Spirometry: A Key Tool for Every Office

Q: How critical-and cost-effective-is in-officepulmonary function equipment for the primarycare practitioner?

A: It is time for the spirometer to take its rightfulplace alongside the stethoscope, ophthalmoscope,sphygmomanometer, and electrocardiograph. Thespirometer is at least as important as any of these otherinstruments, because spirometric abnormalities are associatedwith all-cause mortality and indicate an elevatedrisk of lung cancer, myocardial infarction, and stroke.¹Currently, only about 30% of primary care clinicians usespirometers in their offices; most refer selected patientsto pulmonary function laboratories.

Spirometry plays a key role in the workup of dyspneaand chronic cough. Its importance is comparable to that ofelectrocardiography in a patient with chest pain; unlike electrocardiography,however, spirometry can identify occultdisease in asymptomatic patients. It can detect obstructivelung diseases, such as asthma and chronic obstructive pulmonarydisease (COPD), and restrictive lung diseases,such as sarcoidosis and congestive heart failure. Spirometricmonitoring is essential--particularly in asthma andCOPD--for determining if maximum therapeutic benefit isbeing achieved and for guiding dosage adjustments.

Keeping it simple. Factors that have delayed thewidespread adoption of spirometry in the primary care officeinclude misinformation about its complexity and costs.Spirometry simply measures the volume of air expiredwith maximum force after a full inspiratory effort (forcedvital capacity [FVC]) and the expiratory flow rate.

Only 2 values are needed in the evaluation-theforced expiratory volume in 1 second (FEV₁ [the flow test])and the FVC (the volume test)-and their ratio. The normalFEV₁/FVC ratio is greater than 70%. A lower ratio indicatesan obstructive disease. Ratios of 85% or more stronglysuggest a restrictive disease or ventilatory defect. Becausenormal lungs empty in 6 seconds or less, the forced expiratoryvolume in 6 seconds is an excellent surrogate for theFVC and is now the recommended standard.^2,3

Unfortunately, the other "parameters" that engineershave so enthusiastically added to devices that use flowtransducers-such as the midexpiratory phase of theforced expiratory flow (FEF_25%-75%) and other values-onlyserve to confuse. These numbers have no special meaningand should be removed from spirometers and testreports.

Spreading the word.

The aim of the National LungHealth Education Program (NLHEP) is to encourage primarycare physicians to use office spirometry for diagnosis andmanagement of COPD and other diseases. The NLHEPrecommends simple 2-parameter office spirometric testingfor all smokers and former smokers 45 years or older andfor persons who have dyspnea on exertion, chronic cough,mucus hypersecretion, or wheeze.

⁴

In response to requests from the NLHEP, severalmanufacturers have produced simple, accurate, and reliablespirometers that cost less than $1000. Less expensivedevices are being developed. Established billingcodes are used for reimbursement.

References:

REFERENCES: 1. Petty TL. Simple office spirometry. Clin Chest Med. 2001;22:845-859.
2. Hankinson JL, Odencrantz JR, Fedan KB. Spirometric reference values from asample of the general US population. Am J Respir Crit Care Med. 1999;159:179-187.
3. Swanney MP, Jensen RL, Crichton DA, et al. FEV6 is an acceptable surrogatefor FVC in the spirometric diagnosis of airway obstruction and restriction. Am JRespir Crit Care Med. 2000;162:917-919.
4. Ferguson GT, Enright PL, Buist AS, et al. Office spirometry for lung health assessmentin adults. A consensus statement from the National Lung Health EducationProgram. Chest. 2000;117:1146-1161.