Since PFT values vary according to age, sex, and ethnicity, PFTs were analyzed for percent predicted values based on age, gender, and race. Notably, median values for FEV1, FVC, and PEF were all close to 100% of the predicted value. The MVV percent predicted was available in 60 cases and was 93% of predicted values. The most significant difference from expected values was FEF 25% to 75%, at 84% of expected results.
Flow-volume loop evaluations on the 97 PFTs available were completed, and 58 of the 97 were noted for variable extrathoracic airway obstruction consistent with inspiratory inhibition in the patient population. This is 60% of the available PFTs in this cohort study.
Discussion
This retrospective chart review of 100 consecutive VCD diagnoses in a military treatment facility reinforces many of the findings currently available in the literature. As illustrated in a Chest review article, the diagnosis of VCD on history, physical examination, or PFTs remains ellusive.1 The PFT evaluation contains some subjectivity regarding the flattening of inspiratory flow-volume loops and is not routinely reported in PFT results. In patients diagnosed with VCD, a clear consensus of treatment modalities remains lacking. Modification of risk factors (allergic rhinitis, GERD, smoking cessation, weight loss) assisted in self-reported patient improvement, as did focused speech therapy.
The median age of 31 years, likely reflected the younger military population served at Eglin AFB. Seventy-five of these patients were currently on active duty, 6 were retired from active duty (veterans), and 19 were dependents. The median time of symptoms to diagnosis was 2 years. Prior misdiagnosis with other diseases such as asthma was common. Also, referral to Pulmonology and Speech Therapy was usually completed after failed outpatient primary care management for the alternative diagnoses.
Improvement with therapy was mixed, and during the time of documented follow-up, 72 patients reported complete or partial improvement. Most active-duty patients in the partial improvement category based this subjective reporting on their ability to meet military physical fitness standards.
Previous data suggested a female predominance, but this study population was 61% male. Military populations are about 80% to 85% male, so an increase in male diagnosis is expected.
Many patients in the patient cohort arrived as a result of Pulmonology referrals with a presumptive diagnoses of asthma but were determined not to have asthma through PFT results inconsistent with asthma, no improvement with β-agonist therapies, and negative methacholine challenges (if performed). These results prompted evaluations for other conditions and eventually a VCD diagnosis. As noted, exclusion of asthma is of particular importance in a military population, as medical discharges often are pursued in service members with asthma whether controlled or uncontrolled. Lag time to referral also is possible in failures of military physical, which prompted medical evaluation once several failures had occurred over a 1- to 2-year time frame.
The PFT data evaluation was inconclusive for statistically significant changes when compared with age-matched normal PFT values. This also was noted in previous studies of VCD cases. Most notable was percent predicted values of FEF 25% to 75%, with 84% of expected values. The FEV1, FVC, and PEF all fell within predicted values of normal, despite wide ranges in age, sex, and ethnicity among the subjects. Inspiratory flattening consistent with extrathoracic obstruction was present in 58 of the 97 PFTs available for review at Eglin AFB.
Limitations
Limitations to this retrospective case series are illustrated here. Cases were found only when VCD was diagnosed and coded; and it is the authors’ suspicion that many have been misdiagnosed or improperly treated for asthma or other pulmonary/oropharynx conditions. If providers are not familiar with VCD or if PFT readings do not comment on inspiratory findings, diagnosis is less likely. Some of the authors’ colleagues already have determined that postdeployment prevalence of VCD seems to be elevated.8
This cohort was completed on all patients in a military treatment facility, with 75 active-duty personnel, 6 veterans, and 19 dependents of varying ages. This case series is retrospective and tabulates suspected risk factors; stronger and more informative studies could certainly be completed in prospective studies (although likely difficult with low prevalence) or in treatment comparison studies at the time of diagnosis.
Since the cohort had varied and lengthy time to diagnosis from onset of related symptoms, the treatment patients received prior to diagnosis differed extensively. Diagnosis was completed by numerous primary care managers or other subspecialties prior to arrival to Pulmonology and Speech Therapy at Eglin AFB. Once diagnosed in Speech Therapy, consistent treatment options were provided to patients in accordance with standard of care.
It is the authors’ suspicion that VCD may have a higher prevalence than previously reported in the literature. Military service members are tested annually or biannually on physical fitness standards and are evaluated for medical reasons for recurrent fitness standard failures. This selection of patients is more likely to have a VCD evaluation as part of a comprehensive evaluation than is a healthy adult in a civilian population. A prospective study in military service members would be more fruitful and possibly yield a higher prevalence postdeployment.