Tracheal Pressure Research Articles

Changes in Tracheal Tube Cuff Pressure and Recurrent Laryngeal Nerve Conductivity During Thyroid Surgery.

The aetiology of recurrent laryngeal nerve (RLN) neurapraxia is unclear in most RLN palsies post-thyroidectomy. We hypothesised that high intralaryngeal pressures impede RLN conductivity, in turn contributing to RLN palsy. Therefore, we measured tracheal tube (TT) cuff pressure (as a surrogate for intralaryngeal pressure) and RLN conduction during ten standard manoeuvres in thyroidectomy, to assess for correlation between cuff pressure and RLN conductivity. A prospective cohort study of thyroidectomy during 2018. For each thyroid lobe, TT cuff pressure was continuously measured via an air pressure transducer. RLN conduction (amplitude and latency) was measured using continuous neuromonitoring. Changes in mean TT cuff pressure and median nerve conduction from baseline measurements were analysed using Student's t test and Wilcoxon signed-rank test. In a total of 50 RLNs, the mean baseline TT cuff pressure of 19.5 ± 8.9mmHg increased significantly to 22.0mmHg during anteromedial rotation of the thyroid (p < 0.05). RLN conduction changed during manipulation of the superior thyroid pole with shortening of latency (-0.49% from baseline, p = 0.05) and reduction in amplitude (-12.0% from baseline, p = 0.02). The timing of these deviations did not correlate with the increased TT cuff pressure. In three cases of temporary RLN palsy, the mean cumulative case TT cuff pressure was significantly higher (24.8mmHg, p = 0.02). This study demonstrates that TT cuff pressure and RLN conductivity can change significantly with manipulation of the thyroid and that high TT cuff pressures may be associated with RLN injuries.

Tracheal tube cuff pressure monitoring: Assessing current practice in critically ill patients at Chris Hani Baragwanath Academic Hospital.

Intubated patients with a high tracheal tube cuff pressure (CP) are at risk of developing tracheal or subglottic stenosis. Recently an increasing number of patients have presented to our hospital with these complications. To determine the frequency of tracheal tube CP measurements and the range of CP and to explore nursing knowledge regarding CP monitoring. Frequency of CP measurement was assessed using a prospective chart review, followed by an interventional component. In the final stage nurses completed a self-administered questionnaire. A total of 304 charts from 61 patients were reviewed. Patients' ages ranged from 1 to 71 years, with a male preponderance (1.5:1). The majority of charts (87%) did not reflect a documented CP measurement and only 12 charts showed at least one measurement per shift. Only 17% of recorded CPs were within the recommended range; 59% were too low. The questionnaire was completed by only 51% of the 75 respondents. Nursing experience ranged from 3 to 35 years and 92% of respondents were trained in critical care. Knowledge of current critical care CP monitoring guidelines was reported by 62% of the respondents (n=23/37). Only 53% (20/38) reported routinely measuring CP. Almost all respondents (94%) knew of at least one complication of abnormal CP. Having a basic knowledge of CP measurement, having awareness of the complications of abnormal CP and the availability of national best practice guidelines did not translate into appropriate ICU practice. Research into effective implementation strategies to achieve best practice is needed. Basic knowledge of cuff pressure measurement may not always result in best practice.Improvement in current practice requires research into effective implementation strategies.

The effect of pressure support on imposed work of breathing during paediatric extubation readiness testing

BackgroundPaediatric critical care practitioners often make use of pressure support (PS) to overcome the perceived imposed work of breathing (WOBimp) during an extubation readiness test (ERT). However, no paediatric data are available that shows the necessity of adding of pressure support during such tests. We sought to measure the WOBimp during an ERT with and without added pressure support and to study its clinical correlate. This was a prospective study in spontaneously breathing ventilated children < 18 years undergoing ERT. Using tracheal manometry, WOBimp was calculated by integrating the difference between positive end-expiratory pressure (PEEP) and tracheal pressure (Ptrach) over the measured expiratory tidal volume (VTe) under two paired conditions: continuous positive airway pressure (CPAP) with and without PS. Patients with post-extubation upper airway obstruction were excluded.ResultsA total of 112 patients were studied. Median PS during the ERT was 10 cmH2O. WOBimp was significantly higher without PS (median 0.27, IQR 0.20–0.50 J/L) than with added PS (median 0.00, IQR 0.00–0.11 J/L). Although there were statistically significant changes in spontaneous breath rate [32 (23–42) vs. 37 (27–46) breaths/min, p < 0.001] and higher ET-CO2 [5.90 (5.38–6.65) vs. 6.23 (5.55–6.94) kPa, p < 0.001] and expiratory Vt decreased [7.72 (6.66–8.97) vs. 7.08 (5.82–8.08) mL/kg, p < 0.001] in the absence of PS, these changes appeared clinically irrelevant since the Comfort B score remained unaffected [12 (10–13) vs. 12 (10–13), P = 0.987]. Multivariable analysis showed that changes in WOBimp occurred independent of endotracheal tube size.ConclusionsWithholding PS during ERT does not lead to clinically relevant increases in WOBimp, irrespective of endotracheal tube size.

Effect of Apneic Oxygenation on Tracheal Oxygen Levels, Tracheal Pressure, and Carbon Dioxide Accumulation: A Randomized, Controlled Trial of Buccal Oxygen Administration.

Apneic oxygenation via the oral route using a buccal device extends the safe apnea time in most but not all obese patients. Apneic oxygenation techniques are most effective when tracheal oxygen concentrations are maintained >90%. It remains unclear whether buccal oxygen administration consistently achieves this goal and whether significant risks of hypercarbia or barotrauma exist. We conducted a randomized trial of buccal or sham oxygenation in healthy, nonobese patients (n = 20), using prolonged laryngoscopy to maintain apnea with a patent airway until arterial oxygen saturation (SpO2) dropped <95% or 750 seconds elapsed. Tracheal oxygen concentration, tracheal pressure, and transcutaneous carbon dioxide (CO2) were measured throughout. The primary outcome was maintenance of a tracheal oxygen concentration >90% during apnea. Buccal patients were more likely to achieve the primary outcome (P < .0001), had higher tracheal oxygen concentrations throughout apnea (mean difference, 65.9%; 95% confidence interval [CI], 62.6%-69.3%; P < .0001), and had a prolonged median (interquartile range) apnea time with SpO2 >94%; 750 seconds (750-750 seconds) vs 447 seconds (405-525 seconds); P < .001. One patient desaturated to SpO2 <95% despite 100% tracheal oxygen. Mean tracheal pressures were low in the buccal (0.21 cm·H2O; SD = 0.39) and sham (0.56 cm·H2O; SD = 1.25) arms; mean difference, -0.35 cm·H2O; 95% CI, 1.22-0.53; P = .41. CO2 accumulation during early apnea before any study end points were reached was linear and marginally faster in the buccal arm (3.16 vs 2.82 mm Hg/min; mean difference, 0.34; 95% CI, 0.30-0.38; P < .001). Prolonged apnea in the buccal arm revealed nonlinear CO2 accumulation that declined over time and averaged 2.22 mm Hg/min (95% CI, 2.21-2.23). Buccal oxygen administration reliably maintains high tracheal oxygen concentrations, but early arterial desaturation can still occur through mechanisms other than device failure. Whereas the risk of hypercarbia is similar to that observed with other approaches, the risk of barotrauma is negligible. Continuous measurement of advanced physiological parameters is feasible in an apneic oxygenation trial and can assist with device evaluation.

Flow-controlled ventilation during ear, nose and throat surgery: A prospective observational study.

Flow-controlled ventilation (FCV) is a new mechanical ventilation mode that maintains constant flow during inspiration and expiration with standard tidal volumes via cuffed narrow-bore endotracheal tubes. Originating in manually operated 'expiratory ventilation assistance', FCV extends this technique by automatic control of airway flow, monitoring of intratracheal pressure and control of peak inspiratory pressure and end-expiratory pressure. FCV has not yet been described in a clinical study. The aim of this study was to provide an initial assessment of FCV in mechanically ventilated patients undergoing ear, nose and throat surgery and evaluate its potential for future use. An observational study. Two German academic medical centres from 24 November 2017 to 09 January 2018. Consecutive patients (≥ 18 years) scheduled for elective ear, nose and throat surgery. Exclusion criteria were planned laser surgery, intended fibreoptic awake intubation, emergency procedures, increased risk of aspiration, American Society of Anesthesiologists (ASA) physical status more than III and chronic obstructive pulmonary disease classified as GOLD stage more than II. Peri-operative use of FCV provided by a new type of ventilator (Evone) via a narrow-bore endotracheal tube (Tritube). Minute volume, respiratory rate, intratidal tracheal pressure amplitude (Δp) and end-tidal CO2 (PetCO2) were recorded every 5 min. All adverse events were noted. Data are presented as median [IQR]. Sixteen patients provided 15 evaluable data sets. A minute volume of 5.0 [4.4 to 6.4] l min and a respiratory rate of 9 [8 to 11] min generated a PetCO2 of 4.9 [4.8 to 5.0] kPa. Δp was 10 [9 to 12] cmH2O. Five adverse events were recorded: a tube obstruction due to airway secretions and four tube dislocations (two attributed to coughing, two not study-related). FCV achieves adequate PetCO2 levels with minute volume and Δp in the normal range. Tritube's high flow resistance may increase the likelihood of tube dislocations if the patient coughs. Although further evaluation is necessary, FCV provides a new option for short-term mechanical ventilation. The successful operation of FCV with narrow-bore tubes contributes to the armamentarium for airway management. DRKS00013312.

Carbon dioxide diffusion coefficient in noninvasive high-frequency oscillatory ventilation.

The carbon dioxide (CO2 ) diffusion coefficient (DCO 2 ) reflects CO 2 removal during high-frequency oscillatory ventilation (HFOV). We hypothesized that despite leak flow during noninvasive HFOV (nHFOV) DCO 2 continues to indicate ventilation efficacy. A neonatal airway model including CO2 production and an adjustable oropharyngeal leak was connected to a ventilator via bi-nasal prongs. Pressures and gas flows were measured at prongs, trachea, and leak. Oscillatory tidal volumes below (V T trachea ) and above the leak (V T prong ) were calculated from tracheal and leak flows. DCO 2 was calculated using V T trachea (DCO 2 trachea ) and V T prong (DCO 2 prong ) and compared with CO 2 partial pressure (pCO 2 ). Effects of leak flow (0, 5, or 10L/min) on DCO 2 were assessed at fixed pressure amplitudes or predefined oscillatory volumes under steady-state pCO 2 conditions in the modeled lung. DCO2 trachea correlated strongly with pCO 2 , independent of the leak flow level (P < 0.0001). DCO 2 prong correlated with pCO 2 without and with moderate leak (P < 0.0001) but not with maximum leak (P = 0.1432). V T trachea correlated with the quotient of tracheal pressure amplitude and frequency irrespective of the leak (P < 0.0001). Based on the pressure amplitude at prong level (A prong ) V T trachea continued to follow a linear model of which the slopes decreased with increasing leak flow. V T prong correlated with the quotient of A prong and frequency, irrespective of the leak (P < 0.0001). DCO2 obtained at the airway opening at prong level reflects ventilation efficacy during nHFOV even in the presence of moderate oropharyngeal leak.

High flow nasal cannula: Influence of gas type and flow rate on airway pressure and CO2 clearance in adult nasal airway replicas

BackgroundHigh flow nasal cannula therapy is a form of respiratory support which delivers high flow rates of heated, humidified gas to the nares via specialized cannula. Two primary mechanisms of action attributed to the therapy are the provision of positive airway pressure as well as clearance of CO2-rich exhaled gas from the upper airways. MethodsPhysiologically accurate nose-throat airway replicas were connected at the trachea to a lung simulator, where CO2 was supplied to mimic the CO2 content in exhaled gas. Cannula delivered either air, oxygen or heliox (80/20%volume helium/oxygen) to the replicas at flow rates ranging from 0 to 60 l/min. Five replicas and three cannulas were compared. Tracheal pressure and CO2 concentration were continuously measured. The lung simulator provided breaths with tidal volume of 500 ml and frequency of 18 breaths/min. Additional clearance measurements were conducted for tidal volume and breathing frequency of 750 ml and 27 breaths/min, respectively. FindingsCannula flow rate was the dominant factor governing CO2 concentration. Average CO2 concentration decreased with increasing cannula flow rate, but above 30 L/min this effect was less pronounced. Tracheal positive end-expiratory pressure increased with flow rate and was lower for heliox than for air or oxygen. A predictive correlation was developed and used to predict positive end-expiratory pressure for a given cannula size as a function of supplied flow rate and occlusion of the nares. InterpretationCompared with administration of air or oxygen, administration of heliox is expected to result in similar CO2 clearance from the upper airway, but markedly lower airway pressure.

An Artificial Cough Maneuver to Remove Secretions From Below the Endotracheal Tube Cuff.

Endotracheal suctioning is mandatory to prevent complications caused by the retention of tracheal secretions. Endotracheal suctioning is often performed late, when patients show signs of respiratory and hemodynamic alterations. We conceived a prototype device that, when synchronized with the ventilator, automatically removes secretions collected below the endotracheal tube (ETT) cuff, thus avoiding endotracheal suctioning. The aim of our investigation was to assess the performance of this novel prototype in vitro. Three studies were performed to examine the characteristics of the prototype. We tested device's ability to generate an effective artificial cough flow (artificial cough maneuver) > 1 L/s by rapidly deflating the ETT cuff within the time of a sustained inflation (at 30 and at 40 cm H2O) (cough flow study). We also tested the prototype's ability to remove the fluid positioned below the ETT cuff using saline dye (fluid removal study), and to prevent the aspiration of saline dye from above the ETT cuff during the deflation phase of the ETT cuff (aspiration study). The trachea model was positioned at 45° in the aspiration study, and horizontally in the other two studies. In the cough flow study, the prototype provided an effective artificial cough maneuver, with a mean ± SD of 1.78 ± 0.19 L/s (range, 1.42-2.14 L/s). The tracheal pressure after ETT cuff deflation never decreased below the PEEP level. In the fluid removal study, the prototype cleared the fluid from below the ETT cuff and the experimental trachea. No fluid was aspirated from the area above the ETT cuff toward the lower airways. We conceived an system capable of automatically expelling fluid from below the ETT cuff outside an experimental trachea by generating an artificial cough maneuver. This system may decrease the use of endotracheal suctioning and its complications. Future in vivo studies are needed to confirm this first in vitro evaluation.

Comparison of tracheal tube cuff pressure with two technique: fixed volume and minimal leak test techniques.

Introduction: There is a correlation between endotracheal cuff pressure and airway complication; therefore, cuff pressure measurement is of an essential importance. The gold standard technique is measuring the cuff pressure by a calibrated manometer. However, there are several methods that injects air into balloon pilot and measures the cuff pressure. The aim of this study is to compare the tracheal cuff pressure measurement by two methods: fixed volume and minimal leak test (MLT). Methods: This descriptive study was performed at the emergency department on 110 patients. Patients were randomized into two groups. For one group, fixed volume technique and for the other group MLT was used. Results: Mean cuff pressure was 46.07±23.54 cmH2O in the fixed volume group and 33.72±9.14 cmH2O in the MLT group (P=0.05) which is significantly higher in the fixed volume group (P=0.028). In addition, 56.4% and 78.2% of the subjects had normal cuff pressure in the fixed volume group and MLT group, respectively; indicating a significantly higher rate in MLT group (P=0.025). Conclusion: Both techniques cause above normal intracuff pressure; however, MLT produces more acceptable pressure than fixed volume. It seems that the volume of 10 cc produces high pressures; therefore, fixed values may yield more appropriate results in lower volumes.

Microcuff Pediatric Endotracheal Tubes: Evaluation of Cuff Sealing Pressure, Fiber-optic Assessment of Tube Tip, and Cuff Position by Ultrasonography.

Background:Use of uncuffed tubes causes lots of morbidity, and there is a surge in the use of microcuff pediatric endotracheal tubes. These tubes are not evaluated in the Indian population.Aims:The study aimed to evaluate the pediatric microcuff endotracheal tubes in terms of cuff sealing pressure, fiber-optic assessment of tube tip, and cuff position to assess postextubation airway morbidity.Settings and Design:Study design involves follow-up analytical study.Subjects and Methods:Thirty-four children in the age group of 2–12 years were studied. Patients with leak pressure >20 cm H2O were exchanged with smaller size tube and excluded. Cuff pressure, fiber-optic assessment of tube tip to carina distance in neutral and flexion, ultrasound assessment of cuff position, and postextubation airway morbidity were assessed.Statistical Analysis Used:Parameters expressed as the median with the interquartile range. Nonparametric data were analyzed using the Wilcoxon signed-rank test.Results:The tracheal leak pressure was <20 cm H2O (median 14.5 cm H2O) in 30 children. Tube exchange was required in four patients. A complete seal was achieved in 30 patients with cuff pressures ranging from 6 to 8.25 cm of H2O (median 8 cm of H2O). The median caudal displacement is 0.8 cm (0.47–1.22 cm) with flexion. There was no airway-related morbidity in any of these patients.Conclusions:The microcuff pediatric endotracheal tubes when used according to the age-based formula had a higher tube exchange rate in our study population. However, in children in whom the tube size was appropriate, the tubes provided good sealing without increasing airway morbidity. Further studies with a larger sample size might be required to confirm the findings.

Evaluation of the accuracy of finger-tip palpation of pilot balloon as a method to judge endo tracheal tube cuff pressure

Evaluation of the accuracy of finger-tip palpation of pilot balloon as a method to judge endo tracheal tube cuff pressure

Association between core body temperature and mean airway pressure with endotracheal cuff pressure in intubated patients of emergency department.

Background & Objective:Endotracheal intubation is routinely performed in the critical situations. In order to prevent microaspiration and tracheal injury endotracheal cuff pressure is important to remain constant between 20 and 30 cmH2O. Positive pressure ventilation, duration of intubation, body temperature, and body movements can alter endotracheal cuff pressure. This survey was conducted to evaluate core body temperature and cuff pressure relation with airway pressure simultaneously.Methods:This was a descriptive analytic study conducted from March 2018 to July 2018 on 150 intubated patients in the emergency department. All were ventilated with SIMV mode and had Ramsi sedation level of 2-3. Mean airway pressure was measured simultaneouly with core body temperature measurement from ventilator monitor. All these parameters were measured 10 times each hour and documented.Results:There was a statistically meaningful relation between airway pressure and cuff pressure in the primary evaluation (P=0.02, r=0.19), while none of the subsequent evaluations showed meaningful relation (P>0.05). No significant relation was found between cuff pressure and core body temperature in any of the measurements (P>0.05).Conclusion:The pressure of cuff should be checked repeatedly after intubation because of substantial variation over time. Factors other than core body temperature and airway pressure can influence cuff pressure.

Is continuous better than intermittent control of tracheal cuff pressure? A meta-analysis.

To compare and evaluate the efficacy and safety of continuous and intermittent control of cuff pressure. We performed a comprehensive and systematic meta-analysis of randomized controlled trials (RCTs) assessing the continuous and intermittent control of Pcuff by searching PUBMED, EMBASE and other such databases (from inception to 31 March 2018). Summary odds ratios or mean differences with 95% confidence intervals were calculated using a fixed- or random-effects model. Seven randomised controlled trials with 970 mechanically ventilated patients were included in this study. The continuous control of cuff pressure significantly reduced the incidence of cuff pressure < 20 cm H2 O (0.03 (OR) (95% CI: 0.01-0.07)), Pcuff > 30 cm H2 O (0.06 (95% CI: 0.03-0.15)) and VAP (0.39 (95% CI: 0.28-0.55)) when compared with intermittent control of cuff pressure. No significant differences in duration of MV (-1.94 (95% CI: -4.06 to -0.17)), length of ICU stay (-3.88 (95% CI: -9.00 to -1.23)) and mortality (0.99 (95% CI: 0.73-1.35)) were found between the two groups. Continuous control of cuff pressure offers more benefits in stabilizing the cuff pressure and reducing the incidence of VAP, and more studies are warranted to further evaluate the role of continuous control of cuff pressure. The continuous control of cuff pressure should be conducted whenever possible as it is the most ideal for the prognosis of MV patients.

Devising negative pressure within intercuff space reduces microaspiration

BackgroundMicroaspiration past the tracheal tube cuffs causes ventilator-associated pneumonia. The objective of the current study was to evaluate whether creating negative pressure between the tracheal double cuffs could block the fluid passage past the tracheal tube cuffs.MethodsA new negative pressure system was devised between the double cuffs through a suction hole in the intercuff space. Blue-dyed water was instilled above the cuff at negative suction pressures of − 54, − 68, − 82, − 95, − 109, − 122, and − 136 cmH2O, and the volume leaked was measured in an underlying water trap after 10 min. Leakage tests were also performed during positive pressure ventilation, and using higher-viscosity materials. The actual negative pressures delivered at the hole of double cuffs were obtained by placing microcatheter tip between the intercuff space and the artificial trachea.ResultsNo leakage occurred past the double cuff at − 136 cmH2O suction pressure at all tracheal tube cuff pressures. The volume leaked decreased significantly as suction pressure increased. When connected to a mechanical ventilator, no leakage was found at − 54 cmH2suction pressure. Volume of the higher-viscosity materials (dynamic viscosity of 63–108 cP <cP> and 370–430 cP) leaked was small compared to that of normal saline (0.9–1.1 cP). The pressures measured in the intercuff space corresponded to 3.8–5.9% of those applied.ConclusionsA new prototype double cuff with negative pressure in the intercuff space completely prevented water leakage. The negative pressure transmitted to the tracheal inner wall was a small percentage of that applied.

A Novel Non-invasive Approach for Measuring Upper Airway Collapsibility in Mice.

Introduction: Invasive procedures were previously developed for measuring pharyngeal collapsibility in rodents during expiration, when declining neuromuscular activity makes the airway unstable. We developed a non-invasive approach for streamlining collapsibility measurements by characterizing responses in physiologic markers of dynamic expiratory airflow obstruction to negative nasal pressure challenges.Methods: Anesthetized mice were instrumented to monitor upper airway pressure-flow relationships with head-out plethysmography while nasal pressure was ramped down from ~ +5 to −20 cm H2O over several breaths. Inspiratory and expiratory flow, volume, and timing characteristics were assessed breath-wise. Pcrit was estimated at transitions in expiratory amplitude and timing parameters, and compared to gold standard PCRIT measurements when nasal and tracheal pressures diverged during expiration. Predictions equations were constructed in a development data set (n = 8) and applied prospectively to a validation data set (n = 16) to estimate gold standard PCRIT.Results: The development data demonstrated that abrupt reversals in expiratory duration and tidal volume during nasal pressure ramps predicted gold standard PCRIT measurements. After applying regression equations from the development to a validation dataset, we found that a combination of expiratory amplitude and timing parameters proved to be robust predictors of gold standard PCRIT with minimal bias and narrow confidence intervals.Conclusions: Markers of expiratory airflow obstruction can be used to model upper airway collapsibility, and can provide sensitive measures of changes in airway collapsibility in rodents. This approach streamlines repeated non-invasive PCRIT measurements, and facilitates studies examining the impact of genetic, environmental, and pharmacologic factors on upper airway control.

In-vitro analysis of a novel 'add-on' silicone cuff to improve sealing properties of tracheal tubes.

Leakage of colonised oropharyngeal secretions across the tracheal tube cuff may cause iatrogenic pulmonary infection. We studied a novel 'add-on' cuff, which can be inserted over an existing tracheal tube and advanced into the subglottic region. The physical properties of the novel silicone cuff (BronchoGuard, Ciel Medical, USA) were evaluated in comparison with the Hi-Lo® tracheal tube. In a bench study, we identified saline inflation volumes required to transmit pressures between 15 and 30cmH2 O against artificial tracheas of 18, 20 and 22mm internal diameter. We computed cuff compliance, and minimal inflation volume to achieve air sealing during mechanical ventilation. Finally, we compared the leakage flow rate of artificial saliva across the novel cuff. On average, the mean (SD) inflation volumes necessary to transmit tracheal pressures of 15, 20, 25 and 30cmH2 O were 4.1 (2.2), 4.4 (2.3), 4.6 (2.4) and 4.8 (2.4) ml for the novel cuff and 7.7 (2.5), 8.0 (2.6), 8.4 (2.6) and 8.7 (2.7) ml for the Hi-Lo tube, respectively (p<0.001). The minimal inflation volumes to achieve air sealing were 3.8 (0.9) and 10.5 (2.1) ml (p<0.001), which resulted in transmitted tracheal pressures of 8.3 (9.8) and 27.6 (34.8)cmH2 O (p<0.001). Compliance was 0.026 (0.004) and 0.616 (0.324) ml.cmH2 0-1 , respectively (p<0.001). Although massive leak was found when the novel cuff transmitted pressures ≤20cmH2 O against the trachea, leakage was avoided with pressures ≥25cmH2 O, owing to optimal contact between the cuff and the tracheal wall. In contrast, the standard cuff consistently leaked irrespective of the pressure. We conclude that the novel cuff has advantageous properties that warrant clinical corroboration.

Magnesium Sulfate Nebulizer versus Ketamine Nebulizer in Decreasing Incidence and Severity of Post Operative Sore Throat with Endotracheal Intubation in Adults

Background: Endotracheal intubation is the prominent cause of airway mucosal injury which results in postoperative sore throat (POST), with an incidence of 21%–65%. Although this complication is minor, if left unresolved, it produces significant agony and annoyance to the patient. Aim of the Work: to compare efficacy of magnesium/ nebulizer versus ketamine nebulizer in decreasing postoperative sore throat incidence, severity and duration with fixed endotracheal tube intra cuff pressure at or below 20 cm H2O using handheld tracheal cuff pressure monitor in adults ASA (American Society of Anesthesiologists) I-II in 20-60 years age group of either sex in operations less than 2 hours. Methodology: our study included 90 adult patients, status I-II (ASA I-II) in the age group 20-60 years, of either sex undergoing operation under general anesthesia (GA) scheduled for a day case surgery and operation time less than 2 hours with fixation of endotracheal tube cuff at 20 cm H2O using hand held tracheal cuff pressure monitor (Pressure Gauge) and checked every half hour till end of surgery and maintained at or below 20 cm H2O. Results: Our study showed reduction in POST incidence and severity after preoperative magnesium sulfate nebulization in all time points 0, 2, 4, 8, 12 and 24 hours postoperative, so it was proved that magnesium nebulizer has great role in reduction of incidence, severity and duration of POST. Conclusion: we concluded that preoperative magnesium sulfate nebulization reduce incidence and severity of POST and it is more effective than preoperative ketamine nebulization.

Using twitch tracheal airway pressure, negative inhale forced pressure, and Medical Research Council score to guide weaning from mechanical ventilation.

Weaning from mechanical ventilation (MV) is an important and universal issue in critically ill patients, with no consensus that predicts weaning success. Twitch tracheal airway pressure (TwPtr) may be a more objective indicator of diaphragm function. The present study evaluated TwPtr relative to negative inspiratory force (NIF) or Medical Research Council (MRC) score, for predicting success of weaning from MV. From December 2015 to March 2017, 62 patients were included who received invasive MV >48 hours and then underwent a test for spontaneous breathing. The NIF and MRC score were sequentially determined. The TwPtr measurement was performed via magnetic stimulation of the neck phrenic nerve. Weaning success was achieved by 54 patients (87.1%), including 30, 12, and 12 patients who experienced simple, difficult, and prolonged weaning, respectively. The areas under receiver operating characteristic curves (AUCs) for NIF, MRC score, and TwPtr were 0.778, 0.560, and 0.792. When TwPtr was combined with NIF, the sensitivity and specificity of weaning success were 96.3% and 75.0%, and AUC was 0.807. In the weaning success group, after correction for age, the AUC of TwPtr was 0.878, which differentiated the simple weaning from non-simple group. TwPtr was superior to either NIF or MRC score for differentiating patients in the simple weaning group from those patients who experienced difficult, prolonged, or failed weaning. TwPtr combined with NIF may be used to predict weaning success better than the MRC score alone.

Effects of Increasing Airway Pressures on the Pressure of the Endotracheal Tube Cuff During Pelvic Laparoscopic Surgery.

Tracheal tube cuff pressures exceeding the perfusion pressures of the tracheal mucosa have been associated with complications such as sore throat, tracheal mucosa ulcers, tracheal rupture, and subglottic stenosis. Despite appropriate inflation, many factors can increase the tracheal cuff pressure during mechanical ventilation. This prospective observational cohort study was designed to test the hypothesis that during a clinical model of decreasing respiratory compliance, the pressure within the endotracheal tube cuff will rise in direct relationship to increases in the airway pressures. Twenty-eight adult obese patients (BMI ≥30 kg/m) scheduled for elective laparoscopic gynecologic procedures were enrolled. All patients received general anesthesia utilizing endotracheal tubes with low-pressure high-volume cuffs. After baseline adjustment of the cuff pressure to 25 cm H2O, the airway pressures and endotracheal cuff pressures were continuously measured using pressure transducers connected to the anesthesia circuit and cuff pilot, respectively. Data on cuff and airway pressures, mechanical ventilation parameters, intraabdominal pressures, and degree of surgical table inclination were collected throughout the anesthetic procedure. General linear regression models with fixed and random effects were fit to assess the effect of increases in airway pressures on cuff pressure, after adjusting for covariates and the clustered structure of the data. The mean (standard deviation) age and body mass index were 42.2 (8.8) years and 37.7 (5.1) kg/m, respectively. After tracheal intubation, the cuffs were overinflated (ie, intracuff pressures >30 cm H2O) in 89% of patients. The cuff pressures significantly changed after concomitant variations in the airway pressures from a mean (standard error) value of 29.6 (1.30) cm H2O before peritoneal insufflations, to 35.6 (0.68) cm H2O after peritoneal insufflation, and to 27.8 (0.79) cm H2O after peritoneal deflation (P < .0001). The multilevel mixed regression models revealed that after controlling for clustering of the data (at the patient and study phase levels) and covariates, increased peak airway pressures were significantly associated with increased pressures within the endotracheal cuff (coefficient [95% confidence interval], 0.25 [0.14-0.36]; P < .0001). Other variables associated with increasing endotracheal cuff pressure included degree of surgical table inclination (0.08 [0.04-0.12]; P = .0003) and I:E ratio of 1:1 (4.47 [2.10-6.83]; P = .0002). This clinical model of decreased respiratory compliance in mechanically ventilated patients reveals that the pressure within the endotracheal cuff significantly changes in direct relation to changes in the airway pressures. This finding may have clinical relevance in patients requiring prolonged use of high airway pressures.

Paced breathing and phrenic nerve responses evoked by epidural stimulation following complete high cervical spinal cord injury in rats.

Spinal cord injury (SCI) at the level of cervical segments often results in life-threatening respiratory complications and requires long-term mechanical ventilator assistance. Thus restoring diaphragm activity and regaining voluntary control of breathing are the primary clinical goals for patients with respiratory dysfunction following cervical SCI. Epidural stimulation (EDS) is a promising strategy that has been explored extensively for nonrespiratory functions and to a limited extent within the respiratory system. The goal of the present study is to assess the potential for EDS at the location of the phrenic nucleus (C3-C5) innervating the diaphragm: the main inspiratory muscle following complete C1 cervical transection. To avoid the suppressive effect of anesthesia, all experiments were performed in decerebrate, C1 cervical transection, unanesthetized, nonparalyzed ( n = 13) and paralyzed ( n = 7) animals. Our results show that C4 segment was the most responsive to EDS and required the lowest threshold of current intensity, affecting tracheal pressure and phrenic nerve responses. High-frequency (200-300 Hz) EDS applied over C4 segment (C4-EDS) was able to maintain breathing with normal end-tidal CO2 level and raise blood pressure. In addition, 100-300 Hz of C4-EDS showed time- and frequency-dependent changes (short-term facilitation) of evoked phrenic nerve responses that may serve as a target mechanism for pacing of phrenic motor circuits. The present work provides the first report of successful EDS at the level of phrenic nucleus in a complete SCI animal model and offers insight into the potential therapeutic application in patients with high cervical SCI. NEW & NOTEWORTHY The present work offers the first demonstration of successful life-supporting breathing paced by epidural stimulation (EDS) at the level of the phrenic nucleus, following a complete spinal cord injury in unanesthetized, decerebrate rats. Moreover, our experiments showed time- and frequency-dependent changes of evoked phrenic nerve activity during EDS that may serve as a target mechanism for pacing spinal phrenic motor networks.