Is it time to end the use of base deficit for fetal well-being assessment?

Authors have expressed reservations regarding the use of base deficit measured in umbilical artery blood samples to assess fetal well-being during the course of labor and to predict neonatal neurologic morbidity. Despite its integration into clinical practice for more than 50 years, obstetricians and maternal-fetal medicine specialists may not realize that this marker has significant limitations in accurately identifying neonatal metabolic acidosis as a proxy for fetal well-being. In brief, there are 2 large families of base deficit, namely whole blood and extracellular fluid. Both rely on equations that use normal adult acid-base characteristics (pH 7.40 and partial CO2 pressure of 40 mm Hg) that overlook the specificity of the normal in utero acid-base status of pH 7.27 and partial CO2 pressure of 54 mm Hg. In addition, it ignores the unique characteristic of the in utero fetal response to acute hypoxia. The dependence on placental circulation for CO2 elimination may lead to extremely high values (up to 130 to 150 mm Hg) during hypoxic events, a phenomenon that is absent in adults with acute metabolic acidosis who can hyperventilate. The dispute over if to include a correction for high partial CO2 pressure in the bicarbonate estimation, as presented in the Great Trans-Atlantic Debates, remains unresolved. The key constants computed for adult acid-base physiology in the current base deficit algorithms, without accounting for the impact of high partial CO2 pressure or other fetal characteristics of buffering capacity (eg, differences in body water content composition, plasma protein, and hemoglobin attributes), may lead to an overestimation of metabolic acidosis, especially in newborns who are experiencing hypercarbia during the early stages of the hypoxic response. These unrecognized limitations impact the base deficit results and may mislead clinicians on fetal well-being assessments when discussing the management of fetal heart rate monitoring and neonatal outcomes. Based on our arguments, we believe that it is prudent to consider an alternative to base deficit for drawing conclusions regarding fetal well-being during the course of birth management. We propose a marker specifically related to the newborn acid-base physiology--the neonatal eucapnic pH correction. This marker can be added to arterial cord blood gas analysis, and we have described how to interpret it as a marker of neonatal metabolic acidosis.

Umbilical artery eucapnic pH to assess fetal well-being.

BACKGROUND: Umbilical artery gas results help obstetricians assess fetal well-being during labor and guide screening decisions on eligibility for therapeutic hypothermia (ie, whole-body or head cooling). The accuracy of results, especially for the base deficit on arterial cord gas analysis, in predicting brain injury is questioned. A novel biomarker specifically calculated for fetal acid-base physiology and response to asphyxia-neonatal eucapnic pH as a marker of neonatal metabolic acidosis-has the potential to be an accurate predictor of hypoxic-ischemic encephalopathy. OBJECTIVE: We aimed to compare false-negative rates of hypoxic-ischemic encephalopathy for umbilical artery pH, base deficit, and neonatal eucapnic pH in assessing fetal acid-base balance as a marker of fetal well-being and predicting acute brain injury. STUDY DESIGN: This is a retrospective single-center cohort study of newborns ≥ 35 weeks of gestation diagnosed with hypoxic-ischemic encephalopathy. We compared false-negative rates for any grade of hypoxic-ischemic encephalopathy using unilateral paired chi-square statistical analysis based on cutoff values for umbilical artery pH ≤7.00, base deficit ≥16 mmol/L, base deficit ≥12 mmol/L and neonatal eucapnic pH ≤7.14. We performed an analysis of variance between umbilical artery pH, base deficit, and neonatal eucapnic pH for each hypoxic-ischemic encephalopathy grade. RESULTS: We included 113 newborns. False-negative rate for hypoxic-ischemic encephalopathy was significantly higher for base deficit <16 mmol/L (n=78/113; 69.0%) than <12 mmol/L (n=46/113; 40.7%), pH >7.00 (n=41/113; 36.3%), or neonatal eucpanic pH >7.14 (n=35/113; 31.0%) (P<.0001). All true-positive cases were identified using only umbilical artery pH and neonatal eucapnic pH. Base deficit ≥16 or ≥12 mmol/L did not add any value in identifying newborns with hypoxic-ischemic encephalopathy when using umbilical artery pH and neonatal eucapnic pH. No association emerged between any marker and hypoxic-ischemic encephalopathy severity grading. CONCLUSION: Our findings support the accuracy of neonatal eucapnic pH to assess fetal well-being during labor and to improve predictive performance for acute brain injury. Neonatal eucpanic pH, in addition to umbilical artery pH, may be a viable alternative in identifying newborns at risk for hypoxic-ischemic encephalopathy.

A novel capnogram analysis to guide ventilation during cardiopulmonary resuscitation: clinical and experimental observations.

BACKGROUND: Cardiopulmonary resuscitation (CPR) decreases lung volume below the functional residual capacity and can generate intrathoracic airway closure. Conversely, large insufflations can induce thoracic distension and jeopardize circulation. The capnogram (CO2 signal) obtained during continuous chest compressions can reflect intrathoracic airway closure, and we hypothesized here that it can also indicate thoracic distension. OBJECTIVES: To test whether a specific capnogram may identify thoracic distension during CPR and to assess the impact of thoracic distension on gas exchange and hemodynamics. METHODS: (1) In out-of-hospital cardiac arrest patients, we identified on capnograms three patterns: intrathoracic airway closure, thoracic distension or regular pattern. An algorithm was designed to identify them automatically. (2) To link CO2 patterns with ventilation, we conducted three experiments: (i) reproducing the CO2 patterns in human cadavers, (ii) assessing the influence of tidal volume and respiratory mechanics on thoracic distension using a mechanical lung model and (iii) exploring the impact of thoracic distension patterns on different circulation parameters during CPR on a pig model. MEASUREMENTS AND MAIN RESULTS: (1) Clinical data: 202 capnograms were collected. Intrathoracic airway closure was present in 35%, thoracic distension in 22% and regular pattern in 43%. (2) Experiments: (i) Higher insufflated volumes reproduced thoracic distension CO2 patterns in 5 cadavers. (ii) In the mechanical lung model, thoracic distension patterns were associated with higher volumes and longer time constants. (iii) In six pigs during CPR with various tidal volumes, a CO2 pattern of thoracic distension, but not tidal volume per se, was associated with a significant decrease in blood pressure and cerebral perfusion. CONCLUSIONS: During CPR, capnograms reflecting intrathoracic airway closure, thoracic distension or regular pattern can be identified. In the animal experiment, a thoracic distension pattern on the capnogram is associated with a negative impact of ventilation on blood pressure and cerebral perfusion during CPR, not predicted by tidal volume per se.

Intrathoracic Airway Closure Impacts CO2 Signal and Delivered Ventilation during Cardiopulmonary Resuscitation.

RATIONALE: End-tidal CO2 (EtCO2) is used to monitor cardiopulmonary resuscitation (CPR), but it can be affected by intrathoracic airway closure. Chest compressions induce oscillations in expired CO2, and this could reflect variable degrees of airway patency. OBJECTIVES: To understand the impact of airway closure during CPR, and the relationship between the capnogram shape, airway closure, and delivered ventilation. METHODS: This study had three parts: 1) a clinical study analyzing capnograms after intubation in patients with out-of-hospital cardiac arrest receiving continuous chest compressions, 2) a bench model, and 3) experiments with human cadavers. For 2 and 3, a constant CO2 flow was added in the lung to simulate CO2 production. Capnograms similar to clinical recordings were obtained and different ventilator settings tested. EtCO2 was compared with alveolar CO2 (bench). An airway opening index was used to quantify chest compression-induced expired CO2 oscillations in all three clinical and experimental settings. MEASUREMENTS AND MAIN RESULTS: A total of 89 patients were analyzed (mean age, 69 ± 15 yr; 23% female; 12% of hospital admission survival): capnograms exhibited various degrees of oscillations, quantified by the opening index. CO2 value varied considerably across oscillations related to consecutive chest compressions. In bench and cadavers, similar capnograms were reproduced with different degrees of airway closure. Differences in airway patency were associated with huge changes in delivered ventilation. The opening index and delivered ventilation increased with positive end-expiratory pressure, without affecting intrathoracic pressure. Maximal EtCO2 recorded between ventilator breaths reflected alveolar CO2 (bench). CONCLUSIONS: During chest compressions, intrathoracic airway patency greatly affects the delivered ventilation. The expired CO2 signal can reflect CPR effectiveness but is also dependent on airway patency. The maximal EtCO2 recorded between consecutive ventilator breaths best reflects alveolar CO2.

A proposed lung ultrasound and phenotypic algorithm for the care of COVID-19 patients with acute respiratory failure.

Pulmonary complications are the most common clinical manifestations of coronavirus disease (COVID-19). From recent clinical observation, two phenotypes have emerged: a low elastance or L-type and a high elastance or H-type. Clinical presentation, pathophysiology, pulmonary mechanics, radiological and ultrasound findings of these two phenotypes are different. Consequently, the therapeutic approach also varies between the two. We propose a management algorithm that combines the respiratory rate and oxygenation index with bedside lung ultrasound examination and monitoring that could help determine earlier the requirement for intubation and other surveillance of COVID-19 patients with respiratory failure.

RéSUMé: Les complications pulmonaires du coronavirus (COVID-19) constituent ses manifestations cliniques les plus fréquentes. De récentes observations cliniques ont fait émerger deux phénotypes : le phénotype à élastance faible ou type L (low), et le phénotype à élastance élevée, ou type H (high). La présentation clinique, la physiopathologie, les mécanismes pulmonaires, ainsi que les observations radiologiques et échographiques de ces deux différents phénotypes sont différents. L'approche thérapeutique variera par conséquent selon le phénotype des patients atteints de COVID-19 souffrant d'insuffisance respiratoire.

Umbilical artery carbon dioxide decreases the risk for hypoxic-ischaemic encephalopathy.

AIM: An accurate biomarker for metabolic acidosis at birth is needed. Our aims were to investigate the link between umbilical artery pCO2 and the risk for hypoxic-ischaemic encephalopathy (HIE) and to compare false-negative screen results in newborn infants with HIE using three umbilical artery blood gas biomarkers. METHODS: From a cohort of newborn infants ≥35 weeks born in Ottawa, Canada, between January 2007 and December 2016, we highlighted those with HIE or who died. We compared the umbilical artery pCO2 for matched pH >mean versus matched pH ≤mean. We compared false-negative rates for three umbilical artery biomarkers-pH <7.0, base deficit ≥16 mmol/L and neonatal eucapnic pH ≤7.14. RESULTS: This study included 51 286 newborn infants, 51% male and a mean gestational age of 38.9 ± 1.5 weeks. The rate for HIE or death with umbilical artery pCO2 for matched pH >mean was 22%, compared to 78% for matched pH ≤mean. In 60 HIE or deaths, the false-negative rate for umbilical artery neonatal eucapnic pH ≤7.14 was 8%; compared to 31% for pH <7.00 and 36% for base deficit ≥16 mmol/L. CONCLUSION: The rate of HIE or death is lower in newborn infants with higher pCO2 . Using neonatal eucapnic pH decreases the risk of missing newborn infants with HIE.

Eucapnic pH coupled with arterial cord pH improves hypoxic-ischemic encephalopathy prediction.

OBJECTIVE: To consider the classical use of "pH < 7.0 and/or a base deficiency ≥12 mmol/L" as markers of the risk of neonatal hypoxic-ischemic encephalopathy (HIE), recalling various criticisms of the use of these markers in favor of that of neonatal eucapnic pH, which appears to be a better marker of this risk. METHODS: Fifty-five cases of acidemia with pH < 7.00 were collected from a cohort from the Nice University Hospital with eight cases of HIE. We compared the receiver operating characteristics curves established from the positive likelihood ratio (+LR) for each case of: umbilical cord artery pH (pHa), neonatal eucapnic pH (pH euc-n) in isolation (not matched to pHa), and matched pHa to its own pH euc-n. RESULTS: The areas under the curve (AUC) are identical for pHa and pH euc-n, but AUC for the matched pair pHa-pH euc-n appears superior but non-significant because of the small number in our cohort. However, using the bootstrap method, the partial AUC for a sensitivity greater than 75% indicates the significant superiority (P < 0.01) of the matched pair pHa-pH euc-n approach. CONCLUSION: The originality of this study lies in the use of two methodologic approaches: (1) standardized partial analysis of the AUCs of the pHa curve and that of pHa matched to its own pH euc-n, and (2) bootstrap statistical technique, that allowed us to conclude (P < 0.01) that the combined use of pH measured at the cord coupled with its eucapnic correction is better for diagnosing metabolic acidosis and best predicting the risk of HIE.

Preliminary evaluation of a new index to predict the outcome of a spontaneous breathing trial.

BACKGROUND: The available predictors of spontaneous-breathing-trial (SBT) success/failure lack accuracy. We devised a new index, the CORE index (compliance, oxygenation, respiration, and effort). OBJECTIVE: To compare the CORE index to the CROP index (compliance, rate, oxygenation, and pressure), airway-occlusion pressure 0.1 s after the start of inspiratory flow (P(0.1)), and rapid shallow breathing index (RSBI) for predicting SBT success/failure in a critical care environment. METHODS: With 47 mechanically ventilated patients recovering from respiratory failure, of various causes, we prospectively examined the SBT success/failure prediction accuracy and calculated receiver operating characteristic curves, sensitivity, specificity, and likelihood ratios of CORE, CROP, P(0.1), and RSBI. RESULTS: The specificities were CORE 0.95, P(0.1) 0.70, CROP 0.70, and RSBI 0.65. The sensitivities were CORE 1.00, CROP 1.00, P(0.1) 0.93, and RSBI 0.89. The areas under the receiver operating characteristic curve were CORE 1.00 (95% CI 0.92-1.00), CROP 0.91 (95% CI 0.79-0.97), P(0.1) 0.81 (95% CI 0.67-0.91), and RSBI 0.77 (95% CI 0.62-0.88). The positive likelihood ratios were CORE 20.0, CROP 3.3, P(0.1) 3.1, and RSBI 2.5. The negative likelihood ratios were CORE 0.0, CROP 0.0, P(0.1) 0.1, and RSBI 0.2. CONCLUSIONS: The CORE index was the most accurate predictor of SBT success/failure.

Umbilical artery base deficit/excess: sailing blindly in a thick fog.

Assessing the wellbeing of newborns at birth with base deficit (BD)/base excess(BE) is well anchored in clinicians' practice. However, clinicians may not fully understand the concepts behind BD and the concerns regarding the validity of BD results provided by the hospital laboratory. These concerns are linked to the inconsistencies between the equations to calculate BD, and that these equations do not consider the aspects of acid-base physiology at birth. Additionally, the evidence-based supporting BD threshold in the literature to help physicians in making decisions is rather insufficient. These considerations support the need to review practice guidelines that use BD to guide decisions and bring to an end to clinicians to sail blindly in a thick fog.

Comparisons between umbilical cord biomarkers for newborn hypoxic-ischemic encephalopathy.

BACKGROUND: Cord blood umbilical artery (Ua) pH, base deficit (BD), and pH eucapnic Blickstein/Green-50 may mislead clinicians to identify newborns at risk for hypoxic-ischemic encephalopathy. Neonatal eucapnic pH (pH euc-n Racinet-54) may be a comprehensive alternative. The goal of the study is to compare the predictive performance of these four biomarkers for the combined primary outcome of hypoxic-ischemic encephalopathy/death. METHODS: This retrospective cohort study includes newborns ≥35 weeks gestational age. Receiver operating characteristics curves analysis was performed for Ua cord pH, BD, pH euc-n Racinet-54, and pH eucapnic Blickstein/Green-50 for the global cohort and for two subgroups of newborns with Ua cord pH ≤ 7.15. Cutoff values were derived for all four markers. RESULTS: From the original cohort of 61,037 newborns born between 1 January 2007 and 31 December 2016, we excluded cases with major congenital malformations and missing/incomplete data. The global cohort includes 51,286 newborns and 60 newborns afflicted with hypoxic-ischemic encephalopathy (HIE)/death. The area under the curves (AUC) derived from the global cohort were comparable between Ua cord pH (0.95; 95%CI = 0.94-0.95), BD (0.93; 95%CI = 0.93-0.93), pH euc-n Racinet-54 (0.93; 95% CI = 0.93-0.93), and lower for pH Blickstein/Green-50 (0.78; 95% CI = 0.77-0.78) (p < .05). Within newborn with severe acidemia (pH ≤ 7.00) and moderate acidemia (7.00 ≤ pH ≤ 7.15), pH euc-n Racinet-54 had the largest AUC and best positive likelihood ratios especially for sensitivity ≥ 0.80 to minimize false negative cases. CONCLUSION: In this large retrospective study, predictive performance for Ua cord pH, BD, and pH euc-n Racinet-54 are comparable when applied to the global group. For newborns with Ua cord pH ≤ 7.00 and Ua cord 7.00 ≤ pH ≤ 7.15, pH euc-n Racinet-54 appears better to identify those with HIE/death, especially when the target is sensitivity > 80%. Prospective studies will confirm if pH euc-n Racinet-54 is a better alternative to Ua cord pH and BD to evaluate newborn acid-base physiology.

Gastric insufflation during cardiopulmonary resuscitation: A study in human cadavers.

INTRODUCTION: Bag-valve-mask ventilation is the first-line ventilation method during cardiopulmonary resuscitation (CPR). Risks include excessive volume delivery and gastric insufflation, the latter increasing the risk of pneumonia. The efficacy of ventilation can also be reduced by airway closure. We hypothesized that continuous chest compression (CC) could limit the risk of gastric insufflation compared to the recommended 30:2 interrupted CC strategy. This experimental study was performed in human "Thiel" cadavers to assess the respective impact of discontinuous vs. continuous chest compressions on gastric insufflation and ventilation during CPR. METHODS: The 30:2 interrupted CC technique was compared to continuous CC in 5 non-intubated cadavers over a 6 min-period. Flow and Airway Pressure were measured at the mask. A percutaneous gastrostomy allowed measuring the cumulative gastric insufflated volume. Two additional cadavers were equipped with esophageal and gastric catheters instead of the gastrostomy. RESULTS: For the 7 cadavers studied (4 women) median age of death was 79 [74-84] years. After 6 min of CPR, the cumulative gastric insufflation measured in 5 cadavers was markedly reduced during continuous CC compared to the interrupted CC strategy: (1.0 [0.8-4.1] vs. 5.9 [4.0-5.6] L; p < 0.05) while expired minute ventilation was slightly higher during continuous than interrupted CC (1.9 [1.4-2.8] vs. 1.6 [1.1-2.7] L/min; P < 0.05). In 2 additional cadavers, the progressive rise in baseline gastric pressure was lower during continuous CC than interrupted CC (1 and 2 cmH2O vs. 12 and 5.8 cmH2O). CONCLUSION: Continuous CC significantly reduces the volume of gas insufflated in the stomach compared to the recommended 30:2 interrupted CC strategy. Ventilation actually delivered to the lung is also slightly increased by the strategy.

Translaryngeal Tracheostomy Needle Introducer: a simple device to improve safety and reduce complications during Fantoni's translaryngeal tracheostomy procedure: trial on human cadavers.

BACKGROUND: Percutaneous dilatational tracheostomy (PDT) is the most frequently performed procedure in patients requiring prolonged mechanical ventilation. A crucial step in such procedures is needle insertion into the trachea. To simplify this procedure and increase its safety, we developed a new device, the translaryngeal Tracheostomy Needle Introducer (tTNI), for use with Fantoni's method. This cadaver study was designed to assess the performance of the tTNI on human anatomy. METHODS: We tested the tTNI in a cadaver laboratory; the operators included two experts trained in PDT and three without specific training in the procedure. We performed 58 needle insertion attempts on 13 cadavers. We compared the tTNI technique with the standard needle insertion approach using external landmarks. We recorded the number of attempts needed to optimise needle insertion, time required in seconds, final position of the needle and complications related to needle insertion. RESULTS: tTNI use resulted in fewer puncture attempts (1.91 ± 1.34 vs. 1.19 ± 0.5, p < 0.001), less time (36.8 ± 51.6 s vs. 13.14 ± 15.57 s, p < 0,001) and increased precision on the first puncture (18.87 ± 25.38° vs. 7.5 ± 12.95°, p < 0,005). We did not observe any complication with tTNI use, whereas complications found using the standard method were in line with the literature. CONCLUSIONS: The tTNI is a device that simplifies needle insertion by enhancing the accuracy of insertion with fewer attempts and higher precision, even when used by less experienced operators. Clinical testing is required to evaluate the device performance in patients.

A new physiological model for studying the effect of chest compression and ventilation during cardiopulmonary resuscitation: The Thiel cadaver.

BACKGROUND: Studying ventilation and intrathoracic pressure (ITP) induced by chest compressions (CC) during Cardio Pulmonary Resuscitation is challenging and important aspects such as airway closure have been mostly ignored. We hypothesized that Thiel Embalmed Cadavers could constitute an appropriate model. METHODS: We assessed respiratory mechanics and ITP during CC in 11 cadavers, and we compared it to measurements obtained in 9 out-of-hospital cardiac arrest patients and to predicted values from a bench model. An oesophageal catheter was inserted to assess chest wall compliance, and ITP variation (ΔITP). Airway pressure variation (ΔPaw) at airway opening and ΔITP generated by CC were measured at decremental positive end expiratory pressure (PEEP) to test its impact on flow and ΔPaw. The patient's data were derived from flow and airway pressure captured via the ventilator during resuscitation. RESULTS: Resistance and Compliance of the respiratory system were comparable to those of the out-of-hospital cardiac arrest patients (CRSTEC 42 ±â€¯12 vs CRSPAT 37.3 ±â€¯10.9 mL/cmH2O and ResTEC 17.5 ±â€¯7.5 vs ResPAT 20.2 ±â€¯5.3 cmH2O/L/sec), and remained stable over time. During CC, ΔITP varied from 32 ±â€¯12 cmH2O to 69 ±â€¯14 cmH2O with manual and automatic CC respectively. Transmission of ΔITP at the airway opening was significantly affected by PEEP, suggesting dynamic small airway closure at low lung volumes. This phenomenon was similarly observed in patients. CONCLUSION: Respiratory mechanics and dynamic pressures during CC of cadavers behave as predicted by a theoretical model and similarly to patients. The Thiel model is a suitable to assess ITP variations induced by ventilation during CC.

The use of the bispectral index in the detection of pain in mechanically ventilated adults in the intensive care unit: a review of the literature.

BACKGROUND: Pain assessment is an immense challenge for clinicians, especially in the context of the intensive care unit, where the patient is often unable to communicate verbally. Several methods of pain assessment have been proposed to assess pain in this environment. These include both behavioural observation scales and evaluation of physiological measurements such as heart rate and blood pressure. Although numerous validation studies pertaining to behavioural observation scales have been published, several limitations associated with using these measures for pain assessment remain. Over the past few years, researchers have been interested in the use of the bispectral index monitoring system as a proxy for the evaluation of encephalography readings to assess the level of anesthesia and, potentially, analgesia. OBJECTIVES: To synthesize the main studies exploring the use of the bispectral index monitoring system for pain assessment, to guide future research in adults under sedation in the intensive care unit. METHOD: The EMBASE, Medline, CINAHL and PsycINFO databases were searched for studies published between 1996 and 2013 that evaluated the use of the bispectral index in assessing pain. RESULTS: Most studies conclude that nociceptive stimulation causes a significant increase in the bispectral index and revealed the importance of controlling certain confounding variables such as the level of sedation. DISCUSSION: Further studies are needed to clearly demonstrate the relationship between nociceptive stimuli and the bispectral index, as well as the specificity of the bispectral index in detecting pain.

Effect of ventilatory variability on occurrence of central apneas.

OBJECTIVE: To compare the influence of 2 ventilation strategies on the occurrence of central apneas. METHODS: This was a prospective, comparative, crossover study with 14 unsedated subjects undergoing weaning from mechanical ventilation in the medical ICU of Hôpital du Sacré-Cœur, Montréal, Québec, Canada. The subjects were ventilated alternately in neurally adjusted ventilatory assist (NAVA) and pressure support ventilation (PSV) modes. Inspiratory flow/time and pressure/time waveforms and diaphragmatic electrical activity were used to detect central apneas. Ventilatory variability and breathing pattern were evaluated in both modes. Breathing patterns just before central apneas, and associations between apneas and sleep patterns (electroencephalogram) were studied. RESULTS: Switching from PSV to NAVA did not change mean minute ventilation, tidal volume, or breathing frequency. However, tidal volume variability, defined as the coefficient of variability (standard error/mean), was significantly greater with NAVA than with PSV (17.2 ± 8 vs 10.3 ± 4, P = .045). NAVA induced a greater decrease in central apneas, compared to PSV (to 0 with NAVA vs 10.5 ± 11 with PSV, P = .005). Central apneas during PSV were detected only during non-rapid-eye-movement sleep. CONCLUSIONS: NAVA was associated with increased ventilatory variability, compared to constant-level PSV. With NAVA the absence of over-assistance during sleep coincided with absence of central apneas, suggesting that load capacity and/or neuromechanical coupling were improved by NAVA and that this improvement decreased or abolished central apneas.

Sleep quality in mechanically ventilated patients: comparison between NAVA and PSV modes.

BACKGROUND: Mechanical ventilation seems to occupy a major source in alteration in the quality and quantity of sleep among patients in intensive care. Quality of sleep is negatively affected with frequent patient-ventilator asynchronies and more specifically with modes of ventilation. The quality of sleep among ventilated patients seems to be related in part to the alteration between the capacities of the ventilator to meet patient demand. The objective of this study was to compare the impact of two modes of ventilation and patient-ventilator interaction on sleep architecture. METHODS: Prospective, comparative crossover study in 14 conscious, nonsedated, mechanically ventilated adults, during weaning in a university hospital medical intensive care unit. Patients were successively ventilated in a random ordered cross-over sequence with neurally adjusted ventilatory assist (NAVA) and pressure support ventilation (PSV). Sleep polysomnography was performed during four 4-hour periods, two with each mode in random order. RESULTS: The tracings of the flow, airway pressure, and electrical activity of the diaphragm were used to diagnose central apneas and ineffective efforts. The main abnormalities were a low percentage of rapid eye movement (REM) sleep, for a median (25th-75th percentiles) of 11.5% (range, 8-20%) of total sleep, and a highly fragmented sleep with 25 arousals and awakenings per hour of sleep. Proportions of REM sleep duration were different in the two ventilatory modes (4.5% (range, 3-11%) in PSV and 16.5% (range, 13-29%) during NAVA (p = 0.001)), as well as the fragmentation index, with 40 ± 20 arousals and awakenings per hour in PSV and 16 ± 9 during NAVA (p = 0.001). There were large differences in ineffective efforts (24 ± 23 per hour of sleep in PSV, and 0 during NAVA) and episodes of central apnea (10.5 ± 11 in PSV vs. 0 during NAVA). Minute ventilation was similar in both modes. CONCLUSIONS: NAVA improves the quality of sleep over PSV in terms of REM sleep, fragmentation index, and ineffective efforts in a nonsedated adult population.

Poor correlation between hemodynamic and echocardiographic indexes of left ventricular performance in the operating room and intensive care unit.

OBJECTIVES: To compare hemodynamic and echocardiographic indexes of left ventricular performance. DESIGN: Retrospective database analysis of four clinical trials. SETTING: University hospital. PATIENTS: Cardiac surgery patients. INTERVENTION: Left ventricular performance was evaluated using left ventricular stroke work index (LVSWI) calculated from the pulmonary artery catheter and both fractional area change and regional wall motion score index (RWMSI) measured from transesophageal echocardiography. Measures of left ventricular performance were obtained before and after bypass (group 1, n = 30), during acute increase and decrease in preload (group 2, n = 14), after administration of inhaled prostacyclin or placebo in patients with pulmonary hypertension (group 3, n = 20), and in hemodynamically unstable patients in the intensive care unit at admission and at 2 and 4 hrs (group 4, n = 20). MAIN RESULTS: A total of 186 simultaneous LVSWI, fractional area change, and RWMSI were analyzed and compared. Patients with RWMSI <1.3 had a LVSWI of 23.4 +/- 10.3 g.m.m compared with 18.4 +/- 7.2 g.m.m in those with RWMSI >1.3 (p =.0349). Subdividing fractional area change into three different groups (> or =50%, 25% to 49%, and < or =24%), the corresponding values of LVSWI were 22.3 +/- 9.7 g.m.m, 22.2 +/- 10.8 g.m.m, and 17.7 +/- 5.5 g.m.m, respectively (p =.5114). Correlations between LVSWI and RWMSI changes ranged from -0.28 to 0.16 (p values from.31 to.94). Correlations between LVSWI and fractional area change changes ranged from -0.62 to 0.22 (p values from.07 to.95). CONCLUSION: There is a significant discrepancy and limited relationship between the hemodynamic and echocardiographic evaluation of left ventricular performance.