may also alter the pathophysiology of asthma. In the present study, we analyzed whether tobacco smoke has acute or chronic effects on bronchial tone and whether it alters bronchial reactivity in vitro.

METHODS

Airways in murine lung slices were digitally recorded and the change in cross-sectional area with time was quantified. T-bet KO mice served as a model for bronchial hyperreactivity. T-bet KO mice show a shift towards type 2 helper T lymphocytes and display histological as well as functional characteristics of asthma. Cigarette smoke extract (CSE) was obtained using commercially available cigarettes (Gauloise Blondes) by drawing cigarette smoke slowly through a water pump into a tube containing 10 mL of DMEM culture medium.

RESULTS

Acute exposure to CSE led to relaxation of the airway. Acute exposure to nicotine resulted in a minor relaxation of the airway in Balb/C mice and in nonsignificant relaxation of the airway in T-bet KO mice. The nicotinic acetylcholine-receptor hexamethonium partially inhibited CSE-induced airway relaxation. Airway contraction in response to acetylcholine was stronger in T-bet KO mice than in Balb/C mice. After exposure to CSE or nicotine for 48 hours, acetylcholine-induced airway contraction was no longer different between the 2 types of mice.

CONCLUSIONS

Our data indicate that acute exposure to CSE leads to airway relaxation, which is partially mediated by nicotine. Chronic exposure to CSE reverses bronchial hyperreactivity in the airways of T-bet KO mice; this effect can be mimicked by chronic exposure to nicotine.

[Prognostic factors for COPD patients with chronic hypercapnic respiratory failure and home ventilation]

The prevalence of patients with severe COPD and chronic hypercapnic respiratory failure (CHRF) receiving non-invasive home ventilation has greatly increased. With regard to disease severity, a multidimensional assessment seems indicated. Base excess (BE), in particular, reflects the long-term metabolic response to chronic hypercapnia and thus constitutes a promising, easily accessible, integrative marker of CHRF. Infact, BE as well as nutritional status and lung hyperinflation have been identified as independent predictors of long-term survival. In addition and in a review with the literature, a broad panel of indices including frequent comorbidities are helpful for assessment and monitoring purposes of patients with CHRF. Accordingly, in view of the patients' individual risk profile, the decision about the initiation of NIV should probably not rely solely on symptoms and chronic persistent hypercapnia but include a spectrum of factors that specifically reflect disease severity. Owing to the physiologically positive effects of NIV and according to retrospective data, patients with COPD and recurrent hypercapnic respiratory decompensation and patients with prolonged mechanical ventilation and/or difficult weaning could also be considered for long-term non-invasive ventilation. This, however, has to be corroborated in future prospective trials.

Therapeutic approaches in metastatic renal cell carcinoma: local immunotherapy

Since 1990, aerosol interleukin (IL)-2 has been used to treat pulmonary metastatic renal cell carcinoma (pmRCC). Inhalation therapy deposits a drug into the airways to achieve a high, local, clinical effect while avoiding serious systemic side effects. We report three studies to describe safety and efficacy of aerosol IL-2 in patients with pmRCC. In a multicenter study, 24 patients received exclusive inhalation (study I) of natural IL-2 (three dose levels, 48 weeks) and response and toxicity were evaluated. The survival of high-risk patients (study II) with mainly inhaled IL-2 (n=94) was compared with that of patients receiving systemic IL-2 (n=103). In ten patients we analyzed in detail lung function and markers of airway inflammation before and during inhalational IL-2 therapy (study III). Study I: The response of exclusive inhalation was 33.3% at 3 months and 16.7% at 6 months. Treatment was well tolerated, cough being the most frequent adverse event. Study II: The probabilities of survival at 5 years were 21% for the inhalational group and 0% for the systemic group. Study III: Inhaled IL-2 induced a moderate decline of forced expiratory volume (FEV), while exhaled nitric oxide (NO) and sputum eosinophils rose accompanied by moderate cough and dyspnea. In conclusion, inhalational IL-2 combines good efficacy and improves tolerability. This is especially important for patients who are not able to benefit from systemic IL-2 therapy. Whether the local eosinophilic response additionally supports the antitumor effect remains a challenging question.