Effect of Regular Use of High-dose Nebulized β2-Agonists on Resting Energy Expenditure, Weight, and Handgrip Strength in Patients With Chronic Airflow Limitation: Measuremen t of REE
The flow rate was checked every 2 months by nitrogen gas infusion and remained at 45.2 L/min. A paramagnetic oxygen analyzer and an infrared carbon dioxide analyzer sample continuously from the canopy and a microprocessor calculates Vo2 and carbon dioxide production (Vco2). A readout of average values is given at 1-min intervals. Sampling is continued until six steady-state readings (<5% variation) are obtained. This generally takes about 15 to 20 min. The gas analyzers are calibrated each time the metabolic monitor is used by means of a commercial calibration gas mixture (Electrochem Ltd; Stoke on Trent, UK) that is independently checked in our laboratory by the Haldane technique.
Measurements were made in the morning after an overnight fast and when the patient was in a stable clinical state with no fever or symptoms of infection. The patients were brought to the laboratory by taxi to minimize exertion that morning. They brought an overnight timed urine sample. All measurements were carried out in a dedicated “metabolic room” that was not used for any other purpose, and in which only the investigator and the subject were present. There were no external stimuli such as television and radio. The patients were observed, encouraged to relax, but it was checked that they did not fall asleep.
On arrival, they rested while the St George’s Hospital Respiratory Questionnaire was administered. This is a validated standardized quality-of-life questionnaire that gives score for activity, symptoms, and impact plus an overall score in relation to respiratory disease. It is a useful way of judging whether patients are similar in the way that their disease affects them. REE was then measured as described above, following which anthropometric measures were made; height, weight, midarm circumference (MAC), triceps skinfold (TSF) using skin callipers (John Bull; British Indicators Ltd), and HGS using a handgrip dynamometer (C.H. Sterling Co; Chicago). MAC, TSF, and HGS were measured in each arm, the dominant side being noted. TSF was measured as described by Durnin and Wormersley by the same experienced operator. Muscle mass was estimated from height, and TSF and MAC were estimated using the equations of Heymsfield et al. Fat mass was derived from TSF, and fat-free mass (FFM) was calculated by subtracting the fat mass from body weight. This method of deriving FFM from TSF has been validated in COPD patients by our group by comparison with values obtained by dual energy X-ray absorptiometry (unpublished work).
Category: Airflow Limitation
Tags: chronic airflow limitation, resting energy expenditure