THE RELATIONSHIPS BETWEEN MINUTE VENTILATION, PULMONARY GAS DIFFUSION AND RESPIRATORY WORK MEASURED SIMULTANEOUSLY DURING A STANDARD EXERCISE TEST

Early changes in pulmonary functions after mitral valve replacement

BACKGROUND:

This study evaluates changes in pulmonary functions before and after mitral valve replacement (MVR).

MATERIALS AND METHODS:

Twenty-five patients with rheumatic mitral lesions who had undergone MVR were divided into three groups, based on New York Heart Association (NYHA) class. They were evaluated for changes in pulmonary functions, preoperatively and postoperatively at 1 week, 1 month and 3 months to find any improvements after MVR.

RESULTS:

Forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), peak expiratory flow rates were universally found to be decreased preoperatively. Total lung capacity (TLC) and diffusion capacity (DLCO) were significantly reduced preoperatively in NYHA Class III and IV. The pulmonary functions further declined at 1 week after surgery. Except for FVC in NYHA Class IV (32.3% improvement, P < 0.05), the changes were statistically insignificant.

CONCLUSIONS:

Pulmonary functions deteriorate immediately after surgery and then recover gradually over a period of 3 months. However, they remain below the predicted values.

Fractional carbon monoxide uptake in an employed population

Stebbings, J. H. (1974). Thorax , 29 , 505-510. Fractional carbon monoxide uptake in an employed population. The fractional carbon monoxide uptake in 913 New York City transit workers was studied. A prediction equation for white males, based on nonsmokers, was obtained: fractional CO uptake = 0·58032 − 0·00204 × age + 0·0004 × weight (kilograms). Weight was the index of body size most strongly correlated with the fractional CO uptake. Decline in function with age by amount of tobacco smoked is described. A correction factor for respiration, based on results from 581 workers with two or more tests, was calculated: − 0·123654 × (standard tidal volume − observed tidal volume). Tidal volume was the most important contributor to individual variability of the fractional CO uptake, and minute volume or respiration rate do not add significantly to it. For epidemiological or screening uses, prediction equations are given for the fractional CO uptake corrected to 0·5 1. tidal volume. Respiration variables explain only 1·5% of individual variability, and individual variability over a mean period of 16·6 months was much larger (an individual standard error of 0·07) than the unexplained population variability (a population standard error of 0·01−0·02); thus the usefulness of the fractional CO uptake as a test of respiratory function is in doubt.