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Flashcards in PFTs Deck (28)
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1
Q

What are the types of PFTs?

A

Spirometry
Lung Volumes
Diffusion Capacity

2
Q

What is spirometry?

What is the primary measurement?

A

measures how an individual inhales or exhales volume of air as a function of time

Primary measurement in spirometry is either volume or flow

3
Q

What are the indications for spirometry?

A

Detecting & quantifying pulmonary impairment in cardiopulmonary diseases

Following the evolution of diseases & monitoring response to therapy

Monitoring the effects of environmental, occupational & drug exposures associated with lung injury

Assess preoperative risk

Assessing disability & impairment

4
Q

What are the primary spirometric indices?

What else can be found with spirometry?

A

Forced Vital Capacity (FVC)
Forced Expiratory volume in 1 sec (FEV1)
Ratio FEV1/FVC

Flow-Volume Loop

5
Q

How is the FVC test performed

A

having patient inhale to TLC & make a maximally forced exhalation into a spirometer

6
Q

How is Exhaled volume measured in spirometry?

How is flow measured?

A

exhaled volume is measured as a function of time (volume-time curve)

Flow is also measured & displayed as function of exhaled volume (flow-volume loop)

7
Q

How are patients classifed with spirometry?

A

Normal
Airflow obstruction
Restriction

8
Q

What are the three types of ventilatory defects?

A

Obstructive Ventilatory Defects
Restrictive Ventilatory Defects
Mixed Ventilatory Defects

9
Q

what are obstructive ventilatory defect?

A

decreased expiratory flows compared with a healthy persons

Early airway obstruction begins in the small airways & tends to reduce flows at lower lung volumes

Progressive slowing of expiratory flow is reflected in the concave shape on flow-volume curve

10
Q

What is the primary marker for presence of airway obstruction?

A

FEV1/FVC ratio

FEV1/FVC<70% predicted

11
Q

How is airway obstruction classified?

A

using the FEV1%

12
Q

What is FEF25-75?
How is it useful?
How can it be used to diagnose airflow obstruction?

A

average forced expiratory flow rate over the mid 50% of FVC

helpful in diagnosing obstruction, but dependent on FVC

, a reduced FEF25-75 <60% & FEV1/FVC in low-normal range can confirm airflow obstruction

13
Q

What is the degree o severity in obstructive defects using FEV1% pred?

A

mild= FEV1% > 80%
moderate = FEV1% 50-79%
severe = FEV1% 30-49%
very severe <35%

14
Q

What is bronchodilator response?

How is the test performed?

A

used for patients with obsructive lung disease

obtaining baseline spirometry
administering SABA, waiting 15 mins
then repeat the spirometry

15
Q

What is an improvement when administering a bronchodialtor response?

A

An improvement in FEV1 or FVC of 12% & 200ml from baseline is considered a positive response

Lack of response does not preclude a clinical response

16
Q

What are restrictive defect characterized by?
why?
What is suggestive of a restrictive defect?

A

reduced FVC

reduced because of the smaller absolute lung volumes

FVC < 80% predicted is suggestive of a restrictive defect

17
Q

When would you obtain lung volume to confirm restrictive defect?

A

If airway obstruction is present & FVC is low, a defect maybe present

Would recommend obtaining lung volumes to confirm the restrictive defect

18
Q

What are differentials for restrictive lung disease?

A

Pleural Disease
Parenchymal Lung Disease
Chest Wall Disease
Neuromuscular Disorders

19
Q

When are lung volume test used?

A

diagnose a restrictive lung disease & to determine the severity of the impairment

To help clarify whether a decrease in FVC is due to restriction or a consequence of air trapping due to airflow obstruction

20
Q

What is restrictive lung disease defined as in lung volume test?

A

Restrictive lung disease is defined as a reduction in lung volumes, particularly VC & TLC

21
Q

What are TLC ranges in normal restrictive lung diseases and obstructive lung diseases?

A

TLC Normal Range is 80-120% predicted

Restrictive Defect
TLC < 80% predicted

Obstructive Defect
TLC > 120% predicted

22
Q

What does diffusion capacity represent and measure?

A

Represents the gas exchange capabilities of the lung

Measures the ability of gas to diffuse across the alveolar-capillary membrane using carbon monoxide (DLCO)

23
Q

What does diffusion capacity depend upon?

A

Alveolar-capillary membrane
Hemoglobin concentration
Cardiac output

24
Q

What is a decreased DLCO<80% predictive of?

A

Obstructive Lung Disease
Parenchymal Lung Disease
Pulmonary Vascular Disease
Anemia

25
Q

What is a increased DLCO> 120% predictive of?

A

Asthma (maybe also normal)
Pulmonary Hemorrhage
Polycythemia
Left to Right Shunt

26
Q

What is a systematic way to interpret spirometry?

A

Look at the Force Vital Capacity (FVC) to see if its within normal limits

Look at the FEV1 & determine if it is within normal limits

If both FVC & FEV1 are normal, then you do not have to go any further

If the FEV1/FVC is <70%, you probably have an obstructive defect
Severity can be determined by the FEV1%

If FEV1/FVC is >88% and/or FVC <80%, you probably have a restrictive defect & would consider obtaining lung volumes and/or diffusion capacity

27
Q

What is a systematic way to determine Lung volume testing?

A

If the TLC < 80% predicted, then there is a restrictive ventilatory defect

If the TLC >80% predicted, but the FVC <80%, the patient does not have a restrictive defect

If the TLC >120% predicted, then there is a an obstructive ventilatory defect

28
Q

when would you order DLCO?

A

To help differentiate asthma from emphysema

To help in the evaluation & determine, the severity of interstitial lung disease or restrictive lung disease

Evaluate cardiovascular disease