Challenges of Anesthetic Monitoring in Low- and Middle-Income Countries: Availability of Equipment in Major Referral Hospitals in Kenya.

BACKGROUND: Anesthetic monitoring within standards defined by various professional anesthesia organizations has been shown to reduce perioperative mortality. Given the scarce resources for anesthesia and surgery in low- to middle-income countries, we sought to determine the availability of recommended monitoring devices in major referral hospitals in Kenya. METHODS: We purposely selected the 16 major referral hospitals in Kenya. A cross-sectional survey was conducted in 103 operating theaters, 96 postanesthesia care unit (PACU) beds, and 16 areas where procedural sedation was routinely administered. A checklist questionnaire based on the Association of Anaesthetists of Great Britain and Ireland (AAGBI) guidelines of 2015 was used to determine the availability of basic and functional monitoring devices. RESULTS: We determined that only 1 of 16 (6.25%) hospitals had all the monitoring devices recommended by the AAGBI. Automated noninvasive blood pressure (NIBP) monitoring and pulse oximetry were present in all operating theaters. Continuous electrocardiography (ECG) was available in 102 of 103 (99%) operating theaters, skin temperature monitoring probes in 73 of 103 (70.9%), and capnography in 49 (47.6%). A nerve stimulator was accessible in 5 of 16 (31.25%) hospitals. There were functional patient monitors in all operating theaters (100%). One of the regional referral hospitals did not have a PACU. We encountered 9 of 96 (9.4%) PACU beds without any monitoring devices. Pulse oximetry was the most common device (84.4%) in the PACU beds equipped with monitoring. In 5 of 16 (31.25%) procedural sedation areas, pulse oximetry was the only monitoring device, whereas there were no devices in 2 of 16 (12.5%) areas. Portable multiparameter devices used for patient transport were present in 5 of 16 (31.25%) hospitals. CONCLUSIONS: The availability of recommended monitoring devices in major referral hospitals in Kenya is inadequate. Thus, there are challenges to anesthetic monitoring in these hospitals, and perioperative patient safety is jeopardized. We recommend the universal provision of basic monitoring devices and suggest the use of the data collected in this study to affect policy change and safe anesthesia practice in our country.

Respiratory System Mechanics During Low Versus High Positive End-Expiratory Pressure in Open Abdominal Surgery: A Substudy of PROVHILO Randomized Controlled Trial.

BACKGROUND: In the 2014 PROtective Ventilation using HIgh versus LOw positive end-expiratory pressure (PROVHILO) trial, intraoperative low tidal volume ventilation with high positive end-expiratory pressure (PEEP = 12 cm H2O) and lung recruitment maneuvers did not decrease postoperative pulmonary complications when compared to low PEEP (0-2 cm H2O) approach without recruitment breaths. However, effects of intraoperative PEEP on lung compliance remain poorly understood. We hypothesized that higher PEEP leads to a dominance of intratidal overdistension, whereas lower PEEP results in intratidal recruitment/derecruitment (R/D). To test our hypothesis, we used the volume-dependent elastance index %E2, a respiratory parameter that allows for noninvasive and radiation-free assessment of dominant overdistension and intratidal R/D. We compared the incidence of intratidal R/D, linear expansion, and overdistension by means of %E2 in a subset of the PROVHILO cohort. METHODS: In 36 patients from 2 participating centers of the PROVHILO trial, we calculated respiratory system elastance (E), resistance (R), and %E2, a surrogate parameter for intratidal overdistension (%E2 > 30%) and R/D (%E2 < 0%). To test the main hypothesis, we compared the incidence of intratidal overdistension (primary end point) and R/D in higher and lower PEEP groups, as measured by %E2. RESULTS: E was increased in the lower compared to higher PEEP group (18.6 [16…22] vs 13.4 [11.0…17.0] cm H2O·L; P < .01). %E2 was reduced in the lower PEEP group compared to higher PEEP (-15.4 [-28.0…6.5] vs 6.2 [-0.8…14.0] %; P < .05). Intratidal R/D was increased in the lower PEEP group (61% vs 22%; P = .037). The incidence of intratidal overdistension did not differ significantly between groups (6%). CONCLUSIONS: During mechanical ventilation with protective tidal volumes in patients undergoing open abdominal surgery, lung recruitment followed by PEEP of 12 cm H2O decreased the incidence of intratidal R/D and did not worsen overdistension, when compared to PEEP ≤2 cm H2O.

Association between pre-operative biological phenotypes and postoperative pulmonary complications: An unbiased cluster analysis.

BACKGROUND: Biological phenotypes have been identified within several heterogeneous pulmonary diseases, with potential therapeutic consequences. OBJECTIVE: To assess whether distinct biological phenotypes exist within surgical patients, and whether development of postoperative pulmonary complications (PPCs) and subsequent dependence of intra-operative positive end-expiratory pressure (PEEP) differ between such phenotypes. SETTING: Operating rooms of six hospitals in Europe and USA. DESIGN: Secondary analysis of the 'PROtective Ventilation with HIgh or LOw PEEP' trial. PATIENTS: Adult patients scheduled for abdominal surgery who are at risk of PPCs. INTERVENTIONS: Measurement of pre-operative concentrations of seven plasma biomarkers associated with inflammation and lung injury. MAIN OUTCOME MEASURES: We applied unbiased cluster analysis to identify biological phenotypes. We then compared the proportion of patients developing PPCs within each phenotype, and associations between intra-operative PEEP levels and development of PPCs among phenotypes. RESULTS: In total, 242 patients were included. Unbiased cluster analysis clustered the patients within two biological phenotypes. Patients with phenotype 1 had lower plasma concentrations of TNF-α (3.8 [2.4 to 5.9] vs. 10.2 [8.0 to 12.1] pg ml; P < 0.001), IL-6 (2.3 [1.5 to 4.0] vs. 4.0 [2.9 to 6.5] pg ml; P < 0.001) and IL-8 (4.7 [3.1 to 8.1] vs. 8.1 [6.0 to 13.9] pg ml; P < 0.001). Phenotype 2 patients had the highest incidence of PPC (69.8 vs. 34.2% in type 1; P < 0.001). There was no interaction between phenotype and PEEP level for the development of PPCs (43.2% in high PEEP vs. 25.6% in low PEEP in phenotype 1, and 73.6% in high PEEP and 65.7% in low PEEP in phenotype 2; P for interaction = 0.503). CONCLUSION: Patients at risk of PPCs and undergoing open abdominal surgery can be clustered based on pre-operative plasma biomarker concentrations. The two identified phenotypes have different incidences of PPCs. Biologic phenotyping could be useful in future randomised controlled trials of intra-operative ventilation. TRIAL REGISTRATION: The PROtective Ventilation with HIgh or LOw PEEP trial, including the substudy from which data were used for the present analysis, was registered at ClinicalTrials.gov (NCT01441791).

Kinetics of plasma biomarkers of inflammation and lung injury in surgical patients with or without postoperative pulmonary complications.

BACKGROUND: Postoperative pulmonary complications (PPCs) are common after major abdominal surgery. The kinetics of plasma biomarkers could improve identification of patients developing PPCs, but the kinetics may depend on intraoperative ventilator settings. OBJECTIVE: To test whether the kinetics of plasma biomarkers are capable of identifying patients who will develop PPCs, and whether the kinetics depend on the intraoperative level of positive end-expiratory pressure (PEEP). DESIGN: A preplanned substudy of a randomised controlled trial. SETTING: Operation room of five centres. PATIENTS: Two hundred and forty-two adult patients scheduled for abdominal surgery at risk of developing PPCs. INTERVENTIONS: High (12 cmH2O) versus low (≤2 cmH2O) levels of PEEP. MAIN OUTCOME MEASURES: Individual PPCs were combined as a composite endpoint. Plasma samples were collected before surgery, directly after surgery and on the fifth postoperative day. The levels of the following were measured: tumour necrosis factor (TNF)-α, interleukin (IL)-6 and IL-8, the soluble form of the Receptor for Advanced Glycation End-products (sRAGE), Surfactant Protein (SP)-D, Clara Cell protein (CC)-16 and Krebs von den Lungen 6 (KL6). RESULTS: Blood sampling was complete in 242 patients: 120 patients in the high PEEP group and 122 patients in the low PEEP group. Increases in plasma levels of TNF- IL-6, IL-8 and CC-16, and a decrease in plasma levels of SP-D were greater in patients who developed PPCs; however, the area under the receiver operating characteristic curve was low for all biomarkers. CC-16 was the only biomarker whose level increased more in patients who had received high levels of PEEP. CONCLUSION: In patients undergoing abdominal surgery and at risk of developing PPCs, plasma levels of biomarkers for inflammation or lung injury showed distinct kinetics with development of PPCs, but none of the biomarkers showed sufficient prognostic value. The use of high levels of PEEP was associated with increased levels of CC-16, suggesting lung overdistension. TRIAL REGISTRATION: The PROVHILO trial, including this substudy, was registered at clinicaltrials.gov (NCT01441791).

Open Lung Approach for the Acute Respiratory Distress Syndrome: A Pilot, Randomized Controlled Trial.

OBJECTIVE: The open lung approach is a mechanical ventilation strategy involving lung recruitment and a decremental positive end-expiratory pressure trial. We compared the Acute Respiratory Distress Syndrome network protocol using low levels of positive end-expiratory pressure with open lung approach resulting in moderate to high levels of positive end-expiratory pressure for the management of established moderate/severe acute respiratory distress syndrome. DESIGN: A prospective, multicenter, pilot, randomized controlled trial. SETTING: A network of 20 multidisciplinary ICUs. PATIENTS: Patients meeting the American-European Consensus Conference definition for acute respiratory distress syndrome were considered for the study. INTERVENTIONS: At 12-36 hours after acute respiratory distress syndrome onset, patients were assessed under standardized ventilator settings (FIO2≥0.5, positive end-expiratory pressure ≥10 cm H2O). If Pao2/FIO2 ratio remained less than or equal to 200 mm Hg, patients were randomized to open lung approach or Acute Respiratory Distress Syndrome network protocol. All patients were ventilated with a tidal volume of 4 to 8 ml/kg predicted body weight. MEASUREMENTS AND MAIN RESULTS: From 1,874 screened patients with acute respiratory distress syndrome, 200 were randomized: 99 to open lung approach and 101 to Acute Respiratory Distress Syndrome network protocol. Main outcome measures were 60-day and ICU mortalities, and ventilator-free days. Mortality at day-60 (29% open lung approach vs. 33% Acute Respiratory Distress Syndrome Network protocol, p = 0.18, log rank test), ICU mortality (25% open lung approach vs. 30% Acute Respiratory Distress Syndrome network protocol, p = 0.53 Fisher's exact test), and ventilator-free days (8 [0-20] open lung approach vs. 7 [0-20] d Acute Respiratory Distress Syndrome network protocol, p = 0.53 Wilcoxon rank test) were not significantly different. Airway driving pressure (plateau pressure - positive end-expiratory pressure) and PaO2/FIO2 improved significantly at 24, 48 and 72 hours in patients in open lung approach compared with patients in Acute Respiratory Distress Syndrome network protocol. Barotrauma rate was similar in both groups. CONCLUSIONS: In patients with established acute respiratory distress syndrome, open lung approach improved oxygenation and driving pressure, without detrimental effects on mortality, ventilator-free days, or barotrauma. This pilot study supports the need for a large, multicenter trial using recruitment maneuvers and a decremental positive end-expiratory pressure trial in persistent acute respiratory distress syndrome.

The acute respiratory distress syndrome: incidence and mortality, has it changed?

PURPOSE OF REVIEW: The purpose of this review is to examine and discuss the incidence and outcome of patients with the acute respiratory distress syndrome (ARDS). This is a challenging task, as there is no specific clinical sign or diagnostic test that accurately identifies and adequately defines this syndrome. RECENT FINDINGS: This review will focus on published epidemiological studies reporting population-based incidence of ARDS, as defined by the American-European Consensus Conference criteria. In addition, the current outcome figures for ARDS patients reported in observational and randomized controlled trials will be reviewed. The focus will be on studies published since 2000, when the ARDSnet study on protective mechanical ventilation was published, although particular emphasis will be on those articles published in the last 24 months. SUMMARY: On the basis of current evidence, and despite the order of magnitude of reported European and USA incidence figures, it seems that the incidence and overall mortality of ARDS has not changed substantially since the original ARDSnet study. The current mortality of adult ARDS is still greater than 40%.

EPidemiology, clinical characteristics and Outcomes of 4546 adult admissions to high-dependency and intensive care units in Kenya (EPOK): a multicentre registry-based observational study.

Objective: to describe clinical, management and outcome features of critically ill patients admitted to intensive care units (ICUs) and high dependency units (HDUs) in Kenya. Design: prospective registry-based observational study. Setting: three HDUs and eight ICUs in Kenya. Patients: consecutive adult patients admitted between January 2021 and June 2022. Interventions: none. Measurements and main results: data was entered in a cloud based platform using a common data model. Study endpoints included case mix variables, management features and patient centred outcomes. Patients with Coronavirus disease 2019 (COVID-19) were reported separately. Of the 3892/4546 patients without COVID-19, 2445 patients (62.8%) were from HDUs and 1447 (37.2%) from ICUs. Patients had a median age of 53 years (interquartile range [IQR] 38-68), with HDU patients being older but with a lower severity (APACHE II 6 [3-9] in HDUs vs 12 [7-17] in ICUs; p<0.001). One out of four patients were postoperative with 604 (63.4%) receiving emergency surgery. Readmission rate was 4.8%. Hypertension and diabetes were prevalent comorbidities, with a 4.0% HIV/AIDS rate. Invasive mechanical ventilation (IMV) was applied in 3.4% in HDUs vs. 47.6% in ICUs (P<0.001), with a duration of 7 days (IQR 3-21). There was a similar use of renal replacement therapy (4.0% vs. 4.7%; P<0.001). Vasopressor use was infrequent while half of patients received antibiotics. Average length of stay was 2 days (IQR 1-5). Crude HDU mortality rate was 6.5% in HDUs versus 30.5% in the ICUs (P<0.001). Of the 654 COVID-19 admissions, most were admitted in ICUs (72.3%) with a 33.2% mortality. Conclusions: We provide the first multicenter observational cohort study from an African ICU national registry. Distinct management features and outcomes characterise HDU from ICU patients. Study registration: Clinicaltrials.gov (reference number NCT05456217, date of registration 07 Nov 2022).

Organisation, staffing and resources of critical care units in Kenya.

OBJECTIVE: To describe the organisation, staffing patterns and resources available in critical care units in Kenya. The secondary objective was to explore variations between units in the public and private sectors. MATERIALS AND METHODS: An online cross-sectional survey was used to collect data on organisational characteristics (model of care, type of unit, quality- related activities, use of electronic medical records and participation in the national ICU registry), staffing and available resources for monitoring, ventilation and general critical care. RESULTS: The survey included 60 of 75 identified units (80% response rate), with 43% (n = 23) located in government facilities. A total of 598 critical care beds were reported with a median of 6 beds (interquartile range [IQR] 5-11) per unit, with 26% beds (n = 157) being non functional. The proportion of ICU beds to total hospital beds was 3.8% (IQR 1.9-10.4). Most of the units (80%, n = 48) were mixed/general units with an open model of care (60%, n = 36). Consultants-in-charge were mainly anesthesiologists (69%, n = 37). The nurse-to-bed ratio was predominantly 1:2 with half of the nurses formally trained in critical care. Most units (83%, n = 47) had a dedicated ventilator for each bed, however 63% (n = 39) lacked high flow nasal therapy. While basic multiparametric monitoring was ubiquitous, invasive blood pressure measurement capacity was low (3% of beds, IQR 0-81%), and capnography moderate (31% of beds, IQR 0-77%). Blood gas analysers were widely available (93%, n = 56), with 80% reported as functional. Differences between the public and private sector were narrow. CONCLUSION: This study shows an established critical care network in Kenya, in terms of staffing density, availability of basic monitoring and ventilation resources. The public and private sector are equally represented albeit with modest differences. Potential areas for improvement include training, use of invasive blood pressure and functionality of blood gas analysers.

Performance of current intensive care unit ventilators during pressure and volume ventilation.

BACKGROUND: Intensive-care mechanical ventilators regularly enter the market, but the gas-delivery capabilities of many have never been assessed. METHODS: We evaluated 6 intensive-care ventilators in the pressure support (PS), pressure assist/control (PA/C), and volume assist/control (VA/C) modes, with lung-model mechanics combinations of compliance and resistance of 60 mL/cm H(2)O and 10 cm H(2)O/L/s, 60 mL/cm H(2)O and 5 cm H(2)O/L/s, and 30 mL/cm H(2)O and 10 cm H(2)O/L/s, and inspiratory muscle effort of 5 and 10 cm H(2)O. PS and PA/C were set to 15 cm H(2)O, and PEEP to 5 and 15 cm H(2)O in all modes. During VA/C, tidal volume was set at 500 mL and inspiratory time was set at 0.8 second. Rise time and termination criteria were set at the manufacturers' defaults, and to an optimal level during PS and PA/C. RESULTS: There were marked differences in ventilator performance in all 3 modes. VA/C had the greatest difficulty meeting lung model demand and the greatest variability across all tested scenarios and ventilators. From high to low inspiratory muscle effort, pressure-to-trigger, time for pressure to return to baseline, and triggering pressure-time product decreased in all modes. With increasing resistance and decreasing compliance, tidal volume, pressure-to-trigger, time-to-trigger, time for pressure to return to baseline, time to 90% of peak pressure, and pressure-time product decreased. There were large differences between the default and optimal settings for all the variables in PS and PA/C. Performance was not affected by PEEP. CONCLUSIONS: Most of the tested ventilators performed at an acceptable level during the majority of evaluations, but some ventilators performed inadequately during specific settings. Bedside clinical evaluation is needed.

Adaptive support ventilation: an appropriate mechanical ventilation strategy for acute respiratory distress syndrome?

BACKGROUND: Adaptive support ventilation (ASV) allows the clinician to set a maximum plateau pressure (PP) and automatically adjusts tidal volume to keep PP below the set maximum. METHODS: ASV was compared to a fixed tidal volume of 6 ml/kg. ASV determined the respiratory rate and tidal volume based on its algorithms. Maximum airway pressure limit was 28 cm H2O in ASV. Six sets of lung mechanics were simulated for two ideal body weights: 60 kg, Group I; 80 kg, Group II. Positive end expiratory pressure was 8, 12, and 16 cm H2O, and target minute volume 120%, 150%, and 200% of predicted minute volume. RESULTS: ASV "sacrificed" tidal volume and minute ventilation to maintain PP in 9 (17%) of 54 scenarios in Group I and 20 (37%) of 54 scenarios in Group II. In Group I, the number of scenarios with PP of 28 cm H2O or more was 14 for ASV (26%) and 19 for 6 ml/kg (35%). In these scenarios, mean PP were ASV 28.8 +/- 0.86 cm H2O (min 28, max 30.3) and 6 ml/kg 33.01 +/- 3.48 cm H2O (min 28, max 37.8) (P = 0.000). In group II, the number of scenarios PP of 28 cm H2O or more was 10 for ASV (19%) and 21 for 6 ml/kg (39%). In these cases, mean PP values were ASV 28.78 +/- 0.54 cm H2O (min 28, max 29.6) and 6 ml/kg 32.66 +/- 3.37 cm H2O (min 28.2, max 38.2) (P = 0.000). CONCLUSION: In a lung model with varying mechanics, ASV is better able to prevent the potential damaging effects of excessive PP (greater than 28 cm H2O) than a fixed tidal volume of 6 ml/kg by automatically adjusting airway pressure, resulting in a decreased tidal volume.

Effects of Positive End-Expiratory Pressure on the Risk of Postoperative Pulmonary Complications in Patients Undergoing Elective Craniotomy.

BACKGROUND: Intraoperative use of positive end-expiratory pressure (PEEP) has a protective effect in patients with acute lung injury and is recommended during anesthesia to minimize postoperative pulmonary complications. However, high levels of pressure might also cause harm to the lung because of overdistension. This retrospective study was designed to compare the effect of low and high levels of PEEP on the risk of postoperative pulmonary complications in patients with normal lung function who were undergoing an elective craniotomy. METHODS: Two thousand four hundred thirty-seven patients without any pre-existing respiratory disease, who underwent an elective craniotomy, were hospitalized from January 1, 2008, to December 31, 2012. The patients were divided into 2 groups according to the application of an intraoperative PEEP < 5 or ≥ 5 cm H2O, referred as low and high groups. Primary outcome was the odds of postoperative pneumonia and the requirement for either noninvasive ventilation (NIV) or reintubation and mechanical ventilation (MV). RESULTS: One thousand twenty-three (42%) of 2437 patients were in the low group, and 1414 patients (58%) were in the high group. Patients in the low group did not show any difference in the incidence of postoperative pneumonia (P = 0.523) or the requirement of postoperative reintubation and MV (P = 0.999) compared with those in the high group. The incidence of reintubation and MV is significantly associated with postoperative pneumonia (P < 0.001). CONCLUSIONS: Low and high levels of PEEP show similar incidences of postoperative pneumonia and requirement of postoperative NIV or invasive MV in patients with normal function of the lungs undergoing elective craniotomy.

Perioperative anesthetic management for recipients of orthotopic liver transplant undergoing nontransplant surgery.

OBJECTIVES: The number of organ transplant recipients who present for nontransplant surgery has increased annually. The aim of this study was to evaluate the perioperative anesthetic management of recipients of an orthotopic liver transplant who have undergone nontransplant surgery at Baskent University Hospital. PATIENTS AND METHODS: The medical records of 22 recipients of an orthotopic liver transplant who had undergone a total of 32 nontransplant elective surgeries between December 1988 and February 2006 were retrospectively reviewed. Demographic information, including the anesthetic management and the results of perioperative liver and renal function tests, was recorded. RESULTS: The mean age of the patients at the time of transplant was 20.2 +/- 17.9 years. The mean interval from liver transplant to the first surgery was 739.1 +/- 502.2 days. The most frequent type of surgery was abdominal (28.1%). The types of anesthetic techniques used were general (75%), regional (9.4%), local (9.4%), and sedoanalgesia (6.3%). General anesthesia was induced with thiopental, propofol, or ketamine, and was maintained with isoflurane and nitrous oxide. Endotracheal intubation was performed in 43.8% of the patients. Spinal anesthesia was induced in 3 patients, and peripheral neural blockage was used in 2 patients. Prothrombin time, activated partial thromboplastin time, international normalized ratio, and levels of serum alanine transaminase, aspartate transaminase, total bilirubin, blood urea nitrogen, and creatinine were similar preoperatively and on the first day after surgery (P > .05). CONCLUSIONS: In this study, neither regional nor general anesthesia was associated with a deterioration of liver function. We suggest that recipients of orthotopic liver transplant can undergo nontransplant surgery without postoperative graft dysfunction if hepatic perfusion is maintained with appropriate anesthetic management.

Evaluation of an automated endotracheal tube cuff controller during simulated mechanical ventilation.

BACKGROUND: Maintaining endotracheal tube cuff pressure within a narrow range is an important factor in patient care. The goal of this study was to evaluate the IntelliCuff against the manual technique for maintaining cuff pressure during simulated mechanical ventilation with and without movement. METHODS: The IntelliCuff was compared to the manual technique of a manometer and syringe. Two independent studies were performed during mechanical ventilation: part 1, a 2-h trial incorporating continuous mannikin head movement; and part 2, an 8-h trial using a stationary trachea model. We set cuff pressure to 25 cm H2O, PEEP to 10 cm H2O, and peak inspiratory pressures to 20, 30, and 40 cm H2O. Clinical importance was defined as both statistically significant (P<.05) and clinically significant (pressure change [Δ]>10%). RESULTS: In part 1, the change in cuff pressure from before to after ventilation was clinically important for the manual technique (P<.001, Δ=-39.6%) but not for the IntelliCuff (P=.02, Δ=3.5%). In part 2, the change in cuff pressure from before to after ventilation was clinically important for the manual technique (P=.004, Δ=-14.39%) but not for the IntelliCuff (P=.20, Δ=5.65%). CONCLUSIONS: There was a clinically important drop in manually set cuff pressure during simulated mechanical ventilation in a stationary model and an even larger drop with movement, but this was significantly reduced by the IntelliCuff in both scenarios. Additionally, we observed that cuff pressure varied directly with inspiratory airway pressure for both techniques, leading to elevated average cuff pressures.

A unidirectional breathing pattern improves breathing efficiency in subjects with severe COPD.

BACKGROUND: Unidirectional breathing (UB), nose-in mouth-out (NMB) or vice versa, is thought to create PEEP, stabilize small airways, and increase expiratory flow and exhaled tidal volume (VT) in patients with expiratory obstructive disorders. However, the exact mechanism providing the benefits of UB remains unknown. Our hypothesis was that the benefits of UB are achieved mainly through reduction of upper airway dead space. METHODS: Sixteen stable COPD patients requiring oxygen use at home were enrolled in this prospective study at a tertiary health care center. A nasal mask and a mouthpiece were used, each having a removable one-way valve to direct the breathing pattern. Four experimentally defined patterns of spontaneous breathing, NMB, mouth-in nose-out (MNB), nose-in nose-out (NNB), and mouth-in mouth-out (MMB), were compared. Each breathing pattern lasted 5 min followed by a 5-min rest period. A NICO device continuously monitored respiratory parameters. The functional anatomical dead space volume (VD) and expired VT values were determined. Breathing efficiency (BE) was calculated as alveolar VT divided by expired volume. RESULTS: Functional anatomical VD was higher in bidirectional breathing (BB) (overall: 207.4 ± 7.9 mL; MMB: 232.5 ± 72.7 mL; NNB: 182.2 ± 75 mL) compared to UB (overall: 178.1 ± 87.2 mL; NMB: 176.9 ± 91.3 mL; MNB: 179.3 ± 83.2 mL) (P < .001). BE achieved with UB (overall: 76.2 ± 6.5%; NMB: 76.8 ± 6.8%; MNB: 75.6 ± 6.3%) was higher than that with BB (overall: 66.2 ± 0.09%; MMB: 64.3 ± 0.10%; NNB: 68.1 ± 0.08%) (P < .001). The difference in BE between UB and BB was more pronounced with small VT values (UB: 73.8 ± 0.08; BB: 49.4 ± 0.09) than with large VT values (UB: 77.3 ± 0.06; BB: 63.0 ± 0.07) (P < .001). CONCLUSIONS: Our data suggest that a reduction in functional anatomic VD may be the underlying mechanism for the benefits associated with UB in COPD patients. (ClinicalTrials.gov registration NCT00784004.).

Adaptive support ventilation with and without end-tidal CO2 closed loop control versus conventional ventilation.

PURPOSE: Our aim was to compare adaptive support ventilation with and without closed loop control by end tidal CO2 (ASVCO2, ASV) with pressure (PC) and volume control ventilation (VC) during simulated clinical scenarios [normal lungs (N), COPD, ARDS, brain injury (BI)]. METHODS: A lung model was used to simulate representative compliance (mL/cmH2O): resistance (cmH2O/L/s) combinations, 45:5 for N and BI, 60:7.7 for COPD, 15:7.7 and 35:7.7 for ARDS. Two levels of PEEP (cmH2O) were used for each scenario, 12/16 for ARDS, and 5/10 for others. The CO2 productions of 2, 3, 4 and 5 mL/kg predicted body weight/min were simulated. Tidal volume was set to 6 mL/kg during VC and PC. Outcomes of interest were end tidal CO2 (etCO2) and plateau pressure (P Plat). RESULTS: EtCO2 levels in N and BI and COPD were similar for all modes. In ARDS, etCO2 was higher in ASVCO2 than in other modes (p < 0.001). Under all mechanical conditions ASVCO2 revealed a narrower range of etCO2. P Plat was similar for all modes in all scenarios but ARDS where P Plat in ASV and ASVCO2 were lower than in VC (p = 0.001). When P Plat was ≥ 28 cmH2O, P plat in ASV and ASVCO2 were lower than in VC and PC (p = 0.024). CONCLUSION: All modes performed similarly in most cases. Minor differences observed were in favor of the closed loop modes. Overall, ASVCO2 maintained tighter CO2 control. The ASVCO2 had the greatest impact during ARDS allowing etCO2 to increase and protecting against hypocapnia evident with other modes while ensuring lower P plat and tidal volumes.

New insights into the effect of rapid transfusion of fresh frozen plasma on ionized calcium.

STUDY OBJECTIVES: 1) To develop an in vitro system to simulate the kinetics of ionized calcium in mixed venous blood during rapid transfusion of fresh frozen plasma (FFP) and 2) to use the in vitro data to estimate the effect of the transfusion rate relative to cardiac output (CO) on ionized calcium. DESIGN: Experimental study. SETTING: Research laboratory of an academic hospital. MEASUREMENTS: Citrated FFP was mixed with compatible heparinized whole blood at various volume ratios in vitro to simulate the mixed venous blood obtained at various flow ratios of FFP transfusion to the recipient's venous system in vivo. Ionized calcium was measured after each mixture. MAIN RESULTS: Mixing FFP and whole blood at volume ratios of 0:100, 5:95, 10:90, and 15:85 yielded ionized calcium levels (mean ± SD, mmol/L) of 1.23, 0.81 ± 0.02, 0.54 ± 0.08, and 0.34 ± 0.02, respectively. The 50% reduction in ionized calcium occurred at a volume ratio of 7:93. CONCLUSIONS: An instantaneous 50% reduction in ionized calcium occurs in vitro at a proportion equivalent to a transfusion rate of FFP representing 7% of CO.

Variables affecting leakage past endotracheal tube cuffs: a bench study.

PURPOSE: Leakage of oral secretions past endotracheal tubes (ETT) has been implicated in ventilator associated pneumonia. The aim of this bench study was to compare the ability of current generation ETT cuffs to prevent fluid leakage and to determine the specific mechanical ventilator settings that affect movement of fluid across an inflated ETT cuff. METHODS: Using a 2.3-cm internal diameter (ID) tracheal model and simulated ventilatory support, we evaluated the impact of cuff pressure (20 and 30 cmH(2)O), positive end-expiratory pressure/continuous positive airway pressure (PEEP/CPAP, 0-15 cmH(2)O), peak inspiratory pressure (PIP, 15-45 cmH(2)O), and mode of ventilation (volume control, volume assist/control, pressure control, pressure assist/control, and CPAP) on leakage of fluid past the ETT cuffs of 16 ETTs. The tracheal model was configured in the vertical position with 35 ml of vitaminwater(®) on top of the inflated ETT cuff and mechanically ventilated. Fluid leakage past the cuff was determined by calculating the volume change in the tracheal model after each 30-min ventilation period. Initially five 8.0-mm-ID ETTs of each manufacturer type were evaluated at baseline ventilator settings. Tubes allowing a consistent leak within two SD of the mean leakage for the five tubes were numbered in consecutive order. A single tube from this group was then randomly selected for detailed evaluation. RESULTS: Cuff leakage varied among ETT types (p < 0.0001); median leak volume 6.0 ml (0.6-15.1) across all tubes under all conditions. Cuff leakage was inversely related to PEEP level, cuff pressure, and PIP except when PEEP was set at 15 cmH(2)O (all p < 0.0001). In addition, cuff leak varied among modes (p = 0.035). CONCLUSION: Cuff leakage varies greatly among ETT types and is affected by cuff pressure, PEEP, PIP, and mode.