Monitoring Oxygen Levels RsCr 220 MONITORING OXYGEN LEVELS

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Monitoring Oxygen Levels RsCr 220 MONITORING OXYGEN LEVELS Powered By Docstoc
					                                                              Monitoring Oxygen Levels
                                                                             RsCr 220
ABG, Pulse Oximetry and Transcutaneous Monitoring

Monitoring Patient : (AARC Guidelines)
   Clinical assessment including but not limited to cardiac, pulmonary, and
      neurological status
   Assessment of physiologic parameters: measurement of oxygen tensions or
      saturation in any patient treated with oxygen
      o In conjunction with the initiation of therapy; or
      o Within 12 hours of initiation with FIO2 < 0.40
      o Within 8 hours, with FIO2 > or = 0.40 (including post anesthesia recovery)
      o Within 72 hours in acute myocardial infarction
      o Within 2 hours for any patient with the principal diagnosis of COPD
      o Within 1 hour for the neonate

Blood is drawn anaerobically from a peripheral artery (radial, brachial, or femoral) via a
single needle puncture, or from an indwelling arterial cannula or catheter for multiple
Repeated puncture of a single site increases the likelihood of hematoma, scarring, or
laceration of the artery. Care should be exercised to use alternate sites for patients
requiring multiple punctures. An indwelling catheter may be indicated when multiple
sampling is anticipated.
Either method provides a blood specimen for direct measurement of partial pressures of
carbon dioxide (PaCO2) and oxygen (PaO2), hydrogen ion activity (pH), total hemoglobin
(Hbtotal), oxyhemoglobin saturation (HbO2), and the dyshemoglobins
carboxyhemoglobin (COHb) and methemoglobin (MetHb).

The following should be monitored as part of arterial blood sampling:
    Proper application of patient device (e.g., mask or cannula) at a prescribed
    Patient's respiratory rate
    Patient's temperature

Assessment of Need
The following findings may assist the clinician in deciding whether arterial blood
sampling is indicated:
    History and physical indicators (e.g., positive smoking history, recent onset of
       difficulty in breathing independent of activity level, trauma)
    Presence of other abnormal diagnostic tests or indices (abnormal pulse oximetry
       readings or CXR)
    Initiation of, administration of, or change in therapeutic supplemental oxygen or
       mechanical ventilation
    Preoperative surgical risks
    Projected enrolment in a pulmonary rehabilitation program or home oxygen

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Blood Gas Analyzers
The blood that is drawn from the patient must be taken to the lab and be analyzed. The
pH, carbon dioxide and oxygen are directly measured with the three different electrodes
in the blood gas analyzer. Other important values (HCO3 and BE) are calculated.
A co-oximeter analysis is often done at the same time to measure hemoglobin (Hbtotal),
oxyhemoglobin saturation (HbO2), and the dyshemoglobins carboxyhemoglobin (COHb)
and methemoglobin (MetHb).


Pulse oximetry provides estimates of arterial oxyhemoglobin saturation (SaO2) by
utilizing selected wavelengths of light to non-invasively determine the saturation of
oxyhemoglobin (SpO2).

The need to monitor the adequacy of arterial oxyhemoglobin saturation

Device Limitations / Validation of Results
Pulse oximetry is considered a safe procedure, but because of device limitations, false-
negative results for hypoxemia and/or false-positive results may lead to inappropriate
treatment of the patient.
     motion artifact
     abnormal hemoglobins (primarily carboxyhemoglobin [COHb] and met-
       hemoglobin [metHb])
     intravascular dyes
     exposure of measuring probe to ambient light during measurement
     low perfusion states
     skin pigmentation
     nail polish or nail coverings with finger probe
     inability to detect saturations below 83% with the same degree of accuracy and
       precision seen at higher saturations

To validate pulse oximeter readings, incorporate or assess agreement between SpO2 and
arterial oxyhemoglobin saturation (SaO2) obtained by direct measurement - these
measurements should be initially performed simultaneously and then periodically re-
evaluated in relation to the patient's clinical state.
To help assure consistency of care (between institutions and within the same institution)
based on SpO2 readings, assess
     selection of proper probe and appropriate placement (the probe is attached to its
         intended site);
     strength of waveform or pulse amplitude strength; assure that device is detecting
         an adequate pulse.
     clinical appearance of patient - subjective assessment of perfusion at measuring
         site (e.g., cyanosis, skin temperature)

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      agreement between patient's heart rate as determined by pulse oximeter and by
       palpation and heart monitor

Clinical judgment must be exercised. When disparity exists between SpO2 and SaO2
readings, and the clinical presentation of the patient, possible causes should be explored
before results are reported. Discrepancies may be reduced by monitoring at alternate sites
or appropriate substitution of instruments or probes. If such steps do not remedy the
disparity direct measurement of arterial blood gas values should be requested.

for Neonatal & Pediatric Patients

Transcutaneous monitoring measures skin-surface PtcO2 and PtcCO2 to provide estimates
of arterial partial pressure of oxygen and carbon dioxide (PaO2 and PaCO2). The devices
induce hyperperfusion by local heating of the skin and measure the partial pressure of
oxygen and carbon dioxide electrochemically.

Hazards and Complications
Indicated usually with Neonate and Newborns, it can cause problems with patients with
poor skin integrity and/or adhesive allergy.

PtcO2 and/or PtcCO2 monitoring is considered a safe procedure, but because of device
limitations, false-negative and false-positive results may lead to inappropriate treatment
of the patient. In addition, tissue injury may occur at the measuring site (eg, blisters,
burns, skin tears).

Limitations and validation of results
PtcO2 is an indirect measurement of PaO2 and, like PaO2, does not reflect oxygen
delivery or oxygen content. Complete assessment of oxygen delivery requires knowledge
of hemoglobin, saturation, and cardiac output. In a similar way, PtcCO2 is an indirect
measurement of PaCO2.
Transcutaneous blood gas monitoring should be continuous for development of trending
data. Spot checks are not appropriate.


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