Novel method of transpulmonary pressure measurement with an air-filled esophageal catheter

Background There is a strong rationale for proposing transpulmonary pressure-guided protective ventilation in acute respiratory distress syndrome. The reference esophageal balloon catheter method requires complex in vivo calibration, expertise and specific material order. A simple, inexpensive, accurate and reproducible method of measuring esophageal pressure would greatly facilitate the measure of transpulmonary pressure to individualize protective ventilation in the intensive care unit. Results We propose an air-filled esophageal catheter method without balloon, using a disposable catheter that allows reproducible esophageal pressure measurements. We use a 49-cm-long 10 Fr thin suction catheter, positioned in the lower-third of the esophagus and connected to an air-filled disposable blood pressure transducer bound to the monitor and pressurized by an air-filled infusion bag. Only simple calibration by zeroing the transducer to atmospheric pressure and unit conversion from mmHg to cmH2O are required. We compared our method with the reference balloon catheter both ex vivo, using pressure chambers, and in vivo, in 15 consecutive mechanically ventilated patients. Esophageal-to-airway pressure change ratios during the dynamic occlusion test were close to one (1.03 ± 0.19 and 1.00 ± 0.16 in the controlled and assisted modes, respectively), validating the proper esophageal positioning. The Bland–Altman analysis revealed no bias of our method compared with the reference and good precision for inspiratory, expiratory and delta esophageal pressure measurements in both the controlled (largest bias −0.5 cmH2O [95% confidence interval: −0.9; −0.1] cmH2O; largest limits of agreement −3.5 to 2.5 cmH2O) and assisted modes (largest bias −0.3 [−2.6; 2.0] cmH2O). We observed a good repeatability (intra-observer, intraclass correlation coefficient, ICC: 0.89 [0.79; 0.96]) and reproducibility (inter-observer ICC: 0.89 [0.76; 0.96]) of esophageal measurements. The direct comparison with pleural pressure in two patients and spectral analysis by Fourier transform confirmed the reliability of the air-filled catheter-derived esophageal pressure as an accurate surrogate of pleural pressure. A calculator for transpulmonary pressures is available online. Conclusions We propose a simple, minimally invasive, inexpensive and reproducible method for esophageal pressure monitoring with an air-filled esophageal catheter without balloon. It holds the promise of widespread bedside use of transpulmonary pressure-guided protective ventilation in ICU patients.

Role of Fluid and Sodium Retention in Experimental Ventilator-Induced Lung Injury

Background: Ventilator-induced lung injury (VILI) via respiratory mechanics is deeply interwoven with hemodynamic, kidney and fluid/electrolyte changes. We aimed to assess the role of positive fluid balance in the framework of ventilation-induced lung injury.Methods:Post-hoc analysis of seventy-eight pigs invasively ventilated for 48 h with mechanical power ranging from 18 to 137 J/min and divided into two groups: high vs. low pleural pressure (10.0 ± 2.8 vs. 4.4 ± 1.5 cmH2O; p < 0.01). Respiratory mechanics, hemodynamics, fluid, sodium and osmotic balances, were assessed at 0, 6, 12, 24, 48 h. Sodium distribution between intracellular, extracellular and non-osmotic sodium storage compartments was estimated assuming osmotic equilibrium. Lung weight, wet-to-dry ratios of lung, kidney, liver, bowel and muscle were measured at the end of the experiment.Results: High pleural pressure group had significant higher cardiac output (2.96 ± 0.92 vs. 3.41 ± 1.68 L/min; p < 0.01), use of norepinephrine/epinephrine (1.76 ± 3.31 vs. 5.79 ± 9.69 mcg/kg; p < 0.01) and total fluid infusions (3.06 ± 2.32 vs. 4.04 ± 3.04 L; p < 0.01). This hemodynamic status was associated with significantly increased sodium and fluid retention (at 48 h, respectively, 601.3 ± 334.7 vs. 1073.2 ± 525.9 mmol, p < 0.01; and 2.99 ± 2.54 vs. 6.66 ± 3.87 L, p < 0.01). Ten percent of the infused sodium was stored in an osmotically inactive compartment. Increasing fluid and sodium retention was positively associated with lung-weight (R2 = 0.43, p < 0.01; R2 = 0.48, p < 0.01) and with wet-to-dry ratio of the lungs (R2 = 0.14, p < 0.01; R2 = 0.18, p < 0.01) and kidneys (R2 = 0.11, p = 0.02; R2 = 0.12, p = 0.01).Conclusion: Increased mechanical power and pleural pressures dictated an increase in hemodynamic support resulting in proportionally increased sodium and fluid retention and pulmonary edema.

Pleural Manometry—Basics for Clinical Practice

Purpose of Review The aim of this paper is to present basic data on pleural manometry and to outline the advances in its use as both a research tool enabling a better understanding of pleural pathophysiology and as a clinical tool useful in management strategy planning in patients with pleural diseases. To discuss updates and current trends in the development of pleural manometry, a search of the literature on pleural manometry published in recent years was performed. Recent Findings The technique of pleural manometry has significantly evolved over the last 40 years from simple water manometers to electronic or digital devices which enable the measurement and recording of instantaneous pleural pressure. Although to date it is mainly used as a research tool, pleural manometry has the potential to be applied in clinical practice. Recent studies demonstrated that monitoring of pleural pressure changes during therapeutic thoracentesis does not seem to be helpful in predicting re-expansion pulmonary edema and procedure-related chest discomfort. On the other hand, measurement of pleural elastance plays an important role in the diagnosis of unexpandable lung in patients with malignant pleural effusion facilitating determination of the optimal management strategy. Additionally, it allows for study of newly discovered phenomena, including pleural pressure pulse assessment and the impact of continuous positive airway pressure and cough on pleural pressure. Summary Pleural manometry is an established technique of pleural pressure measurement. Despite recent advances, its role in clinical practice remains undetermined.

Estimation of change in pleural pressure in assisted and unassisted spontaneous breathing pediatric patients using fluctuation of central venous pressure: A preliminary study

Background It is important to evaluate the size of respiratory effort to prevent patient self-inflicted lung injury and ventilator-induced diaphragmatic dysfunction. Esophageal pressure (Pes) measurement is the gold standard for estimating respiratory effort, but it is complicated by technical issues. We previously reported that a change in pleural pressure (ΔPpl) could be estimated without measuring Pes using change in CVP (ΔCVP) that has been adjusted with a simple correction among mechanically ventilated, paralyzed pediatric patients. This study aimed to determine whether our method can be used to estimate ΔPpl in assisted and unassisted spontaneous breathing patients during mechanical ventilation. Methods The study included hemodynamically stable children (aged <18 years) who were mechanically ventilated, had spontaneous breathing, and had a central venous catheter and esophageal balloon catheter in place. We measured the change in Pes (ΔPes), ΔCVP, and ΔPpl that was calculated using a corrected ΔCVP (cΔCVP-derived ΔPpl) under three pressure support levels (10, 5, and 0 cmH2O). The cΔCVP-derived ΔPpl value was calculated as follows: cΔCVP-derived ΔPpl = k × ΔCVP, where k was the ratio of the change in airway pressure (ΔPaw) to the ΔCVP during airway occlusion test. Results Of the 14 patients enrolled in the study, 6 were excluded because correct positioning of the esophageal balloon could not be confirmed, leaving eight patients for analysis (mean age, 4.8 months). Three variables that reflected ΔPpl (ΔPes, ΔCVP, and cΔCVP-derived ΔPpl) were measured and yielded the following results: -6.7 ± 4.8, − -2.6 ± 1.4, and − -7.3 ± 4.5 cmH2O, respectively. The repeated measures correlation between cΔCVP-derived ΔPpl and ΔPes showed that cΔCVP-derived ΔPpl had good correlation with ΔPes (r = 0.84, p< 0.0001). Conclusions ΔPpl can be estimated reasonably accurately by ΔCVP using our method in assisted and unassisted spontaneous breathing children during mechanical ventilation.

Esophageal pressure as a surrogate of pleural pressure in mechanically-ventilated patients

BackgroundEsophageal pressure (Pes) is used to approximate pleural pressure (PPL) and therefore to estimate transpulmonary pressure (PL).ObjectivesWe aimed to compare esophageal and regional pleural pressures and to calculate transpulmonary pressures in a prospective physiological study on lung transplant recipients during their stay in the intensive care unit of a tertiary university hospital.MethodsLung transplant recipients receiving invasive mechanical ventilation and monitored by esophageal manometry and dependent and non-dependent pleural catheters were investigated during the post-operative period. We performed simultaneous short time measurements and recordings of esophageal manometry and pleural pressures. Expiratory and inspiratory PL were computed by subtracting regional PPL or Pes from airway pressure; inspiratory PL was also calculated with the elastance ratio method.ResultsSixteen patients were included. Among them, 14 were analyzed. Esophageal pressures correlated with dependent and non-dependent pleural pressures during expiration, respectively R2=0.71, p=0.005 and R2=0.77, p=0.001 and during inspiration, respectively, R2=0.66 for both (respectively p=0.01 and p=0.014). PL calculated using Pes were close to those obtained from the dependent pleural catheter but higher than those obtained from the non-dependent pleural catheter both during expiration and inspiration.ConclusionIn ventilated lung transplant recipients, esophageal manometry is well correlated to pleural pressure. Absolute value of Pes is higher than pleural pressure of non-dependent lung regions and could therefore underestimate the highest level of lung stress in these at high risk of overinflation.