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Background Tidal volumes standardized to predicted body weight are recommended for adult mechanical ventilation, but children are frequently ventilated by using measured body weight. The goal of this study was to examine the difference in FVC (in milliliters per kilogram [mL/kg]) by using measured body weight compared with predicted body weight in children. Methods This retrospective analysis included outpatient pulmonary function tests (PFTs) from two datasets. Dataset one included 6- to 19-year-old patients undergoing PFTs from the nationally representative Canadian Health Measures Survey. Dataset two included 6- to 20-year-old patients undergoing PFTs at a freestanding children's hospital. FVC mL/kg values were analyzed against BMI z scores to show changes in FVC vs BMI between measured and predicted weight. Results Dataset one included 5,394 PFTs from the Canadian survey. FVC from measured weight decreased as the BMI z score group increased. The median FVC from measured weight was 81.4 mL/kg in the lowest BMI z score group and 51.7 mL/kg in the highest BMI z score group. FVC from predicted weight increased slightly with increasing BMI z score group. Dataset two included 8,472 patient PFTs from clinical measurement. A decline in median FVC from measured weight (from 69.4 to 37.6 mL/kg) as BMI z score group increased was also seen. Conclusions FVC differs significantly when standardizing to measured weight vs predicted weight. Obese children have lung volumes reflecting their predicted body weight from height. Children with low or normal BMI have lung volumes reflecting measured body weight. These findings suggest that targeting tidal volume by using the lower of measured and predicted body weights would be the most lung-protective strategy.

Tidal volumes standardized to predicted body weight are recommended for adult mechanical ventilation, but children are frequently ventilated by using measured body weight. The goal of this study was to examine the difference in FVC (in milliliters per kilogram [mL/kg]) by using measured body weight compared with predicted body weight in children.This retrospective analysis included outpatient pulmonary function tests (PFTs) from two datasets. Dataset one included 6- to 19-year-old patients undergoing PFTs from the nationally representative Canadian Health Measures Survey. Dataset two included 6- to 20-year-old patients undergoing PFTs at a freestanding children's hospital. FVC mL/kg values were analyzed against BMI z scores to show changes in FVC vs BMI between measured and predicted weight.Dataset one included 5,394 PFTs from the Canadian survey. FVC from measured weight decreased as the BMI z score group increased. The median FVC from measured weight was 81.4 mL/kg in the lowest BMI z score group and 51.7 mL/kg in the highest BMI z score group. FVC from predicted weight increased slightly with increasing BMI z score group. Dataset two included 8,472 patient PFTs from clinical measurement. A decline in median FVC from measured weight (from 69.4 to 37.6 mL/kg) as BMI z score group increased was also seen.FVC differs significantly when standardizing to measured weight vs predicted weight. Obese children have lung volumes reflecting their predicted body weight from height. Children with low or normal BMI have lung volumes reflecting measured body weight. These findings suggest that targeting tidal volume by using the lower of measured and predicted body weights would be the most lung-protective strategy.

Inhaled colistin is used for the treatment of Pseudomonas aeruginosa infection in cystic fibrosis (CF) patients despite reports of chest tightness and bronchospasm. The main objective of the study was to assess whether bronchospasm occurred in pediatric CF patients with or without clinical evidence of airway hyperreactivity.A prospective placebo-controlled clinical trial with crossover design was devised using challenge tests with 75 mg colistin in 4 mL saline solution and a placebo solution of the same osmolarity using a breath-enhanced nebulizer for administration. Subjects were recruited as follows: high risk (HR) for bronchospasm due to a personal history of recurrent wheezing, a family history of asthma and/or atopy, or bronchial lability, as demonstrated in pulmonary function tests; or low risk (LR) without these characteristics.The mean FEV(1) (expressed as the mean [+/- SD] fall from baseline) of the HR group (n = 12) fell 12 +/- 9% after placebo was administered, and fell 17 +/- 10% after colistin was administered. For the LR group (n = 8), the mean FEV(1) fell 9 +/- 4% following placebo administration and 13 +/- 8% following colistin administration. There was a greater number of subjects in the HR group compared to the LR group, which had a mean fall in FEV(1) of/= 15% (p0.01) after inhaling colistin. The differences between placebo and colistin therapy in the LR group were not significant.The results demonstrated that colistin can cause bronchospasm, particularly in those patients with coexisting CF and asthma.

Objectives: To evaluate differences between three new-generation nebulizers—Pari LC Star (Pari Respiratory Equipment; Mississauga, ON, Canada), AeroEclipse (Trudell Medical International, London, ON, Canada), and Halolite (Medic-Aid Limited, West Sussex, UK)—in terms of rate and amount of expected deposition as well as the consistency of the doses delivered. Methods: The in vitro performance characteristics were determined and then coupled to the respiratory pattern of seven patients with cystic fibrosis (age range, 4 to 18 years) in order to calculate expected deposition. The Pari LC Star and AeroEclipse were characterized while being driven by the Pari ProNeb Ultra compressor (Pari Respiratory Equipment) for home use, and by a 50-psi medical air hospital source. The Halolite has its own self-contained compressor. Algorithms for the rate of output for the inspiratory flow were developed for each device. Patient flow patterns were divided into 5-ms epochs, and the expected deposition for each epoch was calculated from the algorithms. Summed over a breath, this allowed the calculation of the estimated deposition for each patient’s particular pattern of breathing. Results: The rate of deposition was highest for the Pari LC Star and lowest for the Halolite. Rate of deposition was independent of respiratory pattern for the Pari LC Star and AeroEclipse, but proportional to respiratory rate for the Halolite. The differences between the Pari LC Star and AeroEclipse were less when driven by the 50-psi source. The AeroEclipse had the least amount of drug wastage. As designed, the Halolite delivered a predetermined amount of drug very accurately, whereas expected deposition when run to dryness of the other two devices had significant variations. Conclusions: To minimize treatment time, the Pari LC Star would be best. To minimize drug wastage, the AeroEclipse would be best. To accurately deliver a specific drug dose, the Halolite would be best.

To compare drug output from a vented nebulizer (Pari LC Jet Plus) with a traditional unvented nebulizer (Hudson 1730 T Up-Draft 11) using aerosolized tobramycin, which is frequently used in the treatment of cystic fibrosis.Six nebulizers of each type were filled with a 4 mL tobramycin (80 mg) solution and were driven by a compressor (Pulmo-Aide). Various inspiratory flows (VI) (0, 5, 10, 15, 20 L/min for the Pari LC Jet Plus and 0, 5, and 10 L/min for the Hudson 1730, all at 40% relative humidity) were directed through each nebulizer. Drug output was measured from changes in weight and concentration (assessed by changes in osmometry) within the nebulizer. Particle size distributions were determined by laser diffraction allowing the calculation of the amount of aerosol output in the respirable range (5 microm). The nebulizers were first run until end-nebulization to establish total drug output and then for either 4 or 5 min to determine the rate of drug output (mg/min) before intermittent aerosol output.The total drug output without VI for both the unvented and the vented nebulizers was not significantly different, 55 (51, 60) mg for the Hudson 1730 vs 51 (49, 53) mg for the Pari LC Jet Plus (mean [95% confidence limits]). Inspiratory flow had no effect on the unvented Hudson 1730 nebulizer but significantly increased the rate of total drug output and the rate of drug output in the respirable range for the vented Pari LC Jet Plus nebulizer (VI=0, 3.35 [2.84, 3.85] and 1.72 [1.48, 1.96] compared with VI=20, 9.87 [9.03, 10.70] and 6.11 [5.33, 6.88] mg/min).These findings indicate that the increase in the rate of drug output with VI for the vented nebulizer would result in shorter nebulization times and a relative decrease in drug loss during the expiratory phase.

The use of inhaled antibiotics in the treatment of cystic fibrosis has become widespread despite controversy in the literature as to the appropriate dosing regimen and its effectiveness. This study compared two tobramycin (T) preparations (one with and one without the addition of albuterol) using two different jet nebulizers in order to determine if drug output would be affected. Using calibrated flows from a dry compressed gas source of 6 and 8 L/min as well as a specific compressor (Pulmo-Aide), the Hudson 1720 nebulizer was compared with the newer disposable Hudson 1730. The albuterol preparation used in this study was the Ventolin (albuterol) Respirator Solution (VRS). The nebulizers were charged with (1) 2 mL T (80 mg/2 mL) with 0.5 mL VRS (5 mg/mL) and normal saline solution to make the total nebulizer charge of 3 or 4 mL, or (2) 2 mL T and either 1 or 2 mL normal saline solution. A laser diffraction analyzer (Malvern 2600) was used to determine the aerosol particle size distribution. From the distribution, the respirable fraction, which is the fraction of aerosol that could enter and remain in the lungs, was calculated. For all solutions and each particular flow, the Hudson 1730 had a larger respirable fraction of T. The addition of VRS lowered the surface tension of the solution in the nebulizer and resulted in a greater output of T. This effect was most apparent for the 3-mL volume fills of the Hudson 1720. The greatest differences were between the 3-mL nebulizer charges of T using the Hudson 1720 driven by a flow of 6 L/min, which produced 8 mg of T in the respirable fraction, compared with 35 mg produced by the Hudson 1730 driven by a flow of 8 L/min. These results suggest that different nebulizers, different nebulizer solutions, and different techniques of nebulization may result in very different amounts of T aerosol output in the respirable fraction.

The time course of inspiration has been shown to have a significant influence on the subsequent maximal expiratory flows and timed forced expiratory volumes in healthy adults and those with COPD. The purpose of this study was to evaluate the effect of two different inspiratory maneuvers on the spirogram in 15 patients with cystic fibrosis, aged 13 to 35 years, who had mild to moderate airway obstruction. Patients performed a forced expiratory maneuver either after a rapid inspiration without an end-inspiratory pause or after a slow inspiration with a 4-s end-inspiratory pause. Flow-time and volume-time curves were measured by a pneumotachograph. The mean values of FVC, FEV 1 , and peak expiratory flow were significantly larger by 11%, 13%, and 26%, respectively, after the rapid inspiration without an end-inspiratory pause compared to the slow inspiration with the end-inspiratory pause. This discrepancy probably reflects differences in effective elastic recoil pressure between the two maneuvers. Although the nature of this phenomenon is not fully understood, our results show that for spirometry in patients with cystic fibrosis, the preceding inspiratory maneuver influences the results. An important corollary is that this inspiratory maneuver should be standardized.

Study objective: To compare the effect of the prone position (PP) vs supine position (SP) on oxygenation in children with acute respiratory failure (ARF). Design: Prospective, randomized controlled trial. Setting: A 36-bed pediatric critical-care unit in a tertiary-care, university-based children’s hospital. Patients: Ten children (mean [SD] age, 5 6 3.6 years) with ARF with a baseline oxygenation index (OI) of 22 6 8.5. Interventions: Following a period of stabilization in the SP, baseline data were collected and patients were randomized to one of two groups in a two-crossover study design: group 1, supine/prone sequence; group 2, prone/supine sequence. Each position was maintained for 12 h. Lung mechanics and acute response to inhaled nitric oxide were examined in each position. Measurements and main results: OI was significantly better in the PP compared to the SP over the 12-h period (analysis of variance, p 5 0.0016). When patients were prone, a significant improvement in OI was detected (7.9 6 5.3; p 5 0.002); this improvement occurred early (withi n2hi n 9 of 10 patients) and was sustained over the 12-h study period. Static respiratory system compliance and resistance were not significantly affected by the position change. Inhaled nitric oxide had no effect on oxygenation in either position. Urine output increased while prone, resulting in a significantly improved fluid balance (1 6.6 6 15.2 mL/kg/12 h in PP vs 1 18.9 6 13.6 mL/kg/12 h in SP; p 5 0.041). No serious adverse effects were detected in the PP. Conclusion: In children with ARF, oxygenation is significantly superior in the PP than in the SP. This improvement occurs early, remains sustained for a 12-h period, and is independent of changes in lung mechanics. (CHEST 2001; 119:211‐218)

Study objectives: To develop practical ways ofnebulizing colistin by determining the rate of drug output, total drugoutput, and particle-size distribution of two commercially availablejet nebulizers, the disposable Hudson 1730 Updraft II (Hudson Respiratory Care; Temecula, CA) and the reusable Pari LC Starbreath-enhanced nebulizer (Pari Respiratory Equipment; Midlothian, VA). Methods: The nebulizers contained colistin, 75 mg, in 4 m, L of isotonic solution. Particle-size distribution was measuredby helium-neon laser diffraction, allowing calculation of therespirable fraction (RF), the mass of aerosol comprised of droplets Results: The mean (95% confidenceinterval [CI]) total rate of output of the Updraft II was 2.6 mg/min(2.0, 3.1; n = 4) with 1.3 mg/min (1.0, 1.5) mg/min within the RF. The rate of output of the LC Star increased in a quadratic relationshipto the inspiratory flow, delivering 1.8 mg/min (0.7, 2.0; n = 4) with1.4 mg/min (1.3, 1.6) within the RF, and 6.2 mg/min (5.6, 6.8) with 5.3mg/min (4.8, 5.7) within the RF, at 0 L/min and 20 L/min inspiratoryflows, respectively. Efficiency, as the rate of expected pulmonarydeposition divided by rate of total output, was then calculated. The LCStar estimated 56% (51, 61) efficiency, with pulmonary delivery of29% (26, 32) of the charge of the nebulizer, compared to the Updraft II at 22% (22, 23) efficiency and expected pulmonary deposition of10% (10, 10) of the dose. Conclusions: Colistin canbe successfully nebulized with both nebulizers tested. This studyprovides an estimate of in vivo efficiency and expectedpulmonary deposition that may be used in futuretrials.

Although a fall in arterial oxygen saturation (SaO2) during exercise has been reported in patients with advanced lung disease due to cystic fibrosis (CF), not every patient with advanced disease desaturates, and pulmonary function tests have not been considered predictive as to which patient will desaturate. This study evaluated oxygen desaturation by ear oximetry during a progressive exercise test in 21 patients with CF and compared it to forced expiratory volume in one second (FEV1), the forced vital capacity (FVC) and the single breath diffusing capacity for carbon monoxide (DCO), all expressed as percent predicted. During exercise, the SaO2 fell less than 0.25 percent per ml of the maximal O2 consumption per kilogram of body weight to values never less than 90 percent in 15 patients (group A), whereas it fell more than this and always to values at the end of exercise of less than 90 percent in six others (group B). The FEV1 ranged from 103 percent predicted to 37 percent for group A compared to 28 to 17 percent in group B, while the range of FEV1/FVC was 87 to 52 percent for group A and 54 to 40 percent for group B. The range of DCO for group A was 129 to 84 percent compared to 64 to 54 percent. In conclusion, this study found that both the FEV1 and the DCO could separate those that had significant desaturation from those that did not and that no patient with a DCO of 80 percent or greater had significant desaturation during exercise.

The popularity of the maximum expiratory flow-volume curve (FVC) is in part due to the effort independence of expiratory flow. Of interest are expiratory flow rates at specific lung volumes, usually 50 and 25 percent of vital capacity (VC); V ˙ max50 and V ˙ max25, which make accurate assessment of lung volumes essential. Changes in lung volume during the test are due to both the volume of gas expired and the volume change due to gas compression (Vcomp). In normal subjects, Vcomp is small but may be considerable in those with airflow obstruction. When the FVC is measured in a plethysmograph (FVCp), both expired volume and Vcomp are measured. When the volume of the FVC is derived from gas expired at the mouth (FVCm), Vcomp is not considered and differences in V ˙ max25 or V ˙ max50 may occur. The magnitude of these errors was assessed in 30 children and young adults: nine normal subjects, ten with cystic fibrosis (CF) and 11 with asthma. For V ˙ max50, use of FVCm instead of FVCp resulted in an error of 8 ± 7 percent (mean ± 1 SD) in the normal subjects compared to 32 ± 23 in those with CF (p 1 or RV/TLC but were related to a combination of expiratory effort, the shape of the FVCp, and the absolute volume of gas that was being compressed (p