Ghassan Jamaleddine

Changes in resistances of endotracheal tubes with reductions in the cross-sectional area.

Background and objectives: Partial obstruction of endotracheal tubes due to accumulation of secretions and mucus plugs can increase the tube resistance and subsequently impose increased resistive load on the patient. This study was performed to determine the changes in the resistance of endotracheal tubes of sizes 7.5, 8.0 and 8.5 mm with different degrees and locations of endotracheal tube narrowing. Methods: Reductions of 10%, 25%, 50% and 75% in the endotracheal tubes cross‐sectional areas were created at different sites along the axes of the tube connected to an artificial lung. While ventilating with a constant inspiratory flow, a 1 s end‐inspiratory occlusion manoeuvre was applied and the resulting plateau pressure was determined. The resistance was calculated as (peak airway pressure ‐ plateau pressure)/peak inspiratory flow. Results: Significant increases in the endotracheal tubes resistances were observed as the tubes cross‐sectional area reduction was increased from 25% to 50% and from 50% to 75% for the 7.5 mm endotracheal tube, from 25% to 50% for the 8.0 mm endotracheal tube, and from 50% to 75% for the 8.5 mm endotracheal tube. Changes of the endotracheal tube resistances were not affected by the site of cross‐sectional area reductions along the axes of the tubes. Conclusions: For endotracheal tubes of sizes 7.5, 8.0 and 8.5 mm, significant changes in the tubes resistances are observed when the partial obstructions of the tubes exceed certain critical values. The location of the partial obstruction did not affect the changes in the endotracheal tube resistances.

Detection of a highly prevalent and potentially virulent strain of Pseudomonas aeruginosa from nosocomial infections in a medical center

BackgroundWe correlated genotypes, virulence factors and antimicrobial susceptibility patterns of nosocomially identified Pseudomonas aeruginosa isolates from clinical specimens to those of environmental isolates encountered in the same units of a medical center. Antibiotic susceptibility testing, RAPD analysis and detection of enzymatic activities of extracellular virulence factors, were done on these isolates.ResultsData showed that most of the clinical and environmental isolates were susceptible to tested antimicrobial agents. RAPD analysis determined the presence of 31 genotypes, with genotype 1 detected in 42% of the clinical isolates and 43% of the environmental isolates. Enzymatic activity testing showed that genotype 1 produced all virulence factors tested for.ConclusionIn conclusion, our data demonstrated the predominant prevalence of a potentially virulent P. aeruginosa genotype, circulating in a number of units of the medical center and emphasize the need to reinforce infection control measures.

THROMBOTIC THROMBOCYTOPENIC PURPURA IN A CASE OF SCLERODERMA RENAL CRISIS TREATED WITH TWICE-DAILY THERAPEUTIC PLASMA EXCHANGE

We report the rare complication of thrombotic thrombocytopenic purpura (TTP) in an elderly patient with the uncommon scleroderma renal crisis (SRC) at the advanced age of 85 years. Initially, she was treated by standard daily one and a half plasma volume therapeutic plasma exchange (TPE), in combination with steroid therapy. Due to an unsatisfactory clinical response, she was consequently, treated by an intensive twice-daily one and a half plasma volume TPE regimen. Although there was an increase in the platelet count, a 7-day course of the intensive regimen did not elicit further propitious laboratory test results or a clinical improvement and the patient expired secondary to the pulmonary and cardiac conditions related to SRC. Intensive TPE administration has been advocated in few specific patients who are refractory to standard daily treatment. The unfavorable outcome in this case may be attributed to the multiple complications associated with her primary disorder. In conclusion, we observed intensive twice-daily TPE to increase temporarily the platelet count, but not to be of benefit in a patient with SRC and multiple organ failure. The two TPE regimens and outcomes are compared and the pathogenesis of TTP and scleroderma are discussed.

Coronary artery bypass grafting after pneumonectomy

The need to perform coronary artery bypass grafting in patients who have a single lung is not uncommon. To date, the safety of such procedures has not been well documented. In this article, we review the literature using the Medline 1966 to September 2000 database to identify patients with pneumonectomy who underwent coronary artery grafting and we provide a compilation of all reported cases. We also present an additional case in whom the use of nasal bilevel positive airway pressure was beneficial in preventing postoperative pulmonary complications.

Metabolic and Respiratory Variables during Pressure Support versus Synchronized Intermittent Mandatory Ventilation

Background: Mechanically ventilated patients interact and respond differently to different modes of ventilatory support. Objectives: To assess changes in metabolic and respiratory variables during equivalent changes with either pressure support ventilation (PSV) or volume-cycled synchronized intermittent mandatory ventilation (SIMV) in non-tracheostomized patients without known obstructive pulmonary disease receiving short-term mechanical ventilation in the intensive care unit. Methods: Fourteen patients receiving volume-cycled SIMV at 12 breaths/min (SIMV100%) were included in the study. The PSV level (PSV100%) resulting in a minute volume and respiratory rate equivalent to that during SIMV100% was determined for each patient. Then each patient underwent trials at 66% and 33% of initial ventilator support with volume-cycled SIMV (SIMV66% and SIMV33%) and PSV (PSV66% and PSV33%) in random order. At the end of each trial, oxygen consumption (v̇O2), carbon dioxide production (v̇CO2), measured energy expenditures (MEE), peak inspiratory flow, total respiratory frequency, tidal volume, minute ventilation, occlusion pressure (P0.1) and inspiratory duty cycle (Ti/Ttot) were measured. Results: There were smaller changes in v̇O2, v̇CO2 and MEE when equivalent changes were applied with PSV (15.7 ± 4.4; 12.5 ± 2.2 and 15 ± 3.5%) compared with volume-cycled SIMV (32.7 ± 7.7; 23 ± 5.2 and 30.7 ± 6.8%; p < 0.05). P0.1 and Ti/Ttot were significantly smaller during PSV (2.64 ± 0.28 and 0.38 ± 0.03 cm H2O) than volume-cycled SIMV (4.01 ± 0.21 and 0.43 ± 0.02 cm H2O; p < 0.05). Conclusions: Changes in the level of PSV resulted in smaller changes in metabolic and respiratory variables compared with equivalent changes in the level of volume-cycled SIMV support. PSV may be more suitable for progressive respiratory muscle reloading.

Use of Heparinized versus Non-Heparinized Syringes for Measurements of the Pleural Fluid pH

Background: Pleural fluid (PF) pH measurement is important for establishing a diagnosis and for guiding clinical management. The current standard practice is to collect PF samples for pH measurement in heparinized syringes at room temperature and to instantaneously process these samples. Objective: The purpose of this study is to investigate the effect of collecting PF in heparinized versus non-heparinized syringes at room temperature on PF pH measurements when processed at various time intervals. Methods: From 50 consecutive thoracenteses, 1 ml of PF was collected anaerobically in each of six 3-ml syringes. Only three syringes were coated with heparin. The samples were processed for PF pH measurements at time 0 (T₀) and 1 h (T1) and 2 h (T2) after collection. All specimens were preserved at room temperature, until the measurements were carried out in duplicates by a calibrated blood gas analyzer. Results: PF pH values were significantly lower with heparinized versus non-heparinized syringes at all time intervals (T₀: pH heparinized = 7.378 ± 0.107 vs. pH non-heparinized = 7.390 ± 0.108; T1: pH heparinized = 7.378 ± 0.115 vs. pH non-heparinized = 7.389 ± 0.111; T2: pH heparinized = 7.367 ± 0.105 vs. pH non-heparinized = 7.389 ± 0.121). In the heparinized syringes, there was a significant decrease in PF pH values at T2 versus T₀ and T1. There were no significant changes in PF pH values over time in the non-heparinized syringes. Conclusions: For serial PF pH measurements, the same type of syringes (either heparinized or non-heparinized) should be consistently used. With heparinized syringes, processing of PF pH measurements should be performed within 1 h after collection.

Metastases in malignant pleural mesothelioma: A new radiological appearance

This report describes a patient with malignant pleural mesothelioma who presented with a right‐sided pleural effusion and contralateral parenchymal metastases manifesting as alveolar opacities with air bronchograms. This radiological pattern of metastases has never been described before. The patient died from respiratory failure related to extensive parenchymal metastases, an outcome seldom reported with malignant pleural mesothelioma.

Pressure support ventilation: a significant confounding factor in the determination of the rapid shallow breathing index.

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