Management of refractory hypoxemia using recruitment maneuvers and rescue therapies. Frontiers. 2023

Question 1

What are the hemodynamic effects of recruitment maneuvers and high PEEP?

Answer 1

• decreased RV and LV preload
• increased RV afterload
• increased pulmonary vascular resistance

> > decreased CO, hypotension, tachycardia

reported: arrhythmias

Question 2

What are the complications from barotrauma?

Answer 2

• pneumothorax
• subcutaneous emphysema
• pneumomediastinum

Question 3

\Which type of recruitment maneuver has less negative hemodynamic effects, sustained inflation or a stepwise approach?

Answer 3

sustained inflantion

Question 4

What minimum level of PEEP should be implemented after recruitment maneuvers to keep the recruited alveoli open?

Answer 4

10-12 mm Hg

Question 5

List contraindications for recruitment maneuver

Answer 5

• hemodynamic instability
• right sided heart failure
• intracranial hypertension
• pneumothorax
• barotrauma risk
• patients with focal lung disease

Question 6

What are the benefits of neuromuscular blockade in mechanically ventilated patients?

Answer 6

improved synchrony results in:
* improved recruitment
* improved compliance
* improved gas exchange
* reduced biotrauma

Question 7

What are the downsides of neuromuscular blockade in mechanically ventilated patients?

Answer 7

• loss of diaphragmatic tone –> atalectasis –> hypoxemia
• intensive care acquired weakness
• critical illness polyneuropathy

Question 8

What are the proposed benefits of inhaled pulmonary vasodilators?

Answer 8

• reverse pulmonary hypoxic vasoconstriction
• support right ventricular function (indirectly) –> reduce pulmonary vascular resistance

Question 9

Name 2 inhaled vasodilators

Answer 9

• nitric oxide
• prostaglandins

Question 10

What are adverse effects of inhaled nitric oxide?

Answer 10

• methemoglobinemia
• kidney failure
• inhibition of platelet activity
• hypotension

Question 11

What happens if inhaled vasodilators are stopped too abruptly?

Answer 11

severe rebound hypertension

epoprostenol: half dose every 2-4 hours considered safe

Question 12

Describe APRV

Answer 12

Phases of high continuous airway pressure with short phases of intermittent pressure release

i.e., high I:E ratio

Question 13

What are the different settings to control in APRV?

Answer 13

High-level pressure - set to the plateau pressure on conventional mode prior to APRV
High pressure time - 3-8 seconds, start at 4 sec - should be ~90% of the cycle time
Low-level pressure - set to 0 mm Hg
Low-pressure time - 0.2-0.8 seconds - set at 0.5 seconds initially

Question 14

If PLow is set to 0 in APRV, why aren’t most alveoli collapsing?

Answer 14

The short release preiod permits only partial unloading - causes auto-PEEP

Question 15

What is high frequency oscillatory ventilation

Answer 15

low tidal volume with high RR with high PEEP

Question 16

Define “refractory hypoxemia”

Answer 16

PaO2 < 60 mm< 100
on:
* FiO2 of 0.8-1.0
* PEEP of 10-30 cm H2O
* plateau pressure > 30 cm H2O

Question 17

What is the main common cause of death in patients with ARDS?

Answer 17

MODS

Question 18

What entails “protective mechanical ventilation”?

Answer 18

low tidal volues - 4-8 mL/kg
low plateau pressure - up to 30-32 cm H2O

Question 19

Define anatomic versus functional recruitment

Answer 19

anatomic recruitments is defined as the restoration of aeration as assessed by CT
functional recruitment is defined as the improvement in gas exchange

Question 20

List criteria to determine lung recruitability

Answer 20

1. Distribution of lung lesions –> focal (nonrecruitable) versus diffuse (recruitable)
2. Predominant lesion type –> interstitial edema, compressive and congestive atelectasis (recruitable) versus complete alveolar filling (nonrecruitable)
3. Timing of recruitment maneuver compared to onset of ARDS - unlikely to be beneficial with ARDS of more than 3-5 days

Question 21

List methods to assess the effectiveness of recruitment maneuvers

Answer 21

• CT scans
• Pressure-volume curve
• Electrical impedance tomography
• Lung ultrasound
• Stress index
• Recruitment-to-inflation ratio

Question 22

Describe the “stress index” in mechanical ventilation

Answer 22

Assessed on the pressure-time scalar in volume-controlled ventilation
linear line equals stress index of 1

stress index < 1 - downward concavity = recruitment
stress index > 1 - upward convacity = overdistention