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Biomedical subjects

L Brochard

Publications and source records attributed to L Brochard.

At least 109 records · Page 6Linked to original sources
PubMed1994

Acoustic method to estimate the longitudinal area profile of endotracheal tubes.

A problem in mechanical ventilation is the accumulation of mucus secretions in the endotracheal tube (ETT), which tends to reduce the patent cross-sectional area. Here we characterized the extent and locus of the ETT obstruction using an acoustic reflection method recently modified to be applied at bedside. Experiments were conducted both in vivo in 10 intubated patients and in vitro in ETT with or without known constrictions of 1 to 3 mm over 5 cm, located at various distances from the ETT entry: 5, 10, 15, and 20 cm. Acoustic results were compared with the results obtained by an hydraulic reference method, which was the only method available to measure ETT obstruction in mechanically ventilated patients. In vivo acoustic results showed that area reductions were maximal near the tracheal extremity of the ETT, with a range from 2 to 36% (mean value 13 +/- 10%), when estimated relative to the area measured in an unused ETT of the same inner diameter (7 to 9 mm). Statistical analysis of the differences between acoustic reflection data and hydraulic data showed that the two methods did not differ significantly. In vitro acoustic results obtained in constricted ETT showed a highly significant correlation with the actual area (r = 0.97, p = 0.0001). Thus, reductions in ETT area may be detected, quantified, and located by the present acoustic reflection method, which therefore provides a means to avoid emergency extubation because of ETT obstruction.

Acoustics↗
PubMed1994

Nebulized versus intravenous albuterol in hypercapnic acute asthma. A multicenter, double-blind, randomized study.

In a multicenter, randomized, double-blind study, we compared the effects of nebulized (5 mg x 2) and intravenous (0.5 mg) albuterol (salbutamol) over 1 h in 47 patients admitted to hospital with severe acute asthma defined as a peak expiratory flow (PEF) below 150 L/min and hypercapnia (Pa(CO2) > or = 40 mm Hg). Additional treatment included nasal oxygen and hydrocortisone succinate. The efficacy was assessed after 1 h. In the group treated by nebulization (NEB group, n = 22) 19 (86%) patients (95% confidence interval: 65 to 97%) had been treated successfully according to predefined criteria, versus 12 (48%) patients (95% confidence interval: 28 to 69%) in the intravenously treated group (i.v. group, n = 25), p = 0.006. The mean increase in PEF was greater in the NEB group than in the i.v. group (+107 +/- 94 L/min versus +42 +/- 66 L/min, p = 0.01) as well as the decrease in Pa(CO2) values (-10 +/- 5 mm Hg versus -2 +/- 12 mm Hg, p < 0.01). Beta agonist-induced hypokalemia was more pronounced in the i.v. group than in the NEB group. We conclude that, in hypercapnic acute asthma, the nebulized route has a greater efficacy and fewer side effects than the intravenous route.

Acute Disease↗
PubMed1994

Comparison of three methods of gradual withdrawal from ventilatory support during weaning from mechanical ventilation.

Several modalities of ventilatory support have been proposed to gradually withdraw patients from mechanical ventilation, but their respective effects on the outcome of weaning from mechanical ventilation are not known. We conducted a randomized trial in three intensive care units in mechanically ventilated patients who met standard weaning criteria. Those who could not sustain 2 h of spontaneous breathing were randomly assigned to be weaned with T-piece trials, with synchronized intermittent mandatory ventilation (SIMV), or with pressure support ventilation (PSV). Specific criteria for performing tracheal extubation were defined for each modality. The number of patients who could not be separated from the ventilator at 21 d (i.e., who failed to wean) was compared between the groups. Patients in whom tracheal intubation was required in a 48-h period following extubation were also classified as failures. Among 456 mechanically ventilated patients who met weaning criteria, 109 entered into the study (35 with T piece, 43 with SIMV, and 31 with PSV). The three groups were comparable in terms of etiology of disease or characteristics at entry in the study. When all causes for weaning failure were considered, a lower number of failures was found with PSV than with the other two modes, with the difference just reaching the level of significance (23% for PSV, 43% for T piece, 42% for SIMV; p = 0.05). After excluding patients whose weaning was terminated for complications unrelated to the weaning process, the difference became highly significant (8% for PSV versus 33% and 39%, p < 0.025).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Bronchoalveolar lavage during neutropenic episodes: diagnostic yield and cellular pattern.

Few data are available concerning the relationship between alveolar and blood cell populations during neutropenia. We wanted to compare the value of pulmonary endoscopic procedures with lavage in neutropenic (polymorphonuclear (PMN) count < or = 1,000.mm-3) and non-neutropenic settings. We therefore, retrospectively, reviewed the results of 118 investigations for pneumonia in patients with malignant haematological diseases. All had bronchoalveolar lavage (BAL), and some had additional studies with protected bacteriological samples. Each BAL specimen was studied after cytocentrifugation by cytological examination for opportunistic infections, haemorrhage, virus, legionellae, and bacteriological cultures. The diagnostic yield of all endoscopic procedures (BAL, telescoping plugged catheter and protected specimen brush) was 53% in neutropenic (Group 1) and 61% in non-neutropenic (Group 2) patients. The aetiological pattern of pneumonia was nearly the same in the two groups, except for more alveolar proteinosis in Group 1 and more cytomegalovirus (CMV) in Group 2. The absolute number of alveolar cells recovered through BAL (total number, macrophages, lymphocytes and PMNs) was significantly lower in neutropenic patients. We conclude that: 1) neutropenic patients with pneumonia require the same investigative approach as non-neutropenic patients; 2) profound neutropenia may be concomitant with a decreased cellularity of alveoli, which may reflect the consequences of marrow aplasia on the pulmonary cell population and/or direct effect of chemotherapy on the lung.

Adolescent↗
PubMed1994

Effects of pressure-controlled with different I:E ratios versus volume-controlled ventilation on respiratory mechanics, gas exchange, and hemodynamics in patients with adult respiratory distress syndrome.

BACKGROUND: Pressure-controlled (PCV) and pressure-controlled inverse ratio ventilation (PCIRV) have been proposed instead of volume-controlled conventional ratio ventilation (VC) with positive end-expiratory pressure (PEEP) for patients with adult respiratory distress syndrome (ARDS). The advantages advocated with the use of PCIRV are to decrease airway pressures and to improve gas exchange. However, most studies did not compare PCIRV and VC while keeping both the level of ventilation and end-expiratory alveolar pressure (total-PEEP) constant. METHODS: Nine patients with moderate to severe ARDS (lung injury score 2.83 +/- 0.18) had their lungs ventilated with VC, PCV with a conventional ratio (I:E 1:2; PC 1/2), and PCIRV (I:E 2:1 and 3:1; PC 2/1 and PC 3/1, respectively). Ventilator settings were adjusted to keep tidal volume, respiratory rate, FIo2, and total-PEEP constant in every mode. With each mode, a complete set of ventilatory, hemodynamic, and gas exchange parameters was obtained after 30 min. RESULTS: In PC 3/1, the data obtained could not be strictly compared to the other modes because total-PEEP was higher despite external-PEEP being set at zero. For the other modes (VC, PC 1/2, and PC 2/1), despite differences in peak airway pressures, no difference was noted for end-inspiratory and end-expiratory static airway pressures (which better reflect alveolar pressures) nor for lung and respiratory system compliance. Arterial oxygenation deteriorated slightly with PC 2/1 despite a higher mean airway pressure, whereas alveolar ventilation tended to be slightly, but not significantly, improved (lower PaCo2). A decrease in systolic and mean arterial pressure also was observed with PC 2/1 without other significant hemodynamic change. CONCLUSIONS: In this prospective controlled study, no short-term beneficial effect of PCV or PCIRV could be demonstrated over conventional VC with PEEP in patients with ARDS.

Adult↗
PubMed1994

Inspiratory pressure support.

Inspiratory pressure support is a mode of partial ventilatory support which can be defined as patient-initiated, pressure-targeted and patient-interrupted. Addition of pressure support to a spontaneously breathing patient results in a reduction of respiratory rate and an increase in tidal volume. It corrects arterial blood gas abnormalities resulting from rapid shallow breathing and reduces the work of breathing. The synchrony between the patient's demand and ventilator assistance is optimized and allows an improvement in the efficiency of the spontaneous effort of the patient. Since it is not volume-targeted, variation in delivered ventilation may occur in unstable patients or in patients with fluctuations in respiratory drive. Clinical advantages have been found using pressure support during the process of weaning from mechanical ventilation in patients with prolonged difficulty in tolerating discontinuation from mechanical ventilation. Lastly, it can be delivered via a face-mask to avoid the need for endotracheal intubation in patients with hypercapnic respiratory failure.

Humans↗
PubMed1994

Clinically relevant diaphragmatic dysfunction after cardiac operations.

Phrenic nerve injury and diaphragmatic dysfunction can be induced by cardiac operation. The clinical consequences are not well-established. We evaluated 13 consecutive patients over a 2-year period with unexplained and prolonged difficulties in weaning from mechanical ventilation. The mean time of measurement from the operation day was 31 +/- 19 days (range 8 to 78). With the same technique we also evaluated 12 control patients: four patients at day 1 after cardiac operation while they were still intubated; four normally convalescing patients at day 7 or 8 after cardiac operation; and four patients who required prolonged mechanical ventilation because of another identified cause after cardiac operation. Diaphragmatic function was evaluated at the bedside from esophageal and gastric pressure measurements. A low or negative ratio of gastric pressure swing to transdiaphragmatic pressure swing, indicative of diaphragm dysfunction, was found in all 13 patients (mean -0.39 +/- 0.64). The difference between the 13 patients and all control groups was found to be highly significant. Transdiaphragmatic pressure measured during a maximal voluntary inspiratory effort and transdiaphragmatic pressure measured during a short, sharp sniff were markedly diminished (28 +/- 18 cm H2O and 13 +/- 15 cm H2O, respectively) in the 13 patients, significantly different from values in the four control patients studied at day 7 or 8. Transdiaphragmatic pressure measured after magnetic stimulation in four patients was also markedly reduced (7 +/- 5 cm H2O) as compared with normal theoretic values. Aminophylline infusion had no effect on any of these parameters. In one of two patients evaluated a second time, about 5 weeks later, a marked improvement was observed. Estimating the prevalence of clinically relevant diaphragmatic dysfunction, we found it to be 0.5% when no topical cooling was used and 2.1% when iced slush with no insulation pad was added for myocardial protection (p < 0.005). The most striking finding was that the clinical course of the 13 patients was marked by severe intercurrent events, including cardiorespiratory arrest after early tracheal extubation in 5 patients, nosocomial pneumonia in 11, prolonged mechanical ventilation in all (58 +/- 41 days), and a fatal outcome in 3. We conclude that prolonged postoperative diaphragmatic dysfunction may cause severe life-threatening complications after cardiac operation and can be limited to some extent by avoiding the use of iced slush topical cooling of the heart.

Adult↗
PubMed1992

A knowledge-based system for assisted ventilation of patients in intensive care units.

The procedure for weaning a patient with respiratory insufficiency from mechanical ventilation may be complex and requires expertise obtained by long clinical practice. We designed a knowledge-based system for the management of patients receiving respiratory support and implemented a weaning procedure. The system is intended for patients whose spontaneous respiratory activity is assisted by a Hamilton Veolar ventilator delivering a positive pressure plateau during inspiration (Pressure Support Ventilation mode). Our closed-loop real-time system running on a Personal Computer continuously adapts the assistance provided by the ventilator to the patient's evolution, and indicates when the patient can be withdrawn from the ventilator. Three parameters are used to appreciate the 'respiratory comfort' of the patient: breathing frequency, which we consider the most informative index, tidal volume and end-tidal CO2 pressure. A preliminary study of 19 patients was performed to evaluate the ability of our system to adapt the assistance to the patient's needs, with the main objective of facilitating weaning by gradually lowering the level of assistance. In 10 of these patients, considered as good candidates for weaning on the strength of objective criteria, the system maintained the breathing pattern in a zone of comfort for 95% of the period of assisted ventilation and stated that they were 'weanable'. This was consistent with the clinical evolution of all 10 patients. These results show that such a system can provide effective management for mechanically ventilated patients.

Adult↗
PubMed1992

Use of the Blasius resistance formula to estimate the effective diameter of endotracheal tubes.

To early detect mucus deposition in endotracheal tubes (ETT), we propose using a geometric, flow-independent parameter, i.e., diameter of the ETT, based on a precise knowledge of ETT flow regime, instead of using the classic flow-dependent ETT resistance based on the empirical, nonlinear Rohrer equation. From the estimated slope of -0.24 derived from Moody diagrams characterizing the pressure-flow relationship in ETT of various inner diameters (D), we first assessed that the Blasius resistance formula slope of -0.25 could be applied to adult-size ETT, meaning that flow remains fully developed, turbulent, and hydraulically smooth (0.5 L/s less than or equal to V less than or equal to 1.4 L/s). Insertion into the ETT of a pressure catheter (external diameter: d) to stimulate in vivo measurements did not modify these results, provided the hydraulic diameter, D* = D - d, was substituted for D in the Blasius formula. The Blasius formula was then used to determine, from in vitro pressure and flow measurements in ETT before intubation and in ETT lined with dry mucus secretions, the effective diameter, shown here to be highly correlated to the actual diameter measured by volumetric water displacement. The effective ETT diameter was measured in eight patients at different stages after oral or nasal intubation. Compared with the actual ETT diameter measured before insertion, the effective diameter was slightly reduced (2.6 +/- 2.5%) during the first week of intubation and was strongly reduced (12.2 +/- 2.8%) during the second week.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1992

Bronchoalveolar lavage in immunocompromised patients. Clinical and functional consequences.

Fiberoptic bronchoscopy and bronchoalveolar lavage are major tools in the diagnosis of acute pneumonia in immunocompromised patients. We conducted a prospective study to assess the morbidity associated with this procedure in 14 patients with AIDS and 16 patients with drug-induced immunosuppression. No patient had a PaO2 lower than 70 mm Hg with additional oxygen. Clinical data, chest roentgenogram, pulmonary function test, forced vital capacity, forced expiratory volume in one second, and arterial blood gases were recorded before and after bronchoscopy. Arterial oxygen saturation was monitored during the procedure, and initial, lowest, and final saturation values were noted. The patients were separated into three groups on the basis of chest roentgenographic findings. No procedure-induced pneumonia or need for tracheal intubation occurred. Minor clinical symptoms induced by the lavage in seven patients resolved spontaneously. By contrast, mean SaO2 decreased markedly during the procedure from 94 +/- 3 to 87 +/- 5 percent (p less than 0.0001) and returned to only 89 +/- 5 percent at the end of the procedure. Lowest SaO2 during the procedure and final SaO2 correlated poorly with initial SaO2 but correlated well with initial FVC and FEV1 (p less than 0.01). The PFT values were lower following bronchoscopy. O2 desaturation was more pronounced in patients with severe roentgenographic abnormalities. No significant differences were found between the three groups of patients, or between the AIDS and DII patients in terms of changes in PFT values. We conclude that in immunocompromised patients, bronchoscopy with BAL induces severe arterial oxygen desaturation which is correlated with initial PFT and chest roentgenographic findings, and most of these abnormalities are transient and do not lead to major complications.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Intraoperative transesophageal echocardiography for pulmonary embolectomy without cardiopulmonary bypass.

This case report describes a patient with massive pulmonary embolism and acute circulatory failure in whom transesophageal echocardiography permitted the diagnosis of thrombi in the main pulmonary truncus and in the right branch and guided intraoperatively the surgical embolectomy performed under simple venous inflow occlusion because of a contraindication to heparin administration. Transesophageal echocardiography seems to be a very helpful technique to diagnose promptly massive pulmonary embolism and a very useful tool at the time of operation to guide the embolectomy.

Cardiopulmonary Bypass↗
PubMed1991

Inspiratory pressure support compensates for the additional work of breathing caused by the endotracheal tube.

Breathing through an endotracheal tube and a demand valve may increase the work performed by the respiratory muscles. Inspiratory pressure support (PS) is known to reduce this work and might therefore compensate for this increased requirement. To test this hypothesis, we measured the work of breathing (WOB) in 11 patients whose tracheas were intubated. Five had no intrinsic lung disease, but six had chronic obstructive lung disease. We compared WOB measurements taken under several sets of conditions: during assisted breathing at four levels of PS, during unassisted breathing and connection to a T-piece, and after extubation of the trachea. During unassisted breathing via the ventilator circuit (PS set at 0 cmH20), the WOB per minute was greater than that after extubation, with a mean increase (+/- standard deviation) of 68 +/- 38% (10.3 +/- 5.1 vs. 6.5 +/- 3.7 J.min-1, P less than 0.01). While breathing through the T-piece, the WOB was 27 +/- 18% greater than after tracheal extubation (8.2 +/- 5.1 vs. 6.5 +/- 3.7 J.min-1, P less than 0.05). The principal reason why inspiratory work decreased after extubation was that the ventilatory requirement decreased. For each patient, we determined retrospectively, after extubation, the level of PS that had reduced WOB to its postextubation value and obtained levels ranging from 3.4 to 14.4 cmH2O. The PS level at which additional WOB was compensated for, was greater in patients with chronic lung disease than in those free of lung disease (12.0 +/- 1.9 vs. 5.7 +/- 1.5 cm H2O, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Diagnosis of nosocomial pneumonia in mechanically ventilated patients. Comparison of a plugged telescoping catheter with the protected specimen brush.

Protected samples of lower respiratory tract secretions processed by quantitative culture techniques are recommended to diagnose nosocomial bacterial pneumonia in intubated, mechanically ventilated patients. To evaluate the accuracy of a simple and inexpensive sampling device in this setting, we compared quantitative cultures of paired single-sheathed plugged telescoping catheter (PTC) and protected specimen brush (PSB) samples in 55 patients during 78 suspected episodes of nosocomial pneumonia. PTC and PSB samples were taken in randomized order, and patients were also randomized to have PTC samples taken "blindly" or via a fiberoptic bronchoscope. Fifteen PSB and 27 PTC samples were culture positive (greater than or equal to 10(3) cfu/ml). The two sampling procedures gave similar results in 58 (74%) episodes. A major discrepancy occurred in 20 episodes, including six false negatives of PSB in episodes of proved pneumonia, four possible false positives of PSB, and 10 possible false positives of PTC (three of which rapidly evolved towards overt pneumonia). The sensitivity and specificity of PTC were 100 and 82.2%, and those of PSB were 64.7 and 93.5%, respectively. Blinded or directed PTC samples had similar concordance with PSB samples taken via bronchoscopy. We conclude that PTC is at least as accurate as PSB in the bacteriologic diagnosis of nosocomial pneumonia in intubated patients, and that its use can result in substantial cost savings, especially when fiberoptic bronchoscopy is not otherwise indicated.

Bacterial Infections↗
PubMed1991

Effects of albuterol inhalation on the work of breathing during weaning from mechanical ventilation.

The work of breathing is a major determinant of the success of weaning from mechanical ventilation. The aim of this study was to assess whether an inhaled bronchodilator could reduce the mechanical load on the respiratory muscles and diminish the work. For this purpose, 15 intubated patients in the process of weaning from mechanical ventilation inhaled the beta 2-agonist bronchodilator albuterol via a spacer device filled with 1 mg of the drug and connected to the endotracheal tube. During spontaneous breathing, the mean work of breathing diminished significantly after albuterol, from 9.35 +/- 1.05 to 8.33 +/- 1.13 J/min (p less than 0.01), and seven patients exhibited a decrease superior or equal to 15%. This decrease resulted from a marked reduction in lung and airway resistance, from 12.0 +/- 1.7 to 9.8 +/- 1.4 cm H2O.L-1.s (p less than 0.05). No significant changes were observed in the breathing pattern, intrinsic PEEP or arterial blood gas measurements after albuterol, and peripheral cardiovascular effects were not significant. In seven patients, we were able to compare the changes that occurred after albuterol in the work of breathing during weaning from mechanical ventilation with the changes in pulmonary function induced by albuterol after extubation, as assessed by the forced oscillation method. A close correlation was found between the two types of change, further indicating that the reduction in the work of breathing was more likely to occur in patients with the largest bronchodilating effect of albuterol at baseline.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗
PubMed1991

Constant-flow insufflation prevents arterial oxygen desaturation during endotracheal suctioning.

In mechanically ventilated patients, disconnection from the ventilator and endotracheal suctioning can induce major arterial oxygen desaturation resulting from apnea, changes in inspired oxygen fraction, and decrease in lung volume. The aim of this study was to test the efficacy of a simple method of delivering oxygen and maintaining lung volume during this process. Our study was conducted in two parts. In the first part, constant-flow insufflation of oxygen (CFI) was used in seven patients ventilated for acute respiratory failure (PaO2/FlO2 = 347 +/- 33 mm Hg) as a means of maintaining arterial oxygenation during apnea and disconnection from the ventilator. CFI was administered via a modified endotracheal tube in which small capillaries allowed delivery of a high-velocity jet flow near the tracheal end of the tube during disconnection from the ventilator. In comparison to apnea alone, CFI prevented a fall in arterial oxygen tension (16 +/- 7 mm Hg during CFI versus 117 +/- 27 during apnea, after 90 s of disconnection in the two situations, p less than 0.001), whereas it did not reduce the development of hypercapnia. The efficacy of CFI resulted both from the injection of oxygen into the trachea and from the maintenance of positive alveolar pressure induced by air entrainment (mean 10.4 +/- 1.1 cm H2O), preventing a fall in lung volume usually occurring after disconnection (+338 +/- 88 ml during CFI versus -344 +/- 64 ml during apnea, p less than 0.01). In the second part of the study CFI was used to prevent arterial oxygen desaturation induced by endotracheal suctioning.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗