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32
Chapter 2: Astra 300 Functional Operation
The Spirometry Source
see and hear a forced expiration, they are more apt to
perform well. Body language is the key to good performance.
Instruct the patient to put the AstraGuard filter between his/
her teeth and make a good, tight seal with his lips. After the
patient slowly makes a maximal inspiration, the first phase of
the test, loudly exhort the patient to BLAST out. This
element of surprise will help the patient to realize the
maximum peak flow, which is the second phase of the test.
The third phase of the test, which involves diminished
flow, is important to achieve the highest possible volume of
patient FVC. Traditionally, technicians have loudly instructed
the patient to “blow, blow, blow…keep going, keep going!” to
achieve the maximal forced volume, when the opposite
approach may actually be more effective.
Evidence suggests that using the “soft sell” may be
better for achieving the best performance during the third
phase. “Draw [the patient’s] attention to the …audio tone of
the flow-sensing spirometers, which shows that he or she is
continuing to get out some air.” “Patients should be quietly
told to ‘keep going; I can see you’re still getting more air
out.’”
2
This is a critical part of the test, since an obstructed
patient may actually still be expelling a volume of air, but it
may not seem apparent, and many times the test is stopped
too soon. This results in a lower FVC than normal and when
interpreted, may suggest that the patient is restricted. Your
SDI spirometer is designed to give you an audible “beep”
when flow has reached a specific diminished threshold. The
spirometer will also alert you with an error message when it
sees an abrupt cessation of flow. Another key indicator
might be to note the FET (Forced Expiratory Time) that is
sometimes displayed as part of the data. If the time was
appreciably shorter than six seconds, this would suggest that
the patient ended the test too quickly.
1
European Respiratory Journal.
Standardisation of Spirometry
. Eur Resp J 2005; 26:319-338
.
2
Enright, Paul L., MD. How to Make Sure Your Spirometry Tests Are of Good Quality.
Respiratory Care
August 2003; 48:774.