Positive Pressure Ventilation (PPV)
preset volume ventilators (either volume limited or volume cycled)
preset pressure ventilators (either pressure limited or pressure cycled)
Volume Ventilators
a preset tidal volume (Vt) is delivered to the patient in each machine breath (once delivered inspiration ends)
volume limited can develop an inspiratory pressure that maintains the preset tidal volume when changes in airway resistance and compliance occu
Pressure Cycled Ventilators
preset inspiratory pressure is delivered to the patient and once reached inspiration ends
delivered tidal volume is unknown but varies with the changes in airway resistance and compliance
when the lung compliance decreases, the delivered tidal volume decr
Pressure Control Ventilation (PCV)
used as a general mode of ventilation for ARDS
INITIAL SETTINGS:
the initial settings should include a peak inspiratory pressure (PIP) of about 50% of that on volume ventilation
peak inspiratory pressure should be set to obtain a specific exhaled tidal vo
Pressure Control Ventilation (PCV)
studies show this mode of ventilation improves gas exchange, increases oxygenation, reduces peak inspiratory pressure (PIP), increases mean arterial pressure (MAP), reduces required positive end expiratory pressure (PEEP), and decreased minute ventilation
BiLevel
mode of pressure ventilation
may be either time cycled or patient cycled
uses two pressures: IPAP and EPAP
Assist Mode
patient initiates inspiration by creating a preset negative pressure which delivers a machine control breath
sensitivity control determines how much negative pressure is required to initiate inspiration (usually between -.5 and -2)
the patient must initia
Control Mode
the patient cannot initiate inspiration in this mode
inspiration is initiated by a timing device
the patient should be very heavily sedated or paralyzed on this mode
the minute volume remains constant because the rate cannot be altered
Assist Control Mode
the patient initates inspiration by creating a negative pressure, but if the patient fails to cycle the ventilator into inspiration, a backup respiratory rate is set and a machine tidal volume breath is delivered
the patient may initiate as many vent brea
Synchronized Intermittent Mandatory Ventilation (SIMV)
allows for spontaneous breathing along with positive pressure ventilation (PPV) breaths, which are built into the ventilator and senses when the patient is breathing spontaneously so breath stacking does not occur
used as both a weaning mode and a ventila
Pressure Support Ventilation (PSV)
patient assisted, pressure generated, flow cycled breath
can be augmented with SIMV or used by itself
designed to make spontaneous breathing through the endotracheal tube during weaning more comfortable by overcoming the high resistance and increased insp
Continuous Positive Airway Pressure (CPAP)
preset pressure is maintained in the airways as the patient breathes totally on their own (spontaneously breathing)
indications and hazards are the same as in PEEP
Tidal Volume (Vt)
determines the delivered volume to the patient in milliliters or liters
should be set to 6-12 ml/kg of ideal body weight depending on the patients condition
enough should be used so that it doesn't cause overdistention of the alveoli
best to maintain alve
Alveolar Ventilation
increasing tidal volume increases this along with increasing the minute ventilation, which decreases PaCO2
decreasing tidal volume decreases this while also decreasing minute ventilation, which increases PaCO2
On Volume Ventilators
increasing tidal volume increases I-time
decreasing tidal volume decreases I-time
the preset machine tidal volume IS NOT the actual volume reaching the patient's lungs
volume is lost in the ventilator circuit because of airway resistance from gas flow
tub
Tidal Volume (Vt)
exhaled _____ is measured by and exhaled volume digital display
exhaled _____ is most accurately measured with a respirometer placed between the endotracheal tube and the ventilator Y adapter or at the exhalation valve
to most accurately measure ___ deliv
Respiratory Rate (RR)
normal is 8-12 per minute
adjusting rate control alters the E-time, which in turn alters the I:E ratio
increasing ____ decreases E-time
decreasing ____ increases E-time
adjusting ____ alters minute ventilation (Ve); an increase causes an increase in Ve; a
Inspiratory Flow Control
normal setting is 40-60 liters per minute
adjusting flow rate alters the I-time, which in turn alters the I:E ratio
increasing flow rate decreases the I-time
decreasing flow rate increases the I-time
I:E Ratio
comparison of I-time with E-time
normal adult/pediatric is 1:2; normal neonate is 1:1
tidal volume control: increasing tidal volume increases I-time; decreasing tidal volume decreases I-time
flow rate control: increasing flow rate decreases I-time; decrea
Oxygen Control
adjustable from 21%-100%
should be increased to a maximum level of 60% to maintain normal PaO2 levels
once 60% is reached either PEEP should be added or increased
reduce to 60% before reducing PEEP
Sensitivity Control
determines the amount of patient effort required to cycle the ventilator into inspiration
should be set to the patient generates between -.5 to -2 cmH20 pressure
if it takes more than -2 cmH20 pressure to cycle the ventilator into inspiration increase ___
Sigh Control
should be set at 6-12 per hour
volume should be 1.5 to 2 times the tidal volume
aids in prevention of atelectasis
usually not functional in SIMV
Inflation Hold
adjustable from 0-2 seconds
keeps the exhalation valve close during ventilator tidal volume to be held in the lungs for a preset time
used to improve oxygenation by reducing atelectasis and shunting and increasing the diffusion of gases
using an ______ ca
Expiratory Retard (Resistance)
used to prevent premature airway collapse during expiration
increases E-time, alters I:E ratio and increases intrathoracic pressure and increases MAP which may result in decreased venous return and decreased cardiac output
Positive End Expiratory Pressure (PEEP)
used to maintain positive pressure in the airway after a ventilator breath
Indications for PEEP
atelectasis
hypoxemia on 60% or more FiO2
decreased functional residual capacity (FRC)
lowering oxygen levels to safe levels
decreased lung compliance
pulmonary edema
Hazards of PEEP
barotrauma
decreased venous return
decreased cardiac output (CO)
decreased urinary output
Optimal PEEP
level of PEEP that improves the lung compliance without decreasing cardiac output (CO)
a mixed venous PvO2 may be obtained from the pulmonary artery; reflects cardiac output
normal PvO2 is 35-45 mmHg
PvO2 of less than 35 indicates a possible decrease in t
Ventilator Alarms
...
Low Pressure Alarm
5-10 below peak inspiratory pressure (PIP) alarm
activated by a leak in the ventilator circuit, chest tube, endotracheal tube cuff or a circuit disconnect
High Pressure Alarm
5-15 above PIP
when high pressure is reached on volume ventilator, inspiration ends prematurely, decreasing delivered tidal volume
activated by decreasing lung compliance, increasing airway resistance caused by secretions, bronchospasm, water in tubing, k
Low PEEP/CPAP Alarm
2-4 below baseline
activated for the same reasons as the low pressure alarm
Apnea Alarm
activated by the patients respiratory rate
activated after a preset time passes with no inspiratory flow through the tubing
IMPORTANT ALARM FOR PATIENTS ON VENTILATOR IN CPAP MODE OR LOW SIMV RATE
Low Tidal Volume Alarm
approximately 10% below the set tidal volume
activated for the same reasons as the low pressure alarm
Mean Airway Pressure (Paw)
average pressure applied to the airway over a set time period
directly affected by the ventilator rate, peak inspiratory pressure (PIP), I-time, inspiratory hold, expiratory retard, PEEP, pressure waveform, and I:E ratio
level that will improve oxygenatio
Formula to Calculate Mean Airway Pressure (Paw)
PIP-PEEP x I-time/TCT
Capnography (End Tidal CO2)
exhaled CO2 is measured
obtained by using a mass spectrometer
normal PETCO2 is the same as alveolar CO2 which is equal to your PCO2
noninvasive to obtain patients PaCO2 level
normal is 34-45 mmHg or 4.5-5.5%
there is a difference of approximately 2-5 mmHg
Indications for Mechanical Ventilation
apnea
acute ventilatory failure
impending acute ventilatory failure
oxygenation
Criteria for Initiation of Mechanical Ventilation
vital capacity (VC) of less than 10-15 mL/kg
(normal is 65-75 mL/kg)
A-a gradient of greater than 450 mmHg on 100% FiO2
(normal is 25-65 mmHg)
VD/VT ratio of greater than 60%
(normal is 25-35)
patient is unable to obtain a NIF of -20 cmH20
(normal is -50
Formula for VD/VT Ratio
PaCO2-PeCO2/PaCO2
Goals of Mechanical Ventilation
increased minute ventilation (Ve)
decreased work of breathing (WOB)
increased alveolar ventilation
maintenance of ABG levels within the normal range
improved distribution of inspired gases
Complications of Mechanical Ventilation
atelectasis- use a minimum of 8-10 mL/kg of ideal body weight and use a sigh breath occasionally
pulmonary oxygen toxicity- may result in ARDS
tracheal damage- usually at the cuff site
decreased venous return to the heart- results from positive pressure v
Dead Space (VD)
portion of the tidal volume that does not take part in gas exchange
Anatomic_____: consists of the conducting airways from nose to the terminal bronchioles (no gas exchange)
1 ml/lb of body weight
a trach decreases anatomic ______ by bypassing the upper a
Alveolar Dead Space
air reaches the alveoli but does not take part in gas exchange
results form lack of perfusion to air filled alveoli
may result from hyperinflated alveoli where blood is not able to use all the air
Physiologic Dead Space
sum of anatomic and alveolar dead space
most accurate measure of dead space
Mechanical Dead Space
vent circuits have a certain amount of this ranging from 75-150 mL
because anatomic dead space decreases when a patient has an endotracheal tube or a trach the dead space created by the circuit balances out
additional _____ may be added to the ventilatory
Lung Compliance
the ease with with the lung expands varies inversely with the pressure required to move a specific volume of air
the higher the ______, the easier it is to ventilate the lung
the lower the ______, the stiffer the lung is and the harder it is to ventilate
Dynamic Compliance
measured as air is flowing through the circuit and the airways (measurement of Raw)
changes with changes in Raw caused by water in the tubing, bronchospasm, airway secretions, and mucosal edema
Static Compliance
more accurate measurement of lung compliance because it is measure with no air flowing through the circuit and airways
airflow may be stopped with the volume remaining in the lungs by adjusting a 1-2 second inspiratory hold or by pinching expiratory drive
Points to Remember about Compliance
increasing plateau pressures indicate the lung compliance is decreasing or the lungs are harder to ventilate
if peak pressures are increasing but the plateau pressure remains the same, then lung compliance is NOT decreasing, but the Raw is increasing (usu
Causes of Decreasing Static Compliance
pneumonia
pulmonary edema
consolidation
atelectasis
air trapping
pleural effusion
pneumothorax
ARDS
Airway Resistance (Raw)
amount of pressure that is being delivered to the airways and how much is going to the alveoli; difference is the amount of pressure lost as a result of Raw
determine loss by subtracting plateau pressure from PIP
the closer the plateau pressure is to the
Normal Airway Resistance
unintubated patient: .6-2.4cmH20
intubated patient: 5 cmH20