Comparison of sampler filling times among selected arterial blood samplers.

BACKGROUND: True arterial blood samples are essential in making clinical decisions for respiratory patients. Previous studies using only the Portex Pro-Vent arterial sampler have shown a significant difference between arterial and venous filling times. The goal of this study was to determine whether there is a statistically significant difference between sampler filling times measured at a normal mean arterial pressure among multiple arterial samplers with plungers and to determine whether there is a statistically significant difference in filling times between venous and normal mean arterial pressures for a sampler without a plunger. METHODS: We assembled an extracorporeal laboratory model to circulate a synthetic compound composed of 0.9% sodium chloride solution and Life/form artificial blood, and we used hemostats to create pressures within the circuit. We randomly selected samplers and measured the filling times of 4 arterial samplers with plungers at a normal mean arterial pressure (93 ± 1 mm Hg). We also measured the filling time of one arterial sampler without a plunger at a normal mean arterial pressure and at a simulated venous pressure (9 ± 2 mm Hg). We used the Kruskal-Wallis one-way analysis of variance to compare arterial filling times in samplers, and we used a t test for independent samples to compare venous and arterial filling times in the sampler without a plunger. RESULTS: There was a statistically significant difference between sampler filling times among the 4 arterial samplers with a plunger (P < .001). There was a statistically significant difference between arterial and venous pressure filling times for the sampler without a plunger (P < .001). CONCLUSIONS: Although there was a statistically significant difference between arterial filling times among various samplers with plungers, the difference was < 1 s and was not deemed clinically important. Regardless of the sampler brand being used, respiratory therapists and other clinicians performing arterial punctures can use sampler filling time to identify a successful arterial puncture while drawing blood.

The effects of abnormal blood pressure on arterial sampler filling times.

BACKGROUND: Sampler filling time begins with the initial flash of blood in the needle hub until the preset sampler volume is obtained. Previous studies have shown statistically significant differences between arterial and venous sampler filling times, but included only a few subjects with abnormal blood pressures. OBJECTIVE: To determine whether the time required to fill a vented arterial sampler is an accurate indication of a successful arterial blood sample in adults with abnormal blood pressure. We hypothesized that mean arterial pressure and arterial sampler filling time would have a negative correlation, and that venous sampler filling time would be significantly longer than arterial filling time. METHODS: We studied 40 subjects: 25 arterial subjects, and 15 venous subjects. The arterial subjects included 3 groups: hypertensive, hypotensive, or normal. During the arterial and venipuncture procedures, we measured sampler filling time and recorded blood volume. The PO2 of the samples was measured. Additionally, blood pressure and SpO2 were measured in the arterial group. RESULTS: The mean sampler filling time was 220.4 s/mL for the venous group, and 18.1 s/mL for all 3 arterial groups combined. There were significant differences between each mean arterial sampler filling rate and mean venous filling rate (P < .001). There were no significant differences in mean sampler filling rate between the arterial subgroups (P > .99). The correlation between mean arterial pressure and filling rates was 0.06 (P = .38). CONCLUSIONS: There is a significant difference between arterial and venous filling rates. There was no relationship between filling time and abnormal mean arterial pressure. Regardless of the arterial pressure, the arterial sampler filling time can be used as an indicator of a successful arterial puncture at the bedside.

Arterial sampler filling time during arterial and venous punctures, and its relationship with mean arterial pressure in human subjects.

BACKGROUND: When obtaining an arterial blood sample via percutaneous puncture, there is a risk of accidentally obtaining venous blood. Conventional methods of confirming arterial blood at the bedside, such as blood color and pulsatile return, can be misleading in patients with low blood pressure or hypoxemia. OBJECTIVE: To determine if the arterial sampler filling time can be an accurate indicator of obtaining an arterial blood sample in subjects with various blood pressures. Our hypotheses were that there would be a statistically significant negative correlation between sampler filling time during arterial puncture and mean arterial blood pressure, and a statistically significant difference between venous and arterial filling times in human adults. METHODS: Prior to an arterial puncture, we measured and recorded arterial blood pressure noninvasively. During the arterial and venipuncture procedures we measured the amount of time it took to fill the sampler and the volume of blood obtained. A t test for independent samples was calculated to determine if mean arterial sampler filling times were significantly different between the arterial and venous groups. Pearson correlation coefficient was calculated to determine the relationship between mean arterial pressure and seconds of filling time per milliliter in the arterial group. RESULTS: This study included 38 human subjects; 22 were adult patients ordered for arterial blood gases by arterial puncture; 16 were normal, healthy, adult volunteers who had a venipuncture performed using an arterial blood sampler. The mean ± SD filling time was 15 ± 4 s/mL for the arterial group and 115 ± 48 s/mL for the venous group, and the difference was significant (P < .001). The range of mean arterial pressures was 69-125 mm Hg; the average mean arterial pressure was 91 ± 13 mm Hg, and the Pearson correlation coefficient for mean arterial pressures and sampler filling times was -0.49 (P = .02). CONCLUSION: Our results were consistent with a laboratory study showing a significant difference between arterial and venous filling times and a negative correlation between mean arterial pressure and sampler filling time, but our times in adult subjects were longer. Respiratory therapists may find arterial sampler filling time as a useful indicator of successful arterial puncture at the bedside.

Effects of mean arterial pressure and needle size on arterial sampler filling time.

BACKGROUND: Arterial blood sampling is subject to numerous pre-analytical errors, one of which is inadvertent venous blood sampling. Especially when assessing oxygenation and titrating ventilation, accidental venous blood sampling may lead to inappropriate respiratory care and repeated percutaneous punctures. OBJECTIVE: To determine the effects of mean systemic blood pressure and needle size on vented arterial sampler filling times, to distinguish venous and arterial sampling. METHODS: We constructed an extracorporeal laboratory model to circulate whole blood at 4 L/min. We used hemostats to create 6 pressures: 57 mm Hg (representing a patient in shock), 70 mm Hg (representing a patient with low-normal blood pressure), 93 mm Hg (normal), 107 mm Hg (high-normal), 133 mm Hg (severe hypertension), and 14 (peripheral venous pressure). We simulated percutaneous punctures with vented arterial samplers preset to 2 mL, with 2 common sampling needles. We compared the filling times of each pressure/needle combination and determined the correlation between the mean pressure and filling time. RESULTS: For all the tested arterial pressures combined, the mean ± SD sampler filling time was 15.8 ± 0.4 s; for venous pressures the time was 51.4 ± 1.4 s (P < .001). With the 22-gauge/1.5-inch needles the sampler filling time was 22.2 ± 14.9 s. With the 23-gauge/1-inch needle the time was 21.4 ± 13.1 s (difference not significant). The Pearson correlation coefficient between the mean blood pressures and the sampler filling times was r(2) = -0.86 (P = .01). CONCLUSIONS: Lower blood pressure increased the sampler filling time. Measuring the filling time may enable therapists to confirm successful arterial puncture in adult patients. Confirming successful arterial puncture prior to blood analysis would expedite appropriate patient care decisions.

Effects of syringe material, sample storage time, and temperature on blood gases and oxygen saturation in arterialized human blood samples.

BACKGROUND: The practice of on-ice storage of arterial-blood samples in plastic syringes for delayed analysis continues, and the effects of storage time and temperature on the measurement of blood-oxygen-saturation values (S(aO2)) have not been adequately described. OBJECTIVE: To determine the effects of syringe material, storage time, and storage temperature on normal arterialized blood gas and S(aO2) values. METHODS: We used a temperature-controlled extracorporeal circuit to "arterialize" 500 mL of fresh, whole human blood at 37 degrees C, and we used certified calibration gases of 12% O2 and 5% CO2 to produce normal blood-gas values. From that arterialized blood we took 90 samples and randomly assigned them to 6 groups, until there were 15 samples in each group. The groups were (1) plastic syringe, analyzed immediately, (2) plastic syringe, stored 30 min at 0-4 degrees C, (3) plastic syringe, stored 30 min at 22 degrees C, (4) glass syringe, analyzed immediately, (5) glass syringe, stored 30 min at 0-4 degrees C, and (6) glass syringe, stored 30 min at 22 degrees C. RESULTS: Compared to the samples that were analyzed immediately, the P(O2) of the samples stored in plastic syringes for 30 min at 22 degrees C and at 0-4 degrees C was significantly higher, with a clinically important magnitude of 11.9-13.7 mm Hg. The P(CO2) of blood stored in glass for 30 min at 0-4 degrees C was significantly lower, although the magnitude of the difference (1.5 mm Hg) was not clinically important. There were no statistically significant differences in pH or oxygen saturation among the 6 groups. CONCLUSION: For accurate arterial-blood-gas results, samples drawn in plastic syringes should be analyzed immediately. If the analysis is going to be delayed, the samples should be drawn and stored in glass.

Bachelor of science degree education programs: organization, structure, and curriculum.

Therapists with bachelor's degrees in respiratory therapy have become the new advanced clinicians of the twenty-first century. Although the opportunity has increased in recent years, earning a baccalaureate degree in respiratory therapy remains a limited option. The "2-year preprofessional plus 2-year respiratory therapy" is the most popular curriculum design, but several other notable designs also fulfill the definition of a bachelor's degree in respiratory therapy. Two landmark documents issued in 2003 make strong arguments for expanding opportunities for baccalaureate education in respiratory therapy. Recognizing the "need to increase the number of respiratory therapists with advanced levels of training and education to meet the demands of providing services requiring complex cognitive abilities and patient management skills," the American Association for Respiratory Therapy has strongly encouraged the continuing development of baccalaureate education. Strategies for expanding baccalaureate opportunities include increasing the number and capacities of traditional programs, creating more articulation and bridge agreements between community and junior colleges with 4-year colleges and universities, and offering baccalaureate respiratory therapy through distance education. For the profession of respiratory therapy to require a baccalaureate at entry level, expansion of baccalaureate education will be necessary, and educators, managers, practitioners, and professional leaders will need to pursue all viable strategies. As an interim phase in the evolution of the profession, Becker suggests a strategy of"reprofessionalism" aimed at assisting therapists currently in the workforce to complete their degrees. Through a combination of strategies, a bachelor's degree in respiratory therapy will inevitably become the standard for clinicians in the decades to come.

A comparison of the therapeutic effectiveness of and preference for postural drainage and percussion, intrapulmonary percussive ventilation, and high-frequency chest wall compression in hospitalized cystic fibrosis patients.

INTRODUCTION: Cystic fibrosis (CF) patients have abnormally viscid bronchial secretions that cause airway obstruction, inflammation, and infection that leads to lung damage. To enhance airway clearance and reduce airway obstruction, daily bronchopulmonary hygiene therapy is considered essential. OBJECTIVE: Compare the effectiveness of and patient preferences regarding 3 airway clearance methods: postural drainage and percussion (PD&P), intrapulmonary percussive ventilation (IPV), and high-frequency chest wall compression (HFCWC). METHODS: The participants were hospitalized CF patients >or= 12 years old. Effectiveness was evaluated by measuring the wet and dry weights of sputum obtained with each method. In random order, each patient received 2 consecutive days of each therapy, delivered 3 times daily for 30 minutes. Sputum was collected during and for 15 minutes after each treatment, weighed wet, then dried and weighed again. Participants rated their preferences using a Likert-type scale. Mean weights and preferences were compared using analysis of variance with repeated measures. Patient preferences were compared using Freidman's test. RESULTS: Twenty-four patients were studied. The mean +/- SD wet sputum weights were 5.53 +/- 5.69 g with PD&P, 6.84 +/- 5.41 g with IPV, and 4.77 +/- 3.29 g with HFCWC. The mean wet sputum weights differed significantly (p = 0.035). Wet sputum weights from IPV were significantly greater than those from HFCWC (p < 0.05). The mean dry sputum weights were not significantly different. With regard to overall preference and to the subcomponents of preference, none of the 3 methods was preferred over the others. CONCLUSIONS: HFCWC and IPV are at least as effective as vigorous, professionally administered PD&P for hospitalized CF patients, and the 3 modalities were equally acceptable to them. A hospitalized CF patient should try each therapy and choose his or her preferred modality.