Page 55 - Clinical Application of Mechanical Ventilation

Principles of Mechanical Ventilation 21

TABLE 1-11 Causes of Ventilatory Pump Failure

Type Clinical Conditions

Chest trauma Flail chest
Tension pneumothorax
Premature birth Idiopathic respiratory distress syndrome

Electrolyte imbalance Hyperkalemia
Geriatric patients Fatigue of respiratory muscles

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SUMMARY

Mechanical ventilation is used for many different clinical conditions. Essentially all
uses of mechanical ventilation are targeted toward patients who fail to ventilate or
oxygenate adequately. Ventilatory and oxygenation failure may be due to the adverse
changes in a patient’s physiologic functions (i.e., depressed respiratory drive, exces-
sive ventilatory workload, and failure of ventilatory pump). These abnormal physi-
ologic functions should be identified early on so that the indications for mechanical
ventilation are clearly delineated.
While mechanical ventilation does not treat any ventilation or oxygenation abnor-
malities per se, it is a useful adjunct to support the gas exchange function until effective
spontaneous breathing or oxygenation is restored.

Self-Assessment Questions

1. Airway resistance may be increased in all of the following clinical conditions except:
A. airway obstruction.
B. endotracheal tube with small internal diameter.
C. condensation in ventilator circuit.
D. tachycardia.

2. A mechanically ventilated patient has an increased airflow resistance due to unknown reasons. In assess-
ing the patient-ventilator system, the therapist should see ___ on the pressure-volume (P-V) display.
A. widening (bowing) of the P-V loop
B. narrowing of the P-V loop
C. shifting of the P-V slope toward the volume axis
D. shifting of the P-V slope toward the pressure axis

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