Hypercapnia is not excluded by normoxia in neuromuscular disease patients: implications for oximetry

Emma Gray, C. Menadue, Amanda Piper, Keith Wong, Matthew Kiernan, Brendon J. Yee
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Abstract

Pulse oximetry is widely used in the assessment of chronic respiratory failure (CHRF) in neuromuscular disease (NMD) patients. CHRF is the major cause of morbidity and mortality, necessitating early diagnosis and intervention. Guidelines suggest an arterial blood gas (ABG) is indicated if oxygen saturations (SpO2)≤94% in the absence of lung disease. However, hypercapnia with normoxia (SpO2≥95%) has been observed on ABGs of patients with NMD, in particular those with motor neurone disease (MND).A single-centre retrospective audit of room-air ABGs in stable hypercapnic chronic respiratory failure (CHRF) patients from 1990–2020 was performed. Patients with parenchymal lung disease were excluded. Patients were grouped into three main categories: non-NMD, other-NMD and MND.Two-hundred and ninety-seven ABGs with hypercapnia from 180 patients with extrinsic restrictive lung disease were analysed. No patients with non-NMD, 54% of other-NMD and 36% of MND patients demonstrated hypercapnia with normoxia (χ261.33; p<0.001). The potential mechanism is proposed to be a difference in calculated respiratory quotient (RQ). If the A-a gradient is assumed to be normal, the calculated RQ was significantly higher in MND patients and other-NMD patients compared with non-NMD patients (estimated-marginal-mean 0.99 [95%CI 0.94–1.03]; 0·86 [95%CI 0.76–0.96]; 0·73 [95%CI 0.63—0.83] respectively; p<0.001) by mixed-model analysis.Hypercapnia is not excluded with normal oximetry in NMD patients and may be due to an elevated RQ. This has implications in the diagnosis and monitoring of respiratory insufficiency in NMD patients with oximetry alone.Dr Emma Gray received an NHMRC Postgraduate Scholarship.
神经肌肉疾病患者的高碳酸血症不能通过正常氧排除:对血氧饱和度的影响
脉搏血氧仪被广泛用于评估神经肌肉疾病(NMD)患者的慢性呼吸衰竭(CHRF)。慢性呼吸衰竭是发病和死亡的主要原因,因此必须及早诊断和干预。指南建议,在无肺部疾病的情况下,如果血氧饱和度(SpO2)≤94%,则应进行动脉血气(ABG)检查。然而,在 NMD 患者,尤其是运动神经元疾病(MND)患者的 ABG 中观察到了高碳酸血症与正常氧合(SpO2≥95%)。患有肺实质疾病的患者被排除在外。患者被分为三大类:非 NMD、其他 NMD 和 MND。分析了 180 名外在限制性肺部疾病患者的 297 份高碳酸血症 ABG。没有非 NMD 患者、54% 的其他 NMD 患者和 36% 的 MND 患者在常氧状态下出现高碳酸血症(χ261.33;P<0.001)。其潜在机制是计算出的呼吸商(RQ)不同。如果假定 A-a 梯度正常,通过混合模型分析,MND 患者和其他 NMD 患者的计算 RQ 明显高于非 NMD 患者(估计边际平均值分别为 0.99 [95%CI 0.94-1.03];0-86 [95%CI 0.76-0.96];0-73 [95%CI 0.63-0.83];p<0.001)。Emma Gray 博士获得了 NHMRC 研究生奖学金。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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