Chapter 4 and 5
produced by the action of the respiratory muscles
produced by the ventilator
produce motion to deliver a volume of gas to the lungs (FLOW)
depends on two factors, compliance and resistance
equation of motion
pressure ventilation + pressure muscles=elastance X volume + resistance X flow
Ventilator controls - pressure Controller
the ventilator maintains the same pressure waveform at the mouth regardless of changes in the lungs
Ventilator controls - flow controller
Ventilator volume delivery and volume waveform remain constant and are not affected by changes in the lung. Flow is measured
Ventilator controls - volume controller
ventilator volume delivery and volume waveform remain constant and are not affected by changes in the lung. Volume is measured
Ventilator controls - time controller
pressure, volume, and flow curves can be changed as lung changes. Time remain constant
two factors that control inspiration
manufacturers design, and how the Ventilator set
two methods of delivering inspiration
volume ventilation and pressure ventilation
the operator sets the volume for delivery to the patient
volume ventilation is also called
volume targeted, volume limited, volume control
the operator sets the pressure for delivery to the patient
pressure ventilation is also called
Pressure targeted, pressure limited, pressure control
the primary Variable that the denominator adjusts to produce inspiration
the two, Commonly used control Variables
pressure and volume
the four control variables
pressure, volume, flow, time
if phase variable begins, some stains, and ends each four Phases of breath
Four phases of breath
Change from exhalation to inspiration, inspiration, change from inspiration to exhalation, exhalation
mechanism the Ventilator uses to end Exhalation and begin inspiration
5 triggering mechanisms
time, patient, pressure, flow, volume
4 limit variables
pressure, volume, flow, maximum pressure limiting
cycling Mechanisms of termination
volume, time, flow, pressure
two types of breath
mandatory and spontaneous
a period between inspirations
define baseline pressure
the pressure level in which a ventilator begins a breath
define time limited exhalation
ventilation mode that limits expiratory time
define continuous gas flow
gas flow provide at the end of exhalation because airway resistance is low. Many new ICU ventilators provide this.
negative end expiratory pressure (iron lungs)
define expiratory hold
a pause at the end of exhalation because it is measuring the pressure associated with air trapping (auto PEEP)
define expiratory retard
resistance on the expiratory side because of ventilator circuits, expiratory valves, and bacterial filters
Continuous positive airway pressure that helps improve oxygenation to a spontaneous breathing patient.
Positive pressure that remains in the airway at the end of exhalation . Improves oxygenation.
Evaluation of a patient in respiratory distress involves what three basic assessments?
patient's level of consciousness, color, vital signs
Evaluation of patient's LOC ask what type of questions?
are they awake? can they be aroused? what extent of consciousness are they?
Evaluation of color , appearance, and texture involve looking at what three variables?
naie beds, pale, level of diaphorisis
Vital signs include what in respiratory distress assessment?
rr, hr, bp, temp, spo2
define respiratory distress
absence or insufficient respiratory activity to maintain adequate oxygen uptake and carbon dioxide clearance AND the inability to maintain PO2, PCO2, and PH.
Define PO2 that would indicate respiratory distress
below predicted normal ranges
Define PCO2 that would indicate respiratory distress
50 mm hg or higher
Define a ph level that indicates respiratory distress
7.25 and lower
List two types of acute respiratory failure
List six reasons hypoxic failure would happen
v/q mismatching, diffusion defects, right to left shunting, alveolar hypoventilation, aging, inadequate inspired oxygen
Acute hypoxic failure is indicative of
a life threatening situation that may also be vital organ threatening to tissues
How would you treat hypoxic failure?
If acute hypoxic failure is occurring with hypercapnia,and WOB how do you treat?
Mechanical ventilation but it is a last resort
define acute hypercapnic failure
inability to maintain normal PaCo2
What can hypercapnia be caused by?
CNS disorders, neuromuscular disorders, any disorder that increases WOB
List some early indicators of hypoxia
decreased PaO2, tachycardia, tachypnea
list a early indicator of hypercapnia
PaCO2 levels are elevated unless receiving supplemental oxygen
What conditions can hypercapnia lead to, if not treated correctly
CO2 narcosis, cerebral depression, coma, death
CNS disorders reduce the drive to breath and can be caused by
drug over dose, trauma, hypothyroidism, CSA
Neuromuscular disorders include
paralytic disorders, paralytic drugs, and impaired muscle function
List some paralytic disorders
MG, Tetanus, Botulism, GB, Poliio, MD, ALS
List some paralytic drugs
Curare, Nerve gas, Succinycholine, insecticides
List some conditions that may effect muscle function
electrolyte imbalance, malnutrition, PN disorders, atrophy, fatigue, COPD
List some problems that occur because of an increase in WOB
pluera-occupying lesions, chest wall deformities, increased raw, lung tissue involvement, pulmonary vascular problems, post-op, hyperinflation
What two ventilator mechanics measurements are used most often to assess the condition of respiratory muscles?
What ventilator parameter is used most often to with acute asthma?
FEV1 is also used but not as much
What ventilator parameters are used to assess the need for invasive ventilation AND also indicators for discontinuing ventilation?
MIP, MEP, VC, Vt, F, FEV1, PEFR
What are normal and critical values of MIP (maximum inspiratory pressure)
N: -100 to -50
C: -20 to 0
What are normal and critical values of MEP (Maximum expiratory pressure)
C: 40 or less
What are normal and critical values of VC
C: 10 to 15
What are normal and critical values of Vt
C: 5 or less
What are normal and critical values of F (frequency)
C: 35 or more
What are normal and critical values of FEV1
C: 10 or less
What are normal and critical values of PEFR
List some physiological measurements (values) that are good indicators of oxygenation failure
PaO2 (less than 70 with a SPO2 of 90 on a FIO2 of 60% or less indicates hypoxic failure), SpO2, P [A-a]O2, PaO2/PAO2, P to F ratio
How do you treat hypoventilation?
increase alveolar ventilation
How do you treat low ventilation/perfusion ratio
How do you treat intrapulmonary shunt
How do you treat a diffusion defect
How do you treat low barametric pressure
Descend to lower altitude
How do you treat low inspired oxygen (less than 21%)
What are the values present when ventilation failure is imminent?
PaCO2 of 50-55 and rising
PH of 7.25 or less
What are some alternatives instead of mechanical ventilation
Hi-flow oxygen, NPPV
Intubation without ventilation is common or uncommon?
What size et tube must be used to conclude that IPPV is NOT needed?
7 mm or larger
What are some ethical considerations that we must ask ourselves before intubation?
Do they really want this? Do they have a living will? What is their advance directive?
What is a contraindication of mechanical ventilation?
If it's use is medically pointless, futile and NO chance exists that this treatment would extend this person's quality of life in a meaningful way.
Explain 'elastic recoil pressure' 's place in the motion equation
The volume of air in the lungs depends on this pressure which is the result of alveolar tension on the volume within the alveoli
What phase variable begins inspiration
List two other names for pressure-limited ventilation
pressure-targeted ventilation, pressure controlled
T or F. In a pressure-controlled breath, tidal volume is constant.
What are the two most common patient triggering variables?
Pressure and flow
What happens in most ICU ventilators if the pressure limit is reached?
1. Inspiration ends, tidal volume reduced
2. An alarm sounds
Flow triggering is popular because
It causes less work of breathing for the patient
T or F. Inflation hold increases inspiratory time?
Which ventilator uses a brief negative pressure at the beginning of the expiratory phase?
On a pressure-time wave form, the curve during the expiratory phase does not return to the baseline rapidly, like it should, but eventually makes it. What could be the problem?
an obstruction in the expiratory line
Inspiratory flow ends and exhalation begins when a preset time has elapsed. This is called?
The pressure-time waveform does not change during inspiration but the volume-time waveform changes with lung characteristics. This is called?
Indications of NPPV
RR of 25 or less
PH of 7.30-.7.35, 45-60 mm Hg
Using accessory muscles (mod-severe dyspnea)
Although manipulation of a mechanical ventilator can be helpful in reducing intracranial pressure, this procedure has NOT been shown to improve long-term outcomes. T or F.
When would opting not to provide mechanical ventilation to an apneic patient be appropriate?
When the patient has a living will or a surrogate that states he or she does not wish to be intubated and ventilated. Another possibility is in an advanced stage of a terminal illness.
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