*Tidal Volume (Vt)

*Inspiratory reserve volume (IRV)

*Expiratory reserve volume (ERV)

*Residual volume (RV)

*Vital Capacity (VC)

*Inspiratory Capacity (IC)

*Functional Residual Capacity (FRC)

*Amount of air that can be forcefully inspired after a normal tidal volume inhalation.

*Normal IRV= 3,100

*TLC is the maximum amount of air the lung can hold.  

*Normal TLC= 6.000

*TLC= VT+IRV+ERV+RV

*TLC= IC+FRC

What is Tidal Volume? What is a normal tidal volume?

*VT= Amount of air moved into or out of the lungs

*Resting tidal volume is the normal volume of air inhaled or exhaled in one breath

*Normal VT= 500mL

*ERV= Amount of air that can be forcefully exhaled after a normal VT exhalation

*Normal ERV= 1,200mL

*RV=Amount of air in the lungs after a forced exhalation

*Normal RV= 1200mL

*MV=Amount of air moved during normal inspiration and expiration in one minute

*VT x RR= MV

*Normal MV= 6,000mL/min

*Amount of air forcefully exhaled after maximal inspiration

*VC= IRV+VT+ERV

What is "slow" vital capacity? (SVC)

*The VC when maximal effort is made to exhale as rapidly as possible.

*If FVC is timed, it is possible to measure forced expiratory volume per unit of time

*Ex: FEV1 is forced expiratory volume over one second. Normal is ~80% of FVC.

*Combination of tidal volume and inspiratory reserve volume

*IC= VT+IRV

*Combination of expiratory reserve volume and residual volume

*FRC=ERV+RV

*AV or VA is the effective ventilation 

*Defined as volume of fresh gas entering the alveoli per minute 

*Component of ventilation that undergoes molecular gas exchange with the pulmonary blood

*Normally, VA is less than MV due to the portion of gases that are inhaled and fill the respiratory passages but do not participate in gas exchange with pulmonary blood.

*VA= RRxVD

*Normal= 4,200mL

*Deadspace ventilation (VD) is the wasted portion of total ventilation that does not undergo molecular gas exchange with the pulmonary blood

*VD increases slightly with age

*Anatomic dead space

*Physiologic dead space

*Anatomic areas of the respiratory tract that do not participate in gas exchange

*Nasal passages, pharynx, trachea & bronchi

*Relatively constant & predictable with spontaneous respirations in normal size and body weight individuals

*Normal= 2.2ml/kg

What is the physiologic dead space?

*The gas volume in the alveoli with reduced or no function due to diminished blood flow through the corresponding pulmonary capillaries

*Wasted ventilation

*Variable and difficult to measure in instances of ventilation/perfusion mismatch

*Provides objective, standardized measurements of respiratory function

*Identifies patients at increased risk for postop pulmonary complications

*Allows for optimization of physical status before surgery 

*Lowered BP

*Altered position

*Positive pressure ventilation

*Surgical stress

*PFTs are helpful only as general indicators

*Studies have not conclusively proven that PFTs are accurate predictors of postoperative morbidity and mortality.

*Assess activity tolerace

*Ability to lay flat

*breath sounds

*symmetry

*Physical development- body habitus

*Assess infectious processes

*Mediastinal shifts

*Enlarged heart size

*Atelectasis

*Adequacy of ventilation (PaCO2)

*Adequacy of oxygenation (PaO2)

*Oxygenation is not a good predictor of ventilation (Pulse oximetry is not useful to predict ventilation)

*The cornerstone of PFT measurements 

*Performed by having the patient fill his lungs maximally, then exhale forcefully into the spirometer until the RV is reached 

*Results are based on patients ability to cooperate

*VT 

*RR

*MV

*Can be used to estimate the patients ventilatory reserve

*The patient must be able to cooperate to obtain accurate readings

*Important clinical values when looking at obstructive and restrictive disease

*Normal young patients can achieve a ratio of 80-85% (Can't be 100% because there will always be a RV)

*Decreased FEV1/FVC ratios are hallmark indicators for obstructive diseases 

*Forced expiratory flows between 25-75% of exhaled volume (FEF 25-75%)

*AKA Maximum Mid Expiratory Flow Rate (MMFR or MMEFR)

*Represents the average airflow during the 'effort independent' portion of FVC.

*Can assess small airway function

*It is a relative indication of FVC

*Useful with spontaneously breathing uncooperative or anesthetized patients

*Good indicator of muscle strength for ventilation

*FVC<50% Predicted

*FEF 25-75% <50% predicted

*FEV1/FVC <50% predicted

*Helium dilution

*Nitrogen washout

*Body plethysmography

*PT breathes 100% O2 from a reservior

*All exhaled gas is collected

*Using the total gas volume, initial nitrogen concentration and final nitrogen concentrations, the FRC can be calculated.

*Pt is seated in closed chamber

*Inspire/expire against an obstructed airway

*Manometers measure mouth pressure & body chamber pressure

*Boyles Law: P1V1=P2V2

*Temperature is constant, the pressure of the gas is inversely related to the volume.

*Body Plethysmography

*Independent of the mechanics of the lung airways

*Gas dilution techniques can give falsely low FRCs with obstructive disease.

*THUS body plethysmography is useful in assessing pts with obstructive diseases.

*FEV1 should normally be >70% of FVC

*FEV1 <70% indicates disease process

*Healthy adult- 45 seconds

*Moderate disease- 30 seconds

*Severe disease 20 seconds

*Total volume of air that a patient can move in and out of their lungs per minute

*Determined by measuring the total ventilation while the patient performs a maximal breathing effort over 12 seconds

*Called the breathing reserve 

*(MVV-MV=Breathing reserve)

*Dyspnea

*Reduction in exercise tolerance

*Increased morbidity, especially with thoracic surgery

*Patient forcibly exhales completely, then immediately and forcibly inhales to capacity 

*The expired and inspired volumes are plotted on the x axis

*The flow is plotted on the y axis

*Configuration is very significant

*They can be analyzed and reflect obstructive or restrictive diseases.

*Normal lungs show linear decrease with volume over most of the VC range

*The curve is linear

*Limitations to expiratory and inspiratory flow

*Flat ovid loop

*Fairly normal peak respiratory flows

*linear decrease in flow

*Decreased lung volume

*Equal flow at all volumes

*appears as a normal miniature loop

*Shape of curve independent of pt effort

*Determined by elastic recoil of lungs (75% of TLC to RV)

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What pattern does letter A represent?

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What pattern does letter B represent?

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What pattern does letter C represent?

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What pattern does letter D represent?

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What pattern does letter E represent?

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What pattern does letter F represent?

*The Single Breath Carbon Monoxide Test (DLco)

*Seated upright

*Breathes through a 3 way valve

-Breathes room air first

-Reservior with 0.3% CO, 21% O2, 10% helium

-Patient limb

-Valve to room air- patient expires to residual volume or maximum expiration

-Valve to reservoir-pt inspires maximally and holds breath for 10 seconds

-The end expiratory gas (free of dead space gas) is collected and analyzed

*High affinity for hemoglobin (200x greater than O2)

*Ergo almost no CO will remain dissolved in plasma

*Not usually found in high concentrations within pulmonary capillary blood

*CO uptake is not limited by a decrease in its pressure gradient across the membrane but rather by the diffusion characteristics of the alveolar-capillary membrane and hemoglobin content of red blood cells in contact with alveolar air

*Perfusion-limited transfer occurs with gases like N20

*Decreased surface area available for diffusion (Emphysema, Lobectomy)

*Increase in thickness of the alveolar-capillary barrier (Fibrosis, interstitial or alveolar edema)

*Decreased hemoglobin

*A ventilation-perfusion mismatch (Pulmonary Embolus)

*Increased alveolar-capillary surface area available for diffusion such as exercise and elevations in pulmonary artery pressure

*Increased red blood cell volume (Polycythemia)

*Supine position

*With increased alveolar PCO2 level

*Does not help in evaluating most abnormalities of gas exchange

*False results can be from: Smoking (causes excessive blood levels of CO, diffusion is inhibited via a decreased pp gradient), Rupture typmanic membrane (allows CO to escape from a non pulmonary route)

*Decreased DLco does not account for clinically significant hypoxemia at rest.

*Diffusion reserve of the lung is such that DLco or DL02 can be greatly reduced without a decreased paO2

*The diffusion capacity for CO is not equal to the diffusion capacity of oxygen

*FVC <50% predicted

*FEV1 <50% predicted or <2L/M

*MVV <50% predicted or <50L/M

*DLco <50% predicted

*RV/TLC >50% 

*25-50%

*1-2

*25%

*2 weeks

*20%

*24 hours

*2 weeks

*33%

*Small airway closure

*Less sighs per hour

*Decreased clearance of secretions

*Normal tidal volume patterns are altered

*Splinting from pain is additive

*Need FRC or 15mL/kg to cough (most say 20)

*Need a NIP of negative 20 to cough

*Upper abdmoninal sugery

*Thoracic surgery

In obstructive disease:

-VC is ______

-Maximum expiratory flow (MEF) _____

-MVV ______

-FRC _____

-RV ______

-FEV1 ______

-FEV1/FVC ______

-TLC ______

*VC normal or decreased

*MEF decreased

*MVV decreased

*FRC Increased

*RV Increased

*FEV1 Decreased

*FEV1/FVC decreased

*TLC normal or increased

*Upper airway disease

*Peripheral airway disease

*Pulmonary parenchymal disease

*Pharyngeal and laryngeal tumors, edema, or infection

*Foreign bodies

*Tumors, collapse and stenosis of the trachea

*Bronchitis

*Bronchiectasis

*Bronchiolitis

*Bronchial asthma

*Loss of airway support and elastic recoil

*Emphysema

With restrictive airway disease...

-Vital capacity ______

-Expiratory flow rate ______

-MVV _______

-TLC ________

-FRC ______

-RV ______

-FEV1 ________

-FEV1/FVC ______

*Vital capacity decreases

*Expiratory flow rates relatively normal

*MVV relatively normal

*TLC decreased

*FRC Decreased

*RV decreased

*FEV1 normal or decreased

*FEV1/FVC normal or increased

*Interstitial lung disease

*Space-occupying lesions

*Pleural disease

*Chest wall disease

*Extrathoracic conditions

*Interstitial pneumonia

*Fibrosis

*Pneumoconiosis

*Granulomatosis

*Edema

*Pneumothorax

*Hemothorax

*Pleural effusion

*Empyema

*Fibrothorax

*Injury

*Kyphoscoliosis

*Spondylitis

*Neuromuscular disease (MS, GB)

*Obesity

*Peritonitis

*Pregnancy

*Ascites

*Diffuse interstitial disease (Pulmonary edema, Intersitial pneumonia, lung fibrosis)

*Reduced lung volumes

*Parenchymal destruction (Emphysema)

*Reduced pulmonary vascular bed (Thromboembolism, V/Q mismatch)

*Pulmonary resection

*Anemia

*Carboxyhemoglobinemia (burn patients)