Portable Metabolic Measurement System Research Articles

VALIDITY OF A LOW-FLOW PNEUMOTACH AND PORTABLE METABOLIC SYSTEM FOR MEASUREMENT OF BASAL METABOLIC RATE

The accurate measurement of physiologic variables at rest is essential for determination of basal metabolic rate (BMR). Advances in technology have led to development of portable metabolic measurement systems which allow researchers to take systems into homes for the determination of BMR. The low flow volume produced during BMR assessment has proved difficult for portable units to accurately measure. Recently a pneumotach was developed for a portable metabolic measuring system for measuring oxygen consumption (VO2), carbon dioxide production (VCO2) and minute ventilation (VE) at rest. PURPOSE The purpose of this study was to investigate the validity of the MedGraphics VO2000 portable metabolic measurement system with a Low Flow Pneumotach (Medical Graphics Corp., St. Paul, MN) for the determination of VO2, VCO2 and VE at rest. METHODS A MedGraphics VO2000 equipped with a Low Flow Pneumotach was arranged in series to a MedGraphics CPX/D metabolic system. This back to front series allowed for identical samples to be obtained by both systems thus limiting biological and environmental variability from multiple testing sessions. Twenty-two(10 M, 12 F) young(24±6 yrs) healthy participants volunteered for this study. Mean height and weight were 173.2 cm(±10.2) and 73.5 kg(±10.9), respectively. Protocol consisted of subjects arriving to the laboratory after a 12 hr fast and lying quietly in a comfortable supine position for 10 minutes before data collection began. Inspired and expired gases were collected for 60 min. RESULTS Student's T-test demonstrated no significant difference (p < .05) between VO2, VCO2, or VE. These findings coincide with significant (P < 0.05) correlation coefficients of 0.78, 0.78 and 0.71 for VO2, VCO2, and VE, respectively. Bland-Altman plots indicated good agreement between the systems for VO2, VCO2 and VE. CONCLUSION Results of this study indicate that the MedGraphics VO2000 fitted with a Low Flow Pneumotach produces comparable results for VO2, VCO2 and VE to that of the MedGraphics CPX/D unit for measures of BMR.

Reliability and intensity of the six-minute walk test in healthy elderly subjects.

The 6-min walk test (6-MWT) is an easy and validated field test, generally used in patients to assess their physical capacity. We think that the 6-MWT could also be conducted in the same perspective in healthy subjects, aged 60-70 yr. However, little is known about the effect of the familiarization on the 6-MWT performance and the relative intensity of this test. The aims of this study were therefore to bring precision to the 6-MWT reliability and intensity in this population. METHODS; Over 3 d, 12 subjects performed two maximal exercise tests on treadmill and five 6-MWT (two in the morning and three in the afternoon) with a portable metabolic measurement system (Cosmed K4, Rome, Italy). The distance, walking speed, oxygen uptake (VO2 (max)), and heart rate (HR) values were measured during the 6-MWT. Distance, walking speed, and VO2(max) were only lower during the first two 6-MWT (respectively, P< 0.001, P< 0.001, and P< 0.05). HR was reliable from the first 6-MWT and was higher during the tests performed in the afternoon (P< 0.001). The intensity of the 6-MWT corresponded to 79.6 +/- 4.5% of the VO2(max), 85.8 +/- 2.5% of the HR (max), and 78.0 +/- 6.3% of the HR (reserve). Moreover, it was higher than the ventilatory threshold in each subject (P< 0.01). In healthy elderly subjects, the 6-MWT represents a submaximal exercise, but at almost 80% of the VO2(max). To be exploitable, two familiarization attempts are required to limit the learning effect. Finally, the 6-MWT time of day must be taken into account when assessing HR.

VALIDATION OF THE COSMED K4b2 PORTABLE METABOLIC MEASUREMENT SYSTEM

Purpose: The Cosmed K4b2 is a portable metabolic measurement system that is worn by the subject, allowing the assessment of energy expenditure in the field. The purpose of this study was to determine the validity of the K4b2 against the criterion Douglas bag (DB) method at rest and during incremental exercise to 250W. Methods: Seven male subjects completed two graded exercise tests on a cycle ergometer while fractional expired oxygen (FEO2) and carbon dioxide (FECO2), oxygen uptake (VO2), carbon dioxide production (VCO2), minute ventilation (VE), and respiratory exchange ratio (R) were measured by either the K4b2 or the DB method. Results: The results show that the K4b2 is accurate for the determination of VO2, VCO2, VE, and R at work rates from rest to 200W, despite significant differences in FEO2 and FECO2. These differences in FEO2 and FECO2 are due to the special characteristics of the K4b2 breath-by-breath system, which accounts for the deadspace of the facemask/valve and the brief time delay to match ventilation with gas fractions. At 250W, the K4b2 significantly underestimated VCO2 and R compared to the DB method.TableConclusion: These findings suggest that the K4b2 accurately measures energy expenditure at rest and during exercise and is appropriate for assessing the energy cost of activities outside the laboratory.

Validation of the COSMED K4 b2 Portable Metabolic System

The purpose of this investigation was to assess the accuracy of the COSMED K4 b2 portable metabolic measurement system against the criterion Douglas bag (DB) method. During cycle ergometry on consecutive days, oxygen consumption (VO2), carbon dioxide production (VCO2), minute ventilation (VE), and respiratory exchange ratio (R) were measured at rest and during power outputs of 50, 100, 150, 200, and 250W. No significant differences (P > 0.05) were observed in VO2 between the K4 b2 and DB at rest and at 250W. Though the K4 b2 values were significantly higher (P<0.05) than DB values at 50, 100, 150, and 200 W, the magnitude of these differences was small (0.088, 0.092, 0.096, and 0.088 L x min(-1), respectively). VCO2 and VE values from the K4 b2 were significantly lower than the DB at 200 and 250 W, while no significant differences were observed from rest through 150W. The slight overestimation of VO2 (50-200 W) combined with the underestimation of VCO2 (200 and 250W) by the K4 b2 resulted in significantly lower R values at every stage. These findings suggest the COSMED K4 b2 portable metabolic measurement system is acceptable for measuring oxygen uptake over a fairly wide range of exercise intensities.

Validity of four motion sensors in measuring moderate intensity physical activity.

This study tested the validity of four motion sensors for measuring energy expenditure (EE) during moderate intensity physical activities in field and laboratory settings. We also evaluated the accuracy of the EE values for selected moderate activities listed in the 1993 Compendium of Physical Activities. A total of 81 participants (age 19-74 yr) completed selected tasks from six general categories: yardwork, housework, occupation, family care, conditioning, and recreation. Twelve individuals performed each of the 28 activities examined. During each activity, EE was measured using a portable metabolic measurement system. Participants also wore three accelerometers (Computer Science and Applications [CSA], Inc. model 7164; Caltrac; and Kenz Select 2) and the Yamax SW-701 electronic pedometer. For the CSA device, three previously developed regression equations were used to convert accelerometer scores to EE. The mean error scores (indirect calorimetry minus device) across all activities were: CSA1, 0.97 MET; CSA2, 0.47 MET, CSA3, 0.05 MET; Caltrac, 0.83 MET; Kenz, 0.96 MET; and Yamax, 1.12 MET. The correlation coefficients between indirect calorimetry and motion sensors ranged from r = 0.33 to r = 0.62. The energy cost for power mowing and sweeping/mopping was higher than that listed in the 1993 Compendium (P < 0.05), and the cost for several household and recreational activities was lower (P < 0.05). Motion sensors tended to overpredict EE during walking. However, they underpredicted the energy cost of many other activities because of an inability to detect arm movements and external work. These findings illustrate some of the limitations of using motion sensors to predict EE in field settings.

Validation of Aerosport KB1-C portable metabolic system.

The purpose of this study was to test the validity of the Aerosport KB1-C portable metabolic measurement system against the criterion Douglas bag method. During cycle ergometry, simultaneous measurements of minute ventilation (VE), oxygen consumption (VO2), and carbon dioxide production (VCO2) were made at rest and at power outputs of 50, 100, 150, 200, and 250 W. No significant differences (P > 0.05) were observed for VE, VO2, and VCO2 between the KB1-C and Douglas bag at 100, 150, and 250 W, while the KB1-C was significantly different (P < 0.05) from Douglas bag values at rest, 50, and 200 W. R values were found to be significantly different (P < 0.05) at 100, 150, and 200 W, while no significant differences were observed at rest, 50, and 250 W. The fractional concentrations of oxygen (FEO2) and carbon dioxide (FECO2) were not significantly different at 50, 100, 200, and 250 W while values at rest and 150 W were significantly different (P < 0.05). These findings show that the Aerosport KB1-C portable metabolic system is acceptable for measuring oxygen uptake in the range of 1.5 and 3.5 L x min(-1), using the medium flow pneumotach setting. At lower intensities, the low-flow pneumotach setting provides acceptable results.

ACCURACY OF USING RPE TO MONITOR INTENSITY OF GROUP INDOOR STATIONARY CYCLING

643 The purpose of this study was to determine the accuracy of the Borg 6-20 RPE Scale as a subjective assessment of exercise intensity during a 40-minute group indoor cycling class (spinning). Seven novice, female subjects (38 ± 6 years) participated in two separate testing sessions, first an actual spinning class, and second a maximal GXT on a cycle ergometer. In both tests, a portable metabolic measurement system was used to collect physiological measurements (VO2 and HR) while subjects indicated perceived exertion levels (Borg 6-20 RPE). Results of paired sample t-tests revealed: (1) significantly higher HR's during spinning compared to GXT at RPE 12 (t=4.22; p=0.0056); and (2) significantly lower maximal RPE's during spinning compared to GXT (t=3.45; p=0.0137) with significantly higher HR-values (at maximal RPE's) during spinning compared to GXT (t=3.60; p=0.0113). In addition a 2 × 3 ANOVA was utilized to compare the actual VO2 and the VO2 estimates based on RPE at three intensity levels indicated by RPE 12, 15, and 16. A significant interaction was found between group and intensity (F=8.97; p=0.0009). Tukey's Post Hoc Tests showed that actual VO2's obtained during spinning were significantly higher than estimated VO2's at RPE 12 and 15. These results suggest that Borg's 6-20 RPE Scale may be inaccurate when used by novice participants to subjectively monitor intensity in a group indoor stationary cycling class and that the additional use of an objective measure such as HR monitoring may be needed to insure the safety and effectiveness of the program.

VALIDATION OF AEROSPORT KB1-C PORTABLE METABOLIC SYSTEM

The purpose of this study was to test the validity of the Aerosport KB1-C portable metabolic measurement system against the criterion Douglas bag method. During cycle ergometry, simultaneous measurements of minute ventilation (V E ), oxygen consumption (VO 2 ), and carbon dioxide production (VCO 2 ) were made at rest and at power outputs of 50,100,150, 200, and 250 W. No significant differences (P > 0.05) were observed for V E , VO 2 , and VCO 2 between the KB1-C and Douglas bag at 100, 150, and 250 W, while the KB1-C was significantly different (P < 0.05) from Douglas bag values at rest, 50, and 200 W. R values were found to be significantly different (P < 0.05) at 100, 150, and 200 W, while no significant differences were observed at rest, 50, and 250 W. The fractional concentrations of oxygen (F E O 2 ) and carbon dioxide (F E CO 2 ) were not significantly different at 50, 100, 200, and 250 W while values at rest and 150 W were significantly different (P < 0.05). These findings show that the Aerosport KB1-C portable rmetabolic system is acceptable for measuring oxygen uptake in the range of 1.5 and 3.5 L·min -1 using the medium flow pneumotach setting. At lower intensities, the low-flow pneumotach setting provides acceptable results.

Reliability and Validity of a Portable Metabolic Measurement System

The purpose of this study was to assess the reliability and validity of a portable metabolic system (TEEM 100) during submaximal and maximal (VO2max) exercise using a computer-based metabolic system as the reference system (REF). Between repeated trials of submaximal exercise at three constant loads, differences in ventilation (Ve) and oxygen consumption (VO2) were 0.2 +/- 4.9 L . min-1 and 0.03 +/- 0.10 L . min-1 for REF, and 1.9 +/- 0.7 L . min-1 and 0.00 +/- 0.17 L . min-1 for TEEM 100. Pooled intraclass reliability coefficients for Ve and VO2 calculated from the repeated submaximal trials were r = .89 and r = .94 for REF, and r = .86 and r = .94 for the TEEM 100. Respiratory exchange ratio (RER) measured by the TEEM 100 was significantly higher (p = .01) at only the lowest workload. At VO2max, the TEEM 100 recorded significantly higher values for FeO2 (p = .01) and RER (p < .001). These results suggest that the TEEM 100 provides reliable and valid measurements of VO2 during submaximal and maximal exercise.