Alternative Modes Of Ventilation - 27

Question 0

How do you prevent alveolar collapse?

Answer 0

Prevent closing and open already closed = open lung concept ( high frequency oscillation)

Question 1

Two mechanisms for lung injury during atelectasis

Answer 1

1. Tv will distribute to normal areas and over distend –> volutrauma
2. Alveolar collapse only at end expiration, repetitive opening and closing –> atelectruama

Question 2

Describe high frequency oscillation ventilation

Answer 2

1. Low volume (1-2ml/kg) + high frequency
2. Oscillations create high peak airway pressure, improves gas exchange, prevent collapse, and opening collapsed alveoli
3. Recruitment with PEEP used prior to switching from conventional ventilation modes

Question 3

Describe HFOV vent settings

Answer 3

4Hz: pH 7.35

Amplitude: 70-90cmH2O

Mean Paw: 5cmH2O > Pplateau on CMV to max of 30cmH2O

Bias flow: 40L/min

Inspiration time: 33%

FiO2: 100%

Lower oscillation = higher Tv/amplitude = more effective CO2 removal

Question 4

Describe the advantages of HFOV vs. CMV

Answer 4

1. 16-24% increase in PaO2/FiO2 ratio
2. New studies ? Show impact on survival

NOT been compared to lung protective ventilation however

Question 5

Disadvantages of HFOV

Answer 5

1. Special ventilator
2. CO dec d/t high mean airway pressures
3. Aerosols zed bronchodilators are ineffective during HFOV

Question 6

Describe airway pressure release ventilation (APRV)

Answer 6

Prolonged periods of spontaneous breathing at high end-expiratory pressures (30cmH2O vs 5cmH2O of CPAP). These are then interrupted by brief periods of pressure release to atmospheric air (0cmH2O).

Variant of CPAP

High CPAP level in ARPV improves arterial oxygenation and prevents further collapse of alveolar collapse.

The pressure release phase is designed to facilitate CO2 removal

Question 7

Describe APRV vent settings

Answer 7

Pressure:
High: same as Pplateau on CMV just prior to switching to APRV, to max 30cmH2O
Low: atmospheric (0) - never actually reaches 0 d/t brevity and this actually helps prevent alveolar collapse

Time:
High pressure: 4-6sec
Low pressure: 0.6-0.8sec

FiO2: 100%

Question 8

Advantages of APRV

Answer 8

1. Recruitment of nearly all collapsed alveoli (by maintaining high airway pressures for long time periods) –> Improves oxygenation, reduces lung compliance

Question 9

Disadvantages of APRV

Answer 9

1. Severe asthma and COPD relative contraindications b/c of inability to empty lungs rapidly during the pressure release
2. CO dec b/c of high mean airway pressures but less than in HFOV

Question 10

Describe CPAP

Answer 10

Spontaneous breathing at positive end-expiration pressure (maintained by expiration valve)

Effect = increases FRC

Question 12

Limitations of CPAP

Answer 12

1. Does NOT augment Tv = limited use in AFR

2. Use in ARF is for cardiogenic pulmonary edema (which may be d/t hemodynamic support)

Question 13

Describe BiPAP

Answer 13

1. Variant of APRV
   - APRV most of the time is spent in high pressure
   - BiPAP most of the time is spent in LOW pressure
2. High pressure = Inspiratory positive airway pressure (IPAP)
3. Low pressure = Expiratory positive airway pressure (EPAP)
4. BiPAP –> higher mean airway pressure than CPAP
   - promotes alveolar recruitment
   - INC lung compliance –> indirect inc in Tv

Question 14

Describe BiPAP vent setting

Answer 14

IPAP: 10 cmH2O
EPAP: 5 cmH2O
Insp time: 3 sec
Peak Pressure = IPAP + EPAP
Peak Pressures >20 cmH2O not advised

Question 15

Describe pressure support ventilation (PSV)

Answer 15

1. Patient triggered inspirations
2. Pressure-augmented Tv
   - Terminated when insp flow rate dec to 25% of peak
3. Insp flow rate pattern = decelerating
4. Combined with CPAP to INC FRC

Question 16

Describe PSV vent settings

Answer 16

Start w/ inflation pressure 10 cmH2O + CPAP 5 cmH2O = Peak of 15 cmH2O

Question 17

Checklist for Noninvasive Ventilation

Answer 17

1. YES - Resp distress (tachypnea, accessory use, and paradox)
2. YES - PaO2/FiO2 45mmHg
3. NO - Immediate threat to life?
4. NO - Life-threatening circulatory disorder (shock)
5. NO - Coma, severe agitation, seizures, uncooperative
6. NO - Can’t protect airway
7. NO - Hematemesis, vomiting, sputum production
8. NO - Obstruction, laryngeal edema, facial trauma, recent head/neck surgery

Question 18

Describe the use of NIV in acute COPD exacerbation

Answer 18

1. Dec rates of intubation
2. Dec rates of mortality
3. 1st line therapy in COPD w/ hypercapnia
4. PSV + CPAP

Question 19

Describe the use of NIV in Obesity Hypoventilation Syndrome

Answer 19

1. Red severity of hypercapnia as output

2. Either BiPAP or CPAP

Question 20

Describe the use of NIV in asthma

Answer 20

1. Little evidence - may hasten resolution and dec length of stay

Question 21

Rank the failure rates of NIV in:

1. ARDS
2. Community acquired PNA
3. Pulmonary contusion
4. Cardiogenic pulmonary edema

Answer 21

Highest failure rate –> Lowest

ARDS (51%) –> CAP (50%) –> PC (18%) –> CPE (10%)

Question 22

Describe the use of NIV in noncardiogenic pulmonary edema

Answer 22

1. Red need for intubation & mortality
2. CPAP 10 cmH2O
3. Improved cardiac output in pts w/ systolic failure = red after load with positive intrathoracic pressure

Question 23

Describe the use of NIV in ARDS

Answer 23

1. Limited success
2. Greater success when cause is extra pulmonary (sepsis)
3. Greater success w/ PSV + CPAP

Question 24

How do you monitor the response of a pt to NIV

Answer 24

1st hour
- PaCO2 dec
or
- PaO2/FiO2 inc from 100-200

Question 25

Describe the adverse events when using NIV

Answer 25

Gastric Insufflation

• < 30 cmH2O = will not cause insufflation
• can withhold NG tube if they don’t develop insufflation

Nosocomial PNA

• Retards mucociliary clearance
• 8-10% vs. 19-22% when intubated