Sleep-related breathing disorders in infants with spina bifida repaired prenatally and postnatally.

STUDY OBJECTIVES: Advances in prenatal repair of myelomeningocele (MMC) have improved outcomes involving different organ systems. There is limited data on respiratory outcomes following prenatal surgical repair. We hypothesize there is no difference in respiratory outcomes between spina bifida (SB) patients who have undergone prenatal versus postnatal repair. METHODS: We performed a retrospective study of 46 infants <1 year with SB seen at Children's Hospital Los Angeles from 2004-2022. Demographic data, timing of closure, neonatal course, Chiari II malformation (CIIM), ventriculoperitoneal shunt (VPS), polysomnography (PSG) results, and need for supplemental oxygen were collected. Unpaired t-test and Chi-square Test were used to analyze results. RESULTS: 31/46 had prenatal repair of MMC; average age at repair was 27 weeks post-conception (PCA). Average age at postnatal repair was 37 PCA. There was no difference in age at PSG. There was no difference in CIIM presence (p=0.61). 60% of patients with postnatal repair and 23% in the prenatal group underwent VPS placement (p=0.01).There was no difference in PSG findings between the two groups: CAI (p=0.11), OAHI (p=0.64), average SpO2 baseline (p=0.91), average SpO2 nadir (p=0.17), average PETCO2 baseline (p=0.87), and average PETCO2 maximum (p=0.54). There were no significant differences in the proportion of patients on supplemental O2 (p=0.25), CSA or OSA between groups. CONCLUSIONS: Patients with SB who've undergone closure of neural tube defect have persistent central apneas, obstructive apneas, and significant hypoxemia. There were no differences in the frequency or severity of sleep-disordered breathing in those with prenatal repair versus postnatal repair.

Elevated transaminases in congenital central hypoventilation syndrome.

Patients with CCHS who also have Hirschsprung disease, elevated or low BMI, or pulmonary hypertension may be predisposed to elevated transaminases and may need periodic follow-up of their hepatic function https://bit.ly/3uW7AUG.

When to panic about a panic attack: A challenging case of hypersensitivity pneumonitis.

The COVID-19 pandemic has created diagnostic difficulties with the increase in mental health illnesses that often present with nonspecific symptoms, like hypersensitivity pneumonitis. Hypersensitivity pneumonitis is a complex syndrome of varying triggers, onset, severity, and clinical manifestations that can be challenging to diagnose in many cases. Typical symptoms are nonspecific and can be attributed to other entities. There are no pediatric guidelines, which contributes to diagnostic difficulties and delays in treatment. It is particularly important to avoid diagnostic biases, have an index of suspicion for hypersensitivity pneumonitis, and to develop pediatric guidelines as outcomes are excellent when diagnosed and treated promptly. This article discusses hypersensitivity pneumonitis with a focus on the causes, pathogenesis, diagnostic approach, outcomes, and prognosis while using a case to illustrate the diagnostic difficulties worsened by the COVID-19 pandemic.

Clinical Features of COVID-19 in Patients with Congenital Central Hypoventilation Syndrome.

Background: The clinical course of COVID-19 in patients with congenital central hypoventilation syndrome (CCHS) is unknown. Methods: We conducted a cross-sectional questionnaire study in 43 patients with CCHS who had COVID-19. Results: The median age of patients was 11 [interquartile range (IQR) 6-22] years and 53.5% required assisted ventilation (AV) through tracheostomy. Disease severity ranged from asymptomatic infection (12%) to severe illness with hypoxemia (33%) and hypercapnia requiring emergency care/hospitalization (21%), increased AV duration (42%), increased ventilator settings (12%), and supplemental oxygen demand (28%). The median duration to return to baseline AV (n = 20) was 7 (IQR 3-10) days. Patients with polyalanine repeat mutations required increased AV duration compared with those with nonpolyalanine repeat mutations (P = 0.048). Patients with tracheostomy required increased oxygen during illness (P = 0.02). Patients aged ≥18 years took longer to return to baseline AV (P = 0.04). Conclusions: Our study suggests that all patients with CCHS should be vigilantly monitored during COVID-19 illness.

Obstructive sleep apnea as a presentation of congenital central hypoventilation syndrome.

Congenital central hypoventilation syndrome is a rare disorder due to a mutation in the PHOX2B gene, characterized by a failure in autonomic control of breathing with diminished or absent response to hypoxia and hypercapnia, which is most pronounced during sleep. Most patients present from birth with central apneas and hypoventilation, or later in the setting of a physiologic stress. Recent literature in mice with a Phox2b27Ala/+ mutation suggests a predisposition to obstructive apneas likely due to hypoglossal dysgenesis. We report on three patients with obstructive sleep apneas with absent or mild hypoventilation. Our cases propose that obstructive apneas can be the primary presentation in patients who subsequently develop the classic phenotype of congenital central hypoventilation syndrome and emphasize their close monitoring and surveillance. CITATION: Kagan O, Zhang C, McElyea C, Keens TG, Davidson Ward SL, Perez IA. Obstructive sleep apnea as a presentation of congenital central hypoventilation syndrome. J Clin Sleep Med. 2023;19(9):1697-1700.

Congenital central hypoventilation syndrome without hypoventilation: is it congenital central hypoventilation syndrome?

Congenital central hypoventilation syndrome (CCHS) is a rare condition caused by pathogenic variants of the PHOX2B gene. There have been case reports describing variable phenotypes and mutations of the PHOX2B gene, not commonly tested for, that may challenge the classic definition of CCHS. We report on 3 family members with a rare heterozygous deletion encompassing the entire PHOX2B gene with variable phenotypes, including sleep-disordered breathing and autonomic nervous system involvement, but an unexpected lack of alveolar hypoventilation, which is usually a defining feature of CCHS. Our cases highlight the dilemmas in making a diagnosis of CCHS and emphasize the need for expanded genetic testing, including for PHOX2B gene deletion. More patients with variable phenotypes of CCHS may be identified through comprehensive genetic testing and warrant surveillance as they are still at risk for high-risk complications of CCHS. CITATION: Wo LL, Itani R, Keens TG, Marachelian A, Ji J, Perez IA. Congenital central hypoventilation syndrome without hypoventilation: is it congenital central hypoventilation syndrome? J Clin Sleep Med. 2023;19(6):1161-1164.

Perioperative outcomes and the effects of anesthesia in congenital central hypoventilation patients.

PURPOSE: Patients with congenital central hypoventilation syndrome (CCHS) have autonomic dysfunction and lack ventilatory responses to hypoxemia and hypercarbia and thus are prone to adverse events during general anesthesia. The objective of this study was to describe the perioperative outcomes of patients with CCHS who were undergoing diaphragm pacer (DP) implantation surgeries under general anesthesia. METHODS: A retrospective cohort study was conducted on patients with CCHS who underwent DP implantation surgeries at CHLA between January 2000 and May 2016. Charts were reviewed for demographics, PHOX2B genotype, ventilatory support, comorbidities, anesthesia administered, and perioperative courses. RESULTS: Of 19 patients with CCHS (58% female) mean age at surgeries was 8.6 ± 5.8 years. Seventeen patients were ventilator-dependent during sleep only; two were ventilator dependent 24 h per day. Mean surgery duration was 3.1 ± 0.5 h. Seventeen patients were extubated to PPV via tracheostomy in the OR. Two patients were extubated to NPPV on postoperative day (POD) 1. Mean transition time to home ventilator or NPPV was 3.0 ± 2.2 days, and mean hospital stay was 5.0 ± 2.1 days. One patient premedicated without ventilatory support developed hypoxemia and hypoventilation. Ten patients (52%) had intraoperative events such as bradycardia, hypotension, significant hypoxemia, and bronchospasm. Fifteen patients had postoperative events. Hypoxemia, pneumonia, and atelectasis accounted for most of perioperative complications. One patient experienced seizure on POD 2 due to hypercarbia. CONCLUSION: Patients with CCHS are vulnerable to the cardiorespiratory effects of sedative and anesthetic agents. Therefore, they require vigilant monitoring and optimal ventilatory support in the perioperative period.

High rates of anxiety detected in mothers of children with inconclusive cystic fibrosis screening results.

OBJECTIVE: The purpose was to assess postpartum depression, anxiety, and depression in mothers of children with an inconclusive diagnosis after a positive cystic fibrosis (CF) newborn screening (NBS), known as cystic fibrosis transmembrane conductance regulator (CFTR)-related metabolic syndrome (CRMS) or CF screen positive, inconclusive diagnosis (CFSPID). There is limited information on the prognosis and on the impact of this designation on maternal mental health. METHODS: Mothers of children with CRMS/CFSPID and CF identified by NBS were recruited from two centers in California. Maternal mental health was assessed using measures of depression, anxiety, and a scripted interview. Descriptive statistics and multivariate logistic regression were applied for data reporting. RESULTS: A total of 109 mothers were recruited: CF: 51, CRMS/CFSPID: 58. Mothers from both groups showed higher rates of depression and anxiety symptoms than women in the general population. CRMS/CFSPID and CF mothers had no significant difference on their self-reported symptoms of anxiety and depression after adjusting for potential confounders. Mothers equally reported that their child's diagnosis had a negative impact, and that genetic counseling had a positive impact on their emotional health. CONCLUSIONS: CF and CRMS/CFSPID diagnoses impact maternal mental health similarly. Uncertain prognosis of CRMS/CFSPID likely contributed to the negative mental health impact. Providers should consider conducting mental health screening for every mother of a child with CRMS/CFSPID, in addition to the recommended mental health screening for mothers of children with CF. Genetic counseling has potential to mitigate emotional stress on these families.

Transitional care and clinical management of adolescents, young adults, and suspected new adult patients with congenital central hypoventilation syndrome.

PURPOSE: With contemporaneous advances in congenital central hypoventilation syndrome (CCHS), recognition, confirmatory diagnostics with PHOX2B genetic testing, and conservative management to reduce the risk of early morbidity and mortality, the prevalence of identified adolescents and young adults with CCHS and later-onset (LO-) CCHS has increased. Accordingly, there is heightened awareness and need for transitional care of these patients from pediatric medicine into a multidisciplinary adult medical team. Hence, this review summarizes key clinical and management considerations for patients with CCHS and LO-CCHS and emphasizes topics of particular importance for this demographic. METHODS: We performed a systematic review of literature on diagnostics, pathophysiology, and clinical management in CCHS and LO-CCHS, and supplemented the review with anecdotal but extensive experiences from large academic pediatric centers with expertise in CCHS. RESULTS: We summarized our findings topically for an overview of the medical care in CCHS and LO-CCHS specifically applicable to adolescents and adults. Care topics include genetic and embryologic basis of the disease, clinical presentation, management, variability in autonomic nervous system dysfunction, and clarity regarding transitional care with unique considerations such as living independently, family planning, exposure to anesthesia, and alcohol and drug use. CONCLUSIONS: While a lack of experience and evidence exists in the care of adults with CCHS and LO-CCHS, a review of the relevant literature and expert consensus provides guidance for transitional care areas.

Impaired ventilation during 6-min walk test in congenital central hypoventilation syndrome.

BACKGROUND: Patients with congenital central hypoventilation syndrome (CCHS) can develop hypoxemia and hypercapnia during exercise. However, there is limited literature on cardiorespiratory responses during submaximal exercise and their correlation with paired-like homeobox 2B (PHOX2B) genotype. OBJECTIVES: To assess oxygen saturation (SpO2 ), end-tidal carbon dioxide (ETCO2 ), heart rate (HR), and 6-min walk distance (6MWD) during a 6-min walk test (6MWT) in CCHS subjects and to correlate them with PHOX2B genotypes and assisted ventilation (AV) via tracheostomy. METHODS: In this cross-sectional study, subjects with CCHS performed 6MWT with continuous pulse oximetry, HR, and capnography recorded before and during the 6MWT. Medical records were reviewed for PHOX2B genotype and phenotype data. Patients were categorized based on PHOX2B genotype and AV via tracheostomy. RESULTS: Fifteen subjects aged 10.5 (interquartile range 7.9-16.2) years completed the 6MWT. Nine subjects used AV via tracheostomy. Seven (47%) subjects developed hypoxemia (SpO2 ≤ 90%, n = 7) and hypoventilation (ETCO2 ≥ 50 mmHg, n = 3) during the 6MWT. There was a significant decline from baseline SpO2 , increase from baseline ETCO2 , and increase in HR during the 6MWT (all p < 0.05). Subjects had decreased median percent predicted 6MWD (59.7% [50.6%-62.5%]). Nadir SpO2 (p = 0.029) and peak ETCO2 (p = 0.046) differed significantly between PHOX2B genotype groups but 6MWD did not (p = 0.8). CONCLUSION: Despite normal oxygenation and ventilation at rest and during sleep on AV, patients with CCHS can develop hypoxemia and hypercapnia during submaximal exercise. Our study highlights the importance of assessing ventilatory responses during submaximal exercise in patients with CCHS regardless of their PHOX2B genotype.

Pediatric Cardiopulmonary Exercise Testing: Interoperability Through Domain Analysis Modeling and a National Survey.

PURPOSE: The electronic health record, data science advances, and dynamic environmental and infectious threats to child health highlight the need for harmonized and interoperable approaches to pediatric cardiopulmonary exercise testing (CPET). Accordingly, we developed a terminology harmonization in exercise medicine and exercise science domain analysis model (THEMES DAM) to structure CPET data elements. METHODS: THEMES DAM identified 114 data elements, including participant information, calibration, equipment, protocols, laboratory personnel, encouragement strategies, and analysis procedures. We used the THEMES DAM, vetted by the international data standards organization HL7, to construct a current-state survey of pediatric CPET centers in the United States. Forty-eight of 101 centers responded to a questionnaire covering seven major topic areas (38 items). RESULTS: Centers predominantly performed between 100 and 500 tests annually. Cardiac disease represented 55% of referrals. Almost all centers calibrated gas concentrations and flow daily, but 42% never calibrated their treadmill or cycle ergometers. All centers measured V̇O2peakbut calculated differently. Centers used a variety of protocols (e.g., for treadmill: 61%, Bruce; 43%, modified Bruce; 59%, other); 44% calculated CPET slopes from submaximal portions of CPET (e.g., V̇O2-HR). All centers verbally encouraged participants, but only 40% used a standardized approach. The interpretation of CPET was done by physicians (60%), exercise physiologists (25%), exercise technicians (10%), nurses (1%), or others (4%). Ninety-one percent would agree to collaborate in multicenter research, 89% to establish dynamic reference values, and 83% to better interpret CPET. CONCLUSIONS: The survey data and the implementation of THEMES DAM could accelerate interoperability across multiple centers. This would facilitate a nimble approach to create pediatric reference values responsive to the constantly changing health environment and stimulate novel approaches to CPET research and clinical application.

An unusual cause of diaphragm pacer failure in congenital central hypoventilation syndrome.

Congenital central hypoventilation syndrome is a rare genetic disorder affecting ventilatory response to hypercapnia and/or hypoxemia. We describe a case of diaphragm pacing (DP) failure in a 38-year-old woman with congenital central hypoventilation syndrome who used DP as ventilatory support only during sleep for 24 years. Diagnostic evaluation began with examination of external DP equipment, but adjustment did not elicit adequate diaphragm contractions. Clinical evaluation and transtelephonic monitoring showed absent function of the right pacer and diminished function of the left pacer. The patient had surgical exploration of her internal DP components. The operation revealed that the right pacer receiver had significant circumferential calcium accumulation. After replacement of the receivers in subcutaneous pockets closer to the skin surface, robust diaphragm contractions bilaterally occurred with stimulation. This case suggests DP failure can result from development of calcification and increased distance from the skin surface to the receivers due to weight gain. CITATION: Kwon A, Lodge M, McComb JG, et al. An unusual cause of diaphragm pacer failure in congenital central hypoventilation syndrome. J Clin Sleep Med. 2022;18(3):949-952.

Tracheostomy decannulation to noninvasive positive pressure ventilation in congenital central hypoventilation syndrome.

PURPOSE: Noninvasive positive pressure ventilation (NPPV) may permit tracheostomy decannulation (TD) in patients with congenital central hypoventilation syndrome (CCHS) requiring nocturnal positive pressure ventilation via tracheostomy (PPV-T). There is limited evidence on optimal strategies for transitioning patients from PPV-T to NPPV. This study aimed to describe the clinical course and outcome of children with CCHS who underwent TD and transitioned from PPV-T to NPPV. METHODS: Retrospective review was conducted on patients with CCHS using nocturnal PPV-T who underwent TD to NPPV. The results of clinical evaluations, airway endoscopy, polysomnography, and clinical course leading to TD were analyzed. RESULTS: We identified 3 patients with CCHS aged 8-17 years who required PPV-T only during sleep. Patients underwent systematic multidisciplinary evaluations with a pediatric psychologist, pulmonologist, sleep physician, and otolaryngologist utilizing a TD algorithm. These included evaluation in the sleep clinic, NPPV mask fitting and desensitization, endoscopic airway evaluation, daytime tracheostomy capping, acclimatization to low-pressure NPPV, polysomnography with capped tracheostomy and NPPV titration, and if successful, TD. All patients underwent successful TD following optimal titration of NPPV during polysomnography. The duration to TD from decision to pursue NPPV was between 2.4 and 10.6 months, and the duration of hospitalization for TD was between 4 and 5 days. There were no NPPV-related complications; however, all patients required surgical closure of tracheocutaneous fistula. CONCLUSION: NPPV may be an effective and feasible option for patients with CCHS requiring PPV-T during sleep and permits TD. In patients with CCHS, a systematic multidisciplinary algorithm may optimize successful transition to NPPV and TD.

Children with Congenital Central Hypoventilation Syndrome Do Not Wake up to Ventilator Alarms.

PURPOSE: Congenital Central Hypoventilation Syndrome (CCHS) requires lifelong ventilatory support during sleep. Subjects with CCHS are vulnerable to sleep disturbances associated with treatments, monitoring alarms, and care they receive. We hypothesized that sleep would be disrupted in patients  with CCHS due to ventilatory support and other treatments at night. METHODS: An anonymous survey of patients with CCHS, age up to 17 years was conducted through REDCAP. Subjects were recruited in person, by flyer, email, and social media. Data collected included demographics, PHOX2B genotype, ventilatory support, treatments, nursing, and sleep parameters. RESULTS: We received 23 responses (35% female, 8.1 years ± 5.6). PHOX2B genotypes were 20/24 PARM (2), 20/25 PARM (4), 20/26 PARM (2), 20/27 PARM (9), ≥ 20/28 PARM (2), and NPARM (2). Two subjects did not indicate the PHOX2B genotype. 13/23 were ventilated by PPV via tracheostomy, 7 by NIPPV, 2 by diaphragm pacing, and 1 did not indicate. Additional treatments received at night included suctioning (9), aerosol (1), G-tube feeding (2), and none (11). Only 9 received nursing at night. 13 used pulse oximetry for monitoring, and 9 used both pulse oximetry and end tidal CO2 monitor. 17/23 rarely woke up due to ventilator or monitor alarms. 11/23 usually or sometimes woke up at least once a night; only 2/11 woke up due to alarms. 5/17 who rarely woke up to the alarms had night nursing. CONCLUSION: Most subjects with CCHS did not awaken to ventilator or monitoring alarms and a majority of these patients did not have nighttime nursing. (Mathur et al. in Sleep 43(Supplement_1):A333, 2020).

Does acute flaccid myelitis cause respiratory failure in children?

INTRODUCTION: Acute flaccid myelitis (AFM) is a rare disease that affects spinal cord gray matter, results in acute flaccid weakness of one or more limbs and predominantly involves the cervical spinal cord, which places patients at higher risk for respiratory failure. Our study aims to describe respiratory failure in pediatric AFM patients with emphasis on the need for assisted ventilation and respiratory nerve involvement from an acute and long-term perspective. MATERIALS AND METHODS: We reviewed the medical records of patients diagnosed with AFM seen in a multidisciplinary clinic for persistent limb weakness between 2016 and 2020. RESULTS: We studied 54 patients, 35% were female. The median age of patients at illness onset was 5 years (range 7 months-19 years). The median age of patients at the time of study was 8.5 years (range 2-20 years). Eleven patients (20%) required assisted ventilation for acute respiratory failure. Of those that experienced acute respiratory failure, 81% developed chronic respiratory failure. Fifty-six percent of patients with chronic respiratory failure were able to wean off assisted ventilation by 1 year. All patients that experienced unilateral diaphragm impairment with AFM onset experienced acute and chronic respiratory failure. DISCUSSION: Many patients with AFM may experience respiratory compromise and develop chronic respiratory failure. However, most of these patients can be weaned off ventilatory support by 1 year from illness onset. Most children with unilateral diaphragm impairment can sustain adequate ventilation without the need for long-term ventilatory support.

Annual Respiratory Evaluations in Congenital Central Hypoventilation Syndrome and Changes in Ventilatory Management.

Background: Annual in-hospital respiratory evaluations (AREs) during wakefulness and sleep are recommended to assess ventilatory requirements in patients with congenital central hypoventilation syndrome (CCHS) aged ≥2-3 years based on expert consensus. This study aimed to determine if AREs in patients with CCHS led to changes in ventilatory management. Methods: Retrospective review of patients with CCHS who underwent AREs with or without polysomnography between 2017 and 2019 was conducted. Clinical symptoms, results of AREs, and subsequent changes in ventilatory management were analyzed. Results: We identified 10 patients with CCHS aged 4-20 years. All patients required assisted ventilation (AV) only during sleep delivered by positive pressure ventilation via tracheostomy (n = 7) or diaphragm pacing (n = 3). In total, 7 (70%) patients had abnormal oxygenation and/or ventilation requiring changes in ventilator settings or duration of AV. Six patients required an increase in settings and/or duration of AV, and only 1 patient required a decrease in ventilator settings. Two patients had awake hypercapnia during a routine outpatient visit that improved following increase in ventilator settings and a period of continuous AV. One patient who was previously ventilator-dependent only during sleep was identified to require 16 h per day of AV. All patients (n = 3) who reported symptoms such as headache or oxygen desaturations during sleep required an increase in ventilator settings. Conclusion: We report a high prevalence of changes in AV management following an ARE. Our results demonstrate the importance of regular AREs in patients with CCHS to assess their ventilatory requirements and optimize AV.

Variable phenotypes in congenital central hypoventilation syndrome with PHOX2B nonpolyalanine repeat mutations.

STUDY OBJECTIVES: Congenital central hypoventilation syndrome (CCHS) is a rare disorder affecting the autonomic nervous system that is caused by variants in the paired-like homeobox 2B (PHOX2B) gene. About 10% of patients with CCHS have nonpolyalanine repeat mutations (NPARM) that are associated with severe phenotypes requiring continuous assisted ventilation, Hirschsprung's disease, and increased neural crest tumor risk. However, some patients with NPARM have milder phenotypes. Our objective was to describe the phenotypes in patients with CCHS PHOX2B NPARM. METHODS: Retrospective case series of patients with CCHS PHOX2B NPARM was conducted at 2 children's hospitals to evaluate their phenotypes. RESULTS: We identified 8 patients with CCHS PHOX2B NPARM aged 3-31 years. Seven patients were diagnosed in infancy and 1 patient at 2 years of age. All patients presented with respiratory depression in the first 2 months of life. Only 1 patient was identified with a severe phenotype requiring continuous assisted ventilation, Hirschsprung's disease, and a neural crest tumor, which was resected. Five patients required positive pressure ventilation via tracheostomy only during sleep and 2 patients required oxygen only during sleep. Four patients had Hirschsprung's disease and 1 patient had a cardiac pacemaker due to a bradyarrhythmia. None of the patients had echocardiographic abnormalities. CONCLUSIONS: Patients with CCHS PHOX2B NPARM can have variable phenotypes, emphasizing the importance of implementing a plan of care that is individualized for each patient. The type of NPARM and their respective location on the PHOX2B gene may play a critical role in the severity of phenotypes displayed by each patient. CITATION: Kasi AS, Li H, Jurgensen TJ, Guglani L, Keens TG, Perez IA. Variable phenotypes in congenital central hypoventilation syndrome with PHOX2B nonpolyalanine repeat mutations. J Clin Sleep Med. 2021;17(10):2049-2055.

Abnormal Lung Clearance Index in Cystic Fibrosis Children with Normal FEV1 and Single-Breath Nitrogen Washout Test.

Single- and multiple-breath washout tests (SBW and MBW) measure ventilation inhomogeneity, but the relationship between them is unclear. Forty-three subjects with cystic fibrosis (CF) and healthy controls (HC) 8-21 years of age were recruited (CF = 30 and HC = 13) and performed nitrogen MBW, vital capacity SBW, spirometry, and plethysmography. Mean phase III slope from SBW (SIII) and lung clearance index (LCI) were significantly different between CF and HC (p = 0.017 and p < 0.0001, respectively). Based on Pearson correlation, SIII and LCI showed strong correlation (ρ = 0.81, p < 0.0001). Both SIII and LCI significantly correlated with spirometry (all p < 0.05). Among CF subjects with normal FEV1 (≥ 80%; n = 17), 76% (n = 13) had normal SIII but abnormal LCI. We conclude that LCI can be abnormal despite normal SIII and FEV1 in CF children. Although LCI and SIII showed strong correlation, our results suggest that LCI is a better test to detect ventilation inhomogeneity in CF children with normal FEV1.