Cosmed Quark PFT, Руководство пользователя

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76 - Quark PFT User Manual
Closing Volume Test (CV)
The Patient perform one single inspiration of 100% O2 following a maximal expiration
(RV level) and then expires smoothly through a breathing system able to measure both
the instantaneous N
2
concentration and expired flow.
The expired nitrogen is plotted on a N
2
/Volume graph from which test results are
obtained. The graph presents 4 different phases:
Phase I : The gas expired during Phase I represents the oxygen coming from the
dead volume of the measurement system and the upper airways not
interested by any distribution phenomenon.
Phase II: Shows the N
2
% rising belonging to the spaces connecting the upper
airways and the alveolar volume where the initial N
2
has be diluted with
the inspired oxygen. In this phase the Anatomic Dead Space is calculated
(Fowler method).
Phase III: It is called Alveolar Plateau . It shows the average N
2
concentration
resulting from the dilution of the air originally contained in the Residual
Volume with the inspired Oxygen. The slope of this plateau (about 1.5%
for normal subjects) is an useful index for assessing distribution disorders
(Patients affected by severe emphysema can reach 10% values).
Phase IV : The end of Phase III corresponds to the beginning of the so called
Closing Volume which represents the last section of the Vital Capacity
before the Residual Volume. The quick increase of the N2% belongs to
the emptying of the latest alveoli, richest of N
2
because not reached by the
inspired O
2
. Increased values of CV can be related to lung pathologies.
The main parameters calculated during this test are:
CV Closing Volume
Delta N
2
% Delta N
2
% between 750ml and 1250ml of expiration.
Recommendations
• The system must be calibrated before each test (See Calibration chapter)
•
The flowmeter must be connected properly to the breathing valve and the soft
mouthpiece must be properly fixed to the corresponding adapter.
•
Check that the O
2
cylinder is open and its output pressure is adjusted in the range 5-
6 bar.
Perform the test
1. Select Single Breath O
2
from the Test menu and wait for the green led is prompted
on the right side of the screen.
2. Connect the patient to the breathing valve and invite him/her to breathe normally.
3. Wait for the message “carry out Slow Vital Capacity” is prompted on the screen of
the PC and let the patient to perform a slow vital capacity.
4. Wait for a normal breathing pattern is again established and press Start (F2) during
a maximal exhalation.
5. Ask him/her to inspire up to TLC level and then to expire slowly maintaining the
flow rate as much constant as possible (two lines corresponding to 250ml/min and
500ml/min can be used as a target interval).
On the right side of the graph it is displayed a colored column, representing the
instantaneous flow. This column is green if the flow is within the acceptable range,
otherwise it is red.
6. The test stops automatically.
7. In order to visualise the graph and the main parameters press the follow buttons:
View CV graph.