Pulmonology/ Mechanical Ventilation

Question 1

What does SIMV stand for?

Answer 1

synchronized intermittent mandatory ventilation

Question 2

What does PRVC stand for?

Answer 2

pressure regulated volume control

Question 3

What is post-obstructive pneumonia and what usually causes it?

Answer 3

Post-obstructive pneumonia is the result of airway obstruction, commonly due to lung cancer. It presents as a pulmonary infiltrate distal to a bronchial obstruction. The majority of patients with lung cancer are non-operable and incurable at initial presentation.

[Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/16643772]

Question 4

What is important to understand about vitamin D levels in a patient with sarcoidosis?

Answer 4

Serum vitamin D levels may not reflect tissue-level vitamin D in sarcoidosis

Question 5

What is sarcoidosis?

What common electrolyte and vitamin imbalances are commonly associated with sarcoidosis?

Answer 5

Sarcoidosis is a chronic granulomatous disease.

It presents with hypercalciuria in 30 – 50% of patients and hypercalcemia in 10 – 20% of patients. Hypervitaminosis D is also commonly reported.

[Retrieved from “Serum vitamin D levels may not reflect tissue-level vitamin D in sarcoidosis”, by Jill Lauren Berlin, Ghanshyam Palamaner Subash Shantha, Henry Yeager, and Linda Thomas-Hemak]

Question 6

Explain the VC-AC mode of ventilation.

Answer 6

VC-AC is Volume Control - Assist Control
– volume-controlled
– timed cycled
– machine- or patient-triggered
– fixed inspiratory flow
– backup frequency

In the ventilation mode VC-AC, the patient always receives at least the set tidal volume (VT).
In VC-AC, every detected inspiration effort of the patient at PEEP level triggers an additional mandatory breath. The patient thus determines the number of additional mandatory breaths.
To give the patient sufficient time for expiration, it is not possible to trigger another mandatory breath immediately after a completed breath.
If after the completion of the expiratory time no mandatory breath has been triggered, a mandatory breath is automatically applied (backup frequency).
The control knob for respiratory rate (RR) therefore defines the minimum ventilation frequency.
Because the number of mandatory breaths depends both on the patient and the set frequency (RR), the minute volume (MV) can vary.

[Retrieved from p. 24 of https://www.draeger.com/Products/Content/9066477 _nomenklatur_booklet_gesamt_en_20140630_l1_fin.pdf]

Question 7

The principal benefits of mechanical ventilation are…

Answer 7

…improved gas exchange and decreased work of breathing.

[Retrieved from UpToDate: https://www-uptodate-com.libproxy. usouthal.edu/contents/overview-of-mechanical-ventilation?source=search_result&search=overview%20of%20mechanical %20ventilation&selectedTitle=1~150]

Question 8

A trial of NPPV is worthwhile in patients with…

…who do not require emergent intubation and do not have contraindications to NPPV.

Answer 8

…acute cardiogenic pulmonary edema or hypercapnic respiratory failure due to chronic obstructive pulmonary disease (COPD)…

[Retrieved from UpToDate: https://www-uptodate-com.libproxy. usouthal.edu/contents/overview-of-mechanical-ventilation?source=search_result&search=overview%20of%20mechanical %20ventilation&selectedTitle=1~150]

Question 9

What are some contraindications to NIPPV?

Answer 9

altered mental status
abundant secretions
nausea or emesis

[Retrieved from UpToDate: https://www-uptodate-com.libproxy. usouthal.edu/contents/overview-of-mechanical-ventilation?source=search_result&search=overview%20of%20mechanical %20ventilation&selectedTitle=1~150]

Question 10

One study identified diaphragm _______ and markers of ___________ even among patients whose ventilatory support lasted less than three days.

Answer 10

atrophy; proteolysis

[Retrieved from UpToDate: https://www-uptodate-com.libproxy. usouthal.edu/contents/overview-of-mechanical-ventilation?source=search_result&search=overview%20of%20mechanical %20ventilation&selectedTitle=1~150]

Question 11

Auto-PEEP (intrinsic positive end-expiratory pressure) interferes with pressure triggering. Auto-PEEP refers to…

Answer 11

…end-expiratory pressure that is created when inspiration begins before expiration is complete.

[Retrieved from UpToDate: https://www-uptodate-com.libproxy. usouthal.edu/contents/overview-of-mechanical-ventilation?source=search_result&search=overview%20of%20mechanical %20ventilation&selectedTitle=1~150]

Question 12

During volume-limited ventilation, the tidal volume is set by the clinician and remains constant. During pressure-limited ventilation, the tidal volume is ________; it is directly related to the ___________ ________ _____ and compliance, but indirectly related to the resistance of the ventilator tubing such that the clinician typically changes the tidal volume by adjusting the inspiratory pressure level.

Answer 12

variable
inspiratory pressure level

[Retrieved from UpToDate: https://www-uptodate-com.libproxy. usouthal.edu/contents/overview-of-mechanical-ventilation?source=search_result&search=overview%20of%20mechanical %20ventilation&selectedTitle=1~150]

Question 13

Extrinsic positive end-expiratory pressure (applied PEEP) is generally added to…

Answer 13

…mitigate end-expiratory alveolar collapse.

[Retrieved from UpToDate: https://www-uptodate-com.libproxy. usouthal.edu/contents/overview-of-mechanical-ventilation?source=search_result&search=overview%20of%20mechanical %20ventilation&selectedTitle=1~150]

Question 14

One pilot study of 103 mechanically ventilated patients reported __ __________ __ _____ ___________, intensive care unit (ICU) mortality, or 90-day mortality in patients who were ventilated using a conservative strategy (peripheral oxygen saturation [SpO2] 88 to 92 percent) compared to a liberal one (SpO2 ≥ 96 percent)

Answer 14

no difference in organ dysfunction

[Retrieved from UpToDate: https://www-uptodate-com.libproxy. usouthal.edu/contents/overview-of-mechanical-ventilation?source=search_result&search=overview%20of%20mechanical %20ventilation&selectedTitle=1~150]

Question 15

Patients whose lung units empty heterogeneously (eg, patients with obstructive airways disease) are particularly susceptible to developing _________ during positive pressure ventilation, even at relatively low minute ventilation.

Answer 15

auto-PEEP

[Retrieved from UpToDate: “Physiologic and pathophysiologic consequences of mechanical ventilation”]

Question 16

The distribution of positive pressure ventilation is never uniform because the amount of ventilation is a function of three factors that vary from region to region within the lungs:

Answer 16

1. ) alveolar compliance
2. ) airway resistance
3. ) dependency (upper versus lower lung zones)

[Retrieved from UpToDate: “Physiologic and pathophysiologic consequences of mechanical ventilation”]

Question 17

Dead space is an area that is…

Answer 17

…overventilated relative to perfusion.

[Retrieved from UpToDate: “Physiologic and pathophysiologic consequences of mechanical ventilation”]

Question 18

Areas affected by shunting are…

Answer 18

areas that are underventilated relative to perfusion.

[Retrieved from UpToDate: “Physiologic and pathophysiologic consequences of mechanical ventilation”]

Question 19

In terms of effect on dead space and shunt, by increasing ventilation (V), the institution of positive pressure ventilation will…

Answer 19

…worsen dead space but improve shunt.

[Retrieved from UpToDate: “Physiologic and pathophysiologic consequences of mechanical ventilation”]

Question 20

Mechanical ventilation itself causes diaphragmatic muscle atrophy, a phenomenon called…

Answer 20

…ventilator induced diaphragmatic dysfunction.

[Retrieved from UpToDate: “Physiologic and pathophysiologic consequences of mechanical ventilation”]

Question 21

Positive pressure ventilation appears to impair ___________ motility in the airways.

Answer 21

mucociliary

[Retrieved from UpToDate: “Physiologic and pathophysiologic consequences of mechanical ventilation”]

Question 22

How exactly does mechanical ventilation decrease venous return to the heart?

Answer 22

Intrathoracic and right atrial pressure increase during positive pressure ventilation, thereby reducing the gradient for venous return.

[Retrieved from UpToDate: “Physiologic and pathophysiologic consequences of mechanical ventilation”]

Question 23

What does alveolar inflation during positive pressure ventilation do to the pulmonary vascular bed?

Answer 23

It compresses the pulmonary vascular bed.

[Retrieved from UpToDate: “Physiologic and pathophysiologic consequences of mechanical ventilation”]

Question 24

Name a condition associated with low chest wall compliance.
high lung compliance?
high chest wall compliance?
low lung compliance?

Answer 24

fibrothorax
emphysema
sternotomy
ARDS, heart failure

[Retrieved from UpToDate: “Physiologic and pathophysiologic consequences of mechanical ventilation”]

Question 25

When a patient is receiving positive pressure ventilation, the PCWP is ____________ ________ and not reflective of the true __________ _______ ________.

Answer 25

artificially elevated; transmural filling pressure

[Retrieved from UpToDate: “Physiologic and pathophysiologic consequences of mechanical ventilation”]

Question 26

The true transmural filling pressure can be estimated by subtracting…

Answer 26

…one-half of the PEEP level from the PCWP if the lung compliance is normal, or one-quarter of the PEEP level if lung compliance is reduced.

[Retrieved from UpToDate: “Physiologic and pathophysiologic consequences of mechanical ventilation”]

Question 27

Positive airway pressure (especially PEEP) is also associated with decreased splanchnic perfusion. Decreased splanchnic perfusion manifests as…

Answer 27

…elevated plasma aminotransferase and lactate dehydrogenase levels.

[Retrieved from UpToDate: “Physiologic and pathophysiologic consequences of mechanical ventilation”]

Question 28

Positive pressure ventilation is an independent risk factor for…

Answer 28

…acute renal failure.

[Retrieved from UpToDate: “Physiologic and pathophysiologic consequences of mechanical ventilation”]

Question 29

What is the formula for the rapid shallow breathing index?

Answer 29

The ratio of respiratory frequency to tidal volume (f/VT).

A patient who has a respiratory rate of 25 breaths/min and a tidal volume of 250 mL/breath has an RSBI of (25 breaths/min)/(.25 L) = 100 breaths/min/L.

[Retrieved from UpToDate: “Weaning from mechanical ventilation: The rapid shallow breathing index”]

Question 30

The rapid shallow breathing index (RSBI) was originally described in a prospective cohort study that evaluated a population of mechanically ventilated patients. The study found that an RSBI > ___ breaths/min/L was associated with weaning failure.

Answer 30

105

[Retrieved from UpToDate: “Weaning from mechanical ventilation: The rapid shallow breathing index”]

Question 31

Forced vital capacity is defined as…

FVC is measured via __________.

Answer 31

….a measure of the total exhaled volume of air during a forceful and complete exhalation, taken after a maximal inhalation.

spirometry

[Retrieved from UpToDate, “Overview of Pulmonary Function Testing in Adults”]

Question 32

Forced expiratory volume in one second (FEV1) is defined as…

Answer 32

…a measure of the volume of air exhaled in the first second during a forceful and complete exhalation, taken after a maximal inhalation.

[Retrieved from UpToDate, “Overview of Pulmonary Function Testing in Adults”]

Question 33

Body ______________ is the gold standard for measurement of lung volumes, particularly in the setting of significant airflow obstruction.

Answer 33

plethysmography

[Retrieved from UpToDate, “Overview of Pulmonary Function Testing in Adults”]

Question 34

Because both pleural effusion and consolidation produce dullness, percuss just above the dullness, preferably using the light pat technique. The following clues each indicate that the presence of a pleural effusion is more likely:

Increased rib vibration in the anterior chest to percussion posteriorly (Kellock’s sign);

Change in the percussible dullness with change in position (D’Amato’s sign);

A rim of hyperresonance heard just above the dullness (skodaic hyperresonance);

Increased resonance of the thoracic spinous processes (Korányi’s sign);

An “_“-shaped line of dullness on percussion of the chest (known as the _________-_____ line); and

Change in the tympanitic note above a pleural effusion when the patient opens and closes his or her mouth.

Answer 34

“S”
Damoiseau-Ellis

[Retrieved from https://www.medscape.com/viewarticle/712242_6]

Question 35

Theophylline — what is it’s pharmacologic category and mechanism of action?

Answer 35

It’s a nonselective phosphodiesterase enzyme inhibitor. It has 2 distinct actions: smooth muscle relaxation (bronchodilation), and suppression of the response of the airways to stimuli.
Bronchodilatation is mediated by inhibition of 2 isoenzymes: phosphodiesterase (PDE III and to a lesser extent, PDE IV).
Theophylline increases the force of contraction of diaphragmatic muscles through enhancement of calcium uptake through adenosine-mediated channels.

[Lexicomp]

Question 36

What is a “mode” of mechanical ventilation?

Answer 36

A predetermined pattern of patient-ventilator interaction.

p. 1749; from “Taxonomy for Mechanical Ventilation” article in Respiratory Care, Nov 2014

Question 37

The first maxim of mechanical ventilation:

Answer 37

a breath is one cycle of positive flow (inspiration) and negative flow (expiration) defined in terms of the flow-time curve.

(p. 1749; from “Taxonomy for Mechanical Ventilation” article in Respiratory Care, Nov 2014)

Question 38

By convention, positive flow is designated as…

While negative flow indicates…

Answer 38

…inspiration.

…expiration.

(p. 1749; from “Taxonomy for Mechanical Ventilation” article in Respiratory Care, Nov 2014)

Question 39

Inspiratory time is defined as….

Answer 39

….the period from the start of positive flow to the start of negative flow.

(p. 1749; from “Taxonomy for Mechanical Ventilation” article in Respiratory Care, Nov 2014)

Question 40

Expiratory time is defined as….

Answer 40

…the period from the start of negative flow to the start of positive flow.

(p. 1749; from “Taxonomy for Mechanical Ventilation” article in Respiratory Care, Nov 2014)

Question 41

The tidal volume is the ________ of flow with respect to time.

Answer 41

integral

p. 1749; from “Taxonomy for Mechanical Ventilation” article in Respiratory Care, Nov 2014

Question 42

The 2nd maxim of mechanical ventilation:

A breath is assisted if the ventilator provides ____ __ ___ of the work of breathing.

Answer 42

some or all

p. 1749; from “Taxonomy for Mechanical Ventilation” article in Respiratory Care, Nov 2014

Question 43

Neurogenic pulmonary edema is defined as….

Answer 43

…an increase in pulmonary interstitial and alveolar fluid that is due to an acute central nervous system injury and usually develops rapidly after the injury.

[From UptoDate, “Neurogenic pulmonary edema”]

Question 44

How does barotrauma cause SQ air/ pneumos?

Answer 44

Alveolar rupture allows air from the alveolus to enter the pulmonary interstitium. The interstitial air can then dissect along the perivascular sheaths toward the pleural space, mediastinum, peritoneum, and/or skin.