Normal Values

Normal values for MSV, by any method, have not been systematically obtained over a wide population, and results vary considerably between laboratories (Table 1). The large differences in predicted values may be due in part to variations in technique, particularly with respect to impedances of the mechanical measuring devices. The system impedance can have substantial effects on the total Wrs at high ventilations. In addition, there are differences in the populations studied and what was defined as sustainable. It is recommended that when publishing reports of ventilatory endurance, the value for the impedance of the measuring device be stated. Until more complete population standards and uniform equipment and techniques are available, each laboratory is advised to establish its own population standards.

Results for MSV should be reported as a fraction of measured MVV (MSV/MVV%) and either as an absolute value (L/minute) or as a fraction of predicted MVV (MSV/MVV% pred). The latter, which has not been used routinely, provides a normalization of the absolute sustainable value to the patient's age, height, and sex, independent of inherent lung or respiratory muscle function.

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