Respiratory Care

We compared the amounts of bronchodilator delivered through an endotracheal tube (ETT) to a laboratory model of the neonate requiring ventilatory support. METHODS & MATERIALS: Albuterol (Proventil) from a nebulizer driven by a 6 L/min gas flow was delivered in three ways. In Method 1, the nebulizer was placed just proximal to the patient Y on the inspiratory limb of a ventilator circuit. In Method 2, the nebulizer was placed in-line on the inspiratory limb of a ventilator circuit with a 5-inch reservoir tube between the nebulizer and the patient Y. In Method 3, the outlet of the nebulizer T-piece was connected directly to the ETT. With the first two methods, ventilation was provided with a Sechrist IV-100B neo-natal ventilator, using continuous-flow and pressure-limited ventilation. In Meth-od 3, nebulized drug was delivered by manually inflating the lung model. Uniform ventilator settings were used with all three methods: rate 30 breaths/min, in-spiratory time 0.5 s, and peak inspiratory pressure 20 cm H2O. Aerosolized drug delivery at the end of the ETT was measured using a spectrophotometric tech-nique. RESULTS: The nebulizer proximal to the Y delivered 0.97% of the total dose placed in the nebulizer reservoir to the end of the ETT. The use of the res-ervoir tubing increased this to 1.78% of the dose. Manual inflation resulted in de-livery of 1.03% of the dose. Drug delivery was significantly greater with use of res-ervoir tubing than with the other two methods (p < 0.05), which did not differ from each other. CONCLUSION: The presence of a 5-inch reservoir between the gas-powered nebulizer and the Y adapter on the inspiratory limb of the ventilator circuit significantly increases the aerosolized bronchodilator delivered through a neonatal ETT, although only a small fraction of the total dose is delivered with any of the three methods examined.

BACKGROUND: We used a piglet model of respiratory failure to compare cardiopulmonary responses and pathologic effects on the airway mucosa and lung parenchyma of a combination of high frequency ventilation (HFV) and conventional breaths as provided by an electronic high frequency flow interrupter (HFFI) and a pneumatic oscillator (HFO). Unlike the HFFI, the HFO superimposed high frequency pulses on the conventional breaths. MATERIALS & METHODS: Twelve piglets (mean age 9 days, mean weight 2980 g), assigned at random to either ventilator, received lung lavage and 6 hours of ventilation (FIO2 1.0). Five additional piglets of similar characteristics received alternating HFFI and HFO. RESULTS: The combination of CMV and HFV was readily provided by both devices. Successful gas exchange was accomplished without cardiovascular compromise with either the well-known HFFI or the new pneumatic HFO. CONCLUSIONS: Absence of significant airway and lung injury suggests that the ventilatory strategies instituted resulted in alveolar recruitment and lung-volume maintenance. No beneficial effects of high frequency pulses superimposed on conventional breaths were observed in this study, but the unique capability of the pneumatic HFO to oscillate during lung inflations of different magnitudes and duration should be explored further.

BACKGROUND: Current-generation multichannel blood gas electrolyte analyzer systems (MBGES) have the ability to measure blood gases & electrolytes simultaneously. The proposed volume of sample required to achieve this is as little as 1.8 mL. Previous studies have identified inaccuracies & imprecision of blood gas and electrolyte results caused by anticoagulants & small sample size. However, the effects of these two variables on measured analyte parameters have not been addressed for simultaneous measurements on current-generation MBGES. We designed a prospective study to quantify errors introduced into blood gas & electrolyte measurements by sample size & concentration of dry lyophilized heparin during simultaneous analysis using a Corning 288 MBGES. METHODS: Arterial blood was collected from an arterially cannulated 33-year-old healthy Caucasian man. Seventy samples of blood were removed, comprising 10 randomly ordered sets of 0.2, 0.4, 0.6, 0.8, 1.0, 2.0, & 3.0 mL of blood; the resulting specimens contained ∼ 250, 125, 83, 63, 50, 25, & 17 IU of lithium heparin to 1.0 mL of blood, respectively. Sodium, potassium, ionized calcium, pH, PaO2, PaCO2, & total hemoglobin were all measured according to criterion standard for arterial blood gas analysis, collection, & calibration. RESULTS: Using analysis of variance & the Scheffe test, small sample volumes/high heparin concentrations resulted in lower sodium (p < 0.001) & ionized calcium (p < 0.001) and higher PaO2 (p = 0.03) values. No variations were found in potassium, PaCO2, or total hemoglobin. Sodium & ionized calcium concentrations are underestimated in sample volumes of < 0.6 mL with lithium heparin concentrations > 83 IU/mL. CONCLUSION: When standard samples are used with MBGES, we recommend a minimum 0.6-mL sample size for accurate & precise blood gas & electrolyte values.

Flexible fiberoptic bronchoscopy is a commonly performed procedure for which the indications, technical aspects, and potential patient complications have been well described. However, limited information is available regarding damage to the instrument itself. In order to better describe the types and causes of bronchoscope damage, repair costs, and time out of service, we performed a postal survey of hospital bronchoscopy laboratories in Alabama, Mississippi, and Louisiana. We received 43 completed surveys from laboratories that perform an average of 233 bronchoscopies per year. The respondents reported 103 episodes of bronchoscope damage, the majority of which consisted of damage to the bronchoscope cover, broken fiber bundles, malfunction of the bending apparatus, and suction channel damage. The respondents attributed 62% of all the damage to one of the three fol- lowing categories: unknown, improper handling, and damage caused by biopsy forceps, brushes, or needles. Of the 103 episodes of bronchoscope damage, 66 (64%) were judged to be preventable, 13.6% not preventable, and 17.5% to be in- determinant. The average time out of service (mean, SD) for each damaged bron- choscope was 3.5 (3.9) weeks, and the average repair cost per episode of broncho- scope damage was $2,726.13 ($1,391.21). At least 19 episodes of bronchoscope damage occurred during cleaning and disinfecting procedures. We conclude that the majority of bronchoscope damage and repair costs should be potentially pre- ventable and suggest that a program to familiarize all personnel handling bron- choscopes with proper maintenance and handling procedures should decrease the risk of bronchoscope damage.

INTRODUCTION: It is difficult to successfully suction the left bronchial tree. We evaluated the success rate of left bronchial cannulation with a new closed-suction directional-tip catheter (Trach Care directional-tip catheter, TCDT, Ballard Medical Products, Midvale UT). Success rates were compared in patients with endotracheal and tracheostomy tubes. We also studied the effects on success rate of (1) the distance of the endotracheal tube from the carina, (2) the tube's bevel orientation, and (3) the tube's position in the patient's mouth. METHOD: At the time of the routine daily chest radiograph, 75 attempts at left bronchial cannulation were made in 45 patients. With the head maintained in a midline position, the TCDT catheter was advanced with the radiopaque blue line in the 1 o'clock position. The radiograph was evaluated for correct placement of the TCDT catheter. RESULTS: Due to lung pathology and x-ray technique, catheter placement could not be interpreted in 17% of the radiographs. In the remainder, overall success rate was 71% (79% with tracheostomy tubes and 67% with endotracheal tubes, not significantly different, with p > 0.3). Tube distance from the carina and bevel orientation did not significantly affect success rates. Success rates for tubes located in the left and central positions of the patient's mouth were significantly better (p < 0.002 and p < 0.03, respectively) than for tubes located on the right side of the patient's mouth. With the endotracheal tube on the left side of the patient's mouth, the success rate was 89%. CONCLUSION: We conclude that the TCDT catheter successfully combines the features of a closed-suction system with those of a directional-tip catheter that allows selective bronchial cannulation, a large percentage of the time.

Contributions to this section are welcome. send double-spaced typed material (and illustrations if pertinent) to Historical Notes, RESPlRATORY CARE, 11030 Ables Lane, Dallas TX 75229-4593. Identify source of material and include your name, credentials, and address.

Each year a highlight of the Annual Meeting of the American Association for Respiratory Care, the RESPIRATORY CARE OPEN FORUM, provides a platform for the reporting and discussion of some of the clinical studies, methods and device evaluations, and case reports completed by members and friends during the previous year. During the 1992 OPEN FORUM in San Antonio, Texas, December 12-15, more than 120 papers will be presented- clustered into 12 minisymposia. The abstracts of those papers are published here, sequenced as they will be presented. An index of the authors appears on page 1372, with Presenters designated by boldface type.

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