anesthetic implications of lung volumes, capacities and pulmonary functions

1. LUNG VOLUMES AND CAPACITIES
AND PULMONARY FUNCTION TESTS
Presenter : Dr. Rajesh Munigial
Moderator : Dr. Meena Padmaja
HOD : Dr. Arun Kumar A
SSIMS & RC , DAVANAGERE

3. Physiology Of Respiration
• INSPIRATION
Contraction of diaphragm causes caudal
displacement of central tendon resulting in
longitudinal expansion of chest cavity.

4. EXPIRATION
Expiration is a passive process because of the
elastic recoil of the lungs and chest wall.
Forced expiration is by the internal intercostal
and abdominal muscles.
Contraction of abdominal muscles→↑ the intra
abdominal pressure→cephaloid movement of the
diaphragm.

5. • RIBS AND MUSCLES OF INSPIRATION
Diaphragm
External intercostal muscles –
inspiration
- bucket handle movement
Accessory respiratory muscles
1. For inspiration – sternocleidomastoid
,scalene and pectoralis
1. For expiration – abdominal muscles (
rectus abdominis , external and
internal oblique and transversus ) and
internal intercostal muscles

6. Compliance = stretchability
CL = Change in lung volume
Change in transpulmonary pressure
Normal value : 150-200 mL/cm H2O
Factors affecting :
1. Lung volume
2. Pulmonary blood volume
3. Extravascular lung water
4. Pathological conditions ( inflammation and fibrosis)

7. TWO TYPES : STATIC AND DYNAMIC
• STATIC COMPLIANCE : It is measured when the flow
of air has ceased, as during breath holding or during
apnea in anaesthesia.
• DYNAMIC COMPLIANCE:
When the volume change of the thorax in relation to
pressure changes is measured during respiration it is
known as dynamic compliance.
Dynamic compliance is always less than or equal to static
lung compliance

9. LUNG VOLUMES
• TIDAL VOLUME : volume of air inspired and
expired with each normal breath , it is about
6-8ml/kg . (500 ml in adult male)
• INSPIRATORY RESERVE VOLUME : extra
volume of air that can be inspired over and
above the normal tidal volume when the
person inspires with full force , it is usually
40ml/kg (3000ml).

10. • EXPIRATORY RESERVE VOLUME : IT IS THE
MAXIMUM extra volume of air that can be
expired by forceful expiration after the end of
normal tidal expiration . It is about 20ml/kg
• RESIDUAL VOLUME : the volume of the air
remaining in the lungs after most forceful
expiration . It is about 15ml/kg.

11. LUNG CAPACTIES
• Inspiratory capacity : Total amount of air that can be inspired after a tidal
expiration (IRV + TV) = 3500ml
• Functional residual capacity : amount of air remaining in the lungs after a
tidal expiration (RV + ERV) = 2300 ml
• Vital capcity :the maximum volume of air that can be exhaled after a
maximal expiration.(TV + IRV + ERV) = 4600ml
• Total lung capacity: – sum of all lung volumes (approximately 6000 ml in
males)
• All pulmonary volumes and capacities are usually about 20-25% less in
women than in men , they are greater in large and athletic people than in
small and asthenic people .

12. Pulmonary volumes Normal values (ml)
Tidal volumes 500
Inspiratory reserve volume 3000
Expiratory reserve volume 1100
Residual volume 1200
Pulmonary capacities Normal values (ml)
Inspiratory capacity 3500
Functional residual capacity 2300
Vital capacity 4600
Total lung capacity 5800

13. SPIROMETRY
• Pulmonary ventilation can be studied by recoding the volume movement
of air into and out of the lungs by a method called SPIROMETRY.
• Changes in lung volume can be recorded on sheet of paper called
spirogram

15. TYPES OF SPIROMETERS
• Bellows spirometers:
Measures volume; mainly in lung function
units
• Electronic desk top spirometers:
Measure flow and volume with real time
display
• Small hand-held spirometers:
Inexpensive and quick to use.

16. VOLUME MEASURING SPIROMETER

17. FLOW MEASURING SPIROMETER

18. Small Hand-held Spirometers

19. MEASUREMENT OF TIDAL AND MINUTE
VOLUMES DURING ANAESTHESIA
Wright respirometer –
• allows the instrument to record for one minute.
• Minute volume measured directly
• Tidal volume can be calculated from this reading
and the respiratory rate.

20. WRIGHT
RESAPIROMETER :
Compact and light
Used to measure
minute volume.
Offers an accurate
assessment of the
patient’s minute
volume(+/– 10%)
within range of 3.7 to
20 L/min.

21. RESIDUAL VOLUME :
Increase in RV signifies that lung is larger than usual and
cannot empty adequately.
Increase in RV usually associated with air-trapping in lungs.
Increase is seen in obstruction to airway as in asthma,
thoracic surgeries.
In Severe emphysema- air is trapped completely in the
alveoli and never comes in contact with the respired gases.

22. LOSS OF VITAL CAPACITY :
• Trendelenburg position : 14.5 %
• Lithotomy position : 18%
• Left lateral position : 10%
• Right lateral position : 12%
• Prone position : 10%

23. SIGNIFICANCE OF VITAL CAPACITY
DURING ANAESTHESIA
 Reductions in the vital capacity become important in the post
operative period when the expulsion of secretions may be
• seriously impeded.
 If it falls below about 3 times the tidal volume, artificial help
may be needed to maintain the airways clear of excessive
secretions.
EXAMPLES :
• . Tension pneumothorax, large haemothorax ,diaphragmatic hernia
,exopthalmos in the new born, neuromuscular diseases and upper
respiratory obstruction

24. Functional Residual Capacity
• Volume of air remaining in lungs after normal
tidal expiration, when there is no airflow .
• Normal 2.3 -3.3 l or 30-35ml/kg
• Frc = rv + erv
• Decreases under anesthesia
• With spontaneous respiration decreases by 20
%
• With paralysis decreases by 16%

25. FACTORS AFFECTING FRC
INCREASES
Increased height
• Erect position
• Decreased lung recoil
• ASTHMA
• CHRONIC BRONCHITIS
• APPLICATION OF PEEP
DECREASES
• Obesity
• Muscles paralysis
• Spine position
• Restrictive lung disease
• Anaesthesia
• PULMONECTOMY

26. Functions of FRC
• Oxygen store
• Buffer for maintaining a steady arterial po2
• Partial inflation helps preventing atelectasis
• Minimise the work of breathing
• Minimised v/q mismatch
• Keep aiway resisitance low

27. Measurement of FRC
• Measured by 3 methods;
1. Nitrogen technique
2. Helium dilution method
3. Body plethysmography

28. Nitrogen wahshout technique

29. Principle - to collect all the nitrogen that can be
washed out of patient’s lungs
Following a maximal expiration or normal
expiration, the patient inspires oxygen from a
special source and then expires into a
spirometer which is free of nitrogen.
After some minutes almost all of the alveolar
nitrogen is washed out of lungs.

30. • In healthy adults this may be achieved by 2
minutes.
• In patients with severe emphysema 20 minutes
may be needed.
• Concentration of nitrogen in spirometer is
measured.
• The difference in nitrogen volume at the initial
concentration and at the final exhaled
concentration allows a calculation of intrathoracic
volume, usually FRC.

31. Helium dilution method
 A spirometer of known volume is filled with air mixed
with helium at a known concentration.
 Before breathing from the spirometer, the person
expires normally.
 At the end of this expiration, the remaining volume in
the lungs is equal to the functional residual capacity.
 At this point, the subject immediately begins to
breathe from the spirometer, and the gases of the
spirometer mix with the gases of the lungs.

32. from this V2( FRC) can be calculated,
V2 =V1* C1-C2/C2

33. Once the FRC has been determined, the residual
volume (RV) can be determined.
Also, the total lung capacity (TLC) can be
determined by adding the inspiratory capacity
(IC) to the FRC.
That is, RV = FRC – ERV
TLC = FRC + IC

34. BODY PLETHYSMOGRAPHY
• Plethysmography (derived from greek word meaning
enlargement). Based on principle of BOYLE’S LAW(P*V=k)
• A patient is placed in a sitting position in a closed body box
with a known volume
• The patient pants with an open glottis against a closed
shutter to produce changes in the box pressure proportionate
to the volume of air in the chest.
• As measurements done at end of expiration, it yields FRC

36. Closing capacity
As the lungs become reduced in volume during
expiration there comes a point at which some small
airways begin to close.
And therefore prevent any further expulsion of gas
from related alveoli.
Due to this “air trapping” occurs.
 Lung volume at which this phenomenon can first be
detected is CC.

37. • The volume above RV at which airways begin
to close during expiration is called closing
volume(CV).
• The sum of RV and CV is called closing
capacity(CC)
• RV+CV = CC

39. CLOSING CAPACITY
can be measured using single breath nitrogen –washout technique.
while breathing, the subject slowly expires to residual volume
and then slowly takes a single breath of oxygen to maximum
inhalation
breath is held for a few seconds and then slowly and evenly expired.
during this phase the instantaneous nitrogen concentration and
volume of the expired concentration are recorded.

40. This will give us a
characteristic curve
having four phases
1. dead space gas
2. mixed dead space and
alveolar gas
3. mixed alveolar gas
from all alveoli
4. phase in which there
is sudden rising
concentration of
nitrogen
5. the CC is the volume
at which phase 4
begins.

41. RELATION BETWEEN FRC AND CC
• If the CC rises above the FRC, some airways
will be closed during part, or later whole of
the normal range of ventilation.
• As a result the blood passing through the
closed areas of lung will not be fully
oxygenated.
• Arterial po2 will fall.

42. o In people with normal lungs, CC becomes equal to FRC
in the 60’s and in the 40’s in supine position.
o Later CC continues to rise as age increases and the
arterial po2 begins to fall.
o Rise in CC is seen in smokers, obesity, rapid iv infusion,
LVF, following MI and postoperatively.
o It is increased after surgery and may be an important
factor in the genesis of post operative hypoxemia.
o Use of PEEP raises arterial po2 by raising the FRC above
CC

43. Altered physiologic conditions :
During Anaesthesia
• Gas exchange is altered by shunt and
inhomogenous VQ ratio.
Normal range of po2 can be maintained if alveolar
po2 is atleat 200mmhg which requires fio2 of
atleast 35%.
Within 5 min of induction in dependent region of
lungs incresed density with increased atelectasis
is seen due to compression of lung tissue

45. • POSITION
• During deep anesthesia diaphragm flaccid
som VQ mismatch is more
• Apply peep to mitigate the effect
• Matching Is superior in prone than in supine
position

46. OBESITY

47. Obesity
• Restrictive ventilatory pattern
• Decrease in FRC leads to increase venoarterial
shunting and a tendency to desaturate during
induction and maintainence of anesthesia in
postop period
• Peep eliminates atelectasis in morbid obese
• Challenge is to minimise fall in FRC
• Avoid long acting NMR’s , positioning and
postop cpap

48. Age :
• Newborns and infants
• Overall compliance is low in newborns and
increases till adolescence.
• Alveoli at birth have less elastin and less
surfactant
• But compliance of chest wall is very high due
to absence of ossification of cartilages which
leads to decreased frc during anesthesia .

49. • In awake state FRC is maintained above CC in
infants by increase in RR
• All airways are proportionately smaller which
leads to incresed resistance leading to
increased work of breathing mainly during
infections (croup)

50. ELDERLY:
• lung elastic recoil
• in o2 diffusion capacity
• in vital capacity
• in FEV1 and FVC
• in lung compliance
• residual volume
• in FRC
• in CC at greater rate
• in intrapulmonary shunting

52. Pulmonary function tests
1.Bedside pulmonary function tests
2. Static lung volumes and capacities
3. Measurement of FRC, RV
4. Dynamic lung volumes/forced spirometry
5. Flow volume loops and detection of airway
obstruction
6. Flow volume loop and lung diseases
7. Tests of gas function
8. Tests for cardiopulmonary reserve

53. REASONS TO USE PFT :
• Screening for the presence of obstructive and restrictive diseases
• Evaluating the patient prior to surgery
• Evaluating the patient's condition for weaning from a ventilator. If the
patient on a ventilator can demonstrate a vital capacity (VC) of 10 - 15
ml/Kg of body weight, it is generally thought that there is enough
ventilatory reserve to permit (try) weaning and extubation.
• Documenting the progression of pulmonary disease - restrictive or
obstructive
• Documenting the effectiveness of therapeutic intervention

55. Bed side PFT
1) sabrazer breath holding test:
Reveals Cardiopulmonary And Ventilatory
Capcaity Status
• Ask the patient to take a full but not too deep
breath & hold it as long as possible
• > 25 sec normal cardiopulmonary reserve
• 15-25 sec limited cardiopulmonary reserve
• < 15 sec very poor cardiopulmonary reserve

56. 2) Single breath test
• After deep breath , hold it and start counting
till the next breath
• Normal – 30 -40 count
• Indicates vital capacity

57. 3) Schneider’s match blowing test :
measures maximum breathing capacity
• Ask to blow a match stick from a distance of 6” (15cm)
• Cannot blow out a match
• MBC < 6ol/min
• Fev 1 <1.6 l
Able to blow a match
mbc > 60l/min
Fev1 > 1.6l/min
Modified match test :
DISTANCE MBC
9” >150L/MIN
6” > 60 L/MIN
3” >40L/MIN

58. COUGH TEST
4) COUGH TEST : ability to cough
• Strenghth
• Effectivess
Inadequate cough
FEV < 20ml/kg
fev < 15ml/kg
Pefr < 200l/min
Vc – 3 times TV for effective cough

59. 5) Forced expiratory time
• After deep beath , exhale maximally ad
forcefully and keep stethscope over trachea an
listen
• Normal 3-5sec
• Obs lung disease > 6 sec
• Res lung disease < 3 sec

60. 6) DE-BONO 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.

61. DEBONO’S WHISTLE

62. GAS EXCHANGE TESTS
• Alveolar arterial po2 gradient
• Diffusion capacity
• Gas distribution tests : single breath
• N2 test
• Multiple breath n2 test
• Helium dilution test
• Radio Xe scintigram
• Ventilation perfusion test
Abg
Single breath co2 elimination test
Shunt equation

63. Forced vital capacity
Max vol. Of air which can be expired out as forcefully and rapidly as possible,
following a maximal inspiration to TLC.
Characterized by full inspiration to TLC followed by abrupt onset of expiration to
RV
Indirectly reflects flow resistance property of airways.

64. • Interpretation of % predicted:
• 80-120% Normal
• 70-79% Mild reduction
• 50%-69% Moderate reduction
• <50% Severe reduction

66. Measurement obtained from fvc
curve
• FEV1 ---the volume exhaled during the first second of
the FVC maneuver
• FEV 25-75%---the mean expiratory flow during the
middle half of the FVC maneuver; reflects flow through
the small (<2mm 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

68. Spirometry interpretations in obstructive
and restrictive disorders
• • 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 ↓

69. PEAK EXPIRATORY FLOW RATES
Maximum flow rate during an FVC maneuver
occurs in initial 0.1 sec
After a maximal inspiration, the patient
expires as forcefully and quickly as he can and
the maximum flow rate of air is measured.
It gives a crude estimate of lung function,
reflecting larger airway function.
 Effort dependent but is highly reproducible

70. PEFR
It is measured by a peak flow
meter, which measures how much
air (litres per minute)is being
blown out or by Spirometry
The peak flow rate in normal
adults varies depending on age
and height.
 Normal : 450 - 700 l/min in
males
300-500 l/min in females
 Clinical significance - values of
<200L/min- impaired coughing &
hence likelihood of post-
opcomplication

72. FLOW VOLUME LOOPS
• “Spirogram” Graphic analysis of flow at various lung
volumes
• Tracing obtained when a maximal forced expiration
from TLC to RV is followed by maximal forced
inspiration back to TLC
• Measures forced inspiratory and expiratory flow rate
• Principal advantage of flow volume loops vs. typical
standard spirometric descriptions - identifies the
probable obstructive flow anatomical location.

73. FLOW VOLUME
LOOPS
 First 1/3rd of expiratory flow
is effort dependent and the final
2/3rd near the RV is effort
independent
 Inspiratory curve is entirely
effort dependent
 Ratio of maximal expiratory
flow(MEF)/maximal inspiratory
flow(MIF) mid VC ratio and is
normally 1

74. RESTRICTIVE OBSTRUCTIVE

75. Fixed obstruction:
constant
Flow-volume loops
provide information on
upper airway
obstruction:
airflow limitation on
inspiration and
expiration—such as
1. Benign stricture
2. Goiter
3. Endotracheal
neoplasms
4. Bronchial stenosis

76. Variable intrathoracic
obstruction
flattening of expiratory limb.
1.Tracheomalacia
2. Polychondritis
3. Tumors of trachea or main bronchus
During forced expiration – high pleural
pressure – increased intrathoracic
pressure - decreases airway diameter.
The flow volume loop shows a greater
reduction in the expiratory phase
During inspiration – lower pleural
pressure around airway tends to
decrease obstruction

77. Variable extrathoracic
obstruction
1.Bilateral and unilateral vocal cord
paralysis
2. Vocal cord constriction
3. Chronic neuromuscular disorders
4. Airway burns
5. OSA
 Forced inspiration- negative transmural
pressure inside airway tends to collapse
it
Expiration – positive pressure in airway
decreases obstruction
 inspiratory flow is reduced to a greater
extentthan expiratory flow

79. TESTS FOR GAS EXCHANGE
• ALVEOLAR-ARTERIAL O2 TENSION GRADIENT:
• Sensitive indicator of detecting regional V/Q inequality
• AbN high values at room air is seen in asymptomatic
• smokers & chr. Bronchitis (min. symptoms)
• A-a gradient = PAO2 - PaO2
• * PAO2 = alveolar PO2 (calculated from the alveolar
• gas equation)
• * PaO2 = arterial PO2 (measured in arterial gas

80. DIFFUSING CAPACITY

81. DIFFUSING CAPACITY
• Rate at which gas enters the blood divided by its driving
pressure ( gradient – alveolar and end capillary tensions)
• Measures ability of lungs to transport inhaled gas from
alveoli to pulmonary capillaries
• Normal- 20-30 ml/min/mm Hg
• Depends on:
• - thickness of alveolar—capillary membrane
• - hemoglobin concentration
• - cardiac output

82. 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
• DLO2 = DLCO x 1.23
• Why CO?
• A)High affinity for Hb which is approx. 200 times that of O2
,so does not rapidly build up in plasma
• B) Under N condition it has low bld conc ≈ 0
• C) Therefore, pulm conc.≈0

83. • The DLCO is low in ILD,but normal in disorders
of pleura, chest and neuromuscular disorder
causing restrictive lung function.
• DLCO is also useful for following the course of
or response to therapy in ILD.

84. Factors affecting dlco
Decreased (<80% predicted) Increased (> 120-140% predicted )
Anemia polycythemia
Carboxyhemoglobin Exercise
Pulmonary embolism Congestive heart failure
Diffuse pulmonary fibrosis
Pulmonary emphysema

85. References :
• Guyton and hall : textbook of medical
physiology second edition
• Stoelting pharmacology and physiology in
anesthesia practice 5th edition

86. THANK YOU !!!