Department of Intensive Care Medicine, Ng Teng Fong General Hospital, Jurong Health Campus, National University Health System, 1 Jurong East Street 21, Singapore, 609606, Singapore.
Department of Respiratory Therapy, Ng Teng Fong General Hospital, National University Health System, 1 Jurong East Street 21, Singapore, 609606, Singapore.
BMC Pulm Med. 2022 Sep 16;22(1):350. doi: 10.1186/s12890-022-02121-9.
High flow nasal cannula (HFNC) is increasingly being used to support patients with acute respiratory failure (ARF) and to avoid need for intubation. However, almost one third of the patients do not respond and require escalation of respiratory support. Previously, ROX index (SpO/FIO [SF] ratio/respiratory rate) has been validated among pneumonia patients to facilitate early recognition of patients likely to fail HFNC and therefore, benefit from timely interventions. However, it has been postulated that incorporation of PaO/FIO (PF) ratio from arterial blood gas (ABG) analysis may better predict the outcome of HFNC compared to indices that utilizes SF ratio. Similarly, heart rate increase after HFNC therapy initiation has been found to be associated with HFNC failure. Therefore, we aimed to compare ROX index with a new modified index to predict HFNC outcomes among ARF patients.
This single centre 2-year retrospective study included ARF patients of varying etiologies treated with HFNC. The modified index incorporated heart rate and substituted PF ratio for SF ratio in addition to respiratory rate. We named the index POX-HR and calculated Delta POX-HR index as the difference pre- and post-HFNC initiation POX-HR. We also recorded ROX index at the time when post-HFNC initiation ABG was done ('post-HFNC initiation ROX') and calculated Delta ROX. HFNC success was defined as no need of escalation of respiratory support or discharged to ward within 48 h of HFNC initiation, or successful wean off HFNC for at least 12 h. Evaluation was performed using area under the receiver operating characteristic curve (AUROC) and cut-offs assessed for prediction of HFNC outcomes.
One hundred eleven patients were initiated on HFNC for ARF, of whom 72 patients (64.9%) had HFNC success. Patients with HFNC failure had significantly lower values for all the indices. At median of 3.33 h (IQR 1.48-7.24 h), Delta POX-HR demonstrated the best prediction accuracy (AUROC 0.813, 95% CI 0.726-0.900). A Delta POX-HR > 0.1 was significantly associated with a lower risk of HFNC failure.
Our proposed modified dynamic index (Delta POX-HR) may facilitate early and accurate prediction of HFNC outcomes compared to ROX index among ARF patients of varied etiologies.
高流量鼻导管（HFNC）越来越多地被用于支持急性呼吸衰竭（ARF）患者，并避免需要插管。然而，几乎三分之一的患者没有反应，需要升级呼吸支持。此前，ROX 指数（SpO/FIO[SF] 比值/呼吸频率）已在肺炎患者中得到验证，以帮助早期识别可能无法耐受 HFNC 的患者，从而从及时干预中受益。然而，有人推测，将动脉血气（ABG）分析中的 PaO/FIO（PF）比值纳入其中，可能比利用 SF 比值的指数更好地预测 HFNC 的结果。同样，HFNC 治疗开始后心率的增加也与 HFNC 失败有关。因此，我们旨在比较 ROX 指数与新的改良指数，以预测 ARF 患者 HFNC 的结果。
这项单中心 2 年回顾性研究纳入了不同病因的 ARF 患者，他们接受了 HFNC 治疗。改良指数纳入了心率，并将 PF 比值替代 SF 比值，同时还纳入了呼吸频率。我们将该指数命名为 POX-HR，并计算出 HFNC 起始前后的 POX-HR 差值（Delta POX-HR 指数）。我们还记录了在进行 HFNC 起始后 ABG 检查时的 ROX 指数（'HFNC 起始后 ROX'），并计算了 Delta ROX。HFNC 成功定义为无需升级呼吸支持或在 HFNC 起始后 48 小时内出院到病房，或成功脱机 HFNC 至少 12 小时。使用接受者操作特征曲线（AUROC）下面积进行评估，并评估预测 HFNC 结果的截断值。
111 名 ARF 患者接受 HFNC 治疗，其中 72 名（64.9%）HFNC 成功。HFNC 失败的患者所有指数的数值均明显较低。在中位数为 3.33 小时（IQR 1.48-7.24 小时）时，Delta POX-HR 显示出最佳的预测准确性（AUROC 0.813，95%CI 0.726-0.900）。Delta POX-HR>0.1 与 HFNC 失败的风险降低显著相关。
与 ROX 指数相比，我们提出的改良动态指数（Delta POX-HR）可能在不同病因的 ARF 患者中更有助于早期、准确地预测 HFNC 的结果。
