Pulmonary Function Testing Martha Richter, MSN, CRNA

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Pulmonary Function TestingMartha Richter, MSN,
CRNA
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Other test of pulmonary function

• Try to dodge the retirees in the commissary
• Have 5 minutes to change terminals in Atlanta
  Airport
• Tie the patient behind a car and take off
• Can he/she keep up?

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OBJECTIVES

• The student will
• Define lung volume terms used
• Describe the importance of the FEV1/FVC ratio
• List care objectives specific to patients with
  poor PFTs
• State 2 issues of concern involving PACU in this
  population

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How about some definitions?

• The Lung Volumes
• Inspiratory Reserve (IRV) 2500 cc
• Tidal Volume (Vt) 500cc
• Expiratory Reserve (ERV) 1500cc
• Residual Volume (RV) 1500cc
• TOGETHER THESE MAKE UP THE TOTAL LUNG VOLUME
• Figures are based on a 70kg male

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The lung volumes

• Vt 6-8 ml/kg
• Dec with reduced muscle strength,dec. lung
  compliance
• VC60 ml/kg. Correlation for deep breathing
  coughing. Dec with restrictive processes
• IClargest vol that can be inspired after
  reaching normal expiration. Can detect extrathor
  obst.
• FRCdefines lung compliance(by calc),is resting
  expir vol (when dec., ven admixture inc-gtarterial
  hypoxemia). Can be measured with nitrogen
  washout test

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How about more definitions?

• THE LUNG CAPACITIES
• Total lung (TLCIRVVtERVRV) or 6000 cc
• Vital capacity (VCIRVVtERV) or 4500 cc
• Functional Residual Capacity
• (FRCRVERV) or 3000cc
• Inspiratory Capacity (ICIRVVt) or 3000cc
• Based on 70 kg male

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?
RV Residual volume 1.5L
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ERV Expiratory reserve volume 1.5L
?
RV Residualvolume 1.5L
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?
ERV Expiratory reserve volume 1.5L
FRC Functional residual
capacity 3.0L
RV Residualvolume 1.5L
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?
VT Tidal volume 0.5L
ERV Expiratory reserve volume 1.5L
FRC Functional residual
capacity 3.0L
RV Residualvolume 1.5L
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IRV Inspiratory reserve volume 2.5L
VT Tidal volume 0.5L
ERV Expiratory reserve volume 1.5L
FRC Functional residual
capacity 3.0L
RV Residual volume 1.5L
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IRV Inspiratory reserve volume 2.5L
?
VT Tidal volume 0.5L
ERV Expiratory reserve volume 1.5L
FRC Functional residual
capacity 3.0L
RV Residualvolume 1.5L
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IRV Inspiratory reserve volume 2.5L
IC Inspiratory capacity 3.0L
?
VT Tidal volume 0.5L
ERV Expiratory reserve volume 1.5L
FRC Functional residual
capacity 3.0L
RV Residualvolume 1.5L
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IRV Inspiratory reserve volume 2.5L
IC Inspiratory capacity 3.0L
VC Vital capacity 4.5L
VT Tidal volume 0.5L
ERV Expiratory reserve volume 1.5L
FRC Functional residual
capacity 3.0L
RV Residualvolume 1.5L
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?
Inspiratory reserve volume


Tidal volume
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Inspiratory reserve volume
Inspiratory capacity


Tidal volume
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Inspiratory reserve volume
Inspiratory capacity


Tidal volume
Residual volume
Expiratory reserve volume


?
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Inspiratory reserve volume
Inspiratory capacity


Tidal volume
Functional residual capacity

Residual volume
Expiratory reserve volume


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Inspiratory reserve volume
Inspiratory capacity


Tidal volume
Functional residual capacity

Residual volume
Expiratory reserve volume


?

Inspiratory reserve volume
Expiratory reserve volume

Tidal volume

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Inspiratory reserve volume
Inspiratory capacity


Tidal volume
Functional residual capacity

Residual volume
Expiratory reserve volume



Vital capacity
Inspiratory reserve volume
Expiratory reserve volume

Tidal volume

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Inspiratory reserve volume
Inspiratory capacity


Tidal volume
Functional residual capacity

Residual volume
Expiratory reserve volume



Vital capacity
Inspiratory reserve volume
Expiratory reserve volume

Tidal volume

Functional residual capacity
Inspiratory Capacity
?


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Inspiratory reserve volume
Inspiratory capacity


Tidal volume
Functional residual capacity

Residual volume


Expiratory reserve volume

Vital capacity
Inspiratory reserve volume
Expiratory reserve volume

Tidal volume

Functional residual capacity
Total lung capacity
Inspiratory Capacity


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What are the value of preop PFTs?
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What are the value of preop PFTs?

• Indices of the dynamic function of the patients
  lungs
• Provides objective data for quantitating the
  degree of respiratory dysfunction
• Helps identify patients with abnormal lung
  function in order to take steps to alter their
  outcome
• Bronchodilators
• Leave intubated

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For instance

• An FVC of 1 liter is needed to effectively cough
• The higher the incision is (towards the
  diaphragm) the more impact there will be on the
  patients pulmonary function

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Who needs PFTs Preop?

• Patients with any evidence of chronic pulmonary
  disease
• Smokers with a history of persistent cough
• The elderly (gt70 years)
• The Morbidly Obese

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What are the indications for obtaining PFTs in
this case?

• Patients with chest wall and spinal deformities
• Patients for thoracic surgery
• Patients for upper abdominal surgery

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What are the indications for obtaining PFTs in
this case?

• Remember about the type of surgery!

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Before we look at the classic patterns of
obstructive and restrictive lung disease, lets
look at the volumes and capacities a little
closer.
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There is a lot of data reported out on a PFT test

• The only numbers to be really concerned with are
• FVC
• FEV1
• FVC / FEV1 ratio
• FEF25-75

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A forced vital capacity maneuver
Vol (L)
1
2
3
5
4
0
Time (sec)
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A forced vital capacity maneuver
Vol (L)
1
2
3
5
4
0
Time (sec)
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A forced vital capacity maneuver
Vol (L)
1
2
3
5
4
0
Time (sec)
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A forced vital capacity maneuver
Vol (L)
1
2
3
5
4
0
Time (sec)
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A forced vital capacity maneuver
FVC
Vol (L)
1
2
3
5
4
0
Time (sec)
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A forced vital capacity maneuver
FEV1
Vol (L)
1
2
3
5
4
0
Time (sec)
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A forced vital capacity maneuver
Vol (L)
FEF25-75
1
2
3
5
4
0
Time (sec)
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A forced vital capacity maneuver
FEV1
FVC
Vol (L)
FEF25-75
1
2
3
5
4
0
Time (sec)
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Forced vital capacity

• A measure of VOLUME
• How much air that can be forcefully exhaled
• NormallyVC
• Varies directly with height and inversely with
  age
• Reported in liters and of predicted
• Considered abnormal if lt 80 of predicted value

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Forced vital capacity

• Dyspnea usually present if lt 50 of predicted
  value
• Usually 50 of predicted is 2L
• With a reduced FVC, the patient may not be able
  to cough -gt atelectasis

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Forced vital capacity

• Surgical risk
• Need a FVC of about 1L to cough effectively
• Increased post op risk lt 2L
• Extreme increased risk lt 1L
• Upper abdominal surgery will diminish the FVC by
  about one half
• If 2L to start with, will be 1L post op

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Forced vital capacity

• Obstructive vs restrictive
• Reduced in obstructive
• Almost always reduced in restrictive
• lt15ml/kgassoc with prob of postop pulm problems
  b/o ineffective cough
• Concern with neuromuscular dis,quadriplegics

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Forced expiratory volume in 1 second (FEV1)

• A measure of FLOW
• If low, cant get the air OUT
• The amount of air that is forcefully exhaled in
  the first second
• Reported in liters and of predicted

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FEV1

• FEV1 reflects airway resistance in large airways
• May be reported as a volume
• Or as a percentage of the FVC, more about that
  later

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FEV1

• The FEV1 may be misleading if interpreted alone
  as it can be low in the face of a low FVC
• Considered abnormal if lt 80 of predicted value
• Dyspnea usually present if lt 50 of predicted
  value

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FEV1

• Surgical risk
• If less than 50 of predicted, dyspnea is likely
  and the patient is at risk for postop pulmonary
  complications
• Usually 50 of predicted is about 1.5L

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FEV1

• Obstructive vs restrictive
• FEV1 reflects airway resistance in large airways
• Considered abnormal if lt 80 of predicted value
• If after a bronchodilator the FEV1 increases by
  20 or more and the PaO2 increases
• The obstructive process is at least partially
  reversible and bronchodilators are indicated
• Also may place on bronchodilators if the patient
  improves symptomatically in the face of no
  improvement of the PFTs

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FEV1
FVC

• A ratio (may be referred to as the ratio)
• A measure of FLOW
• Reflects airway resistance in large airways

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The ratio

• Of all of the air that is forcefully exhaled
  (FVC) , how much is exhaled in the first second
  the FEV1
• You should exhale at least 80 of your air in the
  first second

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The ratio

• Reported as just that - the of air that is
  exhaled in the first second
• Everyone (too tall or too small) should exhale
  80 of their air in the first second

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The ratio

• Useful especially if the FRC is reduced
• If the FRC is reduced, as in restrictive lung
  disease, the absolute amount of air exhaled in
  the first second (FEV1) will also be reduced
• Or the FEV1 may be increased in restrictive
  disease
• BUT the of air exhaled in the first second
  compared to all of the air exhaled should be the
  same UNLESS there is obstruction

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The ratio

• If the FEV1 / FVC ratio is less than 80, there
  is probably obstruction
• If after a bronchodilator this ratio increases by
  20 or more and the PaO2 increases
• The obstructive process is at least partially
  reversible and bronchodilators are indicated
• Also may place on bronchodilators if the patient
  improves symptomatically in the face of no
  improvement of the PFTs

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Forced midexpiratory flow (FEF25-75)

• Sometimes termed the maximal midexpiratory flow
  rate (MMEF)
• A measure of FLOW
• Measures flow rate over the middle half of
  expiration
• Should be reported as L/sec and as of predicted

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FEF25-75

• It is less effort dependent compared to the FEV1
  / FVC ratio
• It may detect closure of small airways better
  than the FEV1 or FEV1 / FVC ratio

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FEF25-75

• Normal values vary widely
• Varies with age, ht, wt
• Surgical risk
• Increased postop risk if FEF25-75 is less than
  about 0.6 L/sec

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FEF25-75

• Obstructive vs restrictive
• It may detect closure of small airways better
  than the FEV1 or FEV1 / FVC ratio
• But if the FEV1 / FVC ratio is greater than about
  75 of predicted, the FEF25-75 is usually normal

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Some normals to remember

• FVC 2.8 - 4 L
• FEV1 gt80 of predicted
• FEV1 / FVC ratio gt80
• NOT OF PREDICTED
• FEF25-75 gt80 of predicted

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What are the classic patterns of obstructive and
restrictive lung disease?

• Obstruction
• Restriction

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What are the classic patterns of obstructive and
restrictive lung disease?

• Obstruction
• FVC Normal or decreased
• FEV1 Decreased
• FEV1/FVC Decreased

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What are the classic patterns of obstructive and
restrictive lung disease?

• Restriction
• FVC Decreased
• FEV1 Normal or increased
• FEV1/FVC Normal

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Why do we need to know this?

• Planning ahead for your approach to care will
  help you in the long run!
• Anticipation of problems is one of the goals that
  we include in our planning.

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This case

• FVC
• Pre 1.42 L (44)
• Post 1.73 (54)
• 22 change with albuterol
• FEV1
• Pre 0.79 L (33)
• Post 0.99 (42)
• 25 change with albuterol
• FEV1 / FVC ratio
• Pre 56
• Post 57
• 2 change with albuterol
• FEF25-75
• Pre 0.39L (15)
• Post 0.50L (19)
• 28 change with albuterol

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And the answer is?

• Mixed obstruction and restriction with some
  reversible component of the obstruction

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The ABG

• pH 7.41
• PaCO2 48 torr
• PaO2 68 torr
• HCO3 30 mEq/L
• SaO2 93

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And the answer is?

• Compensated respiratory acidosis

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Effects of age on the PaO2

• 60 yo PaO2 gt 80 torr
• 70 yo PaO2 gt 70 torr
• 80 yo PaO2 gt 60 torr
• 90 yo PaO2 gt 50 torr

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The care plan

• Goal
• Successfully control airway
• Prevent intraop bronchospasm
• Prevent postop pulmonary morbidity (and
  mortality!)

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The care plan

• Preop
• Hydration
• Patient education
• Bronchodilators
• What is a theophylline level going to help you
  with?
• Steroids?
• Antibiotics?
• All meds the day of surgery except for the
  diuretic (?)
• All inhalers to OR

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The Care Plan

• Preop
• What is the best anesthetic approach for the
  procedure?
• Will the patient agree?
• Anxiolysis

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The care plan

• Induction
• Concern about the airway
• If elect to induce anesthesia prior to
  intubation, blunt the airway reactivity prior to
  instrumentation of the airway
• Bronchodilators
• Volatile anesthetic
• Lidocaine IV
• Ketamine
• Propofol/Thiopental
• Narcotics ???
• Remember the patient has comorbidities

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The care plan

• Postop
• Leave intubated and extubate only after meeting
  extubation parameters
• Use epidural
• All the time preventing bronchospasm
• Bronchodilators

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Maintenance

• Tailor your choices to the patient response.
• Watch the airway pressures
• Watch the ETCO2
• Watch the SaO2

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Postop pulmonary complications

• 45 - 76 of all postop patients
• About 11 of pts undergoing abdominal operations
• Atelectasis and/or infections
• Pts with pul dx about 26 suffer pul
  complications
• Without pul dx about 8 suffer pul complications

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Postop pulmonary complications

• Higher incidence of postop pul complications in
  patients having surgery near the diaphragm
• Thoracic 40 - 50
• Upper abd 20 - 30
• Lower abd 5 - 10

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Postop pulmonary complications

• Primary factor leading to postop complications
  decreased lung volumes
• Causes
• Shallow, monotonous, sighless breathing due to
  pain, anesthetics, adjuncts
• With just a GA Decrease in the FRC with V/Q
  mismatch
• Sighs increase surfactant
• Decrease surfactant airway collapse
• Vertical incision more of a problem than
  transverse

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Postop pulmonary complications

• Physiology of postop lung volumes
• Decrease lung volume -gt increased lung recoil -gt
  lungs require a higher inflation pressure to
  achieve the same volume
• Increased lung recoil decreased transpulmonary
  pressure at the resting lung volume -gt decreased
  lung compliance stiffer lungs

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Postop pulmonary complications

• Physiology of postop lung volumes
• Normal Closing volume (CC) lt FRC
• Postop Breathing pattern leads to a decreased
  FRC
• When FRC is lt CC dependent airways close
  throughout tidal volume breathing -gt increased
  ventilation to upper lung zones with higher
  perfusion to lower lung zones ventilation -
  perfusion (V/Q) mismatch
• As trapped air is absorbed -gt atelectasis -gt more
  V/Q mismatch, possibility of pneumonia

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Postop pulmonary complications

• Physiology of postop lung volumes
• FRC decreases with 2 peaks
• Up to 2 hrs postop due to effects of the
  anesthetic and adjuncts
• Postop day 1 due to narcotics, pain
• Returns to normal in about 5 days postop

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Postop pulmonary complications

• Physiology of postop lung volumes
• Postop
• Tidal volume decreases about 20 and RR increases
• VC decreases 25 - 75 for the first 24 - 48 hrs
• Mostly from decrease in ERV
• Normalizes in about 1 - 2 weeks
• ERV decreases 25 with lower abdominal surgery,
  decreases 60 with upper abdominal surgery
• Need VC of at least 1 L to cough

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FLOW VOLUME LOOPS

• WHAT ARE THEY?
• Studies used for detection of intrathoracic or
  extrathoracic disorders/obstructions
• Recordings are done during inspir expir expir
  data is seen to be more valuable

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FLOW VOLUME LOOPS
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FLOW VOLUME LOOPS

• With FVC, PEF occurs in early part of expiration,
  max expir flow rate progressively dec until RV is
  reached. After approx 25 of VC is exhaled,flow
  maximum cant be increased. This effect is more
  pronounced in pts with airway obstruction.
• http//www.lib.mcg.edu

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FLOW VOLUME LOOPS
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FLOW VOLUME LOOPSINTRATHORACIC OBSTRUCTION
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FLOW VOLUME LOOPSEXTRATHORACIC OBSTRUCTION
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FLOW VOLUME LOOPS

• Another method of measuring FVC and FEV1
• Some new anesthesia machines incorporate this
  option into their functioning

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The importance of PFTs

• Thank you.