Intrinsic PEEP determined by static pressure-volume curves — application of a novel automated occlusion method

Objective Evaluation of new computer-controlled occlusion procedure for determination of intrinsic PEEP in mechanically ventilated patients and comparison with the standard end-expiratory occlusion method.Design Prospective controlled study.Setting Intensive care unit of a university hospitalPatients 16 patients with acute respiratory failure of different degree and etiology. All patients were mechanically ventilated, heavily sedated and muscle paralyzed (non-depolarising relaxants). The type of ventilator, the inspiration/expiration ratio, FIO₂ and PEEP were selected by the attending clinicians according to the patients' need and independently from the study.Interventions Static compliance of the respiratory system (C_stat) was determined at varying external end-expiratory pressure settings: ZEEP (=ambient pressure), PEEP of 5 cmH₂O and 10 cmH₂O. All other ventilator settings were kept constant during the entire procedure.Measurements and results A computer-controlled occlusion method (SCASS) was used for determination of C_stat. Intrinsic PEEP was determined by SCASS as the extrapolated zero-volume intercept of the regression line of multiple pressure/volume data pairs (PEEP_SCASSinspir and PEEP_SCASSexpir). Directly thereafter intrinsic PEEP in this particular ventilatory setting was determined by end-expiratory occlusions (PEPP_EEO). The intrinsic PEEP values of the different methods were nearly identical with a significant correlation (p<0.0001). Mean values±SD: PEEP_SCASSinspir 7.1±4.3 cmH₂O; PEEP_SCASSexpir 7.1±4.5 cmH₂O; PEEP_EEO 7.1±4.2 cmH₂O.Conclusion Since no significant difference between PEEP_i values measured by the inspiratory and expiratory occlusion method (SCASS) was seen, this indicates that no alveolar recruitment occurred during the respiratory cycle. This study demonstrates that the automated occlusion method for measuring C_stat system can also be used with high accuracy for determination of intrinsic PEEP in mechanically ventilated patients.     

A new automated method versus continuous positive airway pressure method for measuring pressure-volume curves in patients with acute lung injury

Objective  To compare pressure–volume (P–V) curves obtained with the Galileo ventilator with those obtained with the CPAP method in patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). Design  Prospective, observational study. Setting  General critical care center. Patients and participants  Patients with ALI/ARDS and receiving mechanical ventilation. Interventions  Pressure–volume curves were obtained in random order with the CPAP technique and with the software PV Tool-2 (Galileo ventilator). Measurements and results  In ten consecutive patients, airway pressure was measured by a pressure transducer and changes in lung volume were measured by respiratory inductive plethysmography. P–V curves were fitted to a sigmoidal equation with a mean R ² of 0.994 ± 0.003. Intraclass correlation coefficients were all >0.75 (P < 0.001 at all pressure levels). Lower (LIP) and upper inflection (UIP), and deflation maximum curvature (PMC) points calculated from the fitted variables showed a good correlation between methods with intraclass correlation coefficients of 0.98 (0.92, 0.99), 0.92 (0.69, 0.98), and 0.97 (0.86, 0.98), respectively (P < 0.001 in all cases). Bias and limits of agreement for LIP (0.51 ± 0.95 cmH₂O; −1.36 to 2.38 cmH₂O), UIP (0.53 ± 1.52 cmH₂O; −2.44 to 3.50 cmH₂O), and PMC (−0.62 ± 0.89 cmH₂O; −2.35 to 1.12 cmH₂O) obtained with the two methods in the same patient were clinically acceptable. No adverse effects were observed. Conclusion  The PV Tool-2 built into the Galileo ventilator is equivalent to the CPAP method for tracing static P–V curves of the respiratory system in critically ill patients receiving mechanical ventilation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Application of continuous positive airway pressure to trace static pressure-volume curves of the respiratory system

OBJECTIVE: To evaluate a new technique for pressure-volume curve tracing. DESIGN: Prospective experimental study. SETTING: Animal research laboratory. SUBJECTS: Six anesthetized rats. INTERVENTIONS: Two pressure-volume curves were obtained by means of the super-syringe method (gold standard) and the continuous positive airway pressure (CPAP) method. For the CPAP method, the ventilator was switched to CPAP and the pressure level was raised from 0 to 50 cm H2O in 5 cm H2O steps and then decreased, while we measured lung volume using respiratory inductive plethysmography. Thereafter, lung injury was induced using very high-volume ventilation. Following injury, two further pressure-volume curves were traced. Pressure-volume pairs were fitted to a mathematical model. MEASUREMENTS AND MAIN RESULTS: Pressure-volume curves were equivalent for each method, with intraclass correlation coefficients being higher than.75 for each pressure level measured. Bias and precision for volume values were 0.46 +/- 0.875 mL in basal measurements and 0.31 +/- 0.67 mL in postinjury conditions. Lower and upper inflection points on the inspiratory limb and maximum curvature point on the deflation limb obtained using both methods and measured by regression analysis also were correlated, with intraclass correlation coefficients (95% confidence interval) being.97 (.58,.99),.85 (.55,.95), and.94 (.81,.98) (p <.001 for each one). When inflection points were estimated by observers, the correlation coefficient between methods was.90 (.67,.98) for lower inflection points (p <.001). However, estimations for upper inflection points and maximum curvature point were significantly different. CONCLUSIONS: The CPAP method for tracing pressure-volume curves is equivalent to the super-syringe method. It is easily applicable at the bedside, avoids disconnection from the ventilator, and can be used to obtain both the inspiratory and the deflation limbs of the pressure-volume curve. Use of regression techniques improves determination of inflection points.     

A standardized method of oleic acid infusion in experimental acute respiratory failure

Commonly, acute respiratory failure (ARF) in laboratory animals is induced through the intravenous infusion of oleic acid (OA). The methods by which OA is infused, and the methods by which droplets are generated, differ greatly among investigators. The resulting ARF, and the distribution of the underlying pulmonary pathology, are not highly reproducible. A method was developed that generated a reproducible, known spectrum of OA microdroplets. This method was applied to infuse a known volume of OA into the vena cava superior (VCS) in sheep, to induce ARF. In vitro studies were conducted in an observation chamber filled with saline or plasma. The distal end was cut off a 7F Swan Ganz catheter. The catheter was immersed in an observation chamber. Through one of the channels OA was infused at a low flow rate while saline was infused at variable high flow rates through a second channel. The size and the distribution spectrum of the so generated OA droplets were determined from flash photographic studies. The distribution and the size of the microdroplets depended on the media in the observation chamber, and on the saline infusion rate. In vivo studies were conducted in six anesthetized and ventilated sheep. We chose in our in vivo studies a saline flow rate of 126 mL/min and at an OA flow rate of 3 mL/min, that generated OA microdroplets 125 +/- 32 microm SD in size. OA microdroplets were generated in situ in the VCS and where then embolized into small pulmonary vessels. A total dose of 0.06 mL/kg of OA was administered in three separate doses of 0.02 mL/kg, each 10 min apart. The evolving ARF was manifested by a progressive deterioration in arterial blood gases, and a uniform opacification of all lung fields on chest X-ray films. At autopsy the lungs were diffusely consolidated. CONCLUSION: A method was developed to standardize the infusion of OA in laboratory animals that resulted in diffuse involvement of the all lungs, with a predictable and reproducible severe acute respiratory failure.     

Inflation static pressure-volume curves of the total respiratory system determined without any instrumentation other than the mechanical ventilator

Objective To assess the accuracy of static pressure-volume (PV) curves of the total respiratory system performed with the data directly obtained from the Servo 900C vs. the data obtained from an external calibrated device.Design Performance of the PV curve by the method of Levy with simultaneous recording of data obtained from both systems.Setting The general ICU of Hospital de Sabadell.Patients Ten sedated and paralyzed patients ventilated in the control mode for acute respiratory failure were evaluated.Interventions and measurements Inflation static PV curves were performed by the method of Levy. We simultaneously measured airway pressure and volume by means of calibrated pressure tranducer and pneumotachograph and by the internal devices built in the ventilator Siemens Servo 900C. Statistics were concordance analysis between the two methods and covariance analysis between derived curves.Results concordance analysis between both methods showed a 95% confidence interval of (+4%, –5%) in volume and (+2.2 cmH₂O, –1.7 cmH₂O) in pressure. Derived PV curves analyzed by MANOVA showed no significant differences whichever the method used within subject (p=0.579).Conclusion Inflation static pressure volume curves of the total respiratory system can be accurately performed with the data directly obtained from the Servo Ventilator 900C without the need of any other external device.Supported by Grant 91/1084 from FIS, Ministerio de Sanidad y Consumo, Spain     

Elastic pressure-volume curves of the respiratory system reveal a high tendency to lung collapse in young pigs

Objective: To study pressure-volume (P/V) curves over a wide pressure and volume range in pigs.¶Design: Dynamic and static P/V curves (P_dyn/V and P_st/V) and compliance of the respiratory system were studied. The effects of recruitment, positive end-expiratory pressure (PEEP) and body position were analysed.¶Setting: Research animal laboratory.¶Materials: Seven anaesthetised, paralysed and ventilated healthy pigs of 21 kg.¶Measurements: P/V curves up to a pressure of about 40 cmH₂O were recorded with a computer-controlled ventilator. P_st/V curves were obtained with the static occlusion method and P_dyn/V curves during an insufflation at a low, constant flow rate.¶Results: P_dyn/V recording showed a complex pattern. During the insufflation compliance increased, fell, increased and fell again. A 2nd ¶P_dyn/V recording immediately following the 1st one was displaced towards higher volumes and showed only one maximum of compliance. The difference between the two curves reflected: (1) lung collapse during a period of 5 min of ventilation at zero end-expiratory pressure (ZEEP) following a recruitment manoeuvre, (2) recruitment during the measurement of the 1st P_dyn/V curve. These observations were similar in the supine and in the left lateral position. After ventilation at PEEP, 4 cmH₂O, the signs of collapse and recruitment were reduced. It was confirmed that PEEP offers a partial protection against collapse. P_st/V curves showed higher volumes and higher compliance values compared to P_dyn/V curves. This reflects the influence of viscoelastance on P_dyn/V curves.¶Conclusion: The study demonstrates a particularly strong tendency to lung collapse in pigs.     

Static and dynamic pressure-volume curves reflect different aspects of respiratory system mechanics in experimental acute respiratory distress syndrome.

INTRODUCTION: A lower inflection point, an upper inflection (or deflection) point, and respiratory system compliance can be estimated from an inspiratory static pressure-volume (SPV) curve of the respiratory system. Such data are often used to guide selection of positive end-expiratory pressure (PEEP)/tidal volume combinations. Dynamic pressure-volume (DPV) curves obtained during tidal ventilation are effortlessly displayed on modern mechanical ventilator monitors and bear a theoretical but unproven relationship to the more labor-intensive SPV curves. OBJECTIVE: Attempting to relate the SPV and DPV curves, we assessed both curves under a range of conditions in a canine oleic acid lung injury model. METHODS: Five mongrel dogs were anesthetized, paralyzed, and monitored to assure a stable preparation. Acute lung injury was induced by infusing oleic acid. SPV curves were constructed by the super-syringe method. DPV curves were constructed for a range of PEEP and inspiratory constant flow settings while ventilating at a frequency of 15 breaths/min and tidal volume of 350 mL. Functional residual capacity at PEEP = 0 cm H2O was measured by helium dilution. The change in lung volume by PEEP at 8, 16, and 24 cm H2O was measured by respiratory inductance plethysmography. RESULTS: The slope of the second portion of the DPV curve did not parallel the corresponding slope of the SPV curve. The mean lower inflection point of the SPV curve was 13.2 cm H2O, whereas the lower inflection point of the DPV curve was related to the prevailing flow and PEEP settings. The absolute lung volume during the DPV recordings exceeded (p < 0.05) that anticipated from the SPV curves by (values are mean +/- SEM) 267 +/- 86 mL, 425 +/- 129 mL, and 494 +/- 129 mL at end expiration for PEEP = 8, 16, and 24 cm H2O, respectively. CONCLUSIONS: The contours of the SPV curve are not reflected by those of the DPV curve in this model of acute lung injury. Therefore, this study indicates that DPV curve should not be used to guide the selection of PEEP/tidal volume combinations. Furthermore, an increase in end-expiratory lung volume occurs during tidal ventilation that is not reflected by the classical SPV curve, suggesting a stable component of lung volume recruitment attributable to tidal ventilation, independent of PEEP.     

Improved enzymatic method for determining mannitol and its application to dog serum after mannitol infusion

An enzymatic method for mannitol quantitation has been developed. Its application mannitol levels in serum samples from dogs after mannitol infusion is illustrated. The method is based on the spectrophotometric measurement of the initial rate of NADH formation in the reaction between mannitol and NAD catalyzed by mannitol dehydrogenase. A linear relationship between initial rates and mannitol concentration is seen between 17 mumol/l and 6.7 mmol/l mannitol. From the extent of dilution of the serum sample in the assay this corresponds to serum levels of 0.5 to 200 mmol/l. Because of the high degree of substrate specificity of mannitol dehydrogenase and the extensive dilution of the serum sample in the assay reaction mixture, serum proteins and glucose do not interfere with the reaction. As a result, pre-treatment of samples to remove glucose and deproteinization are necessary.     

特普他林对油酸性肺损伤鼠肺泡液体清除功能的影响

目的：观察特普他林对油酸致伤大鼠肺损伤后肺泡上皮液体清除能力的影响。方法：采用大鼠油酸型肺损伤模型。大鼠伤后２４小时经气管滴注特普他林（１×１０－ ４ ｍ ｏｌ／Ｌ）溶液５ ｍ ｌ／ｋｇ;１ 小时后检测肺泡内液体清除率（ＡＬＣ）、总肺水量（ＴＬＷ）、肺血管外肺水量（ＥＶＬＷ）和动脉血气参数。结果：大鼠伤后２４ 小时ＡＬＣ降低４９．２％ ,ＴＬＷ 和ＥＶＬＷ 明显增加〔分别由（３．１４±０．１４）ｍ ｌ／ｇ 和（２．２５±０．１１）ｍ ｌ／ｇ 增至（４．０４±０．１３）ｍ ｌ／ｇ和（４．３２±０．１１）ｍ ｌ／ｇ〕,严重的低氧血症〔ＰａＯ２ 为（６．５５±０．２３）ｋＰａ（１ ｋＰａ＝ ７．５ ｍ ｍ Ｈｇ）〕。特普他林组ＡＬＣ较油酸致伤组增高６３．７％ ,ＴＬＷ 和ＥＶＬＷ 显著减少〔分别为（３．３９±０．１６）ｍ ｌ／ｇ 和（２．９４±０．１２）ｍ ｌ／ｇ〕。钠转运特异性抑制剂 阿咪洛利或哇巴因能部分抑制特普他林刺激肺泡内液体清除的作用。结论：特普他林通过上调钠主动转运机能,促进肺水肿液的吸收,从而改善换气功能,对急性肺损伤后肺水肿有一定的治疗作用     

Comparison between dynamic lung compliance and static compliance of the respiratory system in sick newborn infants

We compared dynamic lung compliance (Cldyn) determined by the oesophageal balloon technique with static compliance of the respiratory system (Crs) determined by an airway occlusion technique in 10 newborn infants with various cardio-respiratory diseases. The correlation between the two variables was linear and statistically significant (r = 0.911, p less than 0.0003; Cldyn = 1.51.Crs-0.48). Crs varied significantly less than Cldyn (mean coefficient of variation 3.9 for Crs vs. 9.3 for Cldyn; t = 6.06, p less than 0.0002). Since Crs is closely related to lung compliance but a more reliable parameter and technically easier to assess, we recommend the assessment of Crs instead of Cldyn in clinical practice.     

Differences in the deflation limb of the pressure-volume curves in acute respiratory distress syndrome from pulmonary and extrapulmonary origin

Objective To assess the differences in the deflation pressure-volume (PV) curves between acute respiratory distress syndrome from pulmonary (ARDSp) and extrapulmonary (ARDSe) origin.Design Prospective study.Setting Twenty-bed intensive care unit in an university hospital.Patients Ten patients within the first 24 h from meeting ARDS criteria, classified as ARDSp or ARDSe in a clinical basis.Interventions A deflation PV curve was recorded by means of decreasing steps of continuous positive airway pressure (CPAP) from 35 to 0 cmH₂O.Results The simultaneous recording of pressure at the airway opening (Pao), esophageal pressure (Pes) and volumes (V) allows us to trace the Pao-V, Pes-V and transpulmonary pressure (Ptp)-V curves. These data were fitted to a sigmoid model and ARDSp and ARDSe groups were compared. ARDSp has lower lung compliance and higher chest wall compliance than ARDSe (35.9±11.3 vs. 77.2±50.6 and 199.6±44.4 vs. 125.5±16.5 ml/cmH₂O, respectively, P<0.05). The Pao-V curve in ARDSp is shifted down and right with respect to ARDSe. The Ptp-V curve shows a similar displacement. The Pes-V curve in the ARDSp group is, however, shifted to the left. When relative values (percentage to the maximum volume achieved at 35 cmH₂O) are considered, these differences persist, but, in the Ptp-V curves, are only significant in the low-pressure range.Conclusions Differences between ARDSp and ARDSe PV curves are present all along the pressure axis and are related to differences not only in the Pes-V curve, but also in the Ptp-V curve.This study was presented in part as a poster at the 22nd International Symposium on Intensive Care and Emergency Medicine, Brussels, Belgium, March 2002.     

Positive end-expiratory pressure at minimal respiratory elastance represents the best compromise between mechanical stress and lung aeration in oleic acid induced lung injury

Introduction  

Protective ventilatory strategies have been applied to prevent ventilator-induced lung injury in patients with acute lung injury (ALI). However, adjustment of positive end-expiratory pressure (PEEP) to avoid alveolar de-recruitment and hyperinflation remains difficult. An alternative is to set the PEEP based on minimizing respiratory system elastance (Ers) by titrating PEEP. In the present study we evaluate the distribution of lung aeration (assessed using computed tomography scanning) and the behaviour of Ers in a porcine model of ALI, during a descending PEEP titration manoeuvre with a protective low tidal volume.     

An enzymatic method for measuring serum mannitol and its use in hemodialysis patients

We evaluated two chemical methods for quantifying mannitol in serum, based on the oxidation of mannitol by periodate, and measurement of the formaldehyde formed with chromotropic acid (colorimetry) or acetylacetone (fluorometry). We found interference in these methods by serum glycerol. Additionally, a high-performance liquid chromatography (HPLC) method was evaluated and found to be specific but impractical for routine use. We therefore, developed an enzymatic fluorometric procedure, based on the oxidation of mannitol by beta-NAD to fructose and NADH, in the presence of the enzyme mannitol dehydrogenase (MD). MD is not commercially available and was partially purified from cultures of Leuconostoc mesenteroides. This new method is specific, sensitive, simple, and accurate and is proposed as the method of choice for measuring mannitol in the serum of patients who received this sugar alcohol during routine hemodialysis treatment.     

高压氧对油酸诱导大鼠急性肺损伤作用的实验研究

目的 探讨高压氧(HBO)对油酸(OA)诱导大鼠急性肺损伤(ALI)的干预作用.方法 80只SD大鼠按随机数字表法分为4组.OA组30只,经鼠尾静脉注射OA 0.15 ml/kg制备ALI模型,分别于制模后4 h、3 d、7 d各随机活杀10只;OA+HBO组20只,在HBO治疗箱给予2.5 atm(1 atm=101.325 kPa)下单次治疗90 min,分别于HBO治疗后3 d、7 d各随机活杀10只;单纯HBO干预组20只,分别于HBO治疗后3 d、7 d各随机活杀10只;另设正常对照组10只.取腹主动脉血进行血气分析,测定血清肿瘤坏死因子-α(TNF-α)、白细胞介素-1β(IL-1β)、IL-6;取左肺标本,观察大体形态改变及镜下病理学改变;取右肺,测定湿/干重(W/D)比值.结果 OA组4 h后动脉血氧分压(PaO2,mm Hg,1 mm Hg=0.133 kPa)由107.70±5.37降至57.40±2.63;肉眼可见肺脏明显淤血、水肿;光镜下肺泡正常结构消失,间质水肿增宽,大量炎性细胞浸润,毛细血管明显扩张、透明膜形成;W/D比值较正常对照组明显增加(6.94±0.44比4.59±0.44,P<0.05),血清TNF-α、IL-1β、IL-6水平升高[TNF-α(μg/L):18.52±1.20比5.27±0.61,IL-1β(μg/L):13.73±1.37比6.13±1.51,IL-6(μg/L):14.51±1.21比11.14±0.89].经HBO治疗3 d、7 d时PaO2(mm Hg,3 d:79.20±1.68比59.00±2.70,7 d:94.30±3.77比74.00±3.85)、肺W/D比值(3 d:7.43±0.73比9.82±0.99,7 d:6.75±1.14比8.77±1.60)均较OA组同期有不同程度改善(P<0.05或P<0.01).治疗3 d后HBO有降低血清中IL-1β(μg/L)的作用(6.46±1.99比9.09±1.09,P<0.05).结论 HBO治疗有改善ALI大鼠氧合,促进肺水吸收、抑制部分炎症介质产生的作用.     

Effects of mannitol on the acute lung injury induced by oleic acid in rats.

Our purpose was to evaluate the pulmonary effects of mannitol infusion in a rat model of acute lung injury induced by oleic acid (OA) to compare the effects of mannitol to those of another diuretic, furosemide (FUR), and to assess if mannitol effects remained after correction of the volume depletion induced by this agent. Acute lung injury was induced in Wistar rats by intravenous administration of 100 mg/kg of OA. Mannitol (1 mL of a 20% solution) was infused either 15 min before or 2 h after OA infusion. FUR was infused intravenously in a dose (1 mg/kg) that induced a similar amount of diuresis compared to mannitol. We also studied rats that received NaCl 0.9% infusion to correct for volume losses induced by mannitol. The severity of the acute lung injury was evaluated by morphometric studies of the lungs 4 h after OA infusion. The amount of intraalveolar fluid accumulation and the intensity of alveolar distention and collapse were evaluated. Mannitol infusion either 15 min before or 2 h after OA administration resulted in a significant decrease in the amount of intraalveolar edema and alveolar distention and collapse (P < 0.001). FUR administration before OA infusion had an effect similar to mannitol. We did not observe any significant effect of mannitol when the rats received saline infusion to correct for diuresis induced by mannitol. We conclude that mannitol decreases the severity of pulmonary injury induced by OA in rats. This effect is mainly due to its diuretic properties.     

An improved method for the estimation of urinary 5-hydroxyindole-acetic acid and its application to the diagnosis of carcinoidosis

An improved method is described for the rapid estimation of 5-hydroxyindole-acetic acid (5-HIA) in urine. The method is based on the separation of 5-HIA by thin-layer chromatography, and color reaction with the sensitive reagent, p-dimethylamino-cinnamaldehyde. The method has been applied to the diagnosis of carcinoidosis.     

高效液相色谱-串联质谱法检测血清油酸及其在胰岛素抵抗中的应用

目的建立高效液相色谱-串联质谱法(HPLC-MS/MS)检测血清油酸(OA),初步评估OA在2型糖尿病(T2DM)胰岛素抵抗(IR)中的作用。方法用OA-[~(13)C_5]作为同位素内标物,OA和OA-[~(13)C_5]的离子对分别为281.3/281.3和286.3/286.3。ZORBAX SB-Aq C18反相色谱柱,流动相A为超纯水,流动相B为甲醇乙腈(1∶1,v/v),梯度洗脱,流速0.3 mL/min。根据EP15-A3文件,考察精密度和正确度、线性范围、稳定性、携带污染率等性能以评价该方法的可靠性。选取临床确诊T2DM患者109例及体检健康者100例,用HPLC-MS/MS检测血清OA,并计算胰岛素抵抗指数(HOMA-IR)评价IR,进一步分析OA与IR的关系。结果建立的检测OA的HPLC-MS/MS特异性好,在10～1 000μmol/L范围内线性关系良好,y=0.007 55x+0.004 83,r=0.997 7,定量限(LLOQ)为10μmol/L,批内不精密度(以变异系数CV表示)≤1.62%,实验室内CV≤1.73%,方法精密度较好,适合临床血清样品的测定。与健康人对照组血清OA水平(113.20±58.00)μmol/L比较,T2DM组血清OA水平(425.58±220.17)μmol/L升高,且对照组和T2DM组OA与HOMA-IR均呈正相关。以OA诊断IR的AUC为0.689,当根据约登指数确定cut-off值为235.8μmol/L时,敏感性为70.4%,特异性为63%;当OA联合FPG诊断IR时,AUC增至0.806,且与OA诊断IR的AUC比较,差异有统计学意义(P0.05)。结论建立了科学、高效定量检测血清OA浓度水平的HPLC-MS/MS,为动态监测代谢性疾病人群OA含量的变化提供了可靠的方法。