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Biomedical subjects

M McPeck

Publications and source records attributed to M McPeck.

8 recordsLinked to original sources
PubMed1997

Aerosol delivery during continuous nebulization.

BACKGROUND AND OBJECTIVES: Continuous administration of aerosolized beta 2-agonists has been suggested as an effective treatment for severe reversible airways disease. To facilitate continuous therapy and avoid a feed system for small-volume nebulizers (SVNs), a large-volume medication nebulizer (Vortran HEART) was developed. The goal of this study was to determine actual drug delivery of the HEART and conventional SVNs for both adult and pediatric breathing patterns. DESIGN: Output studies were conducted on comparable samples of CIS-US AeroTech II and Hospitak PowerMist SVNs and Vortran HEART large-volume continuous nebulizers. To duplicate clinical aerosol delivery via an aerosol mask, drug particles were inhaled through the mouth of a model of a human face for two test breathing patterns (adult = tidal volume (Vt) of 500 mL, 20 breaths/min, duty cycle of 40%; pediatric = VT of 100 mL, 35 breaths/min, duty cycle of 40%), generated by a ventilator. Radiolabeled particles of saline solution, confirmed to behave identically to albuterol, were collected on absolute filters at the mouth of the face to measure the actual mass of albuterol particles delivered to the airway opening. RESULTS: The AeroTech II and PowerMist SVNs delivered 5.14 and 3.74 mg/h, respectively, for the adult breathing pattern and 2.97 and 2.48 mg/h, respectively, for the pediatric breathing pattern. Drug delivery rates of the HEART were a function of drug concentration and ranged from 0.87 to 3.48 mg/h for the adult breathing pattern. For the pediatric breathing pattern, drug delivery rate was a function of drug concentration and inspired minute ventilation and ranged from 0.41 to 1.83 mg/h. CONCLUSION: Our data demonstrate that drug delivery to the patient, expressed as inhaled mass over time, is similar for continuous nebulization (HEART system) and intermittently filled SVNs. In addition, for all nebulizers, the influence of the pediatric breathing pattern needs to be considered. Continuous nebulization permits the redistribution of health-care personnel and may reduce the costs of therapy.

Adrenergic beta-Agonists↗
PubMed1997

Measuring nebulizer output. Aerosol production vs gravimetric analysis.

STUDY OBJECTIVES: The function of jet nebulizers has been measured traditionally by gravimetric methods, i.e., by weighing nebulizers before and after nebulization. Newer techniques measure aerosol output directly by analyzing aerosolized drug or tracer, i.e., radioactive 99mTc. Because of evaporation, the equivalence of these methods is uncertain. The aim of this study was to determine if the gravimetric method is an accurate measure of aerosol production under different conditions of aerosol generation (i.e., nebulizer type, flow rate, pressure, volume fill, and concentration of solution used to nebulize a drug). METHODS: In the first phase of the study, we measured the aerosol output of nine commercially available jet nebulizers (AvaNeb; Up-Draft-Hudson RCI; Cirrus-Intersurgical Inc; DeVilbiss 646-DeVilbiss; Powermist-Hospitak, Inc; Respirgard II-Marquest Medical Products; Seamless-Seamless/Dart Respiratory; Salter; Salter Labs; Airlife-Baxter Health Care) run under commonly used conditions (2.5 mL volume fill, 2.0 mL normal saline solvent, 0.5 mL albuterol, flow of 6 L/min, and pressures averaging 15.0 +/- 2.3 [mean +/- SD] pounds per square inch [on the] gauge [psig] provided by a DeVilbiss PulmoAide compressor) with simultaneously measured gravimetrics and filtered radioactivity. Each nebulizer was run to dryness with data acquired every 2 min. The change in the weight of the nebulizer and radioactivity captured on the filter were expressed as percentages of the total in the nebulizer solution. In the second phase of the study, the experiments were repeated using the same nebulizers with a volume fill of 5 mL (diluted to half normal saline solution plus albuterol), flow of 10 L/min, and pressures of 35.6 +/- 8.8 psig. RESULTS: The cumulative (sum of all 2-min runs) weight loss for each individual nebulizer ranged from 25.00 to 64.55% and cumulative aerosol captured varied from 12.63 to 38.76%. While different, the weight loss and aerosol captured were closely correlated (y = -0.62 + 0.62x; r = 0.961, p < 0.0001). Changing volume fill and concentration of solvent did not affect this correlation (p = 0.921 and 0.373, respectively). However, changing flow from 6 L/min to 10 L/min significantly (p = 0.02) affected the relationship (y = -3.80 + 0.83x; r = 0.969, p < 0.001). CONCLUSIONS: When compared with direct methods such as filtering generated particles, the gravimetric method of assessing nebulizer function overestimates aerosol output by 1.8 +/- 0.18 times, presumably because of the loss of solvent during nebulization. However, the relationship between methods is predictable and appears unaffected by changing the type of nebulizer, volume fill, and concentration of solvent. Changes in nebulizer flow and pressure significantly affected the correlation. Gravimetric methods can be used as simple and convenient screening techniques for comparing jet nebulizers under a wide range of experimental conditions.

Adrenergic beta-Agonists↗
PubMed1996

Utility of technetium-99m-DTPA in determining regional ventilation.

UNLABELLED: The goal of this study was to determine the usefulness of radiolabeled aerosols in the assessment of regional ventilation in tracheotomized patients maintained on mechanical ventilation. METHODS: Three commercially available radioaerosol nebulizer kits were studied on the bench to determine nebulizer efficiency and particle distribution of 99mTc-DTPA aerosols. We studied ventilated tracheotomized human subjects with a gamma camera and simultaneously measured regional ventilation with 81mKr gas and 99mTc-DTPA aerosol. Images were compared by analysis of radioactivity distributions in computer-generated regions of interest. RESULTS: The UltraVent nebulizing system produced the smallest particles with a mass median aerodynamic diameter of 0.9 micron compared to the AeroTech I and Venti-Scan II systems, which both produced aerosols of 1.3 microns. Despite relatively small particle sizes, 99mTc-DTPA deposition images with the UltraVent nebulizer did not accurately represent regional ventilation as measured by 81mKr equilibrium. Visual inspection of images revealed significant amounts of particle deposition in the region of the trachea which was diminished but not eliminated following replacement of the tracheotomy tube inner cannula. Based on regional analysis, correlation between radioactivity distributions of both isotopes was poor (r = 0.262, p = 0.162) with segmental analysis suggesting that the upper and middle lung regions were significantly affected by residual tracheal activity. CONCLUSION: The lungs of patients maintained on mechanical ventilation can be imaged after the inhalation of 99mTc-DTPA from commercially available delivery kits, but the correlation between aerosol deposition and regional ventilation is poor. Better definition of ventilated lung segments is obtained when using a gas such as 81mKr because tracheal activity with the radiolabeled gas is minimized.

Adult↗
PubMed1991

Factors determining pulmonary deposition of aerosolized pentamidine in patients with human immunodeficiency virus infection.

Although aerosolized pentamidine (AP) has recently been approved for prophylaxis and is undergoing clinical trials for treatment of pneumocystis, pneumonia (PCP), factors important in the deposition of AP have not been described. Using radioaerosol techniques, deposition was measured in 22 patients receiving AP for prophylaxis or treatment of PCP. In all patients total and regional deposition of pentamidine, breathing pattern, pulmonary function (PFT), regional ventilation, and type of nebulizer were analyzed. Bronchoalveolar lavage (BAL) was performed 24 h after inhalation to assess the relationship between pentamidine levels in BAL fluid and measured aerosol deposition. The nebulizers tested were the Marquest Respirgard II and the Cadema AeroTech II, both previously characterized in our laboratory. The aerosol particles consist of water droplets containing dissolved pentamidine and technetium 99m bound to albumin. Analysis of particles sampled during inhalation via cascade impaction confirmed a close relationship between radioactivity in the droplets and the concentration of pentamidine as measured by HPLC (r = 0.971, p less than 0.0001; n = 18). Deposition was measured by capturing inhaled and exhaled particles on absolute filters and measuring radioactivity. This technique allows the determination of the deposition fraction (DF, the fraction of the amount inhaled that is deposited), which provides information on factors strictly related to the patient. To confirm the filter measurements, pentamidine deposition was also measured by gamma camera. The camera measurement was possible because each patient's thoracic attenuation of radioactivity was determined by a quantitative perfusion scan (mg pentamidine deposited via both techniques, r = 0.949, p less than 0.0001; n = 26). Regional lung volume and ventilation were determined by xenon 133 equilibrium scan and washout. Pentamidine deposition varied markedly between patients, but BAL levels of pentamidine significantly correlated with measured deposition (r = 0.819, p less than 0.01; n = 9). DF averaged 0.621 +/- 0.027 (SEM) and did not correlate with any measured lung parameter, including breathing pattern and PFT. Regional deposition did not correlate with regional ventilation. The major factor influencing pentamidine deposition was aerosol delivery (mg deposited versus mg inhaled; r = 0.963, p less than 0.0001; n = 26). The nebulizer was an important determinant of aerosol delivery, with the AeroTech delivering between 2.5 and 5 times more drug than the Respirgard. These observations are important in assessing treatment failure and cost of therapy.

Aerosols↗
PubMed1982

The impact of computer-age technology on respiratory therapy.

Computer-age technology is changing the face of respiratory therapy as it is that of nearly every other technical field. In some hospital respiratory therapy departments computers are presently being used for a wide range of functions such as blood gas result reporting, billing, budgeting, purchasing, hemodynamic calculations, and respiratory monitoring. Microprocessor-controlled ventilators and respiratory monitoring systems are becoming increasingly utilized. In the future the computer may actually operate the ventilator. But who is going to operate the computer? The new breed of intensivist will be trained in critical care medicine, respiratory therapy, biomedical engineering, and computer technology. Respiratory therapists must recognize and rise to the challenge that computer-age technology presents if they are to continue as intensivists. The worst possible development of the future for respiratory therapy would be for computer-age technology to be applied to respiratory therapy without the input and inclusion of respiratory therapists. The challenge then is to be adequately prepared to utilize and apply this inevitable new computer-age technology.

Blood Gas Analysis↗
PubMed1981

Comparison of the cerebral function monitor with the EEG in determining brain death.

The cerebral function monitor (CFM) is a portable electronic device that processes and records bipolar cortical electrical signals derived from two parietal scalp electrodes. Specific filtering and electronic rectification permit tracings of high quality to be obtained at any location, even where electrical interference and personal movements may render the conventional EEG difficult to interpret. In a comparison study of patients with clinically apparent brain death, CFM tracings that revealed no cerebral electrical activity correlated perfectly with isoelectric EEGs performed in a neurophysiology laboratory in 10 patients who manifested signs of absent brain stem function, a positive 3-min apnea test, and severe hypotension. All patients had a terminal cardiac arrest within 17 days of onset of coma; the mean survival time was 9 days. Thus, a strong though presumptive diagnosis of brain death may be made in those patients with absent electrical activity on the CFM and evidence of absent brain stem, i.e., respiratory center, function.

Adult↗