{
  "abstract": "Introduction Earlobe blood gas [EBG] is routinely performed in all patients attending for a continuous positive airway pressure [CPAP] loan at the Trust. It was hypothesised that a significant decline in the overnight oximetry parameters was associated with an elevated daytime partial pressure of carbon dioxide [PaCO2]; aiding in triaging patients that needed an EBG prior to CPAP initiation. This retrospective, non-blinded, one centre service evaluation aims to streamline the current sleep pathway, reducing direct costs and patient waiting times.Methods The study population included 213 patients (Male: 73%, Female: 27%) that attended their outpatient appointment between 19/07/2019 – 15/04/2021.Results 8% of the study population showed a PaCO2 ≥ 6.0 kPa. Fisher’s test showed there was no significant difference between body mass index [BMI] ≥30 kg/m2 (p= 0.4775), smoking history (p= 0.070), morning headaches (p= 0.093), timing of EBG (p = 0.802) and PaCO2 in eucapnic and hypercapnic patients. Fisher’s test showed that there was a significant difference between BMI of ≥35 kg/m2 (p = 0.019*) and PaCO2 in eucapnic and hypercapnic patients. Spearman’s correlation showed a weak positive correlation between BMI (r= 0.239, p= <0.001 *), oxygen desaturation index [ODI] (r= 0.252, p= <0.001*), Time spent with peripheral oxygen saturation [spO2] <90% (r= 0.258, p= <0.001 *) and PaCO2 (kPa). Spearman’s correlation showed a weak negative correlation between spO2 nadir (r= -0.284, p= <0.001 *), Mean spO2 (r= -0.201, p = 0.003 *) and PaCO2 (kPa). Cut-off values including time spent with <90% spO2 ≥ 11.7% (AUC = 0.845), spO2 nadir ≤ 74% (AUC = 0.801), Mean spO2 ≤ 92.7% (AUC = 0.780), BMI ≥ 34.8 kg/m2 (AUC = 0.712) were identified through receiver operating curve analysis that could aid in triaging patients that require an EBG.Conclusion Time spent with <90% spO2, spO2 nadir, Mean spO2 and BMI ≥35 kg/m2 should be used more routinely in clinical practice to triage the need for an EBG prior to a CPAP device loan. Further research is required to assess whether serum venous bicarbonate level, spot spO2 and neck circumference could be used to triage patients that require an EBG prior to CPAP initiation.",
  "authors": [
    {
      "affiliations": [
        "Manchester Metropolitan University, Manchester, UK",
        "King’s College Hospital NHS Trust, London, UK"
      ],
      "name": "Sheron Mathew"
    },
    {
      "affiliations": [
        "Manchester Metropolitan University, Manchester, UK"
      ],
      "name": "Frederick Jones"
    },
    {
      "affiliations": [
        "King’s College Hospital NHS Trust, London, UK"
      ],
      "name": "Claire Wood"
    },
    {
      "affiliations": [
        "King’s College Hospital NHS Trust, London, UK",
        "King’s College London, UK"
      ],
      "name": "Kai Lee"
    }
  ],
  "title": "P28 ‘A retrospective service evaluation to assess the need to perform an EBG prior to every initiation of CPAP therapy’",
  "uid": "65ea5d4c-6eed-53b2-9a37-afd6319d4d72"
}