Sympathetic chemoreflex responses in obstructive sleep apnea and effects of continuous positive airway pressure therapy

BACKGROUND: Sympathetic nerve activity is increased in awake and regularly breathing patients with obstructive sleep apnea (OSA). Over time, repetitive hypoxic stress could alter sympathetic chemoreflex function in OSA. METHODS: We determined the responses to acute hypoxia (fraction of inspired oxygen of 0.1, for 5 min), static handgrip exercise, and the cold pressor test (CPT) in 24 patients with OSA (age, 50 +/- 3 years [mean +/- SEM]; apnea-hypopnea index, 47 +/- 6 events per hour) and in 14 age- and weight-matched nonapneic control subjects. Muscle sympathetic nerve activity (MSNA) [peroneal microneurography], BP, and ventilation were monitored. RESULTS: Basal MSNA was higher in OSA patients compared to control subjects (45 +/- 4 bursts per minute vs 33 +/- 4 bursts per minute, respectively; p < 0.05). Furthermore, compared to control subjects, the MSNA responses to hypoxia were markedly enhanced in OSA (p < 0.001). Whereas the ventilatory responses to hypoxia tended to be increased in OSA (p = 0.06), the BP responses did not differ between the groups (p = 0.45). The neurocirculatory reflex responses to handgrip exercise and to the CPT were similar in the two groups (p = not significant). In OSA patients who were retested after 1 to 24 months of continuous positive airway pressure (CPAP) therapy (n = 11), basal MSNA (p < 0.01) and the responses of MSNA to hypoxia (p < 0.01) decreased significantly, whereas the ventilatory responses remained unchanged (p = 0.82). CONCLUSION: These data suggest that the sympathetic responses to hypoxic chemoreflex stimulation are enhanced in OSA and may normalize in part following CPAP therapy.     

吸入一氧化氮技术治疗新生儿严重低氧血症的疗效分析

目的:探讨吸入一氧化氮(iNO)治疗新生儿严重低氧血症的临床疗效.方法:38例重症呼吸衰竭新生儿,平均胎龄(34±6)周,体重(2 187±181)g,因在常频通气(CMV)治疗过程中出现FiO2≥0.8,平均气道压≥0.98 kPa,持续2 h以上经皮氧饱和度≤90%或氧合指数(OI)＞40而采用iNO,治疗过程中监...     

Folate Levels in Patients Hospitalized with Coronavirus Disease 2019

We aimed to investigate the prevalence of decreased folate levels in patients hospitalized with Coronavirus Disease 2019 (COVID-19) and evaluate their outcome and the prognostic signifi-cance associated with its different levels. In this retrospective cohort study, data were obtained from the electronic medical records at the Sheba Medical Center. Folic acid levels were available in 333 out of 1020 consecutive patients diagnosed with COVID-19 infection hospitalized from January 2020 to November 2020. Thirty-eight (11.4%) of the 333 patients comprising the present study population had low folate levels. No significant difference was found in the incidence of acute kidney injury, hypoxemia, invasive ventilation, length of hospital stay, and mortality be-tween patients with decreased and normal-range folate levels. When sub-dividing the study population according to quartiles of folate levels, similar findings were observed. In conclusion, decreased serum folate levels are common among hospitalized patients with COVID-19, but there was no association between serum folate levels and clinical outcomes. Due to the important role of folate in cell metabolism and the potential pathologic impact when deficient, a follow-up of folate levels or possible supplementation should be encouraged in hospitalized COVID-19 patients. Fur-ther studies are required to assess the prevalence and consequences of folate deficiency in COVID-19 patients.     

Automatic titration and calculation by predictive equations for the determination of therapeutic continuous positive airway pressure for obstructive sleep apnea

BACKGROUND: It is unknown to what extent therapeutic continuous positive airway pressure (CPAP) levels obtained by various methods for the treatment of obstructive sleep apnea syndrome (OSAS) differ. This study aimed to explore the relationships among pressures titrated by an automatic CPAP (APAP) device and those calculated using different predictive equations, and to compare different ranges of calculated pressures with pressure values titrated by APAP. METHODS: In 140 OSAS patients, the 95th percentile pressure delivered by an APAP device (AutoSet T; ResMed; Sydney, NSW, Australia) during polysomnography, and pressures calculated by three equations (equation 1, Hoffstein and Miljetig [1994]; equation 2, Sériès et al [2000]; and equation 3, Stradling et al [2004]) were compared. RESULTS: Titrated and calculated pressures were weakly correlated. Significant differences were found between the mean (+/- SD) pressures (11.1 +/- 1.6, 8.3 +/- 1.8, 10.5 +/- 1.6, and 10.3 +/- 1.3 cm H(2)O, respectively) for 95th percentile APAP, and pressures calculated by equations 1, 2, and 3, except between values calculated by equations 2and 3. Differences between the calculated and APAP-derived pressures were negative for the low calculated values, and were progressively attenuated, or became positive, for the high values. The differences were smallest for calculated pressures from 11 to > 13 cm H(2)O, which were represented to a greater extent among the values calculated by equations 2 and 3 than by those calculated by equation 1. CONCLUSIONS: Considerably different therapeutic CPAP levels may be determined using various methods. The differences between the calculated and APAP-derived pressures are largest for calculated values of < 9 or > 15 cm H(2)O. The clinical consequences of these findings deserve further evaluation. Caution is still required before treating OSAS patients with calculated pressures.     

Correlation between clinical features,high-resolution computed tomography findings,and a visual scoring system in patients with pneumonia due to Mycoplasma pneumoniae

Background

Mycoplasma pneumoniae (MP) is the primary cause of community-acquired pneumonia. We aimed to evaluate the correlation between clinical features, with special reference to hypoxemia and the total affected area obtained using high-resolution computed tomography (HRCT).

突发严重低氧血症和顽固性低血压猝死1例

猝死以心源性、肺源性、神经源性猝死为多见,肿瘤所致的猝死相对较少,常常被临床忽视。本文首次报道并讨论了1例胸壁转移性肝癌破裂出血导致猝死的老年病例。旨在提醒临床医师在合并肿瘤的患者突发病情变化时,要考虑到肿瘤及其转移瘤引起突发病情变化的可能性,及时正确做出有效处理。     

COPD患者采用间断负压经鼻气道深部吸痰研究

目的 探讨COPD患者实施间断负压气道深部吸痰的效果.方法 将100例诊断为COPD并具备吸痰指征的患者,单号为对照组(50例),按常规气道内吸引法吸痰;双号为观察组(50例),采用间断开放负压吸痰,即呼气时开放负压吸痰,吸气时堵住吸痰管侧边孔关闭负压.结果 与对照组比较,观察组患者插管次数、吸痰次数减少,2次吸痰间隔延长,痰量增加,血氧饱和度较稳定且呼吸道黏膜损伤及低氧血症发生率显著降低(P＜0.05,P＜0.01).结论 COPD患者采用间断负压经鼻下气道深部吸痰能降低反复插管对患者的刺激,减少吸痰并发症的发生率.     

Explained variance for blood gases in a population with COPD

Introduction: Variation of blood gas levels in chronic obstructive pulmonary disease (COPD) patients has not been extensively reported and there is limited knowledge about predictors of chronic respiratory failure in COPD patients. Objectives: The aim of this study was to identify predictors of hypoxemia, hypercapnia and increased alveolar‐arterial oxygen difference in COPD patients. We hypothesized that prediction of arterial blood gases will be improved in multivariate models including measurements of lung function, anthropometry and systemic inflammation. Methods: A cross‐sectional sample of 382 Norwegian COPD patients, age 40–76, Global Initiative for Chronic Obstructive Lung Disease stage II–IV, with a smoking history of at least 10 pack‐years, underwent extensive measurements, including medical examination, arterial blood gases, systemic inflammatory markers, spirometry, plethysmography, respiratory impedance and bioelectrical impedance. Possible predictors of arterial oxygen (PaO₂), arterial carbon dioxide (PaCO₂) and alveolar‐arterial oxygen difference (AaO₂) were analyzed with both bivariate and multiple regression methods. Results: We found that various lung function measurements were significantly associated with PaO2, PaCO₂ and AaO₂. In addition, heart rate and Fat Mass Index were predictors of PaO₂ and AaO₂, while heart failure and current smoking status were associated with PaCO₂. The explained variance (R²) in the final multivariate regression models was 0.14–0.20. Conclusions: With a wide assortment of possible clinical predictors, we could explain 14–20% of the variation in blood gas measurements in COPD patients. Please cite this paper as: Saure EW, Eagan TML, Jensen RL, Voll‐Aanerud M, Aukrust P, Bakke PS and Hardie JA. Explained variance for blood gases in a population with COPD. Clin Respir J 2012; 6: 72–80.