Questions and Answers
A patient is being mechanically ventilated in the SIMV volume control (VC) mode at a rate of 4/min. The spontaneous respiratory rate increases from 12 to 35/min. What is the most appropriate action?
A pediatric patient with status asthmaticus is receiving volume control A/C ventilation. The expiratory flow fails to drop to zero before the next machine breath. What could you do to correct the situation?
You would select an oxygen hood for an infant who needs:
A physiologic goal of CPAP is to increase:
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The most common problem encountered in applying assist-control mode ventilation is:
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A doctor orders A/C pressure control for a 50 kg postoperative female patient. Which of the following settings would you choose?
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A patient is receiving oxygen via a 28% air entrainment mask set at the manufacturer's specified input flow of 5 L/min. What occurs if you increase the O2 input flow to 7 L/min?
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A patient breathing 40% O2 has a measured physiologic shunt of 20%. When the O2 concentration is increased to 100%, his shunt increases to 35%. What best explains the increased shunt?
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To provide a more normal I:E ratio, you should adjust which of the following settings for a 100 kg adult male receiving volume control A/C?
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If the I:E ratio alarm during volume control A/C ventilation is activated on each breath, which of the following controls may be adjusted to remedy the problem?
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A neonatologist requests positioning to resolve a premature infant's pulmonary interstitial emphysema (PIE) limited to the left lung. Which position would you select?
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You are called to the ER to help in the assessment of a patient with CHF and severe pulmonary edema. What would you start the patient with for O2 delivery?
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A physician has requested delivery of a stable low concentration of O2 (FIO2=0.28) to an alert patient with normal upper airway function. Which system is best to achieve this goal?
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What maximum flow would you apply to an adult receiving O2 therapy via a high flow nasal cannula?
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A patient develops air trapping/auto-PEEP during positive pressure ventilation. This will tend to increase:
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A physician orders a 'T-tube trial' for a patient receiving volume control A/C ventilation with an FIO2 of 0.40. What FIO2 would you deliver during her spontaneous breathing trial?
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Based on a patient's ventilatory support data and blood gases, which action should you suggest?
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As compared to traditional intubation and invasive mechanical ventilation, noninvasive ventilation has which advantage?
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Which of the following is an advantage of intermittent mandatory ventilation (SIMV) over assist/control ventilation (A/C)?
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Which of the following would be appropriate ways to minimize hypoxemia while suctioning an adult patient receiving volume control A/C with PEEP?
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Study Notes
Mechanical Ventilation Techniques
- In SIMV mode, a significant total respiratory rate increase suggests increased work of breathing; increasing the machine rate maintains normal breathing.
- Pediatric patients with inadequate expiratory flow may indicate air trapping; increasing expiratory time counteracts auto-PEEP.
- An oxygen hood with a blender and humidifier is best for delivering precise FIO2 to infants, requiring flows of at least 5-7 L/min to flush CO2.
Physiological Effects of Ventilation
- CPAP increases functional residual capacity (FRC) by recruiting collapsed alveoli.
- Assist-control ventilation commonly leads to hyperventilation and hypocapnia due to excessive minute ventilation, mainly in patients with pain or anxiety.
Setting Appropriate Ventilator Parameters
- For postoperative patients on A/C pressure control, recommended settings are pressure limit around 25 cm H2O, 15 breaths/min, and 1 second inspiratory time.
- Increasing inspiratory flow improves the I:E ratio by promoting faster tidal volume delivery, allowing more exhalation time.
Oxygen Delivery Systems
- Increasing O2 input flow in air entrainment masks raises total outflow but does not significantly alter the delivered O2 concentration.
- Absorption atelectasis occurs when breathing 100% O2 in obstructed alveoli, increasing physiological shunt fraction.
- Nonrebreathing masks are ideal for CHF patients needing high O2 concentrations, ideally over 60%.
Weaning from Mechanical Ventilation
- During T-tube trials, provide 10% higher FIO2 than previously delivered by the ventilator to aid weaning.
- Changing to SIMV from A/C mode with a set rate can decrease minute ventilation in patients with respiratory alkalosis.
Noninvasive vs. Invasive Ventilation
- Noninvasive ventilation permits avoidance of intubation, shorter ventilator duration, reduced sedation requirement, and preservation of airway integrity.
- SIMV enables graded levels of support, allowing patients to breathe spontaneously, contrasting with A/C's fixed support.
Patient Care During Procedures
- To minimize hypoxemia during suctioning: preoxygenate with 100% O2 and use an appropriately sized suction catheter, limiting duration to 10-15 seconds.
- Avoid deflating the ET tube cuff or excessive catheter insertion, as these actions can worsen hypoxemia and cause atelectasis.
These notes summarize key ventilation principles, techniques, and best practices to enhance understanding and application in clinical settings.
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Description
Test your knowledge on mechanical ventilation strategies and physiological effects. This quiz covers key concepts like SIMV mode, CPAP effects, and appropriate ventilator settings for pediatric and postoperative patients. Enhance your understanding of ventilatory support and its impact on patient outcomes.
