This is my 51st powerpoint..deals with PULMONARY FUNCTION TESTS..their uses...details on spirometry, lung volumes and capacities & brief insight into other tests.
Happy reading!!!
3. Refer to tests, that provide OBJECTIVE & QUANTIFIABLE
measures of LUNG FUNCTION
Useful in the DIAGNOSIS, EVALUATION & MONITORING
of respiratory disease/s
Also help to evaluate :
a. Response/ efficacy of ongoing therapy
b. Side-effects of medications, that lead to pulmonary disease.
5. Include:
A. DIAGNOSIS:
- Clinical manifestations of respiratory disease
- Follow-up of historical/lab findings
- Disease effects on pulmonary function
- Drug-induced pulmonary disorders.
B. EVALUATION:
- Medico-legal issues
- Rehabilitation
6. C. MONITORING:
- Respiratory disease progression
- Prognosis
- Occupational/ environmental exposure to toxins
- Therapeutic drug effectiveness
- Drug effects on pulmonary function.
8. - Test, that measures various aspects of breathing & lung function
- Standardization of spirometry regulated by ATS & ERS guidelines
- PROCEDURE OF SPIROMETRY:
a. Patient asked to breathe into a tube(mouth piece)
b. Mouth piece connected to a machine(spirometer)
c. Spirometer measures amount & flow of inhaled/ exhaled air
d. Physical forces of airflow + total amount of air inhaled/exhaled converted by
transducers to electrical signals displayed on a computer screen
e. Prior to conducting spirometry the technique involved SHOULD BE
EXPLAINED & DEMONSTRATED TO THE PATIENT
f. Since spirometry results depend on patient’s inhalation & exhalation
importance of COMPLETELY FILLING & EMPYTING THE LUNGS OF AIR
during the test should be emphasized!!
g. Nose clips should be worn during the test(to prevent air loss through nose!)
9.
10. - There are 2 types of SPIROMETRY SYSTEMS:
A. OPEN-CIRCUIT SYSTEM:
- In this patient has to INHALE BEFORE INSERTING THE MOUTH-PIECE
B. CLOSED-CIRCUIT SYSTEM:
- In this mouthpiece is first inserted patient takes several normal breaths,
before airflow is measured
11. - There are 2 TYPES of SPIROMETRY:
A. STATIC SPIROMETRY:
- Test, that is “VOLUME-BASED” & “SLOW”
B. DYNAMIC SPIROMETRY:
- Test, that is “TIME-BASED”
- Flow-dependant
- “FORCED”!!
13. Include:
1. VITAL CAPACITY(VC)
2. FORCED EXPIRATORY VOLUME(FEV)
3. FORCED EXPIRATORY FLOW(FEF)
- Via SPIROMETRY above values, & a FLOW-VOLUME CURVE are obtained
- FLOW-VOLUME CURVE:
a. Graphical representation of INSPIRATION & EXPIRATION
b. Also known as “flow-volume loops”.
14. VITAL CAPACITY:
- Includes:
a. FORCED VITAL CAPACITY(FVC)
b. SLOW VITAL CAPACITY(SVC)
- FVC refers to total volume of air EXHALED as HARD & as FAST as possible
after a MAXIMAL INHALATION
- Obtained from “DYNAMIC SPIROMETRY”
- SVC refers to total volume of air EXHALED as SLOW as possible, after a
MAXIMAL INHALATION
- SVC obtained from “STATIC SPIROMETRY”.
15. - In patients with NORMAL AIRWAY FUNCTION FVC &
SVC are usually similar
- In COPD patients there is trivial divergence!
- During initial stages of COPD FVC decreases before SVC
does!
16. FORCED EXPIRATORY VOLUME:
- Refers to the assessment of how much air a person can exhale during a FORCED
BREATH.
- Amounts of air exhaled may be measured after:
a. FEV0.5: 0.5 seconds
b. FEV1: 1 second(clinically significant, indicator of airway function!)
c. FEV3: 3 seconds
d. FEV6: 6 seconds, respectively.
- FEV1/FVC ratio used to estimate presence & amount of obstruction inside
airways
- In normal individuals exhalation is approximately 50 % of their FVC in the
first 0.5 seconds, 80% in 1 second & 98 % in 3 seconds.
- In patients with OBSTRUCTIVE DISEASE there is a decreased ratio (ratio
varies based on obstruction severity).
17. - According to ATS(American Thoracic Society), EPS(European Respiratory
Society) & GOLD(Global Initiative for Chronic Obstructive Lung Disease)
guidelines the following criteria is given for diagnosis & severity grading of
COPD:
a. If FEV1/FVC ratio < 70% indicates chronic obstruction(DIAGNOSIS)
b. For SEVERITY GRADING FEV1 values are noted:
• If FEV1 ≥ 80% : Mild-severity
• If FEV1 = 50-80% : Moderate severity
• If FEV1= 30-50% : Severe form of disease
• If FEV1< 30% : Very severe form of disease, respiratory failure.
18. FORCED EXPIRATORY FLOW:
- Measures AIRFLOW RATE during FORCED EXPIRATION
- Used to measure:
a. Flow of air in medium & small airways(bronchioles & terminal bronchioles)
b. To check for large obstructions in terminal bronchioles (as in acute severe
asthma).
19. PEAK EXPIRATORY FLOW RATE:
- Also known as “peak flow”
- Occurs within first milliseconds of expiratory flow
- Measures maximum airflow rate
- Measured using PEAK FLOW METERS
- Applications:
a. To evaluate for large airway obstruction
b. To determine severity of asthma exacerbation
- PEFR preferred over SPIROMETRY during exacerbation preferential
benefit!!!
20. DISEASE FEV1/FVC FEV1 FVC RV TLC
COPD Decreased Decreased Normal/decrease
d
Normal/Increase
d
Normal/Increase
d
Obstructive
Lung
Disease(Reversi
ble & Stable)
Normal Normal Normal Normal Normal
Restrictive Lung
Disease
Normal/Increase
d
Decreased Decreased Decreased Decreased
Combined
Obstructive &
Restrictive
Decreased/norm
al
Decreased Decreased Increased,
normal/decrease
d
Decreased
22. Body plethysmography refers to the method used to obtain LUNG VOLUME
MEASURES
Lung volumes indicate the amount of gas present in the lungs at various
stages of inflation
In body plethysmography patient is asked to sit inside an airtight box asked
to inhale & exhale against a closed shutter
Inside the box there will be a PRESSURE TRANSDUCER
PRESSURE TRANSDUCER measures pressure changes within the box during
respiration
In other words transducer measures the intrathoracic pressure generated
when the patient rapidly & forcefully puffs against the closed mouthpiece!!!
23.
24. - Above obtained details interpreted into Boyle’s Law:
“ P1 * V1 = P2 * V2”, where
“P1”: Pressure inside the box, when the patient is seated(atmospheric pressure)
“V1”: Volume of the box
“P2”: Intrathoracic pressure, generated by the patient
“V2”: Calculated volume of patient’s thoracic cavity.
- By using Boyle’s Law test provides a measure of FUCTIONAL RESIDUAL
CAPACITY(FRC)
27. 1. TIDAL VOLUME(TV):
- “Amount of air inhaled & exhaled at rest”
- TV = 0.5 litres
2. INSPIRATORY RESERVE VOLUME(IRV):
- “Additional volume of air, that a person can inhale (via forceful inspiration)”
- IRV = 3.1 litres
3. EXPIRATORY RESERVE VOLUME(ERV):
- “Additional volume of air, that a person can exhale(via forceful exhalation)”
- ERV = 1.2 litres.
28. 4. RESIDUAL VOLUME(RV):
- “Volume of air remaining in the lung, even after forceful exhalation”
- RV = 1.2 litres
33. Gas exchange tests help to measure ability of gases to diffuse across alveolar-
capillary membrane
Useful in assessing INTERSTITIAL LUNG DISEASES
Tests measure “PER MINUTE TRANSFER OF CO, FROM ALVEOLI TO
BLOOD”
Why is CO USED??
- CO is a gas that is uncommon inside the lung
- It has HIGH AFFINITY for HEMOGLOBIN in RBCs!!
• In the following conditions, diffusion capacity may be lessened:
a. Reduced surface area of alveoli
b. Thickening of alveolar-capillary membrane(due to infiltration of inflammatory
cells/ fibrotic changes)
34. Diffusion capacity of lungs to CO (DLCO) can be measured by either of the
following tests:
A. SINGLE BREATH TEST:
- In this test patient deeply inhales (upto vital capacity) , a mixture of 0.3 % CO,
10% helium & air patient is asked to hold breath for 10 seconds patient
exhales fully concentration of C0 & HELIUM are measured (during the end of
expiration)
- The concentration, so got compared with inspired concentration helps to
determine the amount diffusing across alveolar membrane
- Mean value for CO : 25-30 ml/min/ mm Hg
35. B. STEADY-STATE TEST:
- In this test patient breathes 0.1-0.2% concentration of CO for 5-6 minutes
- In the final 2 minutes expired gases are collected ABG is obtained
- Expired gas analyzed for total volume and concentrations of CO, CO2 & O2
- ABG analyzed for CO2
- Above values are used to calculate amount of gas transferred across alveolar
membrane per unit of time
- Females may have slightly lower values than males(due to slightly smaller lung
volumes in the former)
36. As said before diffusion capacity tests are used to assess gas exchange
Diffusion capacity is decreased in diseases that cause ALVEOLAR FIBROTIC
CHANGES, that include:
A. IDIOPATHIC CHANGES:
- Sarcoidosis
- Environmental/occupational disease(asbestosis, silicosis)
B. INDUCED CHANGES:
- Drugs (NTU, amiodarone, bleomycin).
38. Include:
A. BRONCHODILATOR STUDIES:
- In this test patient is asked to perform spirometry IMMEDIATELY BEFORE
& 15-30 MINUTES AFTER administration of an INHALED SHORT-ACTING
BETA-2 ADRENERGIC AGONIST
- According to ATS guidelines there will be a positive bronchodilator response,
signified by an improvement of:
i. FEV1 by 12%
ii. FVC by 200 mL.
39. B. BRONCHOPROVOCATION CHALLENGE TESTING:
- Also known as Bronchial provocation testing(BPT)
- Measures reactivity of airways to known concentrations of AGENTS that
INDUCE AIRWAY NARROWING
- In this test airways are challenged with increasing doses of provocative
agents, like:
i. Methacholine
ii. Histamine
iii. Adenosine
iv. Specific allergens
- Used to aid in the diagnosis of asthma(in conditions, where symptom history/
spirometry with reversibility, cannot confirm/ reject the diagnosis)
- Also helpful for studying the effect of drug therapy on airway hyperreactivity &
for research purposes.
40. C. EXERCISE CHALLENGE TESTING:
• Exercise-induced bronchospasm(EIB) occurs in majority of asthmatic patients
• Rapid breathing during exercise causes cooling & drying of airways can
lead to EIB
• Test is done to:
i. Confirm/ rule out EIB
ii. Evaluate effectiveness of medications used to treat/prevent EIB.
• Duration of exercise is AGE & TOLERANCE dependent
• Children < 12 years of age usually take 6 minutes
• Older children & adults take 8 minutes to complete the test.
• After the exercise is completed patient does “SERIAL SPIROMETRY”, at 5-
minute intervals, for 20-30 minutes FEV1 is monitored
• A 10-15% decline in FEV1 from baseline generally accepted as “abnormal
response”.
41. EXERCISE CHALLENGE TESTS USED FOR SCREENING
EIB:
METHOD ADVANTAGES DISADVANTAGES
Exercise bicycle Easily standardized, portable Relatively expensive
Treadmill Easily standardized Expensive
Free-running asthma screening
test
Familiar, inexpensive, most
asthmogenic
Not standardized, demerits of
running for 6-7 minutes, space
requirements.
Randolph C. Exercise-induced asthma: update on pathophysiology, clinical diagnosis, and treatment. Curr Probl Pediatr 1997;27:57.
43. - Test used to measure the distance a patient can walk on a FLAT, HARD
SURFACE in 6 minutes.
- Helps to predict morbidity & mortality for patients with CHF, COPD &
pulmonary HTN
- In this test patient is asked to WALK AS FAR AS POSSIBLE for 6 minutes
- Stopping & resting is allowed during the test
- Normal values include:
a. For ADULTS: 500-630 metres
b. For CHILDREN: 470 +/- 59 metres
- Contraindications include:
a. UA
b. MI (in past 1 month)
c. BP > 180/100 mm Hg!
44. To be precise 6MWT is used to assess amount of oxygen required for exertion
Patients with mild-moderate pulmonary disease may have normal oxygen
saturation at rest, but POOR SATURATION with EXERTION
If oxygen saturation is 88% or lower it requires need for supplemental
oxygenation!