Cosmed Quark PFT, Руководство пользователя

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Chapter 9 - Lung diffusing capacity - 85
Pressing the System… button, you can set the following options:
Option Description
System dead space Add the volume of the viral filter eventually used
O
2
concentration O
2
content of the used mixture (ATS 21%, ERS
17%)
Pressing the Patient… button, you can set the following options:
Option Description
Physiologic dead space calculation criterion (ATS=2.2*weight, manual)
Haemoglobin calculation criterion (ATS=14.6 adult men, 13.4
women and children)
Carboxyhaemoglobin digit the percentage value
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 DLCO cylinder is open and its output pressure is adjusted in the
range 5-6 bar.
DLCO with breath-hold (standard technique)
The Patient carry out a maximal inspiration of a mixture containing a low concentration
of CO (0.3%) and a tracer gas which is not metabolised (CH
4
, Methane); then he is
asked to breath hold for 10 seconds (the expiratory valve is kept closed) and finally he
is allowed to expire slowly up to the Residual Volume (the expiratory valve is opened).
Analysing the concentrations of CO and the Tracer gas (CH
4
) belonging to a portion of
the expired volume (collected volume) obtained by discarding the beginning of the
expiration (wash-out volume), the test indexes are determined.
The “wash-out volume” (0.75-1 L for normal subjects, 0.25-0.5 L with reduced Vital
Capacity ), the “collected volume” (0.5-1 L) and the calculation of the “breath hold
time” (ESP, JONES, OGILVIE) have been standardised by both ATS and ERS.
If fast response CO and CH
4
analysers are used it is possible to optimise the selection of
the “wash-out” and “collected” volumes according to the Vital Capacity of the subject.
This is usually achieved operating graphically on the CO/CH
4
graphs.
Repeating the DLCO test with different mixtures of inhaled gas it is possible to
separates the contributes of the alveolar membrane (Dm) and the Capillary Blood
Volume (Vc)
The main parameters of the DLCO test are:
DLCO
Lung Diffusing Capacity
DLCOcorr Lung Diffusing Capacity corrected for Hb, COHb and PB
VA Alveolar
Volume
DLCO/VA Krogh Index
Dm Alveolar Membrane
Vc Capillary Blood Volume
DLCO with apnoea (standard method)
1. Remove the sampling line from the flowmeter
2. Select
Single Breath CO diffusing capacity from the Test menu
3. Confirm or in case change the test options:
- Breath hold time
- Simulated test (it allows to carry out the manoeuvre without inhaling gas, useful
for teaching purposes)
- Hb (haemoglobin)
- Anatomic dead space