Transcript Pulmonary Function Testing and ARDS

Pulmonary Function Testing
&
ARDS
IM Residency Lecture Series
1/26/05
Evan T. Lukow D.O.
Goal:
To understand how to interpret Pulmonary
Function Tests and how they relate to certain disease states.
• The Resident will:
• Understand the basic physiology behind PFT’s and how they relate
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to lung function.
Understand what the specific components of PFT’s are.
Learn to recognized specific pulmonary disease by what PFT
values are obtained.
Recognized patterns of flow-loop diagrams as they relate to
respiratory pathology.
Develop a basic understanding of Acute Respiratory Distress
Syndrome and its current treatment.
Basic Lung Physiology:
• Pulmonary Function Testing evaluates the concepts of
normal lung function:
• Mechanics (airflows and lung volumes).
• Ventilation-Perfusion relationships.
• Ventilation – the process of generating the forces required to move the
needed volumes of air from the atmosphere to the alveoli to meet the
overall needs of the body.
• Perfusion – the amount of blood that is oxygenated at the alveoli and
transported to the tissues to meet the metabolic demands of the body.
• Diffusion/Gas exchange.
• Respiratory muscle (bellows) strength.
Lung Volumes:
Why PFT’s?
• Screening for obstructive or restrictive lung disease.
• Pre-op evaluation of a patient:
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Patients older than 65
Known pulmonary disease
Obesity
History of smoking, cough, or wheeze
Large anesthesia requirements (time)
Extensive abdominal of thoracic procedures
• When weaning a patient from the ventilator:
• Vital capacity of 10-15 mL/Kg is sufficient reserve to extubate.
• Monitoring progression and treatment of pulmonary
disease.
What are PFT’s?
• Four main components:
• Spirometry
• Bronchoprovocation
• Flow-Volume Loops
• Diffusing Capacity
What do PFT’s give us?
Obstructive vs. Restrictive
Common Obstructive Lung
Diseases
•Asthma
•Asthmatic bronchitis
•Chronic obstructive bronchitis
•Chronic obstructive pulmonary
disease (COPD includes
asthmatic bronchitis, chronic
bronchitis, emphysema and the
overlap between them).
•Cystic fibrosis
•Emphysema
Common Restrictive Lung
Diseases
•Idiopathic pulmonary
fibrosis
•Interstitial pneumonitis
•Infectious inflammation
(eg, histoplasmosis,
mycobacterium infection)
•Sarcoidosis/beryllium
disease
•Thoracic deformities
•Congestive heart failure
•Neuromuscular diseases
Spirometry:
Normal
Spirogram
Obstructive
Spirogram
RV, FRC, and TLC are increased
VC is decreased
Expiration is prolonged FEV1/FVC less than 75%
Restrictive
Spirogram
ALL lung volumes are reduced
Tidal volume is rapid and shallow
FEV1/FVC is normal, because both values are decreased
RULE of THUMB:
•Normal PFT Outcomes - > 85 % of predicted values
•Mild Disease - > 65 % but < 85 % of predicted values
•Moderate Disease - > 50 % but < 65 % of predicted values
•Severe Disease - < 50 % of predicted values
Flow-Volume
Profile:
In a simplistic way, respiratory disease can be classified as obstructive or restrictive
processes. Obstructive disorders, such as emphysema or asthma, are characterized by
airflow limitation, have increased lung volumes with air trapping, and have normal or
increased compliance (based on pressure volume profile). In contrast, restrictive disorders
such as pulmonary fibrosis are characterized by reduced lung volumes and an increase in
overall stiffness of the lungs (with reduced compliance)
Bronchoprovocation:
• Used to define whether airway hyper-reactivity cause
pulmonary complaints.
• Inhalational challenge tests, histamine and methacholine,
are used along with standard spirometry to determine if
pulmonary function is affected after administration of these
airway irritants.
• If there is a 20% decrease in FEV1, the test is considered
positive for airway hyper-reactivity.
• Sensitive for Bronchial Asthma.
• False positives with COPD, URI, Allergic rhinitis, CHF.
Flow-Volume Loops:
• The flow-volume loop is generated by continuously
recording flow and volume with an electronic spirometer
during a forced inspiratory and expiratory VC maneuver.
• The shape of the loop reflects the status of the lung
volumes and airways throughout the respiratory cycle.
• Characteristic changes occur in restrictive and in
obstructive disorders.
• The loop is especially helpful in detecting laryngeal and
tracheal lesions.
NORMAL
RESTRICTIVE
(i.e. Sarcoidosis,
Kyphoscoliosis)
OBSTRUCTIVE
(i.e. COPD, Asthma)
FIXED UPPER
AIRWAY
OBSTRUCTION
(i.e. Tracheal Stenosis,
Goiter, B/L Vocal Cord
Paralysis)
Variable ExtraThoracic
Obstruction
Variable IntraThoracic
Obstruction
(i.e. Vocal Cord Paralysis)
(i.e. Tracheomalacia)
Diffusing Capacity:
DLCO
• Used in conjunction with spirometry to evaluate the
amount of damage at the cellular level.
• Take Home Points:
• DLCO is decreased with decreased surface area, decreased
hemoglobin, interstitial lung disease, and pulmonary vascular
disease.
• Please reference handout for more specific breakdowns.
ARDS: Acute Respiratory Distress
Syndrome
Basics of ARDS:
• ARDS is respiratory failure with various acute pulmonary
injury.
• Characterized by the triad of:
• Hypoxemia
• Respiratory Distress
• Non-Cardiogenic Pulmonary Edema
Etiology:
• Airway
• (Drowning)
• Circulation
• (Sepsis) – MOST COMMON
• Neurogenic
• (Head Trauma)
Anteroposterior chest radiograph of a 50-year-old patient with acute respiratory
distress syndrome 12 hours after intubation. Bilateral, diffuse alveolar infiltrates
are consistent with pulmonary edema. Note the absence of cardiomegaly and
pleural effusions, which are often seen in patients with cardiogenic pulmonary
edema.
Pathophysiology:
• The initial insult is at the alveolar capillary membranes.
• These membranes become leaky resulting in alveolar
pulmonary edema.
• This edema results in:
• Reduced lung compliance
• V/Q shunt formation
• Hypoxemia
• Pulmonary hypertension
Clinical Presentation:
The FOUR phases of ARDS
• Phase 1:
Hyperventilation, cyanosis, respiratory alkalosis, and
normal CXR
• Beginning at time of initial insult, lasting several hours.
• Phase 2:
Tachypnea, respiratory distress, marked hypoxemia,
alkalosis, interstitial edema on CXR.
• Phase 3:
• Phase 4:
Hypoxemic Respiratory Failure
Cardiac Arrest
• Phases 2-4 all have variable timeframes, can progress over hours to days.
Treatment:
• TREAT the underlying disorder!!!
• Sepsis – Broad Spectrum Antibiotics
• Support Gas Exchange – Mechanical Ventilation with
PEEP
• Maintain Organ Perfusion – use lowest intravascular
volume possible while still maintaining organ perfusion
• Inotropic Therapy if needed
• Numerous studies have focused on the use of multiple
ventilation approaches and pharmacologic treatments with little
success.
Mortality/Prognosis:
• Mortality – 50%
• Infection is the #1 cause
• If patient survives, recovery of nearcomplete lung function is expected.
References:
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American Thoracic Society: Standardization of Spirometry, 1994 Update. Am J
Respir Crit Care Med 1995 Sep; 152(3): 1107-36
American Thoracic Society: Lung function testing: selection of reference values and
interpretative strategies. Am Rev Respir Dis 1991 Nov; 144(5): 1202-18
Crapo, R.O., Morris, A.H., and Gardner, R.M. 1981. Reference Spirometric Values
Using Techniques and Equipment that Meet ATS Recommendations. Am. Rev. Respir.
Dis., 123:659-664
Kollef MH, Schuster DP. The acute respiratory distress syndrome. N Engl J Med
1995;332:27-37.
Ware LB, Matthay MA. The acute respiratory distress syndrome. N Engl J Med
2000;342:1334-1349.
Core Competencies
Oh what Fun!!!
• Case # 1. 59 yo white male with a 40 pack year
smoking history presents to the ER with
increasing dyspnea over the last several
months, and cough productive of brown
sputum. PFT values are shown below.
• Obstructive or Restrictive or Normal (circle one)
• Case # 1. 59 yo white male with a 40 pack year
smoking history presents to the ER with
increasing dyspnea over the last several
months, and cough productive of brown
sputum. PFT values are shown below.
• Obstructive or Restrictive or Normal (circle one)
• Why?
• Case # 2. 62 yo African American female
presents to the office with increasing SOB over
the last year. Patient is a non-smoker and has a
history of HTN. PFT values are shown below.
• Obstructive or Restrictive or Normal (circle one)
• Case # 2. 62 yo African American female
presents to the office with increasing SOB over
the last year. Patient is a non-smoker and has a
history of HTN. PFT values are shown below.
• Obstructive or Restrictive or Normal (circle one)
• Why?
• Case # 3. 45 yo white male is seen in the office
for follow-up for a recent ER visit. Patient was
out with buddies playing football and suddenly
became short of breath. He was treated with
nebulizers, steroids, and referred to you for
follow-up. PFT values are shown below.
• Obstructive or Restrictive or Normal (circle one)
• Case # 3. 45 yo white male is seen in the office
for follow-up for a recent ER visit. Patient was
out with buddies playing football and suddenly
became short of breath. He was treated with
nebulizers, steroids, and referred to you for
follow-up.
• Obstructive or Restrictive or Normal (circle one)
• Why?
The End
?Questions?