Readministration of helper-dependent adenoviral vectors to mouse airway mediated via transient immunosuppression.

The efficacy of adenovirus-mediated gene therapy is attenuated by the host immune responses to both vector and transgene products. Even for helper-dependent adenoviral (HD-Ad) vectors, which have all viral-coding sequences deleted, the viral capsid proteins still cause immune reactions. In order to improve the efficiency in transgene expression during HD-Ad vector readministration, we administered cyclophosphamide to transiently modulate the mouse immune system. We delivered a high dose (5 × 10(10) vector particles (vp) per mouse) of empty HD-Ad to the mouse airway to induce an initial immune response. After 4 weeks, the mice were readministered with an HD-Ad vector containing either the reporter gene, LacZ, or the gene for the human cystic fibrosis transmembrane conductance regulator (CFTR) (1.5 × 10(10) vp per mouse). We found that the expression of both transgenes was greatly improved by the administration of cyclophosphamide when compared with the expression in mice without the immunosuppressing drug. We also found that the high dose of the empty HD-Ad vector administered intranasally does not induce an acute systemic immune response, but it does elicit an acute local response of proinflammatory cytokine production. Antibodies against Ad vector, including the neutralizing antibodies, were greatly reduced by the presence of cyclophosphamide in vector readministratiton. Moreover, cyclophosphamide reduced the infiltration of inflammatory cells, including total leukocytes, lymphocytes, CD4+ and CD8+T cells. These results indicate that transient administration of immunosuppressive agent can be used to extend transgene expression as well as attenuating immunogenicity to HD-Ad vectors in airway readministration.

Exercise capacity of children with pediatric lung disease.

BACKGROUND: Pulmonary function of children with cystic fibrosis (CF) and bronchopulmonary dysplasia (BPD) is similar at rest even though the mechanisms of injury differ. We sought to compare the peak exercise responses in children with BPD versus CF while controlling for pulmonary impairment, nutritional status, gender, age, height, and predicted forced expired volume in 1 second (approximately 73% of predicted). METHODS: Nine BPD children and 9 CF children underwent spirometry and a progressive exercise test to maximum on a cycle ergometer. RESULTS: There was no difference between groups in body mass percentile (CF:97 +/- 13%, BPD: 98 +/- 11%), peak power output (Wpeak) (CF:67 +/- 19 W, BPD:73 +/- 28 W), % predicted Wpeak (CF:83 +/- 28%, BPD:88 +/- 15%), peak oxygen uptake (VO2peak, CF: 38 +/- 7 ml/kg/min, BPD: 39 +/-6 ml/kg/min), or % predicted VO2peak (CF:99 +/- 16 %, BPD:96 +/- 27%). CONCLUSIONS: Children with mild pulmonary impairments are able to achieve a near normal peak power output and a normal VO2peak. Neither the aetiology nor the developmental onset of the process appears to be important influences on VO2peak or Wpeak.

Age- and size-related reference ranges: a case study of spirometry through childhood and adulthood.

Age-related reference ranges are useful for assessing growth in children. The LMS method is a popular technique for constructing growth charts that model the age-changing distribution of the measurement in terms of the median, coefficient of variation and skewness. Here the methodology is extended to references that depend on body size as well as age, by exploiting the flexibility of the generalised additive models for location, scale and shape (GAMLSS) technique. GAMLSS offers general linear predictors for each moment parameter and a choice of error distributions, which can handle kurtosis as well as skewness. A key question with such references is the nature of the age-size adjustment, additive or multiplicative, which is explored by comparing the identity link and log link for the median predictor.There are several measurements whose reference ranges depend on both body size and age. As an example, models are developed here for the first four moments of the lung function variables forced expiratory volume in 1 s (FEV(1)), forced vital capacity (FVC) and FEV(1)/FVC in terms of height and age, in a data set of 3598 children and adults aged 4 to 80 years. The results show a strong multiplicative association between spirometry, height and age, with a large and nonlinear age effect across the age range. Variability also depends nonlinearly on age and to a lesser extent on height. FEV(1) and FVC are close to normally distributed, while FEV(1)/FVC is appreciably skew to the left. GAMLSS is a powerful technique for the construction of such references, which should be useful in clinical medicine.

Sex differences in habitual physical activity and lung function decline in children with cystic fibrosis.

OBJECTIVES: To evaluate the feasibility of measuring habitual physical activity (HPA) in children with cystic fibrosis (CF) and to assess the relation between HPA and the rate of decline in FEV1 over a period of 2 years. STUDY DESIGN: At regular clinic visits, 109 patients (7 to 17 years; 56 girls) performed pulmonary function testing and completed the Habitual Activity Estimation Scale (HAES). Patients were divided into quartiles, based on activity levels derived from the HAES. RESULTS: Girls in the two lowest activity quartiles had a more rapid rate of decline FEV1 (-3.40% and -3.05% predicted, respectively) than girls in the two highest activity quartiles (-0.93% and +1.17% predicted, respectively) (P = .02). In boys, the rate of decline of FEV1 was similar in all activity quartiles (-1.95% predicted). Patients reported significantly more activity in summer compared with spring, winter, and fall (P < .0001), and boys reported greater activity than girls (6.5 +/- 2.9 vs 5.4 +/- 2.5 h/d, P < .05). CONCLUSIONS: The annual rate of change of FEV1 was related to activity quartile in girls but not in boys. This research suggests that an inactive lifestyle may partially explain the poorer survival of female patients with CF. The HAES is a feasible tool for routine follow-up of HPA in our CF clinic.

Does carbon dioxide retention during exercise predict a more rapid decline in FEV1 in cystic fibrosis?

BACKGROUND: Carbon dioxide (CO2) retention during exercise is uncommon in mild to moderate lung disease in cystic fibrosis (CF). The ability to deal with increased CO2 is dependent on the degree of airflow limitation and inherent CO2 sensitivity. CO2 retention (CO2R) can be defined as a rise in P(ET)CO2 tension of > or =5 mm Hg with exercise together with a failure to reduce P(ET)CO2 tension after peak work by at least 3 mm Hg by the termination of exercise. AIM: To ascertain if carbon dioxide retention during exercise is associated with more rapid decline in lung function. METHODS: Annual spirometric and exercise data from 58 children aged 11-15 years, with moderate CF lung disease between 1996 and 2002 were analysed. RESULTS: The mean FEV1 at baseline for the two groups was similar; the CO2R group (n = 15) was 62% and the non-CO2 retention group (CO2NR) was 64% (n = 43). The decline in FEV1 after 12 months was -3.2% (SD 1.1) in the CO2R group and -2.3% (SD 0.9) in the CO2NR group. The decline after 24 months was -6.3% (SD 1.3) and -1.8% (SD 1.1) respectively. After 36 months, the decline in FEV1 was -5.3% (SD 1.2) and -2.6% (SD 1.1) respectively. The overall decline in lung function was 14.8% (SD 2.1) in the CO2R group and 6.7% (SD 1.8) in the CO2NR group. Using the primary outcome measure as a decline in FEV(1) of >9%, final multivariate analysis showed that the relative risks for this model were (95% CIs in parentheses): DeltaP(ET)CO2 11.61 (3.41 to 24.12), peak VO2 1.23 (1.10 to 1.43), and initial FEV(1) 1.14 (1.02 to 1.28). CONCLUSION: Results show that the inability to defend carbon dioxide during exercise is associated with a more rapid decline in lung function.

Effect of size and disease on estimated deposition of drugs administered using jet nebulization in children with cystic fibrosis.

STUDY OBJECTIVES: To develop a model that quantified the nebulizer output that was inhaled by subjects with cystic fibrosis (CF) in order to predict the amount of drug likely to enter the upper airway contained in particles small enough to be deposited in the lower respiratory tract of individual patients. DESIGN: Forty-three patients (age, 6 to 18 years) with CF, with FEV(1) of 26 to 124% of predicted, breathed through a nebulizer circuit with a pneumotachograph in place at the distal end. Algorithms were developed from the measured flows through the pneumotachograph, allowing partitioning of inspiration into undiluted aerosol and fresh gas. In order to validate the algorithms, argon was added to the nebulizing gas flow and then its concentration was analyzed at the mouth by mass spectrometry. RESULTS: Predictions of the concentration of argon at the mouth were concordant with that measured by mass spectrometry, thus validating the model. Combining data from the model with in vitro nebulizer performance data, predictions for estimates for lung deposition for individuals were possible. Total estimate was independent of patient size or FEV(1). The respiratory duty cycle was 0.44 +/- 0.05 (mean +/- SD) and correlated (r = 0.91, p < 0.001) with estimated deposition and minute ventilation (r = 0.60, p < 0.01). However, when expressed in milligrams per kilogram of body weight, the estimated deposition in smaller children was fourfold higher than in larger children. CONCLUSIONS: If the effect of patient size and pattern of breathing on estimated drug deposition are not considered when prescribing drugs given by nebulization, the result may be overdosing younger children, underdosing older children, or both.

4A randomized trial of prolonged prone positioning in children with acute respiratory failure.

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 +/- 3.6 years) with ARF with a baseline oxygenation index (OI) of 22 +/- 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 = 0.0016). When patients were prone, a significant improvement in OI was detected (7.9 +/- 5.3; p = 0.002); this improvement occurred early (within 2 h in 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 (+ 6.6 +/- 15.2 mL/kg/12 h in PP vs + 18.9 +/- 13.6 mL/kg/12 h in SP; p = 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.

Nebulizer choice for inhaled colistin treatment in cystic fibrosis.

STUDY OBJECTIVES: To develop practical ways of nebulizing colistin by determining the rate of drug output, total drug output, and particle-size distribution of two commercially available jet nebulizers, the disposable Hudson 1730 Updraft II (Hudson Respiratory Care; Temecula, CA) and the reusable Pari LC Star breath-enhanced nebulizer (Pari Respiratory Equipment; Midlothian, VA). METHODS: The nebulizers contained colistin, 75 mg, in 4 mL of isotonic solution. Particle-size distribution was measured by helium-neon laser diffraction, allowing calculation of the respirable fraction (RF), the mass of aerosol comprised of droplets < 5 microm. RESULTS: The mean (95% confidence interval [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 relationship to the inspiratory flow, delivering 1.8 mg/min (0.7, 2.0; n = 4) with 1.4 mg/min (1.3, 1.6) within the RF, and 6.2 mg/min (5.6, 6.8) with 5.3 mg/min (4.8, 5.7) within the RF, at 0 L/min and 20 L/min inspiratory flows, respectively. Efficiency, as the rate of expected pulmonary deposition divided by rate of total output, was then calculated. The LC Star estimated 56% (51, 61) efficiency, with pulmonary delivery of 29% (26, 32) of the charge of the nebulizer, compared to the Updraft II at 22% (22, 23) efficiency and expected pulmonary deposition of 10% (10, 10) of the dose. CONCLUSIONS: Colistin can be successfully nebulized with both nebulizers tested. This study provides an estimate of in vivo efficiency and expected pulmonary deposition that may be used in future trials.

Evaluation of four breath-enhanced nebulizers for home use.

The objective of this study was to evaluate relative efficiency in vitro of four reusable breath-enhanced nebulizers (Pari LC Star, Medic-Aid Ventstream, Devilbiss PermaNeb, Salter Ultramist), and to integrate the in vitro performance data of the nebulizers with the respiratory patterns of four cystic fibrosis (CF) patients to compare efficiency in vivo of each device for each individual patient. Six nebulizers of each type were used to nebulize a solution of 2.5 mg (0.5 mL) albuterol with 3.5 mL of 0.9% saline. Total albuterol output and the rate of albuterol output of each device were measured until end-nebulization and for 4 min, respectively, using entrained flows from 0 to 20 L/min through the inspiratory valve of the device. Particle size distributions and the respirable fraction (RF) were evaluated by laser diffraction technique. Regression analysis of the change in rate of output and change in RF values with inspiratory flows was done to characterize each nebulizer's performance over the complete range of interest. Actual breath tracings of four CF patients were integrated with the equations specific to the in vitro performance of each nebulizer and in vivo nebulizer efficiency was calculated. The change in efficiency in vitro from 0 to 20 L/min flow, respectively, was highest for the Star (44-57%) and lowest for the Ultramist (13-15%). The mean predicted efficiency in vivo for the Star was threefold that of the Ultramist. Although all four nebulizers are breath-enhanced in design, clearly there are measurable differences in the performance and efficiency of each type. The Pari LC Star nebulizer has proven to be the nebulizer of choice among the devices tested.

Accounting for radioactivity before and after nebulization of tobramycin to insure accuracy of quantification of lung deposition.

The ability to predict drug deposition of inhaled drugs used in cystic fibrosis (CF) is important if there is a need to target specific doses of drug to the lungs of individual patients. The gold standard of measuring pulmonary deposition is the quantification of an aerosolized radiolabel either mixed with the drug solution or tagged directly to the compound of interest. Accuracy of the quantification could be assured if there is agreement between the amount of radioactivity before and after administration. Before administration, the radiolabel is concentrated in the well of the nebulizer, whereas after administration, it is distributed throughout the nebulizer, the expiratory filter and connectors, and the upper airway, stomach, trachea, and lung. Not only is the geometry of the distribution that is presented to the gamma camera different, but there are different attenuation factors for the various body tissues. The primary aim of this study was to evaluate the accuracy of the quantification of deposition. Secondary goals were to compare in vitro nebulizer performance with that measured in vivo during the deposition study. Eighty milligrams of tobramycin and technetium bound to human serum albumin was administered to 10 normal adults using a Pari LC Jet Plus (Pari Respiratory Equipment, Inc., Richmond, VA) breath-enhanced nebulizer. Techniques were developed that allowed for the accounting of 99 +/- 2% of the initial radioactivity. The fraction of the rate of lung deposition to total body deposition was the in vivo respirable fraction (0.62 +/- 0.07), which closely agreed with in vitro measurements of respirable fraction (0.62 +/- 0.04). Drug output measured from the change in weight and concentration in the nebulizer systematically overestimated drug output measured by the deposition study. The results indicate that 11.8 of the initial 80 mg would be deposited in the lungs. This technique could be adapted to accurately quantify the amount of deposition on any inhaled therapeutic agent, but caution must be used when extrapolating performance of a nebulizer on the bench to expected deposition in patients.

Inhaled mannitol identifies methacholine-responsive children with active asthma.

Inhaled mannitol has been developed for bronchial challenge testing in adults. This study determined if mannitol could identify children with active asthma and responsive to methacholine, and whether mannitol challenge was faster to complete than methacholine challenge. Twenty-five children (aged 6-13 years) responsive to methacholine and 10 nonasthmatic children unresponsive to methacholine were studied. The methacholine challenge (Cockcroft protocol) was followed by a mannitol challenge on separate days. Twenty-one asthmatic children were positive to mannitol. Three taking inhaled corticosteroids with borderline methacholine responsiveness did not respond to mannitol, and one could not complete the mannitol challenge due to cough. The geometric mean (GM) and 95% confidence interval (CI) for PD(15) for mannitol was 39 mg (19, 78), and PC(20) for methacholine was 0.6 mg/mL (0.35-1.02) (r(p) = 0.75, p < 0.001, n = 21). Responses to mannitol were repeatable: GM PD(15) for the first challenge was 29 mg (CI: 17,50), and for the second challenge, 33 mg (CI: 20, 55) (P = 0.44, n = 9). Mannitol was faster to administer than methacholine (median (range)) 14 min (5-32) vs. 29 min (19-49), respectively (P < 0.001). Time to recover to baseline FEV(1) spontaneously and after bronchodilator administration was similar for both challenges. There were no significant falls in arterial oxygen saturations. During mannitol challenge, the mean (SD) fall in FEV(1) in nonasthmatic children was 3.1% (2.9). We conclude that mannitol identifies children with airway hyperresponsiveness and is faster to perform than the methacholine challenge.

Severe bronchopulmonary dysplasia increases risk for later neurological and motor sequelae in preterm survivors.

Preterm children who develop severe chronic lung disease may be developmentally compromised by exposure to hypoxic episodes. This study aims to determine if children with severe bronchopulmonary dysplasia (BPD) who required home oxygen therapy were at greater risk for neurological and motor deficits at school age than preterm peers without BPD. This study evaluated 27 subjects with BPD and 27 preterm control infants matched for gestational age, birthweight, sex, and year of birth at a mean age of 9.9 years (2.0 SD) using standardized neuromotor outcome measures. Pair-matched comparisons and regression analyses were used to determine if subjects with BPD were at increased risk for neuromotor sequelae. Neurological abnormalities, including subtle neurological signs, cerebral palsy, microcephaly, and behavioral difficulties were highly prevalent in the BPD group (71% compared with 19% in control group, P<0.005). Over half the BPD cohort had difficulties in gross and/or fine motor skills. There were significant differences in postural stability between groups. Duration of hospitalization and home oxygen treatment, and decreased lung function at school age, markers of severity of illness, correlated with motor outcomes. The findings underline the importance of preventing the cardiorespiratory complications associated with chronic lung disease to minimize disability in preterm children. For children with severe BPD, better recognition and subsequent remediation of neuromotor impairments that manifest at school age may help maximize their functional potential.

Comparison of nebulized particle size distribution with Malvern laser diffraction analyzer versus Andersen cascade impactor and low-flow Marple personal cascade impactor.

Particle size of nebulized aerosols can be measured directly using laser diffraction or by evaluating aerodynamic properties by cascade impaction. As of today, there are no generally accepted standards for measuring particle size distribution from nebulizers. Laser diffraction has been questioned because of potential evaporative losses of the small particles at the edge of the plume, causing an apparent shift in the particle size distribution and thus a larger mass median diameter (MMD). When particle-sizing wet aerosols, cascade impaction may give rise to an apparent shift in the distribution, resulting in a smaller mass median aerodynamic diameter (MMAD) due to evaporative losses of aerosol droplets as they enter the impactor at ambient temperature. The modified low-flow Marple 296 Personal Cascade Impactor (MPCI) is currently being proposed as the European standard for wet aerosol analysis to minimize evaporative losses during sampling. The present study compared the particle size distribution of salbutamol and sodium cromoglycate aerosols nebulized by the Pari LC Star, using laser diffraction (Malvern Mastersizer X; MMX) and cascade impaction (Andersen Cascade Impactor [ACI] and the commercially available MPCI), which was either at ambient temperature or cooled to the nebulized aerosol temperature (10 degrees C). MMDs obtained with the MMX were virtually identical to the MMADs measured with both impactors when cooled with no significant differences in geometric standard deviation (sigma(g)). When the impactors were operated at ambient temperature, MMADs were smaller (18 to 30%) with a significantly larger sigma(g) (p < 0.05) compared to the MMX. These findings suggest that droplet distribution data for wet aerosol where evaporation process has not been minimized must be viewed with caution. There was no evidence suggesting a significant evaporative loss of small droplets from the edge of the plume during laser particle sizing. The MPCI does not minimize evaporative losses of aerosol particles during sampling.

Effect of dead volume on the efficiency and the cost to deliver medications in cystic fibrosis with four disposable nebulizers.

OBJECTIVES: To evaluate the factors that affect nebulizer efficiency and to compare the relative cost effectiveness of nebulized medications used in the treatment of cystic fibrosis (CF), delivered by four types of disposable jet nebulizers that are widely used in hospitals. DESIGN: The Hudson 1730 Updraft II, Baxter Misty-Neb, Marquest Whisper Jet (WJ), and Marquest Acorn II were evaluated in terms of respirable aerosol output (particles 5 microm or less), nebulizer dead (residual) volume (VD), and time for complete nebulization using saline, salbutamol and tobramycin at flows of 6 and 8 L/min. The respirable fraction (RF) was determined by laser diffraction, and drug output was calculated from the initial volume and concentration of the drug in the nebulizer minus the product of final drug concentration and the VD following nebulization. COST ANALYSIS: The expected pulmonary deposition (DE) was estimated, and incorporated with the material and labour costs to determine the cost effectiveness of each type of nebulizer. RESULTS: With a DE greater than two times that of the WJ at a cost of 2.4 times less, the Updraft II proved most efficient and cost effective of all the nebulizers evaluated in this study. CONCLUSIONS: The cost effectiveness of each nebulizer was determined by its efficiency, which in turn was predominantly related to its VD and RF at each flow. The efficiencies of these four devices were different and could not have been predicted from specifications provided by the respective manufacturers.

Do sinusoidal models of respiration accurately reflect the respiratory events of patients breathing on nebulizers?

The amount of drug that is delivered by nebulization is a combination of the physical properties of the agent being nebulized, the performance of the nebulizer, and the pattern of breathing of the patient. To avoid biological variation, mechanical models of breathing are frequently employed during the evaluation of the performance of a device. For simplicity, many investigators use sinusoidal models of breathing to calculate the expected inhaled mass, although some use square waves and other more complex models. Most assume that the duration of inspiration (Ti) is half of the total respiratory time (Ttot). This study compared the calculated inhaled mass from which the expected pulmonary deposition was estimated from the actual pattern of breathing of 43 children with cystic fibrosis (CF) breathing from an unvented nebulizer with a low dead volume and appropriate particle size distribution with that from a sinusoidal pattern of breathing using the same tidal volume (VT) and respiratory rate. The respiratory duty cycle (Ti/Ttot) was 0.45 +/- 0.05, which meant that less time was spent during inspiration than that found in a pure sinusoidal pattern. The difference between the predicted deposition from the actual pattern of breathing and that calculated from the sinusoidal model was 12 +/- 7%, which correlated with the respiratory rate (r = 0.67, P < 0.001). The degree of lung disease did not influence the discrepancy between the two values. In general, the actual VTs and respiratory rates were less in the patients than those employed in mechanical models of pediatric breathing. Although some patients had respiratory patterns that could be represented accurately with a sinusoidal model, most did not, and there were wide variations from child to child. These results suggest that there are both systematic and random errors arising from the use of a sinusoidal waveform to mimic respiratory events in patients.

Long-term pulmonary sequelae of severe bronchopulmonary dysplasia.

OBJECTIVE: To evaluate the long-term pulmonary sequelae of survivors of bronchopulmonary dysplasia (BPD) of sufficient severity to have required supplemental oxygen for at least 1 month after term. STUDY DESIGN: Fifteen patients with a mean age of 1.1 years were matched to preterm infants of similar gestational age and age at time of study. Pulmonary function testing included spirometry, plethysmographic lung volumes, carbon monoxide diffusion capacity, and in 9 of 15 subjects with BPD, measurement of lung static elastic recoil pressures. RESULTS: The subjects with BPD had a mean expiratory volume in 1 second (FEV1) of 64% +/- 21% predicted (4 had an FEV1 < 50% predicted) compared with 85% +/- 11% (P < .01) for the preterm children in the control group. Subjects with BPD had a significant degree of gas trapping with a residual volume to total lung capacity ratio of 37% +/- 13% compared with 25% +/- 4% for the control group (P < .01). An inverse relationship was seen between the FEV1 and the time on supplemental oxygen (r = -0.84, P < .0001), with 3 of the 4 children whose FEV1 was < 50% requiring oxygen for more than 900 days. Those with the greatest degree of airflow limitation and gas trapping had the greatest abnormalities in both shape and position of the pressure volume curves of the lung. CONCLUSION: Severe BPD may result in moderate to severe long-term abnormalities in pulmonary function tests.