Advanced respiratory mechanics assessment in mechanically ventilated obese and non-obese patients with or without acute respiratory distress syndrome.

BACKGROUND: Respiratory mechanics is a key element to monitor mechanically ventilated patients and guide ventilator settings. Besides the usual basic assessments, some more complex explorations may allow to better characterize patients' respiratory mechanics and individualize ventilation strategies. These advanced respiratory mechanics assessments including esophageal pressure measurements and complete airway closure detection may be particularly relevant in critically ill obese patients. This study aimed to comprehensively assess respiratory mechanics in obese and non-obese ICU patients with or without ARDS and evaluate the contribution of advanced respiratory mechanics assessments compared to basic assessments in these patients. METHODS: All intubated patients admitted in two ICUs for any cause were prospectively included. Gas exchange and respiratory mechanics including esophageal pressure and end-expiratory lung volume (EELV) measurements and low-flow insufflation to detect complete airway closure were assessed in standardized conditions (tidal volume of 6 mL kg-1 predicted body weight (PBW), positive end-expiratory pressure (PEEP) of 5 cmH2O) within 24 h after intubation. RESULTS: Among the 149 analyzed patients, 52 (34.9%) were obese and 90 (60.4%) had ARDS (65.4% and 57.8% of obese and non-obese patients, respectively, p = 0.385). A complete airway closure was found in 23.5% of the patients. It was more frequent in obese than in non-obese patients (40.4% vs 14.4%, p < 0.001) and in ARDS than in non-ARDS patients (30% vs. 13.6%, p = 0.029). Respiratory system and lung compliances and EELV/PBW were similarly decreased in obese patients without ARDS and obese or non-obese patients with ARDS. Chest wall compliance was not impacted by obesity or ARDS, but end-expiratory esophageal pressure was higher in obese than in non-obese patients. Chest wall contribution to respiratory system compliance differed widely between patients but was not predictable by their general characteristics. CONCLUSIONS: Most respiratory mechanics features are similar in obese non-ARDS and non-obese ARDS patients, but end-expiratory esophageal pressure is higher in obese patients. A complete airway closure can be found in around 25% of critically ill patients ventilated with a PEEP of 5 cmH2O. Advanced explorations may allow to better characterize individual respiratory mechanics and adjust ventilation strategies in some patients. Trial registration NCT03420417 ClinicalTrials.gov (February 5, 2018).

A novel method for assessment of airway opening pressure without the need for low-flow insufflation.

BACKGROUND: Airway opening pressure (AOP) detection and measurement are essential for assessing respiratory mechanics and adapting ventilation. We propose a novel approach for AOP assessment during volume assist control ventilation at a usual constant-flow rate of 60 L/min. OBJECTIVES: To validate the conductive pressure (Pcond) method, which compare the Pcond-defined on the airway pressure waveform as the difference between the airway pressure level at which an abrupt change in slope occurs at the beginning of insufflation and PEEP-to resistive pressure for AOP detection and measurement, and to compare its respiratory and hemodynamic tolerance to the standard low-flow insufflation method. METHODS: The proof-of-concept of the Pcond method was assessed on mechanical (lung simulator) and physiological (cadavers) bench models. Its diagnostic performance was evaluated in 213 patients, using the standard low-flow insufflation method as a reference. In 45 patients, the respiratory and hemodynamic tolerance of the Pcond method was compared with the standard low-flow method. MEASUREMENTS AND MAIN RESULTS: Bench assessments validated the Pcond method proof-of-concept. Sensitivity and specificity of the Pcond method for AOP detection were 93% and 91%, respectively. AOP obtained by Pcond and standard low-flow methods strongly correlated (r = 0.84, p < 0.001). Changes in SpO2 were significantly lower during Pcond than during standard method (p < 0.001). CONCLUSION: Determination of Pcond during constant-flow assist control ventilation may permit to easily and safely detect and measure AOP.

Assessment of renal hemodynamic toxicity of fluid challenge with 0.9% NaCl compared to balanced crystalloid (PlasmaLyte®) in a rat model with severe sepsis.

BACKGROUND: According to international guidelines, volume expansion with crystalloids is the first-line treatment for hemodynamic management in patients with severe sepsis or septic shock. Compared to balanced crystalloids, 0.9% sodium chloride (0.9% NaCl) induces hyperchloremia and metabolic acidosis and may alter renal hemodynamics and function. We compared the effects of 0.9% NaCl to a less chloride-concentrated fluid, PlasmaLyte® (PL) in targeted fluid resuscitation in a randomized, double-blind controlled study in an experimental model of severe sepsis in rats. RESULTS: A sepsis with hypotension was induced by cecal ligature and puncture (CLP) in 40 male Wistar rats (20 for each crystalloid). Rats received fluid resuscitation over a period of 200 min for a targeted mean arterial pressure of 90 mm Hg. Animals received similar volumes of 0.9% NaCl or PL. Unlike PL-resuscitated rats, 0.9% NaCl-resuscitated rats experienced hyperchloremia and metabolic acidosis, whereas systemic hemodynamics, renal hemodynamics and renal function were not significantly different between both groups. CONCLUSION: In our model of rats with severe sepsis resuscitated with large amounts of crystalloids, 0.9% NaCl-induced hyperchloremic acidosis, but balanced crystalloid did not improve systemic and renal hemodynamics or renal function.

Amount of care per survivor in young and older patients hospitalized in intensive care unit: a retrospective study.

BACKGROUND: It is unknown whether the amount of care deployed in the intensive care unit population divided by the number of survivors, that is, amount of care per survivor including the care performed for nonsurvivors, differs between patients older and younger than 75 years of age. METHODS: Data were extracted from the computerized files of all 2,220 patients admitted in a medical intensive care unit between January 2009 and December 2010. Patients ≥75 and <75 years old were compared. The Omega score per survivor (OMEGA/S) was calculated in both age groups by dividing the total amount of Omega points, a score of cumulated care load calculated over intensive care unit stay, by the number of survivors in each group. RESULTS: OMEGA/S was 26% higher in elderly versus younger patients when considering intensive care unit mortality and 40% higher when considering hospital mortality. The absence of difference in raw Omega values between the two groups implies that OMEGA/S differences were related to differences in mortality rate. Simplified Acute Physiology Score II (without age-related points) strata analysis (<20, 20-39, 40-59, 60-79, and ≥80) showed that OMEGA/S in the elderly patients was significantly higher in the first three Simplified Acute Physiology Score II strata only. When calculating by main diagnosis categories, a major increase in the difference of OMEGA/S between elderly and younger patients was observed in cardiac arrest patients due to a major difference in mortality rate. CONCLUSIONS: Elderly patients required a significantly higher care load per survivor in comparison to younger patients. This excess was mainly due to patients with low initial severity.

[Comprehensive geriatric assessment in intensive care unit: a pilot study (pre-Seniorea)]. / Évaluation gériatrique standardisée en secteur de réanimation : étude pilote pré-Seniorea.

BACKGROUND: long-term outcomes of elderly patients after an intensive care unit (ICU) stay are not fully elucidated. The objective of the pre-Seniorea study was to examine the feasibility of comprehensive geriatric assessment (CGA) during and after the ICU stay. METHODS: inpatients aged 75 years and over admitted to medical and surgical ICUs of Angers University Hospital, France, from june to september 2012, received a SGA (assessment of morbidities, frailty, cognition, anxiety, mood, nutrition, functional abilities, motor function, pain, caregiver burden and quality of life) at ICU admission (through a proxy interview), at the end of the ICU stay, and 3 month later in the place of life. RESULTS: fifty-two patients were included (81 [78; 83] years (median [25(th); 75(th) percentile]); 35 males; SAPSII 47 [38; 56]; 80% ventilation). ICU survival was 73% (n=38), 58% (n=30) after three months, and 54% (n=28) after 12 months. The CGA at ICU admission was performed in all patients and lasted 10 [5; 10] minutes. The CGA at discharge was performed in all survivors and lasted 10 [5; 15] minutes. In all, 26 survivors received CGA in their place of life after 3 months. Travel time by evaluators was 42 minutes, and time on site 45 [45; 60] minutes. At 3 months, 85% of surviving patients were at home and felt happy, 80% had preserved autonomy. The only variable predictive of survival at three months was the SAPSII score. CONCLUSION: the follow-up of elderly inpatient admitted to ICU with repeated CGAs, including long-term evaluations in the place of life, was feasible and well-accepted. These results set the place for larger multicentric trials.

Clinical review: bedside assessment of alveolar recruitment.

Recruitment is a dynamic physiological process that refers to the reopening of previously gasless lung units. Cumulating evidence has led to a better understanding of the rules that govern both recruitment and derecruitment during mechanical ventilation of patients with acute respiratory distress syndrome. Therefore not only the positive end-expiratory pressure, but also the tidal volume, the inspired oxygen fraction, repeated tracheal suctioning as well as sedation and paralysis may affect recruitment of acute respiratory distress syndrome lungs that are particularly prone to alveolar instability. In the present article, we review the recently reported data concerning the physiological significance of the pressure-volume curve and its use to assess alveolar recruitment. We also describe alternate techniques that have been proposed to assess recruitment at the bedside. Whether recruitment should be optimized remains an ongoing controversy that warrants further clinical investigation.

Helium/oxygen mixture reduces the work of breathing at the end of the weaning process in patients with severe chronic obstructive pulmonary disease.

OBJECTIVE: To test the hypothesis that helium/oxygen mixture can reduce the work of breathing at the end of the weaning process in patients with chronic obstructive pulmonary disease. DESIGN: Prospective, randomized, crossover study. SETTING: Two medical intensive care units at two university tertiary care centers. PATIENTS: Thirteen patients with chronic obstructive pulmonary disease evaluated just before and after extubation. INTERVENTIONS: Helium/oxygen and air/oxygen mixtures were administered sequentially, for 20 mins each, in a randomized order, just before extubation. It was possible to repeat the study after extubation in five patients. MEASUREMENTS AND MAIN RESULTS: Before extubation, the helium/oxygen mixture induced no significant variation in the breathing pattern. By contrast, it reduced the work of breathing from 1.442 +/- 0.718 J/L (mean +/- sd) to 1.133 +/- 0.500 J/L (p <.05). This reduction was explained mainly by a reduction in the resistive component of the work of breathing from 0.662 +/- 0.376 to 0.459 +/- 0.256 J/L (p <.01). We also observed a slight reduction in the intrinsic positive end-expiratory pressure from 2.9 +/- 2.1 cm H(2)O to 2.1 +/- 1.8 cm H(2)O (p <.05). Similar results were also observed after extubation in five patients in whom the repetition of the study was possible. CONCLUSIONS: In spontaneously breathing intubated patients with chronic obstructive pulmonary disease recovering from an acute exacerbation, helium/oxygen mixture reduces the work of breathing as well as intrinsic positive end-expiratory pressure without modifying the breathing pattern.