Arterial blood gas analyses and measurement of SpO2
As a routine practice of our clinic, ABG samples were taken from punctures of the radial artery without placing an arterial catheter. Brachial or femoral artery were punctured when arterial blood could not be taken from the radial artery. The indications of ABG sampling in our clinic were as follows: a SpO2 below 90%, presence of unexplained or clinically inconsistent hypoxemia, a significant increase in the fraction of inspired oxygen (FiO2) to achieve target oxygen saturation; the presence of acute dyspnea, lethargy or other signs of carbon dioxide retention in a patient with risk factors for hypercapnic respiratory failure and patients at risk for metabolic conditions. If the patient required any oxygen supplementation, oxygen therapy was administered via low flow oxygen systems, including a nasal cannula, simple face mask or non-rebreathing mask with the target oxygen saturation > 90%. All the ABG samples were analyzed within 15 minutes with using the ABL800 blood gas analyzers (Radiometer Medical ApS, Denmark).
As our standard of care in wards, blood pressure, heart rate, body temperature and SpO2 of patients were measured and recorded to patients’ files at least four times a day. The number of these measurements was increased according to the patients’ clinical condition. In addition to these daily measurements, SpO2was measured simultaneously with ABG sampling and recorded. We routinely placed two pulse oximetry probes on both hands finger for at least two measurements of SpO2 using finger pulse oximeters (Contec CMS50D Fingertip Pulse Oximeter, Qinhusangdao, China). Then the mean of SpO2 measurements was recorded to reduce the risk of measurement error.