3 Objectives Know when to mechanically ventilate Understand basic settings: all about the CO2 and O2Learn about two main vent modes: AC and PSThere are 174 methods of positive pressure ventilation!! But this is actually much more complicated than it needs to be.
4 When to intubate?Patient cannot protect their airway…what does that mean?Sepsis, oftenHypercapniaHypoxiaSevere work of breathingObtundation
5 Ventilation RR and Tidal Volume affects ventilation and alters CO2 Tidal volume: volume of air moved in and out of lungs during quiet breathingTidal volumes should 8-10cc/kg of ideal body weight = height based, changes with sexVentilation in ARDS: tidal volume between 5-8cc/kg with higher PEEPCommon setting for RR: 12Common setting for Tidal Volume: 500 mL
7 Oxygenation FiO2 and PEEP affects oxygenation and alters O2 PEEP: Positive End Expiratory PressureSet initial FiO2 on high side, usually 100%, then can titrate down based on ABGCommon FiO2 setting initially: 100%; check gas, then drop to 60%Try to use as little FiO2 as possible to maintain pulse ox %
9 Modes: the basicsAssist Control: SET volume or pressure, with additional breathes triggered by patientVolume Control: can ventilate more consistently in setting of bad lung compliancePressure Control: allows limits for peak inspiratory pressure and avoid barotrauma
10 Modes: the basicsPressure Support: patient controls when a breath terminates (versus AC), allows them to determine tidal volume and inspiration timeVent gives a certain additional pressure to overcome the diseased lung + tubingUsed during weaning, also know as CPAP trialCommon settings: Pressure Support of 10 with PEEP of 5
11 Case 1:56 year old male admitted to UCI MICU for hypoxic respiratory failure secondary to community acquired pneumonia, requiring intubation. You are the night time intern. At 1am the ICU RN pages you. You call back:“Hey doc, the vent is beeping and it says that the peak pressure is pretty high all of a sudden, can you come take a look?”
13 Case 1:Check plateau with inspiratory pause (the “I” button, stands for “Intern”)Peak pressure is usually a static measurement, think of it as patient’s chest wall + vent tubing + airway of the lungsPlateau pressure is usually a dynamic measurement of the compliance of lung parenchyma, think of it as everything except peak pressurePlateau is measured by holding the “Insp Hold” or inspiratory hold button for 1 sec, timed at the end of inspiration If peak is high and plateau is low = obstruction
14 Case 1:If only peak pressure is high (therefore lung parenchyma/plateau is ok), think about something obstructing the air from getting to the lungs such as: mucous plug, bronchospasm, patient biting the vent, the vent tubing became disconnected!
15 Case 1:If both peak and plateau are high, think about what’s wrong with lung compliance, in addition to everything elseIs the patient developing worsening ARDS, pulmonary edema, pneumothorax, pleural effusion, ETT into one bronchus?
16 Case 2:34 year old female admitted to the UCI ICU for hypercapneic respiratory failure due to severe asthma exacerbation, requiring intubation. 3 hours into her admission the nurse calls you:“Doc I think we need to start antibiotics and levophed now! Her blood pressure suddenly went south, it was 130s about an hour ago and now it’s in the 70s! And she’s de-satting!”
17 Case 2: COPD/asthma = desatting, increasing CO2 retention Breath-stacking also known as auto PEEP can be caused by obstructive airway diseasesThis leads to decreased venous return by increasing intrathoracic pressureThis can lead to hypoxia as well
18 Case 2: Many ways to help stop auto-PEEP or breath stacking: Decrease RR effectively increases expiratory timeDecrease tidal volumeIncrease the E in I:E ratio (advanced)Increase sedation/analgesia/even adding neuromuscular blockade (advanced)
19 Summary When to mechanically ventilate Basic settings Cannot protect airway, work of breathing, obtundation, high CO2 or low O2Basic settingsAC VCRR 12, VT 500, PEEP 5, FiO2 100%Two vent modes: AC and PSPS for weaning, also know as CPAPTwo casesDifference between peak and plateau pressureBreath stacking in obstructive airway disease