1. University of GeziraUniversity of Gezira
Faculty of MedicineFaculty of Medicine
Physiology departmentPhysiology department
Batch 8Batch 8
Pulmonary function testPulmonary function test
Presented by:Presented by:
Dr Mogahed HusseinDr Mogahed Hussein
2. ObjectivesObjectives
Explain General principles that help understanding lung V & CExplain General principles that help understanding lung V & C
Explain lung V & c to ease the concept of PFTExplain lung V & c to ease the concept of PFT
Explain bedside PFTExplain bedside PFT
Explain how spirometry measures lung volumes and airflow inExplain how spirometry measures lung volumes and airflow in
patientspatients
Explain how we measure RV, FRC, TLC indirectly withExplain how we measure RV, FRC, TLC indirectly with
spirometer.spirometer.
4. Control of BreathingControl of Breathing
RESPIRATORY
CENTRE (Medulla)
MEDULLARY &
CAROTID
CHEMORECEPTORS
Higher Control
Centres
RESPIRATORY
REFLEXES
DRUG EFFECTS e.g.
OPIATES &
CAFFEINE
CRANIAL & SPINAL
MOTOR NEURONES
STRETCH &
PROPRIOCEPTORS
LUNGS & CHEST WALL
INSPIRATION
7. ChemoreceptorsChemoreceptors
Medulla Oblongata and Carotid BodyMedulla Oblongata and Carotid Body
Respond to changes in pH, CORespond to changes in pH, CO22 and Oand O22
Resetting of carotid chemoreceptors occurs at birth inResetting of carotid chemoreceptors occurs at birth in
response to oxygenationresponse to oxygenation
Not essential at initiation of respiration but used forNot essential at initiation of respiration but used for
control of breathingcontrol of breathing
Responses are weak in the immediate newborn periodResponses are weak in the immediate newborn period
and in preterm babiesand in preterm babies
8. DefinitionsDefinitions
Minute volume = vol. of gas each minuteMinute volume = vol. of gas each minute
200 – 400 mL/kg/min200 – 400 mL/kg/min
Minute volume = Tidal volume x resp. rateMinute volume = Tidal volume x resp. rate
PaCO2 inverselyPaCO2 inversely ∝∝ MVMV
PaCO2PaCO2 ↓↓ byby ↑ tidal volume or ↑ resp. rate↑ tidal volume or ↑ resp. rate
Dead Space = Vol. of lung not involved in ventilation (eg,Dead Space = Vol. of lung not involved in ventilation (eg,
airways and ET tubes)airways and ET tubes)
9. ComplianceCompliance
Compliance is a measure of the dispensability of the lungCompliance is a measure of the dispensability of the lung
Compliance =Compliance = Change in Volume (L)Change in Volume (L)
Change in Pressure (cm HChange in Pressure (cm H22O)O)
Lung disease decreases complianceLung disease decreases compliance
RDSRDS (Alveolar collapse)(Alveolar collapse)
Fluid in insterstitiumFluid in insterstitium
Lung fibrosisLung fibrosis
Pneumothorax (Lung compression)Pneumothorax (Lung compression)
Surfactant improves complianceSurfactant improves compliance
10. Airways ResistanceAirways Resistance
Measure of the pressure gradient needed for gas to flowMeasure of the pressure gradient needed for gas to flow
through a tubethrough a tube
Airway resistance =Airway resistance = Pressure differencePressure difference
(R(RAWAW)) Gas flowGas flow
• Poiseuilles’ equationPoiseuilles’ equation
• RRAWAW ∝∝ airway lengthairway length
• RRAWAW ∝∝ 1/ radius1/ radius44
11. Work of BreathingWork of Breathing
Energy required to produce change in lung volumeEnergy required to produce change in lung volume
Increases with decreased complianceIncreases with decreased compliance
Increases with increased resistanceIncreases with increased resistance
If energy required to breath exceeds capacity to supplyIf energy required to breath exceeds capacity to supply
oxygen to provide that energy then respiratory failureoxygen to provide that energy then respiratory failure
develops requiring mechanical ventilationdevelops requiring mechanical ventilation
15. Lung Volumes and CapacitiesLung Volumes and Capacities
PFT tracings have:PFT tracings have:
Four Lung volumes: tidalFour Lung volumes: tidal
volume, inspiratoryvolume, inspiratory
reserve volume,reserve volume,
expiratory reserveexpiratory reserve
volume, and residualvolume, and residual
volumevolume
Five capacities:,Five capacities:,
inspiratory capacity,inspiratory capacity,
expiratory capacity, vitalexpiratory capacity, vital
capacity, functionalcapacity, functional
residual capacity, andresidual capacity, and
total lung capacitytotal lung capacity
Addition of 2 or more volumes comprise a capacity.
16. Lung VolumesLung Volumes
Tidal VolumeTidal Volume (TV):(TV): volume ofvolume of
air inhaled or exhaled withair inhaled or exhaled with
each breath during quieteach breath during quiet
breathing (6-8 ml/kg)breathing (6-8 ml/kg)
Inspiratory Reserve VolumeInspiratory Reserve Volume
(IRV):(IRV): maximum volume of airmaximum volume of air
inhaled from the end-inhaled from the end-
inspiratory tidal position.(1900-inspiratory tidal position.(1900-
3300ml)3300ml)
Expiratory Reserve VolumeExpiratory Reserve Volume
(ERV):(ERV): maximum volume ofmaximum volume of
air that can be exhaled fromair that can be exhaled from
resting end-expiratory tidalresting end-expiratory tidal
position.( 700-1000ml).position.( 700-1000ml).
17. Lung VolumesLung Volumes
Residual VolumeResidual Volume (RV):(RV):
Volume of airVolume of air
remaining in lungsremaining in lungs
after maximumafter maximum
exhalation (20-25exhalation (20-25
ml/kg) (1700-2100ml)ml/kg) (1700-2100ml)
Indirectly measuredIndirectly measured
(FRC-ERV)(FRC-ERV)
It can not beIt can not be
measured bymeasured by
spirometerspirometer
18. Lung CapacitiesLung Capacities
Total Lung CapacityTotal Lung Capacity (TLC):(TLC):
Sum of all volumeSum of all volume
compartments or volume of aircompartments or volume of air
in lungs after maximumin lungs after maximum
inspiration (4-6 L)inspiration (4-6 L)
Vital CapacityVital Capacity (VC):(VC): TLCTLC
minus RV or maximum volumeminus RV or maximum volume
of air exhaled from maximalof air exhaled from maximal
inspiratory level. (60-70 ml/kg)inspiratory level. (60-70 ml/kg)
(3100-4800ml)(3100-4800ml)
Inspiratory CapacityInspiratory Capacity (IC(IC):):
Sum of IRV and TV or theSum of IRV and TV or the
maximum volume of air that canmaximum volume of air that can
be inhaled from the end-be inhaled from the end-
expiratory tidal position. (2400-expiratory tidal position. (2400-
3800ml).3800ml).
Expiratory Capacity (EC)Expiratory Capacity (EC):: TV+TV+
ERVERV
19. Lung Capacities (cont.)Lung Capacities (cont.)
Functional ResidualFunctional Residual
CapacityCapacity (FRC):(FRC):
Sum of RV and ERV or theSum of RV and ERV or the
volume of air in the lungs atvolume of air in the lungs at
end-expiratory tidalend-expiratory tidal
position.(30-35 ml/kg)position.(30-35 ml/kg)
(2300-3300ml).(2300-3300ml).
Measured with multiple-Measured with multiple-
breath closed-circuit heliumbreath closed-circuit helium
dilution, multiple-breathdilution, multiple-breath
open-circuit nitrogenopen-circuit nitrogen
washout, or bodywashout, or body
plethysmography.plethysmography.
It can not be measured byIt can not be measured by
spirometry)spirometry)
21. 1)1) TIDAL VOLUME (TV):TIDAL VOLUME (TV):
Volume of air inhaled or exhaled with each breath duringVolume of air inhaled or exhaled with each breath during
quiet breathing (6-8 ml/kg)quiet breathing (6-8 ml/kg)
Compliance and muscle strengthCompliance and muscle strength
2)2) VITAL CAPACITY:VITAL CAPACITY:
Measured with VITALOGRAPHMeasured with VITALOGRAPH
22. FACTORS INFLUENCING VCFACTORS INFLUENCING VC
PHYSIOLOGICALPHYSIOLOGICAL ::
physical dimensions- directly proportional to height.physical dimensions- directly proportional to height.
SEX – more in males : large chest size, more muscle power. **SEX – more in males : large chest size, more muscle power. **
AGE – decreases with increasing age**AGE – decreases with increasing age**
Muscle strength.Muscle strength.
POSTURE – decreases in supine position – by altering pulmonaryPOSTURE – decreases in supine position – by altering pulmonary
Blood volume.**Blood volume.**
PREGNANCY- unchanged or increases by 10% ( increase in APPREGNANCY- unchanged or increases by 10% ( increase in AP
diameter In pregnancy)diameter In pregnancy)
24. 5) Depression of respiration : opioids5) Depression of respiration : opioids
6) Abdominal splinting – abdominal binders, tight6) Abdominal splinting – abdominal binders, tight
bandages.bandages.
7)Abdominal pain – decreases by 50% & 75% in lower &7)Abdominal pain – decreases by 50% & 75% in lower &
upper abdominal Surgeries respectively.**upper abdominal Surgeries respectively.**
25. CONTINUED……CONTINUED……
3) FUNCTIONAL RESIDUAL CAPACITY (FRC):3) FUNCTIONAL RESIDUAL CAPACITY (FRC):
Volume of air remaining in the lungs after normal tidalVolume of air remaining in the lungs after normal tidal
expiration, when there is no airflow.expiration, when there is no airflow.
N- 2 -3 L OR 30-35 ml/kg.N- 2 -3 L OR 30-35 ml/kg.
FRC = RV + ERVFRC = RV + ERV
Decreases under anesthesia **Decreases under anesthesia **
With paralysis – decreases by 16%With paralysis – decreases by 16%
26. FUNCTIONS OF FRCFUNCTIONS OF FRC
Oxygen store **increase time to develop hypoxia**Oxygen store **increase time to develop hypoxia**
Buffer for maintaining a steady arterial po2Buffer for maintaining a steady arterial po2
Partial inflation helps prevent atelectasis**Partial inflation helps prevent atelectasis**
Minimize the work of breathingMinimize the work of breathing
Minimize pulmonary vascular resistanceMinimize pulmonary vascular resistance
Minimized v/q mismatchMinimized v/q mismatch
27. FACTORS AFFECTING FRCFACTORS AFFECTING FRC
FRC INCREASES WITHFRC INCREASES WITH
Increased heightIncreased height
Erect position (30% more than in supine)Erect position (30% more than in supine)
Decreased lung recoil (e.g. emphysema)**Decreased lung recoil (e.g. emphysema)**
FRC DECREASES WITHFRC DECREASES WITH
Obesity **Obesity **
Muscle paralysis (especially in supine)Muscle paralysis (especially in supine)
Supine position **Supine position **
Restrictive lung disease (e.g. fibrosis, Pregnancy)Restrictive lung disease (e.g. fibrosis, Pregnancy)
AnesthesiaAnesthesia
FRC does NOT change with age.FRC does NOT change with age.
29. Pulmonary Function TestsPulmonary Function Tests
The term encompasses a wide variety of objective testsThe term encompasses a wide variety of objective tests
to assess lung functionto assess lung function
Provide objective and standardized measurements forProvide objective and standardized measurements for
assessing the presence and severity of respiratoryassessing the presence and severity of respiratory
dysfunction.dysfunction.
30. GOALSGOALS
To predict the presence of pulmonary dysfunctionTo predict the presence of pulmonary dysfunction
To know the functional nature of disease (obstructive orTo know the functional nature of disease (obstructive or
restrictive. )restrictive. )
To assess the severity of diseaseTo assess the severity of disease
To assess the progression of diseaseTo assess the progression of disease
To assess the response to treatmentTo assess the response to treatment
To identify patients at increased risk of morbidity andTo identify patients at increased risk of morbidity and
mortality, undergoing pulmonary resection.mortality, undergoing pulmonary resection.
31. To wean patient from ventilator in ICU.To wean patient from ventilator in ICU.
Medicolegal- to assess lung impairment as a result ofMedicolegal- to assess lung impairment as a result of
occupational hazard.occupational hazard.
Epidemiological surveys- to assess the hazards toEpidemiological surveys- to assess the hazards to
document incidence of diseasedocument incidence of disease
To identify patients at perioperative risk of pulmonaryTo identify patients at perioperative risk of pulmonary
complicationscomplications
GOALS, CONTINUED……..
33. BED SIDE PFTBED SIDE PFT
1)Sabrasez breath holding test:1)Sabrasez breath holding test:
Ask the patient to take a full but not too deep breath & hold it as long as possible.Ask the patient to take a full but not too deep breath & hold it as long as possible.
>25 SEC.-NORMAL Cardiopulmonary Reserve (CPR) **>25 SEC.-NORMAL Cardiopulmonary Reserve (CPR) **
15-25 SEC- LIMITED CPR15-25 SEC- LIMITED CPR
<15 SEC- VERY POOR CPR (Contraindication for elective surgery)<15 SEC- VERY POOR CPR (Contraindication for elective surgery)
25- 30 SEC - 3500 ml VC25- 30 SEC - 3500 ml VC
20 – 25 SEC - 3000 ml VC20 – 25 SEC - 3000 ml VC
15 - 20 SEC - 2500 ml VC15 - 20 SEC - 2500 ml VC
10 - 15 SEC - 2000 ml VC10 - 15 SEC - 2000 ml VC
5 - 10 SEC - 1500 ml VC5 - 10 SEC - 1500 ml VC
34. BED SIDE PFTBED SIDE PFT
2) Single breath count:2) Single breath count:
After deep breath, hold it and start counting till the nextAfter deep breath, hold it and start counting till the next
breath.breath.
N- 30-40 COUNTN- 30-40 COUNT
Indicates vital capacityIndicates vital capacity
35. BED SIDE PFTBED SIDE PFT
3) SCHNEIDER’S MATCH BLOWING TEST: MEASURES Maximum3) SCHNEIDER’S MATCH BLOWING TEST: MEASURES Maximum
Breathing Capacity.**Breathing Capacity.**
Ask to blow a match stick from a distance of 15 cm with:Ask to blow a match stick from a distance of 15 cm with:
Mouth wide openMouth wide open
Chin rested/supportedChin rested/supported
No purse lippingNo purse lipping
No head movementNo head movement
No air movement in the roomNo air movement in the room
Mouth and match at the same levelMouth and match at the same level
36. BED SIDE PFTBED SIDE PFT
Can not blow out a matchCan not blow out a match
MBC < 60 L/minMBC < 60 L/min
FEV1 < 1.6L**FEV1 < 1.6L**
Able to blow out a matchAble to blow out a match
MBC > 60 L/minMBC > 60 L/min
FEV1 > 1.6LFEV1 > 1.6L
37. MODIFIED MATCH TEST:MODIFIED MATCH TEST:
DISTANCE MBCDISTANCE MBC
9” >150 L/MIN.9” >150 L/MIN.
6” >60 L/MIN.6” >60 L/MIN.
3” > 40 L/MIN.3” > 40 L/MIN.
38. BED SIDE TESTBED SIDE TEST
4) COUGH TEST: DEEP BREATH COUGH4) COUGH TEST: DEEP BREATH COUGH
ABILITY TO COUGHABILITY TO COUGH
STRENGTHSTRENGTH
EFFECTIVENESSEFFECTIVENESS
INADEQUATE COUGH IFINADEQUATE COUGH IF::
FVC<20 ML/KFVC<20 ML/K
FEV1 < 15 ML/KGFEV1 < 15 ML/KG
PEFR < 200 L/MIN.PEFR < 200 L/MIN.
##VC ~ 3 TIMES TV FOR EFFECTIVE COUGH.####VC ~ 3 TIMES TV FOR EFFECTIVE COUGH.##
39. BED SIDE TESTBED SIDE TEST
5) FORCED EXPIRATORY TIME:5) FORCED EXPIRATORY TIME:
After deep breath, exhale maximally and forcefully & keepAfter deep breath, exhale maximally and forcefully & keep
stethoscope over trachea & listen.stethoscope over trachea & listen.
N FET – 3-5 SECS.N FET – 3-5 SECS.
OBS.LUNG DIS. - > 6 SECOBS.LUNG DIS. - > 6 SEC
RES. LUNG DIS.- < 3 SECRES. LUNG DIS.- < 3 SEC
40. BED SIDE PFTBED SIDE PFT
6) WRIGHT PEAK FLOW METER6) WRIGHT PEAK FLOW METER::
Measures PEFR (Peak Expiratory Flow Rate)**Measures PEFR (Peak Expiratory Flow Rate)**
N – MALES- 450-700 L/MIN.N – MALES- 450-700 L/MIN.
FEMALES- 350-500 L/MIN.FEMALES- 350-500 L/MIN.
<200 L/ MIN. – INADEQUATE COUGH EFFICIENCY.<200 L/ MIN. – INADEQUATE COUGH EFFICIENCY.
41. MEASUREMENT OF TV & MVMEASUREMENT OF TV & MV
7)Wright respirometer7)Wright respirometer ::
Measures TV, MV…..Measures TV, MV…..
Simple and rapidSimple and rapid
Instrument- compact, light and portable.Instrument- compact, light and portable.
Disadvantage: It under- reads at low flow rates and over- readsDisadvantage: It under- reads at low flow rates and over- reads
at high flow rates.at high flow rates.
Can be connected to endotracheal tube or face maskCan be connected to endotracheal tube or face mask
42. Prior explanation to patients needed.Prior explanation to patients needed.
Ideally done in sitting position.Ideally done in sitting position.
MV- instrument record for 1 min. And read directlyMV- instrument record for 1 min. And read directly
TV-calculated and dividing MV by counting Respiratory Rate.TV-calculated and dividing MV by counting Respiratory Rate.
USES:USES:
1)BED SIDE PFT1)BED SIDE PFT
2) ICU – WEANIG PTS. FROM Ventilation2) ICU – WEANIG PTS. FROM Ventilation..
43. BED SIDE PFTBED SIDE PFT
8) MICROSPIROMETERS8) MICROSPIROMETERS – MEASURE VC.– MEASURE VC.
9) BED SIDE PULSE OXIMETRY9) BED SIDE PULSE OXIMETRY
10) ABG.**10) ABG.**
50. SPIROMETRY : CORNERSTONE OF ALL PFTs.SPIROMETRY : CORNERSTONE OF ALL PFTs.
John hutchinson – invented spirometer.John hutchinson – invented spirometer.
““Spirometer is a medical test that measures the volume of airSpirometer is a medical test that measures the volume of air
an individual inhales or exhales as a function of time.”an individual inhales or exhales as a function of time.”
Measures VC, FVC, FEV1, PEFR.Measures VC, FVC, FEV1, PEFR.
CAN’T MEASURE – FRC, RV, TLC. **CAN’T MEASURE – FRC, RV, TLC. **
MECHANICAL VENTILATORY FUNCTIONS OFMECHANICAL VENTILATORY FUNCTIONS OF
LUNG / CHEST WALL:LUNG / CHEST WALL:
51. PREREQUISITIESPREREQUISITIES
Prior explanation to the patientPrior explanation to the patient
Not to smoke /inhale bronchodilators 6 hrs prior or oralNot to smoke /inhale bronchodilators 6 hrs prior or oral
bronchodilators 12hrs prior.bronchodilators 12hrs prior.
Remove any tight clothing's/ waist beltRemove any tight clothing's/ waist belt
Pt. Seated comfortablyPt. Seated comfortably
If obese, child < 12 yrs- standingIf obese, child < 12 yrs- standing
52. PREREQUISITESPREREQUISITES
Nose clip to close nostrils.Nose clip to close nostrils.
Exp. Effort should last ≥ 4 secs.Exp. Effort should last ≥ 4 secs.
Should not be interfered by coughing, glottis closure,Should not be interfered by coughing, glottis closure,
mechanical obstruction.mechanical obstruction.
3 acceptable tracings taken & largest value is used.3 acceptable tracings taken & largest value is used.
53. FORCED VITAL CAPACITYFORCED VITAL CAPACITY
(FVC)(FVC)
Max vol. Of air which can be expired out as forcefully andMax vol. Of air which can be expired out as forcefully and
rapidly as possible, following a maximal inspiration to TLC.rapidly as possible, following a maximal inspiration to TLC.
Exhaled volume is recorded with respect to time.Exhaled volume is recorded with respect to time.
Indirectly reflects flow resistance property of airways.Indirectly reflects flow resistance property of airways.
Normal healthy subjects have VC = FVC.Normal healthy subjects have VC = FVC.
54. Prior instruction to patients, practice attempts as itPrior instruction to patients, practice attempts as it
needs patient cooperation and effect.needs patient cooperation and effect.
Exhalation should take at least 4 sec and should not beExhalation should take at least 4 sec and should not be
interrupted by cough, glottis closure or mechanicalinterrupted by cough, glottis closure or mechanical
obstruction.obstruction.
55. FORCED VITAL CAPACITY IN 1FORCED VITAL CAPACITY IN 1
SEC. (FEV1)SEC. (FEV1)
Forced expired vol. In 1 sec during FVC maneuver.Forced expired vol. In 1 sec during FVC maneuver.
Expressed as an absolute value or % of FVC .Expressed as an absolute value or % of FVC .
N- FEV1 (1 SEC)- 75-85% OF FVCN- FEV1 (1 SEC)- 75-85% OF FVC
FEV2 (2 SEC)- 94% OF FVCFEV2 (2 SEC)- 94% OF FVC
FEV3 (3 SEC)- 97% OF FVCFEV3 (3 SEC)- 97% OF FVC
56. CONTINUED……CONTINUED……
CLINICAL RANGECLINICAL RANGE
(FEV1)(FEV1)
3 - 4.5 L3 - 4.5 L
1.5 – 2.5 L1.5 – 2.5 L
<1 L<1 L
0.8 L0.8 L
0.5 L0.5 L
PATIENT GROUPPATIENT GROUP
NORMAL ADULTNORMAL ADULT
MILD –MILD –
MOD.OBSTRUCTIONMOD.OBSTRUCTION
HANDICAPPEDHANDICAPPED
DISABILITYDISABILITY
SEVERE EMPHYSEMASEVERE EMPHYSEMA
57. CONTINUED……CONTINUED……
FEV1 – Decreased in both obstructive & restrictive lungFEV1 – Decreased in both obstructive & restrictive lung
disorders.disorders.
FEV1/FVC – Reduced in obstructive disorders.FEV1/FVC – Reduced in obstructive disorders.
NORMAL VALUE IS 75 – 85 % (FEV1/FVC)NORMAL VALUE IS 75 – 85 % (FEV1/FVC)
< 70% OF PREDICTED VALUE – MILD OBST.< 70% OF PREDICTED VALUE – MILD OBST.
< 60% OF PREDICTED VALUE – MODERATE OBST.< 60% OF PREDICTED VALUE – MODERATE OBST.
< 50% OF PREDICTED VALUE – SEVERE OBST.< 50% OF PREDICTED VALUE – SEVERE OBST.
58. Spirometry Interpretation:Spirometry Interpretation:
Obstructive vs. Restrictive DefectObstructive vs. Restrictive Defect
Obstructive DisordersObstructive Disorders
Characterized by aCharacterized by a
limitation of expiratorylimitation of expiratory
airflow so that airwaysairflow so that airways
cannot empty.cannot empty.
Examples:Examples:
AsthmaAsthma
EmphysemaEmphysema
Cystic FibrosisCystic Fibrosis
Restrictive DisordersRestrictive Disorders
Characterized by reducedCharacterized by reduced
lung volumes/decreasedlung volumes/decreased
lung compliancelung compliance
ExamplesExamples::
Interstitial FibrosisInterstitial Fibrosis
ScoliosisScoliosis
ObesityObesity
Lung ResectionLung Resection
Neuromuscular diseasesNeuromuscular diseases
60. Spirometry Interpretation: What do theSpirometry Interpretation: What do the
numbers mean?numbers mean?
FVCFVC
Interpretation of %Interpretation of %
predicted:predicted:
80-120% Normal80-120% Normal
70-79%70-79% Mild reductionMild reduction
50%-69% Moderate50%-69% Moderate
reductionreduction
<50% Severe reduction<50% Severe reduction
FEV1FEV1
Interpretation of %Interpretation of %
predicted:predicted:
>75% Normal>75% Normal
60%-75% Mild obstruction60%-75% Mild obstruction
50-59% Moderate50-59% Moderate
obstructionobstruction
<49% Severe obstruction<49% Severe obstruction
61. Spirometry Interpretation: What do theSpirometry Interpretation: What do the
numbers mean?numbers mean?
FEF 25-75% InterpretationFEF 25-75% Interpretation
of % predicted:of % predicted:
>79% Normal>79% Normal
60-79%60-79% MildMild
obstructionobstruction
40-59%40-59% ModerateModerate
obstructionobstruction
<40% Severe<40% Severe
obstructionobstruction
FEV1/FVC Interpretation ofFEV1/FVC Interpretation of
absoluteabsolute value:value:
80 or higher80 or higher
NormalNormal
79 or lower79 or lower
AbnormalAbnormal
66. Volume–time curves obtained during forcedVolume–time curves obtained during forced
expiration using a wedge-bellows spirometer.expiration using a wedge-bellows spirometer.
(a) The subject has taken a full breath in and exhaled forcibly and fully.
Maximal flow decelerates as forced expiration proceeds, because the
airways decrease in size as the lung volume diminishes**.
Exhalation is terminated when the expired flow rate falls to <0.25
litres/sec (as here) or at 14 sec.
(b) Obstructive and restrictive patterns. In obstruction, FEV1/FVC is low;
in restrictive disorders it is normal or high.
(c) Straight line traces (a) in central airways obstruction, flow is constant
through the first half of expiration; (b) Tracheo-bronchial collapse occurs
in severe emphysema and tracheomalacia the first 200 ml is exhaled
rapidly after which the compressed airway behaves like a fixed central
obstruction.
(d) Response of FEV1 to treatment. A patient with moderate asthma
tested before and after salbutamol and after a course of prednisolone.
FEV1 improves more than FVC
67. PEAK EXPIRATORY FLOW RATEPEAK EXPIRATORY FLOW RATE
(PEFR)(PEFR)
It is the max. Flow rate during FVC maneuver in the initialIt is the max. Flow rate during FVC maneuver in the initial
0.1 sec.0.1 sec.
-PEFR DETERMINED BY :-PEFR DETERMINED BY :
1)1)Function of caliber of airwayFunction of caliber of airway
2)2)Expiratory muscle strengthExpiratory muscle strength
3)3)Pt’s coordination & effortPt’s coordination & effort
- Estimated by Average flow during the liter of gas expired- Estimated by Average flow during the liter of gas expired
after initial 200 ml during FVC maneuver.after initial 200 ml during FVC maneuver.
68. FORCED MID-EXPIRATORY FLOWFORCED MID-EXPIRATORY FLOW
RATE (FEF25%-75%):RATE (FEF25%-75%):
Maximum Mid expiratory Flow rate…..Max. Flow rateMaximum Mid expiratory Flow rate…..Max. Flow rate
during the mid-expiratory part of FVC maneuver.during the mid-expiratory part of FVC maneuver.
FEFFEF25-75%25-75% decreased by :decreased by :
1)1) marked reduction in exp. Effortmarked reduction in exp. Effort
2)2) submaximal inspiration maneuver ↓FVC → ↓ FEFsubmaximal inspiration maneuver ↓FVC → ↓ FEF25-75%25-75%
69. It may decrease with truly max. Effort as compared toIt may decrease with truly max. Effort as compared to
slightly submaximal effort .slightly submaximal effort .
N value – 4.5-5 L/sec. Or 300 L/min.N value – 4.5-5 L/sec. Or 300 L/min.
CLINICAL SIGNIFICANCECLINICAL SIGNIFICANCE::
SENSITIVE & IST INDICATORSENSITIVE & IST INDICATOR OF OBSTRUCTION OFOF OBSTRUCTION OF
SMALL DISTAL AIRWAYSSMALL DISTAL AIRWAYS
70. MAXIMUM BREATHING CAPACITY: (MBC/MVV)MAXIMUM BREATHING CAPACITY: (MBC/MVV)
MAX. VOLUNTARY VENTILATIONMAX. VOLUNTARY VENTILATION
Largest volume that can be breathed per minute byLargest volume that can be breathed per minute by
voluntary effort , as hard & as fast as possible.voluntary effort , as hard & as fast as possible.
N – 150-175 l/min.N – 150-175 l/min.
Estimate of max. Ventilation available to meet increasedEstimate of max. Ventilation available to meet increased
physiological demand.physiological demand.
Measured for 12 secs – extrapolated for 1 min.Measured for 12 secs – extrapolated for 1 min.
MVV = FEV1 X 35MVV = FEV1 X 35
72. RESPIRATORY MUSCLE STRENGTHRESPIRATORY MUSCLE STRENGTH
Evaluated by measuring max inspiratory and expiratoryEvaluated by measuring max inspiratory and expiratory
Efforts.Efforts.
Pressures are generated against occluded airway .Pressures are generated against occluded airway .
MAX STATIC INSP. PRESSURE: (PIMAX)-MAX STATIC INSP. PRESSURE: (PIMAX)-
Measured when inspiratory muscles are at their optimal length i.e. atMeasured when inspiratory muscles are at their optimal length i.e. at
RVRV
PI MAX = -125 CM H2OPI MAX = -125 CM H2O
CLINICAL SIGNIFICANCE:CLINICAL SIGNIFICANCE:
73. CONTINUED…….CONTINUED…….
MAX. STATIC EXPIRATORY PRESSURE (PEMAX):MAX. STATIC EXPIRATORY PRESSURE (PEMAX):
Measured after full inspiration to TLCMeasured after full inspiration to TLC
N VALUE OF PEMAX IS =200 CM H20N VALUE OF PEMAX IS =200 CM H20
PEMAX < +40 CM H20 – Impaired cough abilityPEMAX < +40 CM H20 – Impaired cough ability
Particularly useful in pts with NM Disorders duringParticularly useful in pts with NM Disorders during
weaningweaning
74. Spirometry Pre and PostSpirometry Pre and Post
BronchodilatorBronchodilator
Obtain a flow-volume loop.Obtain a flow-volume loop.
Administer a bronchodilator.Administer a bronchodilator.
Obtain the flow-volume loop again a minimum of 15Obtain the flow-volume loop again a minimum of 15
minutes after administration of the bronchodilator.minutes after administration of the bronchodilator.
Calculate percent change (FEV1 most commonly used---Calculate percent change (FEV1 most commonly used---
so % change FEV 1= [(FEV1 Post-FEV1 Pre)/FEV1 Pre]so % change FEV 1= [(FEV1 Post-FEV1 Pre)/FEV1 Pre]
X 100).X 100).
75. The response of FEV1 and other measures of airflowThe response of FEV1 and other measures of airflow
obstruction to bronchodilators is measured routinely,obstruction to bronchodilators is measured routinely,
without any consensus as to how this should bewithout any consensus as to how this should be
performed or interpreted.performed or interpreted.
It is mainly used to identify untreated asthma, whenIt is mainly used to identify untreated asthma, when
dramatic improvements of 0.5 litres or more may bedramatic improvements of 0.5 litres or more may be
seen after only 200 mcg of inhaled salbutamol..seen after only 200 mcg of inhaled salbutamol..
Disappointingly there is no test which identifies asthmaDisappointingly there is no test which identifies asthma
in the presence of COPD.in the presence of COPD.
76. An improvement of 15% or 0.4 liters (the greater) afterAn improvement of 15% or 0.4 liters (the greater) after
2.5 mg nebulized salbutamol points towards some2.5 mg nebulized salbutamol points towards some
potential for reversibility, but current guidelinespotential for reversibility, but current guidelines
emphasize the need for several days of therapy ratheremphasize the need for several days of therapy rather
than a single laboratory test to assess this potential.than a single laboratory test to assess this potential.
In COPD, post-bronchodilator FEV1 and VC vary lessIn COPD, post-bronchodilator FEV1 and VC vary less
than pre-bronchodilator readings and should ideally bethan pre-bronchodilator readings and should ideally be
used to measure changes of lung function over time inused to measure changes of lung function over time in
longitudinal studies of obstructive disorders.longitudinal studies of obstructive disorders.
77. Bronchial challenges with histamine, methacholine, coldBronchial challenges with histamine, methacholine, cold
air or intensive exercise are used to confirm asthma inair or intensive exercise are used to confirm asthma in
individuals with normal resting spirometric tests.individuals with normal resting spirometric tests.
Asthmatic subjects react to pharmacologicalAsthmatic subjects react to pharmacological
bronchoconstrictors with a 20% fall of FEV1 at a muchbronchoconstrictors with a 20% fall of FEV1 at a much
lower dose than non-reactive individualslower dose than non-reactive individuals
78. MECHANICAL VENTILATORY FUNCTIONS OFMECHANICAL VENTILATORY FUNCTIONS OF
LUNG / CHEST WALL:LUNG / CHEST WALL:
MEASUREMENTS OFMEASUREMENTS OF
VOLUMESVOLUMES
79. TLC, RV, FRC – MEASURED USINGTLC, RV, FRC – MEASURED USING
Nitrogen washout methodNitrogen washout method
Inert gas (helium) dilution methodInert gas (helium) dilution method
Total body plethysmographyTotal body plethysmography
80. 1) HELIUM DILUTION METHOD:1) HELIUM DILUTION METHOD:
Patient breathes in and out of a spirometer filled with 10%Patient breathes in and out of a spirometer filled with 10%
helium and 90% o2, till conc. In spirometer and lunghelium and 90% o2, till conc. In spirometer and lung
becomes same (equilibrium).becomes same (equilibrium).
As no helium is lost; (as it is insoluble in blood)As no helium is lost; (as it is insoluble in blood)
C1 X V1 = C2 ( V1 + V2)C1 X V1 = C2 ( V1 + V2)
V2 =V2 = V1 ( C1 – C2)V1 ( C1 – C2)
C2C2
V1= VOL. OF SPIROMETERV1= VOL. OF SPIROMETER
V2= FRCV2= FRC
C1= Conc.of He in the spirometer before equilibriumC1= Conc.of He in the spirometer before equilibrium
C2 = Conc, of He in the spirometer after equilibriumC2 = Conc, of He in the spirometer after equilibrium
81.
82. 2) TOTAL BODY2) TOTAL BODY
PLETHYSMOGRAPHYPLETHYSMOGRAPHY::
The subject sits in a closed booth (‘body box’,The subject sits in a closed booth (‘body box’,
plethysmograph) of known volume and breathes in and outplethysmograph) of known volume and breathes in and out
against a closed tube for a few seconds.against a closed tube for a few seconds.
According to Boyle’s Law the ratio of the pressures in theAccording to Boyle’s Law the ratio of the pressures in the
mouth and around the subject is determined by the ratio ofmouth and around the subject is determined by the ratio of
The volumes of the lungs and the box.The volumes of the lungs and the box.
BOYLE’S LAW:BOYLE’S LAW:
P and V are CONSTANT at CONSTANT temp.P and V are CONSTANT at CONSTANT temp.
83. For Box – p1v1 = p2 (v1- ∆v)For Box – p1v1 = p2 (v1- ∆v)
For Subject – p3 x v2 =p4 (v2 - ∆v)For Subject – p3 x v2 =p4 (v2 - ∆v)
P1- initial box pr. P2- final box pr.P1- initial box pr. P2- final box pr.
V1- initial box vol. ∆ v- change in box vol.V1- initial box vol. ∆ v- change in box vol.
P3- initial mouth pr., p4- final mouth pr.P3- initial mouth pr., p4- final mouth pr.
V2- FRCV2- FRC
84.
85. CONTINUED………CONTINUED………
DIFFERENCE BETWEEN THE TWO METHODS:DIFFERENCE BETWEEN THE TWO METHODS:
In healthy people there is very little difference.In healthy people there is very little difference.
Gas dilution technique measures only theGas dilution technique measures only the
communicating gas volume.communicating gas volume.
Thus, gas trapped behind closed airways, gas inThus, gas trapped behind closed airways, gas in
pneumothorax are not measured by gas dilutionpneumothorax are not measured by gas dilution
technique, but measured by body plethysmographtechnique, but measured by body plethysmograph
86. CONTINUED………CONTINUED………
3) N2 WASH OUT METHOD:3) N2 WASH OUT METHOD:
Following a maximal expiration (RV) or normal expirationFollowing a maximal expiration (RV) or normal expiration
(FRC), Pt. inspires 100% O2 and then expires it into(FRC), Pt. inspires 100% O2 and then expires it into
spirometer ( free of N2) → over next few minutesspirometer ( free of N2) → over next few minutes
(usually 6-7 min.), till all the N2 is washed out of the(usually 6-7 min.), till all the N2 is washed out of the
lungs.lungs.
N2 conc. of spirometer is calculated followed by totalN2 conc. of spirometer is calculated followed by total
vol.of AIR exhaled. As air has 80% N2 → so actualvol.of AIR exhaled. As air has 80% N2 → so actual
FRC/RV is calculated.FRC/RV is calculated.
88. 2) GAS- EXCHANGE TESTS:2) GAS- EXCHANGE TESTS:
A) Alveolar-arterial po2 gradientA) Alveolar-arterial po2 gradient
B) Diffusion capacityB) Diffusion capacity
C) Gas distribution test: Helium dilution method.C) Gas distribution test: Helium dilution method.
D) ventilation – perfusion testsD) ventilation – perfusion tests
1-ABG1-ABG
2-single breath CO2-single breath CO22 elimination testelimination test
3-Shunt equation3-Shunt equation
89. TESTS FOR GAS EXCHANGETESTS FOR GAS EXCHANGE
FUNCTIONFUNCTION
1)1) ALVEOLAR-ARTERIAL O2 TENSION GRADIENTALVEOLAR-ARTERIAL O2 TENSION GRADIENT::
Sensitive indicator of detecting regional V/Q inequalitySensitive indicator of detecting regional V/Q inequality
Normal value in young adult at room air = 8 mmHg to up toNormal value in young adult at room air = 8 mmHg to up to
25 mmHg in 825 mmHg in 8thth
decade (d/t decrease in PaO2)decade (d/t decrease in PaO2)
Abnormally high values at room air is seen in asymptomaticAbnormally high values at room air is seen in asymptomatic
smokers & chronic Bronchitissmokers & chronic Bronchitis
PAO2 = PIO2 –PAO2 = PIO2 – PaCo2PaCo2
RR
90. CONTINUED……..CONTINUED……..
2) DYSPNEA DIFFENRENTIATION INDEX (DDI):2) DYSPNEA DIFFENRENTIATION INDEX (DDI):
- To d/f dyspnea due to resp/ cardiac d’sTo d/f dyspnea due to resp/ cardiac d’s
DDI =DDI = PEFR x PaCO2PEFR x PaCO2
10001000
- DDI- Lower in resp. pathologyDDI- Lower in resp. pathology
91. CONTINUED……CONTINUED……
33) DIFFUSING CAPACITY OF LUNG) DIFFUSING CAPACITY OF LUNG::
Defined as the rate at which gas enters into blood.Defined as the rate at which gas enters into blood.
divided by its driving pressure.divided by its driving pressure.
CO taken up is determined by infrared analysis:CO taken up is determined by infrared analysis:
DlCO =DlCO = CO ml/min/mmhgCO ml/min/mmhg
PACO – PcCOPACO – PcCO
N range 20- 30 ml/min./mmhg.N range 20- 30 ml/min./mmhg.
DLO2 = DLCO x 1.23DLO2 = DLCO x 1.23
92. DRIVING PR: gradient b/w alveoli & end capillary tensions.DRIVING PR: gradient b/w alveoli & end capillary tensions.
Fick’s law of diffusion : Vgas =Fick’s law of diffusion : Vgas = AA x D x (P1-P2)x D x (P1-P2)
TT
D= diffusion coeff=D= diffusion coeff= solubilitysolubility
√√MWMW
93. CONTINUED…….CONTINUED…….
DL IS MEASURED BY USING CO, cause:DL IS MEASURED BY USING CO, cause:
A)A) High affinity for Hb which is approx. 200 times that ofHigh affinity for Hb which is approx. 200 times that of
O2 , so does not rapidly build up in plasmaO2 , so does not rapidly build up in plasma
B)B) Under N condition it has low bld conc ≈ 0, Therefore,Under N condition it has low bld conc ≈ 0, Therefore,
pulm conc.≈0pulm conc.≈0
94. SINGLE BREATH TEST USINGSINGLE BREATH TEST USING
COCO
The patient inhales from full expiration from a reservoirThe patient inhales from full expiration from a reservoir
containing a trace of CO (0.03%), about 10% helium (orcontaining a trace of CO (0.03%), about 10% helium (or
other non-absorbed gas) with 16–20% oxygen and holdother non-absorbed gas) with 16–20% oxygen and hold
the breath for 10 secsthe breath for 10 secs
Helium dilution is used to measure the accessibleHelium dilution is used to measure the accessible
volume of alveolar gas (VA).volume of alveolar gas (VA).
95.
96. Carbon monoxide is both diluted and absorbed, thus:Carbon monoxide is both diluted and absorbed, thus:
inspired[CO]/expired[CO] is greater than inspired[He]/inspired[CO]/expired[CO] is greater than inspired[He]/
expired[He]; i.e. the ratio of CO uptake to helium dilutionexpired[He]; i.e. the ratio of CO uptake to helium dilution
(CO ratio) >1.(CO ratio) >1.
It is assumed that CO is absorbed exponentially during theIt is assumed that CO is absorbed exponentially during the
period of breath-holding; because Pco is zero in theperiod of breath-holding; because Pco is zero in the
pulmonary blood and the pressure gradient is the alveolarpulmonary blood and the pressure gradient is the alveolar
pressure of the gaspressure of the gas
97. ThereforeTherefore
DLco = VA x (CO ratio) x (1/breath-holding time) x (1/dryDLco = VA x (CO ratio) x (1/breath-holding time) x (1/dry
barometric pressure).barometric pressure).
The units are CO uptake per unit time per pressure unitThe units are CO uptake per unit time per pressure unit
difference from alveolar gas to blood.difference from alveolar gas to blood.
DLco/VA is calculated by dividing DLco by VA measured atDLco/VA is calculated by dividing DLco by VA measured at
body temperature and pressure, saturated with waterbody temperature and pressure, saturated with water
vapour.vapour.
98. The amount of CO extracted depends on:The amount of CO extracted depends on:
The diffusing capacity of the alveolar membrane,The diffusing capacity of the alveolar membrane,
comprising: The area of the gas exchanging surface of thecomprising: The area of the gas exchanging surface of the
lung.lung.
The thickness of the alveolar capillary barrier.The thickness of the alveolar capillary barrier.
The pulmonary capillary blood volume (the volume ofThe pulmonary capillary blood volume (the volume of
haemoglobin in contact with the inhaled gas).haemoglobin in contact with the inhaled gas).
99. DLco depends mainly on alveolar function except:DLco depends mainly on alveolar function except:
When the airways are abnormal and a deep breath is notWhen the airways are abnormal and a deep breath is not
evenly distributed to all parts of the lung.evenly distributed to all parts of the lung.
When the concentration of hemoglobin in the red cells isWhen the concentration of hemoglobin in the red cells is
not normal.not normal.
There are two ways of reporting diffusing capacity. :There are two ways of reporting diffusing capacity. :
DLco is the rate of uptake of CO per unit of alveolar PcoDLco is the rate of uptake of CO per unit of alveolar Pco
in the whole lungin the whole lung
In some situations it can be helpful to divide this by theIn some situations it can be helpful to divide this by the
lung volume; this yields an index known as diffusion orlung volume; this yields an index known as diffusion or
transfer coefficient DL/VA.transfer coefficient DL/VA.
100. In practice both are useful in separate situations.In practice both are useful in separate situations.
The calculation of DLco assumes that regional variations ofThe calculation of DLco assumes that regional variations of
ventilation, perfusion and diffusion are averaged out.ventilation, perfusion and diffusion are averaged out.
In patients with respiratory failure severe ventilation–In patients with respiratory failure severe ventilation–
perfusion mismatching can result in marked abnormalitiesperfusion mismatching can result in marked abnormalities
of CO2 and O2 exchange when DLco is normal.of CO2 and O2 exchange when DLco is normal.
Conversely, a low DLco is compatible with a normal restingConversely, a low DLco is compatible with a normal resting
arterial Po2. Oxygen exchange in exercise is invariablyarterial Po2. Oxygen exchange in exercise is invariably
abnormal when DLco is low.abnormal when DLco is low.
101. Interpretation of DLco and DL/VA are useful clinically in aInterpretation of DLco and DL/VA are useful clinically in a
number of situations.number of situations.
When VC, FEV1, FVC and [Hb] are all normal, a low DLcoWhen VC, FEV1, FVC and [Hb] are all normal, a low DLco
strongly suggests disease involving the alveoli.strongly suggests disease involving the alveoli.
In airflow obstruction a low DLco and DLco/VA suggestIn airflow obstruction a low DLco and DLco/VA suggest
alveolar destruction (emphysema).alveolar destruction (emphysema).
In contrast, they are sometimes abnormally high in asthma.In contrast, they are sometimes abnormally high in asthma.
102. In restrictive pleural and chest wall disease, a highIn restrictive pleural and chest wall disease, a high
DLco/ VA suggests that there is no underlying lungDLco/ VA suggests that there is no underlying lung
disease.disease.
When there are widespread radiological lung shadows,When there are widespread radiological lung shadows,
such as in sarcoidosis or some occupational lung diseases,such as in sarcoidosis or some occupational lung diseases,
DLco reflects lung impairment and disability but is notDLco reflects lung impairment and disability but is not
correlated directly with the extent of the abnormality on thecorrelated directly with the extent of the abnormality on the
plain CXR.plain CXR.
Polycythaemia, pulmonary plethora such as in heat failurePolycythaemia, pulmonary plethora such as in heat failure
or left-to-right shunting and pulmonary haemorrhage causeor left-to-right shunting and pulmonary haemorrhage cause
an increase in DLco because of increases in the volume ofan increase in DLco because of increases in the volume of
haemoglobin in contact with the inspired air.haemoglobin in contact with the inspired air.
103. DLCO decreases in-DLCO decreases in-
Emphysema, lung resection, pul. Embolism, anemiaEmphysema, lung resection, pul. Embolism, anemia
Pulmonary fibrosis, sarcoidosis- increased thicknessPulmonary fibrosis, sarcoidosis- increased thickness
DLCO increases in conditions which increase pulmonary,DLCO increases in conditions which increase pulmonary,
blood flow:blood flow:
Supine position…..Exercise……ObesitySupine position…..Exercise……Obesity
L-R shunt….Polycythemia….pulmonaryL-R shunt….Polycythemia….pulmonary
plethora….pulmonary hemorrhageplethora….pulmonary hemorrhage
105. CATEGORIZATION OF PFTCATEGORIZATION OF PFT
3) CARDIOPULMONARY INTERACTION3) CARDIOPULMONARY INTERACTION::
Reflects gas exchange, ventilation, tissue O2, CO.Reflects gas exchange, ventilation, tissue O2, CO.
A) Qualitative tests:A) Qualitative tests:
- History , examination- History , examination
- ABG- ABG
- Stair climbing test- Stair climbing test
B) Quantitative testsB) Quantitative tests
- 6 min. Walk test (gold standard)- 6 min. Walk test (gold standard)
www.anaesthesia.co.inwww.anaesthesia.co.in
106. CONTINUED…….CONTINUED…….
1) STAIR CLIMBING TEST1) STAIR CLIMBING TEST::
If able to climb 3 flights of stairs without stopping/dypnoeaIf able to climb 3 flights of stairs without stopping/dypnoea
at his/her own pace- ↓morbidity & mortalityat his/her own pace- ↓morbidity & mortality
If not able to climb 2 flights – high riskIf not able to climb 2 flights – high risk
107. 2) 6 MINUTE WALK TEST:2) 6 MINUTE WALK TEST:
-Gold standardGold standard
-C.P. reserve is measured by estimating max. O2 uptakeC.P. reserve is measured by estimating max. O2 uptake
during exerciseduring exercise
-Modified if pt. can’t walk – bicycle/ arm exercisesModified if pt. can’t walk – bicycle/ arm exercises
108. - If pt. is able to walk for >2000 feet during 6 min pd,If pt. is able to walk for >2000 feet during 6 min pd,
- VO2 max > 15 ml/kg/minVO2 max > 15 ml/kg/min
- If 1080 feet in 1 min : VO2 of 12ml/kg/minIf 1080 feet in 1 min : VO2 of 12ml/kg/min
- Simultaneously oximetry is done & if Spo2 falls >4%-Simultaneously oximetry is done & if Spo2 falls >4%-
high riskhigh risk
109. Applied physiologyApplied physiology
A 34-year-old woman with diabetes presents to theA 34-year-old woman with diabetes presents to the
emergency department with complaints of fever, chills,emergency department with complaints of fever, chills,
back pain, dizziness, and shortness of breath. She reportsback pain, dizziness, and shortness of breath. She reports
a new-onset nonproductive cough and denies having chesta new-onset nonproductive cough and denies having chest
pain. She reports no sick contacts. On examination, she ispain. She reports no sick contacts. On examination, she is
ill-appearing, febrile, hypotensive, and tachycardic. She hasill-appearing, febrile, hypotensive, and tachycardic. She has
marked right costovertebral (flank) tenderness.marked right costovertebral (flank) tenderness.
Her lung examination demonstrates course rales andHer lung examination demonstrates course rales and
rhonchi throughout both lung fields. Her heart rate isrhonchi throughout both lung fields. Her heart rate is
tachycardic, but with a regular rhythm.tachycardic, but with a regular rhythm.
110. Applied physiologyApplied physiology
Her oxygen saturation on room air is very low at 80%Her oxygen saturation on room air is very low at 80%
(normal > 94%). Urinalysis reveals numerous bacteria and(normal > 94%). Urinalysis reveals numerous bacteria and
leukocytes, consistent with a urinary tract infection. She isleukocytes, consistent with a urinary tract infection. She is
diagnosed with pyelonephritis and septic shock and hasdiagnosed with pyelonephritis and septic shock and has
evidence of adult respiratory distress syndrome (ARDS)evidence of adult respiratory distress syndrome (ARDS)
with bilateral pulmonary infiltrates on chest x-ray. Thewith bilateral pulmonary infiltrates on chest x-ray. The
emergency room physician explains to the patient thatemergency room physician explains to the patient that
pulmonary injury has led to leaky pulmonary capillaries.pulmonary injury has led to leaky pulmonary capillaries.
111. Applied physiologyApplied physiology
◆◆ How does pulmonary capillary leakageHow does pulmonary capillary leakage
cause hypoxia?cause hypoxia?
◆◆ After a patient takes a normal breath andAfter a patient takes a normal breath and
exhales, what lung volume remains?exhales, what lung volume remains?
◆◆ How do obstructive lung diseases such asHow do obstructive lung diseases such as
asthma affect forced expiratory volume?asthma affect forced expiratory volume?
112. Applied physiologyApplied physiology
Summary: A 34-year-old diabetic woman has pyelonephritis, septicSummary: A 34-year-old diabetic woman has pyelonephritis, septic
shock, and ARDS.shock, and ARDS.
◆◆ Pulmonary capillary leakage and hypoxia: Accumulation of excessPulmonary capillary leakage and hypoxia: Accumulation of excess
fluid outside the capillaries leads to altered local ventilation andfluid outside the capillaries leads to altered local ventilation and
perfusion and makes gas exchange inefficient.perfusion and makes gas exchange inefficient.
◆◆ Lung volume remaining after normal breath: Functional residualLung volume remaining after normal breath: Functional residual
capacity (FRC; cannot be measured with spirometry alone).capacity (FRC; cannot be measured with spirometry alone).
◆◆ Forced expiratory volume with obstructive airway disease:Forced expiratory volume with obstructive airway disease:
Decreased.Decreased.
113. COMPREHENSIONCOMPREHENSION
QUESTIONSQUESTIONS
[1] In a 58-year-old woman with difficulty breathing, the TLC and FRC[1] In a 58-year-old woman with difficulty breathing, the TLC and FRC
are lower than normal and FEV1/FVC is slightly higher than normal.are lower than normal and FEV1/FVC is slightly higher than normal.
These findings are most consistent with which of the following?These findings are most consistent with which of the following?
A.A.Decreased pulmonary blood flowDecreased pulmonary blood flow
B.B.Decreased strength of the chest wall musclesDecreased strength of the chest wall muscles
C.C.Increased airway resistanceIncreased airway resistance
D.D.Increased chest wall elastic recoilIncreased chest wall elastic recoil
E.E.Increased lung elastic recoilIncreased lung elastic recoil
114. COMPREHENSIONCOMPREHENSION
QUESTIONSQUESTIONS
[2] A patient has reduced TLC and increased RV. FRC is[2] A patient has reduced TLC and increased RV. FRC is
normal. These findings are most consistent with which ofnormal. These findings are most consistent with which of
the following?the following?
A. Decreased pulmonary blood flowA. Decreased pulmonary blood flow
B. Decreased strength of the muscles of respirationB. Decreased strength of the muscles of respiration
C. Increased airway resistanceC. Increased airway resistance
D. Increased chest wall elastic recoilD. Increased chest wall elastic recoil
E. Increased lung elastic recoilE. Increased lung elastic recoil
115. COMPREHENSIONCOMPREHENSION
QUESTIONSQUESTIONS
[3] A chest x-ray of a patient with left-sided heart failure[3] A chest x-ray of a patient with left-sided heart failure
indicates pulmonary edema. Additional examinationindicates pulmonary edema. Additional examination
probably would reveal which of the following?probably would reveal which of the following?
A.A.Decreased pulmonary artery pressureDecreased pulmonary artery pressure
B. Decreased pulmonary lymph flowB. Decreased pulmonary lymph flow
C. Increased pulmonary venous pressureC. Increased pulmonary venous pressure
D. Normal arterial oxygen partial pressureD. Normal arterial oxygen partial pressure
E. Normal vital capacityE. Normal vital capacity
116. AnswersAnswers
[1] E. A lung with increased elastic recoil (decreased[1] E. A lung with increased elastic recoil (decreased
compliance) will be harder to fill on inspiration and willcompliance) will be harder to fill on inspiration and will
tend to pull the chest wall inward on relaxation of thetend to pull the chest wall inward on relaxation of the
muscles of breathing. Thus, both TLC and FRC will bemuscles of breathing. Thus, both TLC and FRC will be
decreased. Because airway radius is normal or evendecreased. Because airway radius is normal or even
increased, FEV1 normalized to FVC will be normal orincreased, FEV1 normalized to FVC will be normal or
increased even though FVC will be reduced. Decreasedincreased even though FVC will be reduced. Decreased
muscle strength could cause a decrease in TLC, but itmuscle strength could cause a decrease in TLC, but it
would not alter FRC.would not alter FRC.
117. [2] B. If the muscles of inspiration are weak, lungs cannot[2] B. If the muscles of inspiration are weak, lungs cannot
be inflated as well, thus reducing the inspiratory reservebe inflated as well, thus reducing the inspiratory reserve
volume and TLC. If the muscles of expiration are weak, notvolume and TLC. If the muscles of expiration are weak, not
as much air can be forced from the lungs and expiratoryas much air can be forced from the lungs and expiratory
reserve volume will be decreased, thus increasing RV.reserve volume will be decreased, thus increasing RV.
Increases in elastic recoil of either the chest wall or theIncreases in elastic recoil of either the chest wall or the
lungs and increases in airway resistance will alter TLClungs and increases in airway resistance will alter TLC
and/or FRC.and/or FRC.
118. {3} C. As a result of the decrease in myocardial{3} C. As a result of the decrease in myocardial
contractility, end diastolic pressure in the left ventriclecontractility, end diastolic pressure in the left ventricle
increases, leading to an increase in the pulmonary venousincreases, leading to an increase in the pulmonary venous
and pulmonary capillary pressures. The increasedand pulmonary capillary pressures. The increased
pulmonary capillary hydrostatic pressure leads to increasedpulmonary capillary hydrostatic pressure leads to increased
pulmonary capillary filtration, and when filtration exceedspulmonary capillary filtration, and when filtration exceeds
lymph flow, pulmonary edema develops. Pulmonary arterylymph flow, pulmonary edema develops. Pulmonary artery
pressure is likely to be increased in this condition. Thepressure is likely to be increased in this condition. The
edema interferes with gas exchange and with lung inflation;edema interferes with gas exchange and with lung inflation;
thus, arterial oxygen partial pressure and vital capacity willthus, arterial oxygen partial pressure and vital capacity will
be decreased.be decreased.
119. ReferencesReferences
LANGE CASE FILES: PHYSIOLOGYLANGE CASE FILES: PHYSIOLOGY
Lippincott Medical-Physiology-Principles-Lippincott Medical-Physiology-Principles-
for-Clinical-Medicine-4th-Ed-Gnv64for-Clinical-Medicine-4th-Ed-Gnv64
Oxford Desk Reference - RespiratoryOxford Desk Reference - Respiratory
MedicineMedicine
Powell FL. Mechanics of breathing. In:Powell FL. Mechanics of breathing. In:
Johnson LR, ed. Essential MedicalJohnson LR, ed. Essential Medical
Physiology. 3rd ed. San Diego, CA:Physiology. 3rd ed. San Diego, CA:
Elsevier Academic Press; 2003:277-288.Elsevier Academic Press; 2003:277-288.
