Term
| Recognize the 4 basic functions / (categories) used for classifying ventilators |
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Definition
| Input power, Power transmission and conversion, control system, Output (pressure, volume and flow waveforms) |
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Term
| Define the CMV mode of ventilation |
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Definition
| continuous mandatory ventilation. the clinical attempt is to make every breath a mandatory one vs. IMV intent is to partition ventilatory support between mandatory and spontaneous breaths. CMV is a method of full ventilatory support. (IMV is partial ventilatory support) CMV means spontaneous breaths are not allowed |
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Term
| Describe the action of the volume, flow, and pressure waveforms during volume control ventilation |
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Definition
| If the ventilator controls volume, the volume and flow waveforms will remain consistent, but pressure will vary with changes in respiratory mechanics. to qualify as a true volume controller, a ventilator must measure volume and use this signal to control the volume waveform. volume can be controlled directly by the displacement of a device such as a piston or bellows. volume can be controlled indirectly by controlling flow. this follows from the fact that volume and flow are inverse functions of time. |
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Term
| How do you calculate compressible/tubing loss? i.e. measured volume 200; meausured pressure 70; also measured volume 800, peak pressure 25, tubing compliance 2.86; also calculate the corrected tidal volume |
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Definition
| Compliance = Volume/Pressure; 200/70 = 2.86 - - - - compressible volume = peak pressure x tubing compliance; 25x2.86 = 71.5 - - - corrected tidal volume = compressible volume is subtracted from measured volume; 800 - 72 = 728 mL |
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Term
| What is the drive mechanism |
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Definition
| the system used by the vent to transmit or convert the input power (power source like electrical or pneumatic) to useful ventilatory work. drive mechanisms include pistone, bellows, reducing valves, and pneumatic circuits. |
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Term
| What are 4 primary variables a ventilator can control |
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Definition
| volume, pressure, flow and time |
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Term
| What are the trigger variables used by a ventilator to start ventilation |
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Definition
| It is the variable that determines the start of inspiration. Pressure, volume, flow, or time. Most use time or pressure. |
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Term
| Describe the piston drive mechanism |
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Definition
| electrically driven piston, inspiratory one-way valve, used to generate a pressure gradient to drive a vent |
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Term
| Describe the bellows drive mechanism |
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Definition
| a bellows may be compressed by a spring, weight, or gas pressure if in a sealed chamber. one-way valve admits gas to the bellows, expanding it. when compressed, the one-way valve closes, causing gas delivery to the patient. |
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Term
| Describe a reducing valve drive mechanism |
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Definition
| it can be used to drive a ventilator providing enough pressure gradient to cause ventilation i.e. Bennett PR-2 |
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Term
| Describe microprocessor-controlled pneumatic drive mechanism |
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Definition
| current generation vents use programmed algorithms in the microprocessors to open and close the solenoid valves to mimic virtually any flow or pressure wave pattern. |
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Term
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Definition
| Continuous mandatory ventilation, the ventilator determines when and how much gas is given. The vent initiates ventilation, and the inspiratory phase is terminated based on volume, pressure, time or flow. The patient is unable to initiate inspiration. The control variable may be pressure, volume or flow; the trigger variable is time; the limit variable may be pressure, volume or flow; cycle variable may be time, pressure, volume, or flow; no conditional variable. |
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Term
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Definition
| Assist Control- allows the patient to initiate a breath. has a sensitivity or assist system that responds to the patient's inspiratory effort but if the patient fails to initiate a breath, the vent functions automatically as in CMV via a backup rate. When pressure falls below baseline pressure, the ent initiates inspiration. It can be pressure, volume or flow triggered. control variables may be pressure, volume, or flow. trigger variables may be time, pressure, volume, or flow; limit variables may be pressure, volume or flow; cycle variables may be time, pressure, volume or flow |
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Term
| Define AMV mode of ventilation |
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Definition
| Assisted Mechanical Ventilation - variation of A/C. There is no set respiratory rate, all breaths are patient triggered |
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Term
| Define SIMV mode of ventilation |
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Definition
| Synchronized, intermittent, mandatory ventilation. allows the patient to breathe spontaneously between ventilator breaths. when spontaneously breathing, the patient determines their own rate and tidal volume.the vent will provide support should the patient fail to breathe. |
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Term
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Definition
| continuous positive airway pressure - application of continuous positive pressure during both inspiration and expiration during spontaneous ventilation. CPAP pressures increase the FRC, improving gas exchange. |
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Term
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Definition
| Pressure Supported Ventilation - provides pressure augmentation during spontaneous breathing. trigger may be pressure, flow, or volume triggered...once triggered, a set pressure is delivered above baseline to augment the patient's spontaneous tidal volume and the breath ends when the delivered flow drops to a percentage of peak inspiratory flow |
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Term
| Differentiate between a ventilator’s “Input Alarms” and its “Output Alarms” |
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Definition
| Input alarms are either loss of pneumatic, or loss of electrical power. Output alarms can be subdivided to pressure, volume, flow, time, inspiratory, and expiratory gas |
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Term
| Monahgan 225/SIMV ventilator’s control circuit and identify its cycle variables |
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Definition
| the control circuit is fluid controlled, where various fluidic elements are used for regulation of control, phase, and output variables as well as alarms. The cycle variables are pressure, volume and time. |
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Term
| Recognize those modes of ventilation where pressure is a control variable |
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Definition
| During CPAP (Bear 1, 2, and 3) and Pressure Support (Bear 3), pressure is measured and used as a feedack signal to control the ventilator output via the demand valves. During these modes, inspiratory flow varies to maintain the set CPAP or pressure support level. |
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Term
| Discuss different control interactions |
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Definition
| tidal volume and flow rate controls can have a profound effect upon inspiratory time. as tidal volume is increased, inspiratory time is also increased. a decrease in peak flow rate control will have the same effect. if I:E ratios of 1:2 or greater are desired, adjustment of tidal volume, rate, and peak flows must be manipulated correctly |
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Term
| Identify those variables controlled by a ventilator as stated by the Equation of Motion |
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Definition
| Pressure Volume and Flow The equation of motion is expressed in terms of compliance where compliance equals volume/pressure. Pressure, volume and flow are all changeable variables measured relative to their baseline or end expiratory values. |
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Term
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Definition
| Pressure support ventilation - form of continuous spontaneous ventilation (CSV) that assists the patient's inspiratory efforts. unloads wob and in a maximized capacity, will assume all the wob. |
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Term
| Identify those parameters that can serve as cycle variables |
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Definition
| pressure, volume, flow, time, patient |
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Term
| Discuss how alveolar expansion occurs during spontaneous ventilation |
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Definition
| AT end-exhalation, intra-pleural pressure is slightly negative. alveolar, mouth, and body surface pressures are zero. The diaphragm contracts and descends into the abdominal cavity, decreasing intrapleural pressure once negative, alveolar pressure becomes negative as well. |
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Term
| Discuss how alveolar expansion occurs during negative pressure ventilation (NPV) |
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Definition
| negative pressure ventilation decreases pleural pressure during inspiration by exposing the chest to subatmospheric pressures. Negative pressure at the body surface is transmitted first to the pleural space and then to the alveoli. the airway opening remains exposed to atmospheric pressure, a transairway pressure gradient is created. gas flows from the relatively high pressure at airway opening to relatively low pressure in alveoli. alveolar expansion is determined by the magnitude of teh transpulmonary pressure gradient. |
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Term
| Discuss how alveolar expansion occurs during positive pressure ventilation (PPV) |
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Definition
| opposite of spontaneous and NPV, gas flows into the lungs because pressure at the airway opening is positive and alveolar pressure is initially zero or less positive. because alveolar pressure is greater than pleural pressure during PPV, positive pressure is transmitted from the alveoli to the pleural space. |
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Term
| Calculate “Static Compliance (CLung) |
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Definition
| Exhaled Tidal Volume/(Plateau Pressure - EEP) - EEP is end-expiratory pressure, the baseline from which the patient breathes |
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Term
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Definition
| Raw = (PIP - Pplateau)/flow OR Raw = Pta/flow - Example; Raw = (40-25 cm H20)/1(L/sec) = 15 cm H20 L/sec |
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Term
| Define plateau pressure and its role in calculating static compliance |
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Definition
| plateau pressure is a pressure measurement taken during positive pressure ventilation after a breath has been delivered to the patient and before exhalation has begun. A conditin of no flow exists reflecting the pressure in the lungs and patient circuit. |
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Term
| Recognize the differences between transairway, transthoracic, transpulmonary, and transrespiratory pressures. |
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Definition
| Transairway Pressure is pressure gradient between the airway opening and the alveolus. Transthoracic pressure is pressure difference between the alveolar space or lung and the body's surface. Transpulmonary pressure is the pressure difference between teh alveolus and the pleural space. Transrespiratory pressure is the pressure gradient between the airway opening and the body surface. |
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Term
| Identify the triggering variable for the A/C mode of ventilation |
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Definition
| patient or time triggered |
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Term
| Appropriately adjust tidal volume or rate given a set of ABG values and the patient’s IBW |
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Definition
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Term
| Select the proper inspiratory flow rate when setting up a ventilator |
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Definition
| the flow setting estimates the delivered flow of inspired gas. In general it is best to get the air into the lungs as quickly as possible and set the flow based on the patient's lung condition. An I:E ratio of 1:2 (usually about 1:4) is recommended and can be achieved with an initial peak flow setting of about 60 L/min (range of 40 - 80 L/min) |
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Term
| Recognize the primary advantage and disadvantage of volume ventilation (VV) |
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Definition
| it guarantees a specific volume delivery and Ve, regardless of changes in lung compliance and resistance or patient effort. It is used when the goal is to maintain a certain level of PaCO2 |
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Term
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Definition
| pressure control, inverse ratio ventilation. occasionally T1 is set longer than Te during PC-CMV; this is the opposite of the process that occurs during normal breathing. A longer T1 provides better oxygenation to some patients by increasing Paw. |
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Term
| Identify the flow pattern most commonly used by practitioners when initiating mechanical ventilation |
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Definition
| Rectangle (constant) flow pattern |
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Term
| Describe the difference between an “Open Loop” (Unintelligent) system and a “Closed Loop (Intelligent) system |
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Definition
| open loop is a ventilator that is not microprocessor controlled. closed systems compare the set control variable to the measured control variable - an example is the mode of ventilation called mandatory minute ventilation |
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Term
| Identify the “p.s.i.” requirement for a pneumatic ventilator |
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Definition
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Term
| Identify and define the 4 phase variables (i.e. trigger, limit, and cycle variable) associated with a mechanical ventilation |
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Definition
| trigger variable begins inspiration, limit variable limits inspiratory factors, the cycle variable ends inspiration |
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Term
| Describe an “expiratory retard” and the type of breathing it mimics |
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Definition
| spontaneously breathing individuals with a disease that leads to early airway closure (emphysema) have a prolonged expiratory phase and use pursed-lip breathing - to mimic this, the ventilator adds a degree of resistance to exhalation called expiratory retard. |
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Term
| Identify those indicators associated with the presence of ARF |
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Definition
| Hypoxic Lung Failure (Type I) - Vent/Perfusion mismatch, diffusion defect, right-to-left shunt, alveolar hypoventilation, decreased inspired oxygen. Respiratory activity is inadequate or insufficient to maintain adequate oxygen uptake and carbon dioxide clearance. Inability of Pt to maintain arterial PaO2, PaCO2, an pH acceptable levels. PaO2 <70 on >.6Fio2; PaCo2 >50 and climbing; pH 7.25 and lower |
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Term
| Recognize the causes of “hypoxic lung failure” |
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Definition
| often a result of severe ventilation/perfusion (V/Q) mismatching and can also occur with diffusion defects, right-to-left shunting, alveolar hypoventilation, aging, and inadequate inspired oxygen. |
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Term
| Recognize ventilation, oxygenation, and ventilatory mechanics criteria indicating the need for mechanical ventilatory support. |
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Definition
| VENTILATION - pH, PaCo2, Vd/Vt - critical values are pH less than 7.25, paco2 is > 55 and rising, Vd/vt (deadspace) is >0.6; OXYGENATION - Pa)2, P(A-a)O2, P02 (PaO2/P/A02), PaO2/FiO2; PaO2 <70 (on O2> .60), P(A-a)o2 > 450 (onO2); Po2 (Pa02/PA02) <.15; PaO2/Fi02 <200 |
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Term
| Calculate the amount of gas available for gas exchange given a tidal volume and VT / VD |
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Definition
| a patient with a tidal volume of 1000 mL and a Vd/Vt of .6, for each breath taken only 40% contribute to alveolar gas exchange and 60% goes to areas of the pulmonary system that are not in contact with pulmonary capillary bed (400 mL of the 1000 mL is in contact with pulmonary blood flow |
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Term
| calculate the desired minute ventilation (VE) given: (1) an actual tidal volume (VT), (2) an actual PaCO2, and (3) desired PaCO |
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Definition
| known PaCo2 x known Ve = Desired PaCO2 x desired Ve |
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Term
| Identify common causes of respiratory and metabolic alkalosis |
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Definition
| respiratory alkalosis - hypoxia with compensatory hyperventilation, parenchymal lung disease, medications (salicylate, xanthines, analeptics), mechanical ventilation, central nervous system disorders (meningitis, encephalitis, head trauma), anxiety, metabolic problems ( sepsis, heaptic disease) - metabolic alkalosis - loss of gastric fluid and stomach acid, acid loss in the urine, acid shift into the cells, lactate, acetate or citrate administration, excessive bicarbonate loads |
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Term
| Describe the beneficial effects of a “descending” waveform |
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Definition
| decreases a patient's WOB |
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Term
| ) Identify those factors responsible for increasing mean airway pressure (MAP) |
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Definition
| respiratory rate, tidal volume, inspiratory time, inspiratory pause, expiratory time, I:E ratio, peak pressure, baseline pressure (PEEP/CPAP), and inspiratory flow waveform |
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Term
| ) Identify those factors responsible for increasing mean airway pressure (MAP) |
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Definition
| respiratory rate, tidal volume, inspiratory time, inspiratory pause, expiratory time, I:E ratio, peak pressure, baseline pressure (PEEP/CPAP), and inspiratory flow waveform |
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Term
| Discuss the adverse effects of an increased I:E Ratio on mean airway pressure (MAP) and the cardiovascular system |
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Definition
| increased mean airway pressure, decreases in cardiac output may result in overall decrease in tissue oxygenation |
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Term
| Recognize the physiological goals of artificial ventilation. |
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Definition
| maintain adequate alveolar ventilation and oxygen delivery, restore acid-base balance, and reduce the work of breathing with minimum harmful side effects and complications, increasing or maintaining lung volume with PEEP/CPAP for promotion, improvement, or maintenance of lung improvement |
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Term
| Discuss the different ventilatory management strategies for specific pathological disorders (i.e. Congestive heart failure and neuromuscular disorders) |
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Definition
| noninvasive ventilation - reduce the morbidity and possibly the mortality of both hypoxemic and hypercarbic respiratory failure, i.e. COPD, cardiogenic pulmonary edema, acute asthma (use is controversial), acute hypoxemic and nonhypercapnic respiratory failure is also controversial, helpful for chronic hypercapnic respiratory failure not due to COPD; invasive for ARDS,hyperventilation acutely for short periods helpful for increased ICP; obstructive lung disease |
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Term
| Describe “permissive hypercapnia” |
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Definition
| In patients with ALI and ARDS a Vt of 6 or less may be required to maintain Pplat of less than 30 cmH2O. reductions in Vt may be compensated for by increasing the ventilator rate. The RR is increased and the decision may be made to allow PaCo2 to increase an Ph to decrease |
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Term
| Calculate the minute ventilation (VE) given a tidal volume (VT) and Frequency OR calculate the VT given a VE and Frequency |
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Definition
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Term
| Discuss the differences between Pressure Controlled Ventilation and Volume Controlled Ventilation. Describe situations where one type of ventilation is preferred over another |
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Definition
| in the past pressure control was used primarily for short-term need such as postop care or er care. now it is used in the form of PSV or PCV. can be used alone or with SIMV. in the use of pressure control ventilation, as compliance and resistance change, volume delivery varies. with volume controlled ventilation, as compliance decreases or resistance incresees, pressure increases and volume remains the same. |
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Term
| Recognize the type of supplementary equipment required at the bedside of a patient receiving mechanical ventilation |
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Definition
| an extra ET tube or trach tube, equipment needed to replace the airway, manual resusitator with oxygen supply, suction device, sterile water, sterile gloves, peep valves, crash cart, cardiac monitor, chest tubes, aortic baloon pump, cooling blanket, |
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Term
| Identify the proper Inspiratory Flow Rate, Inspiratory Time and I:E Ratio normally selected when initiating mechanical ventilation |
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Definition
| for most adults, inspiratory time of 1 second resulting in 1:2; initial peak flow of 60 l/min range of 40 - 80 down ramp or sqare. |
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Term
| Define refractory hypoxemia |
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Definition
| when a pt pao2 cannot be maintained above 50 - 60 mm Hg wiht FIo2 of .40 to .50. indication for ppv with PEEP or CPAP, because ppv with either of these modalities improves oxyenation by decreasing physiologic shunting |
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Term
| Recognize and apply the criteria indicating the readiness for “weaning” |
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Definition
| VC >15 mL/kg (IBW); VE <10 to 15 L/min; Vt >4-6 mL/kg (IBW); f <35 breaths per min; f/Vt <60 to 105 breaths/min/L; Pimax < -20 to -30 cm H2O; P0.1 >-6 cm H2O; WOB <0.8 J/L; oxygen cost of breathing <15% of total VO2; Dynamic compliance >25 mL/cm H2O; Vd/Vt <0.6; CROP index >13 mL/breaths/min; PaO2 >/= 60 mmHg; PEEP 250 mmHg; PaO2/PAO2 >.47; P(A-a)O2 >350 mmHg (Fio2 = 1); % Qs/Qt <20%-30% |
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Term
| Discuss and apply the concepts related to the different methods of weaning (i.e. T-tube, IMV/SIMV, PSV and single daily SBT |
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Definition
| After careful evaluation, pt in stable condition who have been treated with a ventilator for less than 72 hours and who have a good spontaneous RR, minute ventilation, MIP and f/V, may undergo a spontaneous breathing trial (SBT) on the vent or T-tube for 30-120 minutes. those on vent support for more than 72 hrs and with marginal oxygenation, ventilatory, cardiovascular, or medical status may need a prolonged period of weaning by SBTs interspersed with SIMV and PSV. Oldest weaning method is spontaneous breathing T-tube trial. one or more daily SBTs with a T-tube resulted in three times faster extubation than with SIMV and two times faster than PSV. |
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Term
| Recognize the different physiological criteria indicating the need for mechanical ventilatory support |
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Definition
| PaCO2 >55; pH <7.2; Vt <5 ml/kg; RR>35; VC <10ml/kg; MMV <2xVE; VE >10; VD/VT% >0.6; P(A-a)O2 on 100% O2 >350; PaO2/Fio2 <200 |
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Term
| Differentiate between Acute Hypoxemic Respiratory Failure (Type I) and Acute Hypercapnic Respiratory Failure (Type II) |
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Definition
| Acute Hypoxemic Respiratory Failure (Type I)= V/Q mismatch; shunt; alveolar hypoventilation; diffusion impairment; perfusion/diffusion impairment; decreased inspired O2; venous admixture. Acute Hypercapnic Respiratory Failure (Type II)= AKA pump failure ventilatory failure - elevated PaCO2 creating an uncompensated respiratory acidosis. |
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Term
| Recognize the FIO2 and PaO2 where PEEP is indicated |
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Definition
| PEEP can correct refractory hypoxemia which exists when the PaO2 cannot be maintained above 50 - 60 mmHg with an Fio2 of .4 - .5 or more. |
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