Recognizing correct and incorrect FVC maneuvers

Characteristics of correctly performed maneuvers are:
•	they seem to be delivered with maximal effort, starting from the level of maximum inspiration
•	the forced expiratory maneuver is started instantaneously with a 'blast' leading to a rapid rise to peak flow, and the effort is sustained until the end of the VC
•	the maneuver was not disturbed by coughing, a continuous exhalation to residual volume
•	no evidence for leaks at the mouthpiece
•	no evidence of obstruction at the mouth opening due to the tongue or biting the mouthpiece, or to bad fitting dentures

It is important that, while you instruct and encourage the patient and handle the equipment, you keep an eye on the patient in order to be able to assess subject cooperation.

Inspection of flow-volume curves may yield important information: reproducible shape, sharp peak, uninterrupted exhalation, complete exhalation indicated by gradual drop of flow to zero rather than a sudden drop. Pain, stress incontinence and poor understanding may lead to unsatisfactory maneuvers.

Criteria for reproducible values of FEV1 and FVC according to ATS/ERS (ref. 1) are:
•	Report the largest value of FEV1 and FVC of three technically satisfactory maneuvers; the reported values need not be from the same maneuvers.
•	The back extrapolated volume should be less than 150 mL or 5% of the FVC, whichever is greater.
•	Both the FEV1 and the FVC reported should not differ by more than 150 mL (100 mL if the FVC is 1.0 L or less) from the next largest FEV1 and FVC, respectively. If the difference is larger up to 8 maneuvers (ref. 2) should be performed.
•	If more than 8 maneuvers are required to satisfy the criteria, then report the largest FEV1 and FVC with a note that reproducible measurements could not be obtained.

ATS/ERS (ref. 1) recommendations are as follows:
FVC minimum duration	6 s, (3 s for children) or plateau in the volume-time curve. Subject cannot or should not continue to exhale.
FVC end of test criteria	• subject cannot or should not continue further exhalation, or • the volume time curve shows an obvious plateau, or • the forced exhalation is of reasonable duration
FVC maximum number of maneuvers	8, both in adults and children
FVC maneuver acceptability: none of the following applies	• unsatisfactory start of expiration • back extrapolated volume >5% of FVC or 150 mL, whichever is greater • coughing that interferes with the measurement of FEV1 and/or FVC • early termination of expiration • Valsalva maneuver • a leak • an obstructed mouthpiece, no glottis closure • effort that is not maximal throughout
FVC and FEV1 repeatability	the largest and second largest FVC and or FEV1 must not differ by more than 150 mL

Rather than carrying out retrospective quality checks it is better to have online feedback on quality aspects of forced expiratory maneuvers. Those developed by Enright c.s. (ref. 1) have been used in very large studies. They entail the following:

Maneuver acceptability
Message	Criterion
Start faster	back-extrapolated volume> 5% of FVC and > 150 mL
Blast out harder	time to peak expiratory flow > 85 ms
Avoid coughing	50% drop in flow in first second
Blow out longer	forced expiratory time < 6 s (see also here)
Blow out more air	flow > 0.2 L/s within 20 mL or FVC end point

Reproducibility criteria
	difference between current maneuver value and highest value from any other acceptable maneuver from the testing session :
Blow out harder	peak expiratory flow > 10%
Take a deeper breath	FVC > 200 mL and > 5% best FVC
Blow out faster	FEV1 > 100 mL and > 5% best FEV1

A more recent recommendation is that from the NLHEP (ref. 1). It was especially designed for 'office spirometry' carried out by primary care providers in patients of at least 45 years who smoke cigarettes. One should therefore be aware of the fact that the recommendation does not address younger subjects, and that it was especially designed for detecting COPD. NLHEP is in favor of using the FEV6 as a substitute for the FVC; this is not widely accepted. Hence, two minor modifications make the NLHEP recommendation more suitable for general use, including clinical environments.

Maneuver acceptability
Message	Criterion
Don't hesitate	back extrapolated volume > 150 mL
Blast out faster	time to peak expiratory flow > 120 ms
Blow out longer	change in exhaled volume during the last 0.5 s > 100 mL, and forced expiratory time < 2 s (see also here)
Blast out harder	PEF values do not match within 1.0 L/s,
Deeper breath	FVC values do not match within 150 mL
Only one error message is displayed (in the order of priority listed above)
Good test session	After 2 acceptable maneuvers that match

Quality control grades
A	at least two acceptable maneuvers with the largest two FEV1 values matching within 100 mL
B	at least two acceptable maneuvers with FEV1 values matching between 101 and 150 mL
C	at least two acceptable maneuvers with FEV1 values matching between 151 and 200 mL
D	only one acceptable maneuver, or more than one, but the FEV1 values match > 200 mL (with no interpretation)
F	no acceptable maneuvers (with no interpretation)

Ref. 1 - Acceptability and quality criteria
1	Quanjer PhH, Tammeling GJ, Cotes JE, Pedersen OF, Peslin R, Yernault JC. Lung volumes and forced ventilatory flows. Official Statement of the European Respiratory Society. Eur Respir J 1993; 6 suppl. 16: 5-40. Erratum Eur Respir J 1995; 8: 1629.
2	American Thoracic Society. Standardization of spirometry. 1994 update. Am J Respir Crit Care Med 1995; 152: 1107-1136.
3	Enright PL, Johnson LR, Connett JE, Voelker H, Buist AS. Spirometry in the Lung Health Study. 1. Methods and quality control. Am Rev Respir Dis 1991; 143: 1215-1223.
4	Ferguson GT, Enright PL, Buist AS, Higgins MW. Office spirometry for lung health assessment in adults. A consensus statement from the National Lung Health Education Program. Chest 2000; 117: 1146-1161.
5	Miller MR et al. Standardisation of spirometry. ATS/ERS task force: standardisation of lung function testing. Eur Respir J 2005; 26: 319-338.
Ref. 2 - If 8 maneuvers have not led to a FVC or FEV1 meeting the above requirements for reproducibility, then further attempts are useless:
1	Ferris BG Jr, Speizer FE, Bishop Y, Prang G, Weener J. Spirometry for an epidemiologic study: deriving optimum summary statistics for each subject. Bull Europ Physiopathol Respir 1978; 14: 145-166.
2	Kanner RE, Schenker MB, Munoz A, Speizer FE. Spirometry in children: methodology for obtaining optimal results for clinical and epidemiological studies. Am Rev Respir Dis 1983; 127: 720-724.

Last modified on 27.02.2018 17:11