no oh, mama mia, mama mia, mama mia, let me go freddy mercury, 1975
TRANSCRIPT
NONO
NONO
NONO
NO
Oh, mama mia, mama mia, mama mia, let me go
Freddy Mercury, 1975
Analysis of Exhaled Nitric Oxide for Patients with
Asthma
Paul Enright, MDThe University of Arizona
Outline
Background Indications Methods Interpretation Summary References
Background
1991 – eNO first measured by Gustafsson 1993 – eNO found elevated in asthmatics
Kjell Alving – Karolinska Institute
Guidelines 1997 ERS 1999 ATS 2005 ATS+ERS
>1200 eNO publications
eNO is an index of eosinophilic airway inflammation.
eNO is not increased with bronchospasm.
eNO = FENO *
* The abbreviation for ivory tower physiologistsFraction of exhaled nitric oxide at a flow of 50mL/sec
0.05
Indications
Confirm asthma Differentiate asthma from COPD Guide inhaled corticosteroid therapy
Predict ICS response (& non-response)
Monitor ICS compliance Titrate ICS daily dose (step-up, step-down)
A high eNO confirms asthma in children with recurrent wheeze
Normal range5-30 ppb
Saito J, JACI 2005
Asthma vs. COPD
A few COPD patients also have eosinophilic inflammation.A few asthma patients have no eosinophilic inflammation.
Fabbri, AJRCCM 2003
eNO remains normal during COPD exacerbations
0
10
20
p<0.001
p<0.01
Smokers COPD
Exh
aled
NO
(p
pb
)
stable unstable
Normal range5-30 ppb
Maziak, AJRCCM 1998
eNO >50ppb predicts ICS response
much better than does spirometry
Hi
ROC curve from Smith, AJRCCM 2005
OptimaleNO
cut-point
FEV1 BDResponse
ICSs suppress airway inflammation,so eNO falls rapidly with ICS therapy.
100 µg/day
400 µg/day
placebo
Kharitonov, ERJ 2000
7 days on ICS 7 days off ICS
Good asthma controlGreen zone
Poor asthma controlYellow-orange zone
ICS dose : eNO response
Silkoff, Chest 2001
BeclomethasoneQVAR DPI
low – med – highdaily ICS dose
ICSnaive
A reduction in eNO suggests good compliance with ICS therapy
eNO fell in half
Beck-Ripp, ERJ 2002
Good %Poor
ICS Compliance
eNO to titrate ICS dosewhile maintaining good asthma
control
Smith, NEJM 2005
A high daily ICS
dosewhilst
following NAEP
guidelines
Future Indications
Guide prednisone tapers Determine Singulair efficacy ? Determine chronic cough cause Epidemiological surveys Occupational asthma
surveillance
Singulair pills lower eNO in some patients with asthma
Sandrini, Chest 2003
one week
Singulair vs.ICS responses
Szefler AJRCCM 2005. CARE, a multi-center, NIH-funded study
• 55% no response• 17% respond to both• 23% respond only to ICS (predicted by higher eNO)• 5% respond only to Singulair 126 children with mild to moderate asthma, crossover, 8 wk study
Correlates
Bronchial responsiveness Methacholine PC-20
Eosinophils (count and %) Induced Sputum Blood BAL and lung biopsy
Lung function (FEV1)
eNO correlates with airway biopsy indices of inflammation
Van den Toorn AJRCCM 2001
Symptomatic
no symptoms
MBP = major basic protein
ppb
21 ICS-naive adolescentswith asthma
Good correlations with blood IgE
Saito J, JACI 2005
An epi study of 278 Japanese school children
Poor correlation with FEV1
Saito J, JACI 2005
Advantages of eNO
Immediate results A painless and easy maneuver Effort independent Entirely safe No sample processing Predicts and measures ICS
response
Disadvantages
Expensive instrument No reimbursement (yet)
Doesn’t measure bronchospasm
Methods
On-line Single, slow exhalations Multiple exhalations
with 5 different flows (MEFT) central versus peripheral
5 minute tidal breathing
Off-line Nasal NO (+ humming for sinusitis)
Online eNO sampling assembly
mouthpiece
Ambient air inspired
Exhalation resistor
Sample to NO analyzer
to pressure gauge for feedback
Filter removesAmbient NO
eNO signals during testing
5-20cmH2O
50 mL/sec
Ignore the peak
Report the plateau value
Offline eNO sampling
Tedlar or Mylarbacteria-freeballoon
It’s okay to include dead space exhalate
Measure samples within 12 hours.
Pre-test preparations
Avoid ETS exposure for 2 hours Avoid meals, drinks, smoking, exercise for 1
hr No spirometry or BD in prior 30 min Determine smoking status
Any cigarettes in last week? Consider exhaled CO confirmation
Determine asthma controller use Ask about recent viral URIs Ask ICS, Singulair, & prednisone last 2 weeks
ATS+ERS 2005
Step-by-step testing sequence
1. Don’t use nose-clips
2. Deep inhalation of NO-free air
3. Don’t pause at TLC
4. Slow exhalation for >6 seconds *
5. Discard dead space
6. Wait >30sec, repeat 2 or 3 times
* 3 sec okay for preschool kids
Quality Assurance
Verify analyzer accuracy daily 100-400ppb calibration gas
Exclude nasal and sinus NO Maintain back-pressure of 5-20cmH2O Display target pressure (display or gauge) Dynamic resistor preferred
Discard dead space gas if on-line Report mean value during flat plateau
Quality Assurance (continued)
Maintain target exhalation rate Standard: 50 mL/sec
Repeat maneuvers until eNOs match Goal: 3ppb or 5% match
Report the mean eNO and flow Rates of acceptable results
70% children ages 4-8 90% adults
ATS+ERS 2005
Effect of exhalation flow
eNO will be underestimated if the subject exhales too fast.
standardtarget
ATS+ERS 2005
Effect of recent smoking
eNO will be underestimated if the subject was smoking recently
Robbins, Chest 1995
3ppb short-term repeatability
Kharitonov, ERJ 2003
• No learning effect• No diurnal variation
Repeatability: children vs adults
The eNO coefficient of variability (CV%)is about 5% in healthy adults and about 10% in children.
Your name here
Instruments
Chemiluminescence Sievers (now GE Analytical, USA) Aerocrine NIOX (Sweden) * Eco Medics (Switzerland) Logan Research (UK)
Electrochemical (very new) Hand-held, no vacuum pump Can’t measure multiple rates
Enright’s conflict of interest statement:Aerocrine bought dinner for me 3 times
NIOX
Instrument Specifications
• Sensitivity: 1 ppb• Accuracy: better than 1 ppb• Repeatability: better than 1 ppb• Range: 1-500 ppb• Signal to noise: better than 3:1
ATS+ERS guidelines 2005
Instrument differences
Muller KC, Respir Med 2005
“Differences due to calibration procedures”
L, M, & H were 3 German biologic control subjects, tested once per day after a re-calibration
EcoMedics CLD88
Reimbursement
Aerocrine obtained FDA 510k pre-marketing approval for its NIOX model in 2003.
An AMA-CPT code for the test was awarded Dec 2005, with reimbursement expected 2007.
Meanwhile, you can charge patients directly for the test.
Interpretation
Consider the pre-test probability Consider the major confounders
Cigarette smoking Asthma controller medication use Nitrate-rich diet
High or low values may be abnormal >30ppb indicates out-of-control asthma <5ppb (very low) may indicate PCD Normal values increase with age in children
eNO in healthy children
Upper limit of the normal range
Mean values
Buchvald 2003
Response rates to ICS therapy
eNO begins to fall within 3-5 days
FEV1
Methacholine
Saito J, JACI 2004
Summary
eNO measures allergic airway inflammation
eNO is a fast, safe, & easy test eNO is standardized and highly repeatable eNO determines ICS need and response In asthma, eNO is complementary to FEV1
Nasal NO during humming detects sinus blockage
Maniscalso, ERJ 2003
Very high nasal NO from sinuses during humming
Low nasal NO with blocked sinus drainage
Recommended Reading
ATS+ERS guidelines, AJRCCM 2005; 171:912 Kharitonov SA, Swiss Med Wkly 2004; 134: 175 Smith AD, Curr Opin Allergy Clin Imm 2005; 5:49 Malmberg LP, J Asthma 2004; 41:511 Smith AD, NEJM 2005; 352(21):2163 Aerocrine, “Scientific Backgrounder” booklet, 2005