IntroductionWe hypothesized the expiratory time constant (ƬE) may be used to provide real time determinations of inspiratory plateau pressure (Pplt), respiratory system compliance (Crs), and total resistance (respiratory system resistance plus series resistance of endotracheal tube) (Rtot) of patients with respiratory failure using various modes of ventilatory support.MethodsAdults (n = 92) with acute respiratory failure were categorized into four groups depending on the mode of ventilatory support ordered by attending physicians, i.e., volume controlled-continuous mandatory ventilation (VC-CMV), volume controlled-synchronized intermittent mandatory ventilation (VC-SIMV), volume control plus (VC+), and pressure support ventilation (PSV). Positive end expiratory pressure as ordered was combined with all aforementioned modes. Pplt, determined by the traditional end inspiratory pause (EIP) method, was combined in equations to determine Crs and Rtot. Following that, the ƬE method was employed, ƬE was estimated from point-by-point measurements of exhaled tidal volume and flow rate, it was then combined in equations to determine Pplt, Crs, and Rtot. Both methods were compared using regression analysis.ResultsƬE, ranging from mean values of 0.54 sec to 0.66 sec, was not significantly different among ventilatory modes. The ƬE method was an excellent predictor of Pplt, Crs, and Rtot for various ventilatory modes; r2 values for the relationships of ƬE and EIP methods ranged from 0.94 to 0.99 for Pplt, 0.90 to 0.99 for Crs, and 0.88 to 0.94 for Rtot (P <0.001). Bias and precision values were negligible.ConclusionsWe found the ƬE method was just as good as the EIP method for determining Pplt, Crs, and Rtot for various modes of ventilatory support for patients with acute respiratory failure. It is unclear if the ƬE method can be generalized to patients with chronic obstructive lung disease. ƬE is determined during passive deflation of the lungs without the need for changing the ventilatory mode and disrupting a patient's breathing. The ƬE method obviates the need to apply an EIP, allows for continuous and automatic surveillance of inspiratory Pplt so it can be maintained ≤ 30 cm H2O for lung protection and patient safety, and permits real time assessments of pulmonary mechanics.

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Introduction: Rotator cuff repair (RCR) is commonly performed before reverse shoulder arthroplasty (RSA) with conflicting evidence on the effect on arthroplasty outcomes. The purpose of this investigation was to evaluate the effect of a prior RCR on the outcomes and complications of primary RSA. Methods: Between 2007 and 2017, 438 RSAs performed in patients with a prior RCR and 876 case-matched controls were identified from a multicenter database. Patients were grouped based on a preoperative diagnosis of glenohumeral osteoarthritis (GHOA) and rotator cuff tear arthropathy (CTA). Data collected included range of motion, strength, complications, and revisions. Additional clinical metrics included American Shoulder and Elbow Society score, Constant score, Shoulder Pain and Disability Index, Simple Shoulder Test, and the University of California Los Angeles shoulder score. Results: Compared with controls, both GHOA and CTA study groups demonstrated lower postoperative forward elevation (FE) (133°versus 147°, P , 0.001; 133°versus 139°, P = 0.048) and FE trength (6.5 versus 8.2, P = 0.004; 6.1 versus 7.3, P = 0.014). In addition, inferior improvements were observed in the GHOA and CTA study groups with respect to abduction (38°versus 52°, P = 0.001; 36°versus 49°, P = 0.001), FE (41°versus 60°, P , 0.001; 38°versus 52°, P = 0.001), ER (16°versus 25°, P , 0.001; 10°versus 17°, P = 0.001), and Constant score (28.4 versus 37.1, P , 0.001; 26.2 versus 30.9, P = 0.016). Compared with controls, no differences were observed in the GHOA and CTA study groups with respect to notching (11.2% versus 5.6%, P = 0.115; 5.8% versus 7.9%, P = 0.967), complications (4.3% versus 1.6%, P = 0.073; 2.5% versus 2.7%, P = 0.878), and revision surgery (3.1% versus 0.9%, P = 0.089; 1.1% versus 1.3%, P = 0.822). Conclusion: RSA after a prior RCR improves both pain and function, without increasing scapular notching, complications, or revision surgery. However, compared with patients without a prior RCR, postoperative shoulder function may be slightly decreased.

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Study Design: Historically controlled clinical trial. Objectives: Patients presenting for correction of adolescent idiopathic scoliosis (AIS) by posterior spinal fusion may benefit from structured clinical pathways. We studied the effects of implementing a published clinical pathway for the perioperative care of patients with AIS that required intraoperative use of methadone at our institution. Methods: We performed a historically controlled clinical trial of patients undergoing posterior spinal fusion for AIS by comparing a retrospectively collected control group of 25 patients with a prospective experimental group of 14 patients receiving methadone, gabapentin, propofol, and remifentanil as part of a new clinical pathway. Results: Use of the pathway decreased average pain scores evaluated by the Numeric Rating Scale in the 24 hours following surgery (4.8 [4-6] to 3.4 [2-4], P = .03 [−2.6 to −0.2; t = −2.3]) and postoperative opioid consumption by 76% (41 [29-51] mg to 10 [4-17] mg, P < .001 [−45 to −15; Welch’s t = 4.9]) during the same period. Improved analgesia and reduced reliance on opioids facilitated other postoperative elements of the clinical pathway and shortened the average hospital length of stay by 1 day (4 [3-6] days to 3 [3-5] days, P = .001 [−2 to −1; U = 67, Z = −3.3]). Conclusions: Multimodal analgesia and a clinical pathway add value in the perioperative care of patients undergoing posterior spinal fusion for AIS by improving analgesia and shortening hospitalization. The prospective arm of the trial was registered at clinicaltrials.gov under NCT02481570.

We describe a real time, noninvasive method of estimating work of breathing (esophageal balloon not required) during noninvasive pressure support (PS) that uses an artificial neural network (ANN) combined with a leak correction (LC) algorithm, programmed to ignore asynchronous breaths, that corrects for differences in inhaled and exhaled tidal volume (VT) from facemask leaks (WOBANN,LC/min). Validation studies of WOBANN,LC/min were performed. Using a dedicated and popular noninvasive ventilation ventilator (V60, Philips), in vitro studies using PS (5 and 10 cm H2O) at various inspiratory flow rate demands were simulated with a lung model. WOBANN,LC/min was compared with the actual work of breathing, determined under conditions of no facemask leaks and estimated using an ANN (WOBANN/min). Using the same ventilator, an in vivo study of healthy adults (n = 8) receiving combinations of PS (3-10 cm H2O) and expiratory positive airway pressure was done. WOBANN,LC/min was compared with physiologic work of breathing/min (WOBPHYS/min), determined from changes in esophageal pressure and VT applied to a Campbell diagram. For the in vitro studies, WOBANN,LC/min and WOBANN/min ranged from 2.4 to 11.9 J/min and there was an excellent relationship between WOBANN,LC/breath and WOBANN/breath, r = 0.99, r(2) = 0.98 (p < 0.01). There were essentially no differences between WOBANN,LC/min and WOBANN/min. For the in vivo study, WOBANN,LC/min and WOBPHYS/min ranged from 3 to 12 J/min and there was an excellent relationship between WOBANN,LC/breath and WOBPHYS/breath, r = 0.93, r(2) = 0.86 (p < 0.01). An ANN combined with a facemask LC algorithm provides noninvasive and valid estimates of work of breathing during noninvasive PS. WOBANN,LC/min, automatically and continuously estimated, may be useful for assessing inspiratory muscle loads and guiding noninvasive PS settings as in a decision support system to appropriately unload inspiratory muscles.

A second aim was to characterize the magnitude of dose changes (bolus, infusion rates, or both) necessary to detect differences in the duration of selected anesthetic effects following emergence from anesthesia. We hypothesized that within a range of clinically relevant doses, dosing intervals exist for propofol, remifentanil, and fentanyl that are distinguishable from one another.