Influenza vaccination strategy in acute coronary syndromes: the VIP-ACS trial.

AIMS: To evaluate whether a strategy of double-dose influenza vaccination during hospitalization for an acute coronary syndrome (ACS) compared with standard-dose outpatient vaccination (as recommended by current guidelines) would further reduce the risk of major cardiopulmonary events. METHODS AND RESULTS: Vaccination against Influenza to Prevent cardiovascular events after Acute Coronary Syndromes (VIP-ACS) was a pragmatic, randomized, multicentre, active-comparator, open-label trial with blinded outcome adjudication comparing two strategies of influenza vaccination following an ACS: double-dose quadrivalent inactivated vaccine before hospital discharge vs. standard-dose quadrivalent inactivated vaccine administered in the outpatient setting 30 days after randomization. The primary outcome was a hierarchical composite of all-cause death, myocardial infarction, stroke, unstable angina, hospitalization for heart failure, urgent coronary revascularization, and hospitalization for respiratory causes, analysed by the win ratio method. Patients were followed for 12 months. During two influenza seasons, 1801 participants were included at 25 centres in Brazil. The primary outcome was not different between groups, with 12.7% wins in-hospital double-dose vaccine group and 12.3% wins in the standard-dose vaccine group {win ratio: 1.02 [95% confidence interval (CI): 0.79-1.32], P = 0.84}. Results were consistent for the key secondary outcome, a hierarchical composite of cardiovascular death, myocardial infarction and stroke [win ratio: 0.94 (95% CI: 0.66-1.33), P = 0.72]. Time-to-first event analysis for the primary outcome showed results similar to those of the main analysis [hazard ratio 0.97 (95% CI: 0.75-1.24), P = 0.79]. Adverse events were infrequent and did not differ between groups. CONCLUSION: Among patients hospitalized with an ACS, double-dose influenza vaccination before discharge did not reduce cardiopulmonary outcomes compared with standard-dose vaccination in the outpatient setting. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov number: NCT04001504.

Azithromycin in addition to standard of care versus standard of care alone in the treatment of patients admitted to the hospital with severe COVID-19 in Brazil (COALITION II): a randomised clinical trial.

BACKGROUND: The efficacy and safety of azithromycin in the treatment of COVID-19 remain uncertain. We assessed whether adding azithromycin to standard of care, which included hydroxychloroquine, would improve clinical outcomes of patients admitted to the hospital with severe COVID-19. METHODS: We did an open-label, randomised clinical trial at 57 centres in Brazil. We enrolled patients admitted to hospital with suspected or confirmed COVID-19 and at least one additional severity criteria as follows: use of oxygen supplementation of more than 4 L/min flow; use of high-flow nasal cannula; use of non-invasive mechanical ventilation; or use of invasive mechanical ventilation. Patients were randomly assigned (1:1) to azithromycin (500 mg via oral, nasogastric, or intravenous administration once daily for 10 days) plus standard of care or to standard of care without macrolides. All patients received hydroxychloroquine (400 mg twice daily for 10 days) because that was part of standard of care treatment in Brazil for patients with severe COVID-19. The primary outcome, assessed by an independent adjudication committee masked to treatment allocation, was clinical status at day 15 after randomisation, assessed by a six-point ordinal scale, with levels ranging from 1 to 6 and higher scores indicating a worse condition (with odds ratio [OR] greater than 1·00 favouring the control group). The primary outcome was assessed in all patients in the intention-to-treat (ITT) population who had severe acute respiratory syndrome coronavirus 2 infection confirmed by molecular or serological testing before randomisation (ie, modified ITT [mITT] population). Safety was assessed in all patients according to which treatment they received, regardless of original group assignment. This trial was registered at ClinicalTrials.gov, NCT04321278. FINDINGS: 447 patients were enrolled from March 28 to May 19, 2020. COVID-19 was confirmed in 397 patients who constituted the mITT population, of whom 214 were assigned to the azithromycin group and 183 to the control group. In the mITT population, the primary endpoint was not significantly different between the azithromycin and control groups (OR 1·36 [95% CI 0·94-1·97], p=0·11). Rates of adverse events, including clinically relevant ventricular arrhythmias, resuscitated cardiac arrest, acute kidney failure, and corrected QT interval prolongation, were not significantly different between groups. INTERPRETATION: In patients with severe COVID-19, adding azithromycin to standard of care treatment (which included hydroxychloroquine) did not improve clinical outcomes. Our findings do not support the routine use of azithromycin in combination with hydroxychloroquine in patients with severe COVID-19. FUNDING: COALITION COVID-19 Brazil and EMS.

Mechanical power of ventilation is associated with mortality in critically ill patients: an analysis of patients in two observational cohorts.

PURPOSE: Mechanical power (MP) may unify variables known to be related to development of ventilator-induced lung injury. The aim of this study is to examine the association between MP and mortality in critically ill patients receiving invasive ventilation for at least 48 h. METHODS: This is an analysis of data stored in the databases of the MIMIC-III and eICU. Critically ill patients receiving invasive ventilation for at least 48 h were included. The exposure of interest was MP. The primary outcome was in-hospital mortality. RESULTS: Data from 8207 patients were analyzed. Median MP during the second 24 h was 21.4 (16.2-28.1) J/min in MIMIC-III and 16.0 (11.7-22.1) J/min in eICU. MP was independently associated with in-hospital mortality [odds ratio per 5 J/min increase (OR) 1.06 (95% confidence interval (CI) 1.01-1.11); p = 0.021 in MIMIC-III, and 1.10 (1.02-1.18); p = 0.010 in eICU]. MP was also associated with ICU mortality, 30-day mortality, and with ventilator-free days, ICU and hospital length of stay. Even at low tidal volume, high MP was associated with in-hospital mortality [OR 1.70 (1.32-2.18); p < 0.001] and other secondary outcomes. Finally, there is a consistent increase in the risk of death with MP higher than 17.0 J/min. CONCLUSION: High MP of ventilation is independently associated with higher in-hospital mortality and several other outcomes in ICU patients receiving invasive ventilation for at least 48 h.

Handovers Among Staff Intensivists: A Study of Information Loss and Clinical Accuracy to Anticipate Events.

OBJECTIVES: Handovers are associated with medical errors, and our primary objective is to identify missed diagnosis and goals immediately after a shift handover. Our secondary objective is to assess clinicians' diagnostic accuracy in anticipating clinical events during the night shift. DESIGN: Single-center prospective observational cohort study. SETTING: Thirty-bed tertiary ICU in Sao Paulo, Brazil. PATIENTS: Three-hundred fifty-two patient encounters over 44 day-to-night handovers. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: We used a multimethods approach to measure transmission of information among staff physicians on diagnoses and goals for the night shift. We surveyed clinicians immediately after a handover and identified clinical events through chart abstractions and interviews with clinicians the next morning. Nighttime clinicians correctly identified 454 of 857 diagnoses (53%; 95% CI 50-56) and 123 of 304 goals (40%; 95% CI, 35-46). Daytime clinicians were more sensitive (65% vs 46%; p < 0.01) but less specific (82% vs 91%; p < 0.01) than nighttime clinicians in anticipating clinical events at night, resulting in similar accuracy (area under the receiver operating characteristic curve, 0.74 [95% CI, 0.68-0.79] vs 0.68 [95% CI 0.63-0.74]; p = 0.09). The positive predictive value of both daytime and nighttime clinicians was low (13% vs 17%; p = 0.2). Gaps in diagnosis and anticipation of events were more pronounced in neurologic diagnoses. CONCLUSIONS: Among staff intensivists, diagnoses and goals of treatment are either not conveyed or retained 50-60% of the cases immediately after a handover. Clinicians have limited ability to anticipate events, and the expectation that anticipatory guidance can inform handovers needs to be balanced against information overload. Handovers among staff intensivists showed more gaps in the identification of diagnostic uncertainty and for neurologic diagnoses, which could benefit from communication strategies such as cognitive checklists, prioritizing discussion of neurologic patients, and brief combined clinical examination at handover.

Readmission to the Intensive Care Unit: Incidence, Risk Factors, Resource Use, and Outcomes. A Retrospective Cohort Study.

RATIONALE: Readmission to the intensive care unit (ICU) is associated with poor clinical outcomes, increased length of ICU and hospital stay, and higher costs. Nevertheless, knowledge of epidemiology of ICU readmissions, risk factors, and attributable outcomes is restricted to developed countries. OBJECTIVES: To determine the effect of ICU readmissions on in-hospital mortality, determine incidence of ICU readmissions, identify predictors of ICU readmissions and hospital mortality, and compare resource use and outcomes between readmitted and nonreadmitted patients in a developing country. METHODS: This retrospective single-center cohort study was conducted in a 40-bed, open medical-surgical ICU of a private, tertiary care hospital in São Paulo, Brazil. The Local Ethics Committee at Hospital Israelita Albert Einstein approved the study protocol, and the need for informed consent was waived. All consecutive adult (≥18 yr) patients admitted to the ICU between June 1, 2013 and July 1, 2015 were enrolled in this study. RESULTS: Comparisons were made between patients readmitted and not readmitted to the ICU. Logistic regression analyses were performed to identify predictors of ICU readmissions and hospital mortality. Out of 5,779 patients admitted to the ICU, 576 (10%) were readmitted to the ICU during the same hospitalization. Compared with nonreadmitted patients, patients readmitted to the ICU were more often men (349 of 576 patients [60.6%] vs. 2,919 of 5,203 patients [56.1%]; P = 0.042), showed a higher (median [interquartile range]) severity of illness (Simplified Acute Physiology III score) at index ICU admission (50 [41-61] vs. 42 [32-54], respectively, for readmitted and nonreadmitted patients; P < 0.001), and were more frequently admitted due to medical reasons (425 of 576 [73.8%] vs. 2,998 of 5,203 [57.6%], respectively, for readmitted and nonreadmitted patients; P < 0.001). Simplified Acute Physiology III score (P < 0.001), ICU admission from the ward (odds ratio [OR], 1.907; 95% confidence interval [CI], 1.463-2.487; P < 0.001), vasopressors need during index ICU stay (OR, 1.391; 95% CI, 1.130-1.713; P = 0.002), and length of ICU stay (P = 0.001) were independent predictors of ICU readmission. After adjusting for severity of illness, ICU readmission (OR, 4.103; 95% CI, 3.226-5.518; P < 0.001), admission source, presence of cancer, use of vasopressors, mechanical ventilation or renal replacement therapy, length of ICU stay, and nighttime ICU discharge were associated with increased risk of in-hospital death. CONCLUSIONS: Readmissions to the ICU were frequent and strongly related to poor outcomes. The degree to which ICU readmissions are preventable as well as the main causes of preventable ICU readmissions need to be further determined.

Smart Care™ versus respiratory physiotherapy-driven manual weaning for critically ill adult patients: a randomized controlled trial.

INTRODUCTION: A recent meta-analysis showed that weaning with SmartCare™ (Dräger, Lübeck, Germany) significantly decreased weaning time in critically ill patients. However, its utility compared with respiratory physiotherapist-protocolized weaning is still a matter of debate. We hypothesized that weaning with SmartCare™ would be as effective as respiratory physiotherapy-driven weaning in critically ill patients. METHODS: Adult critically ill patients mechanically ventilated for more than 24 hours in the adult intensive care unit of the Albert Einstein Hospital, São Paulo, Brazil, were randomly assigned to be weaned either by progressive discontinuation of pressure support ventilation (PSV) with SmartCare™. Demographic data, respiratory function parameters, level of PSV, tidal volume (VT), positive end-expiratory pressure (PEEP), inspired oxygen fraction (FIO2), peripheral oxygen saturation (SpO2), end-tidal carbon dioxide concentration (EtCO2) and airway occlusion pressure at 0.1 second (P0.1) were recorded at the beginning of the weaning process and before extubation. Mechanical ventilation time, weaning duration and rate of extubation failure were compared. RESULTS: Seventy patients were enrolled 35 in each group. There was no difference between the two groups concerning age, sex or diagnosis at study entry. There was no difference in maximal inspiratory pressure, maximal expiratory pressure, forced vital capacity or rapid shallow breathing index at the beginning of the weaning trial. PEEP, VT, FIO2, SpO2, respiratory rate, EtCO2 and P0.1 were similar between the two groups, but PSV was not (median: 8 vs. 10 cmH2O; p =0.007). When the patients were ready for extubation, PSV (8 vs. 5 cmH2O; p =0.015) and PEEP (8 vs. 5 cmH2O; p <0.001) were significantly higher in the respiratory physiotherapy-driven weaning group. Total duration of mechanical ventilation (3.5 [2.0-7.3] days vs. 4.1 [2.7-7.1] days; p =0.467) and extubation failure (2 vs. 2; p =1.00) were similar between the two groups. Weaning duration was shorter in the respiratory physiotherapy-driven weaning group (60 [50-80] minutes vs. 110 [80-130] minutes; p <0.001). CONCLUSION: A respiratory physiotherapy-driven weaning protocol can decrease weaning time compared with an automatic system, as it takes into account individual weaning difficulties. TRIAL REGISTRATION: Clinicaltrials.gov Identifier: NCT02122016 . Date of Registration: 27 August 2013.

Sepsis-related deaths in Brazil: an analysis of the national mortality registry from 2002 to 2010.

INTRODUCTION: Limited population-based epidemiologic information about sepsis' demography, including its mortality and temporal changes is available from developing countries. We investigated the epidemiology of sepsis deaths in Brazil using secondary data from the Brazilian Mortality Information System. METHODS: Retrospective descriptive analysis of Brazilian multiple-cause-of-death data between 2002 and 2010, with sepsis-associated International Classification of Diseases, 10th Revision (ICD-10) code indicated as the cause of death. Population-based sepsis associated mortality rates and trends were estimated. Annual population-based mortality rates were calculated using age-stratified population estimates from the 2010 census provided by the Brazilian Institute of Geography and Statistics as denominators. RESULTS: The total number of annual deaths recorded in Brazil increased over the decade, from 982,294 deaths reported in 2002 to 1,133,761 deaths reported in 2010. The number of sepsis associated deaths also increased both in absolute numbers and proportions from 95,972 (9.77% of total deaths) in 2002 to 186,712 deaths (16.46%) in 2010. The age-adjusted rate of sepsis-associated mortality increased from 69.5 deaths per 100,000 to 97.8 deaths per 100,000 population from 2002 to 2010 (P < 0.001). Sepsis-associated mortality was higher in individuals older than 60 years of age as compared to subjects aged 0 to 20 years (adjusted rate ratio 15.7 (95% confidence interval (CI) 15.6 to 15.8)) and in male subjects (1.15 (95% CI 1.15 to 1.16)). CONCLUSIONS: Between 2002 and 2010 the contribution of sepsis to all cause mortality as reported in multiple-cause-of-death forms increased significantly in Brazil. Age-adjusted mortality rates by sepsis also increased in the last decade. Our results confirm the importance of sepsis as a significant healthcare issue in Brazil.

Noninvasive ventilation immediately after extubation improves weaning outcome after acute respiratory failure: a randomized controlled trial.

INTRODUCTION: Noninvasive ventilation (NIV), as a weaning-facilitating strategy in predominantly chronic obstructive pulmonary disease (COPD) mechanically ventilated patients, is associated with reduced ventilator-associated pneumonia, total duration of mechanical ventilation, length of intensive care unit (ICU) and hospital stay, and mortality. However, this benefit after planned extubation in patients with acute respiratory failure of various etiologies remains to be elucidated. The aim of this study was to determine the efficacy of NIV applied immediately after planned extubation in contrast to oxygen mask (OM) in patients with acute respiratory failure (ARF). METHODS: A randomized, prospective, controlled, unblinded clinical study in a single center of a 24-bed adult general ICU in a university hospital was carried out in a 12-month period. Included patients met extubation criteria with at least 72 hours of mechanical ventilation due to acute respiratory failure, after following the ICU weaning protocol. Patients were randomized immediately before elective extubation, being randomly allocated to one of the study groups: NIV or OM. We compared both groups regarding gas exchange 15 minutes, 2 hours, and 24 hours after extubation, reintubation rate after 48 hours, duration of mechanical ventilation, ICU length of stay, and hospital mortality. RESULTS: Forty patients were randomized to receive NIV (20 patients) or OM (20 patients) after the following extubation criteria were met: pressure support (PSV) of 7 cm H2O, positive end-expiratory pressure (PEEP) of 5 cm H2O, oxygen inspiratory fraction (FiO2)≤40%, arterial oxygen saturation (SaO2)≥90%, and ratio of respiratory rate and tidal volume in liters (f/TV)<105. Comparing the 20 patients (NIV) with the 18 patients (OM) that finished the study 48 hours after extubation, the rate of reintubation in NIV group was 5% and 39% in OM group (P=0.016). Relative risk for reintubation was 0.13 (CI=0.017 to 0.946). Absolute risk reduction for reintubation showed a decrease of 33.9%, and analysis of the number needed to treat was three. No difference was found in the length of ICU stay (P=0.681). Hospital mortality was zero in NIV group and 22.2% in OM group (P=0.041). CONCLUSIONS: In this study population, NIV prevented 48 hours reintubation if applied immediately after elective extubation in patients with more than 3 days of ARF when compared with the OM group. TRIAL REGISTRATION NUMBER ISRCTN: 41524441.

Time course of haemodynamic, respiratory and inflammatory disturbances induced by experimental acute pulmonary polystyrene microembolism.

BACKGROUND AND OBJECTIVE: The time course of cardiopulmonary alterations after pulmonary embolism has not been clearly demonstrated and nor has the role of systemic inflammation on the pathogenesis of the disease. This study aimed to evaluate over 12 h the effects of pulmonary embolism caused by polystyrene microspheres on the haemodynamics, lung mechanics and gas exchange and on interleukin-6 production. METHODS: Ten large white pigs (weight 35-42 kg) had arterial and pulmonary catheters inserted and pulmonary embolism was induced in five pigs by injection of polystyrene microspheres (diameter approximately 300 micromol l(-1)) until a value of pulmonary mean arterial pressure of twice the baseline was obtained. Five other animals received only saline. Haemodynamic and respiratory data and pressure-volume curves of the respiratory system were collected. A bronchoscopy was performed before and 12 h after embolism, when the animals were euthanized. RESULTS: The embolism group developed hypoxaemia that was not corrected with high oxygen fractions, as well as higher values of dead space, airway resistance and lower respiratory compliance levels. Acute haemodynamic alterations included pulmonary arterial hypertension with preserved systemic arterial pressure and cardiac index. These derangements persisted until the end of the experiments. The plasma interleukin-6 concentrations were similar in both groups; however, an increase in core temperature and a nonsignificant higher concentration of bronchoalveolar lavage proteins were found in the embolism group. CONCLUSION: Acute pulmonary embolism induced by polystyrene microspheres in pigs produces a 12-h lasting hypoxaemia and a high dead space associated with high airway resistance and low compliance. There were no plasma systemic markers of inflammation, but a higher central temperature and a trend towards higher bronchoalveolar lavage proteins were found.

Ventilação mecânica não-invasiva com pressão positiva / Noninvasive mechanical ventilation with positive pressure

JUSTIFICATIVA E OBJETIVOS: Em 2000, foi publicado o II Consenso Brasileiro de Ventilação Mecânica. Desde então, o conhecimento na área da ventilação mecânica avançou rapidamente, com a publicação de numerosos estudos clínicos que acrescentaram informações importantes para o manejo de pacientes críticos em ventilação artificial. Além disso, a expansão do conceito de Medicina Baseada em Evidências determinou a hierarquização das recomendações clínicas, segundo o rigor metodológico dos estudos que as embasaram. Essa abordagem explícita vem ampliando a compreensão e a aplicação das recomendações clínicas. Por esses motivos, a AMIB - Associação de Medicina Intensiva Brasileira - e a SBPT - Sociedade Brasileira de Pneumologia e Tisiologia - julgaram conveniente a atualização das recomendações descritas no Consenso anterior. Dentre os tópicos selecionados a Ventilação Mecânica Não-Invasiva foi um dos temas propostos. O objetivo deste estudo foi descrever os pontos mais importantes relacionados à ventilação mecânica na forma não-invasiva (VMNI) e sugerir as principais indicações dessa modalidade. MÉTODO: Objetivou-se chegar a um documento suficientemente sintético, que refletisse a melhor evidência disponível na literatura. A revisão bibliográfica baseou-se na busca de estudos através de palavras-chave e em sua gradação conforme níveis de evidência. As palavras-chave utilizadas para a busca foram: Ventilação mecânica não invasiva: Non-invasive mechanical ventilation. RESULTADOS: São apresentadas recomendações quanto à utilização da VMNI nas diversas formas de insuficiência respiratória e no desmame da ventilação mecânica. CONCLUSÕES: A VMNI está indicada como o tratamento preferencial na exacerbação da DPOC, assim como, na assistência de pacientes em edema agudo de pulmão.

BACKGROUND AND OBJECTIVES: The II Brazilian Consensus Conference on Mechanical Ventilation was published in 2000. Knowledge on the field of mechanical ventilation evolved rapidly since then, with the publication of numerous clinical studies with potential impact on the ventilatory management of critically ill patients. Moreover, the evolving concept of evidence - based medicine determined the grading of clinical recommendations according to the methodological value of the studies on which they are based. This explicit approach has broadened the understanding and adoption of clinical recommendations. For these reasons, AMIB - Associação de Medicina Intensiva Brasileira and SBPT - Sociedade Brasileira de Pneumologia e Tisiologia - decided to update the recommendations of the II Brazilian Consensus. Non-Invasive Mechanical ventilation has been one of the updated topics. Describe the most important topics on the non-invasive mechanical ventilation and suggest the main therapeutic approaches of this modality. METHODS: Systematic review of the published literature and gradation of the studies in levels of evidence, using the keywords "non-invasive mechanical ventilation". RESULTS: Recommendations on the non-invasive mechanical ventilation during respiratory failure and weaning are presented. CONCLUSIONS: Non-invasive mechanical ventilation is the main form of ventilatory support during exacerbation of chronic obstructive pulmonary disease and in acute pulmonary edema patients.

[Noninvasive mechanical ventilation with positive pressure]. / Ventilação mecânica não-invasiva com pressão positiva.

BACKGROUND AND OBJECTIVES: The II Brazilian Consensus Conference on Mechanical Ventilation was published in 2000. Knowledge on the field of mechanical ventilation evolved rapidly since then, with the publication of numerous clinical studies with potential impact on the ventilatory management of critically ill patients. Moreover, the evolving concept of evidence - based medicine determined the grading of clinical recommendations according to the methodological value of the studies on which they are based. This explicit approach has broadened the understanding and adoption of clinical recommendations. For these reasons, AMIB - Associação de Medicina Intensiva Brasileira and SBPT - Sociedade Brasileira de Pneumologia e Tisiologia - decided to update the recommendations of the II Brazilian Consensus. Non-Invasive Mechanical ventilation has been one of the updated topics. Describe the most important topics on the non-invasive mechanical ventilation and suggest the main therapeutic approaches of this modality. METHODS: Systematic review of the published literature and gradation of the studies in levels of evidence, using the keywords "non-invasive mechanical ventilation". RESULTS: Recommendations on the non-invasive mechanical ventilation during respiratory failure and weaning are presented. CONCLUSIONS: Non-invasive mechanical ventilation is the main form of ventilatory support during exacerbation of chronic obstructive pulmonary disease and in acute pulmonary edema patients.

Peak volume history and peak pressure-volume curve pressures independently affect the shape of the pressure-volume curve of the respiratory system.

OBJECTIVE: To determine the specific effect of peak volume history pressure on the inflation limb of the pressure-volume curve and peak pressure-volume curve pressure on the deflation limb of the pressure-volume curve. DESIGN: Prospective assessment of pressure-volume curves in saline, lung lavage injured sheep. SETTING: Large animal laboratory of a university-affiliated hospital. SUBJECTS: Eight female Dorset sheep. INTERVENTIONS: : The effect of two volume history pressures (40 and 60 cm H2O) and three pressure-volume curve peak pressures (40, 50, and 60 cm H2O) were randomly compared. MEASUREMENTS AND MAIN RESULTS: Peak volume history pressure affected the inflation curve beyond the lower inflection point but did not affect the inflection point (Pflex). Peak pressure-volume curve pressure affected the deflation curve. Increased peak volume history pressure increased inflation compliance (p <.05). Increased peak pressure-volume curve pressure increased the point of maximum compliance change on the deflation limb and deflation compliance and decreased compliance between peak pressure and the point of maximum curvature on the deflation limb (p <.05). CONCLUSION: Peak volume history pressure must be considered when interpreting the inflation limb of the pressure-volume curve of the respiratory system beyond the inflection point. The peak pressure achieved during the pressure-volume curve is important during interpretation of deflation compliance and the point of maximum compliance change on the deflation limb.

Position of exhalation port and mask design affect CO2 rebreathing during noninvasive positive pressure ventilation.

OBJECTIVE: Noninvasive positive pressure ventilation may be considered a first line intervention to treat patients with hypercapnic respiratory failure. However, CO2 rebreathing from the ventilator circuit or mask may impair CO2 elimination and load the ventilatory muscles. This study was conducted to evaluate the effect of exhalation port location and mask design on CO2 rebreathing during noninvasive positive pressure ventilation. DESIGN: Lung model evaluation. SETTING: Experimental laboratory of a large university-affiliated hospital. SUBJECTS: A dual-chamber test lung was used to simulate the ventilatory mechanics of a patient with obstructive lung disease. INTERVENTION: Hypercapnic respiratory failure (end-tidal CO2 of 75 mm Hg) and obstructive lung disease were simulated in a double-chamber lung model. A facial mask (inner volume of 165 mL) with exhalation port within the mask (Facial-MEP) or the same mask with exhalation port in the ventilator circuit (Facial-WS) and a total face mask with exhalation port within the mask (inner volume 875 mL, Total Face) were tested during continuous positive airway pressure and pressure support ventilation provided by a single-limb circuit ventilator at the same frequency and tidal volume. MEASUREMENTS AND MAIN RESULTS: A capnometer and a flow transducer were placed in the lung model upper airway to measure the volume of CO2 rebreathed and tidal volume (Vt). The inspiratory load was estimated from the pressure variation in the lung model driving chamber (PDR). Volume of CO2 rebreathed was smaller during Facial-MEP compared with the other masks in all tested conditions (p <.001). The Vt and PDR necessary to decrease end-tidal CO2 20% (from 75 to 60 mm Hg) was different among the tested masks (Facial-MEP, Vt 701 +/- 9 mL, PDR 8.1 +/- 0.1 cm H2O/sec; Facial-WS, Vt 745 +/- 9 mL, PDR 10.2 +/- 0.1 cm H2O/sec; Total Face, Vt 790 +/- 12 mL, PDR 11.4 +/- 0.2 cm H2O/sec, p <.001). CONCLUSION: Facial-MEP with its exhalation port within the mask and the smallest mask volume demonstrated less rebreathed CO2 and a lower PDR than either the Facial-WS or Total Face masks. Additional studies are necessary to confirm if mask design can clinically affect patient's inspiratory effort during noninvasive positive pressure ventilation.

In vitro evaluation of aerosol bronchodilator delivery during noninvasive positive pressure ventilation: effect of ventilator settings and nebulizer position.

OBJECTIVE: Respiratory failure due to exacerbation of obstructive lung disease has been successfully treated with noninvasive positive pressure ventilation (NPPV). However, there have been no reports of factors affecting aerosol delivery during NPPV. Our objective was to determine the effect of ventilator settings and nebulizer position on albuterol delivery during NPPV. DESIGN: Bench model study. SETTING: University laboratory. SUBJECTS: None. INTERVENTIONS: A Respironics BiPAP S/T-D30 with a standard circuit was attached to a lung model simulating spontaneous breathing. Inspiratory/expiratory pressures of 10/5, 15/5, 20/5, 15/10, 20/10, and 25/10 cm H2O were tested at respiratory rates of 10 and 20/min. A nebulizer was filled with 5 mg of albuterol in 4 mL of solution, driven with 8 L/min oxygen, and placed at either a proximal (ventilator outlet) or distal (between leak port and lung model connection) position. Albuterol delivery was estimated by measuring the amount of the albuterol collected on a filter placed at the inlet of the lung model. MEASUREMENT AND MAIN RESULTS: Albuterol delivery varied from 5.2 +/- 0.4% to 24.5 +/- 1.3% of the nominal dose and was significantly affected by the position of the nebulizer, respiratory rate, and BiPAP settings (p <.001 in each case). The greatest albuterol delivery was observed with the nebulizer operating at the distal position and a respiratory rate of 20/min. At this respiratory rate and nebulizer placement, albuterol delivery increased with increasing inspiratory pressure levels and decreased as expiratory pressure levels were increased. Nebulizer flow did not affect function of the ventilator. CONCLUSIONS: At optimum nebulizer position (between the leak port and patient connection) and ventilator settings (high inspiratory pressure and low expiratory pressure), as much as 25% of the nominal albuterol dose may be delivered during NPPV.