Elastic Power of Mechanical Ventilation in Morbid Obesity and Severe Hypoxemia

Abstract

BACKGROUND: To minimize ventilator-induced lung injury, the primary clinical focus is currently expanding from measuring static indices of the individual tidal cycle (eg, plateau pressure and tidal volume) to more inclusive indicators of energy load, such as total power and its elastic components. Morbid obesity may influence these components. We characterized the relative values of elastic subcomponents of total power (ie, driving power and dynamic power) in subjects with severe hypoxemia, morbid obesity, or their combination. METHODS: We analyzed data from subjects receiving mechanical ventilation divided into 4 groups. P aO 2 /F IO 2 < 150 mm Hg (severe hypoxemia) indicated probable reduction of lung compliance while body mass index > 40 kg/m 2 (morbid obesity) suggested a possible contribution to reduced respiratory system compliance from the chest wall. Group 1 included subjects with no expected abnormality of lung compliance or chest wall compliance; Group 2 included subjects with expected reduction of lung compliance on the basis of severe hypoxemia but with no morbid obesity; Group 3 included subjects with morbid obesity without severe hypoxemia; and Group 4 included subjects with morbid obesity and severe hypoxemia. All ventilator-induced lung injury predictors were compared among groups using mixed-effects linear models. RESULTS: Groups 1-4 included 61, 52, 49, and 51 subjects, respectively. Mean body mass index averaged 28.7 kg/m 2 for nonobese subjects and 52.1 kg/m 2 for morbidly obese subjects. Mean driving pressure, dynamic power, and driving power of Groups 2 and 3 exceeded the corresponding values of Group 1 but fell into similar ranges when compared with each other. These values were highest in Group 4 subjects. In Group 2, mean dynamic power and driving power values were comparable to those in Group 3. CONCLUSIONS: In mechanically ventilated subjects, stress and energy-based ventilator-induced lung injury indicators are influenced by the relative contributions of chest wall and lung to overall respiratory mechanics. Numerical guidelines for ventilator-induced lung injury risk must strongly consider adjustment for these elastic characteristics in morbid obesity.

Association of lipid metabolism with pneumonia risk in under-five children in China

“…In fact, an association between obesity and hypoxemia had long been established in sleep apnea syndrome, and its mechanism was that obesity led to stricture of the respiratory tracts, promoting apnea and hypoxemia. 18 , 19 However, because the present study failed to find any significant difference in obesity (BMI Z-score) levels among all three groups, the relationship between hypoxemia and serum TG should be independent of obesity. Furthermore, both hypoxemia and plasma TG levels in pneumonia were clearly factors associated with inflammation, it was possible that inflammation could be a potential mechanism linking these two factors mentioned above, but future studies were needed to verify this assumption.…”

Outcomes and risk factors for delayed-onset postoperative respiratory failure: a multi-center case-control study by the University of California Critical Care Research Collaborative (UC3RC)

“…The Qadir et al findings of low adherence to LPV in known ARDS patients is interesting considering decades of evidence that LPV improves survival in ARDS, [ 51 ] but perhaps makes more sense when we consider the evolution of LPV from an initial focus on lower tidal volume and higher PEEP with or without lung recruitment measures, [ 52 – 54 ] to the addition of lower plateau pressures, [ 55 ] to a more recent focus on lower driving pressure (the difference between plateau pressure and PEEP) [ 56 ]. More recently, literature has emerged on dynamic, rather than static, indicators of energy load (e.g., flow amplitude and the clinician-selected flow waveform), [ 57 – 59 ] Future research to evaluate applicability in the operating suite ventilator management of adult elective surgery patients and possible associations between these modifiable determinants of ventilator induced lung injury (VILI) and PRF may be warranted.…”

Intraoperative Mechanical Power and Postoperative Pulmonary Complications in Noncardiothoracic Elective Surgery Patients: A 10-Year Retrospective Cohort Study

“…The normality of distributions was checked graphically and using the Shapiro–Wilk test. The association between intraoperative ventilation parameters and the occurrence of PPCs was assessed using a logistic regression model adjusted on predefined known confounding factors 3,11,24–27 (age, sex, ASA Physical Status, obesity, chronic obstructive pulmonary disease, length of surgery, digestive or vascular surgery, use of curare, transfusion, and surgical approach).…”