8. Neonatal Ventilation

Question 1

What are the indications of neonatal ventilation? (Hint: 6 things)

Answer 1

1. Resp failure: despite O2 and NIV
2. Vent failure: PaCO2 > 55/60 mmHg, pH < 7.25/7.20
3. Impaired pulmonary function: ↓ compliance & ↑ resistance, RDS, MAS, pneumonia, pneumo
4. Neuro Compromise: Apnea of Prematurity, drug depression
5. Impaired CV Function: PPHN, congenital heart disease, shock
6. Post-Op: Sedation depressing resp drive

Question 2

What are the harmful effects that can occur from neonatal ventilation? (Hint: 8 categories)

Answer 2

1. Barotrauma: from PPV, Air Leaks (Pneumo, pneumomediastinum, PIE)
2. Volutrauma: Overdistention/underdistention
3. Patient/Vent Dys-synchrony (can lead to baro & volutrauma)
4. Atelectrauma: Repetitive opening and closing of atelectatic lung units
5. Biotrauma: Effect of oxidant stress and inflammation
6. Hemodynamics: ↓ venous return, ↓ CO, ↓ pulm perfusion
7. Neurologic: Intracranial hemorrhage, changes in cerebral blood flow
8. Oxygenation: Oxygen toxicity, ROP

Question 3

1. What can ventilator induced lung injury (VILI) lead to?
2. What are the characteristics of an injured alveoli during the acute phase? (think of the sick alveoli picture greg always uses!)

Answer 3

1. BPD
2. Necrotic type 1 cells, inactivated surfactant, hyaline membrane, widened and edematous interstitium, swollen and injured epithelial cells

Question 4

1. What pressure(s) did Hernandez use on his rabbits when he ventilated them?
2. What did Hernandez discover?

Answer 4

1. PIP of 30 and 45 cmH2O
2. Using a plaster cast that wrapped around the lungs and thorax protected the rabbit from having lung damage at even 45 cmH2O pressure, whereas the rabbits with no cast had damage to the lungs.

• This shows that too much volume can cause trauma to the lungs as well.

Question 5

With respect to volutrauma, what would happen if:

1. high Vt, low PEEP
2. normal Vt, high PEEP
3. Normal Vt, low PEEP

Answer 5

1. Lungs atelectatic, overdistention on insp of alv
2. Overdistention
3. Atelectatic

Question 6

How is flow preferably measured in pediatrics and why?

Answer 6

Proximal airway flow sensors (external flow sensors), because they are faster, more accurate, and sensitive
(peds needs very sensitive flow sensors because they get very small tidal volumes)

Question 7

1. What is compressible volume?
2. If the vent measures Vt internally, what do you have to be aware of?
3. What do newer vents calculate during a pre-use check, and what does this do? What about older vents?
4. What is the difference in how compressible volume is calculated b/w the Servo I & the VN500/Avea?

Answer 7

1. Volume lost to expansion of the vent circuit and humidifier
2. If the reading is compensated for compressible volume or not
3. Tubing compliance, this automatically compensates for expansion of the circuit during pressurization
   - Older vents can’t compensate
4. Servo I can turn on/off compensation for compressible volume, VN500/Avea calculates compressible volume & measures Vt at pt Y flow sensor

Question 8

1. What is a normal RR (frequency) to set on a neonatal ventilator?
2. If the baby has spontaneous drive in respiratory distress, how high can the RR be?

Answer 8

1. 30-50 bpm

2. > 60-70 bpm

Question 9

1. What is a normal Vt target in neonates?

2. What patients may this be elevated in? (Give disease example too)

Answer 9

1. 4-6 mL/kg

2. Pts with ↑ anatomical deadspace (ex. BPD, sometimes ventilate 6-8 mL/kg)

Question 10

1. How is PIP set on neonatal ventilators?
2. What is the normal PIP range for infants?
3. What is this limited to in premature infants?
4. What is this limited to in term and older infants?

Answer 10

1. To achieve desired Vt and chest rise
2. 15-22 cmH2O
3. < 25 cmH2O
4. < 30 cmH2O

Question 11

1. How is Ti set in neonatal ventilation?
2. What happens if the Ti is long?
3. What happens if the Ti is short?
4. What is the rule of thumb to figure out Ti based on ETT size?

Answer 11

1. Based on disease pathology and time constants
2. Improves oxygenation, negative feedback inhibiting spont. respirations
3. Prevents effective Vt delivery, excessive PIP needed to deliver Vt
4. Size of ETT/10

Question 12

1. What is the normal PEEP range for neonates, and where do you generally start?
2. Since PEEP improves oxygenation, what else improves?
3. What do you adjust PEEP based on?
4. What do you need to be aware of when changing PEEP? (also…. when setting PIP what happens when you ↑ PEEP, and what happens if you’re setting ΔP?)

Answer 12

1. 5-10 cmH2O, start at 5-7 cmH2O
2. FRC!
3. Pts oxygenation, CXR
4. Vt changes! When setting PIP, increasing PEEP will cut into ΔP, and since PIP stays the same, it therefore ↓Vt. When setting ΔP, increasing PEEP will cause a jump in PIP equal to jump in PEEP, so no change in Vt.

Question 13

1. What is the expected SpO2 in a premature neonate (< 37 wks)?
2. What is the expected SpO2 in a term neonate ( 37 wks - 1 month)?

Answer 13

1. 90-94%

2. >/= 92%

Question 14

1. What does too high of a MAP cause?
2. What dies too low of a MAP cause?
3. What are characteristics of the “most appropriate map”?

Answer 14

1. Barotrauma, overdistention
2. Atelectasis, atelectrauma
3. Enhances oxygenation and minimizes risks of barotrauma and volutrauma

Question 15

What parameters can you change (↑) on the vent to ↑ MAP?

Answer 15

Flow/rise, PIP, Ti, PEEP, RR

Question 16

1. What mechanical variables determine Vt during PCV?

2. What patient variables determine Vt during PCV?

Answer 16

1. ΔP, set Ti, compressible volume, C & R of circuit/ETT

2. C & R, insp. effort, spont. insp time.

Question 17

1. What do you set in PCV?
2. What is variable?
3. What waveform is ideal in PCV and why?

Answer 17

1. Ti, PIP or ΔP, RR, PSV (if in support mode), FiO2
2. Flow
3. Decelerating waveform, almost an immediate rise to PIP, allows gas to be distributed more evenly to areas of lung w/ different time constants

Question 18

1. What is the Vt target in PSV?

2. What are PS levels usually set to in PSV? What does this support help with?

Answer 18

1. 4-6 mL/kg

2. 5-15 cmH2O, this overcomes R of ETT, and minimize WOB

Question 19

1. Why can we use lower pressures with spont. breaths in PSV and achieve similar Vt compared to PCV breaths?
2. How does PSV cycle to exhalation? (Hint: 2 options, explain how both cycle)

Answer 19

1. The effort of the patient helps with increasing Vt, allowing for ventilation at lower pressures
2. Flow: Insp. stops when flow deteriorates to preset level (usually 15-25%)
   Time: Back-up, can usually be set or may be ventilator preset, used so pt doesn’t accidentally have prolonged inspiration

Question 20

1. What is the most common mode of ventilation in Neo/Peds?
2. Which vents call this mode Volume Guarantee, and which use PRVC?
3. What types of vents does this work best in?

Answer 20

1. Volume targeted ventilation
2. VG: Drager VN 500, Avea (neo mode only)
   PRVC: Servo I, Servo U/N
3. Vents that have leak compensation features

Question 21

Volume Guarantee

1. Set tidal volume target and the ______ will adjust __ or __ to meet target
2. Pressure is regulated based on ____
3. Important to know which __ measurement
4. MUST set _____ appropriately

Answer 21

1. Pressure, up, down
2. Vt
3. Vt (ex. Vti, Vte, Calculated Vt)
4. UPL

Question 22

1. What are the steps taken in the VG mode? (Hint: 4 steps)

2. What special algorithm does the VG mode have, and what does it do differently?

Answer 22

1. a. Set target Vt
   b. Vent delivers test breath
   c. Vent measures calculated Vt (Drager)
   d. Vent adjusts PIP to achieve desired Vt
2. Separate PIP control algorithm for triggered and non triggered breaths

Question 23

Why volume guarantee? List the reasons it is beneficial (Hint: 7 things)

Answer 23

1. Maintains more stable Vt and minimizes volutrauma
2. Can assist w/ lung recruitment and avoid atelectrauma
3. More stable SpO2
4. Less hypo/hypercapnia and its effects on the brain
5. Fewer blood gases drawn by clinician
6. Maintains constant Vt (surfactant admin, lung volume recruitment, clearance of lung fluid/secretions)
7. Automatic lowering of pressure, weans in “real time”

Question 24

1. What is the max leak percentage that the VN500 can compensate?
2. The benefits of VG cannot be realized without _____________

Answer 24

1. ETT leak up to 50%

2. Open lung ventilation

Question 25

With VG mode, what happens to the pressure waveform when the baby cries, and what happens to the Vt?

Answer 25

Pressures decrease, Vt increases

Question 26

1. With VG mode, what happens to the pressure, flow, and volume waveforms when the baby has a clamping spell? 2. What disorder are clamping spells common in?

Answer 26

1. No flow, no volume, and increasing pressure to try and get Vt in 2. BPD

Question 27

With respect to surfactant admin. in VG... 1. What does surfactant admin. briefly cause in the ETT? 2. How does VG overcome this? 3. Once surfactant disperses, what happens with PIP and Vt?

Answer 27

1. Transient ETT obstruction 2. By ↑ PIP 3. The PIP will be weaned to maintain target Vt

Question 28

1. What patient populations have large instrument d/s, and what can we increase to overcome this and to what value? 2, What patient popul

Answer 28

1. Extremely small patients, start with Vt slightly larger (5.5 mL/kg) 2. Patients with severe BPD, Vt may have to be increased as high as 6, 7, or 8 mL/kg

Question 29

Trigger Mechanisms 1. Time: Vent delivers breath with ________. 2. Flow: Normal flow trigger for neonates _____, best for patients with no/minimal _____. 3. Pressure: Pt's ________ is detected by ventilator, benefit of this is has a small _____.

Answer 29

1. No pt initiation 2. 0.2 LPM, leak 3. Neg. insp. effort, lag time

Question 30

How does a leak around an uncuffed ETT tube effect ventilation? (hint: 2 things)

Answer 30

Auto cycling, low Vt

Question 31

What is automatic leak compensation? How does it work?

Answer 31

- Trigger threshold and termination criteria are automatically adapted to leak flow, this applies to all synchronized vent modes - Looks at diff in Vti & Vte, adjusts trigger/termination to be slightly below leak to reduce auto cycling