Assessment of interchangeability rate between 2 methods of measurements: An example with a cardiac output comparison study

Estimation of cardiac output variations induced by hemodynamic interventions using multi-beat analysis of arterial waveform: a comparative off-line study with transesophageal Doppler method during non-cardiac surgery

Multi-beat analysis (MBA) of the radial arterial pressure (AP) waveform is a new method that may improve cardiac output (CO) estimation via modelling of the confounding arterial wave reflection. We evaluated the precision and accuracy using the trending ability of the MBA method to estimate absolute CO and variations (ΔCO) during hemodynamic challenges. We reviewed the hemodynamic challenges (fluid challenge or vasopressors) performed when intra-operative hypotension occurred during non-cardiac surgery. The CO was calculated offline using transesophageal Doppler (TED) waveform (COTED) or via application of the MBA algorithm onto the AP waveform (COMBA) before and after hemodynamic challenges. We evaluated the precision and the accuracy according to the Bland & Altman method. We also assessed the trending ability of the MBA by evaluating the percentage of concordance with 15% exclusion zone between ΔCOMBA and ΔCOTED. A non-inferiority margin was set at 87.5%. Among the 58 patients included, 23 (40%) received at least 1 fluid challenge, and 46 (81%) received at least 1 bolus of vasopressors. Before treatment, the COTED was 5.3 (IQR [4.1-8.1]) l min-1, and the COMBA was 4.1 (IQR [3-5.4]) l min-1. The agreement between COTED and COMBA was poor with a 70% percentage error. The bias and lower and upper limits of agreement between COTED and COMBA were 0.9 (CI95 = 0.82 to 1.07) l min-1, -2.8 (CI95 = -2.71 to-2.96) l min-1 and 4.7 (CI95 = 4.61 to 4.86) l min-1, respectively. After hemodynamic challenge, the percentage of concordance (PC) with 15% exclusion zone for ΔCO was 93 (CI97.5 = 90 to 97)%. In this retrospective offline analysis, the accuracy, limits of agreements and percentage error between TED and MBA for the absolute estimation of CO were poor, but the MBA could adequately track induced CO variations measured by TED. The MBA needs further evaluation in prospective studies to confirm those results in clinical practice conditions.

Cardiac Output Determination in Precapillary Pulmonary Hypertension: A Systematic Review

BACKGROUND

Cardiac output determination is essential in precapillary pulmonary hypertension. While direct Fick is the gold standard, thermodilution is commonly used as the reference method. Moving to noninvasive methods would be highly beneficial for patients, avoiding repetitive invasive assessments. This systematic review followed 3 objectives: (1) assessing the validity of indirect Fick and thermodilution in precapillary pulmonary hypertension, (2) assessing the interchangeability of noninvasive cardiac output measurement methods against reference methods in precapillary pulmonary hypertension, and (3) detecting methodological heterogeneity in the included studies.

METHODS

We systematically reviewed the literature using medical databases and following PRISMA guidelines. We included articles comparing an invasive or noninvasive cardiac output measurement method with thermodilution or direct Fick in precapillary pulmonary hypertension patients. Cutoffs of limits of agreement and percentage error derived from the Bland and Altman graph were used to accept interchangeability. To study methodological heterogeneity, we extracted 9 quality criteria from all studies.

RESULTS

Eleven studies were included. None reached the suggested interchangeability criteria. The median number of the 9 assessed quality criteria was 2 with interquartile range (0-4).

CONCLUSIONS

Further studies evaluating the reliability of thermodilution and the consequences of its use in precapillary pulmonary hypertension patients are necessary. No evidence supports the use of indirect Fick in precapillary pulmonary hypertension. The studied noninvasive methods could not be considered interchangeable with invasive methods. A robust methodology should be used to draw sensible conclusions.

Transpulmonary thermodilution in patients treated with veno-venous extracorporeal membrane oxygenation

BACKGROUND

We tested the effect of different blood flow levels in the extracorporeal circuit on the measurements of cardiac stroke volume (SV), global end-diastolic volume index (GEDVI) and extravascular lung water index derived from transpulmonary thermodilution (TPTD) in 20 patients with severe acute respiratory distress syndrome (ARDS) treated with veno-venous extracorporeal membrane oxygenation (ECMO).

METHODS

Comparative SV measurements with transesophageal echocardiography and TPTD were performed at least 5 times during the treatment of the patients. The data were interpreted with a Bland-Altman analysis corrected for repeated measurements. The interchangeability between both measurement modalities was calculated and the effects of extracorporeal blood flow on SV measurements with TPTD was analysed with a linear mixed effect model. GEDVI and EVLWI measurements were performed immediately before the termination of the ECMO therapy at a blood flow of 6 l/min, 4 l/min and 2 l/min and after the disconnection of the circuit in 7 patients.

RESULTS

170 pairs of comparative SV measurements were analysed. Average difference between the two modalities (bias) was 0.28 ml with an upper level of agreement of 40 ml and a lower level of agreement of -39 ml within a 95% confidence interval and an overall interchangeability rate between TPTD and Echo of 64%. ECMO blood flow did not influence the mean bias between Echo and TPTD (0.03 ml per l/min of ECMO blood flow; p = 0.992; CI - 6.74 to 6.81). GEDVI measurement was not significantly influenced by the blood flow in the ECMO circuit, whereas EVLWI differed at a blood flow of 6 l/min compared to no ECMO flow (25.9 ± 10.1 vs. 11.0 ± 4.2 ml/kg, p = 0.0035).

CONCLUSIONS

Irrespectively of an established ECMO therapy, comparative SV measurements with Echo and TPTD are not interchangeable. Such caveats also apply to the interpretation of EVLWI, especially with a high blood flow in the extracorporeal circulation. In such situations, the clinician should rely on other methods of evaluation of the amount of lung oedema with the haemodynamic situation, vasopressor support and cumulative fluid balance in mind.

TRIAL REGISTRATION

German Clinical Trials Register (DRKS00021050). Registered 03/30/2020 https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00017237.

Four different methods of measuring cardiac index during cytoreductive surgery and hyperthermic intraperitoneal chemotherapy

Background

Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) are high-risk extensive abdominal surgery. During high-risk surgery, less invasive methods for cardiac index (CI) measurement have been widely used in operating theater. We investigated the accuracy of CI derived from different methods (FroTrac, ProAQT, ClearSight, and arterial pressure waveform analysis [APWA], from PICCO) and compared them to transpulmonary thermodilution (TPTD) during CRS and HIPEC in the operative room and intensive care unit (ICU).

Methods

Twenty-five patients scheduled for CRS-HIPEC were enrolled. During nine predefined time-points, simultaneous hemodynamic measurements were performed in the operating room and ICU. Absolute and relative changes of CI were analyzed using a Bland-Altman plot, four-quadrant plot, and interchangeability.

Results

The mean bias was −0.1 L/min/m² for ClearSight, ProAQT, and APWA and was −0.2 L/min/m² for FloTrac compared with TPTD. All devices had large limits of agreement (LoA). The percentage of errors and interchangeabilities for ClearSight, FloTrac, ProAQT, and APWA were 50%, 50%, 54%, 36% and 36%, 47%, 40%, 72%, respectively. Trending capabilities expressed as concordance using clinically significant CI changes were −7º ± 39º, −19º ± 38º, −13º ± 41º, and −15º ± 39º. Interchangeability in trending showed low percentages of interchangeable and gray zone data pairs for all devices.

Conclusions

During CRS-HIPEC, ClearSight, FloTrac and ProAQT systems were not able to reliably measure CI compared to TPTD. Reproducibility of changes over time using concordance, angular bias, radial LoA, and interchangeability in trending of all devices was unsatisfactory.

Interchangeability between two breath-by-breath O2 uptake calculation algorithms in asthmatic and healthy volunteers

INTRODUCTION

The interchangeability analysis has been recently proposed to objectively assess whether a newly developed measurement tool can substitute the older ones; this analysis assumes that the measures yielded by the compared tools should differ less than a maximum acceptable value. We aimed to assess the interchangeability rate (IR) of the breath-by-breath O₂ uptake data calculated with the "Independent breath" (IND) and the "Expiration-only" (EXP) algorithms.

METHODS

Oxygen, carbon dioxide fractions, and ventilatory flow were recorded continuously over 26 min in 18 asthmatic and 20 well-matched healthy volunteers at rest, during cycling, and recovery; oxygen uptake (V'O₂) was calculated with the two algorithms under comparison. Coefficients of variation (CVs) of all the steady-state condition were modeled as a function of the average V'O₂ values and IR was calculated accordingly.

RESULTS

CVs were significantly greater in the asthmatic volunteers (F = 5.97, p < 0.05), being lower for IND compared to EXP (F > 7.04, p < 0.02). CVs decreased as a function of the reciprocal of the square root of the average V'O₂. The IR, calculated on the basis of this relationship, was not significantly different in the two groups of volunteers (F = 0.77, p = 0.385); taking as reference method the IND, or EXP algorithms, the IR values were significantly different (F = 58.6, p < 0.001), amounting to 97.4 ± 2.2% or to 98.2 ± 1.7%, respectively.

CONCLUSION

The relative noise of V'O₂ was greater in the asthmatic volunteers compared to the healthy ones and was lower for IND compared to EXP. The interchangeability analysis suggested that IND might be a better substitute for EXP than the opposite.

Best practice & research clinical anaesthesiology: Advances in haemodynamic monitoring for the perioperative patient: Perioperative cardiac output monitoring

Less invasive or even completely non-invasive haemodynamic monitoring technologies have evolved during the last decades. Even established, invasive devices such as the pulmonary artery catheter and transpulmonary thermodilution have still an evidence-based place in the perioperative setting, albeit only in special patient populations. Accumulating evidence suggests to use continuous haemodynamic monitoring, especially flow-based variables such as stroke volume or cardiac output to prevent occult hypoperfusion and, consequently, decrease morbidity and mortality perioperatively. However, there is still a substantial gap between evidence provided by randomised trials and the implementation of haemodynamic monitoring in daily clinical routine. Given the fact that perioperative morbidity and mortality are higher than anticipated and anaesthesiologists are in charge to deal with this problem, the recent advances in minimally invasive and non-invasive monitoring technologies may facilitate more widespread use in the operating theatre, as in addition to costs, the degree of invasiveness of any monitoring tool determines the frequency of its application, at least perioperatively. This review covers the currently available invasive, non-invasive and minimally invasive techniques and devices and addresses their indications and limitations.

Noninvasive continuous arterial pressure monitoring with Clearsight during awake carotid endarterectomy: A prospective observational study

BACKGROUND

Continuous noninvasive blood pressure (CNBP) measurement using the volume-clamp method is a less invasive alternative compared with invasive intra-arterial monitoring for awake patients during carotid endarterectomy (CEA) under regional anaesthesia.

OBJECTIVE

We investigated the agreement of blood pressure (BP) recorded with invasive and CNBP methods during awake CEA.

DESIGN

A prospective observational study for assessing agreement with Bland-Altman plots, agreement-tolerability indices (ATI), concordance and interchangeability.

SETTING

Azienda Ospedaliera Universitaria G. Martino, Messina, a University tertiary referral centre in Italy.

PATIENTS

In 30 consecutive patients, we recorded continuously ipsilateral invasive and noninvasive BPs, from 3 min before carotid cross-clamping to 5 min after unclamping.

MAIN OUTCOME MEASURES

Primary outcome was bias, 95% limits of agreement, ATI, concordance and interchangeability for mean arterial pressure (MAP). Secondary outcomes were agreements for systolic arterial pressure and diastolic arterial pressure. Tracking of changes was assessed with four-quadrant polar plots and the trend interchangeability method. Optimal bias was defined as 5 mmHg or less.

RESULTS

A total of 2672 invasive and CNBP paired measurements (93% of overall data) were analysed, with a median of 92 readings per patient [IQR 76 to 100]. Mean (SD) bias for MAP, systolic arterial pressure and DAP were -6.8 (6.7), -3.0 (9.7) and -9.0 (5.4) mmHg, respectively. The ATIs were 0.88, 0.95 and 0.71, respectively, where ATI of 1.0 or less and at least 2.0 defined acceptable, marginal and unacceptable agreements. The four-quadrant plot analysis for beat-to-beat differences showed concordance rates of 97.3%, 99.98% and 96.4%, respectively. Polar plot analysis showed 95% limits of agreement of -3 to 3, -2 to 2 and -2 to 2 mmHg respectively. Trend interchangeability method showed an interchangeability rate of 95% for MAP.

CONCLUSION

During CEA performed under regional anaesthesia, CNBP offers a less invasive approach for BP monitoring. We found acceptable agreement for MAP defined by an ATI of 0.88 and an excellent 95% global interchangeability rate. A suboptimal bias of 7 mmHg was found with CNBP for MAP.

Noninvasive cardiac output monitoring in a porcine model using the inspired sinewave technique: a proof-of-concept study

Background

Cardiac output (Q˙) monitoring can support the management of high-risk surgical patients, but the pulmonary artery catheterisation required by the current ‘gold standard’—bolus thermodilution (Q˙T)—has the potential to cause life-threatening complications. We present a novel noninvasive and fully automated method that uses the inspired sinewave technique to continuously monitor cardiac output (Q˙IST).

Methods

Over successive breaths the inspired nitrous oxide (N₂O) concentration was forced to oscillate sinusoidally with a fixed mean (4%), amplitude (3%), and period (60 s). Q˙IST was determined in a single-compartment tidal ventilation lung model that used the resulting amplitude/phase of the expired N₂O sinewave. The agreement and trending ability of Q˙IST were compared with Q˙T during pharmacologically induced haemodynamic changes, before and after repeated lung lavages, in eight anaesthetised pigs.

Results

Before lung lavage, changes in Q˙IST and Q˙T from baseline had a mean bias of –0.52 L min⁻¹ (95% confidence interval [CI], –0.41 to –0.63). The concordance between Q˙IST and Q˙T was 92.5% as assessed by four-quadrant analysis, and polar plot analysis revealed a mean angular bias of 5.98° (95% CI, –24.4°–36.3°). After lung lavage, concordance was slightly reduced (89.4%), and the mean angular bias widened to 21.8° (–4.2°, 47.6°). Impaired trending ability correlated with shunt fraction (r=0.79, P<0.05).

Conclusions

The inspired sinewave technique provides continuous and noninvasive monitoring of cardiac output, with a ‘marginal–good’ trending ability compared with cardiac output based on thermodilution. However, the trending ability can be reduced with increasing shunt fraction, such as in acute lung injury.