Blood metabolite data in response to maximal exercise in healthy subjects.

Maximal exercise test with gas exchange measurement evaluates exercise capacities with maximal oxygen uptake (VO(2) max) measurement. Measurements of lactate (L), lactate/pyruvate ratio (L/P) and ammonium (A) during rest, exercise and recovery enhance interpretative power of maximal exercise by incorporating muscular metabolism exploration. Maximal exercise test with gas exchange measurement is standardized in cardiopulmonary evaluations but, no reference data of blood muscular metabolites are available to evaluate the muscular metabolism. We determined normal values of L, L/P and A during a standardized maximal exercise and recovery in 48 healthy sedentary volunteers and compared with results obtained in four patients with exercise intolerance and a mitochondrial disease. In healthy subjects, L, L/P and A rose during exercise. In 98% of them L, L/P or A decreased between the fifth and the fifteenth minutes of recovery. In mitochondrial patients, VO(2) max was normal or low, and L, L/P and A had the same evolution as normal subjects or showed no decrease during recovery. We gave normal L, L/P and A values, which establish references for a maximal exercise test with muscular metabolism exploration. This test is helpful for clinicians in functional evaluation, management and treatment of metabolic myopathy and would be a useful tool in diagnosis of metabolic myopathy.

Mouth and nasal inspiratory pressure: learning effect and reproducibility in healthy adults.

BACKGROUND: Inspiratory muscle strength measurements have become a cornerstone in monitoring neuromuscular disorders. Usually, sniff nasal inspiratory pressure (SNIP) and maximal inspiratory pressure (MIP) are performed. To our knowledge the session-to-session learning effect has rarely been evaluated for MIP performance and has never been done for SNIP performance. OBJECTIVES: We hypothesized that the sniff manoeuvre was natural and did not need to be learned, whereas the Muller manoeuvre, used for MIP measurement, was an isometric contraction which needed to be learned because it is rarely performed in real life conditions. This hypothesis suggests that from the first session and continuing through a subsequent one, the maximal SNIP value and the number of sniff trials necessary to attain it are more reproducible than the maximal MIP value and the number of Muller manoeuvre trials necessary to attain it. METHODS: Seventy-one healthy subjects were included. SNIP and MIP manoeuvres were repeated 12 and 6 times, respectively, per week during 2 sessions a week apart. RESULTS: We observed a session effect on MIP but not on SNIP. Maximal value for MIP was higher during the second session, whereas SNIP maximal value did not increase during the second session. The number of trials needed to obtain the maximal value for MIP was lower during the second session whereas it was not different for SNIP. CONCLUSIONS: SNIP is less sensitive to a learning effect than is MIP. It requires only a routine warm-up. We suggest that SNIP is preferable to MIP for repeated measurement of inspiratory muscle performance.

Performing the apnea of the single-breath carbon monoxide diffusing capacity: relaxation on the shutter or full inspiration with near atmospheric intrapulmonary pressure?

STUDY OBJECTIVES: The aim of the study was to measure the single-breath diffusing capacity of the lung for carbon monoxide (D(LCO)sb) in healthy subjects in the following two conditions originally proposed by the American Thoracic Society (ATS) guidelines: relaxation against the shutter; and full inspiration without straining. SETTING: D(LCO)sb was measured in 76 young adults in duplicate, in the two conditions. Mouth pressure was recorded during all of the trials. RESULTS: The mean (+/- SD) value of the duplicate D(LCO)sb measurements was higher when measured with the patient in the nonrelaxed condition than in the relaxed condition (32.65 +/- 7.65 vs 31.54 +/- 7.11 mL/min/mm Hg, respectively; p < 0.001). The mean effective alveolar volume measured during the single-breath maneuver (VAeff) was also higher in the nonrelaxed condition (VAeff: nonrelaxed condition, 5,779 +/- 1,093 mL; relaxed condition, 5,596 +/- 1,097 mL; p < 0.001), at least as a consequence of a higher inspiratory volume (Vin) in the nonrelaxed condition (nonrelaxed condition, 4,378 +/- 900 mL; relaxed condition, 4,232 +/- 902 mL; p < 0.001). Asking the subject performing a D(LCO)sb maneuver to relax on the shutter during apnea lowers the D(LCO)sb value by approximately 3.4% in comparison to full inspiration without straining, at least in part because it results in a reduced Vin. CONCLUSION: These data lend further support to the new European Respiratory Society/ATS Task Force recommendations (full inspiration maintained with near atmospheric intrapulmonary pressure).