Invasive Ventilatory Support



Invasive Ventilatory Support



Objectives


Upon the completion of the chapter activities and content review topics, the student should be able to:


1. Describe the physiologic goals of mechanical ventilatory support.


2. Describe the clinical objectives of mechanical ventilatory support.


3. Distinguish between volume and pressure modes of mechanical ventilation.


4. Choose the appropriate initial ventilator settings and alarms.


5. Calculate dynamic and static compliances (CD and CS).



Key Terms













Mechanical ventilation is arguably the topic that causes the most apprehension for respiratory therapy students. With numerous different ventilators and inconsistent mode terminology adding to the complexity of this life-support technology, a strong foundation with regard to the pulmonary system and its cardiovascular overlap is imperative. A ventilator simply pushes air into the patient’s lungs. A critical factor in successful mechanical ventilation depends on how skillfully the respiratory therapist (RT) can manipulate pressures, volumes, and flows in a way that will optimize a patient’s oxygenation, ventilation, and acid–base balance. All of this must be accomplished while minimizing the possible adverse effects of mechanical ventilation.



image Reality Check The most influential variable in the success of patients receiving mechanical ventilation is the knowledge of the therapists taking care of them!


While learning the art of mechanical ventilation, remember not to get caught up in all the “bells and whistles” that the technology of respiratory care offers you as a therapist. A ventilator is merely a very expensive piece of equipment at a patient’s bedside if the RT operating it does not know how to effectively use it to benefit the patient. Initiation of mechanical ventilation may be the result of countless patient scenarios, physiologic objectives, and clinical goals. Essentially, patients are intubated and mechanically ventilated because they cannot oxygenate, ventilate, protect their airway, or maintain their secretions. These circumstances are explained in Box 22-1. This chapter will discuss the aspects of initiation of mechanical ventilation as well as the care of the patient receiving mechanical ventilation.



Box 22-1   Goals and Objectives of Ventilatory Support





» Skill Check Lists


22-1 Initiating Invasive Mechanical Ventilation


A majority of patients are placed in a volume control mode of ventilation following intubation and initiation of mechanical ventilation. In this mode, the RT selects a tidal volume for delivery based on the patient’s ideal body weight (IBW), also referred to as predicted body weight. Two different formulas for both men and women are given in Table 22-1. The patient’s current reason for mechanical ventilation along with any underlying pulmonary condition needs to be taken into consideration when choosing mode and settings for mechanical ventilation. Typical values for both volume and pressure control ventilation are provided in Table 22-2. The mode choice and the settings are different for the patient intubated and mechanically ventilated for a surgical procedure with no pulmonary history, compared with the patient whose pulmonary status is deteriorating from pneumonia and exacerbation of chronic obstructive pulmonary disease (COPD).




TABLE 22-2


Typical Values for Initiation of Volume or Pressure Control Ventilation in the Adult Patient























































Setting Typical Value
Tidal volume  
For normal lungs
For COPD
For ALI/ARDS
Acute asthma
Neuromuscular disease		 6–8 mL/kg IBW
Begin at 6–8 mL/kg
4–8 mL/kg IBW to maintain Pplateau <30 cmH2O
4–6 mL/kg IBW
6–10 mL/kg IBW
Peak inspiratory pressure Frequency Pressure level to achieve 6–8 mL/kg IBW
Respiratory Rate  
For Normal Lungs
For COPD
For ALI/ARDS
Acute asthma
Neuromuscular disease		 12–16 breaths/min
10–12 breaths/min
20–35 breaths/min
10–12 breaths/min
12–16 breaths/min
Inspiratory time 0.8–1.2 seconds
Longer expiratory time for patients with obstructive disease
Flow  
Inspiratory flow
Volume control flow pattern		 60–100 L/min
Decreasing ramp
PEEP  
Most patients without ALI
ALI
ARDS
COPD/Asthma		 5 cmH2O
5–10 cmH2O
10–15 cmH2O
5 cmH2O
TRIGGER SENSITIVITY  
Pressure
Flow		 –0.5–2.0 cmH2O
2–3 L/min
PRESSURE LIMIT  
Volume mode
Pressure mode
Peak pressure alarm		 40 cmH2O
30 cmH2O
Once patient is connected and stabilized adjust to 10–15 cmH2O above PIP
Initial FiO2 1.0 and lower as quickly as possible based on patient’s ABG values and condition
Humidification H/H provide 35°C at the airway connection or appropriate HME

ALI, Acute lung injury; ARDS, acute respiratory distress syndrome; COPD, chronic obstructive pulmonary disease; HH, heat and humification; IBW, ideal body weight; L/min, liters per minute; mL/kg, milliliter per kilogram; PEEP, positive end-expiratory pressure; PIP, peak inspiratory pressure.



image Reality Check No “formula” exists for mode choice when initiating mechanical ventilation. Mode choice needs to be based on what is best for the patient at that time.



image Reality Check Lung protective therapy should be on your mind as soon as the decision is made to intubate and mechanically ventilate the patient.


The following is the step-by-step process for initiating mechanical ventilation.




Implementation




1. Assess vital signs.


2. Establish and implement the appropriate settings for the following setup decisions:



3. Establish and implement the appropriate settings for the following ventilatory values:



4. Attach the patient to the ventilator.


5. Perform initial assessment of ventilatory support:



6. Establish and implement the appropriate settings for the following alarms and backup values:



7. Allow enough slack on the circuit so that the artificial airway remains secure.


8. Confirm or place the manual ventilation device at the patient’s bedside.


9. Remove the supplies from the patient’s room, and clean the area, as needed.


10. Remove PPE, and perform proper hand hygiene prior to leaving the patient’s room.





22-2 Assessing a Patient-Ventilator System


With so many intricacies involved in the management of a patient receiving mechanical ventilation, the term “vent check” seems unimportant; however, it is a deceptively trivial expression of the contemplation and skill that actually go into a patient-ventilator system assessment. The evaluation procedure should begin with a careful patient assessment. All current laboratory values, chest radiographs, and the health care provider’s progress notes should be reviewed prior to entering the patient’s room.


Typically, patients are placed on an FiO2 of 1.0 following intubation and initiation of mechanical ventilation. This should be one of the first parameters that need to be adjusted. Once the patient is stabilized a blood gas sample is drawn and interpreted, and the FiO2 should be lowered slowly, if indicated. An FiO2 adjustment formula is given in Box 22-2.



Box 22-2   Adjusting FIO2 of a Ventilated Patient





image Reality Check Because many patients are on isolation precautions, manometers to measure cuff pressures will not always be readily available.


The following is the step-by-step process for assessing a patient-ventilator system.



Procedural Preparation




1. Review the patient’s chart for patient’s current vital signs and ventilator settings.


2. Review the patient’s most recent blood gases or SpO2.


3. Review the most recent chest radiograph.


4. Identify current sedation medications.


5. Verify the physician’s order or the facility’s protocol for standard of care.


6. Obtain, clean, and inspect the appropriate equipment prior to entering the patient’s room.


7. Identify the patient using two patient identifiers.


8. Follow PPE requirements, and observe standard precautions for any transmission-based isolation procedure.


9. Introduce yourself to the patient and to the family.


10. Explain the procedure to the patient and to the family, and acknowledge the patient’s understanding.


11. Perform proper hand hygiene, and put on gloves, mask, and protective eyewear, as appropriate for the procedure.



Implementation




1. Approach the patient before you approach the ventilator.


2. Assess the patient for:



3. Assess ventilator functions and settings:



4. Ensure that the manual ventilation device and the suction equipment are available at the patient’s bedside.


5. Ensure that replacement tracheostomy tubes are available at the patient’s bedside.


6. Remove the supplies from the patient’s room, and clean the area, as needed.


7. Remove PPE, and perform proper hand hygiene prior to leaving the patient’s room.





22-3 Compliance Calculations


Part of your patient-ventilator system assessment includes calculation of the patient’s dynamic compliance (CD) and obtaining a Pplateau to calculate the static compliance (CS) (Box 22-3). Evaluation and trending of these compliance values is a good way to monitor the progression of your patient’s pulmonary status.



Box 22-3   Calculating Dynamic and Static Compliance


Dynamic compliance CD=VTPIP−PEEP


image


Static compliance CS=VTPPlateau−PEEP


image

PIP, Peak inspiratory pressure; PEEP, positive end-expiratory pressure; VT, tidal volume.


The following is the step-by-step process for compliance calculations.



image Reality Check The patient’s family members are more interested in how the patient is doing than exactly what diagnostic test or procedure you are performing.




Implementation




1. Perform a patient-ventilator system assessment (see PA 22-2).


2. Identify PIP.


3. Identify exhaled tidal volume.


4. Identify PEEP.


5. Identify auto-PEEP.


6. Identify total PEEP (PEEP + auto-PEEP).


7. Identify dynamic compliance (CD):



8. Identify static compliance (CS):



9. Remove supplies from the patient’s room, and clean the area, as needed.


10. Remove the PPE, and perform proper hand hygiene prior to leaving the patient’s room.


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Jun 12, 2016 | Posted by in RESPIRATORY | Comments Off on Invasive Ventilatory Support

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