Antonio Braschi

Respiratory response and inspiratory effort during pressure support ventilation in COPD patients

ObjectivePressure Support Ventilation (PSV) is now widely used in the process of weaning patients from mechanical ventilation. The aim of this study was to evaluate the effects of various levels of PS on respiratory pattern and diaphragmatic efforts in patients affected by chronic obstructive pulmonary disease (COPD).SettingIntermediate intensive care unit.PatientsWe studied ten patients undergoing PSV and recovering from an episode of acute respiratory failure due to exacerbation of COPD.MethodsThree levels of PSV were studied, starting from the lowest (PSb) one at which it was possible to obtain an adequate Vt with a pH≥7.32 and an SaO2>93%. Then, PS was set at 5 cmH2O above (PSb+5) and below (PSb-5) this starting level. Ventilatory pattern, transdiaphragmatic pressure (Pdi), the pressure-time product of the diaphragm (PTPdi), the integrated EMG of the diaphragm, static PEEP (PEEPi, stat), dynamic PEEP (PEEPi, dyn), and the static compliance and resistance of the total respiratory system were recorded.ResultsMinute ventilation did not significantly change with variations in the level of PS, while Vt significantly increased with PS (PS−5=6.3±0.5 ml/kg vs. PSb=10.1±0.9 [p<0.01] and vs. PS+5=11.7±0.6 [p<0.01]), producing a reduction in respiratory frequency with longer expiratory time. The best values of blood gases were obtained at PSb, while at PSb−5, PaCO2 markedly increased. During PSb and PSb+5 and to a lesser extent during PSb−5, most of the patients made several inspiratory efforts that were not efficient enough to trigger the ventilator to inspire; thus, the PTPdi “wasted” during these inefficient efforts was increased, especially during PS+5. The application of an external PEEP (PEEPe) of 75% of the static intrinsic PEEP during PSb caused a significant reduction in the occurrence of these inefficient efforts (p<0.05). Minute ventilation remained constant, but Vt decreased, together with Te, leaving the blood gases unaltered. The PTPdi per breath and the dynamic PEEPi were also significantly reduced (by 59% and 31% of control, respectively,p<0.001) with the application of PEEPe.ConclusionWe conclude that in COPD patients, different levels of PSV may induce different respiratory patterns and gas exchange. PS levels capable of obtaining a satisfactory equilibrium in blood gases may result in ineffective respiratory efforts if external PEEP is not applied. The addition of PEEPe, not exceeding dynamic intrinsic PEEP, may also reduce the metabolic work of the diaphragm without altering gas exchange.

Long-term durable benefit after whole lung lavage in pulmonary alveolar proteinosis

Whole lung lavage (WLL) is still the gold-standard therapy for pulmonary alveolar proteinosis (PAP). The few studies on the duration of the effect of WLL, belonging to a rather remote period, show significant but transient benefits. In 21 patients with idiopathic PAP, the duration of any benefit and, in 16 of them, the time course of lung function improvement (at baseline, 1 week, 6 months, 1 yr and then every 2 yrs after WLL) were evaluated. The present WLL technique takes longer, is invasively monitored and partially modified with respect to past techniques. More than 70% of patients remained free from recurrent PAP at 7 yrs. The bulk of the improvement in spirometric results was almost completely gained in the immediate post‐WLL period due to the efficient clearance of the alveoli. At a median of 5 yrs, recovery of diffusing capacity of the lung for carbon monoxide was incomplete (75±19% of the predicted value) and there were residual gas exchange abnormalities (alveolar to arterial oxygen tension difference 3.6±1.5 kPa (27±11 mmHg)) and exercise limitation, probably explained by engorgement of lymphatic vessels. In conclusion, whole lung lavage for idiopathic pulmonary alveolar proteinosis is currently a safe procedure in an experienced setting, and provides long-lasting benefits in the majority of patients.

Respiratory mechanics by least squares fitting in mechanically ventilated patients: Applications during paralysis and during pressure support ventilation

ObjectiveTo evaluate a least squares fitting technique for the purpose of measuring total respiratory compliance (Crs) and resistance (Rrs) in patients submitted to partial ventilatory support, without the need for esophageal pressure measurement.DesignProspective, randomized study.SettingA general ICU of a University Hospital.Patients11 patients in acute respiratory failure, intubated and assisted by pressure support ventilation (PSV).InterventionsPatients were ventilated at 4 different levels of pressure support. At the end of the study, they were paralyzed for diagnostic reasons and submitted to volume controlled ventilation (CMV).Measurements and resultsA least squares fitting (LSF) method was applied to measure Crs and Rrs at different levels of pressure support as well as in CMV. Crs and Rrs calculated by the LSF method were compared to reference values which were obtained in PSV by measurement of esophageal pressure, and in CMV by the application of the constant flow, end-inspiratory occlusion method. Inspiratory activity was measured by P0.1. In CMV, Crs and Rrs measured by the LSF method are close to quasistatic compliance (−1.5±1.5 ml/cmH2O) and to the mean value of minimum and maximum end-inspiratory resistance (+0.9±2.5 cmH2O/(l/s)). Applied during PSV, the LSF method leads to gross underestimation of Rrs (−10.4±2.3 cmH2O/(l/s)) and overestimation of Crs (+35.2±33 ml/cmH2O) whenever the set pressure support level is low and the activity of the respiratory muscles is high (P0.1 was 4.6±3.1 cmH2O). However, satisfactory estimations of Crs and Rrs by the LSF method were obtained at increased pressure support levels, resulting in a mean error of −0.4±6 ml/cmH2O and −2.8±1.5 cmH2O/(l/s), respectively. This condition was coincident with a P0.1 of 1.6±0.7 cmH2O.ConclusionThe LSF method allows non-invasive evaluation of respiratory mechanics during PSV, provided that a near-relaxation condition is obtained by means of an adequately increased pressure support level. The measurement of P0.1 may be helpful for titrating the pressure support in order to obtain the condition of near-relaxation.

Unfavorable mechanical effects of heat and moisture exchangers in ventilated patients

Objective: To investigate the mechanical effects of artificial noses. Setting: A general intensive care unit of a university hospital. Patients: 10 patients in pressure support ventilation for acute respir

Epidural Local Anesthetic Plus Corticosteroid for the Treatment of Cervical Brachial Radicular Pain: Single Injection Versus Continuous Infusion

BackgroundEfficacy of epidural local anesthetics plus steroids for the treatment of cervicobrachial pain is uncertain. MethodsA prospective study randomized 160 patients with cervicobrachial pain resistant to conventional therapy. Patients were divided into 4 groups on the basis of the time between pain onset and treatment initiation: group A, 40 patients with pain onset 15 to 30 days; group B, 40 patients with pain from 31 to 60 days; group C, 40 patients, 61 to 180 days; and group D, 40 patients with pain >180 days. Patients of each group were randomized to receive an epidural block with bupivacaine and methylprednisolone at intervals of 4 to 5 days (Single injection) or continuous epidural bupivacaine every 6, 12, or 24 hours plus methylprednisolone every 4 to 5 days (Continuos epidural). The maximum duration of treatment (9 blocks in Single injection, and 30 days in Continuos epidural) was dependent on achieving Pain Control (PC) ≥80% [PC is defined by this formulae: (100) (VASinitial−VASfinal)/VASinitial]. Follow-up at 1 month and 6 months compared PC and the number of pain-free hours of sleep. ResultsOne hundred forty-one patients completed the study. The 4 groups had similar characteristics. At the 1-month and 6-month follow-up analysis based on the time between pain onset and treatment initiation showed that patients of group D, who received the Continuous epidural treatment, had significantly greater PC and significantly more pain-free hours of sleep compared with similar patients in Single injection. ConclusionsTherapy with continuous epidural local anesthetic and methylprednisolone provides better control of chronic cervicobrachial pain compared with Single injection. These results are discussed with respect to the possible mechanism of action of the drugs and may relate to the physiopathologic mechanisms associated with neuronal plasticity that result in chronic pain.

Inhaled nitric oxide therapy in adults: European expert recommendations.

BackgroundInhaled nitric oxide (iNO) has been used for treatment of acute respiratory failure and pulmonary hypertension since 1991 in adult patients in the perioperative setting and in critical care.MethodsThis contribution assesses evidence for the use of iNO in this population as presented to a expert group jointly organised by the European Society of Intensive Care Medicine and the European Association of Cardiothoracic Anaesthesiologists.ConclusionsExpert recommendations on the use of iNO in adults were agreed on following presentation of the evidence at the expert meeting held in June 2004.

Whole lung lavage: a unique model for ultrasound assessment of lung aeration changes

PurposeWhole lung lavage (WLL) pathophysiologically represents a human model of controlled lung de-aeration, resembling various pathological conditions encountered in the critically ill. Through one-lung ventilation and progressive alveolar flooding, it mimics, respectively, re-absorption atelectasis formation and lung consolidation. With re-ventilation of the treated lung, PEEP application and diuretics administration, it then creates a model of pulmonary edema and its progressive resolution. No studies have so far described lung aeration changes during WLL with ultrasound: objectives of the study were to describe ultrasound findings during WLL with validated semiotics in the critically ill and to investigate their relation with the lung’s state of relative aeration.MethodsIn seven patients, 12 lung areas/patient were prospectively studied with ultrasound during six procedural steps of WLL. A three-tiered pattern classification was assigned (1, normal/nearly normal; 2, alveolar-interstitial syndrome; 3, alveolar consolidation) consistently with their previously described meaning in terms of relative air content. The distribution was compared throughout different WLL maneuvers as it was for arterial oxygen measurement distribution.ResultsDuring one-lung ventilation and saline flooding, ultrasound findings shifted from artifact patterns (normal/nearly normal and alveolar-interstitial syndrome) to alveolar consolidation. Saline removal, re-ventilation and negative water balance were associated with a gradual return to alveolar-interstitial syndrome, then to a normal/nearly normal pattern. Arterial oxygen tension variations were not always consistent with these changes.ConclusionsIn a controlled human model of lung air content variation, the different states of aeration determined by WLL procedure were reliably described with lung ultrasound.

Organ Allocation Waiting Time During Extracorporeal Bridge to Lung Transplant Affects Outcomes

BACKGROUND The use of extracorporeal membrane oxygenation (ECMO) as a bridge to lung transplant (LTX) is still being debated. METHODS We performed a retrospective two-center analysis of the relationship between ECMO bridging duration and survival in 25 patients. Further survival analysis was obtained by dividing the patients according to waiting time on ECMO: up to 14 days (Early group) or longer (Late group). We also analyzed the impact of the ventilation strategy during ECMO bridging (ie, spontaneous breathing and noninvasive ventilation [NIV] or intubation and invasive mechanical ventilation [IMV]). RESULTS Seventeen of 25 patients underwent a transplant (with a 76% 1-year survival), whereas eight patients died during bridging. In the 17 patients who underwent a transplant, mortality was positively related to waiting days until LTX (hazard ratio [HR], 1.12 per day; 95% CI, 1.02-1.23; P = .02), and the Early group showed better Kaplan-Meier curves (P = .02), higher 1-year survival rates (100% vs 50%, P = .03), and lower morbidity (days on IMV and length of stay in ICU and hospital). During the bridge to transplant, mortality increased steadily with time. Considering the overall outcome of the bridging program (25 patients), bridge duration adversely affected survival (HR, 1.06 per day; 95% CI, 1.01-1.11; P = .015) and 1-year survival (Early, 82% vs Late, 29%; P = .015). Morbidity indexes were lower in patients treated with NIV during the bridge. CONCLUSIONS The duration of the ECMO bridge is a relevant cofactor in the mortality and morbidity of critically ill patients awaiting organ allocation. The NIV strategy was associated with a less complicated clinical course after LTX.

Closed-loop control of airway occlusion pressure at 0.1 second (P0.1) applied to pressure-support ventilation: algorithm and application in intubated patients.

OBJECTIVE Airway occlusion pressure at 0.1 sec (P0.1) is an index of respiratory center output. During pressure-support ventilation, P0.1 correlates with the mechanical output of the inspiratory muscles and has an inverse relationship with the amount of pressure-support ventilation. Based on these observations, we designed a closed-loop control which, by automatically adjusting pressure-support ventilation, stabilizes P0.1, and hence patient inspiratory activity, at a desired target. The purpose of the study was to demonstrate the feasibility of the method, rather than its efficacy or even its influence on patient outcome. DESIGN Prospective, randomized trial. SETTING A general intensive care unit of a university hospital in Italy. PATIENTS Eight stable patients intubated and ventilated with pressure-support ventilation for acute respiratory failure. INTERVENTIONS Patients were transiently connected to a computer-controlled ventilator on which the algorithm for closed-loop control was implemented. The closed-loop control was based on breath by breath measurement of P0.1, and on comparison with a target set by the user. When actual P0.1 proved to be higher than the target value, the P0.1 controller automatically increased pressure-support ventilation, and decreased it when P0.1 proved to be lower than the target value. For safety, a volume controller was also implemented. Four P0.1 targets (1.5, 2.5, 3.5, and 4.5 cm H2O) were applied at random for 15 mins each. MEASUREMENTS AND MAIN RESULTS The closed-loop algorithm was able to control P0.1, with a difference from the set targets of 0.59 +/- 0.27 (SD) cm H2O. CONCLUSIONS The study shows that P0.1 can be automatically controlled by pressure-support ventilation adjustments with a computer. Inspiratory activity can thus be stabilized at a level prescribed by the physician.

Equipment review: Mechanical effects of heat-moisture exchangers in ventilated patients

Although they represent a valuable alternative to heated humidifiers, artificial noses have unfavourable mechanical effects. Most important of these is the increase in dead space, with consequent increase in the ventilation requirement. Also, artificial noses increase the inspiratory and expiratory resistance of the apparatus, and may mildly increase intrinsic positive end-expiratory pressure. The significance of these effects depends on the design and function of the artificial nose. The pure humidifying function results in just a moderate increase in dead space and resistance of the apparatus, whereas the combination of a filtering function with the humidifying function may critically increase the volume and the resistance of the artificial nose, especially when a mechanical filter is used. The increase in the inspiratory load of ventilation that is imposed by artificial noses, which is particularly significant for the combined heat-moisture exchanger filters, should be compensated for by an increase either in ventilator output or in patients work of breathing. Although both approaches can be tolerated by most patients, some exceptions should be considered. The increased pressure and volume that are required to compensate for the artificial nose application increase the risk of barotrauma and volutrauma in those patients who have the most severe alterations in respiratory mechanics. Moreover, those patients who have very limited respiratory reserve may not be able to compensate for the inspiratory work imposed by an artificial nose. When we choose an artificial nose, we should take into account the volume and resistance of the available devices. We should also consider the mechanical effects of the artificial noses when setting mechanical ventilation and when assessing a patients ability to breathe spontaneously.