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Critically ill patients require arterial blood gas (ABG) analysis to assess oxygenation and ventilation due to limitations of noninvasive oximetry measurements. Below a pO2 of 60 mm Hg corresponding to an O2 saturation of 80%, the oxyhemoglobin saturation curve is steep and large changes in oximetry may mean small changes in oxygenation. Below this level oximetry may not correlate with oxygenation, and an arterial blood gas (ABG) should be obtained (Table 122-1).

Table 122-1Obtaining an Arterial Sample and Placement of an Arterial Line

By measuring both oxygenation and ventilation ABG analysis assesses the effects of the cardiopulmonary system in oxygen delivery. ABG analysis directly measures the pH, pCO2, and pO2. The normal range for the pH is between 7.36 and 7.44 corresponding to a normal range of 36 to 44 torr for ...

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