what test measure RV
Helium dilution test (FRC)
nitrogen washout (FRC)
body plethsmography (TLC)
explain helium dilution test
-closed circuit
-under the assumption pt doesnt have helium in lungs and doesnt get absorbed into bloodstream stays in lungs
-pt is instructed to breath normally and at the end of normal exhalation they are connect to the curcit ,after pt rebreathes gas insider spirometer (600mLw 10% helium) pt exhales ,CO2 is removed using CO2 absorbent and helium remains and dilutes until equalibrium it reached
-normally takes 2-5 mins
-severe pulmonary diseased takes 20 mins
what is FRC
amount of air in the lungs after normal expiration (ERV+RV)
define what nitrogen washout test is
-nonrebreather or open circuit
-based off N2 concentration in the lungs is 78%
-pt inhales 100%O2 and the O2 replaces all the N2 in lungs, nitrogen is washout and measured by nitrogen analyzer
-complete washout is 7mins
-FRC=Ve x FeN2/.78-FaN2
define fractional exhaled nitric oxide
-breath out slowly into device for 8 seconds
-test how much inflammation a pt has in lungs
levels:
N: 25ppb
intermediate: 26-50ppb
high: >50ppb
explain plethysograpy
-boyles law
-measures the volume of compressible gas in the thorax, including gas trapped behind airway obstruction or in the pleural space
- pt breaths normally, then shallow pantings, shutter closes and they breath against resistance, instucted to exhale to ERV then maximal inhale VC
what gas is normally used in the Diffusion capacity test
carbon monoxide (CO)
-very high affinity for Hb and diffused rapidly into the pulmonary blood keeping pulmonary capillary pressue of CO near zero
important steps to get accurate results for DLCO
-pt seated for 5 mins
-pt should exhale to RV usually 6 seconds
-pt should be able to inspire 90% of their Vc in 4 seconds
-omce pt reaches max inspiration they should hold their breath for 9-11 seconds
-exhalation should be rapid with total exhalation lasting 4 seconds
indications for DLCO
- evaluation of parenchymal lung disease associated with dust or drug reactions or related sarcoidosis
- evaluation and follow up of emphysema or cystic fibrosis
-diffrentaion amoung chronic bronchitis,emphysema, asthma
-those who have undergone chemotherapy
contraindications 0f DLCO
-mental confusion or incoordination
-large meals or exercise before
-smoking with 24 hrs of test
factos that affect DLCO
1.body position
2. activity
3. PaO2
4.Hb and carboxyhemoglobin
decreased DLCO
1.pulmonary fibrosis
2.sarcoidosis
3.ARDS
4. pulmonary edema
5.emphysema (only obstructuve disease)
6. anemia
increased DLCO
1.polycythemia
2.exercise
3.CHF
when performing DLCO
- intervals of 4 mins bw repeated test
2.no more than 5 single breaths - DLCO Hb value for adult male 14.6%
- Hb value for women 13.4%
what is the average DLCO value for adults
25-40mLCO/min/mmHg
*decreased in restrictive lung disease especially pulmonary fibrosis
