1. PULMONARY FUNCTION TESTS Dr. Pooja Chopra

2. Lung Volumes and Capacities
PFT tracings have:
Four Lung volumes: tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual volume
Five capacities:, inspiratory capacity, expiratory capacity, vital capacity, functional residual capacity, and total lung capacity
Addition of 2 or more volumes comprise a capacity.

3. Lung Volumes
Tidal Volume (TV): volume of air inhaled or exhaled with each breath during quiet breathing (6-8 ml/kg)
Inspiratory Reserve Volume (IRV): maximum volume of air inhaled from the end-inspiratory tidal position.( ml)
Expiratory Reserve Volume (ERV): maximum volume of air that can be exhaled from resting end-expiratory tidal position.( ml).

4. Lung Volumes Residual Volume (RV):
Volume of air remaining in lungs after maximium exhalation (20-25 ml/kg) ( ml)
Indirectly measured (FRC-ERV)
It can not be measured by spirometry

5. Lung Capacities
Total Lung Capacity (TLC): Sum of all volume compartments or volume of air in lungs after maximum inspiration (4-6 L)
Vital Capacity (VC): TLC minus RV or maximum volume of air exhaled from maximal inspiratory level. (60-70 ml/kg) ( ml)
Inspiratory Capacity (IC): Sum of IRV and TV or the maximum volume of air that can be inhaled from the end-expiratory tidal position. ( ml).
Expiratory Capacity (EC): TV+ ERV

6. Lung Capacities (cont.)
Functional Residual Capacity (FRC):
Sum of RV and ERV or the volume of air in the lungs at end-expiratory tidal position.(30-35 ml/kg) ( ml).
Measured with multiple-breath closed-circuit helium dilution, multiple-breath open-circuit nitrogen washout, or body plethysmography.
It can not be measured by spirometry)

7. VOLUMES, CAPACITIES AND THEIR CLINICAL SIGNIFICANCE
TIDAL VOLUME (TV):
VOLUME OF AIR INHALED/EXHALED IN EACH BREATH DURING QUIET RESPIRATION.
N – 6-8 ml/kg.
TV FALLS WITH DECREASE IN COMPLIANCE, DECREASED VENTILATORY MUSCLE STRENGTH.
INSPIRATORY RESERVE VOLUME (IRV):
MAX. VOL. OF AIR WHICH CAN BE INSPIRED AFTER A NORMAL TIDAL INSPIRATION i.e. FROM END INSPIRATION PT.
N ml ml.

8. CONTINUED……… 3) EXPIRATORY RESERVE VOLUME (ERV):
MAX. VOLUME OF AIR WHICH CAN BE EXPIRED AFTER A NORMAL TIDAL EXPIRATION i.e. FROM END EXPIRATION PT.
N- 700 ml – 1000 ml
4) INSPIRATORY CAPACITY (IC) :
MAX. VOL. OF AIR WHICH CAN BE INSPIRED AFTER A NORMAL TIDAL EXPIRATION.
IC = IRV + TV
N-2400 ml – 3800 ml.

9. CONTINUED……….. 4) VITAL CAPACITY: COINED BY JOHN HUTCHINSON.
MAX. VOL. OF AIR EXPIRED AFTER A MAX. INSPIRATION .
MEASURED WITH VITALOGRAPH
VC= TV+ERV+IRV
N L. OR ml/kg
VC IS COSIDERED ABNORMAL IF ≤ 80% OF PREDICTED VALUE

10. FACTORS INFLUENCING VC
PHYSIOLOGICAL :
physical dimensions- directly proportional to ht.
SEX – more in males : large chest size, more muscle power, more BSA.
AGE – decreases with increasing age
STRENGTH OF RESPIRATORY MUSCLES
POSTURE – decreases in supine position
PREGNANCY- unchanged or increases by 10% ( increase in AP diameter In pregnancy)

11. CONTINUED……… PATHOLOGICAL: DISEASE OF RESPIRATORY MUSCLES
ABDOMINAL CONDITION : pain, dis. and splinting

12. FACTORS DECREASING VITAL CAPACITY
Alteration in muscle power- d/t drugs, n-m dis., cerebral tumours.
Pulmonary diseases – pneumonia, chronic bronchitis, asthma, fibrosis, emphysema, pulmonary edema,.
Space occupying lesions in chest- tumours, pleural/pericardial effusion, kyphoscoliosis
Abdominal tumours, ascites.

13. 5) Depression of respiration : opioids/ volatile agents
6) Abdominal splinting – abdominal binders, tight bandages, hip spica.
7)Abdominal pain – decreases by 50% & 75% in lower & upper abdominal Surgeries respectively.
8) Posture – by altering pulmonary Blood volume.

14. DIFFERENT POSTURES AFFECTING VC
POSITION
TRENDELENBERG
LITHOTOMY
PRONE
RT. LATERAL
LT. LATERAL
DECREASE IN VC
14.5%
18%
10%
12%

15. VC CONTINUED…….
VC correlates with capability for deep breathing and effective cough.
So in post operative period if VC falls below 3 times VC– artificial respiration is needed to maintain airway clear of secretions.

16. CONTINUED……. 6) TOTAL LUNG CAPACITY :
Maximum volume of air attained in lungs after maximal inspiration.
N- 4-6 l or ml/kg
TLC= VC + RV
7) RESIDUAL VOLUME (RV):
Volume of air remaining in the lungs after maximal expiration.
N – 2100 ml OR 20 – 25 ml/kg.

17. CONTINUED…… 8) FUNCTIONAL RESIDUAL CAPACITY (FRC):
Volume of air remaining in the lungs after normal tidal expiration, when there is no airflow.
N L OR ml/kg.
FRC = RV + ERV
Decreses under anaesthesia
with spontaneous Respiration – decreases by 20%
With paralysis – decreases by 16%

18. FACTORS AFFECTING FRC FRC INCREASES WITH Increased height
Erect position (30% more than in supine)
Decreased lung recoil (e.g. emphysema)
FRC DECREASES WITH
Obesity
Muscle paralysis (especially in supine)
Supine position
Restrictive lung disease (e.g. fibrosis, Pregnancy)
Anaesthesia
FRC does NOT change with age.

19. FUNCTIONS OF FRC Oxygen store
Buffer for maintaining a steady arterial po2
Partial inflation helps prevent atelectasis
Minimise the work of breathing
Minimise pulmonary vascular resistance
Minimised v/q mismatch - only if closing capacity is less than frc
Keep airway resistance low (but not minimal

20. Pulmonary Function Tests
The term encompasses a wide variety of objective tests to assess lung function
Provide objective and standardized measurements for assessing the presence and severity of respiratory dysfunction.

21. GOALS To predict the presence of pulmonary dysfunction
To know the functional nature of disease (obstructive or restrictive. )
To assess the severity of disease
To assess the progression of disease
To assess the response to treatment
To identify patients at increased risk of morbidity and mortality, undergoing pulmonary resection.

22. To wean patient from ventilator in icu.
GOALS, CONTINUED……..
To wean patient from ventilator in icu.
Medicolegal- to assess lung impairment as a result of occupational hazard.
Epidemiological surveys- to assess the hazards to document incidence of disease
To identify patients at perioperative risk of pulmonary complications

23. INDICATIONS OF PFT IN PAC
TISI GUIDELINES FOR PREOPERATIVE SPIROMETRY
Age > 70 yrs.
Morbid obesity
Thoracic surgery
Upper abdominal surgery
Smoking history and cough
Any pulomonary disease

24. INDICATIONS FOR PREOPERATIVE SPIROMETRY
ACP GUIDELINES FOR PREOPERATIVE SPIROMETRY
Lung resection
H/o smoking, dyspnoea
Cardiac surgery
Upper abdominal surgery
Lower abdominal surgery
Uncharacterized pulmonary disease(defined as history of pulmonary Disease or symptoms and no PFT in last 60 days)

25. BED SIDE PFT Sabrasez breath holding test:
Ask the patient to take a full but not too deep breath & hold it as long as possible.
>25 SEC.-NORMAL Cardiopulmonary Reserve (CPR)
15-25 SEC- LIMITED CPR
<15 SEC- VERY POOR CPR (Contraindication for elective surgery)
SEC ml VC
20 – 25 SEC ml VC
SEC ml VC
SEC ml VC
SEC ml VC

26. BED SIDE PFT 2) Single breath count:
After deep breath, hold it and start counting till the next breath.
N COUNT
Indicates vital capacity

27. BED SIDE PFT
3) SCHNEIDER’S MATCH BLOWING TEST: MEASURES Maximum Breathing Capacity.
Ask to blow a match stick from a distance of 6” (15 cms) with-
Mouth wide open
Chin rested/supported
No purse lipping
No head movement
No air movement in the room
Mouth and match at the same level

28. BED SIDE PFT Can not blow out a match Able to blow out a match
MBC < 60 L/min
FEV1 < 1.6L
Able to blow out a match
MBC > 60 L/min
FEV1 > 1.6L
MODIFIED MATCH TEST:
DISTANCE MBC
9” >150 L/MIN.
6” >60 L/MIN.
3” > 40 L/MIN.

29. BED SIDE TEST 4) COUGH TEST: DEEP BREATH F/BY COUGH ABILITY TO COUGH
STRENGTH
EFFECTIVENESS
INADEQUATE COUGH IF: FVC<20 ML/KG
FEV1 < 15 ML/KG
PEFR < 200 L/MIN.
VC ~ 3 TIMES TV FOR EFFECTIVE COUGH.
A wet productive cough / self propagated paraoxysms of coughing – patient susceptible for pulmonary Complication.

30. BED SIDE TEST
5) FORCED EXPIRATORY TIME: After deep breath, exhale maximally and forcefully & keep stethoscope over trachea & listen. N FET – 3-5 SECS. OBS.LUNG DIS. - > 6 SEC RES. LUNG DIS.- < 3 SEC

31. BED SIDE PFT
6) WRIGHT PEAK FLOW METER: Measures PEFR (Peak Expiratory Flow Rate) N – MALES L/MIN. FEMALES L/MIN. <200 L/ MIN. – INADEQUATE COUGH EFFICIENCY. 7) DEBONO WHISTLE BLOWING TEST: MEASURES PEFR. Patient blows down a wide bore tube at the end of which is a whistle, on the side is a hole with adjustable knob. As subject blows → whistle blows, leak hole is gradually increased till the intensity of whistle disappears. At the last position at which the whistle can be blown , the PEFR can be read off the scale.

32. MEASUREMENT OF TV & MV
8)Wright respirometer : measures tv, mv (15 secs times 4)
Simple and rapid
Instrument- compact, light and portable.
Disadvantage: It under- reads at low flow rates and over- reads at high flow rates.
Can be connected to endotracheal tube or face mask
Prior explanation to patients needed.
Ideally done in sitting pos.
MV- instrument record for 1 min. And read directly
TV-calculated and dividing MV by counting Respiratory Rate.
Accurate measurement in the range of l/min.(±10%)
USES: 1)BED SIDE PFT
2) ICU – WEANIG PTS. FROM Ventilation.

33. DEBONO’S WHISTLE

34. BED SIDE PFT
9) MICROSPIROMETERS – MEASURE VC. 10) BED SIDE PULSE OXIMETRY 11) ABG.

35. CATEGORIZATION OF PFT
MECHANICAL VENTILATORY FUNCTIONS OF LUNG / CHEST WALL:
A) STATIC LUNG VOLUMES & CAPACITIES – VC, IC, IRV, ERV, RV, FRC.
DYNAMIC LUNG VOLUMES –FVC, FEV1, FEF 25-75%, PEFR, MVV, RESP. MUSCLE STRENGTH
VENTILATION TESTS – TV, MV, RR.

36. CATEGORIZATION OF PFT 2) GAS- EXCHANGE TESTS:
A) Alveolar-arterial po2 gradient
B) Diffusion capacity
C) Gas distribution tests- single breath
N2 test.
- Multiple Breath N2 test
- Helium dilution method.
- Radio Xe scinitigram.
D) ventilation – perfusion tests
A) ABG
B) single breath CO2 elimination test
C) Shunt equation

37. CATEGORIZATION OF PFT 3) CARDIOPULMONARY INTERACTION:
A) Qualitative tests:
- History , examination
- Abg
- Stair climbing test
B) Quantitative tests
- 6 min. Walk test (gold standard)

38. STATIC LUNG VOLUMES AND CAPACITIES
SPIROMETRY : CORNERSTONE OF ALL PFTs.
John hutchinson – invented spirometer.
“Spirometry is a medical test that measures the volume of air an individual inhales or exhales as a function of time.”
Measures VC, FVC, FEV1, PEFR.
CAN’T MEASURE – FRC, RV, TLC.

39. PREREQUISITIES Prior explanation to the patient
Not to smoke /inhale bronchodilators 6 hrs prior or oral bronchodilators 12hrs prior.
Remove any tight clothings/ waist belt/ dentures
Pt. Seated comfortably
If obese, child < 12 yrs- standing

40. PREREQUISITES Nose clip to close nostrils.
Exp. Effort shld last ≥ 4 secs.
Should not be interfered by coughing, glottic closure, mechanical obstruction.
3 acceptable tracings taken & largest value is used.

41. SPIROMETER
Double walled cylinder with water to maintain water tight seal
Inverted bell (9 l) attached to pulley which carries a counterweight and pen – moves up and down as volume of bell changes
BREATHING ASSEMBLY i.E. Unidirectional breathing valves with mouth piece.

42. Flow-Volume Curves and Spirograms
Two ways to record results of FVC maneuver:
Flow-volume curve---flow meter measures flow rate in L/s upon exhalation; flow plotted as function of volume
Classic spirogram---volume as a function of time

43. Normal Flow-Volume Curve and Spirogram

44. Spirometry Interpretation: So what constitutes normal?
Normal values vary and depend on:
Height
Age
Gender
Ethnicity
Height varies directly with vc
VC increases with age up to age 20 years then becomes inversely proportion to age
Women usually with lower vc than men

45. Acceptable and Unacceptable Spirograms (from ATS, 1994)

46. Measurements Obtained from the FVC Curve
FEV1---the volume exhaled during the first second of the FVC maneuver
FEF 25-75%---the mean expiratory flow during the middle half of the FVC maneuver; reflects flow through the small (<2 mm in diameter) airways
FEV1/FVC---the ratio of FEV1 to FVC X 100 (expressed as a percent); an important value because a reduction of this ratio from expected values is specific for obstructive rather than restrictive diseases

47. Spirometry Interpretation: Obstructive vs. Restrictive Defect
Obstructive Disorders
Characterized by a limitation of expiratory airflow so that airways cannot empty as rapidly compared to normal (such as through narrowed airways from bronchospasm, inflammation, etc.)
Examples:
Asthma
Emphysema
Cystic Fibrosis
Restrictive Disorders
Characterized by reduced lung volumes/decreased lung compliance
Examples:
Interstitial Fibrosis
Scoliosis
Obesity
Lung Resection
Neuromuscular diseases
Cystic Fibrosis

48. Normal vs. Obstructive vs. Restrictive
(Hyatt, 2003)

49. Spirometry Interpretation: Obstructive vs. Restrictive Defect
Obstructive Disorders
FVC nl or↓
FEV1 ↓
FEF25-75% ↓
FEV1/FVC ↓
TLC nl or ↑
Restrictive Disorders
FVC ↓
FEV1 ↓
FEF 25-75% nl to ↓
FEV1/FVC nl to ↑
TLC ↓

50. Spirometry Interpretation: What do the numbers mean?
FVC
Interpretation of % predicted:
80-120% Normal
70-79% Mild reduction
50%-69% Moderate reduction
<50% Severe reduction
FEV1
Interpretation of % predicted:
>75% Normal
60%-75% Mild obstruction
50-59% Moderate obstruction
<49% Severe obstruction
<25 y.o. add 5% and >60 y.o. subtract 5

51. Spirometry Interpretation: What do the numbers mean?
FEF 25-75%
Interpretation of % predicted:
>79% Normal
60-79% Mild obstruction
40-59% Moderate obstruction
<40% Severe obstruction
FEV1/FVC
Interpretation of absolute value:
80 or higher Normal
79 or lower Abnormal

52. What about lung volumes and obstructive and restrictive disease?
(From Ruppel, 2003)

53. MEASUREMENTS OF VOLUMES
TLC, RV, FRC – MEASURED USING
Nitrogen washout method
Inert gas (helium) dilution method
Total body plethysmography

54. CONTINUED……….. 1) HELIUM DILUTION METHOD:
Patient breathes in and out of a spirometer filled with 10% helium and 90% o2, till conc. In spirometer and lung becomes same (equilibirium).
As no helium is lost; (as he is insoluble in blood)
C1 X V1 = C2 ( V1 + V2)
V2 = V1 ( C1 – C2) C2
V1= VOL. OF SPIROMETER
V2= FRC
C1= Conc.of He in the spirometer before equilibrium
C2 = Conc, of He in the spirometer after equilibrium

55. CONTINUED……… 2) TOTAL BODY PLETHYSMOGRAPHY:
Subject sits in an air tight box. At the end of normal exhalation – shuttle of mouthpiece closed and pt. is asked to make resp. efforts. As subject inhales – expands gas volume in the lung so lung vol. increases and box pressure rises and box vol. decreases.
BOYLE’S LAW:
PV = CONSTANT (at constant temp.)
For Box – p1v1 = p2 (v1- ∆v)
For Subject – p3 x v2 =p4 (v2 - ∆v)
P1- initial box pr. P2- final box pr.
V1- initial box vol. ∆ v- change in box vol.
P3- initial mouth pr., p4- final mouth pr.
V2- FRC

56. CONTINUED……… DIFFERENCE BETWEEN THE TWO METHODS:
In healthy people there is very little difference.
Gas dilution technique measures only the communicating gas volume.
Thus,
Gas trapped behind closed airways
Gas in pneumothorax
=> are not measured by gas dilution technique, but measured by body plethysmograph

57. CONTINUED……… 3) N2 WASH OUT METHOD:
Following a maximal expiration (RV) or normal expiration (FRC), Pt. inspires 100% O2 and then expires it into spirometer ( free of N2) → over next few minutes (usually 6-7 min.), till all the N2 is washed out of the lungs. N2 conc. of spirometer is calculated followed by total vol.of AIR exhaled. As air has 80% N2 → so actual FRC/RV is calculated.
E.g. Total vol. collected = 50 L (as N2 makes 80% of FRC on
room air)
Measured N2 = 5%
vol. of N2 in bag = 50 x .05 = 2.5L
2.5 L = X L
.80 FRC FRC
X = l (THIS IS PT’S FRC)

58. PROBLEMS WITH N2 WASH OUT METHOD
Atelectasis may result from washout of nitrogen from poorly ventilated lung zones (obstructed areas)
Elimination of hypoxic drive in CO2 retainers is possible
Underestimates FRC due to underventilation of areas with trapped gas

59. MEASUREMENT OF DYNAMIC LUNG VOLUMES
FEF25–75% = forced expiratory flow during expiration of 25 to 75% of the FVC; FEV1 = forced expiratory volume in the first second of forced vital capacity maneuver; FVC = forced vital capacity (the maximum amount of air forcibly expired after maximum inspiration).
TIMED EXPIRED SPIROGRAMS

60. FORCED VITAL CAPACITY (FVC)
Max vol. Of air which can be expired out as forcefully and rapidly as possible, following a maximal inspiration to TLC.
Exhaled volume is recorded with respect to time.
Indirectly reflects flow resistance property of airways.
Normal healthy subjects have VC = FVC.
Prior instruction to patients, practice attempts as it needs patient cooperation and effect.
Exhalation should take at least 4 sec and should not be interrupted by cough, glottic closure or mechanical obstruction.

61. FORCED VITAL CAPACITY IN 1 SEC. (FEV1)
Forced expired vol. In 1 sec during fvc maneuver.
Expressed as an absolute value or % of fvc.
N- FEV1 (1 SEC) % OF FVC
FEV2 (2 SEC)- 94% OF FVC
FEV3 (3 SEC)- 97% OF FVC

62. CONTINUED…… CLINICAL RANGE (FEV1) PATIENT GROUP 3 - 4.5 L 1.5 – 2.5 L
NORMAL ADULT
MILD – MOD.OBSTRUCTION
HANDICAPPED
DISABILITY
SEVERE EMPHYSEMA

63. CONTINUED……
FEV1 – Decreased in both obstructive & restrictive lung disorders. FEV1/FVC – Reduced in obstructive disorders. NORMAL VALUE IS 75 – 85 % (FEV1/FVC) < 70% OF PREDICTED VALUE – MILD OBST. < 60% OF PREDICTED VALUE – MODERATE OBST. < 50% OF PREDICTED VALUE – SEVERE OBST.

64. CONTINUED…… DISEASE STATES FVC FEV1 FEV1/FVC OBSTRUCTIVE NORMAL ↓
2) STIFF LUNGS
3 ) RESP. MUSCLE WEAKNESS

65. PEAK EXPIRATORY FLOW RATE (PEFR)
It is the max. Flow rate during fvc maneuver in the initial 0.1 sec.
-PEFR DETERMINED BY : 1) Function of caliber of airways
2) Expiratory muscle strength
3) Pt’s coordination & effort
- Estimated by 1) drawing a tangent to steepest part of FVC spirogram (error prone)
2) average flow during the litre of gas expired after initial 200 ml during fvc maneuver. .

66. Normal value in young adults (<40 yrs)= 500l/min
Measured with pneumotachograph / Wright peak flow meter
Wright peak flow meter - valuable tool in identifying gross pulmonary Disability at bedside.
-Less unpleasant & less
Exhaustive
Clinical significance - values of <200/l- impaired coughing & hence likelihood of post-op complication

67. FORCED MID-EXPIRATORY FLOW RATE (FEF25%-75%):
Maximum Mid expiratory Flow rate
Max. Flow rate during the mid-expiratory part of FVC maneuver.
Effort independent
Misnomer, as FEF25-75% decreased by
1) marked reduction in exp. Effort
2)submaximal inspiration b4 maneuver → ↓FVC → ↓ FEF25-75%
It may decrease with truly max. Effort as compared to slightly submaximal effort as dynamic airway compression occurs with maximal effort.
N value – l/sec. Or 300 l/min.
Upto 2l/sec- acceptable.
CLINICAL SIGNIFICANCE: SENSITIVE & IST INDICATOR OF OBSTRUCTION OF SMALL DISTAL AIRWAYS

68. MAXIMUM BREATHING CAPACITY: (MBC/MVV)
MAX. VOLUNTARY VENTILATION
Largest volume that can be breathed per minute by voluntary effort , as hard & as fast as possible.
N – l/min.
Estimate of max. Ventilation available to meet increased physiological demand.
Measured for 12 secs – extrapolated for 1 min.
MVV = FEV1 X 35

69. CONTINUED…….
Discrepancy b/w FEV1 and MVV means inconsistent / submaximal inspiratory effort
MBC/MVV altered by- airway resistance
- Elastic property
-Muscle strength
- Learning
- Coordination
- Motivation

70. RESPIRATORY MUSCLE STRENGTH
Evaluated by measuring max. Static resp. Pressure with anaeroid gauge
Pressures are generated against occluded airway during a max. Forced insp/exp. Effort
MAX STATIC INSP. PRESSURE: (PIMAX)-
Measured when inspiratory muscles are at their optimal length i.e. at RV
PI MAX = -125 CM H2O
CLINICAL SIGNIFICANCE:
IF PI MAX< 25 CM H2O – Inability to take deep breath.

71. CONTINUED……. MAX. STATIC EXPIRATORY PRESSURE (PEMAX):
Measured after full inspiration to TLC
N VALUE OF PEMAX IS =200 CM H20
PEMAX < +40 CM H20 – Impaired cough ability
Particularly useful in pts with NM Disorders during weaning

72. PHYSIOLOGICAL DETERMINANTS OF MAX. FLOW RATES
1)DEGREE OF EFFORT- driving pressure generated by muscle contraction (PEmax & PI max)
ELASTIC RECOIL PRESSURE OF LUNG: (PL)
Tendency to recoil or collapse d/t PL
PL increases from RV (2-3) to TLC (20-30)
Opposed by Pcw (recoil pr. Of chest wall)
Prs=Pl + Pcw = 0 at FRC-resting state
(Prs-recoil pr.of resp.system)
3) AIRWAY RESISTANCE: (Raw):
Determined by the calibre of airways
Decreases as lung vol increases (hyperbolic curve)
Raw high at RV & low at TLC

73. Continued…… DISEASE MSL. STRENGTH Raw PL N-M WEAKNESS ↓ N EMPHYSEMA
ASTHMA/BRONCHI
TIS ↑
PERIPHERAL AIRWAY DIS.

74. MEASUREMENT OF AIRWAY RESISTANCE
1) Raw- Body plethysmography
2) Forced expiratory maneuvers:
Peak expiratory flow (PEF)
FEV1
3) Response to bronchodialtors (FEV1)

75. Spirometry Pre and Post Bronchodilator
Obtain a flow-volume loop.
Administer a bronchodilator.
Obtain the flow-volume loop again a minimum of 15 minutes after administration of the bronchodilator.
Calculate percent change (FEV1 most commonly used---so % change FEV 1= [(FEV1 Post-FEV1 Pre)/FEV1 Pre] X 100).
Reversibility is with 12% or greater change.

76. AIRWAY PARTITIONING AND BEHAVIOUUR
UPPER (EXTRATHORACIC)
Surrounding soft tissue unsupporting
Collapses during inspiration
Expands during expiration
INTRATHORACIC
Outer surface exposed to pleural pressure
Expands during inspiration
Collapses during expiration
DISTAL (PULMONARY)
Intimately related to lung tissue
Collapses as expiration proceeds

77. FLOW VOLUME LOOPS
Do FVC maneuver and then inhale as rapidly and as much as able.
This makes an inspiratory curve.
The expiratory and inspiratory flow volume curves put together make a flow volume loop.

78. Flow-Volume Loops
(Rudolph and Rudolph, 2003)

79. How is a flow-volume loop helpful?
Helpful in evaluation of air flow limitation on inspiration and expiration
In addition to obstructive and restrictive patterns, flow-volume loops can show provide information on upper airway obstruction:
Fixed obstruction: constant airflow limitation on inspiration and expiration—such as in tumor, tracheal stenosis
Variable extrathoracic obstruction: limitation of inspiratory flow, flattened inspiratory loop—such as in vocal cord dysfunction
Variable intrathoracic obstruction: flattening of expiratory limb; as in malignancy or tracheomalacia

80. TESTS FOR GAS EXCHANGE FUNCTION
1) ALVEOLAR-ARTERIAL O2 TENSION GRADIENT:
Sensitive indicator of detecting regional V/Q inequality
N value in young adult at room air = 8 mmhg to upto 25 mmhg in 8th decade (d/t decrease in PaO2)
AbN high values at room air is seen in asymptomatic smokers & chr. Bronchitis (min. symptoms)
PAO2 = PIO2 – PaCo2 R

81. CONTINUED…….. 2) DYSPNEA DIFFENRENTIATION INDEX (DDI):
To d/f dyspnea due to resp/ cardiac d’s
DDI = PEFR x PaCO2
1000
DDI- Lower in resp. pathology

82. CONTINUED……
3) DIFFUSING CAPACITY OF LUNG: defined as the rate at which gas enters into bld. divided by its driving pr. DRIVING PR: gradient b/w alveoli & end capillary tensions. Fick’s law of diffusion : Vgas = A x D x (P1-P2) T D= diffusion coeff= solubility √MW

83. CONTINUED……. DL IS MEASURED BY USING CO, COZ:
High affinity for Hb which is approx. 200 times that of O2 , so does not rapidly build up in plasma
Under N condition it has low bld conc ≈ 0
Therefore, pulm conc.≈0

84. SINGLE BREATH TEST USING CO
Pt inspires a dilute mixture of CO and hold the breath for 10 secs.
CO taken up is determined by infrared analysis:
DlCO = CO ml/min/mmhg
PACO – PcCO
N range ml/min./mmhg.
DLO2 = DLCO x 1.23

85. Emphysema, lung resection, pul. Embolism, anaemia
DLCO decreases in-
Emphysema, lung resection, pul. Embolism, anaemia
Pulmonary fibrosis, sarcoidosis- increased thickness
DLCO increases in:
(Cond. Which increase pulm, bld flow)
Supine position
Exercise
Obesity
L-R shunt

86. TESTS FOR CARDIOPLULMONARY INTERACTIONS
Reflects gas exchange, ventilation, tissue O2, CO.
QUALITATIVE- history, exam, ABG, stair climbing test
QUANTITATIVE- 6 minute walk test

87. CONTINUED……. 1) STAIR CLIMBING TEST: 2) 6 MINUTE WALK TEST:
If able to climb 3 flights of stairs without stopping/dypnoea at his/her own pace- ↓ed morbidity & mortality
If not able to climb 2 flights – high risk
2) 6 MINUTE WALK TEST:
Gold standard
C.P. reserve is measured by estimating max. O2 uptake during exercise
Modified if pt. can’t walk – bicycle/ arm exercises
If pt. is able to walk for >2000 feet during 6 min pd,
VO2 max > 15 ml/kg/min
If 1080 feet in 1 min : VO2 of 12ml/kg/min
Simultaneously oximetry is done & if Spo2 falls >4%- high risk

88. EVALUATION OF PT. FOR LUNG RESECTION
GOALS:
1) to identify pts at risk of increased post-op morbidity & mortality
2) to identify pts who need short-term or long term post-op ventilatory support.
Lung resection may be f/by – inadequate gas exchange, pulm HTN & incapacitating dyspnoea.

89. CONTINUED…..
Removal of entire lung is likely to be tolerated if pre-op pulm function meets the following criteria:
A) FEV1 > 2 L or FEV1/FVC of atleast 50%
B) MVV > 50% of predicted value
C) RV/ TLC < 50%
If any of these criteria is not full filled – go for more invasive & sophisticated, split lung function tests.

90. CONTINUED……
A predicted post op FEV1 Of atleast 800ml is required to perform pneumonectomy
If not- risk of significant resting CO2 retention & dyspnoea is high.
IF Sx inevitable – invasive tests : Pulmonary artery occlusion test
If after occlusion of pulm artery of segment to be resected is not followed by pulm Htn ( mean pulm art pr > 35 mmhg) AND hypoxemia(PaO2 <45 mmhg) – Assure that remaining lung can accommodate entire C.O.

91. THANKYOU