ATS Pulmonary Function Laboratory Manual

ATS Pulmonary Function Laboratory Management & Procedure Manual | 3rd Edition

Table 16.1

Indications for Performing Blood Gas and pH Analysis (2)

Calibration of Blood Gas Analyzer There are numerous blood gas analyzers available and each has specific manufacturer recommendations for calibra- tion. Laboratories must follow these recommendations including use of proper calibration materials and frequency of calibration. The manufacturer’s calibration materials should be traceable to certified reference materials issued by national or international metrology institutes, or natural occurring standards (3). Calibration traceability shall be documented for all materials used to perform internal and external calibration on blood gas analyzers. Documentation should include a statement by the manufacturer regarding traceability, and a certificate of analysis. Traditional systems for measurement of blood gases are calibrated with humidified gas mixtures and require correction for ambient barometric pressure to derive the partial pressure of O 2 and CO 2 in the mixtures, according to Dalton’s Law. In modern systems an internal electronic barometer is used to measure and correct for ambient barometric pressure. The function of the internal barometer should be checked regularly by comparing its reading to a reliable independent measurement. The manufacturer’s recommendations for barometric checks should be followed. Barometric pressure readings should be local conditions and not adjusted to sea level (3). Preanalytic Phase The preanalytic phase of testing encompasses procedures prior to analysis, including identification of patient, supplies, arterial puncture and sampling, storage, transport, and handling of samples. The laboratory must have policies and procedures in place describing the process from the time of sample collection to the reporting of results (4). The preanalytical phase includes patient identification, patient assessment, sample collection and labeling, handling of the sample once it has been obtained, transportation of the sample to the laboratory, and handling of the sample in the laboratory. • A specimen in a plastic collection device that has been stored at room temperature for longer than 30 minutes • The specimen does not have a complete requisition that includes: patient’s name or other unique identifier, birth date or age, date and time of sampling, location of patient, name of ordering physician, clinical indication, blood sampling site or source, respiratory rate, Fi O 2 or O 2 flow rate, body temperature, ventilator settings for mechani- cally ventilated patients, signature or initials of individual who obtained the sample. Clinical indications for blood sampling: • Evaluation of adequacy of ventilation, acid-base, oxygenation status, and the O 2 • Quantification of the patient’s response to therapeutic intervention and/or diagnostic evaluation • Monitor the severity and progression of documented disease processes Table 16.2 Relative Contraindications for Performing Blood Gas, pH, and Hemoximetry Analysis (2) Relative contraindications for blood analysis include: • Improperly functioning blood gas analyzer (non-calibrated and/or non-linear) • A blood gas analyzer that has not had functional status validated using commercially prepared quality control products, tonometered whole blood, or as part of a proficiency testing program. • A specimen containing visible air bubbles -carrying capacity of blood

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