What mechanical criteria should be used to establish the actual ...

[bobbysung]

What mechanical criteria should be used to establish the actual PEEP setting for a mechanically ventilated patient? I. During a recruitment maneuver, the upper inflection point determines the ideal PEEP level. II. During a recruitment maneuver, the lower inflection point determines the optimal PEEP. III. The pressure-volume loop helps determine the best PEEP/ Vt combination. IV. The optimal PEEP corresponds with the best lung compliance along the deflation limb following a recruitment maneuver.
 
  A. I, II only
  B. III, IV only
  C. I, II, III only
  D. II, III, IV only

Question 2

The therapist is using gas exchange criteria to establish PEEP for a mechanically ventilated patient with ARDS. Therefore, which of the following approaches would be used to determine the appropriate PEEP level? I. the lower inflection point II. PEEP-Fio2 table III. Pao2/Fio2 IV. PEEP titration curve
 
  A. I, II only
  B. II, IV only
  C. I, II, IV only
  D. II, II, IV only

[popopong]

Answer to Question 1

ANS: B
A. Incorrect response: The upper and lower inflection points are obtained from a pressure-volume curve. Refer to the following diagram.
The upper inflection point is the point of intersection of a straight line drawn over the upper flat portion of the curve, and a straight line drawn through the steep part of the curve. The lower inflection point is the point of intersection of a straight line drawn through lower flat portion of the curve, and a straight line drawn through the steep part of the curve.
B. Correct response: The mechanical criteria involve one of the two approaches: (1) pressure-volume curves and (2) best compliance determinations. The pressure-volume curve sets the PEEP/ Vt combination to place the lung between the upper and lower inflection points of a pressure-volume loop in an attempt to minimize overdistention and recruitment-derecruitment injury. The best compliance approach uses step changes in PEEP to determine the PEEP level that gives the best compliance. As with the pressure-volume approach, the best PEEP is probably optimally determined after a recruitment maneuver has placed the lung on the deflation limb of the loop. Refer to the following diagram.  
C. Incorrect response: See explanation B.
D. Incorrect response: See explanation B

Answer to Question 2

ANS: B
A. Incorrect response: See explanation B.
B. Correct response: The two current approaches to using gas exchange criteria to set PEEP are (1) the PEEP titration curve, which generally follows a volume recruitment maneuver. Step changes in PEEP are then used to determine the lowest Fio2 that can be achieved for the desired Pao2 goal. (2) The PEEP-Fio2 table is an empirical approach that attempts to balance a Sao2 goal with the harmful effects of pressure and Fio2. These tables describe step changes in both PEEP and Fio2 to maintain a target Pao2 (Spo2). Refer to Table 15-2 on page 292 of the text.
C. Incorrect response: See explanation B.
D. Incorrect response: See explanation B