Validity of inspiratory and expiratory methods of measuring gas exchange with a computerized system

Abstract

The accuracy of a computerized metabolic system, using inspiratory and expiratory methods of measuring ventilation, was assessed in eight male subjects. Gas exchange was measured at rest and during five stages on a cycle ergometer. Pneumotachometers were placed on the inspired and expired side to measure inspired (VI) and expired ventilation (VE). The devices were connected to two systems sampling expired O(2) and CO(2) from a single mixing chamber. Simultaneously, the criterion (Douglas bag, or DB) method assessed VE and fractions of O(2) and CO(2) in expired gas (FE(O(2)) and FE(CO(2))) for subsequent calculation of O(2) uptake (VO(2)), CO(2) production (VCO(2)), and respiratory exchange ratio. Both systems accurately measured metabolic variables over a wide range of intensities. Though differences were found between the DB and computerized systems for FE(O(2)) (both inspired and expired systems), FE(CO(2)) (expired system only), and VO(2) (inspired system only), the differences were extremely small (FE(O(2)) = 0.0004, FE(CO(2)) = -0.0003, VO(2) = -0.018 l/min). Thus a computerized system, using inspiratory or expiratory configurations, permits extremely precise measurements to be made in a less time-consuming manner than the DB technique.

Exercise does not feel the same when you are overweight: the impact of self-selected and imposed intensity on affect and exertion

“…A validation study of this system found that the differences compared to the gold-standard Douglas bag method were 'so small as to be not physiologically significant'. 43 The affective dimension of pleasure-displeasure during exercise was assessed with the Feeling Scale (FS). 44 The FS is an 11-point, single-item, bipolar rating scale commonly used for the assessment of affective responses during exercise.…”

Simultaneous multiple-subject analysis of respiratory gas exchange in humans

“…At this time, mixing chamber systems are intended for single-subject use only. The conventional system using the mixing chamber method has been developed to provide accurate measurements and the convenience of automated analysis 20,21) . Our new system shows time-series plots for all channels during collection on a single display.…”

Historical Development of Nutrient and Calorimetry and Expired Gas Analysis Indirect Calorimetry

“…In addition, there are considerable inconsistencies in using the Douglas bag assumptions that violate actual physiological function of the respiratory and collecting zones of the lung. Furthermore, the bags are made of PVC material, which is slightly permeable to the external air [3,7,8,12]. This mixing continues to the next expiration, as the first volume of air from the body is actually room air not alveolar air.…”

“…Some researchers have noted that it is very difficult to remove all the air from the Douglas Bag and air leaking out during the removal process [8]. According to some recent work of Bassett et al [3], the time need to be flushed out the Douglas bag valve and tubing inflated oxygen and decreased carbon dioxide gas content of room air. This dead air space acts to decrease the overall sensitivity and accuracy of the system.…”

“…Most exercise laboratories are using automated systems to measure respiratory gas exchange with a mixing chamber which gives time averaged values for respiratory variables [3,12,19,27,34]. The mixing chamber also offers the advantage of presenting data in real time and is just as time-saving as the breath-by-breath analysis.…”