Accuracy of respiratory muscle assessments to predict weaning outcomes: a systematic review and comparative meta-analysis.

BACKGROUND: Several bedside assessments are used to evaluate respiratory muscle function and to predict weaning from mechanical ventilation in patients on the intensive care unit. It remains unclear which assessments perform best in predicting weaning success. The primary aim of this systematic review and meta-analysis was to summarize and compare the accuracy of the following assessments to predict weaning success: maximal inspiratory (PImax) and expiratory pressures, diaphragm thickening fraction and excursion (DTF and DE), end-expiratory (Tdiee) and end-inspiratory (Tdiei) diaphragm thickness, airway occlusion pressure (P0.1), electrical activity of respiratory muscles, and volitional and non-volitional assessments of transdiaphragmatic and airway opening pressures. METHODS: Medline (via Pubmed), EMBASE, Web of Science, Cochrane Library and CINAHL were comprehensively searched from inception to 04/05/2023. Studies including adult mechanically ventilated patients reporting data on predictive accuracy were included. Hierarchical summary receiver operating characteristic (HSROC) models were used to estimate the SROC curves of each assessment method. Meta-regression was used to compare SROC curves. Sensitivity analyses were conducted by excluding studies with high risk of bias, as assessed with QUADAS-2. Direct comparisons were performed using studies comparing each pair of assessments within the same sample of patients. RESULTS: Ninety-four studies were identified of which 88 studies (n = 6296) reporting on either PImax, DTF, DE, Tdiee, Tdiei and P0.1 were included in the meta-analyses. The sensitivity to predict weaning success was 63% (95% CI 47-77%) for PImax, 75% (95% CI 67-82%) for DE, 77% (95% CI 61-87%) for DTF, 74% (95% CI 40-93%) for P0.1, 69% (95% CI 13-97%) for Tdiei, 37% (95% CI 13-70%) for Tdiee, at fixed 80% specificity. Accuracy of DE and DTF to predict weaning success was significantly higher when compared to PImax (p = 0.04 and p < 0.01, respectively). Sensitivity and direct comparisons analyses showed that the accuracy of DTF to predict weaning success was significantly higher when compared to DE (p < 0.01). CONCLUSIONS: DTF and DE are superior to PImax and DTF seems to have the highest accuracy among all included respiratory muscle assessments for predicting weaning success. Further studies aiming at identifying the optimal threshold of DTF to predict weaning success are warranted. TRIAL REGISTRATION: PROSPERO CRD42020209295, October 15, 2020.

Expiratory Muscles of Respiration and Weaning Failure: What do We Know So Far?

How to cite this article: Majeed NA, Nasa P. Expiratory Muscles of Respiration and Weaning Failure: What do We Know So Far? Indian J Crit Care Med 2023;27(1):1-3.

Administration of vitamin D and its metabolites in critically ill adult patients: an updated systematic review with meta-analysis of randomized controlled trials.

BACKGROUND: The clinical significance of vitamin D administration in critically ill patients remains inconclusive. The purpose of this systematic review with meta-analysis was to investigate the effect of vitamin D and its metabolites on major clinical outcomes in critically ill patients, including a subgroup analysis based on vitamin D status and route of vitamin D administration. METHODS: Major databases were searched through February 9, 2022. Randomized controlled trials of adult critically ill patients with an intervention group receiving vitamin D or its metabolites were included. Random-effect meta-analyses were performed to estimate the pooled risk ratio (dichotomized outcomes) or mean difference (continuous outcomes). Risk of bias assessment included the Cochrane tool for assessing risk of bias in randomized trials. RESULTS: Sixteen randomized clinical trials with 2449 patients were included. Vitamin D administration was associated with lower overall mortality (16 studies: risk ratio 0.78, 95% confidence interval 0.62-0.97, p = 0.03; I2 = 30%), reduced intensive care unit length of stay (12 studies: mean difference - 3.13 days, 95% CI - 5.36 to - 0.89, n = 1250, p = 0.006; I2 = 70%), and shorter duration of mechanical ventilation (9 studies: mean difference - 5.07 days, 95% CI - 7.42 to - 2.73, n = 572, p < 0.0001; I2 = 54%). Parenteral administration was associated with a greater effect on overall mortality than enteral administration (test of subgroup differences, p = 0.04), whereas studies of parenteral subgroups had lower quality. There were no subgroup differences based on baseline vitamin D levels. CONCLUSIONS: Vitamin D supplementation in critically ill patients may reduce mortality. Parenteral administration might be associated with a greater impact on mortality. Heterogeneity and assessed certainty among the studies limits the generalizability of the results. TRIAL REGISTRATION: PROSPERO international prospective database of systematic reviews (CRD42021256939-05 July 2021).

Plasma Soluble Suppression of Tumorigenicity-2 Associates with Ventilator Liberation in Acute Hypoxemic Respiratory Failure.

Rationale: Standard physiologic assessments of extubation readiness in patients with acute hypoxemic respiratory failure (AHRF) may not reflect lung injury resolution and could adversely affect clinical decision-making and patient outcomes. Objectives: We hypothesized that elevations in inflammatory plasma biomarkers sST2 (soluble suppression of tumorigenicity-2) and IL-6 indicate ongoing lung injury in AHRF and better inform patient outcomes compared with standard clinical assessments. Methods: We measured daily plasma biomarkers and physiologic variables in 200 patients with AHRF for up to 9 days after intubation. We tested the associations of baseline values with the primary outcome of unassisted breathing at Day 29. We analyzed the ability of serial biomarker measurements to inform successful ventilator liberation. Measurements and Main Results: Baseline sST2 concentrations were higher in patients dead or mechanically ventilated versus breathing unassisted at Day 29 (491.7 ng/ml [interquartile range (IQR), 294.5-670.1 ng/ml] vs. 314.4 ng/ml [IQR, 127.5-550.1 ng/ml]; P = 0.0003). Higher sST2 concentrations over time were associated with a decreased probability of ventilator liberation (hazard ratio, 0.80 per log-unit increase; 95% confidence interval [CI], 0.75-0.83; P = 0.03). Patients with higher sST2 concentrations on the day of liberation were more likely to fail liberation compared with patients who remained successfully liberated (320.9 ng/ml [IQR, 181.1- 495.6 ng/ml] vs. 161.6 ng/ml [IQR, 95.8-292.5 ng/ml]; P = 0.002). Elevated sST2 concentrations on the day of liberation decreased the odds of successful liberation when adjusted for standard physiologic parameters (odds ratio, 0.325; 95% CI, 0.119-0.885; P = 0.03). IL-6 concentrations did not associate with outcomes. Conclusions: Using sST2 concentrations to guide ventilator management may more accurately reflect underlying lung injury and outperform traditional measures of readiness for ventilator liberation.

Impact of a remifentanil supply shortage on mechanical ventilation in a tertiary care hospital: a retrospective comparison.

BACKGROUND: The continuous administration of opioids in critical care patients is a common therapy for the tolerance of mechanical ventilation. Opioid choice has a crucial impact on the length of mechanical ventilation. Owing to its very short context-sensitive half-life, remifentanil widens the available options for sedoanalgetic strategies. Supply disruption of such established intensive care medication has been reported to worsen clinical outcomes. METHODS: This retrospective study investigated the influence of a nationwide supply shortage of remifentanil on mechanical ventilation and ventilation-associated outcomes at three perioperative intensive care units (ICUs) in a tertiary care hospital in Vienna. Two groups were followed: patients admitted to the ICU during the remifentanil shortage (July 1, 2016 to September 30, 2016) and a control group one year after the remifentanil shortage (July 1, 2017 to September 30, 2017). Included patients were adults, received mechanical ventilation for at least 6 h, were admitted less than 90 days in the respective ICU, and survived their admission. RESULTS: For comparison, Poisson count regression models and logistic regression models were computed. To compensate for multiple testing, the significance level was split (0.02 for the primary and 0.006 for secondary outcome parameters). Patients in the remifentanil shortage group received significantly longer mechanical ventilation (risk ratio 2.19, 95% confidence interval 2.14-2.24, P <0.001) with significantly prolonged ICU stay (P <0.001), days with non-invasive ventilation (P <0.001), and length of hospital stay (P <0.001). No significant difference was found in the occurrence of pneumonia (P = 0.040) and sepsis (P = 0.061). A greater proportion of patients in the shortage group underwent secondary tracheostomy (P <0.001). CONCLUSIONS: The remifentanil shortage caused a significant impairment of essential outcome parameters in the ICU.

Impact of multidrug-resistant bacteria on outcome in patients with prolonged weaning.

BACKGROUND: Pneumonia and septic pneumonic shock are the most common indications for long-term mechanical ventilation and prolonged weaning, independent of any comorbidities. Multidrug resistant (MDR) bacteria are emerging as a cause of pneumonia or occur as a consequence of antimicrobial therapy. The influence of MDR bacteria on outcomes in patients with prolonged weaning is unknown. METHODS: Patients treated in a specialized weaning unit of a university hospital between April 2013 and April 2016 were analyzed. Demographic data, clinical characteristics, length of stay (LOS) in the intensive care unit (ICU) and weaning unit, ventilator-free days and mortality rates were determined in prolonged weaning patients with versus without MDR bacteria (methicillin-resistant Staphylococcus aureus bacteria, [MRSA]; extended spectrum beta lactamase [ESBL]- and Gyrase-producing gram negative bacteria resistant to three of four antibiotic groups [3 MRGN]; panresistant Pseudomonas aeruginosa and other carbapenemase-producing gram-negative bacteria resistant to all four antibiotic groups [4 MRGN]). Weaning failure was defined as death or discharge with invasive ventilation. RESULTS: Of 666 patients treated in the weaning unit, 430 fulfilled the inclusion criteria and were included in the analysis. A total of 107 patients had isolates of MDR bacteria suspected as causative pathogens identified during the treatment process. Patients with MDR bacteria had higher SAPS II values at ICU admission and a significantly longer ICU LOS. Four MRGN P. aeruginosa and Acinetobacter baumanii were the most common MDR bacteria identified. Patients with versus without MDR bacteria had significantly higher arterial carbon dioxide levels at the time of weaning admission and a significantly lower rate of successful weaning (23% vs 31%, p < 0.05). Mortality rate on the weaning unit was 12.4% with no difference between the two patient groups. There were no significant differences between patient groups in secondary infections and ventilator-free days. CONCLUSIONS: In patients with pneumonia or septic pneumonic shock undergoing prolonged weaning, infection with MDR bacteria may influence the weaning success rate but does not appear to impact on patient survival.

Predicting weaning and extubation outcomes in long-term mechanically ventilated patients using the modified Burns Wean Assessment Program scores.

BACKGROUND AND OBJECTIVE: A number of clinical factors play pivotal roles in weaning and successful extubation of patients requiring long-term mechanical ventilator (LTMV) support. Many patients fail extubation even after passing weaning protocols and spontaneous breathing trials. This study aimed to assess the effectiveness of using a modified Burns Wean Assessment Program (m-BWAP) scoring instrument to predict extubation outcome in patients requiring LTMV. METHODS: All patients with a diagnostic coding for respiratory failure requiring LTMV for longer than 21 days over a 5-year period in a single centre (total 527 patients) were included. Advanced practice nurses trained in the use of the m-BWAP scored the items according to standard definitions. All patients were weaned by pressure support weaning and spontaneous breathing trails. Patients were divided into successful and unsuccessful groups according to the weaning and extubation outcomes. Baseline data, traditional weaning parameters and m-BWAP of the groups were analysed. The sensitivity and specificity of m-BWAP for predicting successful extubation were calculated. RESULTS: Of the 527 patients included, 145 (27.5%) had successful weaning trials. Of the 130 patients extubated, 102 (78.5%) had successful extubation. The m-BWAP score was higher in the patients with successful weaning trials and successful extubation outcome. Using a cut-off value of 60, the sensitivity and specificity of the m-BWAP to predict successful extubation were 81.4% and 82.1%, respectively. This was better than traditional weaning parameters. CONCLUSIONS: The m-BWAP is a good predictor for weaning and extubation outcome in patients requiring LTMV for longer than 21 days.

Neuro-ventilatory efficiency during weaning from mechanical ventilation using neurally adjusted ventilatory assist.

BACKGROUND: Neuro-ventilatory efficiency (NVE), defined as the tidal volume to electrical diaphragm-activity ratio (VT/EAdi) at the beginning and end of the weaning process after acute hypoxaemic respiratory failure, may provide valuable information about patient recovery. METHODS: This observational study included 12 patients breathing with neurally adjusted ventilatory assist (NAVA). When a spontaneous breathing trial (SBT) with pressure support of 7 cm H2O and PEEP was unsuccessful, NAVA was used and the level was adjusted to obtain an EAdi of ∼60% of maximal EAdi during SBT. VT and EAdi were recorded continuously. We compared changes in NVE between NAVA and SBT at the first failed and first successful SBT. RESULTS: When patients were switched from NAVA to SBT, NVE was significantly reduced during both unsuccessful and successful SBT (-56 and -38%, respectively); however, this reduction was significantly lower when SBT was successful (P=0.01). Between the first and last day of weaning, we observed that NVE decreased with NAVA [40.6 (27.7-89.5) vs 28.8 (18.6-46.7); P=0.002] with a significant decrease in NAVA level, whereas it remained unchanged during SBT [15.4 (10.7-39.1) vs 19.5 (11.6-29.6); P=0.50] with significant increases in both EAdi and VT and no difference in respiratory rhythm. CONCLUSIONS: These results suggest that in patients after respiratory failure and prolonged mechanical ventilation, changes in VT and NVE, between SBTs are indicative of patient recovery. Larger clinical trials are needed to clarify whether changes in NVE reliably predict weaning in patients ventilated with NAVA.

Diaphragmatic Kinetics Assessment by Tissue Doppler Imaging and Extubation Outcome.

BACKGROUND: The assessment of diaphragmatic kinetics through tissue Doppler imaging (dTDI) was recently proposed as a means to describe diaphragmatic activity in both healthy individuals and intubated patients undergoing weaning from mechanical ventilation. Our primary aim was to investigate whether the diaphragmatic excursion velocity measured with dTDI at the end of a spontaneous breathing trial (SBT) was different in subjects successfully extubated versus those who passed the trial but exhibited extubation failure within 48 h after extubation. METHODS: We enrolled 100 adult subjects, all of whom had successfully passed a 30-min SBT conducted in CPAP of 5 cm H2O. In cases of extubation failure within 48 h after liberation from invasive mechanical ventilation, subjects were re-intubated or supported through noninvasive ventilation. dTDI was performed at the end of the SBT to assess excursion, velocity, and acceleration. RESULTS: Extubation was successful in 79 subjects, whereas it failed in 21 subjects. The median (interquartile range [IQR]) inspiratory peak excursion velocity (3.1 [IQR 2.0-4.3] vs 1.8 [1.3-2.6] cm/s, P < .001), mean velocity (1.6 [IQR 1.2-2.4] vs 1.1 [IQR 0.8-1.4] cm/s, P < .001), and acceleration (8.8 [IQR 5.0-17.8] vs 4.2 [IQR 2.4-8.0] cm/s2, P = .002) were all significantly higher in subjects who failed extubation compared with those who were successfully extubated. Similarly, the median expiratory peak relaxation velocity (2.6 [IQR 1.9-4.5] vs 1.8 [IQR 1.2-2.5] cm/s, P < .001), mean velocity (1.1 [IQR 0.7-1.7] vs 0.9 [IQR 0.6-1.0] cm/s, P = .002), and acceleration (11.2 [IQR 9.1-19.0] vs 7.1 [IQR 4.6-12.0] cm/s2, P = .004) were also higher in the subjects who failed extubation. CONCLUSIONS: In our setting, at the end of SBT, subjects who developed extubation failure within 48 h after extubation experienced a greater diaphragmatic activation compared with subjects who were successfully extubated. (ClinicalTrials.gov registration NCT03962322.).

Association of Low Alanine Aminotransferase Values with Extubation Failure in Adult Critically Ill Patients: A Retrospective Cohort Study.

BACKGROUND: Liberation from mechanical ventilation is a cardinal landmark during hospitalization of ventilated patients. Decreased muscle mass and sarcopenia are associated with a high risk of extubation failure. A low level of alanine aminotransferase (ALT) is a known biomarker of sarcopenia. This study aimed to determine whether low levels of ALT are associated with increased risk of extubation failure among critically ill patients. METHODS: This was a retrospective single-center cohort study of mechanically ventilated patients undergoing their first extubation. The study's outcome was extubation failure within 48 h and 7 days. Multivariable logistic and Cox regression were performed to determine whether ALT was an independent predictor of these outcomes. RESULTS: The study included 329 patients with a median age of 62.4 years (IQR 48.1-71.2); 210 (63.8%) patients were at high risk for extubation failure. 66 (20.1%) and 83 (25.2%) failed the extubation attempt after 48 h and 7 days, respectively. Low ALT values were more common among patients requiring reintubation (80.3-61.5% vs. 58.6-58.9%, p < 0.002). Multivariable logistic regression analysis identified ALT as an independent predictor of extubation failure at 48 h and 7 days. ALT ≤ 21 IU/L had an adjusted hazard ratio (HR) of 2.41 (95% CI 1.31-4.42, p < 0.001) for extubation failure at 48 h and ALT ≤ 16 IU/L had adjusted HR of 1.94 (95% CI 1.25-3.02, p < 0.001) for failure after 7 days. CONCLUSIONS: Low ALT, an established biomarker of sarcopenia and frailty, is an independent risk factor for extubation failure among hospitalized patients. This simple laboratory parameter can be used as an effective adjunct predictor, along with other weaning parameters, and thereby facilitate the identification of high-risk patients.

Challenging Convention: Daytime Versus Nighttime Extubation in the Pediatric ICU.

BACKGROUND: The majority of pediatric extubations occur during day shift hours. There is a time-dependent relationship between mechanical ventilation duration and complications. It is not known if extubation shift (day vs night) correlates with pediatric extubation outcomes. Pediatric ventilation duration may be unnecessarily prolonged if extubation is routinely delayed until day shift hours. METHODS: We hypothesized that extubation failure would not correlate with shift of extubation and that ventilation duration at first extubation and that length of stay in the pediatric ICU (PICU) would be shorter for children extubated at night. This was a retrospective cohort study within one tertiary care, 24-bed, academic PICU. RESULTS: 582 ventilation encounters were included, representing 517 unique subjects. Status epilepticus was a more common diagnosis among night shift extubations (P = .005), whereas surgical airway conditions were more common among day shift extubations (P = .02). Mechanical ventilation duration at first extubation (37.6 vs 62.5 h, P < .001) and length of stay in the PICU (2.8 vs 4.5 d, P < .001) were shorter for night shift extubations. The extubation failure rate was 10.3% for day shift and 8.1% for night shift (P = .40). Logistic regression modeling at the level of the unique subject indicated that extubation shift was not associated with extubation failure (P = .44). The majority of re-intubation events occurred on the shift opposite of extubation. There was no difference in complications according to shift of re-intubation (P = .72). CONCLUSIONS: Extubation failure was not independently associated with extubation shift in this single-center study. Ventilation liberation should be considered at the first opportunity dictated by clinical data and patient-specific factors rather than by the time of day at centers with similar resources.

Predictors of successful weaning in patients requiring extremely prolonged mechanical ventilation.

INTRODUCTION: For patients on prolonged mechanical ventilation (PMV; > 21 days), successful weaning has been attributed to various factors. The aim of this study is to determine the usefulness of the rapid shallow breathing index(RSBI) and other potential predictors of successful weaning in patients unable to wean and requiring extreme PMV at a hospital-based long-term ventilator facility in Israel. Material and ethods: Retrospective analysis of prospectively collected data over 5 years. RESULTS: A total of 150 subjects on PMV, ready to undergo a weaning process, were included in the study. Of them, 60 (40.0%) were males. The mean age of the whole study population was 76.5 years (SD = 13.6; range 22.0-96.0 years). The subjects were on MV for a mean period of 170.1 days (SD = 237.6; range 25.0-1624.0 days). Sixty patients (40%) were successfully weaned. The mean RSBI in the successfully weaned population was 41.9 breaths/min/L (SD = 12.3; range 13.0-80.4 breaths/min/L), in the population where weaning failed, it was 114.8 breaths/min/L (SD = 69.2; range 47.5-450.0 breaths/min/L). By univariate logistic regression analysis, younger age (p < 0.007), female gender (p < 0.001), decreased duration of MV (p < 0.023), re-spiratory rate (p < 0.001) and RSBI (p < 0.001), increased tidal volume/ideal body weight (p < 0.001) and minute ventilation (p < 0.01) were found to be factors that significantly predict successful weaning. By multivariate analysis, increased tidal volume/ /ideal body weight (p < 0.007) and decreased RSBI (p < 0.046) were found to be independent predictors of successful weaning (p < 0.001; R2 Nagelkerke = 0.90). CONCLUSIONS: Factors independently predicting successful weaning in patients requiring extreme PMV included increased tidal volume/ideal body weight and decreased RSBI.

Esophageal Manometry.

The estimation of pleural pressure with esophageal manometry has been used for decades, and it has been a fertile area of physiology research in healthy subject as well as during mechanical ventilation in patients with lung injury. However, its scarce adoption in clinical practice takes its roots from the (false) ideas that it requires expertise with years of training, that the values obtained are not reliable due to technical challenges or discrepant methods of calculation, and that measurement of esophageal pressure has not proved to benefit patient outcomes. Despites these criticisms, esophageal manometry could contribute to better monitoring, optimization, and personalization of mechanical ventilation from the acute initial phase to the weaning period. This review aims to provide a comprehensive but comprehensible guide addressing the technical aspects of esophageal catheter use, its application in different clinical situations and conditions, and an update on the state of the art with recent studies on this topic and on remaining questions and ways for improvement.

Low-pressure support vs automatic tube compensation during spontaneous breathing trial for weaning.

BACKGROUND: During spontaneous breathing trial, low-pressure support is thought to compensate for endotracheal tube resistance, but it actually should provide overassistance. Automatic tube compensation is an option available in the ventilator to compensate for flow-resistance of endotracheal tube. Its effects on patient effort have been poorly investigated. We aimed to compare the effects of low-pressure support and automatic tube compensation during spontaneous breathing trial on breathing power and lung ventilation distribution. RESULTS: We performed a randomized crossover study in 20 patients ready to wean. Each patient received both methods for 30 min separated by baseline ventilation: pressure support 0 cmH2O and automatic tube compensation 100% in one period and pressure support 7 cmH2O without automatic tube compensation in the other period, a 4 cmH2O positive end-expiratory pressure being applied in each. Same ventilator brand (Evita XL, Draeger, Germany) was used. Breathing power was assessed from Campbell diagram with esophageal pressure, airway pressure, flow and volume recorded by a data logger. Lung ventilation distribution was assessed by using electrical impedance tomography (Pulmovista, Draeger, Germany). During the last 2 min of low-pressure support and automatic compensation period breathing power and lung ventilation distribution were measured on each breath. Breathing power generated by the patient's respiratory muscles was 7.2 (4.4-9.6) and 9.7 (5.7-21.9) J/min in low-pressure support and automatic tube compensation periods, respectively (P = 0.011). Lung ventilation distribution was not different between the two methods. CONCLUSIONS: We found that ATC was associated with higher breathing power than low PS during SBT without altering the distribution of lung ventilation.

Physiological effects of high-flow oxygen in tracheostomized patients.

BACKGROUND: High-flow oxygen therapy via nasal cannula (HFOTNASAL) increases airway pressure, ameliorates oxygenation and reduces work of breathing. High-flow oxygen can be delivered through tracheostomy (HFOTTRACHEAL), but its physiological effects have not been systematically described. We conducted a cross-over study to elucidate the effects of increasing flow rates of HFOTTRACHEAL on gas exchange, respiratory rate and endotracheal pressure and to compare lower airway pressure produced by HFOTNASAL and HFOTTRACHEAL. METHODS: Twenty-six tracheostomized patients underwent standard oxygen therapy through a conventional heat and moisture exchanger, and then HFOTTRACHEAL through a heated humidifier, with gas flow set at 10, 30 and 50 L/min. Each step lasted 30 min; gas flow sequence during HFOTTRACHEAL was randomized. In five patients, measurements were repeated during HFOTTRACHEAL before tracheostomy decannulation and immediately after during HFOTNASAL. In each step, arterial blood gases, respiratory rate, and tracheal pressure were measured. RESULTS: During HFOTTRACHEAL, PaO2/FiO2 ratio and tracheal expiratory pressure slightly increased proportionally to gas flow. The mean [95% confidence interval] expiratory pressure raise induced by 10-L/min increase in flow was 0.2 [0.1-0.2] cmH2O (ρ = 0.77, p < 0.001). Compared to standard oxygen, HFOTTRACHEAL limited the negative inspiratory swing in tracheal pressure; at 50 L/min, but not with other settings, HFOTTRACHEAL increased mean tracheal expiratory pressure by (mean difference [95% CI]) 0.4 [0.3-0.6] cmH2O, peak tracheal expiratory pressure by 0.4 [0.2-0.6] cmH2O, improved PaO2/FiO2 ratio by 40 [8-71] mmHg, and reduced respiratory rate by 1.9 [0.3-3.6] breaths/min without PaCO2 changes. As compared to HFOTTRACHEAL, HFOTNASAL produced higher tracheal mean and peak expiratory pressure (at 50 L/min, mean difference [95% CI]: 3 [1-5] cmH2O and 4 [1-7] cmH2O, respectively). CONCLUSIONS: As compared to standard oxygen, 50 L/min of HFOTTRACHEAL are needed to improve oxygenation, reduce respiratory rate and provide small degree of positive airway expiratory pressure, which, however, is significantly lower than the one produced by HFOTNASAL.

Predictive models of prolonged mechanical ventilation yield moderate accuracy.

PURPOSE: To develop a model to predict prolonged mechanical ventilation within 48 hours of its initiation. MATERIALS AND METHODS: In 282 general intensive care unit patients, multiple variables from the first 2 days on mechanical ventilation and their total ventilation duration were prospectively collected. Three models accounting for early deaths were developed using different analyses: (a) multinomial logistic regression to predict duration > 7 days vs duration ≤ 7 days alive vs duration ≤ 7 days death; (b) binary logistic regression to predict duration > 7 days for the entire cohort and for survivors only, separately; and (c) Cox regression to predict time to being free of mechanical ventilation alive. RESULTS: Positive end-expiratory pressure, postoperative state (negatively), and Sequential Organ Failure Assessment score were independently associated with prolonged mechanical ventilation. The multinomial regression model yielded an accuracy (95% confidence interval) of 60% (53%-64%). The binary regression models yielded accuracies of 67% (61%-72%) and 69% (63%-75%) for the entire cohort and for survivors, respectively. The Cox regression model showed an equivalent to area under the curve of 0.67 (0.62-0.71). CONCLUSIONS: Different predictive models of prolonged mechanical ventilation in general intensive care unit patients achieve a moderate level of overall accuracy, likely insufficient to assist in clinical decisions.