Development and validation of models to predict personal ventilation rate for air pollution research.

Air pollution intake represents the amount of pollution inhaled into the body and may be calculated by multiplying an individual's ventilation rate with the concentration of pollutant present in their breathing zone. Ventilation rate is difficult to measure directly, and methods for estimating ventilation rate (and intake) are lacking. Therefore, the goal of this work was to examine how well linear models using heart rate and other basic physiologic data can predict personal ventilation rate. We measured personal ventilation and heart rate among a panel of subjects (n = 36) while they conducted a series of specified routine tasks of varying exertion levels. From these data, 136 candidate models were identified using a series of variable transformation and selection algorithms. A second "free­living" validation study (n = 26) served as an independent validation dataset for these candidate models. The top­performing model, which included heart rate (Hr), resting heart rate (Hrest), age, sex, and hip circumference and interactions between sex with Hr, Hrest, age, and hip predicted ventilation rate (Ve) to within 11% and 33% for moderate (Ve = 45 L/min) and low (Ve = 15 L/min) intensity activities, respectively, based on the validation study. Many of the promising candidate models performed substantially worse under independent validation. Our results indicate that while measures of air pollution exposure and intake are highly correlated within tasks for a given individual, this correlation decreases substantially across tasks (i.e., as individuals go about a series of typical daily activities). This discordance between exposure and intake may influence exposure­response estimates in epidemiological studies. New air pollution studies should consider the trade­offs between the predictive ability of intake models and the error potentially introduced by not accounting for ventilation rate.

Reducing the dose of oral NSAIDs by use of Feldene Gel: an open study in elderly patients with osteoarthritis.

This open, parallel-group, multicenter study enrolled 191 general practice patients with mild to moderate osteoarthritis (OA) who were taking oral nonsteroidal anti-inflammatory drugs (NSAIDs). One group continued their usual NSAID treatment for 28 days without change in drug or dose. The other group reduced their dose of oral NSAID by a factor of two and concomitantly used 1 g of Feldene Gel, applied topically three or four times daily for 14 days. At the end of this period, if symptoms of OA remained controlled, the oral NSAID was stopped and patients used only the topical preparation for a further 14 days. Symptom scores as assessed by patients and investigators were similar for the two groups 14 and 28 days after Feldene Gel was started, except for tenderness and restriction of active movement. These parameters were significantly different in favor of the group treated topically. An assessment of quality of life also favored treatment with Feldene Gel. Both groups tolerated treatments well. Similar control of symptoms was observed in both groups when the oral NSAID was supplemented with Feldene Gel and when Feldene Gel was the only treatment.

A comparison of the triceps surae and residual muscle moments at the ankle during cycling.

The rigid linked system model and principles of inverse dynamics have been widely used to calculate residual muscle moments during various activities. EMG driven models and optimization algorithms have also been presented in the literature in efforts to estimate skeletal muscle forces and evaluate their possible contribution to the residual muscle moment. Additionally, skeletal muscle-tendon forces have been measured, directly, in both animals and humans. The purpose of this investigation was to calculate the moment produced by the triceps surae muscles and compare it to the residual muscle moment at the ankle during cycling at three power outputs (90, 180 and 270 W). Inferences were made regarding the potential contribution made by each triceps surae component to the tendon force using EMG and muscle-tendon length changes. A buckle-type transducer was surgically implanted on the right Achilles tendon of one male subject. Achilles tendon forces measured in vivo were multiplied by their corresponding moment arms to yield the triceps surae moment during the three working conditions. Moment arm lengths were obtained in a separate experiment using magnetic resonance imaging (MRI). Pedal reaction forces, body segment accelerations (determined from high speed film), and appropriate mass parameters served as input to the inverse solution. The triceps surae moment was temporally in phase with and consistently represented approximately 65% of the residual muscle moment at the ankle. These data demonstrate the feasibility of using implanted transducers in human subjects and provide a greater understanding of musculoskeletal mechanics during normal human movements.

Metoprolol in the aged hypertensive: a comparison of two dosage schedules.

Thirty-one patients aged 65 y or over suffering from moderate hypertension were studied for 16 weeks using a cross-over design in which metoprolol 100 mg daily and metoprolol 200 mg daily were compared. Both treatment regimes were effective in controlling hypertension and no difference was found between the two with regard to efficacy. The 100 mg regime was, however, better tolerated and we propose this as the preferred metoprolol dose for the aged hypertensive.