Mean Airway Pressure As a Predictor of 90-Day Mortality in Mechanically Ventilated Patients.

OBJECTIVES: To determine the association between mean airway pressure and 90-day mortality in patients with acute respiratory failure requiring mechanical ventilation and to compare the predictive ability of mean airway pressure compared with inspiratory plateau pressure and driving pressure. DESIGN: Prospective observational cohort. SETTING: Five ICUs in Lima, Peru. SUBJECTS: Adults requiring invasive mechanical ventilation via endotracheal tube for acute respiratory failure. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Of potentially eligible participants (n = 1,500), 65 (4%) were missing baseline mean airway pressure, while 352 (23.5%) were missing baseline plateau pressure and driving pressure. Ultimately, 1,429 participants were included in the analysis with an average age of 59 ± 19 years, 45% female, and a mean PaO2/FIO2 ratio of 248 ± 147 mm Hg at baseline. Overall, 90-day mortality was 50.4%. Median baseline mean airway pressure was 13 cm H2O (interquartile range, 10-16 cm H2O) in participants who died compared to a median mean airway pressure of 12 cm H2O (interquartile range, 10-14 cm H2O) in participants who survived greater than 90 days (p < 0.001). Mean airway pressure was independently associated with 90-day mortality (odds ratio, 1.38 for difference comparing the 75th to the 25th percentile for mean airway pressure; 95% CI, 1.10-1.74) after adjusting for age, sex, baseline Acute Physiology and Chronic Health Evaluation III, baseline PaO2/FIO2 (modeled with restricted cubic spline), baseline positive end-expiratory pressure, baseline tidal volume, and hospital site. In predicting 90-day mortality, baseline mean airway pressure demonstrated similar discriminative ability (adjusted area under the curve = 0.69) and calibration characteristics as baseline plateau pressure and driving pressure. CONCLUSIONS: In a multicenter prospective cohort, baseline mean airway pressure was independently associated with 90-day mortality in mechanically ventilated participants and predicts mortality similarly to plateau pressure and driving pressure. Because mean airway pressure is readily available on all mechanically ventilated patients and all ventilator modes, it is a potentially more useful predictor of mortality in acute respiratory failure.

Premature, Opportune, and Delayed Weaning in Mechanically Ventilated Patients: A Call for Implementation of Weaning Protocols in Low- and Middle-Income Countries.

OBJECTIVES: Weaning protocols establish readiness-to-wean criteria to determine the opportune moment to conduct a spontaneous breathing trial. Weaning protocols have not been widely adopted or evaluated in ICUs in low- and middle-income countries. We sought to compare clinical outcomes between participants whose weaning trials were retrospectively determined to have been premature, opportune, or delayed based on when they met readiness-to-wean criteria. DESIGN: Prospective, multicenter observational study. SETTING: Five medical ICUs in four public hospitals in Lima, Perú. SUBJECTS: Adults with acute respiratory failure and at least 24 hours of invasive mechanical ventilation (n = 1,657). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: We established six readiness-to-wean criteria and retrospectively categorized our sample into three weaning groups: 1) premature: if the weaning trial took place before fulfilling all criteria, 2) opportune: if the weaning trial took place within 24 hours after fulfilling the criteria, and 3) delayed: if the weaning trial took place over 24 hours after fulfilling criteria. We compared 90-day mortality, ventilator-free days, ICU-free days, and hospital-free days between premature, opportune, and delayed weaning groups. In our sample, 761 participants (60.8%) were classified as having a premature weaning trial, 196 underwent opportune weaning (15.7%), and 295 experienced delayed weaning (23.6%). There was no significant difference in 90-day mortality between the groups. Both the premature and delayed weaning groups had poorer clinical outcomes with fewer ventilator-free days (-2.18, p = 0.008) and (-3.49, p < 0.001), ICU-free days (-2.25, p = 0.001) and (-3.72, p < 0.001), and hospital-free days (-2.76, p = 0.044) and (-4.53, p = 0.004), respectively, compared with the opportune weaning group. CONCLUSIONS: Better clinical outcomes occur with opportune weaning compared with premature and delayed weaning. If readiness-to-wean criteria can be applied in resource-limited settings, it may improve ICU outcomes associated with opportune weaning.

Risk factors for the development of acute respiratory distress syndrome in mechanically ventilated adults in Peru: a multicenter observational study.

BACKGROUND: Clinical and epidemiological differences between acute respiratory distress syndrome (ARDS) that presents at the initiation of mechanical ventilation [MV] (ARDS at MV onset) and that which develops during the course of MV (ARDS after MV onset) are not well understood. We conducted an observational study in five Peruvian ICUs to characterize differences between ARDS at MV onset and after MV onset and identify risk factors for the development of ARDS after MV onset. METHODS: We consecutively enrolled critically ill patients with acute respiratory failure requiring at least 24 h of mechanical ventilation and followed them prospectively during the first 28 days and compared baseline characteristics and clinical outcomes by ARDS status. RESULTS: We enrolled 1657 participants on MV (mean age 60.0 years, 55% males) of whom 334 (20.2%) had ARDS at MV onset and 180 (10.9%) developed ARDS after MV onset. Average tidal volume at the initiation of MV was 8.7 mL/kg of predicted body weight (PBW) for participants with ARDS at MV onset, 8.6 mL/kg PBW for those who developed ARDS after MV onset, and 8.5 mL/kg PBW for those who never developed ARDS (p = 0.23). Overall, 90-day mortality was 56% and 55% for ARDS after MV onset and ARDS at MV onset, respectively, as compared to 46% among those who never developed ARDS (p < 0.01). Adults with ARDS had a higher body mass index (BMI) than those without ARDS (27.3 vs 26.5 kg/m2, p < 0.01). Higher peak pressure (adjusted interquartile OR = 1.51, 95% CI 1.21-1.88), higher mean airway pressure (adjusted interquartile OR = 1.41, 95% CI 1.13-1.76), and higher positive end-expiratory pressure (adjusted interquartile OR = 1.29, 95% CI 1.10-1.50) at MV onset were associated with a higher odds of developing ARDS after MV onset. CONCLUSIONS: In this study of mechanically ventilated patients, 31% of study participants had ARDS at some point during their ICU stay. Optimal lung-protective ventilation was not used in a majority of patients. Patients with ARDS after MV onset had a similar 90-day mortality as those with ARDS at MV onset. Higher airway pressures at MV onset, higher PEEP, and higher BMI were associated with the development of ARDS after MV onset.

Sedation practices and clinical outcomes in mechanically ventilated patients in a prospective multicenter cohort.

OBJECTIVES: We sought to study the association between sedation status, medications (benzodiazepines, opioids, and antipsychotics), and clinical outcomes in a resource-limited setting. DESIGN: A longitudinal study of critically ill participants on mechanical ventilation. SETTING: Five intensive care units (ICUs) in four public hospitals in Lima, Peru. PATIENTS: One thousand six hundred fifty-seven critically ill participants were assessed daily for sedation status during 28 days and vital status by day 90. RESULTS: After excluding data of participants without a Richmond Agitation Sedation Scale score and without sedation, we followed 1338 (81%) participants longitudinally for 18,645 ICU days. Deep sedation was present in 98% of participants at some point of the study and in 12,942 ICU days. Deep sedation was associated with higher mortality (interquartile odds ratio (OR) = 5.42, 4.23-6.95; p < 0.001) and a significant decrease in ventilator (- 7.27; p < 0.001), ICU (- 4.38; p < 0.001), and hospital (- 7.00; p < 0.001) free days. Agitation was also associated with higher mortality (OR = 39.9, 6.53-243, p < 0.001). The most commonly used sedatives were opioids and benzodiazepines (9259 and 8453 patient days respectively), and the latter were associated with a 41% higher mortality in participants with a higher cumulative dose (75th vs 25th percentile, interquartile OR = 1.41, 1.12-1.77; p < 0.01). The overall cumulative dose of benzodiazepines and opioids was high, 774.5 mg and 16.8 g, respectively, by day 7 and by day 28; these doses approximately doubled. Haloperidol was only used in 3% of ICU days; however, the use of it was associated with a 70% lower mortality (interquartile OR = 0.3, 0.22-0.44, p < 0.001). CONCLUSIONS: Deep sedation, agitation, and cumulative dose of benzodiazepines were all independently associated with higher 90-day mortality. Additionally, deep sedation was associated with less ventilator-, ICU-, and hospital-free days. In contrast, haloperidol was associated with lower mortality in our study.

Establishment of a prospective cohort of mechanically ventilated patients in five intensive care units in Lima, Peru: protocol and organisational characteristics of participating centres.

INTRODUCTION: Mechanical ventilation is a cornerstone in the management of critically ill patients worldwide; however, less is known about the clinical management of mechanically ventilated patients in low and middle income countries where limitation of resources including equipment, staff and access to medical information may play an important role in defining patient-centred outcomes. We present the design of a prospective, longitudinal study of mechanically ventilated patients in Peru that aims to describe a large cohort of mechanically ventilated patients and identify practices that, if modified, could result in improved patient-centred outcomes and lower costs. METHODS AND ANALYSIS: Five Peruvian intensive care units (ICUs) and the Medical ICU at the Johns Hopkins Hospital were selected for this study. Eligible patients were those who underwent at least 24 h of invasive mechanical ventilation within the first 48 h of admission into the ICU. Information on ventilator settings, clinical management and treatment were collected daily for up to 28 days or until the patient was discharged from the unit. Vital status was assessed at 90 days post enrolment. A subset of participants who survived until hospital discharge were asked to participate in an ancillary study to assess vital status, and physical and mental health at 6, 12, 24 and 60 months after hospitalisation, Primary outcomes include 90-day mortality, time on mechanical ventilation, hospital and ICU lengths of stay, and prevalence of acute respiratory distress syndrome. In subsequent analyses, we aim to identify interventions and standardised care strategies that can be tailored to resource-limited settings and that result in improved patient-centred outcomes and lower costs. ETHICS AND DISSEMINATION: We obtained ethics approval from each of the four participating hospitals in Lima, Peru, and at the Johns Hopkins School of Medicine, Baltimore, USA. Results will be disseminated as several separate publications in different international journals.

Acetazolamide: a treatment for chronic mountain sickness.

RATIONALE: Chronic mountain sickness or Monge's disease is characterized by an excessive polycythemia in high-altitude dwellers, with a prevalence of 5 to 18% above 3,200 m. To date, no pharmacologic treatment is available. OBJECTIVES: We evaluated the efficacy of acetazolamide in the treatment of chronic mountain sickness and the importance of nocturnal hypoxemia in its pathophysiology. METHODS: A double-blind placebo-controlled study was performed in three groups of patients from Cerro de Pasco, Peru (4,300 m), treated orally for 3 weeks with placebo (n = 10), 250 mg of acetazolamide (n = 10), or 500 mg of acetazolamide (n = 10), daily. RESULTS: Acetazolamide decreased hematocrit by 7.1% (p < 0.001) and 6.7% (p < 0.001), serum erythropoietin by 67% (p < 0.01) and 50% (p < 0.001), and serum soluble transferrin receptors by 11.1% (p < 0.05) and 3.4% (p < 0.001), and increased serum ferritin by 540% (p < 0.001) and 134% (p < 0.001), for groups treated with 250 and 500 mg of acetazolamide, respectively. Acetazolamide (250 mg) increased nocturnal arterial O(2) saturation by 5% (p < 0.01) and decreased mean nocturnal heart rate by 11% (p < 0.05) and the number of apnea-hypopnea episodes during sleep by 74% (p < 0.05). The decrease in erythropoietin was attributed mainly to the acetazolamide-induced increase in ventilation and arterial O(2) saturation. CONCLUSIONS: Acetazolamide, the first efficient pharmacologic treatment of chronic mountain sickness without adverse effects, reduces hypoventilation, which may be accentuated during sleep, and blunts erythropoiesis. Its low cost may allow wide development with a considerable positive impact on public health in high-altitude regions.