Mechanical ventilation resident survival guide

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Syed Hassan A. Kazmi BSc, MD [2]

Mechanical ventilation Resident Survival Guide Microchapters

Overview
Classification
Indications
FIRE
Mode and variable selection
Do's
Donts

## Classification

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Mechanical ventilation may be classified into non-invasive and invasive mechanical ventilation. Non-invasive mechanical ventilation can be further sub-divided into continuous positive airway pressure breathing (CPAP), bilevel positive airway pressure breathing (BiPAP) and mask ventilation. Mechanical ventilators may also be classified based on the basic underlying mechanics of the device and the clinical condition in which it is used. Ventilatiuon may be delivered via bag valve mask, continuous flow, transport ventilators, ICU ventilators, NICU ventilators and PAP ventilators.

## Indications

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The following are the indications of mechanical ventilation:

* Cardiac or respiratory arrest
* Tachypnea or bradypnea with respiratory fatigue or impending arrest
* Acute respiratory acidosis
* Refractory hypoxemia
* Refractory hypoxemia (when the P a O 2 could not be maintained above 60 mm Hg with inspired O 2 fraction (F I O 2 )>1.0)
* Inability to protect the airway associated with depressed levels of consciousness
* Shock associated with excessive respiratory work
* Inability to clear secretions with impaired gas exchange or excessive respiratory work
* Newly diagnosed neuromuscular disease with a vital capacity <10 - 15 mL/kg
* Short term adjunct in management of acutely increased intracranial pressure (ICP) intracranial pressure (ICP)

### Non-Invasive mechanical ventilation

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Consider non-invasive mechanical ventilation especially in the following conditions:

* COPD exacerbation
* Cardiogenic pulmonary edema
* Obesity hypoventilation syndrome
* Patients with asthma or patients with non-cardiogenic hypoxemic respiratory failure

## FIRE: Focused Initial Rapid Evaluation

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A Focused Initial Rapid Evaluation (FIRE) should be performed to identify patients of severe acute respiratory failure and in need of immediate intervention.

Boxes in red signify that an urgent management is needed.

Abbreviations

Boxes in red signify that an urgent management is needed.

Template:WH Template:WS

Assess the patient for respiratory distress

❑Color (Nail bed or lip cyanosis, pale or diaphoretic)

❑Respiratory rate

❑Breathing pattern

❑Use of accessory muscles

❑Paradoxical chest movement

❑Easily audible breath sounds

❑Work of breathing

❑Past medical history of COPD/COPD exacerbation, asthma

❑Pulmonary crepitations/rales/crackles

❑Third heart sound (S3)

❑Look for critical values on ABGs (pH <7.25, PaCO2 >55 mm Hg and rising, PaO2 < 70 mm Hg, alveolar-arterial O2 difference > 450, PaO2/PAO2 <0.15)

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Does the patient have any of the following findings that require invasive ventilation?

❑Respiratory arrest

❑Respiratory rate >35 breaths/min

❑Severe dyspnea with use of accessory muscle of respiration

❑Life-threatening hypoxemia (PaO2 <40 mm HG or PaO2/FiO2 <200)

❑Severe acidosis (pH <7.25) and hypercapnia (PaCO2 >60 mm Hg)

❑Cardiovascular complication (Hypotenion, shock, heart failure)

❑Failure of non-invasive mechanical ventilation<

❑Upper airway obstruction

❑Inability to protect airway

❑Inability to clear respiratory secretions

❑Facial or head surgery/trauma

❑Hemodynamic instability

❑Uncooperative patient

❑HACOR score > 5 at 1 h of non-invasive ventilation

Yes

| No|

Switch to invasive mechanical ventilation

Continue non-invasive mechanical ventilation

Initial stabilization:
❑Always elevate the head of the bed >30 º

❑Use ulcer and DVT prophylaxis, unless contraindicated

❑Use lung protective ventilation strategy for patients with acute lung lnjury (TV ~ 6 ml/kg ideal body weight, Plat pressure < 30 cmH 2 O)

❑Modify ventilator settings primarily to achieve patient-ventilator synchrony. If this fails, use the least amount of sedation required to achieve comfort and avoid unnecessary neuromuscular blockade

Initial parameters and protocols for adults

❑Volume-Ventilation may be used for the majority of patients, but pressure ventilation (PV or PRVC) should be considered in cases of high Peak pressure and plateau pressure (PIP > 40 cm H2O, Pplat > 30 cm H2O)

❑Tidal Volume: 4 to 12 mL/Kg of ideal body weight (IBW), while maintaining plateau pressure < 30 cm H2O and delta P < 20 cm H2O.

❑Minute ventilation: 4.0 x BSA (Body Surface Area) = VE (L/min) for males and 3.5 x BSA = VE (L/min) for females adjusted for altitude and body temperature while maintaining plateau pressure < 30 cm H2O and delta P <20 cm H2O.

❑Rate: 8 to 26 breaths/minute adjusted to achieve optimum total cycle time and maintain desired minute ventilation, while maintaining plateau pressure < 30 cm H2O and delta P < 20 cm H2O.

❑FiO2: Initial setting of 0.6 to 0.9 until results from arterial blood gases (ABG) can be obtained and the setting adjusted

* Initial ABG should be obtained 15-45 minutes from start of ventilation
* Pulse oximetry should be correlated with initial ABG and the patient subsequently monitored with continuous pulse oximetry to maintain SpO2 at or above patient’s normal or >90% SpO2 (Oxygen saturation by pulse oximetry).
* PEEP 5 to 15 cm H2O. Set initial PEEP at 5 cm H2O, unless otherwise indicated. Higher PEEPs may be required with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS)

❑Pressure Support (PS): 8 to 20 cm H2O. Maintain Pplateau <30 cm H2O and delta P < 20 cm H2O. PS should be adjusted to reduce work of breathing and patient fatigue and support effective ventilation.

❑I:E ratio less than 1:1 (example 1:3). The I:E ratio should be optimized along with total cycle time (TCT) to provide optimum mean airway pressure, lung filling, lung emptying (minimizing air-trapping/Auto-PEEP), patient/ventilator synchrony

Ventilator adjustments Based on the following assessments:

❑General appearance, vital signs, breath sounds and hemodynamic stability should be evaluated prior to and during any ventilator adjustments.

❑For a pH < 7.30, evaluate to ensure the cause is respiratory. If appropriate, increase rate to a maximum of 24 breaths/min until pH is > 7.30. If further adjustment is needed increase VT until PIP > 40 cm H2O or Pplateau > 30 cm H2O. If unable to maintain these parameters, consider allowing permissive hypercapnia.

❑For a pH > 7.45, evaluate to ensure the cause is respiratory. If appropriate, reduce rate to a minimum of 8 breaths/minute or until pH is < 7.45. After rate is decreased to 8 breaths/minute, if pH is still > 7.45, reduce volume to a minimum of 4 mL/Kg (IBW).

❑PaO2 or SpO2 values should be patient centered

❑Hemoglobin should be checked to ensure the absence of anemia.

❑Check hemodynamic variables to ensure adequate circulation.

❑If PaO2/FiO2 ratio is < 300, or, should settings of FiO2 = 0.5 and PEEP = 12 cmH2O be insufficient to maintain an appropriate oxygenation level, an intensivist

or pulmonologist should be contact and the ALI/ARDS protocol considered

Monitoring The following paramenters should be monitored in a patient in an intubated patient: ❑Check airway:

* Auscultate breath sounds q2-4 h
* Perform suction for crackles, coughing and decreasing SaO2
* Hyperoxygenate after each suction
* Monitor airway pressures q 1-2 h
* Administer bronchodilators and mucolytics as indicated
* Turn side to side q 2 h
* Monitor ABGs and pulse oximetery

❑Check circulation:

* Assess hemodynamic effects of positive pressure ventilation (e.g. decreased venous return leading to decreased cardiac output and hypotenion)
* Monitor EKG for arrhythmia secondary to hypoxemia
* Maintain intravascular volume by IV fluid support
* Monitor input and output of fluids, urine specific gravity, serum osmolality
* Monitor hydration status by clinical examination, viscosity of airway secretions
* Monitor electrolytes

❑Check safety of tube:

* Securely stabilize endotracheal tube
* Record the "cm" line on endotracheal tube (ETT) position at lips or teeth
* Evaluate ETT position by daily chest X-ray
* Manual resuscitation bag should be readily available
* Inflate cuff by using pressure < 25 mm Hg by manometer
* Monitor cuff-leak
* Protect pilot baloon from damage
* Check ventilator alarms q 4 h

Weaning from invasive mechanical ventilation

Clinical criteria

* Resolution of acute phase of disease
* Adequate cough reflex
* No excessive secretions
* Hemodynamic stability

Ventilator criteria

* PaCO2 < 50 mm Hg
* Vital capacity > 10 ml/Kg
* Spontaneous tidal volume > 5 ml/Kg
* Spontaneous respiratory rate (f) < 35/min
* f/Vt <100 breaths/ml/min
* Minute ventilation < 10 L with ABGs within normal limits

Oxygenation criteria

* PaO2 without PEEP > 60 mm Hg at FiO2 0.4
* PaO2 with PEEP (< 8 cm H2O) > 100 m Hg at FiO2 0.4
* SaO2 > 90% at FiO2 0.4
* PaO2/FiO2 greater than equal to 150
* P(A-a)O2 < 350 mm Hg at FiO2 1.0

Weaning from invasive mechanical ventilation takes into account the clinical condition of the patient and follows ATS/ACCP guidelines:

❑For acutely hospitalized patients on ventilator for > 24 hours the initial Spontaneous breathing trial (SBT) be conducted with inspiratory pressure augmentation (5-8 cm H2O) rather than without (T-piece or CPAP)

❑For acutely hospitalized patients on ventilator for > 24 hours, sedation should be minimal

❑For patients at high risk for extubation failure who have been receiving mechanical ventilation for > 24 h and who have passed SBT, extubation to preventetive NIV is recommended

❑For acutely hospitalized patients who have been mechanically ventilated for > 24 h, protocolized rehabilitation directed toward early mobilization is recommended

❑Perform a cuff-leak test (CLT) in mechanically ventilated adults who meet extubation criteria and are deemed at high risk for post-extubation stridor

❑For adults who have failed a CLT but are otherwise ready for extubation, administer systemic steroids at least 4 h before extubation