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mech vent ch 46
| Question | Answer |
|---|---|
| which types of ventilation is alveolar expansion during inspiration due to a decrease in pleural pressure? | spontaneous ventilation/ negative pressure ventilation |
| describe in detail negative pressure ventilation (NVP) | pressure decreases, volume increases, and chest wall expands |
| in which types of ventilation is alveolar expansion during inspiration due to an increase in alveolar pressure? | positive pressure (bagging patient) |
| in which types of ventilation can pleural pressure become positive during inspiration? | positive pressure ventilation |
| which conditions are associated with a lack of response to increase fio2 in patients receiving positive pressure ventilation? | Shunt |
| what strategies are useful in management of shunt? | Lung expansion with peep |
| list the benefits associated with administration of positive end expiratory pressure (PEEP) or continuous positive airway pressure (CPAP) | |
| what values are considered a normal spontaneous tidal volume in ml/kg? give example | 5-7ml/kg if patient is 60kg then multiply 60*5=300 and 60*7=420kg |
| what is the recommended tidal volume for mechanical ventilation in ml/kg? | 5-7 or 4-8 with resp. failure |
| which condition may require high mechanical respiratory rates? | ARDS |
| explain the increase v/q ratio when excessive positive end expiratory pressure (PEEP) is used. | if you add too much peep it diminishes perfusion due to over inflation by redirecting blood flow away from good alveoli |
| what are the consequences of decreased resistance and compliance? | needs more pressure to ventilate, less volume, less inspiratory and expiratory time, will deflate more quickly, increase RR |
| Identify at least five methods mean airway pressure may be increased | anything that increases pressure: increase pressure, increase peep, increase I time and an inspiratory pause. |
| on what does volume delivered depend during pressure-targeted modes of ventilator support? | pressure gradient, time, flow |
| describe in detail pressure limited modes of ventilator support. | inspiratory flow varies with patient effort and lung mechanics, volume delivered at given pressure must decrease as compliance falls, active effort by the patient against inspiration will decrease delivered volume |
| the volume delivered by a pressure limited ventilator will increase or decrease under which conditions? | lung compliance decreased then volume with decrease and if increase then volume will increase as well. if resistance increases the volume decreases and if the resistance decreases the volume will increase |
| describe safe settings for a lung recruitment maneuver as they relate to pressure and time | pressure up to 50 cmh20, pressure applied for 1 to 3 minutes |
| the magnitude of WOB pt. depends on which factors? | compliance, resistance, ventilator drive, trigger sensitivity, peak flow, cycling coordination, Vt |
| rank the modes of ventilation from greatest to least as they relate to a patients work of breathing | CMV (AC) - 100% WOB, SIMV+PS, SIMV, PS, CPAP 0% |
| when bedside works of breathing measures are unavailable, you should adjust the level of pressure-supported ventilation (PSV) to: | Spontaneous rate 15-25/min., Vt 5-8ml/kg |
| What level of plateau pressure increases the likelihood of causing lung injury? | PP of 28cmh2o or greater likelihood of injury |
| primary indications for using positive end expiratory pressure (PEEP) in conjunction with mechanical ventilation include? | improve oxygenation in patients with refractory hypoxemia |
| identify the indications and contraindications for positive end expiratory pressure (PEEP) most indicated? | indication- improve oxygenation in patients with refractory hypoxemia, contraindications- tension pneumo, unilateral lung disease |
| identify the beneficial physiological effects of positive end expiratory pressure (PEEP) | restored FRC avoids derecruitment, decreased shunt fraction, increased lung compliance, decreased WOB, increased PaO2 for a given FIO2 |
| identify the detrimental effects of positive end expiratory pressure (PEEP) | increased pulmonary vascular resistance, potential decrease in venous return and cardiac output, decreased renal and portal blood flow, increased ICP, increased dead space |
| what are the benefits of high inspiratory flows during positive pressure | reduced air trapping |
| describe the physiological effects of adding a volume limited inflation hold to mandatory breaths | decreased paco2, increased inspiratory time, decreased VD/VT |
| identify the volume controlled (VC) modes of mechanical ventilation | VC-CMV continuous mandatory ventilation (AC, VC-IMV intermittent mandatory ventilation |
| Which mode of support provides all the patients minute ventilation as mandatory volume controlled breaths | CMV, all breaths are mandatory and can be volume or pressure targeted. breaths also can be patient triggered or time triggered. when patient triggered, its also assist/control. When time triggered mode is called controlled vent or control mode. |
| In which mode does the clinician have the most control over the patients breath? | CMV (patient has the least control) |
| Identify the modes of ventilator support that would result in the highest mean airway pressure | any mode that the machine controls the breath (VC-CMV, VC-AC) |
| In which mode of ventilator support is muscle atrophy most likely to occur | CMV because the patient is relying on machine for breaths so not using muscles |
| Identify key causes of patient-ventilator asynchrony and increased work of breathing during pressure-triggered volume-controlled continuous mandatory ventilation. | when not sensitive enough VC-CMV (Pressure Support with be more synchronized) |
| Inspection of the airway pressure waveform of a patient receiving volume-controlled continuous mandatory ventilation assist control with constant flow reveals a large dip or drop in pressure at the beginning of inspiration. Which problem is most likely? | patient is trying to take in more volume than being delivered and pressure will drop. |
| What actions can you use to decrease compressed volume loss during mechanical ventilation? | add humidity, decrease volume, anything to reduce ventilator circuit or compliance of circuit. |
| After accounting for the compressed volume loss on a stable adult patient receiving vc-cmv at a preset volume of 700ml, you still note a 150ml difference between the expected and the actual delivered volume. What is causing problem? | there is leak |
| which modes of ventilatory support are used to help decrease airway and alveolar pressure | PC-CMV (PRessure modes |
| Describe permissive hypercapnia | when CO2 is allowed to increased without letting the ph fall below 7.2 |
| What mode of pressure controlled ventilation is designed to prevent alveoli with short time constants from collapsing, thereby improving oxygenation? | APRV which created auto peep |
| A patient is switched from PC-CMV with PEEP to PC-IRV shows a good improvement in PaO2 but a decrease in tissue oxygenation. What would best explain this observation? | PEEP too high |
| In Which mode of ventilatory support does the patient breathe spontaneously at an elevated airway pressure, with short, intermittent decreases in pressure to a lower level | APRV |
| What does pressure supported ventilation consist of? | pressure support vent. aka pressure support is a spont. mode of ventilation. Patient initiates every breath and the vent delivers support w/ the preset pressure value. With support from vent, the patient also regulates his own RR and Vt |
| What are 2 primary used for pressure support ventilation (PSV)? | augmenting patients spontaneous Vt, overcoming the imposed work of breathing |
| For a patient with respiratory insufficiency, pressure-supported ventilation (PSV) has what advantages over spontaneous breathing? | expect increase muscle activity |
| What spontaneous pressure controlled breath mode allows separate regulation of the inspiratory and expiratory breathing? | Bilevel positive airway pressure (Bipap) |
| Which modes of ventilatory support combine the advantages of pressure-controlled and volume-controlled ventilation. | PRVC (pressure regulated volume control), this is a pressure control mode, but adds a target Vt, so that the inspiratory pressure changes breath-by-breath up to a set point in order to maintain a stable Vt. |
| the delivered Vt is greater than the preset minimum Vt | |
| What are some physiological advantages of volume-assured pressure-supported ventilation | improved patient-ventilator synchrony and decreased work of breathing |
| What factor primarily determines the effect of positive pressure ventilation on the cardiac output? | effect of PPV on the circulatory system depends primarily on mean pleural pressure and cardiovascular status |
| Identify the potential effects of positive pressure ventilation on the cardiovascular system | decreas CO and decread level of arterial pressure |
| Assuming a constant rate of breathing, what effect do inspiratory/expiratory ratios (I:E) have on diastolic pressure | is equivalent without the marked depression in CO and any greater than 1:1 pg 1055 |
| Potential effects of hyperventilation on the central nervous system include: | increased cerebral vascular resistance (CVR), Increased intracranial pressure (ICP) |
| Hyperventilation should generally be avoided during mechanical ventilatory support. Exceptions to this rule include? | Failure of other methods to reduce intracranial pressure |
| Which gastrointestinal condition are commonly associated with long term positive pressure ventilation? | bleeding, ulceration |
| What is traumatic injury to lung tissue caused by excessive pressure? | high ventilation pressure has long been associated with barotrauma |
| What I the term used to describe the lung injury associated with the use of low tidal volumes? | Atelectrauma |
| Types of damage associated with pulmonary barotrauma include: | Pneumothorax, pneumomediastinum, pneumopericardium, and subcutaneous emphysema |
| Which term describes the lung injury associated with the release of prostanoids | Biotrauma |
| Physical assessment indicating the presence of a tension pneumothorax includes: | unequal chest excursion, hyperresonance , absent breath sounds |
| describe lung conditions which would be most prone to air-trapping | one with high resistance and high compliance |
| What factors contribute to the development of auto peep | decreased pulmonary vascular resistance |
| What patients are at greater risk for auto peep? | those with high airway resistance, those with high expiratory flow resistance |
| Ventilatory support strategies likely to result in auto peep include: | CMV, IRV, low inspiratory flows, not low rate IMV |
| The increased work of breathing associated with auto peep during mechanical ventilation is due to: | hyperinflation or impaired contractility of the diaphragm, large alveolar pressure drops required to trigger breaths |
| Which level if FIO2 and what time of exposure have been associated with oxygen toxicity? | FIO2 of 60% or more for longer than 24-48 hours |
| Which groups of patients are primarily affected by ventilator-associated pneumonia? | infants, adults older that 65, immunosuppressed, thoracoabdominal surgery, depressed sensorium |
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