Respirator Tolerance
PHILIP HARBER MD MPH
UCLA
P HARBER (2009) NPTL
WILL RESPIRATORS BE
EFFECTIVE?
• DEVICE MUST EFFECTIVELY
SUPPLY CLEAN ENOUGH AIR
• DEVICE MUST BE USED WHEN
AND WHERE NEEDED
P HARBER (2009) NPTL
QUESTIONS:
• CAN WORK CONTINUE IF
WIDESPREAD USE IS NEEDED?
• CAN PERSONS WITH MILD
RESPIRATORY DISEASES USE THEM?
• HOW DO 2 COMMON TYPES
COMPARE?
• WHAT IS BEST MEASURE OF “PUBLIC
HEALTH” EFFICACY?
P HARBER (2009) NPTL
TWO APPROACHES:
• DECISION ANALYSIS
• EXPERIMENTAL
P HARBER (2009) NPTL
DECISION ANALYSIS:
•
•
•
DEFINE KEY FACTORS &
RESPIRATOR
“TYPCAL” VALUES
ESTIMATE # OF PERSONS
SITES
OVERXPOSED
DETERMINE IMPACT OF
INCREMENTAL IMPROVEMENT
OF 1 FACTOR ON #
OVEREXPOSED
PROGRAM
PF
WPF
NUMBER OF SITES
WORKERS/SITE
SITES IDENTIFIED
SITE HAS A PROGRAM
PROPER SELECTION
RESPIRATOR AVAILABLE
PERSON
EVER USES
PROPORTION OF TIMES USED
EXPOSURE
EXPOSURE LEVEL
TYPICAL HAZARD LEVEL
VARIABILITY
% OUTLIERS
RESULTS
NO. ABOVE HAZARD LEVEL
DIFFERENCE
P HARBER (2009) NPTL
PUBLIC HEALTH: IMPROVE USER %
EFFECT OF CHANGE IN FACTOR TO OVEREXPOSED # (M OD RISK)
Typical
56,145
↑ WPF
55,883
↑ % Ever Users
53,708
↑ % Proper Use
46,492
Sensitive - outlier
60,530
Low WPF - outlier
56,413
0
20,000
40,000
60,000
80,000
# Ove re x pose d
P HARBER (2009) NPTL
EXPERIMENTAL
P HARBER (2009) NPTL
EXPERIMENTAL APPROACH
• COMPARE 2 RESPIRATOR TYPES
AND LABORATORY SURROGATES
► N95 ► DUAL CARTRIDGE HALF
MASK (HFM) ► INDIVIDUAL LOADS
• IN 4 USER GROUPS: NORMAL,
COPD, RHINITIS, ASTHMA
• WITH SIMULATED WORK & IN LAB
P HARBER (2009) NPTL
OUTCOME MEASURES
•
•
•
•
•
PHYSIOLOGIC RESPONSE
PHYSIOLOGIC ADAPTATION
WORK PRODUCTIVITY
MASK POSITION MOVEMENT
SUBJECTIVE RESPONSES (12)
P HARBER (2009) NPTL
P HARBER (2009) NPTL
HOW SHOULD SUBJECTIVE RESPONSE
BE MEASURED?
• ONE QUESTION IS NOT ENOUGH:
MULTIPLE SUBJECTIVE RESPONSES MUST
BE MEASURED
• 3 DISTINCT GROUPINGS OF RESPONSES: ►
"PHYSIOLOGIC SENSATION", ►
"FUNCTIONAL IMPACT", ► "MINIMAL"
16
Heavy
Comfort
Breathing
Face
Hot
Nose
Speech
Cncntrtn
Slippery
Wet
Vision
Hearing
15
14
13
12
11
10
9
8
7
6
Exlab
dsre
dsri
dsxx
mask
nlxxP
HARBER
rexx
rixx(2009) NPTL
HOW SHOULD PHYSIOLOGIC
RESPONSE BE MEASURED?
• ADAPTATION OF RESPIRATORY
PATTERN IS THE MOST CONSISTENT
EFFECT
3.50
0.70
3.00
0.65
Seconds
2.50
0.60
2.00
0.55
1.50
0.50
1.00
Ti:Tt Ratio
Tim e Param e te rs
Ti
Te
Tt
Ti/Tt
0.45
0.50
0.00
0.40
Tas k
bo lt
carr
case
driv
lego
m ags
m agw
sto r
P HARBER (2009) NPTL
HOW DO THE 2 RESPIRATOR
TYPES COMPARE?
• HFM PRODUCED MORE ADVERSE
SUBJECTIVE RESPONSE ON
MULTIPLE SCALES
• HFM PRODUCED GREATER
PHYSIOLOGIC ADAPTATION
IMPACT (ALBEIT LIMITED IN
MAGNITUDE)
P HARBER (2009) NPTL
IMPLICATIONS:
•
•
•
BOTH THE DECISION ANALYSIS AND EXPERIMENTAL
APPROACHES SUGGEST:
THERE IS A "TRADE-OFF" BETWEEN RESPIRATOR
PROTECTION FACTOR AND PROTECTION OF WORKERS!
I.E., HIGHLY PROTECTIVE RESPIRATORS THAT ARE NOT
USED MAY ACTUALLY BE LESS PROTECTIVE TO PUBLIC
HEALTH THAN LESS EFFECTIVE DEVICES THAT FAR BETTER
TOLERATED & MORE WIDELY AVAILABLE
SINCE WE DO NOT (YET) KNOW WHICH OUTCOMES ARE
MOST IMPORTANT, RESPIRATOR DESIGN & EVALUATION
SHOULD CONSIDER MULTIPLE DOMAINS: ►(PHYSIOLOGIC
IMPACT, ► RESPIRATORY ADAPTATION, ► MULTIPLE
SUBJECTIVE COMPONENTS, ► WORK PRODUCTIVITY, & ►
ACTUAL UTILIZATION)
P HARBER (2009) NPTL
THANK YOU!
P HARBER (2009) NPTL