ARDS

Dr. Tura Lencho Anesthesiology and Critical Care Medicine 4/25/2020

Objectives 1. ARDS brief review 2. Overview of mechanical ventilators3. Management of ARDS on MV

Diagnosis

● ARDS can be diagnosed once cardiogenic pulmonary edema and alternative causes of acute hypoxemic respiratory failure and bilateral infiltrates have been excluded.○ Mild: PaO2/FiO2 < 300○ Moderate: P/F < 200○ Severe: P/F < 100

Management Strategies for ARDS

● Noninvasive ventilation

● Invasive ventilation

Management of acute respiratory failureIntubated patients

Airway management ● Intubation

○ Indication:- Respiratory failure, airway protection, surgery○ Airway assessment:-

○ Induction: ensure (SOAP ME; Suction, Oxygen, Airway, Personnel, Meds, Equipments)

■ Regular - oxygen sedation oxygen intubate ■ RSI - oxygen - sedation intubate

○ Position:

Basic Terminologies

1. Tidal Volume (TV) - lung volume with normal inhalation and exhalation when extra effort is not applied

2. Respiratory rate (RR) - breath per minute

3. minute ventilation = TV x RR 4. PEEP- positive end expiratory pressure

5. FiO2 - fraction of inspired oxygen

6. inspiratory pressure - pressure applied to the lungs during inhalation7. Peak inspiratory pressure - the maximum pressure applied to the lungs during inhalation8. Plateau pressure (Pplat 0.5 second inspiratory pause)- pressure that is applied to the small airways and alveoli.

9. inspiratory to expiratory (I:E) ratio - usually 1:3

Mechanical ventilation modes

● Volume-modes 1. Assist-control ventilation (ACV) - set TV for spontaneous breath 2. Synchronized intermittent mandatory ventilation (SIMV) - variable TV

for spontaneous breath ● Pressure- modes :

1. Pressure control ventilation (PCV)2. Pressure support ventilation (PSV) - patient spontaneous3. Airway pressure release ventilation (APRV): Ph, PL, Th & TL

● Dual-modes: a. Pressure regulated volume control (PRVC)

Set by operator directly FiO2 PEEP RR TV Ipressure I:E

ACV yes yes yes yes no yes Additional spont. breath is a set TV

SIMV yes yes Yes minimum

yes no/ (yes

spontaneous part) NO Additional spont breath, TV

varies

PSV yes yes No No yes NO Patient controls RR & TV

PCV yes yes yes no yes yes TV depends on pressure

Volume modes Volume control SIMV

Pressure modesPressure control Pressure support

ARDS vent setting Lung protective vent setting

1. Low tidal volumes 6-8 ml/kg, based on predicted body weight (PBW) 2. PEEP > 5 cm HO23. Plateau pressure < 30 cm HO2

Goals:

1. Limit the risk of volutrauma 2. Limit the risk of atelectrauma3. Limit the risk of barotrauma

PBW M= 50 + 0.91 (height in cm-152.4) F= 45.5 + 0.91 (height in cm-152.4)

Troubleshootings 1. Hypoxia - Gaol - PaO2 55-80 or SpO2 88-95 %

a. Ensure appropriate ETT placement - auscultate b/l chest b. Suction ETT, check Peak & plateau pressuresc. Adjust vent setting: FiO2, PEEP, and I:E d. Avoid patient dyssynchrony with ventilatore. Prone position f. Paralyzing g. Extracorporeal membrane oxygenation (ECMO)

2.3. Hypercarbia

a. Adjust vent setting: TV, RR, and other checks as for hypoxia b. Consider permissive hypercarbia if hypoxia is also an issue

4. High pressure: a. High peak airway pressure = airway issue. Check ETT for kinking, mucous plug,

bronchospasmb. High plateau pressure = alveolar issue. No complaint lung

Galatooma !

Fayya Ta’a !

Reference

1. http://www.ardsnet.org/files/ventilator_protocol_2008-07.pdf

2.