Impact of viral respiratory infections on pulmonary exacerbations in children with cystic fibrosis.

BACKGROUND: Viral respiratory infections trigger pulmonary exacerbations (PEs) in children with cystic fibrosis (CF), but their clinical impact is not well understood. METHODS: A retrospective review of pediatric patients with CF who underwent nasopharyngeal respiratory viral panel testing during hospitalization for a PE between 2011 and 2018 was conducted. Patients were dichotomized into viral-positive and viral-negative groups. The results of spirometry, respiratory cultures, duration of hospitalization, and risk for subsequent PEs were analyzed. RESULTS: Ninety-five patients had 210 hospitalizations for PE (viral-positive = 71/210, 34%) during the study period. Rhinovirus/enterovirus was the most common virus (52/71, 73%) identified. Viral-positive patients were younger (p < 0.001), had higher baseline forced expiratory volume in 1 s (FEV1) (p = 0.037), continued to maintain higher FEV1 at 3 and 6 months following PE (p = 0.003 and 0.002, respectively), and had a shorter duration of hospitalization (p = 0.006) compared to the viral-negative group. There was no difference between the two groups in the rate of recovery of FEV1 at 3 and 6 months following PE (p = 0.71 and 0.405, respectively), time to the next PE (hazard ratio = 1.34, p = 0.157), number of subsequent PEs in 6 months (p = 0.99), or Pseudomonas aeruginosa (PA) acquisition (p = 0.707). CONCLUSIONS: In this single pediatric CF center cohort, one-third of PEs requiring hospitalization were associated with a viral infection, with rhinovirus/enterovirus being the most common. Viral-positive PEs were not associated with a greater decline or delayed recovery of lung function, increased risk for PA acquisition, shortened duration to next PE, longer hospital stay, or an increase in the frequency of subsequent PEs in 6 months compared to viral-negative PEs.

Improving lung function in adolescents with CF by tracking annual rate of lung function decline.

BACKGROUND: For patients with cystic fibrosis (CF), sustaining lung function through the adolescent years is crucial to slow the progressive decline that leads to significant morbidity and early mortality. This holds true for patients with high per cent predicted forced expiratory volume in 1 s (ppFEV1), as they may receive less vigilant monitoring and treatment. Early identification of lung function decline followed by aggressive treatment can lead to preservation of lung function. INTERVENTION: The Emory+Children's Pediatric Cystic Fibrosis Program implemented multiple quality improvement (QI) initiatives to identify and aggressively treat adolescent patients with a rapid decline in lung function. These initiatives included (1) lung zones to categorise and highlight lung function decline, (2) individual lung decline tables for quick reference, (3) a lung health algorithm to encourage uniformity, (4) a rapid decliner checklist to identify potential reasons for individual decline and (5) an automated individual patient-level data report and centre scorecard. We tested these interventions with plan-do-study-act cycles and refined as needed. RESULTS: Implementation of these QI initiatives resulted in overall improvement in lung function and slowing of lung function decline among adolescents with CF . This improvement could be attributed to the more standardised and proactive approach to decreases in lung function and the increased clinician attention to patients with rapid decline, especially for patients with high baseline ppFEV1.

Difference between SF6 and N2 multiple breath washout kinetics is due to N2 back diffusion and error in N2 offset.

Measurement of lung clearance index (LCI) by multiple breath washout (MBW) is a sensitive method for monitoring lung disease in patients with cystic fibrosis (CF). To compare nitrogen MBW (N2-MBW) and sulfur hexafluoride MBW (SF6-MBW), we connected these two gas analysis systems in series to obtain truly simultaneous measurements, with no differences other than the gas used. Nonsmoking healthy controls (HC) and subjects with CF were recruited at two institutions. The Exhalyzer-D (for N2-MBW measurement) was connected in series with the Innocor (for SF6-MBW measurement). Subjects washed in SF6 from a Douglas bag with tidal breathing and washed out SF6 and nitrogen with 100% oxygen provided as bias flow. Washout of both gases was continued past the LCI point (1/40th of equilibration concentration) in triplicate. N2-MBW resulted in higher cumulative exhaled volume, functional residual capacity (FRC), and LCI when compared with SF6-derived parameters in HC subjects (P < 0.0001 for all comparisons). All N2-MBW parameters were also significantly higher than SF6-MBW parameters in subjects with CF (P < 0.01 for all comparisons). After recalculation with a common FRC, N2-MBW LCI was higher than SF6-MBW LCI in subjects with CF (19.73 vs. 11.39; P < 0.0001) and in HC (8.12 vs. 6.78; P < 0.0001). Adjusting for N2 back diffusion and an offset error in the nitrogen measurement resulted in near complete agreement between the two methodologies. We found significant differences in LCI and FRC measurements using two different gases for MBW. This may have significant implications for the future use and interpretation of LCI data in clinical trials and routine clinical care.NEW & NOTEWORTHY This study provides important insights into the differences between the two techniques used for measuring lung clearance index (LCI): N2 and SF6 multiple breath washout. Differences between measurements made by these two methods in subjects with cystic fibrosis and healthy controls could be explained by nitrogen back diffusion and N2 offset error. This is important for use and interpretation of LCI data as an outcome measure for clinical trials and in routine clinical care.