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Critical Care

Ventilated Patient Management



Critical Care Tips – Respiratory


Ventilator Parameters


Airway & Respiratory Distress

Early signs and symptoms:

Tachycardia      Tachypnea        Hypertension                Use of Accessory Muscles

Decreased Levels of Consciousness           Decreased Oxyhemoglobin Saturation (SPO2)

Circum-oral Cyanosis      Paleness to nailbeds   Complaint of Shortness of Breath


Late signs and symptoms:


Unconsciousness   Bradycardia   Bradynpnea   Hypotension   Loss of respiration

Generalized Cyanosis


Airway Management Techniques


Supplemental Oxygen by:


Nasal Canula - effectively delivers up to 55% oxygen. Maximum flow rate is 6 Liters per minute                FIO2 calculation:     FIO2 =( Flow Rate (in LPM) * 4 ) + 21%


Simple Mask - similar to Nasal canula


Venturi Mask -  flow rate and FIO2 determined by venturi device inserted in Oxygen supply line.


Non-Rebreather Mask – delivers up to 100% oxygen based upon reservoir in supply line.




Endotracheal Tube (Intubation ) - Airway of Choice in unconscious patients without a gag reflex. Provides easy access for mechanical ventilation and management of airway secretions.  Disadvantage is that advanced training is required to place ET tubes.


Laryngeal Mask Airway – provides indirect airway management, protects airway from oral secretions. Is easily used in pre-hospital situations.


Esophageal Combitube – provides airway management and the ability to manage airway secretions.




  1. Assess level of sedation and medications administered over the last 6 hours prior to weaning attempt.
  2. Assess for signs and symptoms of adequate ventilation.

Stable PCO2, symmetrical chest movement, absence of dyspnea, headache, crackles or rales, stable level of consciousness and orientation, stable blood pressure & hemodynamics, cardiac rate & rhythm.


  1. Assess for signs and symptoms of adequate oxygenation within desired limits for patient. 

Stable PO2, respiratory rate within normal limits (generally <24), stable level of consciousness and orientation, absence of dyspnea or central cyanosis, stable blood pressure, stable heart rate and rhythm.


  1. Assess the patient’s breathing pattern. An abnormal breathing pattern may indicate that the patient is not ready to be weaned.

Assess for absence of accessory muscle use, tracheal tug, respiratory alternans and respiratory muscle paradox.


5.      Assess arterial blood gases on an FIO2 of 40% or less.

 Assess for pH >7.30 or <7.50, PO2 >60 and PCO2 >30 & <50


6.      Assess chest x-ray for proper tube placement, absence of atelectasis, pneumonia or pulmonary edema.

   Assess for end of ET tube on CXR 2 cm above carina


7.      Note current ventilator settings and compare with MD orders.


8.      Measure Respiratory parameters


Vital Capacity (VC) 3 times

Vital Capacity is the patient’s ability to take deep breaths and cough. Must be at least 10cc/kg of body weight

Negative Inspiratory Force (NIF) 4 times

NIF evaluates the patient’’s ability to generate sufficient intrathoracic pressures for deep breathing and airway clearance. Must be > -20 cm H2O.

                        Minute Volume (Ve) Measure for one full minute

Minute volume is a proxy indicator of the work of breathing. If minute volume is high, the work of breathing is excessive and the patient will fatigue with spontaneous breathing.

Must be >10 L/min.

                        Tidal Volume (Vt)

Tidal Volume is a good indicator of the patient’s strength. Patient should also be able to lift head up off of the bed or pillow for 5 seconds. Divide the minute volume by the respiratory rate to determine the average spontaneous tidal volume.

Vt should be > 5ml/kg.




SIMV – Spontaneous Intermittent Mandatory Ventilation

Spontaneous breaths + preset number of machine breaths.


CMV – Continuous Mandatory Ventilation

        Use when patient’s respiratory rate is greater than 20 breaths per minute.

        CMV rate must be higher than mastery rate if patient is on a rate of 8 or less

        Ventilator cannot lock patient’s spontaneous breaths out.

        Can not have pressure support in this mode. It automatically converts to PEEP


MMV – Minimal Minute Volume or Mandatory Minute Volume Ventilator monitors the patient’s minute volume and gives support only when the preset volume level is not attained.

        Post-op patients can wean themselves

        Set rate and tidal volume

        Set reasonable high rate alarm (except when patient has a high rate and low volume)

        There is usually a delay when initiating this mode due to ventilator’s need to sense the patient’s intrinsic respiratory rate.



        Set FIO2

        No PEEP

        May have Pressure Support set


CPAP – Constant Positive Airway Pressure – a residual pressure greater than atmospheric pressure at the end of expiration on spontaneous breaths. Increases PO2 with a lower FIO2.



            Pressure remaining in ventilator circuit to hold alveoli open between breaths.  Generally initiated in 5mmHg



        Usually start at 10

        Functional with every spontaneous breath

        Decreases work of breathing

        Pressure support is set as sum of PEEP and Pressure support





D = Displacement- dislodgement of tube, check for tube placement

O = Obstruction – mucus plugs, kinked tubing, mechanical obstructions

P = Pneumothorax – check breath sounds and chest x-rays

E = Equipment Failure – disconnect from ventilator and manually with bag-mask valve. If able to easily ventilate patient, suspect equipment failure and replace ventilator.




Ventilator Weaning is successful if:

1.      ABGs remain within acceptable range.        PCO2 <50, PO2 > 65,pH >7.32,             SPO2 >90%

2.      Neurological status is stable.           Awake and alert, able to understand and follow commands.

3.      Strength is adequate to maintain respiration independently for no less than 30 minutes. Strength equals Vt > 5ml/kg, Ve < 10 l/min, VC >10 – 15 ml/kg, NIF > -20 cm H20 able to lift head > 5 seconds, respiratory rate < 25 breaths/min.

4.      Patient remains free of signs of respiratory distress as follow:

        Increased respiratory rate

        Increased pulse


        Poor quality of voice and ineffective cough

        Decreased level of consciousness

        Unstable vital signs

        Ineffective airway clearance

        Signs of laryngeal edema or spasm






        Slight increase in respiratory rate from baseline

        Expressed feelings of increased oxygen need, breathing discomfort, fatigue, warmth

        Inquiries about possible machine dysfunction

        Increased focus or concentration on breathing


MODERATE:  The last 6 digits together may indicate a failure to wean.

        Slight increase in blood pressure <= 20 mmHg over baseline

        Slight increase in heart rate < =20 beats per minute over baseline

        Increase in respiratory rate <= to 5 beats per minute over baseline

        Wide-eyed look (eyewidening)


      Decreased air entry heard on auscultation

      Slight respiratory accessory muscle use

      Skin color changes: pale, slight cyanosis


      Inability to respond to coaching

      Inability to cooperate

      These items together may indicate failure to wean and may require a return to previous settings or a reintubation  of a previously extubated patient. After one hour reevaluate the patient to determine if settings need tobe changed. Consult a physician to determine further actions.


SEVERE: ABORT any attempt to wean patient! Immediately call a physician for further instructions.



      Significant deterioration in ABGs from patient’s baseline.

      Increase in blood pressure > 20 mmHg from baseline

      Increase in heart rate > 20 beats per minute from baseline

      Significant increase in respiratory rate from baseline

      Shallow, gasping breaths

      Adventitious breath sounds

      Full respiratory accessory muscle use

      Paradoxical abdominal breathing

      Uncoordinated breathing with the ventilator

      Profuse diaphoresis


      Decreased level of consciousness

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