Influence of jet nebulization and oxygen delivery on the fraction of inspired oxygen: an experimental model.

BACKGROUND: The fraction of inspired oxygen (FiO(2)) during oxygen-driven jet nebulization is unknown. In the case of air-driven jet nebulization, oxygen is often added through a nasal device, and again, the FiO(2) is unknown. The aim of this experimental study was to measure FiO(2) during oxygen- and air-driven jet nebulization, oxygen being added through a nasal device, and to compare the values observed with those measured during standard oxygen therapy. METHODS: An endotracheal tube was inserted into the distal tracheal extremity of a cadaveric head and neck specimen and connected to a pump, simulating different respiratory patterns. FiO(2) was measured using an electrochemical oxygen analyzer under different nebulization and oxygen delivery conditions. Variables were compared using canonical analysis and analysis of simple and multiple variance. RESULTS: FiO(2) was significantly influenced by the mode of oxygen delivery (p = 0.001). The highest FiO(2) was observed when oxygen was delivered via a nasopharyngeal catheter associated with air-driven jet nebulization. For oxygen flow rates of 12 and 15 L/min, a nasal cannula combined with air-driven jet nebulization resulted in a similar FiO(2). The FiO(2) was significantly lower in the case of oxygen-driven jet nebulization. The FiO(2) decreased with increasing respiratory rate (p < 0.001) and tidal volume (p < 0.001). CONCLUSIONS: Oxygen delivery through a nasal device during air-driven jet nebulization significantly increases the FiO(2), whereas oxygen-driven jet nebulization dramatically decreases FiO(2) compared with standard oxygen therapy.

Relationship between occupational risk factors and severity markers of systemic sclerosis.

OBJECTIVE: To investigate a potential association between occupational risk factors and severity markers of systemic sclerosis (SSc) defined by diffuse cutaneous extent, pulmonary involvement, and immunologic profile, i.e., presence of antitopoisomerase I antibody (anti-topo I). METHODS: Occupational exposures were assessed in 105 patients with SSc from 1998 to 2002. Exposures to silica dust, welding fumes, solvents, and epoxy resins were investigated. A group of 39 exposed SSc patients and a group of 66 unexposed ones were identified and compared according to severity markers of SSc. The stage of cutaneous extent was defined according to the classification of Leroy, as limited scleroderma (lSSc) or diffuse scleroderma (dSSc). Respiratory status was defined by pulmonary function tests and high resolution computed tomography. Immunological profile was determined by the presence of anti-topo I or anticentromere antibodies (ACA). Statistical relationships between occupational exposures and severity markers of SSc were evaluated using a multiple correspondence analysis and Fisher's exact test. RESULTS: Diffuse scleroderma affected mainly patients exposed during their occupational life to toxic agents. There were significant or close to significant associations between toxic exposure and dSSc (p = 0.06), pulmonary involvement (p = 0.10), and negative ACA (p = 0.03). The most incriminated products seemed to be epoxy resins (p = 0.06), white spirit (p = 0.07), aromatic solvents (p = 0.07), and silica coupled to welding fumes (p = 0.10). CONCLUSION: Our results indicate that occupational toxic factors have an influence on the severity of SSc.

Residual gravimetric method to measure nebulizer output.

The aim of this study was to assess a residual gravimetric method based on weighing dry filters to measure the aerosol output of nebulizers. This residual gravimetric method was compared to assay methods based on spectrophotometric measurement of terbutaline (Bricanyl, Astra Zeneca, France), high-performance liquid chromatography (HPLC) measurement of tobramycin (Tobi, Chiron, U.S.A.), and electrochemical measurements of NaF (as defined by the European standard). Two breath-enhanced jet nebulizers, one standard jet nebulizer, and one ultrasonic nebulizer were tested. Output produced by the residual gravimetric method was calculated by weighing the filters both before and after aerosol collection and by filter drying corrected by the proportion of drug contained in total solute mass. Output produced by the electrochemical, spectrophotometric, and HPLC methods was determined after assaying the drug extraction filter. The results demonstrated a strong correlation between the residual gravimetric method (x axis) and assay methods (y axis) in terms of drug mass output (y = 1.00 x -0.02, r(2) = 0.99, n = 27). We conclude that a residual gravimetric method based on dry filters, when validated for a particular agent, is an accurate way of measuring aerosol output.