The effect of inspiratory rise time on mechanical power calculations in pressure control ventilation: dynamic approach.

BACKGROUND: Mechanical power may serve as a valuable parameter for predicting ventilation-induced injury in mechanically ventilated patients. Over time, several equations have been developed to calculate power in both volume control ventilation (VCV) and pressure control ventilation (PCV). Among these equations, the linear model mechanical power equation (MPLM) closely approximates the reference method when applied in PCV. The dynamic mechanical power equation (MPdyn) computes power by utilizing the ventilatory work of breathing parameter (WOBv), which is automatically measured by the mechanical ventilator. In our study, conducted in patients with Covid-19 Acute Respiratory Distress Syndrome (C-ARDS), we calculated mechanical power using both the MPLM and MPdyn equations, employing different inspiratory rise times (Tslope) at intervals of 5%, ranging from 5 to 20% and compared the obtained results. RESULTS: In our analysis, we used univariate linear regression at both I:E ratios of 1:2 and 1:1, considering all Tslope values. These analyses revealed that the MPdyn and MPLM equations exhibited strong correlations, with R2 values exceeding 0.96. Furthermore, our Bland-Altman analysis, which compared the power values derived from the MPdyn and MPLM equations for patient averages and all measurements, revealed a mean difference of -0.42 ± 0.41 J/min (equivalent to 2.6% ± 2.3%, p < 0.0001) and -0.39 ± 0.57 J/min (equivalent to 3.6% ± 3.5%, p < 0.0001), respectively. While there was a statistically significant difference between the equations in both absolute value and relative proportion, this difference was not considered clinically relevant. Additionally, we observed that each 5% increase in Tslope time corresponded to a decrease in mechanical power values by approximately 1 J/min. CONCLUSIONS: The differences between mechanical power values calculated using the MPdyn and MPLM equations at various Tslope durations were determined to lack clinical significance. Consequently, for practical and continuous mechanical power estimation in Pressure-Controlled Ventilation (PCV) mode, the MPdyn equation presents itself as a viable option. It is important to note that as Tslope times increased, the calculated mechanical power exhibited a clinically relevant decrease.

Simplified calculation of mechanical power for pressure controlled ventilation in Covid-19 ARDS patients.

BACKGROUND: Mechanical power (MP) is a promising tool for guidance of lung protective ventilation. Different equations have been proposed to calculate MP in pressure control ventilation (PCV). The aim of this study is to introduce an easy to use MP equation MPpcv(m-simpl) and compare it to an equation proposed by Van der Meijden et al. (MPpcv) which considered as the reference equation in PCV. METHODS: Ventilatory parameters of 206 Covid-19 ARDS patients recorded between 24-72 hours after admission to intensive care unit. The PCV data from these patients were retrospectively investigated. MP in PCV was calculated with a modified equation (MPpcv(m-simpl)) derived from the equation (MPpcv) of Van der Meijden et al.: 0.098xRRx∆Vx(PEEP+∆Pinsp - 1). The results from MPpcv(slope), MPpcv(simpl), and MPpcv(m-simpl) were compared to MPpcv at 15 cmH2O ∙ s/L inspiratory resistance levels by univariable regression and Bland-Altman analysis. RESULTS: Inspiratory resistance levels at 15 cmH2O s/L was found to be correlated between the power values calculated by MPpcv(simpl)/MPpcv(m-simpl) and the MPpcv(slope)/MPpcv based on univariable logistic regression (R2≥98) analyses. In the comparison of all patients average MP values computed by the MPpcv(m-simpl) equation and the MPpcv reference equation. Bland-Altman analysis mean difference and p values at 15 cmH2O s/L inspiratory resistance values (J/min) were found to be MPpcv(m-simpl) vs MPpcv=-0,04 (P=0.014); MPpcv(slope) vs. MPpcv=0.63 (P<0.0001); MPpcv(simpl) vs. MPpcv=0.64 J/min (P<0.0001), respectively. CONCLUSIONS: The results of this study confirmed that the MPpcv(m-simpl) equation can be used easily to calculate MP at bedside in pressure control ventilated COVID-19 ARDS patients.

Comparison of Respiratory and Hemodynamic Parameters of COVID-19 and Non-COVID-19 ARDS Patients.

BACKGROUND: COVID-19 can cause a clinical spectrum from asymptomatic disease to life-threatening respiratory failure and acute respiratory distress syndrome (ARDS). There is an ongoing discussion whether the clinical presentation and ventilatory parameters are the same as typical ARDS or not. There is no clear understanding of how the hemodynamic parameters have been affected in COVID-19 ARDS patients. We aimed to compare hemodynamic and respiratory parameters of moderate and severe COVID-19 and non-COVID-19 ARDS patients. These patients were monitored with an advanced hemodynamic measurement system by the transpulmonary thermodilution method in prone and supine positions. PATIENTS AND METHODS: Data of 17 patients diagnosed with COVID-19 and 16 patients diagnosed with other types of diseases with moderate and severe ARDS, mechanically ventilated, placed in a prone position, had advanced hemodynamic measurements with PiCCO, and stayed in the intensive care unit for more than a week were analyzed retrospectively. Patient characteristics and arterial blood gases analysis recorded at admission and respiratory and advanced hemodynamic parameters during the first week were compared in prone and supine positions. RESULTS: No difference was observed in the respiratory parameters including respiratory system compliance between COVID-19 and non-COVD-19 patients in prone and supine positions. In comparison of advanced hemodynamic parameters in the first week of intensive care, the extravascular lung water and pulmonary vascular permeability indexes measured in supine position of COVID-19 ARDS patients were found to be significantly higher than non-COVID-19 patients. Duration of prone position was significantly longer in patients diagnosed with COVID-19 ARDS. CONCLUSIONS: The results of this study suggested that COVID-19 ARDS is a variant of typical ARDS with a different pathophysiology. HOW TO CITE THIS ARTICLE: Asar S, Acicbe Ö, Sabaz MS, Tontu F, Canan E, Cukurova Z, et al. Comparison of Respiratory and Hemodynamic Parameters of COVID-19 and Non-COVID-19 ARDS Patients. Indian J Crit Care Med 2021;25(6):704-708.

Bedside dynamic calculation of mechanical power: A validation study.

PURPOSE: To develop an equation to calculate the bedside dynamic mechanical power (MPdyn) for modern ventilators using the Work of Breathing ventilator (WOBv) parameter. MATERIALS AND METHODS: We developed an equation based on mechanical power values, which is equal to WOBv x minute volume. To measure mechanical power with this equation forty adult patients, hospitalized with the diagnosis of Acute Respiratory Distress Syndrome and underwent invasive mechanical ventilation, were used. To be able compare our results with Gattinoni's standart mechanical power equation (MPstd) the contribution of the PEEP was included in our equation. Then results obtained from MPdyn and MPstd were compared using univariable regression and Bland-Altman analysis. This comparison was performed at different I:E ratios, PEEP levels and tidal volumes. RESULTS: Analysis of the results for each condition showed that MPdyn and MPstd equation correlated with R2 ≥ 0.98. Additionally, there was no statistically significant difference between MPdyn and MPstd for patient power means were 0.04 J/min (p = .42) using Bland-Altman analysis. CONCLUSIONS: Physicians can easily calculate mechanical power by using MPdyn at the bedside of patients on volume control mode.