Peak Inspiratory Airway Pressure Research Articles

Lung tissue injury and hemodynamic effects of ventilations synchronized or unsynchronized to continuous chest compressions in a porcine cardiac arrest model

AimCompare lung injury and hemodynamic effects in synchronized ventilations (between two chest compressions) vs. unsynchronized ventilations during cardiopulmonary resuscitation (CPR) in a porcine model of cardiac arrest. MethodsTwenty pigs were randomized to either synchronized or unsynchronized group. Ventricular fibrillation was induced electrically and left for 1.5 minutes. Four minutes of basic chest compression:ventilation (30:2) CPR was followed by eight minutes of either synchronized or unsynchronized ventilations (10/min) during continuous compressions before defibrillation was attempted. Aortic, right atrial and intracerebral pressures, carotid and cerebral blood flow and cardiac output were measured. Airway monitoring included capnography and respiratory function monitor. Macro- and microscopic lung injuries were assessed post-mortem. ResultsThere were no significant differences between groups in any of the measured hemodynamic variables or inspiration time (0.4 vs. 1.0 s, p = 0.05). The synchronized ventilation group had lower median peak inspiratory airway pressure (57 vs. 94 cm H2O, p < 0.001), lower minute ventilation (3.7 vs. 9.4 l min−1, p < 0.001), lower pH (7.31 vs. 7.53, p < 0.001), higher pCO2 (5.2 vs. 2.5 kPa, p < 0.001) and lower pO2 (31.6 vs. 54.7 kPa, p < 0.001) compared to the unsynchronized group after 12 minutes of CPR. There was significant lung injury after CPR in both synchronized and unsynchronized groups. ConclusionSynchronized and unsynchronized ventilations resulted in similar hemodynamics and lung injury during continuous mechanical compressions of pigs in cardiac arrest. Animals that received unsynchronized ventilations with one second inspiration time at a rate of ten ventilations per minute were hyperventilated and hyperoxygenated.Institutional protocol number: FOTS, id 6948.

Особливості респіраторної терапії пацієнтів з ожирінням при лапароскопічних операціях

У цьому клінічному дослідженні ми вивчали респіраторні властивості легень 40 пацієнтів із різним ступенем ожиріння під час лапароскопічних операцій. Усі пацієнти були розподілені на 4 групи: три контрольні групи (1-ша група — пацієнти без ожиріння або з надмірною вагою, 2-га група — пацієнти з 1-м та 2-м ступенем ожиріння, 3-тя група — пацієнти з морбідним ожирінням) і одну основну (4-та група — пацієнти з 1-м і 2-м ступенем ожиріння, яким застосовувалась передопераційна неінвазивна CPAP-терапія (Continues Positive Airway Pressure — постійний позитивний тиск у дихальних шляхах), а параметри штучної вентиляції були оптимізовані шляхом зміни рівня позитивного тиску в кінці видиху (ПТКВ) і застосування рекрутмент-маневру). Досліджувались такі респіраторні властивості легень: статичний комплайєнс, середній динамічний комплайєнс, загальний опір дихальних шляхів, піковий тиск вдиху й тиск плато, середній внутрішньогрудний тиск. Усі ці параметри визначалися під час загальної анестезії у встановлених контрольних точках: 1-ша контрольна точка — після інтубації; 2-га контрольна точка — після підвищення внутрішньочеревного тиску до 15 мм рт.ст.; 3-тя контрольна точка — після зменшення внутрішньочеревного тиску до 10 мм рт.ст.; 4-та контрольна точка — після нормалізації рівня внутрішньочеревного тиску. В основній групі додатково визначали ці параметри після зміни рівня ПТКВ та рекрутменту. Застосування передопераційної неінвазивної CPAP-терапії та підвищеного інтраопераційного рівня ПТКВ покращує респіраторні властивості легень, особливо в пацієнтів з ожирінням і тяжкою супутньою легеневою патологією на фоні підвищеного внутрішньочеревного тиску. Внутрішньочеревний тиск на рівні 15 мм рт.ст., що часто застосовується при лапароскопічних операціях, негативно впливає на респіраторну механіку. ПТКВ на рівні 5 см вод.ст. недостатній для підтримання «відкритих легень» у пацієнтів з ожирінням при внутрішньочеревній гіпертензії. Неінвазивна CPAP-терапія та ПТКВ на рівні 10 см вод.ст. дозволяє втримати задовільну розтяжність легень, знизити загальний опір дихальних шляхів, зменшити та провести профілактику ателектазування легень і, можливо, у подальшому скоротити час відлучення від ШВЛ.

Effects of deep neuromuscular block with low-pressure pneumoperitoneum on respiratory mechanics and biotrauma in a steep Trendelenburg position

We hypothesized that deep neuromuscular blockade (NMB) with low-pressure pneumoperitoneum (PP) would improve respiratory mechanics and reduce biotrauma compared to moderate NMB with high-pressure PP in a steep Trendelenburg position. Seventy-four women undergoing robotic gynecologic surgery were randomly assigned to two equal groups. Moderate NMB group was maintained with a train of four count of 1–2 and PP at 12 mmHg. Deep NMB group was maintained with a post-tetanic count of 1–2 and PP at 8 mmHg. Inflammatory cytokines were measured at baseline, at the end of PP, and 24 h after surgery. Interleukin-6 increased significantly from baseline at the end of PP and 24 h after the surgery in moderate NMB group but not in deep NMB group (Pgroup*time = 0.036). The peak inspiratory, driving, and mean airway pressures were significantly higher in moderate NMB group than in deep NMB group at 15 min and 60 min after PP (Pgroup*time = 0.002, 0.003, and 0.048, respectively). In conclusion, deep NMB with low-pressure PP significantly suppressed the increase in interleukin-6 developed after PP, by significantly improving the respiratory mechanics compared to moderate NMB with high-pressure PP during robotic surgery.

Changes in peak inspiratory flow rate and peak airway pressure with endotracheal tube size during chest compression.

Adequate airway management plays an important role in high-quality cardiopulmonary resuscitation (CPR). Airway management is usually performed using an endotracheal tube (ETT) during CPR. However, no study has assessed the effect of ETT size on the flow rate and airway pressure during CPR. We measured changes in peak inspiratory flow rate (PIFR), peak airway pressure (Ppeak), and mean airway pressure (Pmean) according to changes in ETT size (internal diameter 6.0, 7.0, and 8.0 mm) and with or without CPR. A tidal volume of 500 mL was supplied at a rate of 10 times per minute using a mechanical ventilator. Chest compressions were maintained at a constant compression depth and speed using a mechanical chest compression device (LUCAS2, mode: active continuous, chest compression rate: 102±2/minute, chest compression depth 2-2.5 inches). The median of several respiratory physiological parameters during CPR was significantly different according to the diameter of each ETT (6.0 vs. 8.0 mm): PIFR (32.1 L/min [30.5-35.3] vs. 28.9 L/min [27.5-30.8], P<0.001), Ppeak (48.84 cmH2O [27.46-52.11] vs. 27.45 cmH2O [22.53-52.57], P<0.001), and Pmean (18.34 cmH2O [14.61-21.66] vs.13.66 cmH2O [8.41-19.24], P<0.001). The changes in PIFR, Ppeak, and Pmean were related to the internal diameter of ETT, and these values tended to decrease with an increase in ETT size. Higher airway pressures were measured in the CPR group than in the no CPR group.

Comparison of Operating Conditions, Postoperative Pain and Recovery, and Overall Satisfaction of Surgeons with Deep vs. No Neuromuscular Blockade for Spinal Surgery under General Anesthesia: A Prospective Randomized Controlled Trial.

We aimed to investigate operating conditions, postoperative pain, and overall satisfaction of surgeons using deep neuromuscular blockade (NMB) vs. no NMB in patients undergoing lumbar spinal surgery under general anesthesia. Eighty-three patients undergoing lumbar fusion were randomly assigned to receive deep NMB (n = 43) or no NMB (n = 40). In the deep-NMB group, rocuronium was administered to maintain deep NMB (train-of-four count 0, post-tetanic count 1–2) until the end of surgery. In the no-NMB group, sugammadex 4 mg/kg at train-of-four (TOF) count 0–1 or sugammadex 2 mg/kg at TOF count ≥2 was administered to reverse the NMB 10 min after placing the patient prone. Peak inspiratory airway pressure, plateau airway pressure, lumbar retractor pressure significantly were lower in the deep-NMB group. Degree of surgical field bleeding (0–5), muscle tone (1–3), and satisfaction (1–10) rated by the surgeon were all superior in the deep-NMB group. Pain scores, rescue fentanyl consumption in post-anesthesia care unit (PACU), and postoperative patient-controlled analgesia consumption were significantly lower in the deep-NMB group, and this group had a shorter length of stay in PACU. Compared to no NMB, deep NMB provides better operating conditions, reduced postoperative pain and higher overall satisfaction in lumbar spinal surgery.

Work of breathing for cuffed and uncuffed pediatric endotracheal tubes in an invitro lung model setting.

Over the last decade, cuffed endotracheal tubes are increasingly used in pediatric anesthesia and also in pediatric intensive care. However, the smaller inner diameter of cuffed endotracheal tubes and, implicitly, the increased endotracheal tube resistance is still a matter of debate. This invitro study investigated work of breathing and inspiratory airway pressures in cuffed and uncuffed endotracheal tubes and the impact of pressure support ventilation and automatic tube compensation. In 5 simulated neonatal and pediatric lung models, the Active Servo Lung 5000 and an intensive care ventilator were used to quantify the differences in work of breathing under spontaneous breathing (with and without pressure support ventilation and automatic tube compensation) between cuffed and uncuffed endotracheal tubes. Additionally, differences in inspiratory airway pressures, measured either proximal or distal of the endotracheal tube, between cuffed and uncuffed endotracheal tubes under mechanical ventilation were investigated. Work of breathing was overall 10.27% [95% confidence interval 9.01-11.94] higher with cuffed than with uncuffed endotracheal tubes and was dramatically reduced by 34.19% [95% confidence interval 31.61-35.25] with the application of pressure support. Automatic tube compensation almost diminished work of breathing differences between the 2 endotracheal tube types in nearly all pediatric lung models. Peak inspiratory and mean airway pressures measured at the proximal endotracheal tube end revealed significantly higher values in cuffed than in uncuffed endotracheal tubes. However, these differences measured at the distal end of the endotracheal tube became minimal. This invitro study confirmed significant differences in work of breathing and inspiratory pressures between cuffed and uncuffed endotracheal tubes. Work of breathing, however, is almost neutralized by pressure support ventilation with automatic tube compensation and distal inspiratory airway pressures that, from a clinical perspective, are not significantly increased.

Pressure-controlled versus volume-controlled ventilation during one-lung ventilation for video-assisted thoracoscopic lobectomy.

It is controversial as to which ventilation mode is better during one-lung ventilation (OLV). This study was designed to figure out whether there was any difference between volume controlled ventilation (VCV) and pressure controlled ventilation (PCV) on oxygenation and postoperative complications under the condition of protective ventilation (PV). Sixty-five patients undergoing video-assisted thoracoscopic lobectomy were randomized into two groups. Patients in group V received VCV mode during OLV while patients in group P received PCV. The tidal volume (VT) in both groups was 6 mL per predicted body weight (PBW). Positive end-expiratory pressure (PEEP) was set at the level of 5 cmH2O in both groups. Arterial gas analysis were performed preoperatively with room air (T0), at 15 mins (T1) and 1 h (T2) after OLV, at the end of OLV (T3), 30 min after PACU admission (T4), 24 h after surgery (post-operative day 1, POD1) and 48 h after surgery (post-operative day 2, POD2). Peak inspiratory airway pressure (Ppeak) and plateau airway pressure (Pplat) were recorded at T1, T2 and T3. The perioperative complications were also recorded. Sixty-four patients completed this study. Ppeak in group V was significantly higher than that in group P (T1 22.3±2.9 vs. 18.7±2.1 cmH2O; T2 22.2±2.8 vs. 18.7±2.6 cmH2O). There were no differences with Pplat and intraoperative oxygenation index (T1 203.3±109.7 vs. 198.1±93.4; T2 216.8±79.1 vs. 232.1±101.4). The postoperative oxygenation index (T4 525.0±160.9 vs. 520.7±127.1, post-operative day 1 (POD1) 452.1±161.3 vs. 446.1±109.1; post-operative day 2 (POD2) 403.8±93.4 vs. 396.7±92.8) and postoperative complications were also comparable between these two groups. When they were utilized during OLV, PCV and VCV had the same performance on the intraoperative oxygenation and postoperative complications under the condition of PV.

Abstract 19325: Hemodynamic Effects of Guideline-compliant Asynchronous vs. Synchronous Ventilations During Cardiopulmonary Resuscitation in a Porcine Model

Background: Current guidelines for cardiopulmonary resuscitation (CPR) emphasize reducing pauses in chest compressions, and suggest ventilating with 1 second inspiration time and with enough volume to produce normal chest rise 10 times per minute. No specific advice is provided on how ventilations should be timed with ongoing chest compressions. We have compared hemodynamic effects of ventilating synchronously vs. asynchronously during chest compressions in a porcine model. Methods: Twenty anaesthetized domestic pigs (approx. 30 kg) were randomized into two groups; synchronous vs. asynchronous ventilation. Ventricular fibrillation is induced electrically and left for 2 minutes before initiation of basic 30:2 CPR for 4 minutes. CPR with continuous mechanical chest compressions was continued for another 8 minutes with either synchronous or asynchronous ventilation before defibrillation was attempted. Aortic, right atrial and intracerebral pressures, carotid and cerebral blood flow and cardiac output (thermodilution) were measured. Airway monitoring included capnography and spirometry. Results: Hemodynamics, blood gas analysis and airway pressures were similar for both groups during baseline and 30:2 CPR periods. The asynchronous group had higher median peak inspiratory airway pressure (94 vs. 57 cm H 2 O, p&lt;0.001) and lower EtCO 2 (1.8 vs. 3.5 kPa, p=0.023) compared to synchronous group during the last 30 seconds of CPR (after 12 minutes). Asynchronous group also had higher pH (7.55 vs. 7.35, p&lt;0.001), lower pCO 2 (2.4 vs. 4.7, p&lt;0.001) and higher pO 2 (62.1 vs. 29.4, p&lt;0.001) compared to synchronous group. There were no significant differences in any of the measured hemodynamic variables between the two groups with similar coronary and cerebral perfusion pressures. ROSC was achieved in 5/10 vs. 3/10 animals in the synchronous and asynchronous groups, respectively. Conclusion: Synchronous and asynchronous ventilation during mechanical chest compressions provide similar hemodynamics, but guideline-compliant asynchronous ventilation yields significantly higher airway pressures and hyperventilation. Implications for lung injury need to be assessed.

Inhibition of Nitro-Oxidative Stress Attenuates Pulmonary and Systemic Injury Induced by High-Tidal Volume Mechanical Ventilation.

Mechanisms contributing to pulmonary and systemic injury induced by high tidal volume (VT) mechanical ventilation are not well known. We tested the hypothesis that increased peroxynitrite formation is involved in organ injury and dysfunction induced by mechanical ventilation. Male Sprague-Dawley rats were subject to low- (VT, 9 mL/kg; positive end-expiratory pressure, 5 cmH2O) or high- (VT, 25 mL/kg; positive end-expiratory pressure, 0 cmH2O) VT mechanical ventilation for 120 min, and received 1 of 3 treatments: 3-aminobenzamide (3-AB, 10 mg/kg, intravenous, a poly adenosine diphosphate ribose polymerase [PARP] inhibitor), or the metalloporphyrin manganese(III) tetrakis(1-methyl-4-pyridyl)porphyrin (MnTMPyP, 5 mg/kg intravenous, a peroxynitrite scavenger), or no treatment (control group), 30 min before starting the mechanical ventilation protocol (n = 8 per group, 6 treatment groups). We measured mean arterial pressure, peak inspiratory airway pressure, blood chemistry, and gas exchange. Oxidation (fluorescence for oxidized dihydroethidium), protein nitration (immunofluorescence and Western blot for 3-nitrotyrosine), PARP protein (Western blot) and gene expression of the nitric oxide (NO) synthase (NOS) isoforms (quantitative real-time reverse transcription polymerase chain reaction) were measured in lung and vascular tissue. Lung injury was quantified by light microscopy. High-VT mechanical ventilation was associated with hypotension, increased peak inspiratory airway pressure, worsened oxygenation; oxidation and protein nitration in lung and aortic tissue; increased PARP protein in lung; up-regulation of NOS isoforms in lung tissue; signs of diffuse alveolar damage at histological examination. Treatment with 3AB or MnTMPyP attenuated the high-VT mechanical ventilation-induced changes in pulmonary and cardiovascular function; down-regulated the expression of NOS1, NOS2, and NOS3; decreased oxidation and nitration in lung and aortic tissue; and attenuated histological changes. Increased peroxynitrite formation is involved in mechanical ventilation-induced pulmonary and vascular dysfunction.

Airway Pressures as Surrogate Estimates of Intra-abdominal Pressure

Intra-abdominal pressure (IAP) measurements are essential to the diagnosis and management of patients with intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS). Peak inspiratory pressure (PIP), plateau pressure (Pplat), and mean airway pressure (Paw) are used by some surgeons as surrogate estimates of IAP during abdominal closure. Thirty mechanically ventilated surgical/trauma patients with risk factors for IAH/ACS underwent simultaneous triplicate measurements of PIP, Pplat, Paw, and IAP. PIP, Pplat, and Paw were compared with IAP using both coefficient of determination and Bland and Altman analysis. The coefficient of determination for each airway pressure in predicting change in IAP was: PIP 5 per cent (P = 0.24), Pplat 17 per cent (P = 0.02), and Paw 15 per cent (P = 0.03). Bland and Altman analysis identified that marked variability exists between airway pressure and IAP measurements: PIP 19.3 ± 18.7 mmHg, Pplat 11.1 ± 13.7 mmHg, and Paw 2.0 ± 9.8 mmHg. Airway pressures do not accurately reflect IAP and cannot be substituted for IAP measurements in patients at risk for IAH/ACS.

Effects of continuous rate infusion of butorphanol in isoflurane-anesthetized calves.

To assess the hemodynamic changes and bispectral index (BIS) following administration of a continuous rate infusion (CRI) of butorphanol in isoflurane-anesthetized calves. Eight calves weighing 110 ± 12 kg were included in the study. Anesthesia was induced with 5% isoflurane in O2 delivered via face mask and maintained with end-tidal concentration of 1.4%. IPPV was set to a peak inspiratory airway pressure of 15 cmH2O and respiratory rate of six breaths minute-1. Forty minutes after the start of anesthetic maintenance, 0.1 mg kg-1butorphanol was administered intravenously, followed by a CRI of 20 µg kg-1 minute-1. Hemodynamic variables and BIS were recorded before butorphanol administration (T0), and at 10, 20, 40 and 80 minutes following the CRI. Anesthesia was discontinued after the last recording and the calves were allowed to recover. The time to sternal recumbency (SRE) and standing (ST) were evaluated. There were no significant differences between the moments in all hemodynamic variables and BIS. The time to SRE and ST was 9 ± 5 and 14 ± 7 minutes, respectively. The continuous rate infusion did not produce clinically relevant changes in hemodynamic or bispectral index values compared to baseline in mechanically ventilated and unstimulated calves anesthetized at 1.4% isoflurane.

Evaluation of Manual and Automatic Manually Triggered Ventilation Performance and Ergonomics Using a Simulation Model

In the absence of endotracheal intubation, the manual bag-valve-mask (BVM) is the most frequently used ventilation technique during resuscitation. The efficiency of other devices has been poorly studied. The bench-test study described here was designed to evaluate the effectiveness of an automatic, manually triggered system, and to compare it with manual BVM ventilation. A respiratory system bench model was assembled using a lung simulator connected to a manikin to simulate a patient with unprotected airways. Fifty health-care providers from different professional groups (emergency physicians, residents, advanced paramedics, nurses, and paramedics; n = 10 per group) evaluated manual BVM ventilation, and compared it with an automatic manually triggered device (EasyCPR). Three pathological situations were simulated (restrictive, obstructive, normal). Standard ventilation parameters were recorded; the ergonomics of the system were assessed by the health-care professionals using a standard numerical scale once the recordings were completed. The tidal volume fell within the standard range (400-600 mL) for 25.6% of breaths (0.6-45 breaths) using manual BVM ventilation, and for 28.6% of breaths (0.3-80 breaths) using the automatic manually triggered device (EasyCPR) (P < .0002). Peak inspiratory airway pressure was lower using the automatic manually triggered device (EasyCPR) (10.6 ± 5 vs 15.9 ± 10 cm H2O, P < .001). The ventilation rate fell consistently within the guidelines, in the case of the automatic manually triggered device (EasyCPR) only (10.3 ± 2 vs 17.6 ± 6, P < .001). Significant pulmonary overdistention was observed when using the manual BVM device during the normal and obstructive sequences. The nurses and paramedics considered the ergonomics of the automatic manually triggered device (EasyCPR) to be better than those of the manual device. The use of an automatic manually triggered device may improve ventilation efficiency and decrease the risk of pulmonary overdistention, while decreasing the ventilation rate.

Ventilatory strategies in septic patients

Mortality in intensive care unit (ICU) patients is affected by multiple variables. The possible impact of the mode of ventilation has not yet been clarified; therefore, a secondary analysis of the "epidemiology of sepsis in Germany" study was performed. The aims were (1) to describe the ventilation strategies currently applied in clinical practice, (2) to analyze the association of the different modes of ventilation with mortality and (3) to investigate whether the ratio between arterial partial pressure of oxygen and inspired fraction of oxygen (PF ratio) and/or other respiratory variables are associated with mortality in septic patients needing ventilatory support. A total of 454 ICUs in 310 randomly selected hospitals participated in this national prospective observational 1-day point prevalence of sepsis study including 415 patients with severe sepsis or septic shock according to the American College of Chest Physicians/Society of Critical Care Medicine criteria. Of the 415 patients, 331 required ventilatory support. Pressure controlled ventilation (PCV) was the most frequently used ventilatory mode (70.6 %) followed by assisted ventilation (AV 21.7 %) and volume controlled ventilation (VCV 7.7 %). Hospital mortality did not differ significantly among patients ventilated with PCV (57 %), VCV (71 %) or AV (51 %, p=0.23). A PF ratio equal or less than 300 mmHg was found in 83.2 % of invasively ventilated patients (n=316). In AV patients there was a clear trend to a higher PF ratio (204±70 mmHg) than in controlled ventilated patients (PCV 179±74 mmHg, VCV 175±75 mmHg, p=0.0551). Multiple regression analysis identified the tidal volume to pressure ratio (tidal volume divided by peak inspiratory airway pressure, odds ratio OR=0.94, 95 % confidence interval 95% CI=0.89-0.99), acute renal failure (OR=2.15, 95% CI=1.01-4.55) and acute physiology and chronic health evaluation (APACHE) II score (OR=1.09, 95% CI=1.03-1.15) but not the PF ratio (univariate analysis OR=0.998, 95 % CI=0.995-1.001) as independent risk factors for in-hospital mortality. This representative survey revealed that severe sepsis or septic shock was frequently associated with acute lung injury. Different ventilatory modes did not affect mortality. The tidal volume to inspiratory pressure ratio but not the PF ratio was independently associated with mortality.

Do lower cuff pressures reduce damage to the tracheal mucosa? A scanning electron microscopy study in neonatal pigs

Modern high volume-low pressure (HVLP) endotracheal tubes (ETT) cuffs can seal the trachea using baseline cuff pressures (CP) lower than peak inspiratory airway pressures (PIP). The aim of the study was to determine whether this technique reduces the damage to the tracheal mucosa compared to constant CP of 20 cmH(2)O. Eighteen piglets were intubated with an ID 4.0 mm HVLP cuffed ETT (Microcuff PET) and artificially ventilated with 20 cmH(2)O PIP and 5 cmH(2)O PEEP. Animals were randomly allocated to two groups of CP: group A (just seal; n = 9) and group B (20 cmH(2)O; n = 9), controlled constantly with a manometer during the following 4-h study period under sevoflurane anesthesia. After euthanasia, cuff position was marked in situ. Damage in the cuff region was evaluated with scanning electron microscopy (SEM) examination by grading of mucosal damage and by estimating percentage of intact mucosal area both by a blinded observer. Maximal CP to seal the trachea in group A ranged from 12 to 18 cmH(2)O (median: 14 cmH(2)O). Using a mixed effects model approach, the estimated mean effect of group B vs group A was an increase of 17.9% (SE 8.1%) higher proportion of pictures with an area of at least 5% intact mucosa (P = 0.042). Minimal sealing pressures with cyclic pressure changes from CP did not result in decreased damage to the tracheal mucosa compared to constant CP of 20 cmH(2)O in this short-term animal trial.

Comparison of Respiratory Mechanics in Adult Patients Undergoing Minimally Invasive Repair of the Pectus Excavatum and Removal of a Pectus Bar

The objective of this study was to compare the respiratory mechanics and gas exchange in adult patients undergoing minimally invasive repair of the pectus excavatum (MIRPE group) and removal of a pectus bar (bar removal group). A prospective observational study. A tertiary university hospital. Thirty-two patients scheduled for elective MIRPE or removal of a pectus bar. None. Spirometry was used to measure the peak inspiratory airway pressure (PIP), static compliance, and respiratory resistance. The measurements were recorded at 1 minute after beginning mechanical ventilation (T0), 15 minutes after beginning sevoflurane inhalation (T1), and after the insertion (or removal) of a pectus bar through the chest wall (T2). Pulmonary gas exchange was assessed by calculating the alveolar arterial oxygen tension difference (AaDO2) before surgical incision and after insertion (or removal) of the pectus bar. In the MIRPE group, static compliance was decreased significantly (p < 0.001), and PIP was increased significantly (p < 0.001) after insertion of the pectus bar (T2) compared with baseline. In contrast, the bar removal group showed the opposite results. There were significant differences in static compliance and PIP at T2 between the groups (p = 0.002 and 0.026, respectively). AaDO2 was increased significantly in the MIRPE group compared with the bar removal group (p = 0.012). Insertion of the pectus bar through the chest wall results in significant changes in respiratory mechanics and gas exchange. Therefore, close attention to pulmonary function is required during and after these surgical procedures.

A pilot prospective study on closed loop controlled ventilation and oxygenation in ventilated children during the weaning phase

IntroductionThe present study is a pilot prospective safety evaluation of a new closed loop computerised protocol on ventilation and oxygenation in stable, spontaneously breathing children weighing more than 7 kg, during the weaning phase of mechanical ventilation.MethodsMechanically ventilated children ready to start the weaning process were ventilated for five periods of 60 minutes in the following order: pressure support ventilation, adaptive support ventilation (ASV), ASV plus a ventilation controller (ASV-CO2), ASV-CO2 plus an oxygenation controller (ASV-CO2-O2) and pressure support ventilation again. Based on breath-by-breath analysis, the percentage of time with normal ventilation as defined by a respiratory rate between 10 and 40 breaths/minute, tidal volume > 5 ml/kg predicted body weight and end-tidal CO2 between 25 and 55 mmHg was determined. The number of manipulations and changes on the ventilator were also recorded.ResultsFifteen children, median aged 45 months, were investigated. No adverse event and no premature protocol termination were reported. ASV-CO2 and ASV-CO2-O2 kept the patients within normal ventilation for, respectively, 94% (91 to 96%) and 94% (87 to 96%) of the time. The tidal volume, respiratory rate, peak inspiratory airway pressure and minute ventilation were equivalent for all modalities, although there were more automatic setting changes in ASV-CO2 and ASV-CO2-O2. Positive end-expiratory pressure modifications by ASV-CO2-O2 require further investigation.ConclusionOver the short study period and in this specific population, ASV-CO2 and ASV-CO2-O2 were safe and kept the patient under normal ventilation most of the time. Further research is needed, especially for positive end-expiratory pressure modifications by ASV-CO2-O2.Trial registrationClinicalTrials.gov: NCT01095406

P267 Association of the length of non-invasive ventilation (NIV) with arterial bicarbonate level in COPD patients with acute hypercapnic respiratory failure (AHRF)

IntroductionFollowing the British Thoracic Society (BTS) NIV audit 2011 we noted that our institution's length of stay was longer than the national average. Factors related to length of stay are...

SLIPA™ may be more useful than other LMADs for difficult airway management

To the Editor, The SLIPA, a cuffless, hollow, boot-shaped, soft plastic supraglottic airway device (SLIPA; SLIPA Medical Ltd., London, UK), has advantages over other laryngeal mask airway devices (LMADs) because it provides better protection from regurgitation and has a better perilaryngeal seal. However, SLIPA has not been tested in difficult airways. We report successful management of a difficult airway with SLIPA after laryngeal mask airway failure. We obtained the patient’s written consent to publish this report. A 50-yr-old man (169 cm, 90 kg) with gastroesophageal reflux disease (GERD) was scheduled for reconstruction of finger tendons under general anesthesia. Difficult intubation was anticipated because of the patient’s large tongue, short neck, thyromental distance, and a Mallampati score of 4. Because he refused awake fibreoptic intubation, we decided to insert a LMAD. After administering fentanyl 100 lg, thiopental sodium 450 mg, and succinylcholine 90 mg, a LMAD (Solus; Intersurgical Ltd. Wokingham, UK) size 5 was inserted. Immediately after insertion, no leak was heard, the end-tidal carbon dioxide concentration (ETCO2) was 28-30 mmHg, and the peak inspiratory airway pressure (PIP) was 22-25 cm H2O. At one minute after insertion, however, the PIP suddenly increased to 35 cmH2O, and a leak was detected. The LMAD was removed, and another insertion attempt was made after administering succinylcholine 50 mg. This time, the PIP was 40-45 cm H2O, and leaks were audible immediately. A fibreoptic bronchoscope (FOB) was inserted through the airway port of the LMAD, and the anterior portion of the epiglottis was found to be blocking the view. The fibrescope was passed under the epiglottis to examine the glottis, and a glottic narrowing was found. After removing the LMAD, a size 55 SLIPA was inserted. The PIP decreased to 20-23 cm H2O, and the ETCO2 was 32-33 mmHg. No leak was detected. The FOB was inserted, through which the vocal cords were well visualized, and the periglottic seal was seen to be improved. Afterward, ventilation was maintained well, and there were no complications, including airway obstruction or aspiration. Examination of the glottis via the FOB provided possible explanations for the different performances of the two devices. First, the position of the epiglottis was different, which might be due to the designs of the respective bowls. The laryngeal aperture of SLIPA consists of a wide portion and a narrow portion, preventing airway obstruction (Figure), whereas the absence of epiglottic bars on the Solus could cause epiglottis downfolding and subsequent airway obstruction. However, previous reports suggested that because disposable LMADs, including the Solus, have a deeper bowl, ventilation is well maintained despite the absence of epiglottic bars. In this case, the FOB passed under the epiglottis with ease, which makes obstruction by the epiglottis improbable. Second, the presence of a cuff and the shape and location of the bowl should be considered. The space between the tongue and posterior pharyngeal wall was probably narrow in this patient, becoming narrower because of laryngopharyngeal edema caused by GERD. In a narrow space, inflating the LMAD cuff could increase pressure in the laryngopharynx and cause distortion of laryngeal B. G. Lim, MD K. J. Kim, MD M. H. Kong, MD, PhD N. S. Kim, MD, PhD S. H. Lim, MD, PhD M. K. Lee, MD, PhD I. O. Lee, MD, PhD (&) Guro Hospital, College of Medicine, Korea University, Seoul, South Korea e-mail: iloklee@korea.ac.kr

Effectiveness of Breathing through Nasal and Oral Routes in Unconscious Apneic Adult Human Subjects

The authors hypothesized that mouth ventilation by a resuscitator via the nasal route ensures a more patent airway and more effective ventilation than does ventilation via the oral route and therefore would be the optimal manner to ventilate adult patients in emergencies, such as during cardiopulmonary resuscitation. They tested the hypothesis by comparing the effectiveness of mouth-to-nose breathing (MNB) and mouth-to-mouth breathing (MMB) in anesthetized, apneic, adult subjects without muscle paralysis. Twenty subjects under general anesthesia randomly received MMB and MNB with their heads placed first in a neutral position and then an extended position. A single operator performed MNB and MMB at the target breathing rate of 10 breaths/min, inspiratory:expiratory ratio 1:2 and peak inspiratory airway pressure 24 cm H₂O. A plethysmograph was used to measure the amplitude change during MMB and MNB. The inspiratory and expiratory tidal volumes during MMB and MNB were calculated retrospectively using the calibration curve. All data are presented as medians (interquartile ranges). The rates of effective ventilation (expired volume > estimated anatomic dead space) during MNB and MMB were 91.1% (42.4-100%) and 43.1% (42.5-100%) (P < 0.001), and expired tidal volume with MMB 130.5 ml (44.0-372.8 ml) was significantly lower than with MNB 324.5 ml (140.8-509.0 ml), regardless of the head position (P < 0.001). Direct mouth ventilation delivered exclusively via the nose is significantly more effective than that delivered via the mouth in anesthetized, apneic adult subjects without muscle paralysis. Additional studies are needed to establish whether using this breathing technique during emergency situations will improve patient outcomes.

Comparison of ventilatory effects between three-way laryngeal mask airway and tracheal catheter on patients during bronchoalveolar lavage

Objective To compare the ventilatory effects between three-way laryngeal mask airway (TLMA)and tracheal catheter (TC) on hemodynamics, respiratory function and stress responses on patients during bronchoalveolar lavage (BAL). Method Forty patients scheduled for BAL under general anesthesia were divided (stratified sampling) into either TLMA group (group T,n = 20) or TC group (group C, n = 20) according to the stratified sampling principle. SpO2, SBP, DBP and HR were measured in 5 min after entering the operating theater (To), just before inserting TLMA or TC(T1), immediately after inserting TLMA or TC(T2) ,3 min(T3), 5 min(T4), 10 min(T5)after mechanical ventilation, 10 min(T6),20 min(T7), 30 min(T8)during the course of BAL,immediately after extubating TLMA or TC (T9)and 3 min after extubating TLMA or TC (T10). The tidal volume (VT), peak inspiratory airway pressure (Ppeak) and end expiratory CO2 pressure(PETCO2)were recorded at T2,T4,T6,T7, T8, T10. The venous blood samples were taken at T0, T2, T3, T4, T6, T9, T10 for the measurements of epinephrine(AE), norepinephrine(NE)and dopamine (DA) levels with high performance liquid chromatography.Data were dealt with SPSS version 10.0 statistic software. The variables of hemodynamics and stress responses were analyzed with ANOVA of repeating test data. P ＜ 0.05 means the difference in statistical significance. Results In group C, SBP, DBP and HR were significantly higher than those in group T at T2 ,T3 ,T9 (P ＜ 0.05). In group C, the levels of Ppeak were significantly higher than those in group T at T6 ,T7 ,T8 (P ＜ 0.05), and the concentrations of AE, NE and DA were also significantly higher in group C than those in group T at T2, T3 and T9 (P ＜0.05). Conclusions Ventilation with TLMA in patients during BAL is better than TC in respects of keeping stable ventilation, stable hemodynamics and producing less stress responses. Key words: Bronchoalveolar lavage(BAL); Ventilatory effects; Tracheal catheter (TC); Three-way laryngeal mask airway (TLMA); Hemodynamics; Respiratory function; Stress response