M. Bufi

Propofol induces bronchodilation in mechanically ventilated chronic obstructive pulmonary disease (COPD) patients

The aim of this study was to evaluate the effects of propofol administration (2 mg · kg‐1 i.v.) on the airways resistances and respiratory mechanics of patients affected by COPD exacerbation, requiring mechanical ventilation. Twenty patients required anaesthesia for diagnostic or therapeutic procedures. Fourteen consecutive patients were divided at random into two groups: Group P received propofol and Group C (control) received only Intralipid 10%; an additional group of six patients received i.v. flunitrazepam (0.03 mg · kg‐1). Lung mechanics (dynamic and static compliance, peak inspiratory pressure, intrinsic positive and expiratory pressure, minimal and maximal resistances of the respiratory system) were evaluated in basal conditions and 3 and 6 min after propofol, Intralipid or flunitrazepam administration. We did not observe significant variations of the evaluated variables after Intralipid or flunitrazepam (Groups C and F), while in patients who received propofol (Group P), we observed the following modifications: dynamic compliance increased from 2.3 ± 0.3 to 2.8 ± 0.4 ml · kPa‐1 (P<0.05), peak inspiratory pressure decreased from 3.3 ± 0.7 to 2.8 ± 0.4 kPa (P <0.05), minimal resistances of the respiratory system (that mainly reflect airways resistances) decreased from 1 ± 0.2 to 0.7 ± 0.2 kPa · 1‐1 · s‐1 (P <0.01). Our results suggest that propofol induces bronchodilation in mechanically ventilated COPD patients, and that this effect is not related specifically to the induction of general anesthesia.

Preimplantation retrograde pneumoplegia in clinical lung transplantation

Abstract Objective: Retrograde pneumoplegia seems to improve early graft function in experimental and clinical lung transplantation. We evaluated the role of retrograde flushing in addition to antegrade pneumoplegia in clinical lung transplantation. Methods: Fourteen patients undergoing lung transplantation were randomized into 2 groups: in group I we performed antegrade pulmonary artery flushing with alprostadil (prostaglandin E 1 ) and modified Euro-Collins solution at the time of retrieval. In group II additional retrograde flushing through the pulmonary veins was performed at the back table, before reimplantation. Hemodynamic variables, mean airway pressure, and blood gas analysis were monitored at different time points. Postoperative volumetric monitoring was performed to assess extravascular lung water. The reimplantation response was assessed by a radiographic score; extubation time and intensive care unit stay were recorded. Results: During retrograde flushing, blood and clots coming out from the pulmonary artery were observed; 2 lungs harvested from a donor with multiple bone fractures had fat emboli in the retrograde perfusate. Hemodynamic monitoring did not demonstrate any difference between the 2 groups. The ratio of arterial oxygen tension to inspired oxygen fraction, extravascular lung water, duration of intubation, and length of stay in the intensive care unit were improved in group II, but the differences did not reach statistical significance. Intrapulmonary shunt fraction was significantly improved in group II at each time point ( P = .02), as well as indexed alveolar-arterial oxygen tension gradient ( P = .04), mean airway pressure ( P = .04), and chest x-ray score ( P = .03). Conclusions: Preimplantation retrograde flushing is not detrimental and helps to improve early graft function. (J Thorac Cardiovasc Surg 1999;118:107-14)

Effects of the heat-moisture exchangers on dynamic hyperinflation of mechanically ventilated COPD patients

In recent years the use of devices called Heat and Moisture Exchangers (HME) has become widespread as gas conditioners for ICU patients requiring mechanical ventilation. As an important variation of the resistive properties of the HME, related to flow and duration of use, has recently been pointed out during “in vitro” studies, the use of these devices in COPD patients could increase the levels of auto PEEP and dynamic hyperinflation. In this study we have compared the levels of auto PEEP and difference in functional residual capacity (Δ FRC) in a group of COPD patients, requiring controlled mechanical ventilation (CMV), at basal conditions and after the insertion into the circuit of three HMEs (Dar Hygrobac, Pall Ultipor, Engstrom Edith) at random: the results obtained excluded a significant increase of auto PEEP and Δ (FRC) both with “new” HMEs and after 12 h of continuous use.

Detection of leukotrienes B4, C4 and of their isomers in arterial, mixed venous blood and bronchoalveolar lavage fluid from ARDS patients

Seven patients with the adult respiratory distress syndrome (ARDS) were studied. As a control group we used 6 surgical patients who underwent minor surgical operation (inguinal hernia). For both groups the same sample collection and analysis was used. The presence of leuktorienes (LTs) B4 and C4 and of their isomers 11-trans LTC4 and Δ6-trans-12-epi LTB4 was determined in arterial, mixed venous blood and in bronchoalveolar lavage (BAL) fluid. The samples, analysed by reverse phase high performance liquid chromatography (RP-HPLC), showed a similar chromatographic picture among ARDS patients, while the control group showed no detectable amounts of LTs in BAL or blood. The distribution of these arachidonic acid metabolites in mixed venous blood, arterial blood and BAL seems to suggest pulmonary metabolism and/or inactivation. It is suggested that these mediators act as humoral factors in pathogenesis of the ARDS.

Evaluation of respiratory system resistance in mechanically ventilated patients: The role of the endotracheal tube

ObjectiveTo investigate the role played by the endotracheal tube (ETT) in the correct evaluation of respiratory system mechanics with the end inflation occlusion method during constant flow controlled mechanical ventilation.SettingGeneral ICU, university of Rome “La Sapienza”.Patients12 consecutive patients undergoing controlled mechanical ventilation.MethodsWe compared the values of minimal resistance of the respiratory system (i.e. airway resistance) (RRS min) obtained: i) subtracting the theoretical value of ETT resistance from the difference between P max and P1, measured on airway pressure tracings obtained from the distal end of the ETT; ii) directly measuring airway pressure 2 cm below the ETT, thus automatically excluding ETT resistance from the data.ResultsThe values of RRS min obtained by measuring airway pressure below the ETT were significantly lower than those obtained by measuring airway pressure at the distal end of the ETT and subtracting the theoretical ETT resistance (4.5±2.8 versus 2.5±1.6 cm H2O/l/s,p<0.01).ConclusionWhen precise measurements of ohmic resistances are required in mechanically ventilated patients, the measurements must be obtained from airways pressure data obtained at tracheal level. The “in vivo” positioning of ETT significantly increases the airflow resistance of the ETT.

Respiratory system mechanics in the early phase of acute respiratory failure due to severe kyphoscoliosis

Objective: To evaluate respiratory mechanics in the early phase of decompensation in a group of seven patients with severe kyphoscoliosis (KS) (Cobb angle > 90 °) requiring mechanical ventilatory support. Design: Prospective clinical study with a control group. Setting: General intensive care unit at University of Rome “La Sapienza”. Patients: Seven consecutive patients affected by severe KS in the early phase of acute decompensation and a control group of six ASA (American Society of Anesthesiology) 1 subjects who were mechanically ventilated during minor surgery. Measurements and results: Respiratory mechanics were evaluated during constant flow-controlled mechanical ventilation at zero end-expiratory pressure with the end-inspiratory and end-expiratory occlusion technique. In five patients who showed increased ohmic resistance (RRSmin), we evaluated the possibility of reversing this increase with a charge dose of 6 mg/kg doxophylline i. v. In four KS patients, in whom a reliable esophageal pressure was confirmed by a positive occlusion test, we separated respiratory system data into lung and chest wall component. All KS patients showed reduced values of respiratory compliance (CRS) and increased respiratory resistance (RRS). The average basal values of CRS were 36 ± 10 vs 58 ± 8.5 cmH2O in control patients; RRSmax was 20 ± 3.1 vs. 4.5 ± 1.2 cmH2O/l per s; RRSmin 6.2 ± 1.2 vs. 2 ± 0.5 cmH2O/l per s: ΔRRS 14 ± 2.6 cmH2O vs 2.4 ± 0.7 cmH2O/l per s. All KS patients showed low values of intrinsic positive end-expiratory pressure (PEEPi) (1.8 ± 1.5 cmH2O). Separation of lung and chest-wall mechanics, performed only in four patients, showed a reduction in both lung (66.7 ± 7.2 ml/cmH2O) and chest wall values (84 ± 8.2 ml/cmH2O), while both RmaxL and RmaxCW were increased (16.6 ± 2 and 2.8 ± 0.4 cmH2O/l per s, respectively). Infusion of doxophylline did not significantly change respiratory mechanics when evaluated 15, 30, and 45 min after the infusion. Conclusions: During acute decompensation, both lung and chest-wall compliance are severely reduced in KS patients: conversely, and, contrary to that in patients with chronic obstructive pulmonary disease, increases in airway resistance and PEEPi seem to play only a secondary role.

A new device to remove obstruction from endotracheal tubes during mechanical ventilation in critically ill patients

ObjectiveTo evaluate the efficiency of a new device developed to remove obstructions from endotracheal tubes (ETT) in mechanically ventilated patients.DesignOpen study in mechanically ventilated sedated and paralyzed ICU patients.SettingGeneral ICU and Laboratory of Respiratory Mechanics of the University of Rome “La Sapienza”.Patients8 consecutive unselected mechanically ventilated, critically ill patients in which a partial obstruction of ETT was suspected on the basis of an increase of the peak inspiratory pressure (>20%) plus the difficult introduction of a standard suction catheter.InterventionsObstructions to ETT were removed with an experimental “obstruction remover” (OR)Measurements“In vivo” ETT airflow resistance (0.25; 0.5; 0.75; 1l/s) was evaluated before and after use of the OR; the work of breathing necessary to overcome ETT resistance (WOBett) was also evaluated before and after OR use.ResultsThe use of OR significantly reduced in all patients the ETT “in vivo” resistance (From 5.5±2.3 to 2.9±0.5 cmH2O/l/s at 0.25l/s,p<0.05; from 9±2.4 to 3.8±0.8 cmH2O/l/s at 0.51l/s; from 12.2±3.5 to 5.7±1.2 cmH2O/l/s at 0.75l/s; from 16.9±6 to 9.3±3.8 cmH2O/l/s at 1l/s,p<0.01 respectively). Also the WOBett was significantly reduced after use of the OR (from 0.66±0.19 to 0.34±0.08 J/l;p<0.05)ConclusionThis experimental device can be safely and successfully used to remove obstructions from the ETT lumen, without suspending mechanical ventilation, reducing the need for rapid ETT substitution in emergency and life-threatening situations.

Pressure support ventilation (PSV) reverses hyperinflation induced isorhythmic A-V dissociation

We report a case of hyperinflation induced isorythmic atrio-ventricular dissociation with circulatory failure in a patient with chronic obstructive pulmonary disease. The arrythmia was successfully treated by applying “pressure support ventilation” (PSV: 20 cmH2O) which, by decreasing the respiratory rate and increasing the expiratory time reduced the level of auto-PEEP. In order to explain this result the Authors recorded, in the same patient, the level of auto-PEEP and ΔFRC obtained with Intermittent Positive Pressure Ventilation (IPPV), Intermittent Mandatory Ventilation (IMV) and PSV at the same gas exchange values. PSV showed a dramatic reduction of both these parameters. (Auto-PEEP: IPPV 12 cmH2O, IMV 17 cmH2O, PSV 7 cmH2O).

TUMOR-NECROSIS-FACTOR IN SERUM AND IN BRONCHOALVEOLAR LAVAGE OF PATIENTS AT RISK FOR THE ADULT RESPIRATORY-DISTRESS SYNDROME

Tumor necrosis factor-alpha (TNF) production was analyzed in 30 mechanically ventilated patients at high risk for the adult respiratory distress syndrome (ARDS) as defined by the presence of septic syndrome or following multiple trauma. Ten patients mechanically ventilated with acute cerebral hemorrhage were studied as a control group. Serum samples were drawn on entry into the study every 30 minutes for 90 minutes (0hr), 24 hours (24hr), and 48 hours (48hr) after enrollment. Bronchoalveolar lavage (BAL) was performed on the first and third day serum and BAL fluid were essayed for TNF content. No detectable amount of TNF was observed in 10 nonseptic controls. Production of TNF did not vary over the study period and was observed not only in patients with septic syndrome but also in patients without sepsis. Tumor necrosis factor did not correlate with mortality, severity of illness, and clinical parameters. Patients developing ARDS showed a significantly higher concentration of TNF in BAL than in serum (96 ± 25v 28 ± 27 pg/mL at 0hr; 91 ± 29 v 22 ± 25 pg/mL at 48hr; P < .05). These data support the concept of local pulmonary production of this cytokine in ARDS.

Differential evaluation of bronchoalveolar lavage cells and leukotrienes in unilateral acture lung injury and ARDS patients

Patients with unilateral acute lung injury (UALI; n=6) and ARDS (n=4) were evaluated by bronchoalveolar lavage, as controls we used 5 patients suffering from cerebral hemorrhage and without pulmonary, cardiac or infectious disease who were mechanically ventilated. For each group of patients two independent bronchoalveolar lavages (BAL) were performed. The BAL fluid recovered from the two lungs was immediately analyzed for leukotrienes (LTS) by means of RP-HPLC and stained for cell counts. The BAL from the control group did not show any LTS and the percentage of neutrophils was within the normal range: 1±0.2% right lung and 1.2±0.4% left lung. The BAL fluid from UALI patients showed two different patterns, the injured lung showed high levels of LTS (39.1±8 ng ml-1 LTB4; 25±6 ng ml-1 LTD4 and 27.8±8.2 ng ml-111-trans LTC4) and an increased percentage of neutrophils (74.2±7%) compared to controls. Only 2 out of the 6 patients from the UALI group showed small amounts of LTB4 (4 ng ml-1) and LTD4 (3.2 ng ml-1). The BAL obtained from the “healthy lung” in both cases showed values of LTS almost eight fold lower than those present in the injured lung. The percentage of neutrophils from the unaffected lungs (4.3±7%) was not significantly different from controls. Lavage fluid from ARDS patients showed a similar picture to that of the affected lung from UALI patients. Evaluation of ARDS lavage fluid demonstrated the presence of the same LTS (LTB4, LTD4 and 11-trans LTC4) with concentrations similar to those found in the injured lung of UALI subjects. The amount of LTB4 (a very potent chemotatic factor) correlated directly with the percentage of neutrophils both in ARDS and the diseased lung of UALI patients. These findings suggest that LTS and neutrophils participate in the pathophysiology of UALI and ARDS, and that UALI is a localized pathologic entity similar to ARDS.