Low Tidal Ventilation Research Articles

Incidence of Post-Operative Pulmonary Complications in Patients Undergoing Cardiac Surgery with Low Tidal Volume Ventilation

Objective: This study sought to determine if low-tidal ventilation during CPB was superior to a resting-lung strategy with no ventilation in terms of pulmonary complications following surgery. Study Design: This was a retrospective study. Place and Duration: This study was done at the Punjab Institute of cardiology, Lahore from 1st May 2021 to 1st Nov, 2022. Methodology: A total of 1348 patients were enrolled in this study following inclusion criteria. They were divided into two groups equally. SPSS version 24 was used to enter and analyzed collected data. For qualitative variables was presented in frequency(%). For quantitative variables i.e., age, height, weight, preoperative FEV1/FCV, tidal volume, PEEP, PaO2 and PaCO2 mean ±SD was calculated. Chi-square was applied to compare post-operative outcomes between the groups. P-value of <0.05 was taken as significant. Results: The mean age of the cases in Group A was 55 ± 9.08 while in Group B was 56 ± 9.19. There were 75% male and 25% females in Group A while 84% male and 16% females in Group B. In our data there were 67% diabetic and 59% smokers in Group A however 62% diabetic and 58% smokers were enrolled in Group B. Mean tidal volume given to Group A was 8.5 ± 1.8 while in Group B was 7.5 ± 1.3. Peak respiratory pressure in Group A was 18 and in Group B was 16. Mean perfusion time, cross clamp time and anesthesia duration was significant between the groups p-value 0.01. Mean tidal volume given to Group A was 8.5 ± 1.8 while in Group B was 7.5 ± 1.3. Peak respiratory pressure in Group A was 18 and in Group B was 16. Mean perfusion time, cross clamp time and anesthesia duration was significant between the groups p-value 0.01. Conclusion: This study found that continuing low tidal volume ventilation was not superior to no ventilation during CPB in terms of the rate of reintubation, pleural effusion, and pulmonary congestion, although there was a significant difference between pneumonia, atelectasis, and prolong ventilation. Keywords: PEEP, CPB, FEV1/FCV ,Pulmonary Complications, Ventilation, Tidal Volume

Effect of different ventilation strategies during cardiopulmonary bypass on cardiac de-airing in congenital cardiac surgery: A trans-esophageal echocardiography comparative study

ABSTRACT Objectives This study was conducted to evaluate the efficacy of using either low tidal ventilation or continuous positive pressure ventilation on the quality of de-airing procedure during cardiopulmonary bypass (CPB) surgery for correction of congenital heart diseases. Patients and methods This study was conducted on 48 children under the age of 6 years scheduled for elective correction of congenital heart diseases. Patients were randomly allocated into three groups. In the low tidal volume (LTV) group, ventilator was set to a respiratory rate of 5 breaths per minute with tidal volume of 2–3 ml/kg of ideal body weight and a positive end-expiratory pressure of 3–5 cmH2O. In continuous positive airway pressure (CPAP) group, oxygen flow was maintained at 0.5 L/min during CPB, ventilator was shut off and the adjustable pressure-limiting valve (APL) was set at a pressure of 10 cmH2O. In the no ventilation (NV) group, ventilator was shut off, fresh flow air was completely stopped and APL was adjusted on spontaneous position. The primary outcome was the total de-airing time using transesophageal echocardiography. Results The total de-airing time was significantly decreased in CPAP group, with the shortest duration of 246.88 ± 5.40 sec in comparison to both LTV group with 284.25 ± 6.52 sec and NV group with 452.12 ± 26.6 sec with p-value 0.001. Conclusion Use of CPAP 10 cmH2O ventilation during CPB surgery for correction of congenital heart diseases could improve the process of de-airing by decreasing the total time needed to de-air heart chambers.

Efficacy of maintaining low-tidal volume mechanical ventilation as compared to resting lung strategy during coronary artery bypass graft cardiopulmonary bypass surgery: A post-hoc analysis of the MECANO trial

Study objectiveTo compare a low-tidal-volume with positive end-expiratory pressure strategy (VENT strategy) to a resting-lung-strategy (i.e., no-ventilation (noV) strategy) during cardiopulmonary bypass for coronary artery bypass graft surgery on the incidence of postoperative pulmonary complications. DesignPost-hoc analysis of the MECANO trial which was a prospective single-center, blind, randomized, parallel-group controlled trial. SettingTertiary care cardiac surgery center. PatientsPatients who underwent isolated on-pump coronary bypass surgery were randomized either to VENT or noV group. InterventionDuring the cardiopulmonary bypass phase of the cardiac surgery procedure, mechanical ventilation in the VENT group consisted of a tidal volume of 3 mL/kg, a respiratory rate of 5 per minute and a positive end-expiratory pressure of 5 cmH2O. Patients in the noV group received no ventilation during this phase. MeasurementsPrimary composite outcome combining death, early respiratory failure, ventilation support beyond day 2 and reintubation. Main resultsIn this post-hoc analysis, we retained 725 patients who underwent isolated CABG surgery, from the 1501 patients included in the original study. There were 352 in the VENT group and 373 patients in the noV group. Post-hoc comparison yielded no differences in baseline characteristics between these two groups. The primary outcome occurred less frequently in the VENT group than in the noV group, with 44 (12.5%) and 76 (20.4%) respectively (odds-ratio (OR) = 0.56 (0.37–0.84), p = 0.004). There were fewer early respiratory dysfunctions and prolonged respiratory support in the VENT group (respectively, OR = 0.34 (0.12–0.96) p = 0.033 and OR = 0.51 (0.27–0.94) p = 0.029). Complications related to mechanical ventilation were similar in the two groups. ConclusionsIn this post-hoc analysis, maintaining low-tidal ventilation compared to a resting-lung strategy was associated with fewer pulmonary postoperative complications in patients who underwent isolated CABG procedures.

High-Frequency, Low-Tidal-Volume Mechanical Ventilation Safely Improves Catheter Stability and Procedural Efficiency During Radiofrequency Ablation of Atrial Fibrillation

High-Frequency, Low-Tidal-Volume Mechanical Ventilation Safely Improves Catheter Stability and Procedural Efficiency During Radiofrequency Ablation of Atrial Fibrillation

Numerical assessment of a 3D human upper respiratory tract model: effect of anatomical structure on asymmetric tidal pulmonary ventilation characteristics

The analysis of airway ventilation characteristic is important for diagnosis and pathological assistance for respiratory diseases. It is therefore imperative to study the impact of anatomical features on the internal flow field. The article is focused on an in-silico study on impact of anatomical structure of human upper respiratory tract on transient asymmetric tidal pulmonary ventilation characteristics. Therefore, a three-dimensional human airways model is reconstructed from nasal cavity up to seventh generation bronchi from computed tomography (CT) images of a 48-year-old healthy man using computational modelling technique. A validated low Reynolds number (LRN) realisable k - ε turbulence model is used to capture the internal flow mixed turbulence characteristics. The numerical simulations were performed for asymmetric low and high tidal pulmonary ventilation (ALTPV, 10 L/min and AHTPV, 40 L/min). The numerical analysis assists to predict the near realistic airway ventilation phenomena and internal flow physics in the upper respiratory tract.

ASPECTS OF INVASIVE MECHANICAL VENTILATION IN PATIENTS WITH ARDS CAUSED BY COVID-19

Mortality among patients with severe pneumonia and / or acute respiratory distress syndrome (ARDS) due to COVID-19 infection, who underwent mechanical ventilation (MV), is characterized by a fairly high frequency. However, despite the large number of patients receiving appropriate treatment, the question of choosing the optimal ventilation parameters remains poorly understood. In our article, we reviewed the available literature data on the indications for mechanical ventilation, parameters of MV, the need for prone-positioning of patients with ARDS caused by COVID-19 infection in intensive care units to identify unresolved issues.Despite the large number of publications about respiratory support in patients with severe coronavirus infection, there are only general principles regarding the indications for switching to invasive ventilation. Most authors identified the following clinical situations: progression of hypoxemia and / or respiratory failure but with constant oxygen support with increasing percentage of oxygen in the respiratory mixture, use of high-flow cannula or non-invasive ventilation for 1 hour without improvement; persistent hypercapnia, multiorgan failure, coma, high risk of aspiration, hemodynamic instability.According to most of the studies analyzed, the main components of the ventilation strategy should be based on the principles of pulmonary protective ventilation and include the use of low tidal volumes (Vt = 4-8 ml / kg of ideal body weight) and ventilation with plateau pressure Pplat <30 cm H2O (plateau pressure - air pressure measured after an inspiratory pause of 0.5 s). At the same time, many authors recommend using prone position and high levels of positive end-expiratory pressure (PEEP) compared to low levels in patients with ARDS on the background of COVID-19.The approach to invasive mechanical ventilation in ARDS caused by SARS-CoV-2 still requires further research and answers to a number of questions.

Non-specialist therapeutic strategies in acute respiratory distress syndrome.

Acute respiratory distress syndrome (ARDS) is associated with significant morbidity and mortality. We undertook a meta-analysis of randomized controlled trials (RCTs) to determine the mortality benefit of non-specialist therapeutic interventions for ARDS available to general critical care units. A systematic search of MEDLINE, Embase, and the Cochrane Central Register for RCTs investigating therapeutic interventions in ARDS including corticosteroids, fluid management strategy, high PEEP, low tidal volume ventilation, neuromuscular blockade, prone position ventilation, or recruitment maneuvers. Data was collected on demographic information, treatment strategy, duration and dose of treatment, and primary (28 or 30-day mortality) and secondary (P<inf>a</inf>O<inf>2</inf>:FiO<inf>2</inf> ratio at 24-48 hours) outcomes. No improvement in 28-day mortality could be demonstrated in three RCTs investigating high PEEP (28.0% vs. 30.2% control; risk ratio [confidence interval] 0.93 [0.82-1.06]; eight assessing prone position ventilation (39.3% vs. 44.5%; RR 0.83 [0.68-1.01]; seven investigating neuromuscular blockade (37.8% vs. 42.0%; RR 0.91 [0.81-1.03]); ten investigating recruitment maneuvers (42.4% vs. 42.1%; RR 1.01 [0.91-1.12]); eight investigating steroids (34.8% vs. 41.1%; RR 0.81 [0.59-1.12]); and one investigating conservative fluid strategies (25.4% vs. 28.4%; RR 0.90 [0.73-1.10]). Three studies assessing low tidal volume ventilation (33.1% vs. 41.9%; RR 0.79 (0.68-0.91); P=0.001), and subgroup analyses within studies investigating prone position ventilation greater than 12 hours (33.1% vs. 44.4%; RR 0.75 [0.59-0.95), P=0.02) did reveal outcome benefit. Among non-specialist therapeutic strategies available to general critical care units, low tidal volumes and prone position ventilation for greater than 12 hours improve mortality in ARDS.

Use of Inhaled Volatile Anesthetics for Longer Term Critical Care Sedation: A Pilot Randomized Controlled Trial

Objectives: Assess feasibility, barriers to recruitment, and safety of volatile-based sedation in longer term sedation patients in North American ICUs with limited or no experience with volatile sedation. Design: Open-label, pilot randomized clinical trial performed between October 2013 and September 2018. Setting: Four Canadian ICUs across two academic tertiary and quaternary hospitals. Patients: Sixty adults anticipated needing sedation and invasive ventilation beyond 48 hours with tidal volumes greater than 350 mL, expected 6-month mortality risk less than 50%, no evidence of high intracranial pressure, or drug contraindications (malignant hyperthermia, allergy). Interventions: 2:1 randomization to inhaled volatile sedation using isoflurane or standard midazolam and/or propofol IV sedation. Measurement and Main Results: Primary outcome of safety and feasibility was assessed by staff satisfaction scores using a five-point Likert scale and serum fluoride measurements. Secondary clinical outcomes included time to extubation, quality of sedation, opioid use, cardiorespiratory parameters, vasopressor and antipsychotic drug use, and 3-month cognitive outcome measured using telephone interview for cognitive status. From 2,210 screened patients, 308 met eligibility criteria secondary to many not requiring sedation, extubation planned within 48 hours, high risk of death, or low tidal ventilation. Of 308 patients, 60 were randomized to isoflurane (n = 41) or IV (n = 19) sedation secondary to lack of substitute decision-maker or physician consent. Duration of inhaled isoflurane and IV sedation were median of 114 and 88 hours, respectively. Nine isoflurane patients crossed into the IV arm secondary to mainly hypercarbia from low tidal ventilation. Nursing and respiratory therapy staff satisfaction scores were quantitatively similar between both sedation approaches. Serum fluoride levels rose with duration of isoflurane sedation but were not associated with altered kidney function. There were no significant differences in secondary clinical outcomes. Conclusions: We showed adequate preliminary safety and acceptability of inhaled volatile anesthetics for long-term sedation.

Low Tidal Volume Mechanical Ventilation Against No Ventilation During Cardiopulmonary Bypass in Heart Surgery (MECANO): A Randomized Controlled Trial

Postoperative pulmonary complications are common after cardiac surgery and have been related to lung collapse during cardiopulmonary bypass (CPB). No consensus exists regarding the effects of maintaining mechanical ventilation during CPB to decrease these complications. To determine whether maintaining low-tidal ventilation (3mL/kg 5 times/min, with positive end expiratory pressure of 5cm H2O) during CPB (ventilation strategy) was superior to a resting-lung strategy with no ventilation (no ventilation strategy) regarding postoperative pulmonary complications, including mortality. In a randomized controlled trial, patients undergoing cardiac surgery at a single center from May 2017 through August 2019 were randomized to the ventilation or no ventilation strategy during CPB (1:1 ratio). Apart from the CPB phase, perioperative ventilation procedures were standardized. The study included 1,501 patients (mean age, 68.8 ± 10.3 years; 1,152 (76.7%) men; mean EuroSCORE II, 2.3 ± 2.7). Seven hundred fifty-six patients were in the ventilation strategy group, and no differences existed in baseline characteristics and types of procedures between the two groups. An intention-to-treat analysis yielded no significant difference between the ventilation and no ventilation groups regarding incidence of the primary composite outcome combining death, early respiratory failure, ventilation support beyond day 2, and reintubation, with 112 of 756 patients (14.8%) in the ventilation group vs 133 of 745 patients (17.9%) in the no ventilation group (OR, 0.80; 95%CI, 0.61-1.05; P= .11). Strict per-protocol analyses of 1,338 patients (89.1%) with equally distributed preoperative characteristics yielded similar results (OR, 0.81; 95%CI, 0.60-1.09; P= .16). Post hoc analysis of the subgroup who underwent isolated coronary artery bypass graft procedures (n= 725) showed that the ventilation strategy was superior to the no ventilation strategy regarding the primary outcome (OR, 0.56; 95%CI, 0.37-0.84; P= .005). Among patients undergoing cardiac surgery with CPB, continuation of low tidal volume ventilation was not superior to no ventilation during CPB with respect to postoperative complications, including death, early respiratory failure, ventilation support beyond day 2, and reintubation. ClinicalTrials.gov; No.: NCT03098524; URL: www.clinicaltrials.gov.

Multi-factorial barriers and facilitators to high adherence to lung-protective ventilation using a computerized protocol: a mixed methods study

BackgroundLung-protective ventilation (LPV) improves outcomes for patients with acute respiratory distress syndrome (ARDS) through the administration of low tidal volumes (≤ 6.5 ml/kg predicted body weight [PBW]) with co-titration of positive end-expiratory pressure and fraction of inspired oxygen. Many patients with ARDS, however, are not managed with LPV. The purpose of this study was to understand the implementation barriers and facilitators to the use of LPV and a computerized LPV clinical decision support (CDS) tool in intensive care units (ICUs) in preparation for a pilot hybrid implementation-effectiveness clinical trial.MethodsWe performed an explanatory sequential mixed methods study from June 2018 to March 2019 to evaluate the variation in LPV adherence across 17 ICUs in an integrated healthcare system with > 4000 mechanically ventilated patients annually. We analyzed 47 key informant interviews of ICU physicians, respiratory therapists (RTs), and nurses in 3 of the ICUs using a qualitative content analysis paradigm to investigate site variation as defined by adherence level (low, medium, high) and to identify barriers and facilitators to LPV and LPV CDS tool use.ResultsForty-two percent of patients had an initial set tidal volume of ≤ 6.5 ml/kg PBW during the measurement period (site range 21–80%). LPV CDS tool use was 28% (site range 6–91%). This study’s main findings revealed multi-factorial facilitators and barriers to use that varied by ICU site adherence level. The primary facilitator was that LPV and the LPV CDS tool could be used on all mechanically ventilated patients. Barriers included a persistent gap between clinician attitudes regarding the use of LPV and actual use, the perceived loss of autonomy associated with using a computerized protocol, the nature of physician-RT interaction in ventilation management, and the lack of clear organization measures of success.ConclusionsVariation in adherence to LPV persists in ICUs within a healthcare delivery system that was an early adopter of LPV. Potentially promising strategies to increase adherence to LPV and the LPV CDS tool for ARDS patients include initiating low tidal ventilation on all mechanically ventilated patients, establishing and measuring adherence measures, and focused education addressing the physician-RT interaction. These strategies represent a blueprint for a future hybrid implementation-effectiveness trial.

Effects of low tidal volume protective lung ventilation versus pressure controlled ventilation on oxygenation in patients un-dergoing gynecologic laparoscopic surgery

Objective To evaluate the effectiveness and safety of low tidal volume protective lung ventilation (PLV) and pressure controlled ventilation (PCV) in patients undergoing gynecologic laparoscopic surgery. Methods A total of 144 patients who were scheduled for gynecologic laparoscopic surgery in our hospital were enrolled. According to the random number table method, they were divided into two groups (n=72): a PLV group and a PCV group. The PLV group used a tidal volume of 6 ml/kg, an inspiration and expiration ratio of 1∶2, a respiratory rate of 16 breaths per minute, and a positive end expiratory pressure of 5 cmH2O (1 cmH2O=0.098 kPa). In the PCV group, the ventilation pressure was maintained at a tidal volume of 8 ml/kg, with an inspiration and expiration ratio of 1∶2, and a respiratory rate of 12-16 breaths per minute. Their airway peak pressure (Ppeak) and mean airway pressure (Pmean) were recorded 5 min after tracheal intubation (T1), 10 min after pneumoperitoneum (T2), 20 min af-ter pneumoperitoneum (T3), and 10 min after pneumonectomy (T4), while dynamic lung compliance (Cdyn) was calculated. Blood gas analysis was performed at T3 and T4 to record arterial oxygen partial pressure (PaO2), arterial CO2 partial pressure (PaCO2), and alveolar-arterial oxygen partial pressure difference (A-aDO2), while oxygenation index (OI) was calculated. Results At T3, the PLV group presented remarkably increased Ppeak and Pmean and decreased Cdyn, compared with the PCV group (P 0.05). There was no significant differ-ence in the incidence of respiratory complications and the length of hospitalization stay between the two groups (P>0.05). Conclusions For patients undergoing gynecologic laparoscopic surgery, PCV is helpful to maintain stable respiratory dynamics, while low tidal volume PLV is helpful to maintain oxygenation function during surgery. There is no significant difference in safety be-tween the two types of treatment. Key words: Gynaecology; Laparoscopy; Protective lung ventilation mode; Pressure controlled ventilation; Oxygenation function

Implementation of strategies to liberate patients from mechanical ventilation in a tertiary-level medical center

Considerable discrepancies have been observed in the implementation of strategies to liberate patients from mechanical ventilation. The aim of this study was to describe critical care nurses' knowledge of and self-reported and documented adherence to lung-protective ventilation, daily sedation interruption, and daily assessment of readiness to extubate and evaluate how these practices differ between patients with and without ventilator-associated pneumonia and between survivors and nonsurvivors. The survey was conducted in a tertiary-level hospital in Finland from October 2014 to June 2015. Actual adherence was evaluated based on documentation of performed practices. A total of 86 critical care nurses responded to the survey, and 85 patients were followed. The levels of knowledge of and self-reported adherence to low tidal ventilation were 84.5% and 90.2%, respectively, and the median tidal volume was at a target level in 74.4% of patients. Regarding daily sedation interruption, the level of knowledge was 85.7%, the level of self-reported adherence was 77.3%, and documented adherence was 33.3%. The levels of knowledge and self-reported adherence regarding spontaneous breathing trials were 61.9% and 71.6%, respectively. Adherence to lung-protective ventilation, daily sedation interruption, and daily assessment of readiness to extubate did not differ between patients with (n = 20) and without (n = 65) ventilator-associated pneumonia and between survivors (n = 55) and nonsurvivors (n = 30). Lung-protective ventilation, including low-tidal ventilation and avoidance of high inspiratory plateau pressures, was well implemented and adhered to. The levels of knowledge and self-reported adherence versus documented adherence regarding daily sedation interruption and spontaneous breathing trial demonstrated insufficient implementation of local guidelines. There was no effect on the outcome.

Fluid management in Acute Respiratory Distress Syndrome: A narrative review.

Acute Respiratory Distress Syndrome remains a major source of morbidity and mortality in the modern intensive care unit (ICU). Major advances in the understanding and management of this condition were made in the last two decades. The use of low tidal ventilation is a well-established therapy. Conservative fluid management is now another cornerstone of management. However, much remains to be understood in this arena. Assessing volume status in these patients may be challenging and the tools available to do so are far from perfect. Several dynamic measures including pulse pressures variation are used. Ultrasound of the lungs and the vascular system may also have a role. In addition, the type of fluid to administer when needed is still open to debate. Finally, supportive measures in these patients, early during their ICU stay and later after discharge continue to be crucial for survival and adequate recovery.

Randomized Feasibility Trial of a Low Tidal Volume-Airway Pressure Release Ventilation Protocol Compared With Traditional Airway Pressure Release Ventilation and Volume Control Ventilation Protocols.

Low tidal volume (= tidal volume ≤ 6 mL/kg, predicted body weight) ventilation using volume control benefits patients with acute respiratory distress syndrome. Airway pressure release ventilation is an alternative to low tidal volume-volume control ventilation, but the release breaths generated are variable and can exceed tidal volume breaths of low tidal volume-volume control. We evaluate the application of a low tidal volume-compatible airway pressure release ventilation protocol that manages release volumes on both clinical and feasibility endpoints. We designed a prospective randomized trial in patients with acute hypoxemic respiratory failure. We randomized patients to low tidal volume-volume control, low tidal volume-airway pressure release ventilation, and traditional airway pressure release ventilation with a planned enrollment of 246 patients. The study was stopped early because of low enrollment and inability to consistently achieve tidal volumes less than 6.5 mL/kg in the low tidal volume-airway pressure release ventilation arm. Although the primary clinical study endpoint was PaO2/FIO2 on study day 3, we highlight the feasibility outcomes related to tidal volumes in both arms. Four Intermountain Healthcare tertiary ICUs. Adult ICU patients with hypoxemic respiratory failure anticipated to require prolonged mechanical ventilation. Low tidal volume-volume control, airway pressure release ventilation, and low tidal volume-airway pressure release ventilation. We observed wide variability and higher tidal (release for airway pressure release ventilation) volumes in both airway pressure release ventilation (8.6 mL/kg; 95% CI, 7.8-9.6) and low tidal volume-airway pressure release ventilation (8.0; 95% CI, 7.3-8.9) than volume control (6.8; 95% CI, 6.2-7.5; p = 0.005) with no difference between airway pressure release ventilation and low tidal volume-airway pressure release ventilation (p = 0.58). Recognizing the limitations of small sample size, we observed no difference in 52 patients in day 3 PaO2/ FIO2 (p = 0.92). We also observed no significant difference between arms in sedation, vasoactive medications, or occurrence of pneumothorax. Airway pressure release ventilation resulted in release volumes often exceeding 12 mL/kg despite a protocol designed to target low tidal volume ventilation. Current airway pressure release ventilation protocols are unable to achieve consistent and reproducible delivery of low tidal volume ventilation goals. A large-scale efficacy trial of low tidal volume-airway pressure release ventilation is not feasible at this time in the absence of an explicit, generalizable, and reproducible low tidal volume-airway pressure release ventilation protocol.

Comparative analysis of changes in the lungs of experimental animals’ induced conventional and lung protective ventilation

Mechanical ventilation has long been the leader in the treatment of critically ill and injured patients in an intensive care unit. The aim of this study was to examine the impact of the application of positive end-expiratory pressure on histopathological findings and on the parameters of ventilation, oxygenation and acid-base status. The experimental study included 42 animals (piglets), which were divided into of tree groups, each containing 14. The animals of the control group (conventional ventilation) were ventilated with the tidal volume of 10-15 mL/kg. Tidal volume of 6 mL/kg was applied in the low tidal ventilation group, whereas the ventilation strategy in the lung protective ventilation group meant the application of a tidal volume of 6 mL/kg and the 7 mbar of positive end-expiratory pressure. Mechanical ventilation in each animal lasted for 4 hours. After conducting mechanical ventilation, samples were taken from the lung tissue, which were sent for histopathological examination. The parameters of ventilation, oxygenation and acid-base status were measured after each hour’s duration of mechanical ventilation. Application of positive end-expiratory pressure 5-10 mbar during mechanical ventilation is a safe and useful method which is not followed by the occurrence of significant abnormalities in the structure of the ventilated lung. However, a low tidal volume without positive end-expiratory pressure causes significant changes in the histological structure of healthy lungs. Positive end-expiratory pressure keeps the alveoli open throughout the respiratory cycle which allows the lungs to maintain homeostasis in terms of adequate ventilation, oxygenation and acid-base status.

Early application of airway pressure release ventilation may reduce the duration of mechanical ventilation in acute respiratory distress syndrome

PurposeExperimental animal models of acute respiratory distress syndrome (ARDS) have shown that the updated airway pressure release ventilation (APRV) methodologies may significantly improve oxygenation, maximize lung recruitment, and attenuate lung injury, without circulatory depression. This led us to hypothesize that early application of APRV in patients with ARDS would allow pulmonary function to recover faster and would reduce the duration of mechanical ventilation as compared with low tidal volume lung protective ventilation (LTV).MethodsA total of 138 patients with ARDS who received mechanical ventilation for <48 h between May 2015 to October 2016 while in the critical care medicine unit (ICU) of the West China Hospital of Sichuan University were enrolled in the study. Patients were randomly assigned to receive APRV (n = 71) or LTV (n = 67). The settings for APRV were: high airway pressure (Phigh) set at the last plateau airway pressure (Pplat), not to exceed 30 cmH2O) and low airway pressure ( Plow) set at 5 cmH2O; the release phase (Tlow) setting adjusted to terminate the peak expiratory flow rate to ≥ 50%; release frequency of 10–14 cycles/min. The settings for LTV were: target tidal volume of 6 mL/kg of predicted body weight; Pplat not exceeding 30 cmH2O; positive end-expiratory pressure (PEEP) guided by the PEEP–FiO2 table according to the ARDSnet protocol. The primary outcome was the number of days without mechanical ventilation from enrollment to day 28. The secondary endpoints included oxygenation, Pplat, respiratory system compliance, and patient outcomes.ResultsCompared with the LTV group, patients in the APRV group had a higher median number of ventilator-free days {19 [interquartile range (IQR) 8–22] vs. 2 (IQR 0–15); P < 0.001}. This finding was independent of the coexisting differences in chronic disease. The APRV group had a shorter stay in the ICU (P = 0.003). The ICU mortality rate was 19.7% in the APRV group versus 34.3% in the LTV group (P = 0.053) and was associated with better oxygenation and respiratory system compliance, lower Pplat, and less sedation requirement during the first week following enrollment (P < 0.05, repeated-measures analysis of variance).ConclusionsCompared with LTV, early application of APRV in patients with ARDS improved oxygenation and respiratory system compliance, decreased Pplat and reduced the duration of both mechanical ventilation and ICU stay.

The effects of low tidal ventilation on lung strain correlate with respiratory system compliance

BackgroundThe effect of alterations in tidal volume on mortality of acute respiratory distress syndrome (ARDS) is determined by respiratory system compliance. We aimed to investigate the effects of different tidal volumes on lung strain in ARDS patients who had various levels of respiratory system compliance.MethodsNineteen patients were divided into high (Chigh group) and low (Clow group) respiratory system compliance groups based on their respiratory system compliance values. We defined compliance ≥0.6 ml/(cmH2O/kg) as Chigh and compliance <0.6 ml/(cmH2O/kg) as Clow. End-expiratory lung volumes (EELV) at various tidal volumes were measured by nitrogen wash-in/washout. Lung strain was calculated as the ratio between tidal volume and EELV. The primary outcome was that lung strain is a function of tidal volume in patients with various levels of respiratory system compliance.ResultsThe mean baseline EELV, strain and respiratory system compliance values were 1873 ml, 0.31 and 0.65 ml/(cmH2O/kg), respectively; differences in all of these parameters were statistically significant between the two groups. For all participants, a positive correlation was found between the respiratory system compliance and EELV (R = 0.488, p = 0.034). Driving pressure and strain increased together as the tidal volume increased from 6 ml/kg predicted body weight (PBW) to 12 ml/kg PBW. Compared to the Chigh ARDS patients, the driving pressure was significantly higher in the Clow patients at each tidal volume. Similar effects of lung strain were found for tidal volumes of 6 and 8 ml/kg PBW. The “lung injury” limits for driving pressure and lung strain were much easier to exceed with increases in the tidal volume in Clow patients.ConclusionsRespiratory system compliance affected the relationships between tidal volume and driving pressure and lung strain in ARDS patients. These results showed that increasing tidal volume induced lung injury more easily in patients with low respiratory system compliance.Trial registrationClinicaltrials.gov identifier NCT01864668, Registered 21 May 2013.

One-Lung Ventilation with Additional Ipsilateral Ventilation of Low Tidal Volume and High Frequency in Lung Lobectomy.

BackgroundTo investigate the protective effects of additional ipsilateral ventilation of low tidal volume and high frequency on lung functions in the patients receiving lobectomy.Material/MethodsSixty patients receiving lung lobectomy were randomized into the conventional one-lung ventilation (CV) group (n=30) and the ipsilateral low tidal volume high frequency ventilation (LV) group (n=30). In the CV group, patients received only contralateral OLV. In the LV group, patients received contralateral ventilation and additional ipsilateral ventilation of low tidal volume of 1–2 ml/kg and high frequency of 40 times/min. Normal lung tissues were biopsied for the analysis of lung injury. Lung injury was scored by evaluating interstitial edema, alveolar edema, neutrophil infiltration, and alveolar congestion.ResultsAt 30 min and 60 min after the initiation of one-lung ventilation and after surgery, patients in the LV group showed significantly higher ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen than those in the CV group (P<0.001). Lung injury was significantly less severe (2.7±0.7) in the LV group than in the CV group (3.1±0.7) (P=0.006).ConclusionsAdditional ipsilateral ventilation of low tidal volume and high frequency can decrease the risk of hypoxemia and alleviate lung injury in patients receiving lobectomy.

Optimal support techniques when providing mechanical ventilation to patients with acute respiratory distress syndrome.

Adult respiratory distress syndrome (ARDS) is a type of acute diffuse lung injury characterized by severe inflammation, increased pulmonary vascular permeability and a loss of aerated lung tissue. The effects of high fraction of inspired oxygen (FiO2 ) include oxygen toxicity manifested by damage to the lung parenchyma in the acute phase of lung injury. There is still a high mortality rate among this group of patients, so clinically sensitive evidence-based interventions are paramount to maximize survival chances during critical care. The aim of this article is to explore the current opinion concerning optimal mechanical ventilation support techniques for patients with acute respiratory distress syndrome. A literature search of clinical trials and observation studies, reviews, discussion papers, meta-analyses and clinical guidelines written in English up to 2015, derived from the databases of Scopus, CINAHL, Cochrane Library databases and PubMed was conducted. Low tidal volume, pressure limitation and prone positioning in severe ARDS patients appear to be of some benefit. More research is required and further development and use of standardized protocols is an important strategy for reducing practice variations across disciplines, as well as giving clear guidelines to nurses practising in critical care. There is also evidence that this syndrome is under-diagnosed and the utilization of lung protective ventilation is still variable. It is important that nurses have underlying knowledge of both aetiology of ARDS and ventilation management, and that they monitor patients very closely. The adoption of a low tidal ventilation protocol, which is based on quality evidence guidelines, the value of rescue therapies and patient observation practices in the overall patient management, and the need to place emphasis on long-term patient outcomes, all these emerge as key factors for consideration and future research. However, there is also a need for more research that would explore the unique contribution of nurses in the management of this patient group, as it is difficult to discern this in the current literature.

Differences in functional exercise capacity and pulmonary function tests between acute respiratory distress syndrome (ARDS) of pulmonary and extrapulmonary origin

Treatment of ARDS with low volume tidal ventilation has shown improvement in survival rates as compared with traditional high tidal volume ventilation strategy. Nevertheles, respiratory morbidity, including impaired pulmonary function with obstructive and restricitive patterns, decreased DLCO diffusion and reduced exercise capacity have been described in survivors.