Lung Mechanics In Patients Research Articles

Still no room to breathe: insights on supine lung mechanics from oscillometry in COPD

Still no room to breathe: insights on supine lung mechanics from oscillometry in COPD

The impact of lung transplantation on esophageal motility and inter-relationships with reflux and lung mechanics in patients with restrictive and obstructive respiratory disease.

For many patients with lung disease the only proven intervention to improve survival and quality of life is lung transplantation (LTx). Esophageal dysmotility and gastroesophageal reflux (GER) are common in patients with respiratory disease, and often associate with worse prognosis following LTx. Which, if any patients, should be excluded from LTx based on esophageal concerns remains unclear. Our aim was to understand the effect of LTx on esophageal motility diagnosis and examine how this and the other physiological and mechanical factors relate to GER and clearance of boluses swallowed. We prospectively recruited 62 patients with restrictive (RLD) and obstructive (OLD) lung disease (aged 33-75 years; 42 men) who underwent high resolution impedance manometry and 24-h pH-impedance before and after LTx. RLD patients with normal motility were more likely to remain normal (p = 0.02), or if having abnormal motility to change to normal (p = 0.07) post-LTx than OLD patients. Esophageal length (EL) was greater in OLD than RLD patients' pre-LTx (p < 0.001), reducing only in OLD patients' post-LTx (p = 0.02). Reduced EL post-LTx associated with greater contractile reserve (r = 0.735; p = 0.01) and increased likelihood of motility normalization (p = 0.10). Clearance of reflux improved (p = 0.01) and associated with increased mean nocturnal baseline impedance (p < 0.001) in RLD but not OLD. Peristaltic breaks and thoraco-abdominal pressure gradient impact both esophageal clearance of reflux and boluses swallowed (p < 0.05). RLD patients are more likely to show improvement in esophageal motility than OLD patients post-LTx. However, the effect on GER is more difficult to predict and requires other GI, anatomical and pulmonary factors to be taken into consideration.

A novel adaptive filter with a heart-rate-based reference signal for esophageal pressure signal denoising

Esophageal pressure (Peso) is one of the most common and minimally invasive methods used to assess the respiratory and lung mechanics in patients receiving mechanical ventilation. However, the Peso measurement is contaminated by cardiogenic oscillations (CGOs), which cannot be easily eliminated in real-time. The field of study dealing with the elimination of CGO from Peso signals is still in the early stages of its development. In this study, we present an adaptive filtering-based method by constructing a reference signal based on the heart rate and sine function to remove CGOs in real-time. The proposed technique is tested using clinical data acquired from 20 patients admitted to the intensive care unit. Lung compliance ( QUOTE ) and esophageal pressure swings (△Pes) are used to evaluate the performance and efficiency of the proposed technique. The CGO can be efficiently suppressed when the constructional reference signal contains the fundamental, and second and third harmonic frequencies of the heart rate signal. The analysis of the data of 8 patients with controlled mechanical ventilation reveals that the standard deviation/mean of the QUOTE is reduced by 28.4–79.2% without changing the QUOTE and the △Pes measurement is more accurate, with the use of our proposed technique. The proposed technique can effectively eliminate the CGOs from the measured Peso signals in real-time without requiring additional equipment to collect the reference signal.

Adjusting ventilator settings to avoid air trapping in extremely premature infants reduces the need for tracheostomy and length of stay.

Despite the improving understanding of how lung mechanics and tidal volume requirements evolve during the evolution of bronchopulmonary dysplasia (BPD), clinical management continues to be heterogeneous and inconsistent at many institutions. Recent reports have examined the use of high tidal-volume low respiratory rate strategies in these patients once disease has been well established to help facilitate their eventual extubation and improve their long-term neurodevelopmental outcomes. In this retrospective observational research study, we describe how intentional adjustment of ventilator settings based on patient lung mechanics by an interdisciplinary BPD team improved the care of the at-risk population of infants, reduced the need for tracheostomies, as well as length of stay over a period of over 3 years. The team aimed to establish consistency in the management of these children using a high tidal volume, low-rate approach, and titrating PEEP to address the autoPEEP and bronchomalacia that is frequently observed in this patient population.

Effects of Iloprost on Oxygenation during One-Lung Ventilation in Patients with Low Diffusing Capacity for Carbon Monoxide: A Randomized Controlled Study.

The protective mechanism of hypoxic pulmonary vasoconstriction during one-lung ventilation (OLV) is impaired in patients with a low diffusing capacity for carbon monoxide (DLCO). We hypothesized that iloprost inhalation would improve oxygenation and lung mechanics in patients with low DLCO who underwent pulmonary resection. Forty patients with a DLCO < 75% were enrolled. Patients were allocated into either an iloprost group (ILO group) or a control group (n = 20 each), in which iloprost and saline were inhaled, respectively. The partial pressure of arterial oxygen/fraction of inspired oxygen (PaO2/FiO2) ratio, pulmonary shunt fraction, alveolar dead space, dynamic compliance, and hemodynamic parameters were assessed 20 min after the initiation of OLV and 20 min after drug administration. Repeated variables were analyzed using a linear mixed model between the groups. Data from 39 patients were analyzed. After iloprost inhalation, the ILO group exhibited a significant increase in the PaO2/FiO2 ratio and a decrease in alveolar dead space compared with the control group (p = 0.025 and p = 0.042, respectively). Pulmonary shunt, dynamic compliance, hemodynamic parameters, and short-term prognosis were comparable between the two groups. Selective iloprost administration during OLV reduced alveolar dead space and improved oxygenation while minimally affecting hemodynamics and short-term prognosis.

Multiplex Ventilation: Solutions for Four Main Safety Problems.

The COVID-19 pandemic has led to an increased demand for mechanical ventilators and concerns of a ventilator shortage. Several groups have advocated for 1 ventilator to ventilate 2 or more patients in the event of such a shortage. However, differences in patient lung mechanics could make sharing a ventilator detrimental to both patients. Our previous study indicated failure to ventilate in 67% of simulations. The safety problems that must be solved include individual control of tidal volume (VT), individual measurement of VT, individualization of PEEP settings, and individual PEEP measurement. The purpose of this study was to evaluate potential solutions developed at our institution. Two separate lung simulators were ventilated with a modified multiplex circuit using pressure control ventilation. Parameters of the lung models used for simulations (resistance and compliance) were evidence-based from published studies. Individual circuit-modification devices were first evaluated for accuracy. Devices were an adjustable flow diverter valve, a prototype dual volume display, a PEEP valve, and a disposable PEEP display. Then the full modified multiplex circuit was assessed by ventilating 6 pairs of simulated patients with different lung models and attempting to equalize ventilation. Ventilation was considered equalized when VT and end-expiratory lung volume were within 10% for each simulation. The adjustable flow diverter valve allowed volume adjustment to 1 patient without affecting the other. The average error of the dual volume display was -17%. The PEEP valves individualized PEEP, but the PEEP gauge error ranged from 17% to 41%. Using the multiplex circuit, ventilation was equalized regardless of differences in resistance or compliance, reversing the "failure modes" of our previous study. The results of this simulation-based study indicate that devices for individual control and display of VT and PEEP are effective in extending the usability and potential patient safety of multiplex ventilation.

Transpulmonary pressure measurements and lung mechanics in patients with early ARDS and SARS-CoV-2.

PurposeAcute Respiratory Distress Syndrome (ARDS) secondary to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has demonstrated variable oxygenation and respiratory-system mechanics without investigation of transpulmonary and chest-wall mechanics. This study describes lung, chest wall and respiratory-system mechanics in patients with SARS-CoV-2 and ARDS.MethodsData was collected from forty patients with confirmed SARS-CoV-2 and ARDS at Beth Israel Deaconess Medical Center in Boston, Massachusetts. Esophageal balloons were placed to estimate pleural and transpulmonary pressures. Clinical characteristics, respiratory-system, transpulmonary, and chest-wall mechanics were measured over the first week.ResultsPatients had moderate-severe ARDS (PaO2/FiO2 123[98–149]) and were critically ill (APACHE IV 108 [94–128] and SOFA 12 [11–13]). PaO2/FiO2 improved over the first week (150 mmHg [122.9–182] to 185 mmHg [138–228] (p = 0.035)). Respiratory system (30–35 ml/cm H2O), lung (40–50 ml/cm H2O) and chest wall (120–150 ml/cm H2O) compliance remained similar over the first week. Elevated basal pleural pressures correlated with BMI. Patients required prolonged mechanical ventilation (14.5 days [9.5–19.0]), with a mortality of 32.5%.ConclusionsPatients displayed normal chest-wall mechanics, with increased basal pleural pressure. Respiratory system and lung mechanics were similar to known existing ARDS cohorts. The wide range of respiratory system mechanics illustrates the inherent heterogeneity that is consistent with typical ARDS.

Effect of Tiotropium Soft Mist Inhalers on Dynamic Changes in Lung Mechanics of Patients with Chronic Obstructive Pulmonary Disease Receiving Mechanical Ventilation: A Prospective Pilot Study.

The effects of tiotropium bromide soft mist inhalers (SMIs) in patients with chronic obstructive pulmonary disease (COPD) receiving mechanical ventilation remain unexplored. This study investigated the dynamic effects of a tiotropium SMI on lung mechanics and gas exchange in these patients. We analyzed 11 mechanically ventilated and hemodynamically stable patients with COPD who experienced acute exacerbation and were ready to be weaned from the ventilator. Two puffs of tiotropium (2.5 μg/puff) were administered with a T-adaptor connected to the ventilator circuit. Lung mechanics—peak inspiratory pressure, plateau pressure, mean airway pressure, maximum respiratory resistance (Rrs), and gas exchange function—were analyzed. The two-puff tiotropium SMI treatment led to the greatest reduction in Rrs at 6 h, with the Rrs returning to baseline gradually, and significantly improved the PaO2/FiO2 ratio at 24 h. Compared with baseline values, tiotropium SMI had the strongest effect on Rrs between hours 3 and 6 but did not significantly affect hemodynamic parameters. Tiotropium SMI administration in mechanically ventilated patients with COPD achieved the greatest reduction in Rrs at 6 h and significantly improved the PaO2/FiO2 ratio at 24 h. Future studies should investigate whether the bronchodilation effect can be improved with increased dosage or frequency.

Intraoperative MgSO4 infusion protects oxygenation and lung mechanics in COPD patients during general anesthesia. A randomized clinical trial.

The purpose of this study was to examine the effects of an intraoperative MgSO4 infusion on arterial oxygenation and lung mechanics in patients with moderate COPD undergoing cancer larynx surgery under general anesthesia (GA). Our primary outcome was arterial oxygenation determined by the PaO2 and PaO2 /FiO2 . The secondary outcomes were lung mechanics (peak airway pressure, airway plateau pressure, dead space, lung compliance, airway resistance) and postoperative complications. In this randomized controlled double-blinded trial, 40 patients with an ASA classifications II and/or III who were diagnosed with moderate COPD and who were scheduled for cancer larynx surgery under GA were randomly allocated into two equal groups, the target (Mg group) and control group (C group). In the Mg group, 30mg/kg of 10% MgSO4 solution was administered intravenously for over 20minutes as the loading dose, followed by the continuous infusion of 10mg/kg/hr In the C group, the same loading and maintenance infusion rates were administered using 0.9% saline. Unlike the C group (baseline "T0" to post-infusion "T1" interval 294±97 vs 238±71mmHg, respectively, P=.04±SD), the Mg group exhibited preserved intraoperative PaO2 (T0 to T1 interval 271±89 vs 257±53mmHg, respectively, P=.54±SD) and PaO2 /FiO2 (C group T0 to T1 interval 404±81 vs 349±84, P=.04 and Mg group 394±91 vs 379±95, P=.61, respectively), and these effects were modest. Further, compared to the C group, the Mg group exhibited lower airway resistance, dead space, airway plateau pressure, and peak airway pressure, and higher dynamic compliance. The postoperative PaO2 and PaO2 /FiO2 were higher in the Mg group compared to the C group. Intraoperative infusion of MgSO4 in patients with moderate COPD undergoing laryngectomy surgery under GA produces mild perioperative protective effects on both arterial oxygenation and lung mechanics. ClinicalTrials.gov identifier: NCT03461328; registration date: 8 March 2018.

Prospective Observational Study to Evaluate the Effect of Different Levels of Positive End-Expiratory Pressure on Lung Mechanics in Patients with and without Acute Respiratory Distress Syndrome.

Background: The optimal level of positive end-expiratory pressure is still under debate. There are scare data examining the association of PEEP with transpulmonary pressure (TPP), end-expiratory lung volume (EELV) and intraabdominal pressure in ventilated patients with and without ARDS. Methods: We analyzed lung mechanics in 3 patient groups: group A, patients with ARDS; group B, obese patients (body mass index (BMI) > 30 kg/m2) and group C, a control group. Three levels of PEEP (5, 10, 15 cm H2O) were used to investigate the consequences for lung mechanics. Results: Fifty patients were included, 22 in group A, 18 in group B (BMI 38 ± 2 kg/m2) and 10 in group C. At baseline, oxygenation showed no differences between the groups. Driving pressure (ΔP) and transpulmonary pressure (ΔPL) was higher in group B than in groups A and C at a PEEP of 5 cm H2O (ΔP A: 15 ± 1, B: 18 ± 1, C: 14 ± 1 cm H2O; ΔPL A: 10 ± 1, B: 13 ± 1, C: 9 ± 0 cm H2O). Peak inspiratory pressure (Pinsp) rose in all groups as PEEP increased, but the resulting driving pressure and transpulmonary pressure were reduced, whereas EELV increased. Conclusion: Measuring EELV or TPP allows a personalized approach to lung-protective ventilation.

Nebulized dexmedetomidine improves pulmonary shunt and lung mechanics during one-lung ventilation: a randomized clinical controlled trial.

BackgroundDexmedetomidine (Dex), a selective a2-adrenergic receptor agonist, has been previously reported to attenuate intrapulmonary shunt during one-lung ventilation (OLV) and to alleviate bronchoconstriction. However, the therapeutic effects of nebulized Dex on pulmonary shunt and lung mechanics during OLV have not been evaluated. Here we determine whether nebulized dexmedetomidine improved pulmonary shunt and lung mechanics in patients undergoing elective thoracic surgery in a prospective randomized controlled clinical trial.MethodsOne hundred and twenty-eight patients undergoing elective thoracoscopic surgery were included in this study and randomly divided into four groups: 0.9% saline (Placebo group), 0.5 µg/kg (Dex0.5 group), 1 µg/kg (Dex1 group) and 2 µg/kg (Dex2group) dexmedetomidine. After bronchial intubation, patients received different nebulized doses of dexmedetomidine (0.5 µg/kg, 1 µg/kg and 2 µg/kg) or 0.9% saline placebo during two-lung ventilation(TLV). OLV was initiated 15 min after bronchial intubation. Anesthesia was maintained with intravenous infusion of cisatracurium and propofol. Bispectral Index values were maintained within 40–50 by adjusting the infusion of propofol in all groups. Arterial blood gas samples and central venous blood gas samples were taken as follows: 15 min after bronchial intubation during two-lung ventilation (TLV15), after 30 and 60 min of OLV (OLV30and OLV60, respectively) and 15 min after reinstitution of TLV (ReTLV). Dynamic compliance was also calculated at TLV15, OLV30, OLV60 and ReTLV.ResultsDex decreased the requirement of propofol in a dose-dependent manner(P = 0.000). Heart rate (HR) and mean arterial pressure (MAP) displayed no significant difference among groups (P = 0.397 and 0.863). Compared with the placebo group, Dex administered between 0.5 and 2 µg/kg increased partial pressure of oxygen (PaO2) significantly at OLV30 and OLV60(P = 0.000); however, Dex administered between 1 and 2 µg/kg decreased pulmonary shunt fraction (Qs/Qt) at OLV30 and OLV60(P = 0.000). Compared with the placebo group, there were significant increases with dynamic compliance (Cdyn) after OLV in Dex0.5, Dex1 and Dex2group(P = 0.000). Conclusions. Nebulized dexmedetomidine improved oxygenation not only by decreasing pulmonary shunt but also by improving lung compliance during OLV, which may be effective in managing OLV.

The Effects of Alveolar Recruitment Maneuver Versus Low Tidal Volume Ventilation on Oxygenation and Lung Mechanics in Patients Undergoing Laparoscopic Surgeries: A Prospective Randomized Controlled Study.

Different ventilatory strategies have been studied to improve gas exchange and compliance of the lungs in patients undergoing laparoscopic surgeries. This study aimed to test the impact of alveolar recruitment maneuver versus low tidal volume ventilation combine with PEEP on arterial oxygenation and lung mechanics in patients undergoing laparoscopic surgeries. Sixty patients were randomly allocated into three equal groups according to the type of ventilation strategy used during surgery. In the control group, patients received conventional volume-controlled ventilation with 10ml/Kg VT and zero PEEP (ZEEP). In group II ( LTV ), patients received low tidal volume ventilation in the form of 6-8 ml/Kg VT and PEEP 5cmH2O. In group III (REC), patients received 6-8 ml/Kg and recruitment maneuvers were done every 10 minutes after intubation till extubation by manual inflation to 40cmH2O peak inspiratory pressure for 15 seconds then the patient was placed back to the same ventilation settings with PEEP of 5cmH2O. The primary outcome is the dynamic compliance. The secondary outcome measures include PaO2, PH, PCO2, SPO2, HR and MAP. Demographic characteristics and duration of surgery were comparable among groups. PaO2 was highly significantly increased (p <0.001) in the recruitment group (Rec) compared to the conventional group (C) and low tidal volume ventilation group (LTV). There was significant increase in dynamic compliance in the recruitment group (REC) compared with the conventional (C) and low tidal volume (LTV) groups. SpO2, PaCO2 showed a highly statistical significance differences between the three ventilated groups. There were no statistically significant differences between the three ventilated groups in terms of PH. There were no statistically significant differences between the three ventilated groups in terms of Mean arterial blood pressure and HR. repeated recruitment maneuvers combined with 5 cm H2O of PEEP increased respiratory system compliance and PaO2 in patients undergoing laparoscopic surgeries without hemodynamics adverse effects.

The Effects of Alveolar Recruitment Maneuver Versus Low Tidal Volume Ventilation on Oxygenation and Lung Mechanics in Patients Undergoing Laparoscopic Surgeries: A Prospective Randomized Controlled Study

The Effects of Alveolar Recruitment Maneuver Versus Low Tidal Volume Ventilation on Oxygenation and Lung Mechanics in Patients Undergoing Laparoscopic Surgeries: A Prospective Randomized Controlled Study

Evaluation of the effects of dexmedetomidine infusion on oxygenation and lung mechanics in morbidly obese patients with restrictive lung disease

BackgroundDexmedetomidine infusion improves oxygenation and lung mechanics in patients with chronic obstructive lung disease; however, its effect in patients with restrictive lung disease has not been thoroughly investigated yet. The aim of this work was to evaluate the effects of dexmedetomidine infusion on oxygenation and lung mechanics in morbidly obese patients with restrictive lung disease.MethodsForty-two morbidly obese patients scheduled for bariatric surgery were included in the study. Patients were randomized to receive either dexmedetomidine infusion at a bolus dose of 1mcg/Kg followed by infusion at 1 mcg/Kg/hour for 90 min (Dexmedetomidine group), or normal saline infusion (Control group). Both groups were compared with regard to: oxygenation {P/F ratio: PaO2/fraction of inspired oxygen (FiO2)}, lung compliance, dead space, plateau pressure, blood pressure, and heart rate.ResultsDexmedetomidine group showed significant improvement of the PaO2/FiO2 ratio, and higher lung compliance compared to control group by the end of drug infusion. Dexmedetomidine group demonstrated decreased dead space, plateau pressure, blood pressure, and heart rate compared to control group by the end of drug infusion.ConclusionA 90-min dexmedetomidine infusion resulted in moderate improvement in oxygenation and lung mechanics in morbidly obese patients with restrictive lung disease.Trial registrationclinicaltrials.gov: NCT02843698 on 20 July 2016.

Advances in clinical application of adaptive support ventilation

Mechanical ventilation is one of the most commonly used respiratory treatments in intensive care unit.New ventilation modes are developed to reduce the occurrence of mechanical ventilation complications, and adaptive support ventilation (ASV) is one of them.ASV is a newer form of closed-loop controlled ventilation which provides automated selection of initial ventilator parameters based on measurements of patient lung mechanics and breathing effort.Now, the basic theory, parameter setting, advantages and disadvantages of ASV were summarized, and the clinical application in pediatric population was also concluded. Key words: Adaptive support ventilation; Closed-loop controlled ventilation; Clinical application

Effects of bronchodilation on biomarkers of peripheral airway inflammation in COPD

Peripheral airway inflammation and dysfunction are key elements in the pathogenesis of COPD. The exhaled alveolar fraction of nitric oxide (CANO) is an indirect biomarker of lung peripheral inflammation. We tested whether inhaled long-acting bronchodilators (LABA) can affect CANO and we evaluated correlations with lung mechanics in patients with COPD.Two-centre, randomised, double blind, crossover study including COPD patients with moderate-to-severe airflow obstruction. Following a pharmacological washout, multi-flow exhaled fraction of NO (FENO), plethysmography, lung diffusion (DLCO), single breath nitrogen washout test and dyspnoea were measured in a crossover manner at baseline and 30, 60 and 180 min following administration of salmeterol (Sal) or formoterol fumarate (FF). (ClinicalTrials.gov, number NCT01853787).Fort-five patients were enrolled (median age: 71.8 years; 84.4% males). At baseline, CANO correlated with airway resistances (r = 0.422), residual volume/total lung capacity (RV/TLC; r = 0.375), transfer factor (r= -0.463) and forced expiratory volume in 1 s (FEV1; r= -0.375, all P < 0.01). After LABA administration, we found a significant reduction of FENO that reached statistical significance at 180’; no difference was found between FF and S. Consistently, a significant reduction of CANO was documented at 60’ and 180’ compared to baseline for both FF and S (P < 0.01 and P < 0.05, respectively). Changes in CANO were correlated with changes in vital capacity (r=-44; P < 0.001) and RV/TLC (r = 0.56; P < 0.001), but not FEV1.In COPD, direct correlations were found between the levels of CANO and the magnitude of peripheral airway dysfunction. LABA reduced CANO levels. The reduction was associated with improvement in functional parameters reflecting air trapping.

Dexmedetomidine improves function of lung oxygenation in patients with moderate chronic obstructive pulmonary disease underwent lung cancer surgery

To determine whether dexmedetomidine (Dex) improves oxygenation and lung mechanics in patients with moderate chronic obstructive pulmonary disease (COPD) during lung cancer surgery. Methods: Fifty-six patients with moderate COPD were randomly allocated to a control group and a Dex group (n=28 each). In the Dex group, dexmedetomidine was given as an initial loading dose at 1.0 μg/kg lasting for 10 min followed by a maintenance dose at 0.5 μg/(kg.h) during OLV while the control group was administered an equal volume of 0.9% saline accordingly. Results: Patients in the Dex group had a significantly higher oxygenation index (P<0.05) and higher dynamic lung compliance at Dex-30 and Dex-60 (P<0.05) compared with those in the control group. In the Dex group, oxygenation index in the postoperative period was significantly higher (P= 0.025) and postoperative complications were lower than those in the control group. Conclusion: Dex administration may provide clinically relevant benefits by improving o xygenation index and lung mechanics, and reducing postoperative pulmonary complications in patients with moderate COPD underwent lung cancer surgery.

Lung hyperinflation by mechanical ventilation versus isolated tracheal aspiration in the bronchial hygiene of patients undergoing mechanical ventilation.

ObjectiveTo determine the efficacy of lung hyperinflation maneuvers via a mechanical ventilator compared to isolated tracheal aspiration for removing secretions, normalizing hemodynamics and improving lung mechanics in patients on mechanical ventilation.MethodsThis was a randomized crossover clinical trial including patients admitted to the intensive care unit and on mechanical ventilation for more than 48 hours. Patients were randomized to receive either isolated tracheal aspiration (Control Group) or lung hyperinflation by mechanical ventilator (MVH Group). Hemodynamic and mechanical respiratory parameters were measured along with the amount of aspirated secretions.ResultsA total of 50 patients were included. The mean age of the patients was 44.7 ± 21.6 years, and 31 were male. Compared to the Control Group, the MVH Group showed greater aspirated secretion amount (3.9g versus 6.4g, p = 0.0001), variation in mean dynamic compliance (-1.3 ± 2.3 versus -2.9 ± 2.3; p = 0.008), and expired tidal volume (-0.7 ± 0.0 versus -54.1 ± 38.8, p = 0.0001) as well as a significant decrease in peak inspiratory pressure (0.2 ± 0.1 versus 2.5 ± 0.1; p = 0.001).ConclusionIn the studied sample, the MVH technique led to a greater amount of aspirated secretions, significant increases in dynamic compliance and expired tidal volume and a significant reduction in peak inspiratory pressure.

Effects of dexmedetomidine on oxygenation and lung mechanics in patients with moderate chronic obstructive pulmonary disease undergoing lung cancer surgery: A randomised double-blinded trial.

BACKGROUNDChronic obstructive pulmonary disease (COPD) is a risk factor that increases the incidence of postoperative cardiopulmonary morbidity and mortality after lung resection. Dexmedetomidine, a selective α2-adrenoreceptor agonist, has been reported previously to attenuate intrapulmonary shunt during one-lung ventilation (OLV) and to alleviate bronchoconstriction.OBJECTIVEThe objective is to determine whether dexmedetomidine improves oxygenation and lung mechanics in patients with moderate COPD during lung cancer surgery.DESIGNA randomised, double-blinded, placebo-controlled study.SETTINGSingle university hospital.PARTICIPANTSFifty patients scheduled for video-assisted thoracoscopic surgery who had moderate COPD. Patients were randomly allocated to a control group or a Dex group (n = 25 each).INTERVENTIONSIn the Dex group, dexmedetomidine was given as an initial loading dose of 1.0 μg kg−1 over 10 min followed by a maintenance dose of 0.5 μg kg−1 h−1 during OLV while the control group was administered a comparable volume of 0.9% saline. Data were measured at 30 min (DEX-30) and 60 min (DEX-60) after dexmedetomidine or saline administration during OLV.MAIN OUTCOME MEASURESThe primary outcome was the effect of dexmedetomidine on oxygenation. The secondary outcome was the effect of dexmedetomidine administration on postoperative pulmonary complications.RESULTSPatients in the Dex group had a significantly higher PaO2/FiO2 ratio (27.9 ± 5.8 vs. 22.5 ± 8.4 and 28.6 ± 5.9 vs. 21.0 ± 9.9 kPa, P < 0.05), significantly lower dead space ventilation (19.2 ± 8.5 vs. 24.1 ± 8.1 and 19.6 ± 6.7 vs. 25.3 ± 7.8%, P < 0.05) and higher dynamic compliance at DEX-30 and DEX-60 (P = 0.0001 and P = 0.0184) compared with the control group. In the Dex group, the PaO2/FiO2 ratio in the postoperative period was significantly higher (P = 0.022) and the incidence of ICU admission was lower than in the control group.CONCLUSIONDexmedetomidine administration may provide clinically relevant benefits by improving oxygenation and lung mechanics in patients with moderate COPD undergoing lung cancer surgery.TRIAL REGISTRATIONClinicalTrial.gov identifier: NCT 02185430.

Physiological Effects of the Open Lung Approach in Patients with Early, Mild, Diffuse Acute Respiratory Distress Syndrome: An Electrical Impedance Tomography Study.

To test the hypothesis that in early, mild, acute respiratory distress syndrome (ARDS) patients with diffuse loss of aeration, the application of the open lung approach (OLA) would improve homogeneity in lung aeration and lung mechanics, without affecting hemodynamics. Patients were ventilated according to the ARDS Network protocol at baseline (pre-OLA). OLA consisted in a recruitment maneuver followed by a decremental positive end-expiratory pressure trial. Respiratory mechanics, gas exchange, electrical impedance tomography (EIT), cardiac index, and stroke volume variation were measured at baseline and 20 min after OLA implementation (post-OLA). Esophageal pressure was used for lung and chest wall elastance partitioning. The tomographic lung image obtained at the fifth intercostal space by EIT was divided in two ventral and two dorsal regions of interest (ROIventral and ROIDorsal). Fifteen consecutive patients were studied. The OLA increased arterial oxygen partial pressure/inspired oxygen fraction from 216 ± 13 to 311 ± 19 mmHg (P < 0.001) and decreased elastance of the respiratory system from 29.4 ± 3 cm H2O/l to 23.6 ± 1.7 cm H2O/l (P < 0.01). The driving pressure (airway opening plateau pressure - total positive end-expiratory pressure) decreased from 17.9 ± 1.5 cm H2O pre-OLA to 15.4 ± 2.1 post-OLA (P < 0.05). The tidal volume fraction reaching the dorsal ROIs increased, and consequently the ROIVentral/Dorsal impedance tidal variation decreased from 2.01 ± 0.36 to 1.19 ± 0.1 (P < 0.01). The OLA decreases the driving pressure and improves the oxygenation and lung mechanics in patients with early, mild, diffuse ARDS. EIT is useful to assess the impact of OLA on regional tidal volume distribution.