Ch. 9 Test, Ventilator Graphics Flashcards
The two waveforms that are common for pressure scalars are which of the following?
a. Sinusoidal and ascending ramp
b. Rectangular and exponential rise
c. Descending ramp and ascending ramp
d. Exponential decay and descending ramp
ANS: B
Pressure waveforms are usually the rectangular or rising exponential type.
The most important factor to affect the degree of resistance in the airways is which of the following?
a. Flow rate of the gas
b. Viscosity of the gas
c. Length of the airways
d. Diameter of the airways
ANS: D
The most important factor affecting the degree of airway resistance is the diameter of the airways. The mathematical law that determines this fact is Poiseuille’s law. A large diameter airway will have low airway resistance and there will be a greater flow of gas. A small diameter airway will have high resistance and there will be a lower flow.
The respiratory therapist observes the pressure-time scalar seen below. Wave A was generated at 1300 hour and wave B at 1600 hour. The action that is most appropriate for this situation is which of the following?
a. Add positive end-expiratory pressure (PEEP).
b. Change the endotracheal tube (ET).
c. Change to pressure-controlled continuous mandatory ventilation (PC-CMV).
d. Administer a bronchodilator.
ANS: D
When comparing the two waveforms it should be noted that the plateau pressures (Pplateau) are the same for both, 15 cm H2O. However, the peak inspiratory pressure (PIP) is higher in waveform B, 35 cm H2O, as opposed to waveform A, 27 mm H2O. This indicates an increase in transairway pressure (PTA) and therefore, airway resistance. The most appropriate answer is to administer a bronchodilator. If the ET tube was too small the PTA would have been consistently high from the start of mechanical ventilation. Adding PEEP or switching to pressure-controlled continuous mandatory ventilation (PC-CMV) would be appropriate if the Pplateau was increasing.
The ventilator graphics generated by mechanical ventilation with pressure-controlled continuous mandatory ventilation (PC-CMV), rate 18, peak inspiratory pressure (PIP) 25 cm H2O, positive end-expiratory pressure (PEEP) 5 cm H2O, are shown in the scalars below. Interpretation of these scalars reveals which of the following?
a. The flow rate is set too high and should be reduced.
b. There is air trapping that could be due to a high respiratory rate.
c. The ventilator settings are appropriate and there are no problems.
d. There is a leak in the system that needs to be identified and corrected.
ANS: B
Breaths are beginning prior to the patient completely exhaling. This is shown on the flow-time scalar by the expiratory flow not having enough time to return to zero before the next breath is delivered. It is possible that this is caused by the set rate of 18 breaths/min and/or by an increased airway resistance. One can also conclude that there is unintended positive end-expiratory pressure (auto-PEEP) preset in this situation.
The respiratory therapist sees the following scalars on the screen of a ventilator providing support to a patient in the ICU. What action should the respiratory therapist take?
a. Switch to the volume-controlled intermittent mandatory ventilation (VC-IMV) mode.
b. Increase the flow rate to 60 L/min.
c. Decrease the sensitivity to 2 cm H2O.
d. Increase the tidal volume to 550 mL.
ANS: C
The breaths shown are both patient-triggered. Negative deflections on the pressure-time scalar are present for both complete breaths shown. There is also a negative deflection between the two that did not result in a ventilator breath. A closer look at the amount of pressure required to trigger a ventilator breath shows that it is set at 10 cm H2O. The negative deflection in the center of the pressure-time scalar demonstrates that the patient could not generate enough negative pressure to trigger a breath. Therefore, the sensitivity needs to be reduced to 2 cm H2O.
The volume curve on a volume-time scalar is consistently dropping below the baseline during exhalation. The first action to take is which of the following?
a. Measure the plateau pressure.
b. Measure the endotracheal (ET) tube cuff pressure.
c. Check the ventilator circuit for a leak.
d. Assess the patient for active exhalation.
ANS: D
When the volume drops below the baseline during exhalation, the cause could be active exhalation or an inspiratory time that is too long. Assessing the patient for active exhalation is the only viable answer given the choices. By doing the assessment the respiratory therapist can determine whether active exhalation is the cause.
An inadequate flow setting during volume ventilation will cause which of the following to occur?
a. The volume curve will drop below the zero baseline.
b. The volume curve will not drop to the zero baseline.
c. The exhaled flow will take longer to rise to the zero baseline.
d. The pressure-time curve will appear concave during inspiration.
ANS: D
When the flow rate setting is inadequate, the pressure-time scalar takes a concave shape during inspiration. A volume curve dropping below baseline is indicative of active exhalation. A volume curve that ends above baseline indicates a leak. An exhaled flow curve that takes the entire expiratory time to rise back to zero baseline is indicative of increased airway resistance.
The respiratory therapist observes the following pressure-time and flow-time scalars following a patient being intubated and placed on a mechanical ventilator using volume ventilation. The most appropriate action is which of the following?
a. Increase the set flow rate.
b. Switch to pressure control.
c. Increase the set tidal volume.
d. Change to a decelerating flow pattern.
ANS: A
When the flow rate setting is inadequate, the pressure-time scalar takes on a concave shape during inspiration when the patient is actively inhaling. In this case the demand exceeds the ventilator setting and capability. The inspiratory demand of the patient will be provided for by increasing the set flow.
The type of flow curve produced by volume ventilation with constant flow is which of the following?
a. Sinusoidal
b. Rectangular
c. Descending ramp
d. Exponential decay
ANS: B
Volume ventilation with a constant flow will produce a rectangular flow curve unless a different flow pattern is chosen. Pressure ventilation creates a descending curve that varies with both lung characteristics and patient flow demand.
During pressure-controlled continuous mandatory ventilation (PC-CMV) the respiratory therapist observes the pressure-time scalar shown below. The most appropriate action to take is which of the following?
a. Adjust the inspiratory time.
b. Increase the flow rate setting.
c. Adjust the inspiratory rise time control.
d. Increase the peak inspiratory pressure setting.
ANS: C
The pressure-time scalar shows a pressure spike at the beginning of the pressure curve before the pressure adjusts to the set value. Adjusting the inspiratory rise time control will slow the rate at which pressure and flow exit the ventilator. This will reduce or eliminate the pressure spike.
An increase in airway resistance during pressure ventilation will result in which of the following?
a. Plateau pressure (PPlateau) will increase.
b. Volume curve will resemble an igloo.
c. Inspiration will end prior to flow tapering to zero.
d. Pressure curve will become concave on inspiration.
ANS: C
With increased airway resistance the flow-time scalar will show a curve that is flatter in appearance. Flow will not drop to zero by the time the set inspiratory time is reached. Consequently, the ventilator and lung pressures do not equilibrate and this can affect the overall volume delivered to the patient.
A reduction in compliance during pressure ventilation will cause which of the following?
a. Delivered tidal volume will decrease.
b. Volume curve will end under the zero line.
c. Inspiration will end prior to flow tapering to zero.
d. Pressure curve will become concave on inspiration.
ANS: A
When compliance is reduced during pressure ventilation the volume delivered will be reduced proportionally. The volume curve ending under the zero line is indicative of active exhalation. Inspiration ending prior to the flow tapering to zero is consistent with an increase in airway resistance. The pressure curve becoming concave on inspiration is consistent with inadequate flow.
Delayed termination during pressure support ventilation (PSV) can be avoided with patients who have chronic obstructive pulmonary disease (COPD) by doing which of the following?
a. Increase inspiratory time
b. Increase flow-cycle percent
c. Change the flow pattern
d. Decrease peak inspiratory pressure
ANS: B
The presence of active exhalation during pressure support ventilation (PSV) indicates that the patient is trying to end the breath early. This is referred to as delayed termination and is associated with patient-ventilator asynchrony. This phenomenon is often seen with patients who have increased airway resistance, as in chronic obstructive pulmonary disease (COPD). Since inspiratory time is determined by flow cycling in PSV, increasing the flow-cycle setting will shorten inspiration, allowing more time for exhalation.
During a patient-ventilator system check the respiratory therapist notices that the pressure-volume loop begins at zero on the x-axis but does not return to zero during expiration. The cause of this is which of the following?
a. Active exhalation
b. Inadequate sensitivity
c. Ventilator circuit leak
d. Decreased compliance
ANS: C
When the loop on a pressure-volume loop does not return to zero during exhalation, there is a leak in the ventilator circuit.
Which of the following conditions causes a pressure-volume loop during volume-controlled continuous mandatory ventilation (VC-CMV) to extend farther to the right and flatten out?
a. Asthma
b. Bronchitis
c. Emphysema
d. Pneumonia
ANS: D
The extension to the right and flattening out of the pressure-volume loop during VC-CMV is indicative of decreasing compliance. This could be caused by pneumonia. Asthma, bronchitis, and emphysema all have increased airway obstruction.
