Performance Comparison of the Hand-Held Microplus Portable Spirometer and the Sensormedics VMAX22 Diagnostic Spirometer

Abstract

Background

Portable spirometry offers many potential advantages over conventional lung function measurements obtained in a pulmonary function laboratory.

Methods

We compared the performance characteristics of the MicroPlus portable spirometer with the SensorMedics Vmax22 diagnostic spirometer used in our pulmonary function laboratory. Lung function measurements (forced expiratory volume [FVC], forced expiratory volume in the first second [FEV₁], and peak expiratory flow [PEF]) were obtained from both instruments simultaneously, during the same forced expiratory maneuver. The study group consisted of 20 normal subjects, 20 asthmatics with mildly reduced lung function, and 20 severely obstructed chronic obstructive pulmonary disease (COPD) patients.

Results

The difference between instruments (SensorMedics minus MicroPlus) was statistically significant for FVC in all 3 groups (0.31 L ± 0.57 in favor of the SensorMedics) and was also significant for FEV₁ (0.09 L ± 0.39) and PEF (0.33L/s ± 0.77) in the asthma and COPD groups. Between-group comparison of bias was highly significant (p = 0.0001) for PEF when comparing normal subjects with both obstructive lung disease groups. We also conducted a bench study in which we compared lung function from 3 additional MicroPlus units with the SensorMedics, measuring FVC from a 3-L syringe at several flow rates. A tendency to underestimate lung function, particularly at low expiratory flows, was noted in all 4 MicroPlus units tested.

Conclusion

We conclude that the MicroPlus underestimates lung function and, thus, the results obtained with the MicroPlus and the desktop SensorMedics Vmax22 diagnostic spirometer should not be considered equivalent or interchangeable. [Respir Care 1999;44(12):1465-1473]