NIH Public Access

Harvard University, Cambridge, Massachusetts, United States
Critical Care Medicine (Impact Factor: 6.31). 05/2006; 34(5):1389-94. DOI: 10.1097/01.CCM.0000215515.49001.A2
Source: PubMed


Pressure inflating the lung during mechanical ventilation is the difference between pressure applied at the airway opening (Pao) and pleural pressure (Ppl). Depending on the chest wall's contribution to respiratory mechanics, a given positive end-expiratory and/or end-inspiratory plateau pressure may be appropriate for one patient but inadequate or potentially injurious for another. Thus, failure to account for chest wall mechanics may affect results in clinical trials of mechanical ventilation strategies in acute respiratory distress syndrome. By measuring esophageal pressure (Pes), we sought to characterize influence of the chest wall on Ppl and transpulmonary pressure (PL) in patients with acute respiratory failure.
Prospective observational study.
Medical and surgical intensive care units at Beth Israel Deaconess Medical Center.
Seventy patients with acute respiratory failure.
Placement of esophageal balloon-catheters.
Airway, esophageal, and gastric pressures recorded at end-exhalation and end-inflation Pes averaged 17.5 +/- 5.7 cm H2O at end-expiration and 21.2 +/- 7.7 cm H2O at end-inflation and were not significantly correlated with body mass index or chest wall elastance. Estimated PL was 1.5 +/- 6.3 cm H2O at end-expiration, 21.4 +/- 9.3 cm H2O at end-inflation, and 18.4 +/- 10.2 cm H2O (n = 40) during an end-inspiratory hold (plateau). Although PL at end-expiration was significantly correlated with positive end-expiratory pressure (p < .0001), only 24% of the variance in PL was explained by Pao (R = .243), and 52% was due to variation in Pes.
In patients in acute respiratory failure, elevated esophageal pressures suggest that chest wall mechanical properties often contribute substantially and unpredictably to total respiratory impedance, and therefore Pao may not adequately predict PL or lung distention. Systematic use of esophageal manometry has the potential to improve ventilator management in acute respiratory failure by providing more direct assessment of lung distending pressure.

Download full-text


Available from: Atul Malhotra, Nov 21, 2014
41 Reads
  • Source
    • "Additionally, limiting end-inspiratory plateau pressure is used commonly to minimize barotrauma. However, airway pressures do not delineate the often substantial contribution of the chest wall to respiratory system mechanics (Talmor et al. 2006). Plateau pressures may underestimate alveolar distension in patients with negative pleural pressures, such as during spontaneous respirations. "
    The Journal of Physiology 06/2013; 591(Pt 11):2767-9. DOI:10.1113/jphysiol.2013.252619 · 5.04 Impact Factor
  • Source
    • "Since pleural pressure was not assessed in these studies, there is a possibility that part of the beneficial effect of raising PEEP was due to offsetting a negative transpulmonary pressure at end expiration (EXPtp). This possibility is supported by previous reports [9] [10] demonstrating improved oxygenation and lung compliance when end-expiratory transpulmonary pressure was kept positive. The common belief is that by keeping EXPtp positive, we may prevent cycling collapse with deflations at end expiration, and thus derecruitment of alveolar lung units at end expiration. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Patients with acute respiratory failure and decreased respiratory system compliance due to ARDS frequently present a formidable challenge. These patients are often subjected to high inspiratory pressure, and in severe cases in order to improve oxygenation and preserve life, we may need to resort to unconventional measures. The currently accepted ARDSNet guidelines are characterized by a generalized approach in which an algorithm for PEEP application and limited plateau pressure are applied to all mechanically ventilated patients. These guidelines do not make any distinction between patients, who may have different chest wall mechanics with diverse pathologies and different mechanical properties of their respiratory system. The ability of assessing pleural pressure by measuring esophageal pressure allows us to partition the respiratory system into its main components of lungs and chest wall. Thus, identifying the dominant factor affecting respiratory system may better direct and optimize mechanical ventilation. Instead of limiting inspiratory pressure by plateau pressure, PEEP and inspiratory pressure adjustment would be individualized specifically for each patient's lung compliance as indicated by transpulmonary pressure. The main goal of this approach is to specifically target transpulmonary pressure instead of plateau pressure, and therefore achieve the best lung compliance with the least transpulmonary pressure possible.
    Critical care research and practice 09/2012; 2012(2090-1305):597932. DOI:10.1155/2012/597932
  • Source
    • "The balloon catheter was first passed into the stomach and then withdrawn to measure Pes. Proper balloon position was confirmed in all animals by observing an appropriate change in the pressure tracing as the balloon was withdrawn into the thorax (changes in pressure waveform, mean pressure and cardiac oscillation) as well as by observing a transient increase in pressure during a gentle compression of the abdomen as described previously [15]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: To test the hypothesis that open lung (OL) ventilatory strategies using high-frequency oscillatory ventilation (HFOV) or controlled mechanical ventilation (CMV) compared to CMV with lower positive end-expiratory pressure (PEEP) improve respiratory function while minimizing lung injury as well as systemic inflammation, a prospective randomized study was performed at a university animal laboratory using three different lung conditions. Seventy-eight adult male Wistar rats were randomly assigned to three groups: (1) uninjured (UI), (2) saline washout (SW), and (3) intraperitoneal/intravenous Escherichia coli lipopolysaccharide (LPS)-induced lung injury. Within each group, animals were further randomized to (1) OL with HFOV, (2) OL with CMV with "best" PEEP set according to the minimal static elastance of the respiratory system (BP-CMV), and (3) CMV with low PEEP (LP-CMV). They were then ventilated for 6 hours. HFOV was set with mean airway pressure (PmeanHFOV) at 2 cm H2O above the mean airway pressure recorded at BP-CMV (PmeanBP-CMV) following a recruitment manoeuvre. Six animals served as unventilated controls (C). Gas-exchange, respiratory system mechanics, lung histology, plasma cytokines, as well as cytokines and types I and III procollagen (PCI and PCIII) mRNA expression in lung tissue were measured. We found that (1) in both SW and LPS, HFOV and BP-CMV improved gas exchange and mechanics with lower lung injury compared to LP-CMV, (2) in SW; HFOV yielded better oxygenation than BP-CMV; (3) in SW, interleukin (IL)-6 mRNA expression was lower during BP-CMV and HFOV compared to LP-CMV, while in LPS inflammatory response was independent of the ventilatory mode; and (4) PCIII mRNA expression decreased in all groups and ventilatory modes, with the decrease being highest in LPS. Open lung ventilatory strategies associated with HFOV or BP-CMV improved respiratory function and minimized lung injury compared to LP-CMV. Therefore, HFOV with PmeanHFOV set 2 cm H2O above the PmeanBP-CMV following a recruitment manoeuvre is as beneficial as BP-CMV.
    Critical care (London, England) 10/2010; 14(5):R183. DOI:10.1186/cc9291 · 4.48 Impact Factor
Show more