MECHANICAL VENTILATION MODULE III Jeffery C Rooks (Craig) MMHC, RRT - PowerPoint PPT Presentation

MECHANICAL VENTILATION MODULE III Jeffery C Rooks (Craig) MMHC, RRT Arna Banerjee MD, MMHC, FCCM

Learning Objectives • Select appropriate initial ventilator settings (ventilator prescription). • Modify the ventilator prescription in response to pressure changes and arterial blood gas analysis. • Describe the differences between mandatory and spontaneous modes of mechanical ventilation.

Ventilator Circuit • Oxygen/air source • High pressure lines to ventilator • Inspiratory circuit to patient • Expiratory circuit • Exhalation

Other Features • Humidifier/heater • Bacterial filters • Attached suction devices

Control panel • Airway pressure gauge/digital display • Buttons for entry of settings • General alarm displays • Others – Flow rate – Pressure volume curves – Inspiratory to expiratory ratio (I:E)

CASE I Mr. Z, a 43-year-old, 60-kg patient, is admitted with a multidrug overdose. After observation in the intermediate care unit for 2 hours, the nurses have observed a worsening of the patient’s mental status with a decline in his GCS score to 6. The house physician has intubated the patient. After transfer to the ICU, the staff calls you to confirm the mechanical ventilator parameters ordered by the house physician.

MODES OF VENTILATION Use the mode that you are most familiar with

Settings • Mode AC or SIMV • Rate 12-15 breaths/min • Tidal volume (VT) 8 mL/kg ideal body weight • FIO2 100% • PEEP 5 cm H2O • PSV 5-10 cm H2O, if mode is SIMV (+PSV)

Assist Control Ventilation (AC) • Every breath delivered to patient is a mechanical breath (breath may be triggered by a timing mechanism – respiratory rate or patient effort) • Tidal volume is preset • Breaths are delivered at a preset frequency/rate • Pressure is variable throughout the delivered breath

Assist Control You set: Tidal volume Volume Controlled Peak flow (or I:E) Rate

Assist Control (A/C) Patient efforts recognized by ventilator

Pressure Support Pressure Support Positive pressure maintained in the CPAP ventilator circuit during the PS/CPAP inspiratory phase Inspiratory limb To patient Expiratory limb

Flow Cycling Flow (L/m) Set PS level CPAP level Volume (mL) Time (sec)

SIMV Synchronized Intermittent Mandatory Ventilation • Volume Control + Pressure Support • Mandatory breaths are Volume Control breaths (controlled) • Spontaneous breaths are pressure support (supported) • Ventilator provides mandatory breaths which are synchronized with patient’s spontaneous efforts at a preset rate

Flow (L/m) Pressure (cm H 2 O) Volume (mL) Spontaneous Breaths

Modifying Ventilator Settings

30 minutes after initiating mechanical ventilation, you obtain the following ABG: • What abnormalities does this show? – Acute (uncompensated) RESPIRATORY ACIDOSIS – Supranormal OXYGENATION • What adjustments should you make?

• To treat the RESPIRATORY ACIDOSIS: – Increase the respiratory rate to improve the minute ventilation • To treat the SUPRANORMAL OXYGENATION: – Decrease the FiO2 • Repeat the ABG in 20-30 minutes

Tips • PaC02 > 45 (or ETC02 > • Pa02 < 60 (Sp02 < 90%) 50) – Increase Fi02 – Increase Respiratory – Increase PEEP Rate – Increase Tidal Volume • Sp02 > 95% (or appropriate • PaC02 < 35 (or ETC02 < oxygenation for patient) 30) – Reduce Fi02 – Decrease Rate – Reduce PEEP to 5 – Decrease Tidal Volume

Increased Resistance What pressures are we interested in? Dynamic pressure OR Pressure Pressure Peak pressure ( P peak ) Static pressure OR Pressure Plateau pressure ( P plat)

• Normally Pplat = Ppeak – 5to10 cm H2O • Why are we more interested clinically in Pplat? Pplat Ppeak Puts a pause in the Inspiratory Cycle – no flow – measures pressure • Estimates alveolar pressure at end-inspiration • Indirect indicator of alveolar distension • Goal is Ppeak <40, Pplat <30

• Endotracheal tube compromise • Acute bronchospasm High • Pneumothorax Pressure • Gastric distension Alarm • Main stem intubation Differential • Pulmonary edema/change in lung Diagnosis compliance • Patient-ventilator dyssynchrony

If hypoxemic or decompensating, disconnect from ventilator and initiate manual ventilation • Auscultate lung fields and order Chest Xray • Confirmation of tube position and patency • Suction the Endotracheal Tube • Assess for tension pneumothorax • Bronchospasm • Patient agitated • Abdomen: rigid or distended

If hypoxemic or decompensating, disconnect from ventilator and initiate manual ventilation • Peak airway pressure – plateau pressure – if >10 cm H2O = airway resistance – if <5 cm H2O = decreased compliance In the patient with significant distress while on the ventilator, disconnection from the ventilator and reassessment can be diagnostic and therapeutic. (NOT APPLICABLE FOR COVID +VE OR SUSPECTED)

Decreased lung/chest compliance? • Chest wall rigidity • Alveolar dysfunction/collapse

Increased airway resistance • Airway obstruction • Bronchospasm • Circuit kink • Water in endotracheal tube and / or circuit • Check Filter if being used

Case II • A 62-year-old, 70-kg admitted for a small bowel obstruction – aspiration pneumonitis - intubated • SIMV rate 12, tidal volume 650 mL, PS 10 cm H2O, PEEP 5 cm H2O, FIO2 100% • CXR - diffuse alveolar infiltrates • Peak Pressure 45 cm H2O • Plateau pressure is 40 cm H2O. • ABG: pH 7.35, PaCO2 45 mm Hg, PaO2 80 mm Hg, HCO3 24 mmol/L.

Change to the Current Ventilator Settings • Reduce the V T to 6 mL/kg – V T calculation should be based on predicted body weight – not measured weight. – Further reduce V T to 5 mL/kg if plateau pressure remains above 30 cm H 2 O. – Reduction in V T may adversely affect CO 2 clearance

The patient continues to demonstrate worsening oxygenation with a SpO2 of 86% on a FIO2 100% What would likely improve oxygenation?

Improve Oxygenation • Increase PEEP in 2- to 3-cm increments every 30-min intervals • The effect is not immediate and as such it is generally recommended to allow 30 min after an adjustment before assessing efficacy • Prolong the inspiratory time, thus the amount of time spent at the inspiratory driving pressure.

CASE III • 18-year-old man severe asthma exacerbation - bronchodilator and IV corticosteroids • ABG severe respiratory acidosis PaCO2 >100 • Intubated • Vital signs: HR 160, BP 70/55, R 30, SpO2 88%. • Auscultation: minimal air movement. • Ventilator alarms: high respiratory rate, low tidal volume, and high peak airway pressure.

What is “Auto-Peep”? INSP FLOW EXP Expiratory flow Next breath ends before next begins before breath exhalation ends Obstructive lung disease (pursed lip) Rapid breathing (breath stacking) Forced exhalation (anxiety)

Decrease Auto-PEEP • Ventilator maneuvers include actions to enhance expiratory time. • Decreasing the set respiratory rate • Reducing the Tidal Volume • Increasing peak inspiratory flow rates.

Acknowledgement • Raeanna Adams, MD, MBA • Nathan Ashby, MD • Rob Hood, MD • Meredith Pugh, MD, MSCI • Kimberly Rengel, MD • Kyla Terhune, MD, MBA

Questions ?