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检测病人活动的波形法：与食道压一样好吗？

文章

作者: Caroline Brown, Giorgio Iotti

日期: 08.07.2022

在机械通气的病人中，病人和呼吸机之间的不同步现象很常见 (1, 2)。

检测病人活动的波形法：与食道压一样好吗？

要点

  • 分析压力和流量波形以检测呼吸努力的概念在几十年前首次被描述，但随后关于这种方法可靠性的证据尚不明确。
  • 在最近的一项研究中，研究人员使用食道压曲线作为参考，评估了一种用于床旁评估病人活动和人机交互的波形分析系统方法。
  • 波形方法使临床医生能够检测到极高百分比的自发努力，并被证明是一种高度可重复和可靠的方法，可以识别甚至较小的不同步。

治疗的一个重要部分

病人和呼吸机的吸气和呼气时间之间的这种不匹配可能采取各种形式（如提早或较晚切换、自动触发、双重触发或无效努力），并已被证明会影响病人治疗效果 (de Wit M, Miller KB, Green DA, Ostman HE, Gennings C, Epstein SK. Ineffective triggering predicts increased duration of mechanical ventilation. Crit Care Med. 2009;37(10):2740-2745. doi:10.1097/ccm.0b013e3181a98a053​, Blanch L, Villagra A, Sales B, et al. Asynchronies during mechanical ventilation are associated with mortality.Intensive Care Med.2015;41(4):633-641. doi:10.1007/s00134-015-3692-64​)。因此，治疗的一个重要部分是能够识别这些不同步，并相应地调整呼吸机设置，以改善人机交互。

分析气道压力和流量波形以检测呼吸努力及其时间的概念在近三十年前首次被描述 (Fabry B, Guttmann J, Eberhard L, Bauer T, Haberthür C, Wolff G. An analysis of desynchronization between the spontaneously breathing patient and ventilator during inspiratory pressure support.Chest. 1995;107(5):1387-1394. doi:10.1378/chest.107.5.13875​, Giannouli E, Webster K, Roberts D, Younes M. Response of ventilator-dependent patients to different levels of pressure support and proportional assist. Am J Respir Crit Care Med.1999;159(6):1716-1725. doi:10.1164/ajrccm.159.6.97040256​)，但随后关于这种方法可靠性的证据尚不明确 (Thille AW, Rodriguez P, Cabello B, Lellouche F, Brochard L. Patient-ventilator asynchrony during assisted mechanical ventilation.Intensive Care Med. 2006;32(10):1515-1522. doi:10.1007/s00134-006-0301-82​, Colombo D, Cammarota G, Alemani M, et al. Efficacy of ventilator waveforms observation in detecting patient-ventilator asynchrony. Crit Care Med.2011;39(11):2452-2457. doi:10.1097/CCM.0b013e318225753c7​)。普遍认为需要测量食道压；然而，这需要特殊的设备，并且不是正常的临床实践。最近一项针对 16 名病人的研究分析了波形分析是否是一种床旁检测病人呼吸肌活动的可靠和可重复方法 (Mojoli F, Pozzi M, Orlando A, et al.Timing of inspiratory muscle activity detected from airway pressure and flow during pressure support ventilation: the waveform method.Crit Care.2022;26(1):32.Published 2022 Jan 30. doi:10.1186/s13054-022-03895-48​)。

应用波形法

该试验的一个关键要素是使用系统方法分析气道压力和流量波形，该方法包括五个一般生理原理和一组预先定义的特定规则（“波形法”）。所有病人均在压力支持模式下使用食道导管进行通气。该方法应用于使用近端传感器获得的气道压力和流量波形，并使用食道压 (Pes) 作为参考。对于每名病人，来自四人小组（三名高级医师和一名住院医生）的三名研究人员只分析了流量和压力波形，而另一名研究人员分析了流量和压力波形以及食道压跟踪。呼吸被分类为“正常”辅助、自动触发、双重触发或无效努力。在正常辅助呼吸的情况下，还评估了较小的不同步（触发延迟、提早切换和较晚切换）。

终点和结果

主要终点是使用波形法检测到的自发努力的百分比。次要终点包括波形和参考方法在检测较大和较小不同步方面的一致性，以及波形法的评价者之间的一致性。

共记录 4426 次呼吸。使用参考食道压测量，其中 77.8% 被确定为呼吸机正确检测到的呼吸，22.1% 被确定为无效呼吸，0.1% 被确定为自动触发呼吸。波形法能够检测到 99.5% 的自发努力和除一次外的所有自动触发呼吸。同样，将呼吸确定为辅助、自动触发、双重触发或无效的参考方法和波形法之间的一致性非常高。不同步指数——计算公式为自动触发、无效和双重触发呼吸的总和除以呼吸总次数——为 5.9%，使用波形法与食道压进行评估时没有差异。不同步总时间——计算公式为人机不同步的时间除以总记录时间——为 22.4%，其中较小的不同步占 92.1%。不同操作人员对呼吸分类的一致性也很高。

在 90% 以上的病例中，波形法使研究人员能够以足够的精确度识别呼吸努力的开始和结束，从而也可能正确识别“较小的”不同步——触发延迟、提早切换和较晚切换。

这些结果告诉我们什么？

这项研究提出了一些重要的发现。研究人员表明，波形法使临床医生能够检测到极高比例的自发努力，并准确评估病人的活动时间。即使对于较小的不同步，波形法也是高度可靠和可重复的。该研究的进一步发现强调了这一点的重要性，即 PSV 中的大多数不同步时间与较小的不同步有关。

这些结果不仅证明了波形法的可重复性（操作人员之间的高度一致性）；它们还显示，根据预定义的系统方法进行波形分析的训练起着关键作用。有证据表明，治疗机械通气病人的临床经验并不一定等同于识别不同步的能力，而 ICU 医生识别不同步的能力总体很低 (Ramirez II, Arellano DH, Adasme RS, et al. Ability of ICU Health-Care Professionals to Identify Patient-Ventilator Asynchrony Using Waveform Analysis. Respir Care.2017;62(2):144-149. doi:10.4187/respcare.047509​)。在本研究中，其中一名操作人员当时只是住院医生，但所有操作人员都至少有两年的波形分析经验，并使用具有特定规则的系统方法。作者引用这一点作为他们的发现与 Colombo 等人的发现之间差异的可能解释之一 (Colombo D, Cammarota G, Alemani M, et al. Efficacy of ventilator waveforms observation in detecting patient-ventilator asynchrony.Crit Care Med.2011;39(11):2452-2457. doi:10.1097/CCM.0b013e318225753c7​)，Colombo 等人发现从波形中检测较大的不同步具有良好的特异性，但敏感性较差。

作者得出结论，气道压力和气流的近端波形包括足够的信息来准确评估病人活动和人机交互，假设采用适当的系统分析方法，如“波形法”。

通过 IntelliSync+ 持续分析

Hamilton Medical 哈美顿医疗公司呼吸机集成的 IntelliSync®+ 技术（IntelliSync+ 可作为 HAMILTON-C6 和 HAMILTON-G5 机械呼吸机的选配功能及 HAMILTON-S1 的标准功能提供。A​）根据与“波形法”类似的原理连续分析近端流量和气道压力。这使其能够识别病人吸气努力或放松的早期迹象，并相应地启动吸气和切换到呼气。它可以自动触发吸气或呼气或两者。

 

完整引文如下： (Chao DC, Scheinhorn DJ, Stearn-Hassenpflug M. Patient-ventilator trigger asynchrony in prolonged mechanical ventilation. Chest.1997;112(6):1592-1599. doi:10.1378/chest.112.6.15921​)

不同步参考卡

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脚注

  • A. IntelliSync+ 可作为 HAMILTON-C6 和 HAMILTON-G5 机械呼吸机的选配功能及 HAMILTON-S1 的标准功能提供。

参考文献

  1. 1. Chao DC, Scheinhorn DJ, Stearn-Hassenpflug M. Patient-ventilator trigger asynchrony in prolonged mechanical ventilation. Chest. 1997;112(6):1592-1599. doi:10.1378/chest.112.6.1592
  2. 2. Thille AW, Rodriguez P, Cabello B, Lellouche F, Brochard L. Patient-ventilator asynchrony during assisted mechanical ventilation. Intensive Care Med. 2006;32(10):1515-1522. doi:10.1007/s00134-006-0301-8
  3. 3. de Wit M, Miller KB, Green DA, Ostman HE, Gennings C, Epstein SK. Ineffective triggering predicts increased duration of mechanical ventilation. Crit Care Med. 2009;37(10):2740-2745. doi:10.1097/ccm.0b013e3181a98a05
  4. 4. Blanch L, Villagra A, Sales B, et al. Asynchronies during mechanical ventilation are associated with mortality. Intensive Care Med. 2015;41(4):633-641. doi:10.1007/s00134-015-3692-6
  5. 5. Fabry B, Guttmann J, Eberhard L, Bauer T, Haberthür C, Wolff G. An analysis of desynchronization between the spontaneously breathing patient and ventilator during inspiratory pressure support. Chest. 1995;107(5):1387-1394. doi:10.1378/chest.107.5.1387
  6. 6. Giannouli E, Webster K, Roberts D, Younes M. Response of ventilator-dependent patients to different levels of pressure support and proportional assist. Am J Respir Crit Care Med. 1999;159(6):1716-1725. doi:10.1164/ajrccm.159.6.9704025
  7. 7. Colombo D, Cammarota G, Alemani M, et al. Efficacy of ventilator waveforms observation in detecting patient-ventilator asynchrony. Crit Care Med. 2011;39(11):2452-2457. doi:10.1097/CCM.0b013e318225753c
  8. 8. Mojoli F, Pozzi M, Orlando A, et al. Timing of inspiratory muscle activity detected from airway pressure and flow during pressure support ventilation: the waveform method. Crit Care. 2022;26(1):32. Published 2022 Jan 30. doi:10.1186/s13054-022-03895-4
  9. 9. Ramirez II, Arellano DH, Adasme RS, et al. Ability of ICU Health-Care Professionals to Identify Patient-Ventilator Asynchrony Using Waveform Analysis. Respir Care. 2017;62(2):144-149. doi:10.4187/respcare.04750

Patient-ventilator trigger asynchrony in prolonged mechanical ventilation.

Chao DC, Scheinhorn DJ, Stearn-Hassenpflug M. Patient-ventilator trigger asynchrony in prolonged mechanical ventilation. Chest. 1997;112(6):1592-1599. doi:10.1378/chest.112.6.1592



STUDY OBJECTIVE

To investigate patient-ventilator trigger asynchrony (TA), its prevalence, physiologic basis, and clinical implications in patients requiring prolonged mechanical ventilation (PMV).

STUDY DESIGN

Descriptive and prospective cohort study.

SETTING

Barlow Respiratory Hospital (BRH), a regional weaning center.

PATIENTS

Two hundred consecutive ventilator-dependent patients, transferred to BRH over an 18-month period for attempted weaning from PMV.

METHODS AND INTERVENTIONS

Patients were assessed clinically for TA within the first week of hospital admission, or once they were in hemodynamically stable condition, by observation of uncoupling of accessory respiratory muscle efforts and onset of machine breaths. Patients were excluded if they had weaned by the time of assessment or if they never achieved hemodynamic stability. Ventilator mode was patient triggered, flow control, volume cycled, with a tidal volume of 7 to 10 mL/kg. Esophageal pressure (Peso), airway-opening pressure, and airflow were measured in patients with TA who consented to esophageal catheter insertion. Attempts to decrease TA in each patient included application of positive end-expiratory pressure (PEEP) stepwise to 10 cm H2O, flow triggering, and reduction of ventilator support in pressure support (PS) mode. Patients were followed up until hospital discharge, when outcomes were scored as weaned (defined as >7 days of ventilator independence), failed to wean, or died.

RESULTS

Of the 200 patients screened, 26 were excluded and 19 were found to have TA. Patients with TA were older, carried the diagnosis of COPD more frequently, and had more severe hypercapnia than their counterparts without TA. Only 3 of 19 patients (16%), all with intermittent TA, weaned from mechanical ventilation, after 70, 72, and 108 days, respectively. This is in contrast to a weaning success rate of 57%, with a median (range) time to wean of 33 (3 to 182) days in patients without TA. Observation of uncoupling of accessory respiratory muscle movement and onset of machine breaths was accurate in identifying patients with TA, which was confirmed in all seven patients consenting to Peso monitoring. TA appeared to result from high auto-PEEP and severe pump failure. Adjusting trigger sensitivity and application of flow triggering were unsuccessful in eliminating TA; external PEEP improved but rarely led to elimination of TA that was transient in duration. Reduction of ventilator support in PS mode, with resultant increased respiratory pump output and lower tidal volumes, uniformly succeeded in eliminating TA. However, this approach imposed a fatiguing load on the respiratory muscles and was poorly tolerated.

CONCLUSION

TA can be easily identified clinically, and when it occurs in the patient in stable condition with PMV, is associated with poor outcome.

Patient-ventilator asynchrony during assisted mechanical ventilation.

Thille AW, Rodriguez P, Cabello B, Lellouche F, Brochard L. Patient-ventilator asynchrony during assisted mechanical ventilation. Intensive Care Med. 2006;32(10):1515-1522. doi:10.1007/s00134-006-0301-8



OBJECTIVE

The incidence, pathophysiology, and consequences of patient-ventilator asynchrony are poorly known. We assessed the incidence of patient-ventilator asynchrony during assisted mechanical ventilation and we identified associated factors.

METHODS

Sixty-two consecutive patients requiring mechanical ventilation for more than 24 h were included prospectively as soon as they triggered all ventilator breaths: assist-control ventilation (ACV) in 11 and pressure-support ventilation (PSV) in 51.

MEASUREMENTS

Gross asynchrony detected visually on 30-min recordings of flow and airway pressure was quantified using an asynchrony index.

RESULTS

Fifteen patients (24%) had an asynchrony index greater than 10% of respiratory efforts. Ineffective triggering and double-triggering were the two main asynchrony patterns. Asynchrony existed during both ACV and PSV, with a median number of episodes per patient of 72 (range 13-215) vs. 16 (4-47) in 30 min, respectively (p=0.04). Double-triggering was more common during ACV than during PSV, but no difference was found for ineffective triggering. Ineffective triggering was associated with a less sensitive inspiratory trigger, higher level of pressure support (15 cmH(2)O, IQR 12-16, vs. 17.5, IQR 16-20), higher tidal volume, and higher pH. A high incidence of asynchrony was also associated with a longer duration of mechanical ventilation (7.5 days, IQR 3-20, vs. 25.5, IQR 9.5-42.5).

CONCLUSIONS

One-fourth of patients exhibit a high incidence of asynchrony during assisted ventilation. Such a high incidence is associated with a prolonged duration of mechanical ventilation. Patients with frequent ineffective triggering may receive excessive levels of ventilatory support.

Ineffective triggering predicts increased duration of mechanical ventilation.

de Wit M, Miller KB, Green DA, Ostman HE, Gennings C, Epstein SK. Ineffective triggering predicts increased duration of mechanical ventilation. Crit Care Med. 2009;37(10):2740-2745. doi:10.1097/ccm.0b013e3181a98a05



OBJECTIVES

To determine whether high rates of ineffective triggering within the first 24 hrs of mechanical ventilation (MV) are associated with longer MV duration and shorter ventilator-free survival (VFS).

DESIGN

Prospective cohort study.

SETTING

Medical intensive care unit (ICU) at an academic medical center.

PATIENTS

Sixty patients requiring invasive MV.

INTERVENTIONS

None.

MEASUREMENTS

Patients had pressure-time and flow-time waveforms recorded for 10 mins within the first 24 hrs of MV initiation. Ineffective triggering index (ITI) was calculated by dividing the number of ineffectively triggered breaths by the total number of breaths (triggered and ineffectively triggered). A priori, patients were classified into ITI >or=10% or ITI <10%. Patient demographics, MV reason, codiagnosis of chronic obstructive pulmonary disease (COPD), sedation levels, and ventilator parameters were recorded.

MEASUREMENTS AND MAIN RESULTS

Sixteen of 60 patients had ITI >or=10%. The two groups had similar characteristics, including COPD frequency and ventilation parameters, except that patients with ITI >or=10% were more likely to have pressured triggered breaths (56% vs. 16%, p = .003) and had a higher intrinsic respiratory rate (22 breaths/min vs. 18, p = .03), but the set ventilator rate was the same in both groups (9 breaths/min vs. 9, p = .78). Multivariable analyses adjusting for pressure triggering also demonstrated that ITI >or=10% was an independent predictor of longer MV duration (10 days vs. 4, p = .0004) and shorter VFS (14 days vs. 21, p = .03). Patients with ITI >or=10% had a longer ICU length of stay (8 days vs. 4, p = .01) and hospital length of stay (21 days vs. 8, p = .03). Mortality was the same in the two groups, but patients with ITI >or=10% were less likely to be discharged home (44% vs. 73%, p = .04).

CONCLUSIONS

Ineffective triggering is a common problem early in the course of MV and is associated with increased morbidity, including longer MV duration, shorter VFS, longer length of stay, and lower likelihood of home discharge.

Asynchronies during mechanical ventilation are associated with mortality.

Blanch L, Villagra A, Sales B, et al. Asynchronies during mechanical ventilation are associated with mortality. Intensive Care Med. 2015;41(4):633-641. doi:10.1007/s00134-015-3692-6



PURPOSE

This study aimed to assess the prevalence and time course of asynchronies during mechanical ventilation (MV).

METHODS

Prospective, noninterventional observational study of 50 patients admitted to intensive care unit (ICU) beds equipped with Better Care™ software throughout MV. The software distinguished ventilatory modes and detected ineffective inspiratory efforts during expiration (IEE), double-triggering, aborted inspirations, and short and prolonged cycling to compute the asynchrony index (AI) for each hour. We analyzed 7,027 h of MV comprising 8,731,981 breaths.

RESULTS

Asynchronies were detected in all patients and in all ventilator modes. The median AI was 3.41 % [IQR 1.95-5.77]; the most common asynchrony overall and in each mode was IEE [2.38 % (IQR 1.36-3.61)]. Asynchronies were less frequent from 12 pm to 6 am [1.69 % (IQR 0.47-4.78)]. In the hours where more than 90 % of breaths were machine-triggered, the median AI decreased, but asynchronies were still present. When we compared patients with AI > 10 vs AI ≤ 10 %, we found similar reintubation and tracheostomy rates but higher ICU and hospital mortality and a trend toward longer duration of MV in patients with an AI above the cutoff.

CONCLUSIONS

Asynchronies are common throughout MV, occurring in all MV modes, and more frequently during the daytime. Further studies should determine whether asynchronies are a marker for or a cause of mortality.

An analysis of desynchronization between the spontaneously breathing patient and ventilator during inspiratory pressure support.

Fabry B, Guttmann J, Eberhard L, Bauer T, Haberthür C, Wolff G. An analysis of desynchronization between the spontaneously breathing patient and ventilator during inspiratory pressure support. Chest. 1995;107(5):1387-1394. doi:10.1378/chest.107.5.1387

It is common practice to convert patients with acute respiratory insufficiency (ARI) from controlled mechanical ventilation to some form of assisted spontaneous breathing as early as possible. A widely used mode of assisted spontaneous breathing is patient-triggered inspiratory pressure support (IPS). We investigated 11 patients with ARI during weaning from mechanical ventilation using IPS and found that in 9 of these patients, desynchronization between patient and ventilator occurred, ie, that the ventilator did not detect and support all the patients' breathing efforts. Five of these 9 patients displayed severe desynchronization lasting at least 5 min and with less than half of all breathing efforts being supported by the ventilator. We present the analysis of gas flow, volume, esophageal pressure, airway pressure, and tracheal pressure of 1 patient with ARI displaying desynchronization under IPS. Our results imply that desynchronization can occur due to the following: (1) inspiratory response delays caused by the inspiratory triggering mechanisms and the demand flow characteristics of the ventilator; (2) a mismatch between the patient's completion of the inspiration effort and the ventilator's criterion for terminating pressure support; and (3) restriction of expiration due to resistance from patient's airways, endotracheal tube, and expiratory valve. From our analysis, we have made proposals for reducing desynchronization in clinical practice.

Response of ventilator-dependent patients to different levels of pressure support and proportional assist.

Giannouli E, Webster K, Roberts D, Younes M. Response of ventilator-dependent patients to different levels of pressure support and proportional assist. Am J Respir Crit Care Med. 1999;159(6):1716-1725. doi:10.1164/ajrccm.159.6.9704025

The ventilator's response to the patient's effort is quite different in proportional assist ventilation (PAV) and pressure support ventilation (PSV). We wished to determine whether this results in different ventilatory and breathing pattern responses to alterations in level of support and, if so, whether there are any gas exchange consequences. Fourteen patients were studied. Average elastance (E) was 22.8 (range, 14 -36) cm H2O/L and average resistance (R) was 15. 7 (range, 9-21) cm H2O/L/s. The highest PSV support (PSVmax) was that associated with a tidal volume (VT) of 10 ml/kg (20.4 +/- 3.2 cm H2O), and the highest level of PAV assist (PAVmax) was 78 +/- 7% of E and 76 +/- 7% of R. Level of assist was decreased in steps to the lowest tolerable level (PSVmin, PAVmin). Minute ventilation, VT, ventilator rate (RRvent), and arterial gas tensions were measured at each level. We also determined the patient's respiratory rate (RRpat) by adding the number of ineffective efforts (DeltaRR) to RRvent. There was no difference between PSVmin and PAVmin in any of the variables. At PSVmax, VT was significantly higher (0.90 +/- 0.30 versus 0.51 +/- 0.16 L) and RRvent was significantly lower (13.2 +/- 3.9 versus 27.6 +/- 10.5 min-1) than at PAVmax. The difference in RRvent was largely related to a progressive increase in ineffective efforts on PSV as level increased (DeltaRR 12.1 +/- 10.1 vs 1.4 +/- 2.1 with PAVmax); there was no significant difference in RRpat. The differences in breathing pattern had no consequence on arterial blood gas tensions. We conclude that substantial differences in breathing pattern may occur between PSV and PAV and that these are largely artifactual and related to different patient-ventilator interactions.

Efficacy of ventilator waveforms observation in detecting patient-ventilator asynchrony.

Colombo D, Cammarota G, Alemani M, et al. Efficacy of ventilator waveforms observation in detecting patient-ventilator asynchrony. Crit Care Med. 2011;39(11):2452-2457. doi:10.1097/CCM.0b013e318225753c



OBJECTIVES

The value of visual inspection of ventilator waveforms in detecting patient-ventilator asynchronies in the intensive care unit has never been systematically evaluated. This study aims to assess intensive care unit physicians' ability to identify patient-ventilator asynchronies through ventilator waveforms.

DESIGN

Prospective observational study.

SETTING

Intensive care unit of a University Hospital.

PATIENTS

Twenty-four patients receiving mechanical ventilation for acute respiratory failure.

INTERVENTION

Forty-three 5-min reports displaying flow-time and airway pressure-time tracings were evaluated by 10 expert and 10 nonexpert, i.e., residents, intensive care unit physicians. The asynchronies identified by experts and nonexperts were compared with those ascertained by three independent examiners who evaluated the same reports displaying, additionally, tracings of diaphragm electrical activity.

MEASUREMENTS AND MAIN RESULTS

Data were examined according to both breath-by-breath analysis and overall report analysis. Sensitivity, specificity, and positive and negative predictive values were determined. Sensitivity and positive predictive value were very low with breath-by-breath analysis (22% and 32%, respectively) and fairly increased with report analysis (55% and 44%, respectively). Conversely, specificity and negative predictive value were high with breath-by-breath analysis (91% and 86%, respectively) and slightly lower with report analysis (76% and 82%, respectively). Sensitivity was significantly higher for experts than for nonexperts for breath-by-breath analysis (28% vs. 16%, p < .05), but not for report analysis (63% vs. 46%, p = .15). The prevalence of asynchronies increased at higher ventilator assistance and tidal volumes (p < .001 for both), whereas it decreased at higher respiratory rates and diaphragm electrical activity (p < .001 for both). At higher prevalence, sensitivity decreased significantly (p < .001).

CONCLUSIONS

The ability of intensive care unit physicians to recognize patient-ventilator asynchronies was overall quite low and decreased at higher prevalence; expertise significantly increased sensitivity for breath-by-breath analysis, whereas it only produced a trend toward improvement for report analysis.

Timing of inspiratory muscle activity detected from airway pressure and flow during pressure support ventilation: the waveform method.

Mojoli F, Pozzi M, Orlando A, et al. Timing of inspiratory muscle activity detected from airway pressure and flow during pressure support ventilation: the waveform method. Crit Care. 2022;26(1):32. Published 2022 Jan 30. doi:10.1186/s13054-022-03895-4



BACKGROUND

Whether respiratory efforts and their timing can be reliably detected during pressure support ventilation using standard ventilator waveforms is unclear. This would give the opportunity to assess and improve patient-ventilator interaction without the need of special equipment.

METHODS

In 16 patients under invasive pressure support ventilation, flow and pressure waveforms were obtained from proximal sensors and analyzed by three trained physicians and one resident to assess patient's spontaneous activity. A systematic method (the waveform method) based on explicit rules was adopted. Esophageal pressure tracings were analyzed independently and used as reference. Breaths were classified as assisted or auto-triggered, double-triggered or ineffective. For assisted breaths, trigger delay, early and late cycling (minor asynchronies) were diagnosed. The percentage of breaths with major asynchronies (asynchrony index) and total asynchrony time were computed.

RESULTS

Out of 4426 analyzed breaths, 94.1% (70.4-99.4) were assisted, 0.0% (0.0-0.2) auto-triggered and 5.8% (0.4-29.6) ineffective. Asynchrony index was 5.9% (0.6-29.6). Total asynchrony time represented 22.4% (16.3-30.1) of recording time and was mainly due to minor asynchronies. Applying the waveform method resulted in an inter-operator agreement of 0.99 (0.98-0.99); 99.5% of efforts were detected on waveforms and agreement with the reference in detecting major asynchronies was 0.99 (0.98-0.99). Timing of respiratory efforts was accurately detected on waveforms: AUC for trigger delay, cycling delay and early cycling was 0.865 (0.853-0.876), 0.903 (0.892-0.914) and 0.983 (0.970-0.991), respectively.

CONCLUSIONS

Ventilator waveforms can be used alone to reliably assess patient's spontaneous activity and patient-ventilator interaction provided that a systematic method is adopted.

Ability of ICU Health-Care Professionals to Identify Patient-Ventilator Asynchrony Using Waveform Analysis.

Ramirez II, Arellano DH, Adasme RS, et al. Ability of ICU Health-Care Professionals to Identify Patient-Ventilator Asynchrony Using Waveform Analysis. Respir Care. 2017;62(2):144-149. doi:10.4187/respcare.04750



BACKGROUND

Waveform analysis by visual inspection can be a reliable, noninvasive, and useful tool for detecting patient-ventilator asynchrony. However, it is a skill that requires a properly trained professional.

METHODS

This observational study was conducted in 17 urban ICUs. Health-care professionals (HCPs) working in these ICUs were asked to recognize different types of asynchrony shown in 3 evaluation videos. The health-care professionals were categorized according to years of experience, prior training in mechanical ventilation, profession, and number of asynchronies identified correctly.

RESULTS

A total of 366 HCPs were evaluated. Statistically significant differences were found when HCPs with and without prior training in mechanical ventilation (trained vs non-trained HCPs) were compared according to the number of asynchronies detected correctly (of the HCPs who identified 3 asynchronies, 63 [81%] trained vs 15 [19%] non-trained, P < .001; 2 asynchronies, 72 [65%] trained vs 39 [35%] non-trained, P = .034; 1 asynchrony, 55 [47%] trained vs 61 [53%] non-trained, P = .02; 0 asynchronies, 17 [28%] trained vs 44 [72%] non-trained, P < .001). HCPs who had prior training in mechanical ventilation also increased, nearly 4-fold, their odds of identifying ≥2 asynchronies correctly (odds ratio 3.67, 95% CI 1.93-6.96, P < .001). However, neither years of experience nor profession were associated with the ability of HCPs to identify asynchrony.

CONCLUSIONS

HCPs who have specific training in mechanical ventilation increase their ability to identify asynchrony using waveform analysis. Neither experience nor profession proved to be a relevant factor to identify asynchrony correctly using waveform analysis.

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