Biomedical subjects

Didier Tassaux

Publications and source records attributed to Didier Tassaux.

7 recordsLinked to original sources

PubMed2003

Comparative effects of helium-oxygen and external positive end-expiratory pressure on respiratory mechanics, gas exchange, and ventilation-perfusion relationships in mechanically ventilated patients with chronic obstructive pulmonary disease.

OBJECTIVE: To compare the effects of He/O(2) and external PEEP (PEEPe) on intrinsic PEEP (PEEPi), respiratory mechanics, gas exchange, and ventilation/perfusion (V(A)/Q) in mechanically ventilated COPD patients. DESIGN AND SETTING: Prospective, interventional study in the intensive care unit of a university hospital. INTERVENTIONS: Ten intubated, sedated, paralyzed, mechanically ventilated COPD patients studied in the following conditions: (a) baseline settings made by clinician in charge, air/O(2), ZEEP; (b) He/O(2), ZEEP; (c) air/O(2), ZEEP; (d) air/O(2), PEEPe 80% of PEEPi. Measurements at each condition included V(A)/Q by the multiple inert gas elimination technique (MIGET). RESULTS: PEEPi and trapped gas volume were comparably reduced by He/O(2) (4.2+/-4 vs. 7.7+/-4 cmH(2)O and 98+/-82 vs. 217+/-124 ml, respectively) and PEEPe (4.4+/-1.3 vs. 7.8+/-3.6 cmH(2)O and 120+/-107 vs. 216+/-115 ml, respectively). He/O(2) reduced inspiratory and expiratory respiratory system resistance (15.5+/-4.4 vs. 20.7+/-6.9 and 19+/-9 vs. 28.8+/-15 cmH(2)O l(-1)s(-1), respectively) and plateau pressure (13+/-4 vs. 17+/-6 cmH(2)O). PEEPe increased airway pressures, including total PEEP, and elastance. PaO(2)/FIO(2) was slightly reduced by He/O(2) (225+/-83 vs. 245+/-82) without significant V(A)/Q change. CONCLUSIONS: He/O(2) and PEEPe comparably reduced PEEPi and trapped gas volume. However, He/O(2) decreased airway resistance and intrathoracic pressures, at a small cost in arterial oxygenation. He/O(2) could offer an attractive option in COPD patients with PEEPi/dynamic hyperinflation.

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PubMed2003

Usefulness of helium-oxygen mixtures in the treatment of mechanically ventilated patients.

The density of helium is markedly lower than that of air or any of its components, leading to a substantial decrease in airway resistance to flow when it is inhaled. In mechanically ventilated patients with obstructive airway disease, replacing the usual air-oxygen mixture with helium-oxygen has been shown to reduce dynamic hyperinflation and intrinsic positive end-expiratory pressure; to decrease lung inflation pressures, respiratory acidosis, and work of breathing; and to improve arterial blood gases. Aerosol delivery to distal airways is enhanced with helium-oxygen. Preliminary data also suggest that the use of helium-oxygen could be a valuable approach to decrease postextubation respiratory distress. However, interference with ventilator function and added costs are two major disadvantages of helium-oxygen. Hence, before its widespread use in mechanically ventilated patients can be recommended, studies are needed to determine whether these favorable short-term effects can influence patient outcome.

Helium↗

PubMed2003

Helium-oxygen versus air-oxygen noninvasive pressure support in decompensated chronic obstructive disease: A prospective, multicenter study.

OBJECTIVE: To study whether noninvasive pressure support ventilation (NIPSV) with helium/oxygen (He/oxygen), which can reduce dyspnea, PaCO2, and work of breathing more than NIPSV with air/oxygen in decompensated chronic obstructive pulmonary disease, could have beneficial consequences on outcome and hospitalization costs. DESIGN: Prospective, randomized, multicenter study. SETTING: Intensive care units of three tertiary care university hospitals. PATIENTS: All patients with chronic obstructive pulmonary disease admitted to the intensive care units for NIPSV during a 24-month period. INTERVENTIONS: Patients were randomized to NIPSV with air/oxygen or He/oxygen. NIPSV settings, number of daily trials, decision to intubate, and intensive care unit and hospital discharge criteria followed standard practice guidelines. RESULTS: A total of 123 patients (male/female ratio, 71:52; age, 71 +/- 10 yrs, Acute Physiology and Chronic Health Evaluation II, 17 +/- 4) were included. Intubation rate (air/oxygen 20% vs. He/oxygen 13%) and length of stay in the intensive care unit (air/oxygen 6.2 +/- 5.6 vs. He/oxygen 5.1 +/- 4 days) were comparable. The post-intensive care unit hospital stay was lower with He/oxygen (air/oxygen 19 +/- 12 vs. He/oxygen 13 +/- 6 days, p < .002). Cost of NIPSV gases was higher with He/oxygen, but total hospitalization costs were lower by $3,348 per patient with He/oxygen. No complications were associated with the use of He/oxygen. CONCLUSION: He/oxygen did not significantly reduce intubation rate or intensive care unit stay, but hospital stay was shorter and total costs were lower. He/oxygen NIPSV can be safely administered and could prove to be a cost-effective strategy.

APACHE↗

PubMed2002

Comparative bench study of triggering, pressurization, and cycling between the home ventilator VPAP II and three ICU ventilators.

OBJECTIVE: To compare triggering, pressurization, and cycling of the home ventilator VPAP II with those of three ICU ventilators (Evita 4, Galileo, and Servo 300). DESIGN AND SETTING: Two-compartment lung model study in a research laboratory, university hospital. METHODS: One compartment was driven by an ICU ventilator to mimic "patient" inspiratory effort, while the other was connected to the tested ventilator. Pressure support of 10, 15, 20, and 25 cmH2O, and inspiratory efforts of 5, 10, 15, 20, and 25 cmH2O (inspiratory time 1 s) were used in normal, obstructive, and restrictive conditions. Triggering delay (Td), triggering workload, pressurization at 300 and 500 ms, and difference between the "patient's" inspiratory time and that of the ventilator were analyzed. RESULTS: No difference was noted in triggering workload between VPAP II, Evita 4, and Galileo while Servo 300 had a lower value. Pressurization at 300 ms on Evita 4 and Servo 300 reached 75% of the ideal value, on Galileo 35%, and on VPAP II 45%. Pressurization at 500 ms on Evita 4 and Servo 300 reached 85% of the ideal value, on Galileo 50%, and on VPAP II 55%. Cycling was delayed in obstructive conditions and premature in restrictive conditions with each of the devices. CONCLUSIONS: The VPAP II performed as well as one ICU ventilator and less well than two. Home devices for noninvasive ventilation in acute respiratory failure outside the ICU could prove attractive as they are smaller, less costly, and easier to use than ICU machines.

Equipment Design↗

PubMed2002

Helium-oxygen ventilation.

Because of its low density, the He/O2 mixture markedly affects the dynamics of gas-flow, increasing inspiratory and expiratory flows, reducing WOB and respiratory acidosis, and relieving dyspnea in various clinical situations associated with obstructive airway disease. The magnitude of these changes varies according to the proportion of turbulent, transitional, and laminar flow conditions. These effects, however, last only as long as the patient breathes the He/O2 mixture, because it has no curative effect on the cause of airway obstruction. Thus, He/O2 ventilation is mostly useful while awaiting the effects of more definitive treatment. Evidence shows that He/O2 ventilation can improve pathophysiologic and clinical parameters in spontaneously breathing patients with upper airway obstruction, asthma. COPD, bronchopulmonary dysplasia. and bronchiolitis. Furthermore. He/O2 ventilation may prove to be a valuable adjunct in decompensated COPD patients, during both NIV and conventional mechanical ventilation. Despite promising results, however, there are two primary pitfalls to He/O2 ventilation. First, the consequences of the physical properties of the He/O2 mixture on various ventilator functions, the major differences between machines, and the correction factors to apply (if necessary) should be known. Second, in this age of cost control, particular attention should be paid to the cost-benefit ratio of He/O2 ventilation. Indeed, despite clinical evidence that the pathophysiologic principles on which He/O2 ventilation rests can be translated into favorable short-term physiologic and subjective effects, there is presently no evidence of a significant effect on patient outcome. Hence, before He/O2 ventilation can be recommended for widespread use, prospective outcome studies should be conducted in patients who suffer from the conditions discussed in this article to identify which, if any, are most likely to receive a benefit. Meanwhile, the authors recommend that He/O2 ventilation be reserved for patients who have a severe condition and who do not respond to the classic validated treatment modalities.

Clinical Trials as Topic↗

PubMed2002

The impact of a cardioprotective protocol on the incidence of cardiac complications after aortic abdominal surgery.

UNLABELLED: We analyzed a local database including 468 consecutive patients who underwent elective aortic abdominal surgery over an 8-yr period in a single institution. A new cardioprotective perioperative protocol was introduced in January 1997, and we questioned whether perioperative cardiac outcome could be favorably influenced by the application of a stepwise cardiovascular evaluation based on the American College of Cardiology/American Heart Association guidelines and by the use of antiadrenergic drugs. Clonidine was administered during surgery, and beta-blockers were titrated after surgery to achieve heart rates less than 80 bpm. We compared data of two consecutive 4-yr periods (1993-1996 [control period] versus 1997-2000 [intervention period]). Implementation of American College of Cardiology/American Heart Association guidelines was associated with increased preoperative myocardial scanning (44.3% vs 20.6%; P < 0.05) and coronary revascularization (7.7% vs 0.8%; P < 0.05). During the intervention period, there was a significant decrease in the incidence of cardiac complications (from 11.3% to 4.5%) and an increase in event-free survival at 1 yr after surgery (from 91.3% to 98.2%). Multivariate regression analysis showed that the combined administration of clonidine and beta-blockers was associated with a decreased risk of cardiovascular events (odds ratio, 0.3; 95% confidence interval, 0.1-0.8), whereas major bleeding, renal insufficiency, and chronic obstructive pulmonary disease were predictive of cardiac complications. In conclusion, cardiac testing was helpful to identify a small subset of high-risk patients who might benefit from coronary revascularization. Sequential and selective antiadrenergic treatments were associated with improved postoperative cardiac outcome. IMPLICATIONS: Implementation of American College of Cardiology/American Heart Association guidelines and use of antiadrenergic drugs were associated with better cardiac outcomes after major vascular surgery.

Adrenergic beta-Antagonists↗

PubMed2002

Patient-ventilator interactions during partial ventilatory support: a preliminary study comparing the effects of adaptive support ventilation with synchronized intermittent mandatory ventilation plus inspiratory pressure support.

OBJECTIVE: To compare the effects of adaptive support ventilation (ASV) and synchronized intermittent mandatory ventilation plus pressure support (SIMV-PS) on patient-ventilator interactions in patients undergoing partial ventilatory support. DESIGN: Prospective, crossover interventional study. SETTING: Medical intensive care unit, university tertiary care center. PATIENTS: Ten patients, intubated and mechanically ventilated for acute respiratory failure of diverse causes, in the early weaning period, ventilated with SIMV-PS and clinically detectable sternocleidomastoid activity suggesting increased inspiratory load and patient-ventilator dyssynchrony. INTERVENTIONS: Measurement of respiratory mechanics, P0.1, sternocleidomastoid electromyographic activity, arterial blood gases, and systemic hemodynamics in three conditions: 1) after 45 mins with SIMV-PS (SIMV-PS 1); 2) after 45 mins with ASV, set to deliver the same minute-ventilation as during SIMV-PS; 3) 45 mins after return to SIMV-PS (SIMV-PS 2), with settings identical to those of the first SIMV-PS period. MAIN RESULTS: The same minute ventilation was observed during ASV (11.4 +/- 3.1 l/min [mean +/- sd]) as during SIMV-PS 1 (11.6 +/- 3.5 L/min) and SIMV-PS 2 (10.8 +/- 3.4 L/min). No parameter was significantly different between SIMV-PS 1 and 2, hence subsequent results refer to ASV vs. SIMV-PS 1. During ASV, tidal volume increased (538 +/- 91 vs. 671 +/- 100 mL, p <.05) and total respiratory rate decreased (22 +/- 7 vs. 17 +/- 3 breaths/min, p <.05) vs. SIMV-PS. However, spontaneous respiratory rate increased in six patients, decreased in four, and remained unchanged in one. P0.1 decreased during ASV in all patients except three in whom no change was noted (1.8 +/- 0.9 vs. 1.1 +/- 1 cm H2O, p <.05). During ASV, sternocleidomastoid electromyogram activity was markedly reduced (electromyogram index, where SIMV-PS 1 = 100, ASV 34 +/- 41, SIMV-PS 2 89 +/- 36, p <.02) as was palpable muscle activity. No changes were noted in arterial blood gases, pH, or mean systemic pressure during the trial. CONCLUSION: In patients undergoing partial ventilatory support, with clinical and electromyographic signs of increased respiratory muscle loading, ASV provided levels of minute ventilation comparable to those of SIMV-PS. However, with ASV, central respiratory drive and sternocleidomastoid activity were markedly reduced, suggesting decreased inspiratory load and improved patient-ventilator interactions. These preliminary results warrant further testing of ASV for partial ventilatory support.

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