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Respiratory/Musculoskeletal > CM- PFTs and Mechanical Ventilation > Flashcards

CM- PFTs and Mechanical Ventilation Flashcards

1
Q

What are the 5 things PFTs evalulate in the clinical setting?

A
  1. assessment of patients pulmonary complaints
  2. define patterns of respiratory impairment
  3. serial evaluation to see if there is improvement or deterioration
  4. preop assessment to see if they can handle surgery
  5. measure effects of environmental/occupational exposures
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2
Q

What are the 4 categories of information gained from PFTs?

A
  1. Lung volumes and capacities
  2. Flow rates- max flow in airways
  3. Diffusion capacities- how well gas transfers from alveolus to pulmonary capillary
  4. Max inspiration pressure and max expiration pressure- measure strength of respiratory muscles
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3
Q

What are the 4 most important lung compartments to assess in a patient?

A
  1. TLC- volume of gas in lungs after max inspiration
  2. RV- volume in lungs after max expiration
  3. VC- volume of gas expired after inspiring to max, and then expelling to RV (TLC-RV)
  4. FRC- volume of gas in the lungs at resting state
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4
Q 
What is the standard lung volumes and capacities for a 70kg adult for:
TLC
VC
RV
FRC
A 
TLC= 6L
RV = 1.5L 
VC = 4.5L
FRC = 3L
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5
Q

What is spirometry?
Where can it be performed?
What are the 3 main types?

A

It is a test performed at clinics or the hospital that can give information about the capacity of the lungs.
1, Water-seal- move the bell up with expiration and down with inspiration , the vertical distance gives a specific volume
2. Dry rolling seal
3. Pneumotachometer- signal proportional to gas flow

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6
Q

What 4 compartments does spirometry give information about?

What can’t it give information about?

A
  1. FVC
  2. IRV
  3. TV
  4. ERV

It cannot record RV, therefore, you cannot figure out FRC or TLC.

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7
Q

What are the 2 main techniques for measuring lung volumes beyond those calculated by spirometry?

A
  1. Body plethysmography

2. dilutional lung volumes using He or N2 washout

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8
Q
  1. FRC- ERV = ______
  2. IC + FRC = _______
  3. VC + RV = ________
A
  1. RV
  2. TLC
  3. TLC
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9
Q

What can TLC confirm the presence of if it is reduced?

A

Restrictive lung disease

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10
Q

Describe body plethysmography.

A

Patient sits in a tight air-sealed box. Boyle’s law is applied: pressure x volume is constant at a given temperature.
As the patient inhales gas, the volumeof the lungs increase and the box pressure increases because the volume in the box decreases.
During expiration, lung volume decreases and box pressure decreases because gas volume increases.
We measure the change in pressure between inspiration and expiration to determine the FRC.

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11
Q

What are the 2 dilution tests to measures FRC?

A
  1. closed circuit He dilution

2. open circuit N2 washout

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12
Q

Describe the process of He dilution.

A
  1. a known volume of He is inhaled.
  2. He diffuses with the patients lung and equilibration occurs.
  3. Final concentrations of He are obtained.
  4. Helium is diluted by the volume of gas already in the lung and the concentration of expired gas reflects the initial volume of gas in the lungs (FRC)
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13
Q

Why might patients with COPD have a falsely low FRC?

A

He gas concentrates in the poorly ventilated areas (bullae) leading to a falsely low FRC when He is expired.

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14
Q

Describe the process of nitrogen washout.

A

The patient breaths 100% oxygen for a few minutes “washing out” the nitrogen from the lungs.
At the beginning of the test, the lungs have 75-80% nitrogen.
At the end of washout, they have about 1% nitrogen.
The initial concentration, amount washed out and final concentration of nitrogen are measrured and calculated to measure FRC.

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15
Q

Normal FEV1 is about ____% of FVC.

A

70%- most healthy patients exhale 70-80% of their FVC in one second
Normal FEV1/FVC ratio is greater than 70-80%

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16
Q

What would spirometry for COPD show?

A

Elastic recoil is reduced leading to reduced FEV1, FVC and FEV1/FVC ratio.

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17
Q

What would spirometry for asthma show?

A 
FEV1 is reduced and FEV1/FVC ratio is less than 70% because of airway inflammation and increased smooth muscle tone limiting airflow in expiration.
When B2agonist (albuterol) is inhaled, this can increase the FEV1 and FVC by more than 200mL and 12% increase in values.
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18
Q

What is a “significant bronchodilator response” with albuterol on the spirometry measurements?

A

Increase in either FVC or FEV1 by more than 200mL and 12% increase in these values.

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19
Q

What do restrictive lung diseases show for spirometry?

A

Reduced FEV1 and FVC but the ratio FEV1/FVC remains the same or is increased.

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20
Q

What are the reference “normal” values for PFTs based on?

A 
Anthropometric data (age, height, sex, weight, body surface area) and ethnic/racial backgrounds that match the patient and have been taken from "healthy" (no history of lung disease, smoking or pollution exposure)
"
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21
Q

What is the LLN?

A

Lower limit of normal- lowest 5th percentile can be calculated from 95% confidence interval to define “abnormal”

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22
Q

What happens to FEV1/FVC with age?

How does this affect “normal value” PFTs vs. LLN?

A

FEV1/FVC decreases with age due to natural loss of elasticity so using a fixed ratio of 70% to define obstructive lung disease may result in higher false positive rates of COPD and an underestimation of COPD in younger patients

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23
Q

What is FEF 25%-75%?

Which airways does it give info about?

A

Forced expiratory flow measures the expired airflow rate between 25% and 75% on forced expiratory spirogram.
It gives info about the status of medium and small airways.
It can detect beginning stages of obstruction in patients with normal FEV1.FVC/

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24
Q

What lab value gives information about early states of obstructive lung disease (while FEV1/FVC is still normal?

A

FEF25%-75%

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25
Q

For the flow volume loop, what is shown below the x axis? Above?

A

Expiratory curve is above the x axis and shows the flow from maximal inspiration (TLC) to maximal expiration (RV)
Inspiratory curve is below the x axis and shows the flow from maximal expiration (RV) to maximal inspiration (TLC)

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26
Q

Which part of the flow volume loop is changed for obstructive lung diseases like asthma and emphysema?

What is the most characteristic change associated with a restrictive lung disease?

A

Obstructive have scooped expiratory curves

Restrictive have narrow volumes

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27
Q

How is gas exchange capacity of the lung measured?

A

DLCO is a test to assess the rate of transfer (diffusion) of gas from the alveolus to the pulmonary capillary beds.

A small concentration of CO is inhaled by patients. Because CO has a high affinity for Hb, it will readily bind Hb in erythrocytes.

DLCO Sb (single breath) is where the patient breathes at tidal breath, then unforced expiration to RV, then rapid inspiration and breath hold for 10 seconds of a 0.3 percent CO and He tracer. Then the person exhales. 
Remaining CO and He are measured.
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28
Q

What are the 3 major factors that influence diffusing capacity?

A
  1. actual thickness of alveolar capillary membrane
  2. number of functioning alveolar-capillary subunits
  3. available Hb to bind CO
29
Q

What are the 3 respiratory disease processes that lead to decreased DLCO?

A
  1. emphysema
  2. interstitial lung disease- fibrosis, thickening
  3. pulmonary vascular disease- hypertension PE
30
Q

Why don’t asthma or chronic bronchitis decrease the DLCO?

A

Because they affect the airway only and do not affect the lung parenchyma that much

31
Q

What are the effects of anemia and polycythemia on the DLCO?

A

Anemia- decreased DLCO because less Hb to pick up gas

Polycythemia- increased DLCO because more Hb to pick up gas

32
Q

What do max inspiratory pressure and max expiratory pressure give you information about?

It is important to test for this in patients with what disorders?

A

The strength of the respiratory muscles - especially important to test in patients with neuromuscular diseases (poliomyelitis, ALS, myasthenia gravis, Guillian-Barre)

33
Q

How is MIP measured? What muscle does it measure the strength of?
What is the normal max for a man? woman?

A

The patinet expires to RV and then inspires maximally into a pressure gauge on a manometer for one second.

It measures the strength of the diaphragm.

Normal max for a man = -100 cm H20
Normal max for a woman = -80 to -90 cm H20

34
Q

How is the MEP measured? What does it measure the strength of? What is the normal MEP for men? women?

A

Patient inspires fully to TLC and then expires as forcefully as possible into a pressure gauge for 1 second.
It measures the expiratory muscles that are necessary to generate an adequate cough.

Men = +200 cm H2O
women = +125 cm H2O
35
Q

Why would VC and TLC be reduced in a person with neuromuscular disorder?

A

IRV is decreased because of weak diaphragm
ERV is decreased because of weak expiratory msucles
Therefore, VC is reduced because VC = TV + IRV+ERV.
TLC = VC + RV so because VC is reduced, TLC is also reduced

36
Q

What are the 7 steps for evaluating if a patient has an obstructive pattern on PFTs?

A
  1. Did they do the test correctly?
  2. Is FEV1/FVC below 70% or FEV1/FVC below LLN?
  3. Is the flow volume loop “scooped out” on expiratory limb?
  4. Determine severity by % predicted of FEV1
  5. Does it improve by 200mL or 12% with a bronchodilator
  6. Is TLC or RV elevated?
  7. Is DLCO low? (emphysema, ILD, pulm vasc)
37
Q

What percent predicted of FEV1 shows :

  1. mild
  2. moderate
  3. moderate severe
  4. severe
  5. very severe

Obstruction?

A
  1. below 70%
  2. 60-69%
  3. 50-59%
  4. 35-49%
  5. below 35%
38
Q

What are the diseases that show a restrictive pattern with PFTs?

A

PAINT
P- pleural disease ( mesothelioma, effusion)
A- alveolar disease (diffuse hemorrhage, pulm edema, eosinophilic pneumonia)
I- interstitial lung diseases (fibrosis, sarcoidosis, hypersensitivity pneumonitis)
N- neuromuscular disease

39
Q

What are the 6 steps for determining a restrictive lung problem using PFTs?

A
  1. Make sure the test was performed correctly
  2. FEV1 and FVC are both decreased but FEV1/FVC is normal or increased
  3. Obtain lung volume measurements - TLC should be markedly decreased (LLN)
  4. FVL- convex pattern with shortened volume
  5. Check DLCO- if it is low, it suggests ILD, pulmonary fibrosis, or pulmonary vascular disease
40
Q

How do you determine if something is a mixed obstructive and restrictive pattern?
What are 3 relatively common disorders with mixed patterns?

A
  1. The FEV1/FVC ratio should be reduced below 70% or LLN
  2. TLC is below 5% of predictive value

Sarcoidosis, scoliosis, obstructive lung disease

41
Q

What are the 3 isolated diffusion impairment defects?
Are they obstructive, restrictive, mixed?
What are the TLC and FEV1/FVC values of each?

A
  1. Emphysema (obstructive, low FEV1/FVC)
  2. ILD (restrictive, reduced FVC, reduced TLC)
  3. Pulmonary vascular disease (normal spirometry, isolated reduced DLCO)
42
Q

Describe negative pressure ventilation.

What are the drawbacks?

A

Replicates and augments normal spontaneous breathing.
It exposes the surface of the thorax to subzero pressure during inspiration. This expands the thorax decreasing pleural and alveolar pressure so air moves into the alveoli.

Expiration is passive and due to the elastic recoil of the respiratory system

Drawbacks:

  1. cumbersome and uncomfortable
  2. infrequently used
43
Q

Describe positive pressure ventilation.

What are the drawbacks?

A

A cuffed tracheal tube is placed and positive pressure is provided with mechanical presure. A soda lime absorber is connected to remove CO2.

Drawbacks:
1. excessive + pressure ventilation can cause pneumothoraces and collapsed lungs

44
Q

Where is mechanical ventilation used?
What is the general purpose?
Is it curative or supportive?

A

ER, ICU, operating rooms
It is used to eliminate CO2 and assist in inspiration of adequate oxygen while the patient recovers from acute illness.

  1. airway protection
  2. hypoxemia
  3. hypercapnia
  4. increased work of breathing
  5. neuromuscular disorders

IT IS SUPPORTIVE NOT CURATIVE

45
Q

A man is found with an empty bottle of morphine tablets next to him. Why might he need to be put on a ventilator?

A

Morphine suppresses the respiratory center, CO2 would have built up causing a respiratory acidosis.

46
Q

A young woman has myasthenia gravis. Why might she need ventilation?

A

She will have respiratory acidosis so she will need ventilation while treatment for MG with plasmapheresis occurs.

47
Q

What is the first step of mechanical ventilation?

A

Intubate the patient by inserting a tube in the mouth then through the vocal cords, and into the trachea. The balloon is inflated to seal the trachea except through the tube

48
Q

What are the 4 modes that can be set on the mechanical ventilator?

A
  1. Mode
  2. ventilation- tidal volume/RR
  3. Oxygenation- FIO2 delivered
  4. PEEP- positive end expiratory pressure that prevents atelectasis (collapse)
49
Q

What is meant by the mode of the mechanical ventilator?

What are the 2 different types? Which is used in most clinical situations?

A

The pattern of cycling used to drive gas flow from the ventilator to the patient.

  1. pressure cycled
  2. volume cycled- used in most clinical situations
50
Q

What is volume cycling?

A

Each breath delivers the same tidal volume despite changes in mechanical properties of the lungs

51
Q

What is pressure cycled ventilation?

A

A set pressure is delivered with each breath but does not always provide the same tidal volume because changes in mechanical lung properties will vary the number of breaths and breath tidal volumes

52
Q

What are the advantages of volume controlled ventilation?

A
  1. greater control over ventilation
  2. evidence based benefit in ARDS, ALI
  3. easier to measure mechanical properties
53
Q

What are the advantages of pressure controlled ventilation?

A
  1. greater patient comfort
  2. greater protection against VILI
  3. facilitates weaning off the device
  4. more effective support for some patients
54
Q 
Describe CMV (controlled mechanical ventilation). 
Is it volume cycled or pressure cycled?
Who typically receives this type of ventilation?
A

It is volume cycled.
Ventilator provides full support and does not allow the patient to support his own ventilation.
Between set breaths, the inspiratory valve closes so even if a patient tries to take a breath, they won’t be able to get one.

This is used for patients under anesthesia, comatose or those unable to make inspiratory effort.

55
Q

Describe assisted-control ventilation.

Is it volume or pressure cycled?

A

It is the most commonly used ventilation in ER and ICU.
It is like controlled mechanical ventilation EXCEPT there is a sensor that detects patient initiated breaths as a fall in pressure. When this occurs the ventilator assists the patient to provide a full tidal volume breath.

Ex. 12 bpm, 500ml tidal volume is set. If they breath spontaneously, for 20 breaths, each breath will get assisted up to 500ml
If the patient breaths 4 breaths, the machine will deliver 8 more breaths to reach the 12

56
Q 
Describe SIMV (synchronized intermittent mandatory ventilation).
Is it volume or pressure cycled?

What other type of mechanical ventilation is it often combined with?

A

It is a volume cycled ventilation where the ventilator delivers a preset number of BPM at a specified tidal volume.
If the patient tries to breath spontaneously, the machine does NOT assist the breaths.

It is often combined with pressure support to augment support during spontaneous breaths.

57
Q

What is the purpose of pressure support ventilation?

Who is this type of ventilation indicated for?

A

It allows the patient to determine the inflation volume and respiratory cycle.
It is just used to augment spontaneous breathing

When the patient takes a breath, the negative pressure opens a valve that delivers inspired gas at a set pressure.

It is used for spontaneously breathing patients

58
Q

What is pressure controlled ventilation?

A

A target pressure is set by the clinician.

RR, inspiratory pressure, duration of inspiration, duration of expiration, are all determined by the clinician.

59
Q

When you set the RR on the ventilator, what should it be?

A

It is determined by the needs of the patient and can be anywhere from 6 to 30BPM but usually it is 12-20

60
Q

For which ventilators do you set a tidal volume?
What should the tidal volume be usually?
What should it be for a patient with ARDS?

A

CMV, AC, SIMV
Usual tidal volume : 8-10mL/kg
ARDS: 6ml/kg to protect the lung from too high pressure during inspiration

61
Q

What is volutrauma, barotrauma, and atelectotrauma?

A

Volutrauma- too ghigh tidal volume can distend the alveoli damaging them

Barotrauma- pressure caused injury

Atelectotrauma- overdistended alveoli have increased permeability and proinflammatory cytokines are released

62
Q

When setting FIO2 for mechanical ventilation, what do you usually begin with?

A

100% O2 but decrease to minimal needed to maintain adequate saturation.

63
Q

When selecting FIO2, 100% O2 should be avoided in which patients?

A

Those with drug induced respiratory diseases like amiodarone and bleomycin

64
Q

What is the purpose of setting PEEP?

A

It prevents atelectasis by not allowing pressure to get so low that the alveoli collapse during expiration.

65
Q

What are major complications of mechanical ventilation?

A
  1. tracheal tube can cause vocal cord injury
  2. ventilator associated pneumonia
  3. barotrauma, atelectrauma, volutrauma leading to pneumothorax and hypotension
  4. Tension pneumothorax which can cause decreased venous return and decreased CO
  5. discomfort to the patient
66
Q

What is NIPPV?

What are the 2 most common forms?

A

non-invasive positive pressure ventilation where a tight fitting mask is used instead of a tracheal
tube

  1. CPAP- continuous positive airway pressure
  2. BIPAP- inspiratory positive airway pressure and expiratory positive airway pressure
67
Q

When is CPAP used?
How does it work?
What 2 patients are most likely to use CPAP?

A

It is used when the patient is breathing spontaneously.
It has a set pressure delivered in inspiration and expiration. No support is given, but it splints open the airways.

  1. obstructive sleep apnea
  2. cardiogenic pulmonary edema- reduces preload volume and edema
68
Q

When is BIPAP used?

How does it work?

A

It provides an inspiratory positive airway pressure and a different expiratory positive airway pressure
The gradient between the two augments alveolar ventilation

Used in acute settings for patients with:
1. COPD where CO2 elimination is needed

69
Q

What is ECMO?

Who receives it?

A

It is extracorporeal membranous oxygenation- it is used by patients with ARDS (hypoxemic respiratory failure).

The patient is not getting oxygenated blood despite mechanical ventilation.

It removes blood from the patient, circulates it through an artificial lung and then pumps it back into the patient.

Respiratory/Musculoskeletal (36 decks)

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