Umberto Lucangelo

Effect of positive expiratory pressure and type of tracheal cuff on the incidence of aspiration in mechanically ventilated patients in an intensive care unit.

Objective: To test the effects of positive expiratory pressure on the leakage of fluid around cuffs of different tracheal tubes, in mechanically ventilated patients and in a benchtop model. Design: Randomized clinical trial and experimental in vitro study. Setting: Intensive care unit of a university hospital. Patients: Forty patients recovering in the intensive care unit were ventilated in volume-controlled mode. Twenty patients were randomly intubated with Hi-Lo tubes (HL group), whereas the remaining 20 subjects were intubated with SealGuard tubes (SG group). Interventions: Immediately after intubation and cuff inflation with 30 cm H2O, Evans blue was applied onto the cephalic surface of the tracheal tube cuff. A 5-cm H2O positive expiratory pressure was used during the first 5 hrs of stay, and thereafter it was removed. Bronchoscopy verified whether the dye leaked around the cuff. The experiment lasted 12 hrs. Leakage was also tested in vitro with the same tracheal tubes with incremental level of positive expiratory pressure. Measurements and Main Results: At 1 hr, 5 hrs, and thereafter hourly until 12 hrs, bronchoscopy was used to test the presence of dye on the trachea caudal to the cuff. At the fifth hour, two patients of the HL group failed the test. One hour after positive expiratory pressure removal, all subjects in group HL exhibited a dyed lower trachea. On the other hand, one patient in group SG presented a leak at the eighth hour, and at the 12th hour three of them were still sealed. In vitro, the same level of positive expiratory pressure delayed the passage of dye around the cuff; after 30 mins positive expiratory pressure was removed, and in 10 mins all dye leaked only in the Hi-Lo tube. Conclusions: We found that 5 cm H2O positive expiratory pressure was effective in delaying the passage of fluid around the cuffs of tracheal tubes both in vivo and in vitro. The SealGuard tube proved to be more resistant to leakage than Hi-Lo.

Physiologie evaluation of non-invasive pressure support ventilation in trauma patients with acute respiratory failure

ObjectiveTo investigate the effectiveness of noninvasive (face mask) versus invasive (endotracheal tube) equal pressure values on blood gases and respiratory pattern and to evaluate the feasibility of using mask ventilation after the short term physiologic study.DesignOpen, prospective, physiologic study and uncontrolled clinical study.SettingIntensive care unit of a trauma center.Patients22 intubated trauma patients were studied.InterventionsPatients were intubated and ventilated in a pressure support mode (IPSV) of 13.5 ± 1.5 cmH2O and a post end-expiratory pressure (PEEP) of 5.8 ± 2.57 cmH2O. After a T-piece trial to assess patient’s ability to breath spontaneously, patients were switched over to noninvasive pressure support (NIPSV). The pressure levels were set as during IPSV. Blood gases and respiratory parameters were measured during IPSV, during the T-piece trial, and after 1 h of NIPSV After the physiologic study, all patients were asked if they wished to continue on NIPSV. The patient’s subjective compliance with IPSV and NIPSV was measured by means of an arbitrary score. A successful outcome was defined as no need for reintubation.Measurements and resultsIPSV and NIPSV showed no statistical differences for blood gas and respiratory parameters by using the same values of PSV (13 ± 5 vs 12.8 ± 1.7 cmH2O, NS) and PEEP (5.8 ± 2.5 and 5.2 ± 2.2 cmH2O NS). The median length of time on NIPSV was 47 h (range 6 to 144). All patients wished to continue on NIPSV, but 9 patients (40.9 %) were reintubated after 54 ± 54 h. Six of them died after 36 ± 13 days while still on mechanical ventilation. There was no statistically significant difference in compliance score between IPSV and NIPSV.ConclusionsNIPSV is comparable to IPSV in terms of blood gases and respiratory pattern. The clinical uncontrolled study indicates that NIPSV could be used in selected trauma patients.

High-Flow Nasal Interface Improves Oxygenation in Patients Undergoing Bronchoscopy

During bronchoscopy hypoxemia is commonly found and oxygen supply can be delivered by interfaces fed with high gas flows. Recently, the high-flow nasal cannula (HFNC) has been introduced for oxygen therapy in adults, but they have not been used so far during bronchoscopy in adults. Forty-five patients were randomly assigned to 3 groups receiving oxygen: 40 L/min through a Venturi mask (V40, N = 15), nasal cannula (N40, N = 15), and 60 L/min through a nasal cannula (N60, N = 15) during bronchoscopy. Gas exchange and circulatory variables were sampled before (FiO2 = 0.21), at the end of bronchoscopy (FiO2 = 0.5), and thereafter (V40, FiO2 = 0.35). In 8 healthy volunteers oxygen was randomly delivered according to V40, N40, and N60 settings, and airway pressure was measured. At the end of bronchoscopy, N60 presented higher PaO2, PaO2/FiO2, and SpO2 than V40 and N40 that did not differ between them. In the volunteers (N60) median airway pressure amounted to 3.6 cmH2O. Under a flow rate of 40 L/min both the Venturi mask and HFNC behaved similarly, but nasal cannula associated with a 60 L/min flow produced the better results, thus indicating its use in mild respiratory dysfunctions.

Physiologically based indices of volumetric capnography in patients receiving mechanical ventilation

Several indices of ventilatory heterogeneity can be identified from the expiratory CO2 partial pressure or CO2 elimination versus volume curves. The aims of this study were: 1) to analyse several computerizable indices of volumetric capnography in order to detect ventilatory disturbances; and 2) to establish the relationship between those indices and respiratory system mechanics in subjects with normal lungs and in patients with acute respiratory distress syndrome (ARDS), both receiving mechanical ventilation. We studied six normal subjects and five patients with early ARDS mechanically ventilated at three levels of tidal volume (VT). Respiratory system mechanics were assessed by end-expiratory and end-inspiratory occlusion methods, respectively. We determined Phase III slopes, Fletchers efficiency index, Bohrs dead space (VD,Bohr/VT), and the ratio of alveolar ejection volume to tidal volume (VAE/VT) from expiratory capnograms, as a function of expired volume. Differences between normal subjects and ARDS patients were significant both for capnographic and mechanical parameters. Changes in VT significantly altered capnographic indices in normal subjects, but failed to change ventilatory mechanics and VAE/VT in ARDS patients. After adjusting for breathing pattern, VAE/VT exhibited the best correlation with the mechanical parameters. In conclusion, volumetric capnography, and, specifically, the ratio of alveolar ejection volume to tidal volume allows evaluation and monitoring of ventilatory disturbances in patients with adult respiratory distress syndrome.

Influence of prehospital treatment on the outcome of patients with severe blunt traumatic brain injury: a single-centre study

Aim, patients, and methods To compare retrospectively the outcomes of patients with severe traumatic brain injury (Injury Severity Score, ISS total ≥15; the Abbreviated ISS-head, aISShead ≥9) admitted to our Intensive Care Unit by helicopter (helicopter emergency medical service, HEMS group = 89) with those transported by ambulance (GROUND group = 105) from January 2002 to December 2007. Results The groups were comparable for age, Glasgow Coma Scale, ISS total, and aISShead. The preadmission time of the HEMS group was significantly longer as compared with the GROUND group, but the interval from admission to definitive care was significantly shorter. In the prehospital phase, HEMS patients were more aggressively treated, as indicated by a significantly greater number of procedures performed (i.e. tracheal intubation and positioning of intravenous lines) and larger volumes of fluids infused. The overall mortality was lower in the HEMS than in the GROUND patients (21 vs. 25% respectively, P<0.05). The survival with or without only minor neurological disabilities was higher in the HEMS than in the GROUND group (54 vs. 44% respectively, P<0.05); among the survivors, the rate of severe neurological disabilities was lower in the HEMS than in the GROUND group (25 vs. 31%, P<0.05). Conclusion In our experience, aggressive early treatment of patients with severe traumatic brain injury was associated with a better outcome likely because of the prevention of secondary brain injury and a shorter interval elapsing from the trauma to definitive care despite more time spent on the scene by the intervening team.

Lung mechanics at the bedside: make it simple.

Purpose of reviewThe aim of this review is to describe ventilator–patient interaction, employing the equation of motion and the curves obtained by the ventilator. Practitioners confronted with mechanically ventilated patients every day in intensive care units should be able to sort out from all data available from modern ventilators those relevant for choosing a correct ventilatory strategy for each patient. Recent findingsEarly determination of patient–ventilator asynchrony, air-leaks and variation in respiratory parameters is important during mechanical ventilation. A correct evaluation of data, for patient safety and tailored ventilatory strategy becomes mandatory when non-invasive ventilation by helmet or mask is applied. SummaryThe equation of motion is described and dynamic and static respiratory mechanics are analysed to highlight all those data that can influence decision-making in setting mechanical or assisted ventilation in invasively and non-invasively ventilated patients.

Intrapulmonary percussive ventilation improves the outcome of patients with acute exacerbation of chronic obstructive pulmonary disease using a helmet.

Objective:To evaluate the effect of intrapulmonary percussive ventilation (IPV) by mouthpiece during noninvasive positive-pressure ventilation with helmet in patients with exacerbation of chronic obstructive pulmonary disease (COPD). Design:Randomized clinical trial. Setting:General intensive care unit, university hospital. Patients:Forty patients with exacerbation of COPD ventilated with noninvasive positive-pressure ventilation by helmet were randomized to two different mucus clearance strategies: IPV (IPV group) vs. respiratory physiotherapy (Phys group). As historical control group, 40 patients receiving noninvasive positive pressure and ventilated by face mask treated with respiratory physiotherapy were studied. Interventions:Two daily sessions of IPV (IPV group) or conventional respiratory physiotherapy (Phys group). Measurements and Main Results:Physiologic variables were measured at entry in the intensive care unit, before and after the first session of IPV, and at discharge from the intensive care unit. Outcome variables (need for intubation, ventilatory assistance, length of intensive care unit stay, and complications) were also measured. All physiologic variables improved after IPV. At discharge from the intensive care unit, Paco2 was lower in the IPV group compared with the Phys and control groups (mean ± sd, 58 ± 5.4 vs. 64 ± 5.2 mm Hg, 67.4 ± 4.2 mm Hg, p < .01). Pao2/Fio2 was higher in IPV (274 ± 15) than the other groups (Phys, 218 ± 34; control, 237 ± 20; p < .01). In the IPV group, time of noninvasive ventilation (hrs) (median, 25th–75th percentile: 61, 60–71) and length of stay in the intensive care unit (days) (7, 6–8) were lower than other groups (Phys, 89, 82–96; control, 87, 75–91; p < .01; and Phys, 9, 8–9; control, 10, 9–11; p < .01). Conclusions:IPV treatment was feasible for all patients. Noninvasive positive-pressure ventilation by helmet associated with IPV reduces the duration of ventilatory treatment and intensive care unit stay and improves gas exchange at discharge from intensive care unit in patients with severe exacerbation of COPD.

Effects of mechanical load on flow, volume and pressure delivered by high-frequency percussive ventilation.

High-frequency percussive ventilation (HFPV) has proved its unique efficacy in the treatment of acute respiratory distress, when conventional mechanical ventilation (CMV) has demonstrated a limited response. We analysed flow (V(dot)), volume (V) and airway pressure (Paw) during ventilation of a single-compartment mechanical lung simulator, in which resistance (R) and elastance (E) values were modified, while maintaining the selected ventilatory settings of the HFPV device. These signals reveal the physical effect of the imposed loads on the output of the ventilatory device, secondary to constant (millisecond by millisecond) alterations in pulmonary dynamics. V(dot), V and Paw values depended fundamentally on the value of R, but their shapes were modified by R and E. Although peak Paw increased 70.3% in relation to control value, mean Paw augmented solely 36.5% under the same circumstances (maximum of 9.4 cm H2O). Finally, a mechanism for washing gas out of the lung was suggested.

High-frequency percussive ventilation improves perioperatively clinical evolution in pulmonary resection.

Objective:During thoracotomy, positive end-expiratory pressure is applied to the dependent lung and continuous positive airway pressure (CPAP) inflates the nondependent lung to avoid hypoxemia. These methods do not allow the removal of produced secretions. We hypothesized that high-frequency percussive ventilation (HFPV) can improve both conditions and reduce hospital length of stay in these patients. Design:Randomized prospective study. Setting:University Hospital. Patients:Fifty-three consecutive patients undergoing elective pulmonary partial resection were enrolled. Nine were excluded because of surgical reasons. Interventions:The nondependent lung was ventilated with HFPV in 22 patients and other 22 received CPAP. In both groups, the dependent lung was ventilated with continuous mechanical ventilation. Measurement and Main Results:Cardiocirculatory variables and blood gas analysis were measured during surgery. Postoperatively, all patients underwent chest physiotherapy, and Spo2, body temperature, the amount of sputum produced, and chest radiography were recorded. Before nondependent lung re-expansion, HFPV patients presented higher Pao2 than CPAP group (p = 0.020). The amount of secretions was higher in chronic obstructive pulmonary disease patients treated with HFPV than in those who received CPAP (199 and 64 mL, respectively, p = 0.028). HFPV increased by 5.28 times the chance of sputum production by chronic obstructive pulmonary disease patients (&khgr;2 = 46.66, p < 0.0001; odds ratio = 5.28). A patient treated with HFPV had a 3.14-fold larger chance of being discharged earlier than a CPAP-treated subject (likelihood ratio = 11.5, p = 0.0007). Conclusions:Under the present settings, HFPV improved oxygenation in one-lung ventilation during pulmonary resection. Postoperatively, it decreased the length of stay and increased the removal of secretions in comparison with CPAP.

Static pressure-volume curves of the respiratory system: were they just a passing fad?

Purpose of reviewThe aim of this article is to describe the physiologic utility, correlation with lung morphology, difficulties in interpretation and current clinical applications of static respiratory system pressure–volume curves at the bedside in patients with acute lung injury or acute respiratory distress syndrome. Recent findingsComplex interpretation of pressure–volume curves indicates that alveolar reopening continues past the lower inflection point on the linear part of the curve and suggests the presence of homogeneous lung disease in which recruitment is still possible by positive end-expiratory pressure application. Setting positive end-expiratory pressure above the lower inflection point and tidal ventilation (approximately 6 ml/kg) in the linear portion of the respiratory system pressure–volume curve improved mortality and ameliorated lung and plasma inflammatory mediators compared with ventilation with the lowest positive end-expiratory pressure at traditional tidal volumes. Recent studies have found that regular use of pressure–volume curves provides useful physiological data that help to optimize mechanical ventilation at the bedside. SummaryThe physiologic data obtained by measuring the static pressure–volume curves have helped clinicians to better understand the behavior of the respiratory system when positive-pressure ventilation is applied. The advanced technology incorporated into modern ventilators allows routine measurement of pressure–volume curves under sedation without paralysis, with acceptable variability and no serious adverse effects.