High Airway Pressures Research Articles

Use of ProSeal(®) LMA and thoracic epidural in myasthenia patients for trans-sternal thymectomy: A case series.

Myasthenia gravis is an autoimmune disease, resulting from the production of antibodies against the acetylcholine receptors of the neuromuscular endplate. Muscular weakness and fatigability are the hallmarks of myasthenia gravis. Myasthenic patients are sensitive to non-depolarising relaxants and post-operative ventilatory support may be required in high-risk patients. This can be attributed partly to endotracheal intubation and use of intermediate or long-acting muscle relaxants in such cases. The rate of post-operative ventilation after a trans-sternal thymectomy has been reported to be more than 50% in myasthenia gravis patients.[1] Two techniques have been recommended for general anaesthesia in the myasthenic patient. Due to the unpredictable response to succinylcholine and the marked sensitivity to non-depolarising muscle relaxants, some anaesthesiologists avoid muscle relaxants and depend on deep inhalational anaesthesia for tracheal intubation and maintenance of anaesthesia.[2,3] However, others utilise a balanced technique which includes the use of muscle relaxants, without the need for deep inhalational anaesthesia with its concomitant respiratory and cardiovascular side effects, provided neuromuscular transmission is monitored. In this paper, we would like to describe a new and successful technique of using ProSeal® laryngeal mask airway (LMA) with thoracic epidural for three cases who underwent trans-sternal thymectomy. We avoided muscle relaxant during the entire course of surgery and none of our cases required post-operative ventilation.

Differential diagnosis of high peak airway pressures.

The sickest patients often require mechanical ventilation. Although mechanical ventilation is often a lifesaving intervention for many, it can also have life-threatening complications. Monitoring a patient on mechanical ventilation requires skill and prompt troubleshooting to ensure its proper function. The high peak airway pressure (HPAP) alarm is one of the most common alarms. It is critically important that clinicians understand the pathophysiology of the lung and the various causes behind the alarm and have a working differential diagnosis for the causes of HPAPs. The differential diagnosis for HPAP is extensive but can be managed quickly and effectively if you follow a systematic approach. In this article, we aim to describe the basics of respiratory mechanics that contribute to HPAP alarms and describe concepts such as airway resistance, lung compliance, peak airway pressures, and plateau pressures. This is followed by a systematic approach to diagnosing the cause of the HPAP alarm. The list of probable causes of HPAP is extensive. Many causes may be overlooked when there is not a clear understanding of its meaning and potential danger. Providing this algorithm gives relevance and importance to understanding the HPAP alarm and provides essential information for troubleshooting potentially dangerous situations.

Uncommon complication of bilevel positive airway pressure.

Sir, A 60-year-old lady was admitted in the intensive care unit with shortness of breath. She was having coarse bilateral crepitations with saturation of 85% on pulse oximetry. She was diagnosed as a case of dilated cardiomyopathy with severe left ventricular dysfunction. Adrenaline infusion was started to optimize blood pressure. Frusemide was given as decongestive therapy. Bilevel positive airway pressure (BiPAP) with orofacial interface was applied with setting of inspiratory positive airway pressure 14 and expiratory positive airway pressure 7. After 1 h of therapy, saturation started improving; however patient started complaining of right ear pain. Otoscopic examination revealed bulging right tympanic membrane. High positive airway pressure by BiPAP might have caused raised middle ear pressure leading to pain. BiPAP was applied after inserting well lubricated nasal airway size 7 mm in right nasal passage. Patient's ear pain gradually subsided and patient was much comfortable. Noninvasive positive pressure ventilation is commonly used in the treatment of patients with acute respiratory failure.[1] Noninvasive ventilation can avoid morbidity associated with invasive ventilation.[2] The inspiratory positive airway pressure in BiPAP decrease the work of breathing and the expiratory positive airway pressure increase the functional residual capacity of the lung by recruiting collapsed alveoli. Common complication of BiPAP such as mask related minor injury to the skin of the face (laceration, ulcer) occurs in approximately 13% of patients.[3] Other complications include irritation to the eyes from the mask ventilation, irritation to the nasal mucosa, or drying of the upper airway passages, gastric distention (incidence rate, 2%).[4] Positive airway pressure delivered by BiPAP can cause rise in middle ear pressure through eustachian tube as in the present case. It can predispose patient to otitis media and trauma to middle ear structures. In the present case, such complications were avoided by using nasal airway which protected the eustachian tube from transmitting the airway pressure. We do not propose to insert nasal airway in every patient on BiPAP but can be considered in patients complaining of ear pain and history of repeated ear infections. One could also reduce the airway pressure setting to reduce the pressure in the middle ear.

An extracorporeal artificial placenta supports extremely premature lambs for 1 week

PurposeThe treatment of extreme prematurity remains an unsolved problem. We developed an artificial placenta (AP) based on extracorporeal life support (ECLS) that simulates the intrauterine environment and provides gas exchange without mechanical ventilation (MV) and compared it to the current standard of neonatal care. MethodsExtremely premature lambs (110–120days; term=145d) were used. AP lambs (n=9) were cannulated (jugular drainage, umbilical vein reinfusion) for ECLS. Control lambs (n=7) were intubated, ventilated, given surfactant, and transitioned to high-frequency oscillatory ventilation. All lambs received parenteral nutrition, antibiotics, and steroids. Hemodynamics, blood gases, hemoglobin, and circuit flows were measured. ResultsFour premature lambs survived for 1week on the AP, with one surviving 6days. Adequate oxygenation and ventilation were provided by the AP. The MV lambs survived 2–8hours. Each of these lambs experienced a transient improvement with surfactant, but developed progressive hypercapnea and hypoxia despite high airway pressures and HFOV. ConclusionsExtremely premature lambs were supported for 1week with the AP with hemodynamic stability and adequate gas exchange. Mechanically ventilated lambs succumbed within 8hours. Further studies will assess control of fetal circulation and organ maturation on the AP.

Abstract 19663: Failed Delayed Sternal Closure Following Neonatal Cardiac Surgery Predicted by High Mean Airway Pressure and Associated with Increased Post-operative Mortality

Background: Myocardial edema, increased lung water, and anasarca are common following neonatal cardiac surgery with cardiopulmonary bypass and amplify the risk of hemodynamic instability and inadequate ventilation following sternal closure. Delayed sternal closure (DSC) in the intensive care unit one or more days following surgery is a common strategy to mitigate this risk, but has been associated with increased risk of infection. In addition, failed DSC has previously been identified as a risk factor for mortality. This study sought to identify predictor variables and determine impact of failed DSC. Methods: Records of all neonates undergoing DSC in the cardiac intensive care unit (CICU) following surgery with cardiopulmonary bypass between January 2008 and May 2013 were reviewed. Pre-operative, intra-operative and post-operative variables were compared for those patients who failed DSC versus those who did not. Continuous variables were compared utilizing Wilcoxon’s test and categorical variables using Fisher’s exact test. Results: Of 256 neonates undergoing DSC in the CICU, 22 failed first attempt at DSC. No significant difference between the two groups was appreciated in age, weight, or bypass (cross clamp, circulatory arrest, and total) times. Comparing DSC failures to successes, significantly more failures: followed Stage I palliation (63% vs. 31%); occurred later (post-operative day 4.7 vs. 2.8, p = 0.009); and were proceeded by higher mean airway pressures (9 vs. 8 cm H2O, p = 0.04), peak inspiratory pressure (27 vs. 24, p = 0.002), and inotrope score (12.1 vs. 9.6, p = 0.06). There was no association with systolic blood pressure or lactate prior to DSC. Failed DSC was associated with increased duration of mechanical ventilation (41.6 vs 7.4 days, p < 0.001), length of ICU stay (44.3 vs 12.0 days, p < 0.001), and mortality (38 vs 3%, p < 0.001). Conclusions: Mortality for patients who fail the first ICU attempt at delayed sternal closure is significantly higher than for those with successful sternal closure. Ventilatory pressures but not hemodynamic variables prior to DSC differed significantly between the two groups. First attempt at DSC was later in those who failed, suggesting that clinicians had a priori identified these patients as higher risk.

Lung re-inflation after one-lung ventilation for thoracic surgery: importance of clamping the dependent lung

To the Editor, Our thoracic surgeons routinely request that continuous positive airway pressure (CPAP) be applied to the nondependent (i.e., operated on) lung either to test the bronchial staple line after resection or to ensure lung reexpansion prior to chest closure. Although we generally use low airway pressure (i.e., 15 cm H2O), at times up to 30 cm H2O is needed to expand portions of the lung that have been chronically atelectatic. Application of these pressures to both lungs may result in the relatively compliant dependent lung receiving a greater proportion of the gas flow, which can increase its risk of volutrauma. In addition, prolonged inflation with relatively high pressures can excessively increase intrathoracic pressure and even result in a mediastinal shift, each of which can reduce venous return and lead to hypotension. In order to reduce these consequences, prior to applying the CPAP, we suspend ventilation and clamp the dependent lung lumen of the double-lumen endotracheal tube, thereby stopping gas flow to that lung. This measure not only protects the dependent lung from the high airway pressures, but also reduces the duration of CPAP application by expanding the non-dependent lung more rapidly, and thus decreases the risk of prolonged reduction in venous return. Although clamping the dependent lung prior to applying CPAP to the operative lung is not a novel technique, it has come to our attention that many anesthesiologists have not considered it. Indeed, residents who have come to our hospital for exposure to community anesthesia practice frequently note that this technique has not been taught in their training programs. Also, after observing the technique, they have expressed appreciation of its advantages. A potential objection to clamping flow to the dependent lung during a CPAP test is the potential to subjecting the patient to the risk of hypoxemia or hypercapnea. We have not found this been an issue, however. If anything, oxygen saturation improves as the alveoli are opened. Also, suspending ventilation for less than the minute it usually takes to re-expand the lung is unlikely to increase CO2 to any significant degree. Importantly, we have not observed hypotension during re-inflation using this lung-clamping CPAP technique. Despite the fact that there have been no clinical studies to determine that any one technique for lung re-expansion provides better results than any other, we think that this technique is a logical and relatively safe method to prevent potential volutrauma and/or hypotension.

“Open lung ventilation optimizes pulmonary function during lung surgery”

BackgroundWe evaluated an “open lung” ventilation (OV) strategy using low tidal volumes, low respiratory rate, low FiO2, and high continuous positive airway pressure in patients undergoing major lung resections. Materials and methodsIn this phase I pilot study, twelve consecutive patients were anesthetized using conventional ventilator settings (CV) and then OV strategy during which oxygenation and lung compliance were noted. Subsequently, a lung resection was performed. Data were collected during both modes of ventilation in each patient, with each patient acting as his own control. The postoperative course was monitored for complications. ResultsTwelve patients underwent open thoracotomies for seven lobectomies and five segmentectomies. The OV strategy provided consistent one-lung anesthesia and improved static compliance (40 ± 7 versus 25 ± 4 mL/cm H2O, P = 0.002) with airway pressures similar to CV. Postresection oxygenation (SpO2/FiO2) was better during OV (433 ± 11 versus 386 ± 15, P = 0.008). All postoperative chest x-rays were free of atelectasis or infiltrates. No patient required supplemental oxygen at any time postoperatively or on discharge. The mean hospital stay was 4 ± 1 d. There were no complications or mortality. ConclusionsThe OV strategy, previously shown to have benefits during mechanical ventilation of patients with respiratory failure, proved safe and effective in lung resection patients. Because postoperative pulmonary complications may be directly attributable to the anesthetic management, adopting an OV strategy that optimizes lung mechanics and gas exchange may help reduce postoperative problems and improve overall surgical results. A randomized trial is planned to ascertain whether this technique will reduce postoperative pulmonary complications.

Hyperpolarized gas diffusion MRI for the study of atelectasis and acute respiratory distress syndrome.

Considerable uncertainty remains about the best ventilator strategies for the mitigation of atelectasis and associated airspace stretch in patients with acute respiratory distress syndrome (ARDS). In addition to several immediate physiological effects, atelectasis increases the risk of ventilator-associated lung injury, which has been shown to significantly worsen ARDS outcomes. A number of lung imaging techniques have made substantial headway in clarifying the mechanisms of atelectasis. This paper reviews the contributions of computed tomography, positron emission tomography, and conventional MRI to understanding this phenomenon. In doing so, it also reveals several important shortcomings inherent to each of these approaches. Once these shortcomings have been made apparent, we describe how hyperpolarized (HP) gas MRI--a technique that is uniquely able to assess responses to mechanical ventilation and lung injury in peripheral airspaces--is poised to fill several of these knowledge gaps. The HP-MRI-derived apparent diffusion coefficient (ADC) quantifies the restriction of (3) He diffusion by peripheral airspaces, thereby obtaining pulmonary structural information at an extremely small scale. Lastly, this paper reports the results of a series of experiments that measured ADC in mechanically ventilated rats in order to investigate (i) the effect of atelectasis on ventilated airspaces, (ii) the relationship between positive end-expiratory pressure (PEEP), hysteresis, and the dimensions of peripheral airspaces, and (iii) the ability of PEEP and surfactant to reduce airspace dimensions after lung injury. An increase in ADC was found to be a marker of atelectasis-induced overdistension. With recruitment, higher airway pressures were shown to reduce stretch rather than worsen it. Moving forward, HP MRI has significant potential to shed further light on the atelectatic processes that occur during mechanical ventilation.

ABSTRACT 499

Background and aims: Pneumomediastinum is a potentially life-threatening complication in the paediatric patient on mechanical ventilation. High airway pressures may lead to an increase in the amount of air collected in the mediastinum and produce hemodynamic instability. Aims: The objective was to evaluate the effectiveness and safety of high-frequency oscillatory ventilation (HFOV) for respiratory failure with pneumomediastinum in pediatric patients. Methods: A retrospective chart review of all patients diagnosed with respiratory failure and pneumomediastinum who were hospitalised in the intensive care unit of the Beijing Children’s Hospital, China, from 2008 to 2013, was preformed. All patients presented with symptoms of respiratory distress and needed mechanical ventilation. HFOV were used to maintain oxygenation and Ventilation. No recruitment maneuvers were used and a strategy of permissive hypercapnia and hypoxaemia was used. Ventilatory settings, including FiO2 and mean airway pressue, and oxygen index were monitored. The study was approved by the institutional board review at our institution. Results: Twelve patients age 13month to 12years with acute respiratory failure and pneumomediastinum were treated with HFOV. The common causes of pneumomediastinum were pneumonia and asthmatic exacerbation. In addition to pneumomediastinum, all patients had subcutaneous emphysema, six a pneumothorax and one a pneumopericardium. Nine patients responded to HFOV and survived to discharge. The length of time using HFOV was 5 to 11 days. The other three patients did not respond to HFOV and died. Conclusions: HFOV with permissive hypercapnia and hypoxaemia strategy may be used effectively and safely in pediatric patients with respiratory failure and pneumomediastinum.

Cardiorespiratory Impact of Transesophageal Endoscopic Mediastinoscopy Compared With Cervical Mediastinoscopy

Transesophageal natural-orifice transluminal endoscopic surgery (NOTES) mediastinoscopy has been described as a feasible, less-invasive alternative to video-assisted mediastinoscopy (VAM). We aimed to investigate hemodynamic and respiratory effects during transesophageal NOTES mediastinoscopy compared with VAM. This was a short-survival experiment in 20 female pigs randomized to NOTES (n = 10) or VAM (n = 10) mediastinoscopy. In the NOTES group, an endoscopist accessed the mediastinum through a 5-cm submucosal tunnel in the esophageal wall, and CO2 was used to create the pneumomediastinum. Conventional VAM was carried out by thoracic surgeons. A 30-minute systematic exploration of the mediastinum was then performed, including invasive monitoring for hemodynamic and respiratory data. Blood samples were drawn for gas analyses. All experiments except 2 in the NOTES group (one because of technical difficulties, the other because of thoracic lymphatic duct lesion) were completed as planned, and animals survived 24 hours. Also, 3 animals in the NOTES group presented a tension pneumothorax that was immediately recognized and percutaneously drained. VAM and NOTES animals showed similar pulmonary and systemic hemodynamic behavior during mediastinoscopy. Pulmonary gas exchange pattern was mildly impaired during the NOTES procedure, showing lower partial arterial oxygen pressure associated with higher airway pressures (more important in animals that presented with pneumothorax). NOTES mediastinoscopy induces minimal deleterious respiratory effects and hemodynamic changes similar to conventional cervical VAM and could be feasible when performed under strict hemodynamic and respiratory surveillance. Notably, serious complications caused by the injury of pleura are more frequent in NOTES, which mandates an improvement in technique and suitable equipment.

Will the Taper Shaped Cuff Replace the Conventional High Volume-Low Pressured Cuff on Endotracheal Tube?

An effective tracheal seal plays an essential role in precluding aspiration and boosting efficiency with mechanical ventilation when endotracheal tube is inflated. High cuff pressure can cause damage to the tracheal wall and lead to serious complications such as tracheal stenosis. Endotracheal tube (ET) cuff pressures greater than 30 cmH2O may impede capillary blood flow in the tracheal wall, and ET cuff pressures greater than 50 cmH2O is considered high enough to completely block capillary blood flow.[1] Low volume high pressure cuff was used in early ETs but replaced by high volume low pressure (HVLP) cuff because the former causes mucosal injury along the lateral tracheal wall. HVLP cuffs appeared ideal because they are capable of producing a seal with low pressure. However, HVLP's large cuff diameter has emerged as a key issue as it is 1.5 to 2 times larger than the adult trachea. Longitudinal or oblique folds are developed upon inflation within the larger sized HVLP cuffs. The seal then becomes incomplete and allows secretions and air to leak as a result. Pulmonary aspiration of microorganism mass found in the oral cavity is considered one of leading causes of ventilator-associated pneumonia. In addition, over inflation of HVLP cuff can markedly increase cuff pressure, particularly around the folds and result in injury to the tracheal mucosa.[2] Low volume cuff tubes has recently drawn attention again while many researchers explored benefits of modified low volume low pressure (LVLP) cuff tubes. A taper-shaped cuff is designed to fit into the trachea at its narrow end and provides smaller cuff volume. This tapered cuff design is more effective in minimizing longitudinal folds when inflated, improving tracheal seal and preventing leakage of secretions and air even under high airway pressures, compared with conventional HVLP cuffs.[2,3] The transition from HVLP cuffs to taper-shaped cuffs is currently underway in endotracheal tubes. That is, the trend is moving back to low volume cuff tracheal tubes, which exert low pressure, in favor of better outcomes. Then we can have a question: Are tapered cuffs safe from pressure injury that is the most critical complication of low volume high pressure cuffs? While transmission of intracuff pressure to the tracheal wall depends on the cuff material, taper-shaped cuffs can transmit all the intracuff pressure to the tracheal wall.[4] In endoracheal position, the intracuff pressure of LVLP cuffs can be significantly increased by a slight change in inflating volume. In addition, the tapered cuff design provides smaller area of contact with the tracheal wall, compared to cylindrical shaped HVLP cuffs,[2] meaning that the extent of transmitted pressure is higher on the tracheal wall. It is therefore important to examine pressure changes with volume in tracheal tube cuff inflated. Special attention to pressure changes is also crucial in the tracheal tube cuff exposed to nitrous oxide for anesthesia because cuff pressure can significantly increase with increasing volume.[5] In case the taper-shaped cuff is not inflated adequately and develops an asymmetrical shape,

Use of filters in anaesthesia: Is it warranted?

Use of filters in anaesthesia: Is it warranted?

Pneumothorax following flexible fiberoptic bronchoscopy: A rare occurrence.

Sir, Pneumothorax following flexible fibreoptic bronhoscopy is rare. It occurs 1 in 450 bronchoscopy.[1] We report a case of such event in a trauma victim. A 34-year-old male patient with alleged history of road traffic accident admitted in our trauma center. On initial examination, his airway was patent, he was breathing at the rate of 22 breaths/min with air entry diminished over the right lung. Initial hemodynamics were stable with heart rate of 96 beats/min and blood pressure of 126/88 mmHg. Contrast-enhanced computed tomography scan chest revealed the fracture of 1st, 2nd, 3rd, and 7th ribs on the right side with hemopneumothorax and multifocal contusions in all lobes of the right lung. A right-sided intercostal tube drain (ICD) was placed. Pneumothorax and hemothorax resolved subsequently. He was shifted to the general ward. After 4 days of admission, patient developed acute respiratory distress with fall in oxygen saturation (90%) and was transferred to trauma intensive care unit (ICU). On initial evaluation, his chest X-ray showed [Figure 1] right lung collapsed with mediastinal shift toward the right side. A flexible bronchoscopy was contemplated in view of provisional diagnosis of mucus plug obstructing the major airways. A flexible bronchoscopy was carried out and a large mucus plug was aspirated from the right bronchus thereby clearing the airway. The patient was kept on positive pressure ventilation after the procedure. Immediately following the flexible bronchoscopy a large air leak became apparent in right-sided ICD. A follow-up chest X-ray showed a new large pneumothorax and collapse whole lung [Figure 2]. Ventilatory settings were adjusted to minimize the leak and the ICD was connected to negative pressure of 15 mmHg. A second ICD was inserted in order to control the leak and expand the lung. After 2 days, air leak controlled and lung got expanded. Patient was shifted to high dependency unit for further care. Figure 1 Chest X-ray showed collapsed right lung with mediastinal shift toward the right side Figure 2 Chest X-ray demonstrated a new large pneumothorax and collapse of whole the right lung Flexible fiberoptic bronchoscopy is a safe procedure carried out in patients admitted to ICUs. Its indication varies between diagnostic to therapeutic interventions including regular bronchoalveolar lavage for microbiological sampling, diagnosis of pulmonary hemorrhage, use in cases of difficult intubation, as a control in percutaneous tracheostomies, and aspirations of secretions.[2] Its use in clearing the airway because of mucus plug is considered as a standard practice particularly in patients where physiotherapy has failed to do so. However, its complications are infrequent. Most frequent complications cited in the literature are supraventricular tachycardia (3.8%), transient hypoxemia (6.7%), and slight bleeding of the bronchial mucosal membrane (2.4%).[2] Pneumothorax following flexible bronchoscopy has been reported infrequently in literature. Pue et al. have reported pneumothorax following flexible bronchoscopy in 0.16% of cases. Predominantly, it followed transbronchial biopsy procedure.[3] de Blic et al. analyzed prospectively in 1328 flexible bronchoscopy procedures in children and noted 0.1% incidence of pneumothorax.[4] In both the above analysis, none has reported pneumothorax following aspiration of secretion or mucus plug in case of chest injury following trauma. Moreover, flexible fiberoptic bronchoscopy was used here as a diagnostic modality to identify the cause of persistent pneumothorax and bronchial injuries. Mechanism that might have led to pneumothorax in our patient can be attributed to initial lung injury. Probably, the mucus plug had sealed the existent bronchial rent underlying lacerated lung and corrected the initial hemopneumothorax. As soon as the mucus plug got aspirated during flexible bronchoscopy the lung laceration got expose to high airway pressures and caused escaping of air into the pleural cavity. To conclude, although flexible bronchoscopy is a safe procedure, it mandates close monitoring during and after the procedure. It is important to have a high index of suspicion and a follow-up chest X-ray to identify a potentially dangerous complication.

Patient comfort during treatment with heated humidified high flow nasal cannulae versus nasal continuous positive airway pressure: a randomised cross-over trial

ObjectiveTo compare patient comfort in preterm infants treated with heated humidified high flow nasal cannulae (HHHFNC) versus nasal continuous positive airway pressure (NCPAP).DesignRandomised cross-over trial (2×24 h).SettingSingle tertiary neonatal unit.Patients20...

Tidal volume and airway pressure under percutaneous transtracheal ventilation without a jet ventilator: comparison of high-flow oxygen ventilation and manual ventilation in complete and incomplete upper airway obstruction models

Percutaneous transtracheal ventilation (PTV) can be life-saving in a cannot ventilate, cannot intubate situation. The aim of this study was to investigate the efficacy of PTV by measuring tidal volumes (VTs) and airway pressure (Paw) in high-flow oxygen ventilation and manual ventilation using a model lung. We examined 14G, 16G, 18G, and 20G intravenous catheters and minitracheotomy catheters. In high-flow oxygen ventilation, the flow was set to 10L/min, while the inspiratory:expiratory phases (I:E) were 1 s:4 s in the complete upper airway obstruction model and 1 s:1s in the incomplete obstruction model. In manual ventilation, I:E were 2 s:4s in the complete obstruction model and 2 s:3s in the incomplete obstruction model. We ventilated through each catheter for 2min and measured VT and Paw. In high-flow ventilation, the average VTs were approximately 150ml and <100ml with 14G catheters in complete and incomplete upper airway obstruction, respectively. The VTs obtained were reduced when the bore size was decreased. In manual ventilation, the average VTs were over 300ml and approximately 260ml with 14G catheters in complete and incomplete upper airway obstruction, respectively. In high-flow ventilation, the airway pressure tended to be higher. The minitracheotomy catheters produced over 800ml of VT and created almost no positive end-expiratory pressure. High-flow ventilation tends to result in higher airway pressure despite a smaller VT, which is probably due to a PEEP effect caused by high flow.

Prediction of Extubation Success in Myasthenic Crisis Using Bedside Functional Residual Capacity Measurement: A Prospective Feasibility Study

Address for Correspondence / Yaz›flma Adresi: Mehmet Akif Topcuoglu, MD, Department of Neurology, Faculty of Medicine, Hacettepe University, Ankara, Turkey Phone: +90 312 305 18 06 e.mail: mat@hacettepe.edu.tr doi:10.5152/dcbybd.2012.09 Aim: Extubation failure often complicates the recovery phase of a myasthenic crisis (MC). Bedside functional residual capacity (FRC) is a relatively new technique shown to be promising in the improvement of ventilation management in the intensive care unit (ICU), and may have a role in the estimation of extubation success. Since the prediction of extubation success is difficult due to the absence of formally evaluated disease-specific criteria, the appropriateness of any strategy described for non-neuromuscular conditions should be validated for specific neuromuscular diseases such as MC. In accordance, we designed a pilot study to determine the feasibility of bedside FRC measurement in the prediction of extubation success in MC and to determine its yield when added to the conventional parameters. Material and Methods: We prospectively studied the additive value of bedside FRC measurements to predict extubation outcome in 11 MC episodes. The area under the receiver operating characteristic curve (ROC AUC), sensitivity and specificity of all weaning and extubation indices that passed exploratory analysis were determined. Results: The frequency of extubation failure, defined as the need for reinstitution of ventilatory support within 72 hours of planned endotracheal tube removal, was 55% in this study population, in which all patients met the standard weaning indices indicating safety of extubation. The risk of extubation failure was connected to higher airway pressures (peak inspiratory and plato pressures; PIP and Pplato; ROC AUCs: 0.933 and 0.917), increased gradient of end-tidal CO2 to arterial CO2 (CO2 gradient; ROC AUC:0.900) and total airway care score (ACS; ROC AUC:0.983), but not to FRC, the simplified acute physiology score (SAPS-II) and the traditional weaning criteria such as the rapid shallow breathing index (RSBI) and mouth occlusion pressure (P0.1). Although perhaps useful when measurable, the utility of maximal inspiratory/expiratory mouth pressures (MIP and MEP) was also low due to the inability of MC patients to perform the maneuvers required to obtain these parameters. In contrast, FRC measurement was easily attainable at the bedside, with zero risk to the patient and correlated well to the aerated lung volume measured by chest CT (r=0.717). Conclusion: This preliminary study suggests that bedside FRC measurement is safe and feasible for long-term monitoring of intubated myasthenic patients. Its utility in determining weaning and extubation outcomes requires further studies with larger samples. Standard weaning parameters may not be accurate enough in the prediction of extubation outcome in MC, probably reflecting differences in the pathophysiology of failure of extubation and weaning. As a new semi-objective measurement of pulmonary secretion status, ACS can be helpful in the identification of the risk of extubation failure. (Yogun Bakim Derg 2012; 3: 36-42)

Resuscitation with mechanical ventilation: The effects of Chest Compression Synchronized Ventilation (CCSV) or Intermitted Positive Pressure Ventilation (IPPV) on lung injury in a pig model

Objective: Positive pressure ventilation may cause lung injury that might be accelerated by high peak airway pressures as during chest compressions. We investigated the effects of the novel ventilator mode CCSV1 compared with IPPV2 on lung injury following resuscitation and return of spontaneous circulation (ROSC) in a pig model.

Is Time the Missing Component in Protective Ventilation Strategies?*

Is Time the Missing Component in Protective Ventilation Strategies?*

Influences of pleural effusion on respiratory mechanics, gas exchange, hemodynamics, and recruitment effects in acute respiratory distress syndrome

BackgroundAcute lung injury and acute respiratory distress syndrome (ALI/ARDS) cause substantial morbidity and mortality despite improvements in the understanding of lung injury and advances in treatment. Recruitment maneuver (RM) with high sustained airway pressures is proposed as an adjunct to mechanical ventilation to maintain alveolar patency. In addition, RM has been advocated to improve pulmonary gas exchange. However, many factors may influence responses to RM and the effect of pleural effusion (PLE) is unknown. MethodThere were four groups in this study (n = 6 in each group). Group A was the control group, group B was the PLE group, group C was ARDS with RM, and group D was ARDS with PLE and RM. RM was performed in groups C and D, consisting of a peak pressure of 45 cm H2O with positive end-expiratory pressure of 35 cm H2O sustained for 1 min. Arterial blood gas, systemic and pulmonary hemodynamics, lung water, and respiratory mechanics were measured throughout. ResultAfter the induction of ALI/ARDS, there were significant decreases in partial pressure of oxygen in arterial blood, mean arterial pressure, systemic vascular resistance, and lung compliance. There were also significant increases in the alveolar–arterial O2 tension difference, partial pressure of arterial carbon dioxide, mean pulmonary arterial pressure, pulmonary vascular resistance, and lung water. The RM improved oxygenation, which was attenuated by PLE. ConclusionsALI/ARDS leads to poor oxygenation and hemodynamics. RM results in improved oxygenation, but this improvement is attenuated by PLE.

Acute cor pulmonale in ARDS

Acute cor pulmonale in ARDS