Resp Care
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The largest change in spirometric pulmonary function testing in the last 10 years has been the introduction of the digital computer for data acquisition and reduction. Computer-assisted spirometry can enhance the effectiveness of spirometric testing by increasing test accuracy, increasing patient acceptance, and decreasing the time necessary to complete the test and its interpretation. Any computer-assisted spirometer should be easy to use and should clearly display and properly report test results. I recommend that the American Thoracic Society Standards for spirometric testing be used by pulmonary function laboratories and that test interpretation made by a computer be verified.
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We determined the minimum systolic pressures required for blood to enter and begin to displace the plungers of four brands of 3-ml and 5-ml plastic and glass arterial blood gas syringes by combining samples of each syringe size with three sizes of short-beveled needles--25 gauge, 5/8"; 22-gauge, 1"; and 20-gauge, 1 1/2". We measured pressures by use of an arterial-vessel model that incorporated whole human blood and simulated the conditions of a percutaneous arterial puncture. ⋯ Because we found no clinical or statistical differences between 20- and 22-gauge needles, we do not recommend use of the larger 20-gauge needle. The syringe-needle combinations that we do recommend should negate the need for, and the potential trauma of, manual aspiration of the syringe plunger.
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To determine the fractional delivered oxygen concentrations (FDO2) and the proper functioning of patient valves in adult resuscitation bags, we studied the Laerdal, the PMR 1, the PMR 2, and the Vitalograph resuscitators at various oxygen flowrates and ventilation patterns, with and without reservoirs. The Vitalograph, with new or old reservoir, and the PMR 1 cannot deliver high oxygen concentrations (FDO2 greater than 0.90) and should not be used when high FDO2 is important. The PMR 2 and the Laerdal cannot deliver high oxygen concentrations without reservoirs attached; with reservoirs attached the Laerdal achieves FDO2 greater than 0.98 at a flowrate of 10 l/min, and the PMR 2 achieves FDO2 greater than 0.90 at a flowrate of 15 l/min.
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We evaluated the water-vapor output from four brands of unheated, prefilled bubble humidifiers-the Aerwey 300, the Aquapak 301, the McGaw 250, and the Travenol 500-at oxygen flowrates of 2, 4, 6, and 81/min. We recorded relative humidity (RH) and temperature in a test chamber at intervals over a minimum period of 24 h, and we calculated water-vapor content (WVC) and corresponding RH at 37 degrees C. Ambient RH was 53.4% +/- 5.25% (mean +/- 1 SD) at a test-chamber temperature of 26.2 degrees C +/- 0.79 degrees C. ⋯ A statistically significant decrease in mean WVC and RH at 37 degrees C occurred as the oxygen flowrate increased (P less than 0.001). None of the humidifiers was able to hydrate the source gas to a mean equivalent of 50% RH at 37 degrees C, at any flowrate. The design of the humidifier bubble diffuser and the source-gas flowrate appear to be the prime determinants of the humidification efficiency of unheated, prefilled bubble humidifiers.
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Degree of hearing loss in the infant is related to high-intensity or high-frequency sound (noise). We measured sound levels of 6 models of pneumatic nebulizers and 8 models of humidifiers at various flowrates, FIO2 settings, and water levels, when they were attached to incubators and oxygen hoods; we also evaluated sound levels from 2 models of ultrasonic nebulizers at various output settings. Among the pneumatic nebulizers, the recommended 58-dbA maximum sound level was exceeded by the Aquapak 621, Ohio Deluxe, and Puritan All-Purpose devices. ⋯ Among the humidifiers, all produced sound levels below the recommended 58-dbA maximum except the Travenol humidifier; the Bennett Cascade, Conchapak, Foregger, and Hudson humidifiers produced mean sound levels in the 43.0- to 43.5-dbA range. Sound levels increased under all conditions when the devices were used with oxygen hoods. The ultrasonic nebulizers produced low sound levels, but the high-frequency ultrasound they also produce may be undesirable for infants; this question requires further investigation.