New clinical applications for spirometry are at hand.
Printed in the Journal for Respiratory Care Practitioners / RT
October/November 1997 pp 51-54, 103
by: Thomas L. Petty, MD
Dr. Petty picks as his number one weapon in this effort the lowly spirometer. In his editorial in the February/March issues of RT, he argued that every primary care physician=s office and clinic should have a spirometer, and that these devices should routinely be used for the early detection of lung disease.
In his previous article, Dr. Petty focused on using the spirometer for early detection of smoking-related obstructive lung disease. In this issue, his commentary concerns other disease states whose diagnosis or management is facilitated by spirometric testing.
Let=s hope that the National Lung Health
Education Program succeeds in raising the level of consciousness of all health
care professionals on these issues. Our patients are sure to benefit.
He offered his device to the insurance industry, but, alas, his wisdom was not (and still is not) fully appreciated. This fact was later borne out in many studies, including the Framingham Study3 and the Honolulu Heart Program.4 Both showed that reduced vital capacity was a better indicator of premature morbidity and mortality from heart disease than any other single noninvasive test. Spirometric abnormalities can also be used to predict mortality from all causes.5 In addition to the most frequent applications of spirometry in the diagnosis and monitoring of obstructive and restrictive lung diseases, it has many other applications.
Congestive Heart Failure and Acute Myocardial Infarction
A reduction in vital capacity parallels the accumulation of extra vascular lung water6,7 (See Figure 1).
HIV and AIDS
The multiplicity of pulmonary problems that befall the patient who is immunosuppressed because of HIV infection is well known. Vital capacity can be reduced by Pneumocystis carinii pneumonia, cytomegalovirus infection, Mycobacterium avium-intracellulare infection, and common aerobic infections, as well as by noninfectious infiltrations that include eosinophilic pneumonia and lymphocytic interstitial pneumonitis.8 (A reduced diffusion test is even more valuable than a vital capacity determination in assessing the pulmonary impairment associated with AIDS-related pulmonary infections.8) Because of this, it would be perfectly reasonable for patients with AIDS and other immunosuppressive disorders to monitor their vital capacity at home in order to detect early (and, possibly, even asymptomatic) stages of pulmonary infection or other pneumonic complications of AIDS.
Heart or Lung Transplantation
Since rejection or infection are the reasons for failure of heart or lung transplantation, and since both affect forced vital capacity, it seems reasonable for post-transplant in patients to monitor their ventilatory function at home. In fact, this has become established practice in many centers.9 Spirometric abnormalities may or may not correlate with symptoms of cough and dyspnea and offer an early clue to impending complications as well as the need for bronchoalveolar lavage for diagnostic purposes.9
Motor neuromuscular disorders such as Guillain-Barré syndrome, myasthenia gravis, and other peripheral neuropathies and myopathies that may run an episodic course characterized by exacerbations and remissions, could be monitored at home using simple spirometry. Since a reduction in the patient=s ability to fill the lung compromises vital capacity, any progressive reduction in this important Avital@ sign would be important. The inexorable downhill curves of amyotrophic lateral sclerosis, (motor neuron disease) can be effectively monitored through serial measurements of vital capacity, as can the muscular dystrophies that involve the respiratory muscles, such as Duchenné=s muscular dystrophy.
Toxic Exposure and Chronic Fatigue Syndrome
Drugs of the organic pesticide family can cause neuromuscular blockade, so the results of a real or perceived toxic exposure could be charted by serial measurements of vital capacity.
In chronic fatigue syndrome, a reduced vital capacity may herald the onset of a more serious underlying neuromuscular disorder. Thus, monitoring vital capacity may provide evidence of a progressive ventilatory disorder requiring further evaluation in patients with vague somatic and respiratory complaints that may be of neurotic or physiological origin.
The crises of sickle-cell anemia are characterized by repeated pulmonary vascular thromboses. Episodes of this complex problem can be identified and monitored using serial measurements of vital capacity.10 Serial measurements of vital capacity in patients with sickle-cell trait who are exposed to high altitude (which can precipitate a sickle-cell crisis) have not shown an impairment in vital capacity.11 Thus, in this example, the spirometer can be used to offer reassurance to those who are concerned about altitude exposures if they have the sickle-cell trait.11
More than a decade ago, a leader in pulmonology asked: Who needs a pulmonary function laboratory?12 In this interesting editorial, the seasoned clinician lamented the fact that simple spirometers were not widely used at the bedside, in clinics, and physicians= offices. He recognized the value of immediately available clinical measurements of vital capacity and forced expiratory volume in 1 second (FEV1), and the critical necessity of integrating these fundamental measurements into the generation of a physiologically oriented concept that helped to explain the patient=s symptom complex.12 Such an integration was not promoted by reading a pulmonary function testing report outside the context of the patient=s history and physical examination results.
In these examples, the expanded role of spirometry, including home monitoring (primarily of vital capacity), opens new vistas for this important diagnostic test. The National Lung Health Education Program aims to put spirometry in the hands of all primary care practitioners (and of appropriate patients at home). Representatives of spirometry companies have told me that practical, direct-readout spirometers that display vital capacity, FEV1, and the ratio between the two can be mass-produced and placed on the market for about $200. Established and expanded old and new applications for clinical spirometry are at hand. This ushers in a new era for spirometry testing that promises to be exciting in the days ahead.
Thomas L. Petty, MD, is faculty consultant for HealthONE Center for Health Sciences Education and professor of medicine at the University of Colorado School of Medicine, Denver.
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