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muscle pressure

produced by the action of the respiratory muscles

ventilation pressure

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

volume ventilation

the operator sets the volume for delivery to the patient

volume ventilation is also called

volume targeted, volume limited, volume control

pressure ventilation

the operator sets the pressure for delivery to the patient

pressure ventilation is also called

Pressure targeted, pressure limited, pressure control

control variable

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

Phase Variables

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

triggering mechanism

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

define expiration

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.

define neep

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

define CPAP

Continuous positive airway pressure that helps improve oxygenation to a spontaneous breathing patient.

define PEEP

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

hypercapnia, hypoxic

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?


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)

N: 100
C: 40 or less

What are normal and critical values of VC

N: 65-75
C: 10 to 15

What are normal and critical values of Vt

N: 5-8
C: 5 or less

What are normal and critical values of F (frequency)

N: 12-20
C: 35 or more

What are normal and critical values of FEV1

N: 50-60
C: 10 or less

What are normal and critical values of PEFR

N: 350-600
C: 75-100

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

trigger variable

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?

Cardiopulmonary Venturi

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?

time cycling

The pressure-time waveform does not change during inspiration but the volume-time waveform changes with lung characteristics. This is called?

pressure-controlled ventilation

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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