Dataset Information

Capnodynamic monitoring of lung volume and blood flow in response to increased positive end-expiratory pressure in moderate to severe COVID-19 pneumonia: an observational study.

ABSTRACT:

Background

The optimal level of positive end-expiratory pressure (PEEP) during mechanical ventilation for COVID-19 pneumonia remains debated and should ideally be guided by responses in both lung volume and perfusion. Capnodynamic monitoring allows both end-expiratory lung volume ([Formula: see text]) and effective pulmonary blood flow (EPBF) to be determined at the bedside with ongoing ventilation.

Methods

Patients with COVID-19-related moderate to severe respiratory failure underwent capnodynamic monitoring of [Formula: see text] and EPBF during a step increase in PEEP by 50% above the baseline (PEEP_low to PEEP_high). The primary outcome was a > 20 mm Hg increase in arterial oxygen tension to inspired fraction of oxygen (P/F) ratio to define responders versus non-responders. Secondary outcomes included changes in physiological dead space and correlations with independently determined recruited lung volume and the recruitment-to-inflation ratio at an instantaneous, single breath decrease in PEEP. Mixed factor ANOVA for group mean differences and correlations by Pearson's correlation coefficient are reported including their 95% confidence intervals.

Results

Of 27 patients studied, 15 responders increased the P/F ratio by 55 [24-86] mm Hg compared to 12 non-responders (p < 0.01) as PEEP_low (11 ± 2.7 cm H₂O) was increased to PEEP_high (18 ± 3.0 cm H₂O). The [Formula: see text] was 461 [82-839] ml less in responders at PEEP_low (p = 0.02) but not statistically different between groups at PEEP_high. Responders increased both [Formula: see text] and EPBF at PEEP_high (r = 0.56 [0.18-0.83], p = 0.03). In contrast, non-responders demonstrated a negative correlation (r = - 0.65 [- 0.12 to - 0.89], p = 0.02) with increased lung volume associated with decreased pulmonary perfusion. Decreased (- 0.06 [- 0.02 to - 0.09] %, p < 0.01) dead space was observed in responders. The change in [Formula: see text] correlated with both the recruited lung volume (r = 0.85 [0.69-0.93], p < 0.01) and the recruitment-to-inflation ratio (r = 0.87 [0.74-0.94], p < 0.01).

Conclusions

In mechanically ventilated patients with moderate to severe COVID-19 respiratory failure, improved oxygenation in response to increased PEEP was associated with increased end-expiratory lung volume and pulmonary perfusion. The change in end-expiratory lung volume was positively correlated with the lung volume recruited and the recruitment-to-inflation ratio. This study demonstrates the feasibility of capnodynamic monitoring to assess physiological responses to PEEP at the bedside to facilitate an individualised setting of PEEP.

Trial registration

NCT05082168 (18th October 2021).

SUBMITTER: Schulz L

PROVIDER: S-EPMC9340710 | biostudies-literature | 2022 Jul

REPOSITORIES: biostudies-literature

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Publications

Capnodynamic monitoring of lung volume and blood flow in response to increased positive end-expiratory pressure in moderate to severe COVID-19 pneumonia: an observational study.

Schulz Luis L Stewart Antony A O'Regan William W McCanny Peter P Austin Danielle D Hallback Magnus M Wallin Mats M Aneman Anders A

Critical care (London, England) 20220731 1

<h4>Background</h4>The optimal level of positive end-expiratory pressure (PEEP) during mechanical ventilation for COVID-19 pneumonia remains debated and should ideally be guided by responses in both lung volume and perfusion. Capnodynamic monitoring allows both end-expiratory lung volume ([Formula: see text]) and effective pulmonary blood flow (EPBF) to be determined at the bedside with ongoing ventilation.<h4>Methods</h4>Patients with COVID-19-related moderate to severe respiratory failure unde ...[more]

PMID: 35909174

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Project description:RationaleEnd-expiratory lung volume (EELV) is reduced in mechanically ventilated patients, especially in pathologic conditions. The resulting heterogeneous distribution of ventilation increases the risk for ventilation induced lung injury. Clinical measurement of EELV however, remains difficult.ObjectiveValidation of a novel continuous capnodynamic method based on expired carbon dioxide (CO2) kinetics for measuring EELV in mechanically ventilated critically-ill patients.MethodsProspective study of mechanically ventilated patients scheduled for a diagnostic computed tomography exploration. Comparisons were made between absolute and corrected EELVCO2 values, the latter accounting for the amount of CO2 dissolved in lung tissue, with the reference EELV measured by computed tomography (EELVCT). Uncorrected and corrected EELVCO2 was compared with total CT volume (density compartments between - 1000 and 0 Hounsfield units (HU) and functional CT volume, including density compartments of - 1000 to - 200HU eliminating regions of increased shunt. We used comparative statistics including correlations and measurement of accuracy and precision by the Bland Altman method.Measurements and main resultsOf the 46 patients included in the final analysis, 25 had a diagnosis of ARDS (24 of which COVID-19). Both EELVCT and EELVCO2 were significantly reduced (39 and 40% respectively) when compared with theoretical values of functional residual capacity (p < 0.0001). Uncorrected EELVCO2 tended to overestimate EELVCT with a correlation r2 0.58; Bias - 285 and limits of agreement (LoA) (+ 513 to - 1083; 95% CI) ml. Agreement improved for the corrected EELVCO2 to a Bias of - 23 and LoA of (+ 763 to - 716; 95% CI) ml. The best agreement of the method was obtained by comparison of corrected EELVCO2 with functional EELVCT with a r2 of 0.59; Bias - 2.75 (+ 755 to - 761; 95% CI) ml. We did not observe major differences in the performance of the method between ARDS (most of them COVID related) and non-ARDS patients.ConclusionIn this first validation in critically ill patients, the capnodynamic method provided good estimates of both total and functional EELV. Bias improved after correcting EELVCO2 for extra-alveolar CO2 content when compared with CT estimated volume. If confirmed in further validations EELVCO2 may become an attractive monitoring option for continuously monitor EELV in critically ill mechanically ventilated patients.Trial registrationclinicaltrials.gov (NCT04045262).

Project description:BackgroundIn acute respiratory distress syndrome (ARDS), response to positive end-expiratory pressure (PEEP) is variable according to different degrees of lung recruitability. The search for a tool to individualize PEEP based on patients' individual response is warranted. End-expiratory lung volume (EELV) assessment by nitrogen washing-washout aids bedside estimation of PEEP-induced alveolar recruitment and may therefore help titrate PEEP on patient's individual recruitability. We designed a randomized trial to test whether an individualized PEEP setting protocol driven by EELV measurement may improve a composite clinical outcome in patients with moderate-to-severe ARDS (IPERPEEP trial).MethodsIPERPEEP is an open-label, multicenter, randomized trial that will be conducted in 10 intensive care units in Italy and will enroll 132 ARDS patients showing PaO2/FiO2 ratio ≤ 150 mmHg within 24 h from endotracheal intubation while on mechanical ventilation with PEEP 5 cmH2O. To standardize lung volumes at study initiation, all patients will undergo mechanical ventilation with tidal volume of 6 ml/kg of predicted body weight and PEEP set to obtain a plateau pressure within 28 and 30 cmH2O for 30 min (EXPRESS PEEP). Afterwards, a 5-step decremental PEEP trial will be conducted (EXPRESS PEEP to PEEP 5 cmH2O), and EELV will be measured at each step. Recruitment-to-inflation ratio will be calculated for each PEEP range from EELV difference. Patients will be then randomized to receive mechanical ventilation with PEEP set according to the optimal recruitment observed in the PEEP trial (IPERPEEP arm) trial or to achieve a plateau pressure of 28-30 cmH2O (control arm, EXPRESS strategy). In both groups, tidal volume size, use of prone positioning and neuromuscular blocking agents, and weaning from PEEP and from mechanical ventilation will be standardized. The primary endpoint of the study is a composite clinical outcome incorporating in-ICU mortality, 60-day ventilator-free days, and serum interleukin-6 concentration over the course of the initial 72 h of treatment.DiscussionThe IPERPEEP study is a randomized trial powered to elucidate whether an individualized PEEP setting protocol based on bedside assessment of lung recruitability can improve a composite clinical outcome during moderate-to-severe ARDS.Trial registrationClinicalTrials.gov NCT04012073 . Registered 9 July 2019.

Project description:BackgroundThe study objective was to compare titration of positive end-expiratory pressure (PEEP) with electrical impedance tomography (EIT) and with ventilator-embedded pressure-volume loop in severe acute respiratory distress syndrome (ARDS).MethodsWe have designed a prospective study with historical control group. Twenty-four severe ARDS patients (arterial oxygen partial pressure to fractional inspired oxygen ratio, PaO2/FiO2 < 100 mmHg) were included in the EIT group and examined prospectively. Data from another 31 severe ARDS patients were evaluated retrospectively (control group). All patients were receiving medical care under identical general support guidelines and protective mechanical ventilation. The PEEP level selected in the EIT group was the intercept point of cumulated collapse and overdistension percentages curves. In the control group, optimal PEEP was selected 2 cmH2O above the lower inflection point on the static pressure-volume curve.ResultsPatients in the EIT group were younger (P < 0.05), and their mean plateau pressure was 1.5 cmH2O higher (P < 0.01). No differences in other baseline parameters such as APACHE II score, PaO2/FiO2, initial PEEP, driving pressure, tidal volume, and respiratory system compliance were found. Two hours after the first PEEP titration, significantly higher PEEP, compliance, and lower driving pressure were found in the EIT group (P < 0.01). Hospital survival rates were 66.7% (16 of 24 patients) in the EIT group and 48.4% (15 of 31) in the control group. Identical rates were found regarding the weaning success rate: 66.7% in the EIT group and 48.4% in the control group.ConclusionIn severe ARDS patients, it was feasible and safe to guide PEEP titration with EIT at the bedside. As compared with pressure-volume curve, the EIT-guided PEEP titration may be associated with improved oxygenation, compliance, driving pressure, and weaning success rate. The findings encourage further randomized control study with a larger sample size and potentially less bias in the baseline data. Trial Registration NCT03112512.

Project description:IntroductionOne potential mechanism of ventilator-induced lung injury (VILI) is due to shear stresses associated with alveolar instability (recruitment/derecruitment). It has been postulated that the optimal combination of tidal volume (Vt) and positive end-expiratory pressure (PEEP) stabilizes alveoli, thus diminishing recruitment/derecruitment and reducing VILI. In this study we directly visualized the effect of Vt and PEEP on alveolar mechanics and correlated alveolar stability with lung injury.MethodsIn vivo microscopy was utilized in a surfactant deactivation porcine ARDS model to observe the effects of Vt and PEEP on alveolar mechanics. In phase I (n = 3), nine combinations of Vt and PEEP were evaluated to determine which combination resulted in the most and least alveolar instability. In phase II (n = 6), data from phase I were utilized to separate animals into two groups based on the combination of Vt and PEEP that caused the most alveolar stability (high Vt [15 cc/kg] plus low PEEP [5 cmH2O]) and least alveolar stability (low Vt [6 cc/kg] and plus PEEP [20 cmH2O]). The animals were ventilated for three hours following lung injury, with in vivo alveolar stability measured and VILI assessed by lung function, blood gases, morphometrically, and by changes in inflammatory mediators.ResultsHigh Vt/low PEEP resulted in the most alveolar instability and lung injury, as indicated by lung function and morphometric analysis of lung tissue. Low Vt/high PEEP stabilized alveoli, improved oxygenation, and reduced lung injury. There were no significant differences between groups in plasma or bronchoalveolar lavage cytokines or proteases.ConclusionA ventilatory strategy employing high Vt and low PEEP causes alveolar instability, and to our knowledge this is the first study to confirm this finding by direct visualization. These studies demonstrate that low Vt and high PEEP work synergistically to stabilize alveoli, although increased PEEP is more effective at stabilizing alveoli than reduced Vt. In this animal model of ARDS, alveolar instability results in lung injury (VILI) with minimal changes in plasma and bronchoalveolar lavage cytokines and proteases. This suggests that the mechanism of lung injury in the high Vt/low PEEP group was mechanical, not inflammatory in nature.

Project description:PurposeRecruitment of lung volume is often cited as the reason for using positive end-expiratory pressure (PEEP) in acute respiratory distress syndrome (ARDS) patients. We performed a systematic review on PEEP-induced recruited lung volume measured from inspiratory volume-pressure (VP) curves in ARDS patients to assess the prevalence of patients with PEEP-induced recruited lung volume and the mortality in recruiters and non-recruiters.MethodsWe conducted a systematic search of PubMed to identify studies including ARDS patients in which the intervention of an increase in PEEP was accompanied by measurement of the recruited volume (Vrec increase versus no increase) using the VP curve in order to assess the relation between Vrec and mortality at ICU discharge. We first analysed the pooled data from the papers identified and then analysed individual patient level data received from the authors via personal contact. The risk of bias of the included papers was assessed using the quality in prognosis studies tool and the certainty of the evidence regarding the relationship of mortality to Vrec by the GRADE approach. Recruiters were defined as patients with a Vrec > 150 ml. A random effects model was used for the pooled data. Multivariable logistic regression analysis was used for individual patient data.ResultsWe identified 16 papers with a total of 308 patients for the pooled data meta-analysis and 14 papers with a total of 384 patients for the individual data analysis. The quality of the articles was moderate. In the pooled data, the prevalence of recruiters was 74% and the mortality was not significantly different between recruiters and non-recruiters (relative risk 1.20 [95% confidence intervals 0.88-1.63]). The certainty of the evidence regarding this association was very low and publication bias evident. In the individual data, the prevalence of recruiters was 70%. In the multivariable logistic regression, Vrec was not associated with mortality but Simplified Acute Physiology Score II and driving pressure at PEEP of 5 cmH2O were.ConclusionAfter a PEEP increment, most patients are recruiters. Vrec was not associated with ICU mortality. The presence of similar findings in the individual patient level analysis and the driving pressure at PEEP of 5 cmH2O was associated with mortality as previously reported validate our findings. Publication bias and the lack of prospective studies suggest more research is required.

Project description:BackgroundEsophageal pressure (Pes) has been used as a surrogate of pleural pressure (Ppl) to titrate positive end-expiratory pressure (PEEP) in acute respiratory distress syndrome (ARDS) patients. The relationship between Pes and PEEP remains undetermined.MethodsA gastric tube with a balloon catheter was inserted to monitor Pes in moderate to severe ARDS patients who underwent invasive mechanical ventilation. To assess the end-expiratory Pes response (ΔPes) to PEEP changes (ΔPEEP), the PEEP level was decreased and increased subsequently (with an average change of 3 cmH2O). The patients underwent the following two series of PEEP adjustment: (I) from PEEP-3 cmH2O to PEEPbaseline; and (II) from PEEPbaseline to PEEP+3 cmH2O. The patients were classified as "PEEP-dependent type" if they had ΔPes ≥30% ΔPEEP and were otherwise classified as "PEEP-independent type" (ΔPes <30% ΔPEEP in any series).ResultsIn total, 54 series of PEEP adjustments were performed in 18 ARDS patients. Of these patients, 12 were classified as PEEP-dependent type, and six were classified as PEEP-independent type. During the PEEP adjustment, end-expiratory Pes changed significantly in the PEEP-dependent patients, who had a Pes of 10.8 (7.9, 12.3), 12.5 (10.5, 14.9), and 14.5 (13.1, 18.3) cmH2O at PEEP-3 cmH2O, PEEPbaseline, and PEEP+3 cmH2O, respectively (median and quartiles; P<0.0001), while end-expiratory transpulmonary pressure (PL) was maintained at an optimal range [-0.1 (-0.7, 0.4), 0.1 (-0.6, 0.5), and 0.3 (-0.3, 0.7) cmH2O, respectively]. In the PEEP-independent patients, the Pes remained unchanged, with a Pes of 15.4 (11.4, 17.8), 15.5 (11.6, 17.8), and 15.4 (11.7, 18.30) cmH2O at each of the three PEEP levels, respectively. Meanwhile, end-expiratory PL significantly improved [from -5.5 (-8.5, -3.4) at PEEP-3 cmH2O to -2.5 (-5.0, -1.6) at PEEPbaseline to -0.5 (-1.8, 0.3) at PEEP+3 cmH2O; P<0.01].ConclusionsTwo types of Pes phenotypes were identified according to the ΔPes to ΔPEEP. The underlying mechanisms and implications for clinical practice require further exploration.

Dataset Information

Capnodynamic monitoring of lung volume and blood flow in response to increased positive end-expiratory pressure in moderate to severe COVID-19 pneumonia: an observational study.

Background

Methods

Results

Conclusions

Trial registration

Publications

Capnodynamic monitoring of lung volume and blood flow in response to increased positive end-expiratory pressure in moderate to severe COVID-19 pneumonia: an observational study.

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