3. What is Spirometry?
Spirometry is a method of assessing lung
function by measuring the volume of air
the patient can expel from the lungs after
a maximal expiration by spirometer and
shows a relationship between volume and
time as call spirogram.
PFT for PT 3
6. Indications for spirometry
1) Diagnosis
- to evaluate symptoms, sign or abnormal laboratory test
- to measure the effect of disease on lung function
- to screen individuals at risk of having pulmonary disease
- to assess preoperative risk
- to assess prognosis
- to assess health status before enrollment in strenuous
physical activity
PFT for PT 6
7. Indications for spirometry
2) Monitoring
- to assess therapeutic intervention
- to monitor persons in occupations with exposure to
injurious agents
3) Disability/ impairment evaluation
- to assess patients as part of rehabilitation program
- to assess individual for legal reason
4) Public health
- epidemologic surveys
PFT for PT 7
15. การตรวจวัดการทางานของปอด
การตรวจแบ่งเป็น 2 ลักษณะคือ
1. การตรวจวัดปริมาตรและความจุดปอด (Tests of lung
volume and capacity)
VT, IRV, ERV, RV
FRC, IC, VC, TLC
1. การตรวจวัดอัตราการไหลของอากาศ (Tests of air flow
rate)
FVC, RFEV1, FEF 25%-75% , PEFR, MVV
PFT for PT 15
16. Tests of lung volume and capacity
*Volume: VT, IRV, ERV, RV
*Capacity: FRC, IC, VC, TLC
PFT for PT 16
17. Tidal volume (TV)
It is the volume of air inspired or expired with each
breath during normal breathing ( 7ml/kg) 400-700ml
TV decreased in severe RLD
PFT for PT 17
18. Inspiratory Reserve Volume (IRV):
It is the maximal volume of air inspired with
effort in excess of tidal volume
IRV: From TV to TLC
PFT for PT 18
19. Expiratory reserve volume (ERV):
It is the maximal volume of air exhaled from the resting
end-expiratory level. Volume expired by active expiration after
passive expiration.
ERV: From TV to RV
ERV decreased in RLD
PFT for PT 19
20. Residual volume (RV)
It is the volume of air remaining in the lungs at the end of maximal
expiration. Normally it accounts for about 25% of TLC.
- RV increased in airway narrowing with air trapping (B.Asthma) or
in loss of elastic recoil (emphysema).
- RV decreased in Increased elastic recoil (pulmonary fibrosis)
PFT for PT 20
21. Functional Residual Capacity (FRC)
It is the volume of air remaining in the lungs at the end of resting
(normal) expiration.
FRC = RV + ERV.
-FRC Increased (>120% of predicted) in Emphysema (decreased elastic recoil),
B.Asthma, bronchiolar obstruction (air trapping)
-FRC decreased in intrinsic ILD or by upward movement of diaphragm (obesity,
painful thoracic or abdominal wound)
PFT for PT 21
22. Inspiratory capacity (IC):
It is the maximal volume of air inspired from resting expiratory
level
IC= IRV+TV.
PFT for PT 22
23. Vital Capacity: volume of gas measured on complete expiration after
complete inspiration without effort
VC= TLC – RV or
VC= IRV+TV+ERV
decreased in OLD and RLD
( VC < 15 ml/kg (and VT < 5ml/kg) indicates likely need for mechanical
ventilation
PFT for PT 23
24. Total Lung Capacity (TLC)
It is the total volume of air within the lung after maximum inspiration. (the
maximum volume of air that the lung can contain).
TLC = FVC + RV OR
TLC = RV + ERV + TV + IRV
TLC Increased in airway narrowing with air trapping (B.Asthma) or
in loss of elastic recoil (emphysema).
TLC Decreased in RLD , increased recoil (Pulmonary fibrosis), muscle weakness,
Obesity…
PFT for PT 24
26. Tests of air flow rate
• FVC - Forced vital capacity:
The total volume of air that can be forcibly exhaled in one breath
RM strength, Lung compliance, Airway
FVC decrease in OLD and RLD
Duration of expiration: OLD . RLD เพราะการขยายตัวลาบากมีแนวโน้มถูกบีบ
ตัวเข้า
PFT for PT 26
27. Tests of air flow rate
• FEV1 - Forced expiratory volume in one second:
The volume of air expired in the first second of the blow
FRV1 decrease in OLD at trachea or bronchi
PFT for PT 27
28. Tests of air flow rate
• FEV1/FVC ratio:
The fraction of air exhaled in the first second relative to the total
volume exhaled
*This value is critically important in the diagnosis of obstructive and
restrictive diseases
PFT for PT 28
29. FEF25%
Amount of air that was forcibly
expelled in the first 25% of the total
forced vital capacity test.
FEF75%
The amount of air expelled from the
lungs during the first (75%) of the
forced vital capacity test.
FEF25%-75%
The amount of air expelled from the
lungs during the middle half of the
forced vital capacity test.
** Small peripheral airways
PFT for PT 29
30. Flow-volume loops
F-V loop is a plot of
inspiratory and
expiratory flow in the
vertical axis against
volume in the
horizental axis, during
the performance of
maximally forced
inspiratory and
expiratory maneuvers.
PFT for PT 30
31. • The contour of the loop assists in the diagnosis and
localization of airway obstruction as different lung
disorders produce distinct ,easily recognized pattern.
PFT I 31
32. Peak expiratory flow rate (PEFR)
It is the maximum flow rate that can be forced during expiration
Used to assess the improvement or deterioration in the
disease as well as the effectiveness of treatment
**especially, upper and large airways
PEFR < 100 L/min: severe
PEFR 100-200 L/min: moderate
PEFR > 200 L/min: mild
36. Maximum voluntary ventilation
• This measures the greatest amount of air you
can breathe in and out during one minute.
• Deep and rapid inspirited in 15 second
• MVV = TV x RR = FEV1 x 35
• Normal MVV ~ 160-180 L/min
**RM strength and endurance
PFT for PT 36
45. Acceptability Criteria
free from artifacts:
Cough or glottis closure
during the first second of
exhalation
Early termination or cutoff
Variable effort
Leak
Obstructed mouthpiece
Have good starts
Have a satisfactory
exhalation 6 s of exhalation
PFT II 45
47. Reproducibility Criteria
After 3 acceptable spirograms been obtained
Are the two largest FVC within 200ml of each
other?
Are the two largest FEV1 within 200ml of each
other?
If both of these criteria are met, the test session
may be concluded.
If both of these criteria are not met, continue
testing until Both of the criteria are met with
analysis of additional acceptable spirograms; OR a
total of eight tests have been performed
PFT II 47
52. 3. การจาแนกความรุนแรงของความผิดปกติ
Obstructive abnormality
FEV1/VC below normal range
severity
Mild % predict FEV1 < 100 and ≥ 70
Moderate % predict FEV1 < 70 and ≥ 60
Moderately severe % predict FEV1 < 60 and ≥ 50
Severe % predict FEV1 < 50 and ≥ 34
Very severe % predict FEV1 < 34
PFT for PT Source: Am Rev Respir Dis 1991; 144: 1212-18. 52
53. 3. การจาแนกความรุนแรงของความผิดปกติ
Restrictive abnormality
Reduction in VC without reduction of FEV1/VC
severity
Mild % pred VC < LLN but ≥ 70
Moderate % pred VC < 70 but ≥ 60
Moderately severe % pred VC < 60 but ≥ 50
Severe % pred VC < 50 but ≥ 34
Very severe % pred VC < 34
PFT for PT Source: Am Rev Respir Dis 1991; 144: 1212-18. 53
75. Conclusions
• Spirometry defines obstructive and restrictive
lung diseases
• Highly reproducible test
• Needs to be performed accurately to ensure
useful data
• Courses available to train operators
• Highly valuable in the clinical setting