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56 Cards in this Set
- Front
- Back
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What is minute ventilation?
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Product of tidal volume (VT) and ventilatory rate (f)
VE=VT x F |
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What is normal spontaneous tidal volume?
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5 to 7 mL/kg
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What is the accepted tidal volume for ventilated patients?
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5 to 8 mL/kg for ARDS
8 to 12 mL/kg for COPD 10 to 12 mL/kg for normal lung 12 to 15 mL/kg neuromuscular disease |
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What is the ventilatory rate dependant on?
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Patient's status
Postoperative:10 to 12 breath Higher rate for increased intracranial pressure(ICP)and metabolic acidosis. Lower rate for COPD and acute asthma exacerbation to avoid air trapping. |
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What causes respiratory acidosis?
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Hypoventilation causes respiratory acidosis.
Hyperventilation causes respiratory alkalosis. |
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What are some of the benefits of Appropriate PEEP?
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Restored FRC, alveolar recruitment.
Decreased shunt fraction. Increased lung compliance. Decreased work of breathing. Increased Pao2 for a given FIO2. |
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What are some of the detrimental effects of Inappropriate of PEEP?
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Increased incidence of pulmonary barotrauma.
Potential decrease in venous return and cardiac output. Increased work of breathing (with overdistension) Increased pulmonary vascular resistance. Increased ICP. Decreased renal and portal blood flow. Increased dead space . Increased mean airway pressure. |
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What is the calulation of rapid shallowing breathing index ?
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An alternative to measuring the work of breathing at the bedside, RSBI,which is :
RSBI=spontaneous respiratory rate f/Vt (tidal volume) |
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What is the predictor of sucess for liveration from mechanical ventilation?
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RSBI less than 105.
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What is the main objective of mechanical ventilation?
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Minute ventilation acequate to provide the patient with adequate alveolar ventilation.
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What are supplimental oxygen and PEEP for?
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To provide adequate arterial oxygenation.
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What is peak pressure?
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The result of the pressure required to overcome system resistance and elastance.
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What are factors that increase airway resistance?
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Airway edema, bronchospasms and secretions.
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What are some ways of decreasing airway resistance?
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Assure adequate humidity, bronchial hygine(suctioning, airway care) and administration of bronchodilators and antiinflammatory drugs.
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What are the factors that increase the pressure needed to inflate the lung and overcome decreased compliance?
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Alveolar and interstitial edema, fibrosis, and chest wall restriction.
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What can the therapist do for alveolar and interstitial edema,fibrosis and chest wall restriction?
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Rely on medical staff to prescribve drugs that decrease plumonary vascular load, such as pulmonary vasodilators and diuretics, and drugs that increase cardiac contractility in the case of cardiogenic pulmonarhy edema. Little the therapist can do if it's pulmonary fibrosis. Chest wall constriction only if it's tight bandages the issue.
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How is mean airway pressure increased and what does this do?
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Mean airway pressure is increased by an increase in inspiratory time, tidal volume, respiratory rate, PEEP. or PIP. Increases are associated with improvements in Pao2; however increase reduces venous return and my reduce cardiac output in compromised patients.
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What is refactory hypoxemia?
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Exists when Pao2 cannot be maintained above 50 to 60mmHg with an FIO2 of 0.40 to 0.50 or greater. This situation is an indication for PPV with PEEP or CPAP, because PPV with either of these modalities improves oxygenation by decreasing physiological shunting.
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What helps determine the cause of hypoxemia?
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An increase in FIO2 helps determinne the cause of hypoxemia.
Hypoxemia responsive to an increase in FIO2 is likely caused by a low V/Q ratio. Hypoxemia unresponsive to an increase in FIO2 is likely caused by a diffusion defect or shunt. |
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What determines arterial PCO2?
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Alveolar ventilation and carbon dioxide production.
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What does mechanical ventilation with positive pressure do?
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Increases dead space and decreases V/Q ratio.
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What are the most common reasons for intiating mechanical ventilatory support?
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Acute respiratory failure,acute exacerbation of COPD,coma, and neuromuscular disease.
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What are the clinical manifestations of acute respiratory failure ?
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Restlessness, confusion,anxiety,diaphoresis, accessory muscle use, dyspnea, tachypnea, and tachycardia.
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What are the physiologic markers associated with the need for mechanical ventilation?
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Elevated respiratory rate(f>30breaths/min), a decrease in spontaneous tidal volume(Vt>300mL), an elevated rapid shallow breathing index(RSBI Vt/f>105),a decline in vital capacity(<15 to 20mL/kg, or 1.0L),a decline in inspiratory force(maximum inspiratory pressure>-20mmHg),inadequate arterial oxygenation(Pao2<60mmHg,Sao2<90%)while patient is receiving supplemental oxygen, and the development of respiratory acidosis(PaCo2>45-50mmHg,pH<7.25).
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What are the four primary reasons for initiation of mechanical ventilatory support?
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1. Apnea
2. Acute ventilatory failure 3. Impending ventilatory failure 4. Severe oxygenation problems |
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What are the physiological goals of Ventilatory Support?
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To support or manipulate gas exchange.
1. Alveolar ventilation(Paco2 and pH) 2. Arterial oxygenation(Pao2,Sao2,Spo2,Cao2, and Do2.) To increase lung volume 1. End-inspiratory and end-expiratory lung inflation. 2. Functional residual capacity (FRC) To reduce or manipulate the work of breathing To minimize cardiovascular impairment. |
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What are the Clinical Objectives of Ventilatory Support?
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To reverse hypoxemia
To reverse acute respiratory acidosis. To relieve respiratory distress. To prevent or reverse atelectasis. To reverse ventilatory muscle fatigue. To allow sedation and neuromuscular blockade. To decrease systemic or myocardial oxygen consumption. To maintain or improve cardiac output. To reduced ICP. To stabilize the chest. |
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Why do patients with normal lung function need mechanical ventilatory support?
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Apnea or severe hypoventilation caused by a nonpulmonary problem.
Examples:Recovery from major abdominal or thoracic surgery, sedative or narcotic drug overdose(without pulmonary aspiration), high spinal cord injury, cardiac arrest after myocardial infarction, electric shock,or related trauma,neuromuscular disease, head trauma, and certain central nervous system(CNS) disorders. |
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Patients with normal compliance,airway resistance , and lung function can be easily ventilated with what mode?
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Volume ventilation in the assist-control or syncronous intermittent mandatory ventilation mode. (SIMV).
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How do you set a ventilator in the SIMV mode for a patient with normal lung compliance?
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Tidal volume 10-12mL/kg of ideal body weight(IBW)
Machine rate of 10-12 breaths/min. Larger tidal volume(12-15mL/kg and a slower rate(6-10 breaths/min) may be used in the SIMV mode if there are concerns about maintaining lung volume or satisfying patients air hunger. Inspiratory flow in the range of 60 to 80 L/min generally is used and results in a ratio of (I:E) 1:2 or better. Low to moderate inspired oxygen concentration usually is sufficient for adequate arterial oxygenation . Care is taken to ensure a plateau pressue of 30cmH2O ro less, if possible. Small tidal volume (<7mL/kg ) is avoided in patients with normal lung function, because atelectasis can develop. |
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Ventilator initiation includes what choices?
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Choices of mode.
Tidal Volume Rate FIO2 PEEP |
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What do you maintain plateau pressure at and why?
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Less than 30 cm H2O.
To prevent ventilator-induced lung injury. |
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When is negative pressure ventilation useful?
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Patients with chronic respiratory failure.
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What can be considered for acute exacerbation of COPD?
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Non invasive positive pressure ventilation , to avoid intubation and conventional mechanical ventilation.
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What is positive end- expiratory pressue used for?
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PEEP is used primarily to improve oxygenation and lower FIO2 in patients with serre oxygenation problems and refactory hypoxemia.
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What should you use with SIMV mode?
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Pressure support of 5 to 10 cm H2O to over come WOB.
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What do you adjust for PSVmax?
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The pressure limit to achieve a tidal volume of 10-12 mL/kg with a rate of 10-20 breaths/min.
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What can help improve oxygenation in ALI/ARDS patients?
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Pressure-control ventilation with a prolonged inspiratory time may be useful in limiting pressure and improving oxygenation.
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What determines the optimal ventilatory settings for each patient?
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The pathophysiological status of that patient.
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What are the intial ventilator settings for most patients?
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Tidal volume of 10-12mL/kg with a rate of 10-12 breaths/min.
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What are the initial settings for a ALI/ARDS patient?
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Tidal volume of 8mL/kg and a volume adjusted to 6mL/kg to maintain plateau pressure at 30cmH2O or less.
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What is a common cause of metabolic acidosis?
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Lactic acidosis due to severe hypoxia, often after cardiac arrest or severe hypotension.
Renal failure and diabetic or alcholic ketoacidosis also. |
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What are some lung strategies in the management of AlI/ARDS?
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Use of lower tidal volume(6mL/kg), maintaining plateau pressure at 30cmH2O or less, permissive hypercapnia, and PEEP set above the lower inflection point on the static pressure-volume curve.
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What is permissive hypercapnia/
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Decision to allow Paco2 to increase and pH to decrease. An elevated Paco2 resulting in a pH in the range of 7.25 to 7.35.
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What should trigger sensitivity be set at?
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Set to achieve minimal trigger work without autocycling.
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What should inspiratory flow be initially set at?
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60L/min to achieve an inspiratory time of approximately 1 second and an I:E ratio of 1:2 or better.
When in doubt , set the initial FIO2 at 1.O. |
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What should PEEP be set at?
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Initial PEEP level of 3 to 5 cm H2dO may help maintain lung volume and prevent atelectasis.
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When is Auto PEEP a problem?
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Patients with COPD and asthma.
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What are the ventilator alarms for?
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Warning clinicians of a device malfunction or changes in the patient's condition.
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Why are FIO2 and PEEP adjusted for?
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To optimize oxygenation without harmful effects.
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What is a goal of PEEP?
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To achieve a Pao2 of 60 to 100mmHg with an FIO2 of 0.40 to 0.50 or less.
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What are adjusted to optimize ventilation?
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Rate and tidal volume.
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What optimises patient-ventilator interaction?
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Mode of ventilation, trigger sensitivity, and inspiratory flow settings.
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What improves oxgenation in ventiltor patients?
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Bronchial hygine, optimal humidification, bronchodilators, turning, sitting up in bed, suctioning, and airway care.
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What may improve oxygenation in ALI/ARDS patients?
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Prone positioning.
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What alternative lung protective strategies is there for ALI/ARDS patients?
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ECMO,IVOX,HFV, and tracheal gas insufflation.
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