A patient, being mechanically ventilated for airflow obstruction, ...

[asan beg]

A patient, being mechanically ventilated for airflow obstruction, has developed auto-PEEP. Which of the following physiologic and/or mechanical changes can the therapist expect this patient to experience? I. increased right ventricular filling II. respiratory muscle disadvantage III. elevated end-expiratory alveolar pressures IV. decreased respiratory muscle trigger load
 
  A. II, III only
  B. III, IV only
  C. I, II, III only
  D. I, II, IV only

Question 2

Which of the following pathophysiologic conditions can result from acute airway narrowing and increases in airway resistance during respiratory failure caused by airflow obstruction? I. lung regions that cannot be completely emptied II. decreased pulmonary compliance III. respiratory muscle overload IV. impaired cardiac filling
 
  A. I, III only
  B. I, II, IV only
  C. I, III, IV only
  D. II, III, IV only

[pami445]

Answer to Question 1

ANS: A
A. Correct response: The development of air trapping and auto-PEEP creates several challenges regarding the mechanical ventilation of patients with airflow obstruction. These include (1) placing the ventilatory muscles at a mechanical disadvantage, (2) imposing significant breath trigger loads on the muscles of ventilation, (3) reducing right ventricular filling, and (4) increases end-expiratory alveolar pressure. Auto-PEEP does not increase baseline pressure because it is not seen on the pressure-time scalar. Auto-PEEP can be seen under end-expiratory pause conditions.
B. Incorrect response: See explanation A.
C. Incorrect response: See explanation A.
D. Incorrect response: See explanation A.

Answer to Question 2

ANS: C
A. Incorrect response: See explanation C.
B. Incorrect response: See explanation C.
C. Correct response: Respiratory failure from airflow obstruction is a direct consequence of acute airway narrowing and increases in airway resistance. These changes lead to two mechanical alterations. First, the increased pressures required for airflow may overload respiratory muscles, producing ventilatory pump failure with spontaneous minute ventilation inadequate for gas exchange. Second, the narrowed airways create regions of the lungs that cannot be properly emptied and returned to their normal resting volume. This occurrence is called air trapping and produces elevated end-expiratory pressures (i.e., auto-PEEP). Overinflated regions may compress more healthy regions of the lung, and impair ventilationperfusio n matching. The high intrathoracic pressures may also impair cardiac filling.
D. Incorrect response: See explanation C.

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[Kedrick2014]

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