Chapter 17: Effects Of Positive-Pressure

Front 1

Define volutrauma, biotrauma & atelectrauma.

Back 1

. Volutrauma is lung injury caused by excessive volume in the lungs. Biotrauma is caused by the release of inflammatory mediators that cause problems in other organs of the body. Atelectrauma is the term used for shear stress injury and loss of surfactant in the lungs.

Front 2

Briefly describe the difference between ventilator-induced lung injury (VILI) and ventilator-associated lung injury (VALI).

Back 2

. Ventilator-induced lung injury (VILI) is a form of lung injury that occurs at the alveolar level and resembles ARDS. Ventilator-associated lung injury (VALI) includes injury caused by extra-alveolar gas, patient-ventilator dyssynchrony, air trapping, and ventilator-associated pneumonia

Front 3

List five conditions that predipose a patient to barotruama while he/she is being mechanically ventilated.

Back 3

(any of the following) High peak airway pressures with low end-expiratory pressures, presence of bullae, high levels of PEEP with high tidal volumes, aspiration of gastric acid, necrotizing pneumonias, ALI/ARDS

Front 4

During patient ventilator system checks the RT notes that one side of the pt's neck & face appear puffy. These areas feel crepitant to the touch. What is the most likely cause of this problem?

Back 4

Subcutaneous emphysema

Front 5

Rapid onset of increased peak airway pressuers & decreasing lung compliance may be caused by____.

Back 5

a pneumothorax

Front 6

What is the treatment for a tension pneumothorax?

Back 6

. Treatment for a pneumothorax involves placing a 14-gauge needle (or smaller) into the anterior second to third intercostal space on the affected side in the midclavicular line over the top of the rib with the patient in the upright position.

Front 7

A mechanically ventilated patient has developed a tension pneumothorax. How should the pt be ventilated until the appropriate txt can begin?

Back 7

. The patient should be manually ventilated with a resuscitation bag using 100% supplemental oxygen; an in-line manometer should be used to monitor pressure so that it can be kept as low as possible.

Front 8

List four clinical signs of a tension pneumothorax.

Back 8

. (a) Absent breath sounds on the affected side; (b) mediastinal, and possibly tracheal, deviation away from the affected side; (c) tympanic percussion note over the affected side; and (d) neck vein distention.

Front 9

How would a CXR of a pt with a tension pneumothorax look?

Back 9

. The chest radiograph would show one diaphragm more depressed than the other and possibly a deep sulcus sign with air appearing adjacent to the depressed diaphragm.

Front 10

air dissecting into the retroperitoneal space is known as ....

Back 10

pneumoperitoneum

Front 11

What is the minimum transpulmonary pressure that has been associated with lung injury in animals?

Back 11

30 to 35 cm H2O

Front 12

List 3 examples of situations where lung injury may occur from abnormally high transpulmonary pressure.

Back 12

. (a) The lungs are very stiff and the pleural pressure is near normal; (b) the lungs are normal, but there is a right mainstem intubation with a large tidal volume; and (c) both lungs are overdistended inside a normal chest wall.

Front 13

Describe how volutrauma occurs.

Back 13

. Volutrauma, or damage from overdistention, occurs because of regional differences in lung compliance. The more compliant lung areas fill more easily and expand to accommodate large volumes, whereas noncompliant areas do not. The overdistention causes acute alveolar injury and the formation of pulmonary edema both by increased permeability and by filtration mechanisms

Front 14

In the clinical setting, how can chest wall movement be minimixed to decrease the risk of lung injury from volutrauma?

Back 14

. Placing the patient in the prone position restricts chest wall movement and minimizes lung injury from overdistention.

Front 15

What clinical situation puts a ventilated pt at risk of atelectrauma?

Back 15

Managing a patient with ALI/ARDS using low tidal volumes and inadequate levels of PEEP.

Front 16

Name the 2 chemical mediators that are released when the alveolar epithelial cells are overstretched.

Back 16

(1) Shear stress, (2) surfactant alteration and washout, and (3) microvascular injury.
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Front 17

Describe how multiple organ dysfunction syndrome develops from overdistension of alveoli.

Back 17

Overdistention causes the release of chemical mediators, which can leak into the blood vessels. The circulation then carries these substances to other areas of the body and causes inflammatory reactions in other organs, such as the kidneys, gut, and liver.

Front 18

How can multiple organ dysfunction syndrome be avoided during mechanical ventilation?

Back 18

Multiple organ dysfunction syndrome can be avoided during mechanical ventilation by using lung-protective strategies, such as low tidal volumes and therapeutic PEEP.

Front 19

In what areas of the lung are ventilation & perfusion best matched during spont ventilation in the supine position?

Back 19

. Ventilation and perfusion are best matched in the dependent lung areas near the back

Front 20

How are ventilation & perfusion altered during PPV of a pt who is sedated & paralyzed?

Back 20

. The diaphragm is most displaced in the nondependent regions of the lung; therefore, gas flows easily to this area, whereas blood flow to this area is decreased. Alveolar collapse is most likely to occur in the dependent areas of the lung, where perfusion is greatest.

Front 21

How can the changes in gas distribution during mechanical ventilation be minimized?

Back 21

. The preservation of spontaneous breathing can reduce the ventilation/perfusion changes associated with mechanical ventilation. Therefore, ventilator modes that preserve spontaneous breathing may be beneficial (e.g., pressure support ventilation [PSV]).

Front 22

How can PPV increase dead space?

Back 22

Positive pressure ventilation increases the size of the conductive airways, which in turn increases the amount of dead space ventilation. Additionally, if normal alveoli are overexpanded during PPV and compression of pulmonary vessels results, alveolar dead space also increases.

Front 23

Why would the use of high volumes during PPV & PEEP cause an increase in pulmonary shunting?

Back 23

The increased volume during a positive pressure breath and PEEP squeezes the blood out of nondependent zones, sending more blood into dependent areas, where ventilation is now lower, or into disease-affected areas of the lung, where lung volumes are not substantially increased. This can lead to increased shunting and decreased PaO2.

Front 24

How does mechanical ventilation cause increased pulmonary vascular resistance?

Back 24

Increased airway and alveolar pressures can lead to thinning and compression of pulmonary capillaries, decreased perfusion, and increased pulmonary vascular resistance (PVR)

Front 25

Explain how hopoventilaiton can lead to cardiac dysrhythmias.

Back 25

Hypoventilation causes an increase in plasma hydrogen ion levels, which can contribute to high plasma potassium levels (hyperkalemia). Hyperkalemia can affect cardiac function and can lead to cardiac dysrhythmias.

Front 26

What type of pt may benefit from permissive hypercapnia?

Back 26

. Permissive hypercapnia may be appropriate in patients with ARDS, because maintaining a normal CO2 range without causing VILI is difficult in these patients.

Front 27

List four patient-induced hyperventilations...

Back 27

(a) Hypoxemia, (b) pain and anxiety syndromes, (c) circulatory failure, and (d) airway inflammation.

Front 28

The cause of a right shiftin the O2 dissociation curve is ___.

Back 28

. Respiratory acidosis (hypoventilation, hypercapnia)

Front 29

Prolonged ventilatior-induced hyperventilation can lead to what types of patient problems?

Back 29

Respiratory alkalosis can cause hypokalemia (low potassium levels), which can lead to cardiac arrhythmias; other problems include tetany and reduced cerebral perfusion, which may contribute to increased cerebral hypoxia. Respiratory alkalosis also reduces the patient’s drive to breathe, making weaning difficult.

Front 30

What happens to the cerebrospinal fluid during prolonged hyperventilation with mechanical ventilation?

Back 30

Hyperventilation causes respiratory alkalosis, which leads to the diffusion of CO2 out of the cerebral spinal fluid (CSF) because of the low blood CO2 levels. Accordingly, the H+ concentration in the CSF decreases, and respirations are not stimulated.

Front 31

When is the admin of intravenous bicarbonate indicated?

Back 31

. Intravenous administration of bicarbonate is indicated for life-threatening hyperkalemia either caused by or associated with metabolic acidosis.

Front 32

why could admin of IV bicarbonate to a spontaneously breathing patient with a metabolic acidosis cause a problem?

Back 32

. If a spontaneously breathing patient cannot increase ventilation, the additional bicarbonate combines with plasma hydrogen ions and increases CO2 production. If the CO2 is retained, the acidosis may worsen.

Front 33

List causes of metabolic alkalosis in the clinical setting (4).

Back 33

. Metabolic alkalosis can be caused by (1) gastrointestinal suctioning or vomiting, (2) diuretic administration, (3) bicarbonate administration, (4) administration of lactate, acetate, or citrate.

Front 34

What causes auto-PEEP without dynamic hyperinflation?

Back 34

. Auto PEEP can occur without dynamic hyperinflation when the expiratory muscles are actively contracting during exhalation. This raises alveolar pressures at end-exhalation without increasing the volume at end-exhalation (auto PEEP without lung distention).

Front 35

Ventilator-induced auto-PEEP can be created by:

Back 35

. High minute ventilation (high respiratory rates, increased tidal volume), short expiratory times, mechanical devices that increase expiratory resistance, and low inspiratory flow rates.

Front 36

What pt factors increase the risk of auto-PEEP?

Back 36

Chronic obstructive airway disease, age above 60 years, increased airway resistance (e.g., small ET tube size, bronchospasm, increased secretions, mucosal edema), increased lung compliance.

Front 37

What technique is used to detect the presence of auto-PEEP?

Back 37

. End-expiratory pause

Front 38

What pt & ventilator condition must be present in order to detect auto-PEEP?

Back 38

. Detection of auto PEEP by measuring the end-expiratory pressure requires a quiet, relaxed patient on controlled ventilation.

Front 39

How many time constants are necessary for the lungs to empty 98% of the inspired volume?

Back 39

3 to 4 time constants

Front 40

Define dynamic hyperinflation.

Back 40

Dynamic hyperinflation is the failure of lung volume to return to passive FRC during exhalation by the time the next inspiration begins.

Front 41

what effects does the presence of auto-PEEP have on ventilator function?

Back 41

. Auto PEEP slows the beginning of gas flow during inspiration, because flow delivery does not start until mouth pressure exceeds alveolar pressure, which is now higher than the ambient pressure at the end of exhalation. Auto PEEP also makes it more difficult for spontaneously breathing patients to trigger a ventilator breath, even when sensitivity settings are appropriate.

Front 42

Calculate static compliance for the following situation:
Vt 525ml, PIP 43, Pplat 30, set PEEP 12, auto PEEP 5

Back 42

. CSTAT = VT÷[Pplat – (PEEP + auto PEEP)]
= 525mL÷[30cmH2O – (12cmH2O + 5cmH2O)]
=525÷[30–17]
= 525÷13=40.4 mL/cm H2O

Front 43

List 4 strategies that can be used to decrease auto-PEEP when the patient is receiving full ventilatory support:

Back 43

(a) Shorten inspiratory time and allow for a longer expiratory time by increasing the inspiratory flow rate; (b) use smaller tidal volumes and low respiratory rates to increase the expiratory time; (c) use low-resistance exhalation valves; (d) use large endotracheal tubes to reduce air trapping.

Front 44

List 4 modes of ventilation that may be used to decrease auto-PEEP in a pt who is intubated & has spont breathing efforts:

Back 44

. (a) SIMV, (b) pressure support, (c) CPAP, and (d) APRV.

Front 45

When does pulmonary O2 toxicity become a problem in adults & premature infants?

Back 45

. Oxygen becomes a potential hazard when concentrations greater than 60% are administered for longer than 48 hours in an adult and if the FIO2 provides a PaO2 greater than 80 mm Hg in a newborn or premature infant.

Front 46

If an FIO2 greater than __ is required, PEEP should be used. List 4 ways to assess pulmonary changes associated with O2 toxicity.

Back 46

. 0.6. (a) Vital capacity will decrease; (b) compliance will decrease; (c) diffusing capacity will decrease; and (d) alveolar to arterial PO2 difference

Front 47

What are the lower limit tagets for oxygenation for patients recieving mechanical ventilation?

Back 47

. A target PaO2 of 60 mm Hg and an SpO2 of 90% are acceptable lower limits.

Front 48

The use of low tidal volumes with O2 concentrations >70% leads to__.

Back 48

. absorption atelectasis

Front 49

The normal inspiratory WOB is how much?

Back 49

Normal inspiratory WOB is about 0.5 joules/L, or 0.05 kg-m/L.

Front 50

Inspiratory WOB is condidered high when it is greater than ___.

Back 50

. 1.5 joule/L (or 15 joule/L/min)

Front 51

a pt who has an increased WOBwill most likely be experiencing what signs?

Back 51

. A high spontaneous respiratory rate and use of accessory muscles.
54

Front 52

List 4 basic strategeis for keeping the pt's WOB minimized.

Back 52

(a) Use the largest possible endotracheal tube; (b) ensure the machine sensitivity is set appropriately; (c) ensure that there is no asynchrony; (d) reduce the patient’s airway resistance.

Front 53

List 4 signs of pt-vent asynchrony.

Back 53

(a) Use of accessory muscles, (b) tachypnea, (c) retractions, and (d) chest-abdominal paradox.

Front 54

Define trigger asynchroy & describe a method to avoid it.

Back 54

. Trigger asynchrony occurs when the ventilator sensitivity setting is not appropriate for the patient. This problem may be alleviated by adjusting the trigger setting appropriately or by switching to flow triggering, which in older ventilators has a faster response time.

Front 55

How does auto-PEEP cause trigger asynchrony?

Back 55

. The presence of auto PEEP can also make triggering the ventilator more difficult for the patient and result in missed patient triggers. With auto PEEP, the patient’s effort may not be transmitted to the sensing mechanism; consequently the ventilator would not provide inspiratory gas flow. Because auto PEEP is a dynamic condition, it can be present in one breath and absent the next. In fact, in patients normally not suspected of having auto PEEP, it is probably one of the major contributors to trigger asynchrony, resulting in patient discomfort and an increase in the oxygen cost of breathing.

Front 56

What should the initial flow be set at when using volume ventilation with a constant flow?

Back 56

. 80 L/min

Front 57

What type of breaths may provide more synchrony for a pt with high flow demands & why?

Back 57

. Pressure-targeted breaths, such as with PCV and PSV, because the ventilator rapidly provides a high flow to achieve and maintain the set pressure. As long as the set pressure is adequate, the flow to the patient will be adequate.

Front 58

What adjustment can be made during pressure targeted ventilation to lessen the rapid rise of flow when a breath begins?

Back 58

Adjust rise time or slope.

Front 59

What is cycle asynchrony & under what conditions can it occur?

Back 59

Cycle dyssynchrony occurs when the patient begins to exhale before the completion of a ventilator breath (inspiration). This may occur when the inspiratory time is set too long by a control itself, or as a result of a combination of rate, flow, and volume settings.

Front 60

What strategies may be used to eliminate cycle assynchrony during mech ventilation with full support & spont ventilation?

Back 60

. During full ventilatory support, either the flow rate can be increased to shorten TI or the set TI may be reduced. During spontaneous breaths, the flow cycle percentage can be changed.

Front 61

What mode of ventilation delivers varing breath types which may result in mode asynchrony?

Back 61

VC-SIMV

Front 62

when does PEEP asynchrony occur?

Back 62

PEEP asynchrony occurs either when PEEP is set too low and atelectasis forms, or when it is too high and overdistention occurs.

Front 63

How does closed-loop ventilation cause asynchrony?

Back 63

. A ventilator does not detect all of the patient’s spontaneous efforts because of missed triggers. In a minute ventilation−based unit, the ventilator detects a decrease in rate and automatically increases the volume delivery up to 150%. Also, the ventilator may not detect all of a patient’s spontaneous efforts if a patient is on VS or PRVC and the patient’s inspiratory demand increases because of a decrease in compliance or oxygenation. The ventilator detects the high volume and interprets it as an improvement in compliance or resistance and reduces pressure.

Front 64

List at least 5 potential mechanical failures that can occur during mechanical ventilation.

Back 64

. (any of the following) Disconnection from the power source; failure of the power source; failure of the ventilator to function because of equipment manufacturing problems or improper maintenance; failure of alarms to work because of mechanical failure or failure of personnel to turn them on or use them properly; failure of heating or humidifying devices; failure of the pressure relief valve to open; disconnection of the patient Y-connector; leaks in the system, resulting in inadequate pressure or tidal volume delivery; failure of the expiratory valve to function, causing a large system leak or a closed system with no exit for exhaled air; ( inappropriate assembly of the patient circuit.

Front 65

What 7 complications can occur during mechanical ventilation?

Back 65

. (any of the following) Alveolar hypoventilation, alveolar hyperventilation, massive gastric distention, atelectasis, pneumonia, hypotension, pneumothorax, pneumoperitoneum, subcutaneous air.

Front 66

What hazards are associated with the use of both HME's & heated humidifies?

Back 66

Hypothermia, hypoventilation, and alveolar gas trapping caused by mucus plugging of airways, possible increased resistive WOB caused by mucus plugging of airways, possible increased resistive WOB through the humidifier.

Front 67

What are tha hazards associated with the use of HME's?

Back 67

. Possible hypoventilation caused by increased dead space, underhydration, and impaction of mucous secretions; also, ineffective low pressure alarm during disconnection because of resistance through HME

Front 68

The major hazard(s) of oxygen therapy in association with mechanical ventilation include which of the following? (tachycardia, absorption atelectasis, O2 induced bradypnea, pulmonary O2 toxicity)

Back 68

absorption atelectasis & pulmonary O2 toxicity

Front 69

Auto-Peet should be suspected during which of the following observations: (prolonged resp pause, the pt coughs severely when suctioned, expiration is continuous up to the next inspiration, the SIMV manditory rate is set at 10 breaths/min)

Back 69

expiration is continuous up to the next inspiration

Front 70

The lung capacity that increases when auto-PEEP is present is which of the following?

Back 70

FRC

Front 71

Iatrogenic hyperventilation of a patient with a diagnosis of COPD may lead to which of the following consequences?
1. Tetany
2. Air trapping
3. Cerebral edma
4. Hypokalemia

Back 71

Tetany, Air Trapping and Hypokalemia

Front 72

A patient who has been mechanically ventilated for 7 days has recently developed subcutaneous emphysema. Further assessment reveals cyanosis, signs of dyspnea, and a markedly elevated PIP. This patient is most likely expirencing which of the following?

Back 72

Pneumothroax

Front 73

The risk of vollutrauma is increased for mechanically ventilated patients who exhibit which of the following?

Back 73

Increased Pta

Front 74

The amount of bicarbonate replacement given to a patient with severe metabolic acidosis who weighs 145 lb and has a base deficit of 10 should be which of the following?

Back 74

110mEq

Front 75

Failure to recognise a patient's trigger efforts is known as which of the following?

Back 75

trigger asynchrony

Front 76

An increase in a patient's assist rate followed by a rise in PIP and drop in exhaled tidal volume is most often associated with which of the following?

Back 76

Auto-PEEP

Front 77

10. The presence of fine, late inspiratory crackles may lead to which of the following lung injuries?
1. Biotrauma
2. Shear stress
3 Surfactant alteration
4. Subcutaneous emphysema

Back 77

Shear stress and Surfactant alteration