Mechanical Ventilation CH 9,10,12,13 Q's from Pilbeam.docx

Vt / (Plateau - PEEP) - correct answer Static compliance formula? The arrow indicates an active exhalation by the patient. - correct answer Refer to the scalars for pressure, flow, and volume in pressure support ventilation (PSV) in the figure below to answer the following questions. What caused the pressure spike indicated by arrow A on the pressure-time waveform? The flow cycle criterion might be increased to a higher percentage so that TI is shorter. - correct answer What ventilator parameter might be adjusted to eliminate this problem found in the scalars? The expiratory flow pattern at arrow B indicates air trapping. - correct answer What caused the flow waveform during exhalation indicated by arrow B? Shortening the TI might allow a longer time for exhalation and eliminate this problem. Suctioning of the patient or administration of a bronchodilator might be indicated to reduce Raw. Because this is PS, reducing the set pressure might reduce both VT and, thus reducing air trapping. However, this type of adjustment would have to be monitored to ensure that the patient is still adequately ventilated. - correct answer What parameters might be adjusted on the ventilator to eliminate this problem? The prolonged exhalation of volume suggests airway resistance; checking a flow-volume loop might confirm this finding. - correct answer What pulmonary change is suggested by the exhalation volume waveform indicated by arrow C? It is set at a high percentage of the peak flow. Notice the distance from end of flow to baseline. - correct answer Is the flow cycle percentage set at a high or low percentage of peak flow? The pressure-time curve does not have a concave appearance; however, the curve would not take this shape with pressure-targeted ventilation. The patient can get as much flow as needed and the pressure will be maintained. The ventilator would increase flow to achieve the set pressure if the patient were actively inhaling. As long as a rise time or slope does not reduce inspiratory flow, the inadequate flow should not be a problem. - correct answer Is there any indication of inadequate inspiratory flow? The target variable is pressure. The mode could be PC-CMV, but there are not enough breaths to determine whether it is PC-CMV (AC/PC) or PC-IMV (Intermittent mandatory ventilation). The breath shown is time-triggered, pressure targeted, and time cycled (flow drops to zero before end inspiration). - correct answer What target variable is illustrated in figure A? The set pressure is 20 cm H2O. - correct answer What is the set pressure in figure A? VT is 500 mL. - correct answer What is the delivered VT in figure A? Plateau is 20 cm H2O. Because the flow drops to zero during inspiration, there is a period of no flow before exhalation begins. The pressure at that time is the same at the ventilator and in the lungs. - correct answer What is the Plateau in figure A? A leak is present; the inspired and expired volumes are not the same. - correct answer What problem is indicated by the volume- time curve in figure A? The target variable is volume. The mode of ventilation is ACVC. You can tell it is volume targeted because it has a constant flow curve. You can tell it is ACVC because you can see the beginning of a second breath and it is also a mandatory breath. - correct answer What is the target variable illustrated and how do you determine the mode? . The breath is patient-triggered. Notice the negative pressure before the breath is initiated which signifies a patient-triggered breath. - correct answer Is the breath patient-triggered or time-triggered? Based on the pressure- time curve, the problem is inadequate flow. - correct answer What problem is indicated by the pressure scalar? The set flow is about 40 L/ min. The patient draws in more flow which is the curved portion of the flow. - correct answer What is the set flow? The patient is actively inhaling during inspiration, and the ventilator is providing additional flow. This is probably a newer generation ICU ventilator with a responsive inspiratory valve. - correct answer Why is the flow delivery variable during inspiration? Volume delivery will increase because the patient can demand more flow than the set amount. - correct answer What causes the change in flow delivery and how does this affect volume delivery? PIP is about 17.5 cm H2O. - correct answer What is the PIP? The delivered VT is about 700 mL. - correct answer What is the approximate delivered VT? The pressure- volume loop begins at a pressure of zero, therefore no PEEP has been set. - correct answer Has a PEEP been set? Compliance is about 40 mL/ cm H2O. delta V/ delta P - correct answer What is the compliance? delta V/ delta P - correct answer Compliance formula