Effects of body position, hyperinflation, and blood gas tensions on maximal respiratory pressures in patients with chronic obstructive pulmonary disease.

BACKGROUND--Inspiratory muscle strength in patients with chronic obstructive pulmonary disease (COPD) can be affected by mechanical factors which influence the length of the diaphragm, and by non-mechanical factors. The aim of the present study was to evaluate firstly the effects of body position on respiratory pressures and, secondly, to determine the relative contribution of age, body mass index (BMI), lung volumes, and arterial blood gas tensions to respiratory muscle strength. METHODS--Thirty male patients with stable COPD (mean FEV1 40.4% predicted) participated in the study. Maximal inspiratory and expiratory mouth pressures (PImax, PEmax) and maximal inspiratory transdiaphragmatic pressures (PDI) in the sitting and supine position, lung function, and arterial blood gas tensions were measured. RESULTS--Mean (SD) PImax in the sitting position was higher than in the supine position (7.1(2.3)kPa v 6.4(2.2)kPa respectively). In contrast, PDI in the sitting position was lower than in the supine position (10.0(3.5)kPa v 10.8(3.7)kPa respectively). PEmax was higher in the sitting position (9.3(3.0)kPa) than in the supine position (8.7(2.8)kPa). Significant correlations were found between inspiratory muscle strength on the one hand, and lung function parameters, BMI, and arterial blood gas tensions on the other. CONCLUSIONS--Inspiratory muscle strength in patients with COPD is influenced by mechanical factors (body position, lung volumes) and non-mechanical factors (BMI, FEV1, and blood gases). PImax and PEmax are lower in the supine position while, in contrast to healthy subjects, PDI is higher in the supine position than in the sitting position.     

Effect of acute metabolic acid/base shifts on the human airway calibre

Acute metabolic alkalosis (NaHCO(3)), acidosis (NH(4)Cl), and placebo (NaCl) were induced in 15 healthy volunteers (12 females, median age 34 (range 24-56) years) in a double blind, placebo controlled study to evaluate the presence of the effects on airway calibre. Acid-base shifts were determined by capillary blood gas sampling. Measurements were performed at the maximal acid-base shift, 90 min after intervention. Airway resistance (R(aw)) and specific airway conductance (sG(aw)), were evaluated, as primary variables, pre and post intervention. Secondary variables, including bronchial responsiveness to histamine, maximal respiratory mouth pressures and grip strength, were evaluated post intervention. In alkalosis, base excess (BE) increased from -0.3 (-3.0-1.9) to 3.0 (1.0-4.8) mmol/l and pH increased from 7.41 (7.37-7.43) to 7.44 (7.39-7.47) (both P<0.01), accompanied by an increase in Pa(CO(2)): 4.7 (4.0-5.7) to 5.0 (4.7-6.1) kPa (P<0.05). R(aw) increased from 0.156 (0.134-0.263) to 0.169 (0.132-0.271) kPa s/L (P<0.05), sG(aw) decreased, but this was not statistically significantly. In acidosis, BE decreased from -0.2 (-2.0-2.2) to -3.5 (-6.3-1.1) mmol/l and pH decreased from 7.41 (7.39-7.45) to 7.36 (7.31-7.40) (both P<0.01), accompanied by a non-significant decrease in Pa(CO(2)). Changes in R(aw) and sG(aw) were contrary to those in alkalosis, but did not reach statistical significance. Acute metabolic acid-base shifts mildly influence the airway calibre in healthy human subjects.     

Inhaled corticosteroids in patients with COPD: maintain current guidelines

The use of inhaled corticosteroids (ICS) is one of the most controversial issues in COPD treatment. There is evidence that ICS with or without long-acting beta-2-adrenergics (LABA) reduce exacerbation rates and improve the health status of severe COPD patients. The effects on FEV1 are limited and their effect on survival is unknown. Recently, a worldwide double-blind placebo-controlled study 'Towards a revolution in COPD health' (TORCH) was published in which salmeterol 50 microg and fluticasone 500 microg twice daily was compared with placebo, salmeterol alone or fluticasone alone. Of the 6112 included patients 875 died within 3 years after the start of treatment. Death rate, defined as the primary outcome parameter, was not significantly reduced (p = 0.052) while exacerbation frequency and health status improved in the combination therapy group. The TORCH trial therefore does not change current guidelines regarding trial treatment with ICS in severe COPD patients.     

Course of normal and abnormal fatigue in patients with chronic obstructive pulmonary disease, and its relationship with domains of health status

Objective

To examine the difference between patients with normal and patients with abnormal fatigue on aspects of health status, and investigate the natural course of fatigue in patients with Chronic Obstructive Pulmonary Disease (COPD).

Methods

Fatigue, physiological functioning, functional impairment, symptoms, and Quality of Life (QoL) were measured in 168 patients with COPD, and longitudinal data on fatigue of 77 patients were collected.

Results

Fifty percent of patients had abnormal fatigue. Patients with abnormal fatigue reported significantly more problems on the sub-domains of functional impairment (except actual physical activity), symptoms, and QoL as compared to patients with normal fatigue. With respect to physiological functioning patients with normal fatigue scores had better exercise capacity. Four years later the percentage of patients with abnormal fatigue was increased to 64%. In 1/3 of the patients an increase of more than the minimal clinically important difference was found.

Conclusion

Many COPD patients suffer from abnormal fatigue. Patients with abnormal fatigue have more limitations on many aspects of health status, especially on symptoms, functional impairment, and QoL.

Practice implications

Fatigue should be evaluated in usual care with a questionnaire that corrects for normal fatigue in order to tailor treatment to patients’ need.