The respiratory system is in part a mechanical pump or bellows. The Maximum Voluntary Ventilation test (MVV, aka Maximum Breathing Capacity, MBC) is intended to measure the maximum ventilation a patient is capable of. As such the results are dependent on a patient’s lung volume, respiratory muscle strength and endurance, airway resistance and overall inertia of the thoracic cage.

When I started doing PFT’s in the early 1970’s the MVV was a standard part of a complete workup. This has long since changed and I have not performed the MVV test routinely in over 25 years but I’ve always wondered what the MVV test is actually supposed be measuring in a clinical sense.

The ATS/ERS statement on spirometry recommends that the MVV test be 12 seconds long and that for optimum results the patient’s tidal volume should be approximately 50% of their VC at a respiratory rate of 90 breaths per minute. Tidal volume is accumulated during exhalation and at the end of the test the accumulated volume is then multiplied by 5. The ATS/ERS statement also suggests that MVV values that are less than FEV1 (L) x 40 indicate suboptimal patient effort.

The Maximum Voluntary Ventilation has been studied in a variety of disease states and has been shown to be reduced in upper airway obstruction, COPD, obesity, restraint position, dystonia, multiple sclerosis, diabetes, malnourishment, ALS, scoliosis, fatigue, Lupus, cervical spondylotic myelopathy, toxic chemical exposure, atrial fibrillation, polymyositis and chronic kidney failure. That MVV is reduced in these cases should not be a surprise as any reduction in lung volume, muscle strength or endurance, or any increase in airway resistance or inertia will act to limit MVV. A reduction in MVV is not specific however, and the fact that MVV is reduced does not by itself give any indication as to why it is reduced. This means that although the results may give a sense of a patient’s ventilatory status (i.e. good, fair, poor) they are not particularly diagnostic.

MVV has been most often used to evaluate maximum ventilation during cardiopulmonary exercise testing. Although it would seem that there should be a good correlation between maximum exercise ventilation and MVV this tends not to be the case. In particular MVV has been shown to be able to both under- and over-estimate Ve max in patients with airway obstruction. I think a legitimate criticism of comparing MVV and Max Ve results is that the MVV test requires the patient to adopt an artificial breathing pattern that has little relevance to actual exercise breathing patterns. At least one study has shown a higher MVV in what was termed the running position (standing, upper body angled forward 11 degrees, neck extended) when compared to the MVV performed while sitting upright. My personal experience, based on several years of performing both spirometry and MVV tests prior to CPET testing is that FEV1 x 40 is a far better predictor of Ve max than MVV.

One of my biggest concerns about the clinical use of MVV test results to monitor patient status is that patients often perform it poorly. As a technician, during the test you can try get the patient to breathe at the correct respiratory rate and tidal volume but too often I’ve seen patients either pant at very high respiratory rates and low tidal volumes or breathe slowly with very large tidal volumes. Repeated instructions and demonstrations on how to perform the test often make no difference in how well the patient is able to perform the test. In addition patients often refuse to repeat the test because of dizziness.

Although poor performance often leads to reduced MVV values I’ve also seen a number of patients with COPD get into what could best be described as a “resonance” with the testing system and produce MVV results that are well above what they should be capable of.

MVV can be be used as part of an overall assessment and has been used to evaluate patients pre- and post-operatively and pre- and post-exercise training. Because it is non-specific it cannot be a diagnostic test and because of patient performance issues it may be of limited value in monitoring patient outcomes. I strongly suspect that other non-specific multi-system tests like the 6-minute walk may be more clinically relevant than the MVV test and for these reasons I think any clinical usefulness of the MVV is quite limited.

Update:  The normal values for the MVV and the problems involved in assessing MVV test quality was discussed in Assessing MVV Quality.

References:

Bartlett RG, Phillips NE, Wolski G. Maximum voluntary ventilation prediction for the velocity-volume loop. Chest 1963; 43: 382-392

Carter R, Peavlre M, Zinkgraf S, Williams J, Fields S. Predicting maximal exercise ventilation in patients with chronic obstructive pulmonary disease. Chest 1987; 92: 253-259

Dillard TA, Hnatiuk OW, McCumber TR. Maximum Voluntary Ventilation. Spirometric determinants in chronic obstructive pulmonary disease and normal subjects. Amer Rev Resp Dis 1993; 147: 870-875

Haas F, Simnowitz M, Axen K, Gaudino D. Haas A. Effect of upper body posture on forced inspiration and expiration. J Appl Physiol 1982; 52: 879-886.

Matheson HW, Spies SN, Gray JS, arnum DR. Ventilatory Function Tests: II. Factors affecting the voluntary ventilation capacity. J Clin Invest 1950; 29: 682-687.

Miller MR, et al. ATS/ERS Task Force: Standardization of Spirometry. Eur Respir J 2005; 26: 319-338.

Pineda H, Haas F, Axen K, Haas A. Accuracy of pulmonary function tests in predicting exercise tolerance in chronic obstructive pulmonary disease. Chest 1984; 86: 564-567

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