Rafael Fernandez

A COMPARISON OF FOUR METHODS OF WEANING PATIENTS FROM MECHANICAL VENTILATION

BACKGROUND: Weaning patients from mechanical ventilation is an important problem in intensive care units. Weaning is usually conducted in an empirical manner, and a standardized approach has not been developed. METHODS: We carried out a prospective, randomized, multicenter study involving 546 patients who had received mechanical ventilation for a mean (+/- SD) of 7.5 +/- 6.1 days and who were considered by their physicians to be ready for weaning. One hundred thirty patients had respiratory distress during a two-hour trial of spontaneous breathing. These patients were randomly assigned to undergo one of four weaning techniques: intermittent mandatory ventilation, in which the ventilator rate was initially set at a mean (+/- SD) of 10.0 +/- 2.2 breaths per minute and then decreased, if possible, at least twice a day, usually by 2 to 4 breaths per minute (29 patients); pressure-support ventilation, in which pressure support was initially set at 18.0 +/- 6.1 cm of water and then reduced, if possible, by 2 to 4 cm of water at least twice a day (37 patients); intermittent trials of spontaneous breathing, conducted two or more times a day if possible (33 patients); or a once-daily trail of spontaneous breathing (31 patients). Standardized protocols were followed for each technique. RESULTS: The median duration of weaning was 5 days for intermittent mandatory ventilation (first quartile, 3 days; third quartile, 11 days), 4 days for pressure-support ventilation (2 and 12 days, respectively), 3 days for intermittent (multiple) trials of spontaneous breathing (2 and 6 days, respectively), and 3 days for a once-daily trial of spontaneous breathing (1 and 6 days, respectively). After adjustment for other covariates, the rate of successful weaning was higher with a once-daily trial of spontaneous breathing than with intermittent mandatory ventilation (rate ratio, 2.83; 95 percent confidence interval, 1.36 to 5.89; P < 0.006) or pressure-support ventilation (rate ratio, 2.05; 95 percent confidence interval, 1.04 to 4.04; P < 0.04). There was no significant difference in the rate of success between once-daily trials and multiple trials of spontaneous breathing. CONCLUSIONS: A once-daily trial of spontaneous breathing led to extubation about three times more quickly than intermittent mandatory ventilation and about twice as quickly as pressure-support ventilation. Multiple daily trials of spontaneous breathing were equally successful.

Platinum and rhodium distribution in airborne particulate matter and road dust

In this work the platinum and rhodium content in the atmosphere of Madrid was monitored for 1 year at seven different sites. Samples were taken with medium volume PM-10 collectors (< 10 microm) for 48 h and analysed by ICP-MS. The Pt and Rh content was dependent on the sampling site, ranging from < 0.1 to 57.1 and < 0.2 to 12.2 pg m(-3) with a medium value of 12.8 and 3.3 pg m(-3), respectively. These results show that the Pt and Rh content in airborne samples depends on the traffic density per day and also on medium driving speed. Road dust < 63 microm was analysed at the same time and at the same location. The Pt and Rh content at the six sites analysed was in the 31-2252 and 11-182 ng g(-1) range with an average of 317 and 74 ng g(-1), respectively. The average Pt/Rh ratio obtained was 4.3. similar to that obtained for airborne particles (4.0), and agrees with that of the more commonly used gasoline car catalyst [J.J. Mooney, Encyclopaedia of Chemical Technology (1996) 982]. Platinum distribution as a function of particle size in airborne particulate matter was also studied, by sampling with two high-volume sample collectors, a five-stage WRAC (from 10 to 65.3 microm and total) and a seven-stages PM-10) cascade impactor (from 9 to < 0.39 microm). Platinum is associated with a wide range of particle diameters. Due to the ultratrace level of Pt in airborne samples, its distribution in the atmosphere could not be considered as homogeneous. No trend could be established in Pt distribution in the different fractions, except that in most cases the highest value of Pt was obtained in the < 0.39-microm fraction. The Pt content was usually high in airborne samples when the Pb, Ce, Zr and Hf content was also high, thus confirming that the source of these pollutants is from traffic.

Effect of Postextubation High-Flow Nasal Cannula vs Conventional Oxygen Therapy on Reintubation in Low-Risk Patients: A Randomized Clinical Trial

IMPORTANCE Studies of mechanically ventilated critically ill patients that combine populations that are at high and low risk for reintubation suggest that conditioned high-flow nasal cannula oxygen therapy after extubation improves oxygenation compared with conventional oxygen therapy. However, conclusive data about reintubation are lacking. OBJECTIVE To determine whether high-flow nasal cannula oxygen therapy is superior to conventional oxygen therapy for preventing reintubation in mechanically ventilated patients at low risk for reintubation. DESIGN, SETTING, AND PARTICIPANTS Multicenter randomized clinical trial conducted between September 2012 and October 2014 in 7 intensive care units (ICUs) in Spain. Participants were 527 adult critical patients at low risk for reintubation who fulfilled criteria for planned extubation. Low risk for reintubation was defined as younger than 65 years; Acute Physiology and Chronic Health Evaluation II score less than 12 on day of extubation; body mass index less than 30; adequate secretions management; simple weaning; 0 or 1 comorbidity; and absence of heart failure, moderate-to-severe chronic obstructive pulmonary disease, airway patency problems, and prolonged mechanical ventilation. INTERVENTIONS Patients were randomized to undergo either high-flow or conventional oxygen therapy for 24 hours after extubation. MAIN OUTCOMES AND MEASURES The primary outcome was reintubation within 72 hours, compared with the Cochran-Mantel-Haenszel χ2 test. Secondary outcomes included postextubation respiratory failure, respiratory infection, sepsis and multiorgan failure, ICU and hospital length of stay and mortality, adverse events, and time to reintubation. RESULTS Of 527 patients (mean age, 51 years [range, 18-64]; 62% men), 264 received high-flow therapy and 263 conventional oxygen therapy. Reintubation within 72 hours was less common in the high-flow group (13 patients [4.9%] vs 32 [12.2%] in the conventional group; absolute difference, 7.2% [95% CI, 2.5% to 12.2%]; P = .004). Postextubation respiratory failure was less common in the high-flow group (22/264 patients [8.3%] vs 38/263 [14.4%] in the conventional group; absolute difference, 6.1% [95% CI, 0.7% to 11.6%]; P = .03). Time to reintubation was not significantly different between groups (19 hours [interquartile range, 12-28] in the high-flow group vs 15 hours [interquartile range, 9-31] in the conventional group; absolute difference, -4 [95% CI, -54 to 46]; P = .66]. No adverse effects were reported. CONCLUSIONS AND RELEVANCE Among extubated patients at low risk for reintubation, the use of high-flow nasal cannula oxygen compared with conventional oxygen therapy reduced the risk of reintubation within 72 hours. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT01191489.

Clinical consequences of the implementation of a weaning protocol

ObjectiveTo analyze the clinical and economic consequences of the implementation of a weaning protocol in patients mechanically ventilated (MV) for more than 48 h.DesignComparative studySettingGeneral intensive care unit (ICU) in a county hospital covering 360 000 inhabitants.Patients51 patients weaned by a fixed protocol were studied prospectively and compared with 50 retrospective controls.MeasurementsThe following variables were assessed: Acute Physiology and Chronic Health Evaluation (APACHE) II score, age, cause of respiratory failure, type of extubation (direct extubation or extubation using a weaning technique), number of days on MV before the weaning trial, weaning time, total duration of MV, complications (reintubations and tracheostomies), length of ICU stay, and mortality.ResultsThe groups were comparble in terms of age, APACHE II score, and main cause of acute respiratory failure. Number of days on MV up to the weaning trial were similar in the two groups (8.4±7.7 in the protocol group vs 7.5±5.5 in the control group, NS). Most of the patients (80%) in the protocol group were directly extubated without a weaning technique, unlike the control group (10%) (p<0.01). When a weaning technique was used, the weaning time was similar in both groups (3.5±3.9 days vs 3.6±2.2 days in the control group). Duration of MV was shorter in the protocol group (10.4±11.6 days) than in the control group (14.4±10.3 days) (p<0.05). As a result, the ICU stay was reduced by using the weaning protocol (16.7±16.5 days vs 20.3±13.2 days in the control group,p<0.05). We found no differences in reintubation rate (17 vs 14% in the control group) and need for tracheostomies (2 vs 8% in the control group).ConclusionThe implementation of a weaning protocol decreased the duration of MV and ICU stay by increasing the number of safe, direct extubations.

Gentamicin volume of distribution in critically ill septic patients

Gentamicin intrapatient pharmacokinetics variations were studied in 40 critically ill medical patients, suffering gram-negative sepsis. These patients were studied in two phases throughout gentamicin treatment: firstly, on the second day of treatment, when aggressive fluid therapy was required, and secondly, five days later, when patients had achieved a more stable clinical condition. Pharmacokinetic parameters were determined using least squares linear regression analysis assuming a one-compartment model using the Sawchuk-Zaske method. The apparent volume of distribution (Vd) in the first phase of the study was 0.43±0.12 L/kg, while on the seventh day of treatment it was 0.29±0.17 L/kg (p<0.001). Statistically significant differences were also observed for peak serum concentration (p<0.001), total dosage recommended (p<0.001) and half-life (p<0.05), whilst differences were not found for trough levels. From the analysis of the results obtained, we recommend increasing the initial dosage and monitoring plasma levels within the first days of therapy in critically ill patients treated with gentamicin, since important variations in aminoglycoside Vd related to disease, fluid balance and renal function, commonly occur in these patients.

Effect of Postextubation High-Flow Nasal Cannula vs Noninvasive Ventilation on Reintubation and Postextubation Respiratory Failure in High-Risk Patients: A Randomized Clinical Trial.

Importance High-flow conditioned oxygen therapy delivered through nasal cannulae and noninvasive mechanical ventilation (NIV) may reduce the need for reintubation. Among the advantages of high-flow oxygen therapy are comfort, availability, lower costs, and additional physiopathological mechanisms. Objective To test if high-flow conditioned oxygen therapy is noninferior to NIV for preventing postextubation respiratory failure and reintubation in patients at high risk of reintubation. Design, Setting, and Participants Multicenter randomized clinical trial in 3 intensive care units in Spain (September 2012-October 2014) including critically ill patients ready for planned extubation with at least 1 of the following high-risk factors for reintubation: older than 65 years; Acute Physiology and Chronic Health Evaluation II score higher than 12 points on extubation day; body mass index higher than 30; inadequate secretions management; difficult or prolonged weaning; more than 1 comorbidity; heart failure as primary indication for mechanical ventilation; moderate to severe chronic obstructive pulmonary disease; airway patency problems; or prolonged mechanical ventilation. Interventions Patients were randomized to undergo either high-flow conditioned oxygen therapy or NIV for 24 hours after extubation. Main Outcomes and Measures Primary outcomes were reintubation and postextubation respiratory failure within 72 hours. Noninferiority margin was 10 percentage points. Secondary outcomes included respiratory infection, sepsis, and multiple organ failure, length of stay and mortality; adverse events; and time to reintubation. Results Of 604 patients (mean age, 65 [SD, 16] years; 388 [64%] men), 314 received NIV and 290 high-flow oxygen. Sixty-six patients (22.8%) in the high-flow group vs 60 (19.1%) in the NIV group were reintubation (absolute difference, -3.7%; 95% CI, -9.1% to ∞); 78 patients (26.9%) in the high-flow group vs 125 (39.8%) in the NIV group experienced postextubation respiratory failure (risk difference, 12.9%; 95% CI, 6.6% to ∞) [corrected]. Median time to reintubation did not significantly differ: 26.5 hours (IQR, 14-39 hours) in the high-flow group vs 21.5 hours (IQR, 10-47 hours) in the NIV group (absolute difference, -5 hours; 95% CI, -34 to 24 hours). Median postrandomization ICU length of stay was lower in the high-flow group, 3 days (IQR, 2-7) vs 4 days (IQR, 2-9; P=.048). Other secondary outcomes were similar in the 2 groups. Adverse effects requiring withdrawal of the therapy were observed in none of patients in the high-flow group vs 42.9% patients in the NIV group (P < .001). Conclusions and Relevance Among high-risk adults who have undergone extubation, high-flow conditioned oxygen therapy was not inferior to NIV for preventing reintubation and postextubation respiratory failure. High-flow conditioned oxygen therapy may offer advantages for these patients. Trial Registration clinicaltrials.gov Identifier: NCT01191489.

Pressure support ventilation via face mask in acute respiratory failure in hypercapnic COPD patients.

ObjectiveTo test whether non-invasive ventilation via facial mask could reduce the need for tracheal intubation via when mechanical ventilation must be initiated in COPD patients.DesignOpen prospective interventional study.SettingGeneral Intensive Care Service of a County Hospital.PatientsWe have studied 12 COPD patients during 14 episodes of acute exacerbation of chronic respiratory failure who failed to improve with intensive medical therapy and showed impairements in severe respiratory acidosis and/or hypercapnic encephalopathy leading their attending physicians to order mechanical ventilationInterventionsIn these circumstances, a trial of pressuresupport (PS) ventilation (Servo Ventilator 900Cℜ) via facial mask Vital Signs Inc.ℜ) was performed. The level of pressure support was adjusted to obtain a tidal volume>400 ml. If the patient deteriorated, tracheal intubation and standard mechanical ventilation were performed.Measurements and resultsMeasurements are presented as means±SEM. A pressure-support level of 14±3 cmH2O was used during a period of 8±4 h. Low levels of external PEEP were used in 4 patients, while it generated excessive leaks in the others. Significant differences (p<0.05 ANOVA for repeated measures) in data obtained on admission, when patients deteriorated and after pressure support was administered were only observed in PaCO2 (68±3 versus 92±3 versus 67±3 mmHg), arterial pH (7.27±0.03 versus 7.19±0.02 versus 7.31±0.01). SaO2 (60±4 versus 86±3 versus 92±1%) and respiratory rate (35±2 versus 32±2 versus 23±1 breaths·min−1). Three patients needed intubation and one of them died in the ICU.ConclusionNon-invasive ventilation (pressure-support) via face mask may reduce the need for tracheal intubation in the severe hypercapnic failure of COPD patients.

Effect of acute moderate changes in PaCO2 on global hemodynamics and gastric perfusion.

Objective: To describe global hemodynamics and splanchnic perfusion changes in response to acute modifications in PaCO2 in hemodynamically stable patients. Design: Prospective, randomized crossover study. Setting: Medical‐surgical intensive care unit at a community hospital (400,000 inhabitants). Patients: Ten critically III patients who were sedated, paralyzed, and mechanically ventilated. Interventions: Hypercapnia and hypocapnia were obtained by increasing and reducing instrumental deadspace in random order. After each intervention, patients returned to the basal condition. Each period lasted 80 min: 20 min to achieve stable PaCO2 and 60 min for tonometer equilibration. In each period, global hemodynamic variables and tonometric data were collected. The periods were compared using analysis of variance. Measurements and Main Results: Acute hypercapnia (PaCO2 from 40 ± 3 to 52 ± 3 torr, p < .05) increased cardiac index (3.43 ± 0.37 vs. 3.97 ± 0.43 mL/min/m2, p < .05), heart rate (95 ± 6 vs. 105 ± 3 beats/min, p < .05), and mean pulmonary artery pressure (21 ± 1 vs. 24 ± 1 mm Hg, p < .05) and reduced systemic vascular resistance (992 ± 98 vs. 813 ± 93 dyne‐sec/cm5, p < .05) and oxygen extraction ratio (27 ± 3% vs. 22 ± 2%, p < .05). Standardized intramucosal PCO2 increased from 49 ± 2 to 61 ± 3 torr (p < .05) with an associated decrease in calculated intramucosal pH ([pHi] 7.35 ± 0.03 vs. 7.25 ± 0.02, p < .05), but the gastro‐arterial PCO2 gradient (ΔPCO2) did not change. Acute hypocapnia (PaCO2 from 41 ± 3 to 34 ± 3 torr, p < .05; pH 7.41 ± 0.01 to 7.47 ± 0.02, p < .05) induced slight increments in systemic vascular resistance (995 ± 117 vs. 1088 ± 160 dyne·sec/cm5, p < .05) and oxygen extraction ratio (28 ± 2% vs. 30 ± 2%, p < .05). Standardized intramucosal PCO2 decreased (50 ± 4 vs. 44 ± 3 torr, p < .05), pHi increased (7.33 ± 0.03 vs. 7.36 ± 0.02; p < .05), but ΔPCO2 did not change. Conclusions: In this small group of stable patients, moderate acute variations in PaCO2 had a significant effect on global hemodynamics, but splanchnic perfusion, assessed by ΔPCO2, did not change. In these conditions, the use of pHi to evaluate gastric perfusion appears unreliable.

Effect of prone positioning during mechanical ventilation on mortality among patients with acute respiratory distress syndrome: a systematic review and meta-analysis

Background: Mechanical ventilation in the prone position is used to improve oxygenation and to mitigate the harmful effects of mechanical ventilation in patients with acute respiratory distress syndrome (ARDS). We sought to determine the effect of prone positioning on mortality among patients with ARDS receiving protective lung ventilation. Methods: We searched electronic databases and conference proceedings to identify relevant randomized controlled trials (RCTs) published through August 2013. We included RCTs that compared prone and supine positioning during mechanical ventilation in patients with ARDS. We assessed risk of bias and obtained data on all-cause mortality (determined at hospital discharge or, if unavailable, after longest follow-up period). We used random-effects models for the pooled analyses. Results: We identified 11 RCTs (n = 2341) that met our inclusion criteria. In the 6 trials (n = 1016) that used a protective ventilation strategy with reduced tidal volumes, prone positioning significantly reduced mortality (risk ratio 0.74, 95% confidence interval 0.59–0.95; I2 = 29%) compared with supine positioning. The mortality benefit remained in several sensitivity analyses. The overall quality of evidence was high. The risk of bias was low in all of the trials except one, which was small. Statistical heterogeneity was low (I2 < 50%) for most of the clinical and physiologic outcomes. Interpretation: Our analysis of high-quality evidence showed that use of the prone position during mechanical ventilation improved survival among patients with ARDS who received protective lung ventilation.

Noninvasive Ventilation Reduces Intubation in Chest Trauma-Related Hypoxemia: A Randomized Clinical Trial

BACKGROUND Guidelines for noninvasive mechanical ventilation (NIMV) recommend continuous positive airway pressure in patients with thoracic trauma who remain hypoxic despite regional anesthesia. This recommendation is rated only by level C evidence because randomized controlled trials in this specific population are lacking. Our aim was to determine whether NIMV reduces intubation in severe trauma-related hypoxemia. METHODS This was a single-center randomized clinical trial in a nine-bed ICU of a level I trauma hospital. Inclusion criteria were patients with Pao(2)/Fio(2)<200 for >8 h while receiving oxygen by high-flow mask within the first 48 h after thoracic trauma. Patients were randomized to remain on high-flow oxygen mask or to receive NIMV. The interface was selected based on the associated injuries. Thoracic anesthesia was universally supplied unless contraindicated. The primary end point was intubation; secondary end points included length of hospital stay and survival. Statistical analysis was based on multivariate analysis. RESULTS After 25 patients were enrolled in each group, the trial was prematurely stopped for efficacy because the intubation rate was much higher in controls than in NIMV patients (10 [40%] vs 3 [12%], P = .02). Multivariate analysis adjusted for age, gender, chronic heart failure, and Acute Physiology and Chronic Health Evaluation II at admission revealed NIMV as the only variable independently related to intubation (odds ratio, 0.12; 95% CI, 0.02-0.61; P = .01). Length of hospital stay was shorter in NIMV patients (14 vs 21 days P = .001), but no differences were observed in survival or other secondary end points. CONCLUSION NIMV reduced intubation compared with oxygen therapy in severe thoracic trauma-related hypoxemia.