Oral Alimentation in Neonatal and Adult Populations Requiring High-Flow Oxygen via Nasal Cannula.

Use of high-flow oxygen via nasal cannula (HFO2-NC) is increasingly common in intensive care unit (ICU) settings. Despite the critical interface between respiration and swallowing, and the high acuity of patients in ICUs, the impact of HFO2-NC on feeding and swallowing is unknown. The present prospective, single-center, cohort study investigated the impact of HFO2-NC use on oral alimentation in neonatal and adult ICU patients. Oral alimentation status was evaluated in 100 consecutive ICU inpatients (50 neonatal and 50 adult) requiring HFO2-NC. Participant characteristics, respiratory support, successful initiation of oral feeding in neonates, and successful resumption of oral feeding in adults were recorded. Seventeen of 50 (34 %) neonates requiring HFO2-NC were deemed developmentally and medically appropriate by the neonatologist and nursing to begin oral alimentation. All 17 (100 %) were successful with initiation of oral feedings. Thirty-three of 50 (66 %) continued nil per os due to prematurity or medical conditions precluding oral alimentation at time of data collection. Thirty-nine of 50 (78 %) adults requiring HFO2-NC were deemed medically appropriate by the intensivist and nursing to resume oral alimentation (n = 34) or with a functional swallow without aspiration on FEES (n = 5). All 39 (100 %) resumed oral alimentation successfully. Eleven of 50 (22 %) continued nil per os due to severe respiratory issues precluding both swallow testing and oral alimentation at time of data collection. All developmentally and medically appropriate neonatal and adult patients requiring HFO2-NC were successful with either the introduction or resumption of oral alimentation. Patients requiring HFO2-NC who are identified as having feeding or swallowing issues should be referred for swallowing evaluations using the same criteria as patients who do not require HFO2-NC, as it is not the use of HFO2-NC but rather patient-specific determinants of feeding and swallowing readiness and their underlying medical conditions that impact readiness for oral alimentation status.

Nasal insufflation treatment adherence in obstructive sleep apnea.

BACKGROUND: Nasal insufflation (NI) is a novel treatment method that has been introduced for improving respiration during sleep. NI's warmed and humidified nasal airflow provides ventilatory assistance delivered as a rapidly dispersed pressure head, with minimal side wall pressures, that may affect treatment tolerability. The aim of the current study was to investigate objective and subjective adherence rates for NI therapy in mild to moderate obstructive sleep apnea (OSA). METHODS: Ten patients (three men and seven women; age, 51.3 ± 9.6 years; BMI, 32.2 ± 7.7 kg/m2 [mean ± sd]) with recently diagnosed mild to moderate OSA (10.9 ± 5.8 events/h) were investigated. A crossover design was used to compare adherence to NI and continuous positive airway pressure (CPAP) therapy using a range of objective and subjective measurements. Objective (sleep efficiency (%) and arousal indices (arousal/h)) and subjective evaluations of sleep quality were carried out each night in the laboratory. During in-home treatment, adherence for both therapies was assessed objectively (time on therapy) and subjectively (self-reported sleep diary). RESULTS: Objectively derived adherence values were comparable for CPAP and NI, with both treatment devices sharing similar usage per night (3.5 ± 2.5 vs. 3.6 ± 1.6 h/night; respectively) and the number of nights with at least 4 h of treatment (5.5 ± 4.3 vs. 6.8 ± 3.3 nights/trial, respectively). Self-reported adherence was significantly higher than objectively assessed adherence (p < 0.03). CONCLUSIONS: This study showed similar adherence to NI and CPAP over a short period of usage. A randomized clinical trial is now essential for determining the comparative effectiveness of NI therapy in relation to treatment with CPAP.

Characterization of obstructive sleep apnea before and after tongue-lip adhesion in children with micrognathia.

OBJECTIVES: To characterize airway obstruction before and after tongue-lip adhesion in children with micrognathia using polysomnography. DESIGN: Retrospective pilot case series. PARTICIPANTS AND METHODS: Evaluation of all children with micrognathia who underwent tongue-lip adhesion and polysomnography before and after surgery from 2002 to 2007 (N  =  8). RESULTS: Eight children met inclusion criteria; six were girls. The mean interval between polysomnography and tongue-lip adhesion was 6 days (range, 2 to 13 days) preoperatively and 17 days (range, 5 to 32 days) postoperatively. Severe obstructive sleep apnea was identified in seven of eight (88%) children, with a mean preoperative obstructive apnea hypopnea index of 52.6 events per hour (range, 7.1 to 85.7 events per hour). None had significant central sleep apneas (>5 per hour). Tongue-lip adhesion resulted in a mean decrease of 34.5 events per hour (range, -65.8 to 71.6 events per hour). After tongue-lip adhesion, seven of eight (87.5%) patients had an improved obstructive apnea hypopnea index, with resolution of obstructive sleep apnea in one child and improvement to mild (two) and moderate (two) obstructive sleep apnea in four others. Only one child had an obstructive apnea hypopnea index that increased after tongue-lip adhesion. Peak end-tidal pCO(2) measurements were elevated in all eight children before surgery at a mean of 60 mm Hg (range, 52 to 76 mm Hg) that improved to 51 mm Hg (range, 45 to 59 mm Hg), with normal peak levels in four children. Oxygen saturation nadir improved from 73% (range, 58% to 81%) to 82% (range, 65% to 94%). CONCLUSIONS: Tongue-lip adhesion may be performed in micrognathic infants to alleviate airway obstruction. Polysomnographic evaluation in this pilot study before and after surgery suggests that tongue-lip adhesion usually improves obstructive sleep apnea, but only 38% had complete resolution. Future studies of tongue-lip adhesion efficacy should include polysomnographic evaluation.

Prevalence and severity of obstructive sleep apnea and snoring in infants with Pierre Robin sequence.

OBJECTIVE: To evaluate the prevalence and severity of obstructive sleep apnea in infants with Pierre Robin sequence prior to airway intervention and determine whether snoring correlates with the presence of obstructive sleep apnea in this population. DESIGN: Retrospective case series. SETTING: Urban tertiary care teaching hospital. PARTICIPANTS/METHODS: Review of infants with Pierre Robin sequence who underwent polysomnography in the first year of life from 2002 to 2007. Only results from the initial polysomnography were analyzed. A subgroup of consecutive prospectively tested patients was also evaluated. RESULTS: A total of 33 infants with Pierre Robin sequence were identified. Of these, 13 (39%), 11 girls and two boys, underwent polysomnography in the first year of life. The mean age at evaluation was 48 days (range, 7 to 214 days). Seven nonconsecutive and six consecutive patients were included, and no significant differences were seen between groups. Obstructive sleep apnea was identified in 11 of 13 (85%) infants. The mean obstructive apnea-hypopnea index was 33.5 (range, 0 to 85.7). Obstructive sleep apnea severity was mild in 2 of 11 (18%), moderate in 3 of 11 (27%), and severe in 6 of 11 (55%). Mean end-tidal Pco(2) measurements were elevated at 59 mm Hg (range, 47 to 76 mm Hg). Mean oxygen saturation nadir was decreased at 80% (range, 68% to 93%). Snoring occurred in only 7 of 13 (54%). Of the subjects with obstructive sleep apnea, snoring occurred in 6 of 11 (55%). CONCLUSION: The high incidence of obstructive sleep apnea in this group suggests that polysomnography should be promptly performed in children with Pierre Robin sequence. Although snoring was seen in the majority, the absence of snoring did not exclude the presence of obstructive sleep apnea.

Primary snoring and growth failure in a patient with cystic fibrosis.

An 8-year-old female with pancreatic-insufficiency cystic fibrosis presented with recurrent pharyngitis, and reduction in body mass index and height velocity during the previous 2 years. Her symptoms (eg, snoring and restless sleep) suggested obstructive sleep apnea, and physical examination revealed tonsillar hypertrophy. While her respiratory disturbance index on nocturnal polysomnography was normal, there was evidence of prolonged periods of snoring, associated with hypercapnia. Adenotonsillectomy decreased the snoring, improved her sleep, and in the 18-month follow-up period she had substantial weight-gain and growth improvement. This case demonstrates that adenotonsillar hypertrophy associated with recurrent pharyngitis and primary snoring might hinder growth in a patient with cystic fibrosis.

Upper airway neuromuscular compensation during sleep is defective in obstructive sleep apnea.

Obstructive sleep apnea is the result of repeated episodes of upper airway obstruction during sleep. Recent evidence indicates that alterations in upper airway anatomy and disturbances in neuromuscular control both play a role in the pathogenesis of obstructive sleep apnea. We hypothesized that subjects without sleep apnea are more capable of mounting vigorous neuromuscular responses to upper airway obstruction than subjects with sleep apnea. To address this hypothesis we lowered nasal pressure to induce upper airway obstruction to the verge of periodic obstructive hypopneas (cycling threshold). Ten patients with obstructive sleep apnea and nine weight-, age-, and sex-matched controls were studied during sleep. Responses in genioglossal electromyography (EMG(GG)) activity (tonic, peak phasic, and phasic EMG(GG)), maximal inspiratory airflow (V(I)max), and pharyngeal transmural pressure (P(TM)) were assessed during similar degrees of sustained conditions of upper airway obstruction and compared with those obtained at a similar nasal pressure under transient conditions. Control compared with sleep apnea subjects demonstrated greater EMG(GG), V(I)max, and P(TM) responses at comparable levels of mechanical and ventilatory stimuli at the cycling threshold, during sustained compared with transient periods of upper airway obstruction. Furthermore, the increases in EMG(GG) activity in control compared with sleep apnea subjects were observed in the tonic but not the phasic component of the EMG response. We conclude that sustained periods of upper airway obstruction induce greater increases in tonic EMG(GG), V(I)max, and P(TM) in control subjects. Our findings suggest that neuromuscular responses protect individuals without sleep apnea from developing upper airway obstruction during sleep.

Contribution of male sex, age, and obesity to mechanical instability of the upper airway during sleep.

Male sex, obesity, and age are risk factors for obstructive sleep apnea, although the mechanisms by which these factors increase sleep apnea susceptibility are not entirely understood. This study examined the interrelationships between sleep apnea risk factors, upper airway mechanics, and sleep apnea susceptibility. In 164 (86 men, 78 women) participants with and without sleep apnea, upper airway pressure-flow relationships were characterized to determine their mechanical properties [pharyngeal critical pressure under hypotonic conditions (passive Pcrit)] during non-rapid eye movement sleep. In multiple linear regression analyses, the effects of body mass index and age on passive Pcrit were determined in each sex. A subset of men and women matched by body mass index, age, and disease severity was used to determine the sex effect on passive Pcrit. The passive Pcrit was 1.9 cmH(2)O [95% confidence interval (CI): 0.1-3.6 cmH(2)O] lower in women than men after matching for body mass index, age, and disease severity. The relationship between passive Pcrit and sleep apnea status and severity was examined. Sleep apnea was largely absent in those individuals with a passive Pcrit less than -5 cmH(2)O and increased markedly in severity when passive Pcrit rose above -5 cmH(2)O. Passive Pcrit had a predictive power of 0.73 (95% CI: 0.65-0.82) in predicting sleep apnea status. Upper airway mechanics are differentially controlled by sex, obesity, and age, and partly mediate the relationship between these sleep apnea risk factors and obstructive sleep apnea.

Treatment alternatives for sleep-disordered breathing in the pediatric population.

UNLABELLED: PURPOSE FOR REVIEW: Childhood sleep-disordered breathing (SDB) is associated with a myriad of health problems that underscore the need for early diagnosis and treatment. Children with SDB present with behavior problems, deficits of general intelligence, learning and memory deficits, evidence of brain neuronal injury, increased cardiovascular risk, and poor quality of life. Children are in a rapid state of cognitive development; therefore, alterations of health and brain function associated with SDB could permanently alter a child's social and economic potential, especially if the disorder is not recognized early in life or is treated inadequately. RECENT FINDINGS: There is evidence that the majority of the problems associated with SDB improve with treatment. Treatment strategies are now being aimed at mechanisms underlying the disorder. There are multiple treatment options available to children; some are novel, with pending treatments on the horizon that may replace age-old therapies such as adenotonsillectomy or nasal positive pressure. SUMMARY: It is imperative that healthcare workers actively seek out signs and symptoms of SDB in patients to improve early detection and treatment for prevention of long-term morbidity.

Childhood obstructive sleep-disordered breathing: a clinical update and discussion of technological innovations and challenges.

Childhood sleep-disordered breathing (SDB) has been known to be associated with health and cognitive impacts for more than a century, and yet our understanding of this disorder is in its infancy. Neuropsychological consequences in children with snoring or subtle breathing disturbances not meeting the traditional definition of sleep apnea suggest that "benign, or primary snoring" may be clinically significant, and that the true prevalence of SDB might be underestimated. There is no standard definition of SDB in children. The polysomnographic technology used in many sleep laboratories may be inadequate to diagnose serious but subtle forms of clinically important airflow limitation. In the last several years, advances in digital technology as well as new observational studies of respiratory and arousal patterns in large populations of healthy children have led to alternative views of what constitutes sleep-related breathing and arousal abnormalities that may refine our diagnostic criteria. This article reviews our knowledge of childhood SDB, highlights recent advances in technology, and discusses diagnostic and treatment strategies that will advance the management of children with pediatric SDB.

Utilizing inspiratory airflows during standard polysomnography to assess pharyngeal function in children during sleep.

OBJECTIVES: Obstructive sleep apnea (OSA) is the result of pharyngeal obstruction that occurs predominantly during REM in children. Pathophysiologic mechanisms responsible for upper airway obstruction, however, are poorly understood. Thus, we sought to characterize upper airway obstruction in apneic compared to snoring children during sleep. We hypothesized that apneic compared to snoring children would exhibit an increased prevalence and severity of upper airway obstruction, that would be greater in REM compared to non-REM, and would improve following adenotonsillectomy. STUDY DESIGN: Apneic children were assessed with routine polysomnography before and after adenotonsillectomy, and compared to snoring children matched for gender, age, and BMI z-score. In addition to traditional scoring metrics, the following were used to characterize upper airway obstruction: maximal inspiratory airflow (%VI max) and percent of time with inspiratory flow-limited breathing (%IFL). RESULTS: OSA compared to snoring children had similar degrees of upper airway obstruction in non-REM; however, during REM, children with sleep apnea exhibited a higher %IFL (98 ± 2% vs.73 ± 8%, P < 0.01) and lower %VI max (56 ± 6 vs.93 ± 10%, P < 0.01). In children with OSA, CO2 levels were elevated during both wake and sleep. Following adenotonsillectomy, upper airway obstruction improved during REM manifest by decreased %IFL (98 ± 2 to 63 ± 9%, P = 0.04), increased %VI max (56 ± 6 to 95 ± 5%, P = 0.01) and decreased CO2 levels. CONCLUSIONS: Differences in the prevalence and severity upper airway obstruction suggest impaired compensatory responses during REM in children with OSA, which improved following adenotonsillectomy.

Polysomnographic Markers in Children With Cystic Fibrosis Lung Disease.

BACKGROUND AND OBJECTIVES: Children with cystic fibrosis (CF) often report poor sleep, increased daytime sleepiness, and fatigue. The purpose of this study was to identify respiratory patterns over the spectrum of disease severity in children with CF. The overall hypothesis for the current study is that children with CF compared with snoring control subjects demonstrate gas exchange abnormalities and increased respiratory loads during sleep that are not reported or recognized by conventional polysomnography (PSG). METHODS: Analysis of breathing patterns and gas exchange on PSG was performed in children with CF and healthy controls matched by age and BMI. For all CF and control subjects, the indication for PSG was evaluation for obstructive sleep apnea based on a history of snoring. RESULTS: Children with CF, compared with age- and BMI-matched snoring controls, demonstrated lower oxyhemoglobin saturation (95% ± 1.6% vs 98% ± 0.6%, P = .005), higher respiratory rate (19.5 ± 4.9 vs 16.5 ± 1.2 breaths per minute, P = .03), and a higher proportion of inspiratory flow limitation (44.1% ± 24.7% vs 12.1% ± 13.5%, P = .007) during non-rapid eye movement sleep. The respiratory disturbance index did not differ between CF and snoring control groups (1.5 ± 2.7 vs 0.6 ± 0.6 events per hour, P = .11). CONCLUSIONS: Children with CF exhibited abnormalities in gas exchange and increased respiratory load during sleep compared with normal age- and BMI-matched snoring controls. Because these abnormalities were independent of weight and lung function, sleep state may serve as an opportunity for early detection of breathing abnormalities and possibly CF lung disease progression.

Periodic limb movements in sleep and iron status in children.

STUDY OBJECTIVES: To assess potential relationships between serum iron and ferritin levels and the severity of periodic limb movement in sleep (PLMS) in a pediatric population, and to evaluate the response to supplemental iron therapy. DESIGN: A prospective study of all consecutively diagnosed children with PLMS (periodic limb movement index [periodic limb movements per hour of total sleep time, [PLMI] > 5) who underwent overnight polysomnographic evaluation. In all patients, complete blood count and serum iron and ferritin levels were obtained. Patients with serum ferritin concentrations less than 50 microg/L were prescribed iron sulfate at 3 mg/kg of elemental iron per day for 3 months. At the end of treatment, serum iron and ferritin levels and sleep studies were repeated. SETTING: Comprehensive Sleep Medicine Center, Tulane University Health Sciences Center, and Kosair Children's Hospital Sleep Medicine and Apnea Center. PATIENTS: Twenty boys and 19 girls with PLMS with a mean age of 7.5 +/- 3.1 years. INTERVENTION: Iron therapy. RESULTS: Twenty-eight (71.8%) patients had ferritin levels less than 50 microg/L. There was no significant correlation between serum ferritin concentration and PLMS severity as indicated by the PLMI (r = -0.19). The PLMI in patients with serum ferritin levels less than 50 microg/L (29.9 +/- 15.5 PLM/h) was higher than in patients with serum ferritin levels greater than 50 microg/L (21.9 +/- 11.8 PLM/h); however, the difference did not achieve statistical significance (P = 0.09). In contrast, serum iron was significantly correlated with PLMI (r = -0.43, P < 0.01). Indeed, patients with serum iron concentrations less than 50 microg/dL had a higher PLMI compared to patients with serum iron concentrations greater than 50 microg/dL (42.8 +/- 18.3 PLM/h and 23.1 +/- 10.1 PLM/h, respectively; P = 0.02). Twenty-five out of the 28 PLMS patients with serum ferritin levels less than 50 microg/L received treatment with iron sulfate, and 19 (76%) responded favorably. Among the responders to iron therapy, PLMI decreased from 27.6 +/- 14.9 PLM per hour to 12.6 +/- 5.3 PLM per hour after 3 months of iron supplements (P < 0.001) and coincided with increases in serum ferritin levels (pre: 40.8 +/- 27.4 microg/L vs post: 74.1 +/- 13.0 microg/L; P < 0.001). CONCLUSIONS: In children, the presence of PLMS is frequently associated with low serum iron and a tendency toward low serum ferritin levels. In addition, iron therapy is associated with clinical improvement in most of these patients.

Leptin and the control of pharyngeal patency during sleep in severe obesity.

RATIONALE: Obesity imposes mechanical loads on the upper airway, resulting in flow limitation and obstructive sleep apnea (OSA). In previous animal models, leptin has been considered to serve as a stimulant of ventilation and may prevent respiratory depression during sleep. We hypothesized that variations in leptin concentration among similarly obese individuals will predict differences in compensatory responses to upper airway obstruction during sleep. METHODS: An observational study was conducted in 23 obese women [body mass index (BMI): 46 ± 3 kg/m(2), age: 41 ± 12 yr] and 3 obese men (BMI: 46 ± 3 kg/m(2), age: 43 ± 4 yr). Subjects who were candidates for bariatric surgery were recruited to determine upper airway collapsibility under hypotonic conditions [pharyngeal critical pressure (passive PCRIT)], active neuromuscular responses to upper airway obstruction during sleep, and overnight fasting serum leptin levels. Compensatory responses were defined as the differences in peak inspiratory airflow (ΔVImax), inspired minute ventilation (ΔVI), and pharyngeal critical pressure (ΔPCRIT) between the active and passive conditions. RESULTS: Leptin concentration was not associated with sleep disordered breathing severity, passive PCRIT, or baseline ventilation. In the women, increases in serum leptin concentrations were significantly associated with increases in ΔVImax (r(2) = 0.44, P < 0.001), ΔVI (r(2) = 0.40, P < 0.001), and ΔPCRIT (r(2) = 0.19, P < 0.04). These responses were independent of BMI, waist-to-hip ratio, neck circumference, or sagittal girth. CONCLUSION: Leptin may augment neural compensatory mechanisms in response to upper airway obstruction, minimizing upper airway collapse, and/or mitigating potential OSA severity. Variability in leptin concentration among similarly obese individuals may contribute to differences in OSA susceptibility.

Approach for streamlining measurement of complex physiological phenotypes of upper airway collapsibility.

UNLABELLED: The critical closing pressure (PCRIT), a quantitative assessment of upper airway collapsibility, is derived from pressure flow relationship during sleep. The analytic generation of the pressure flow relationships are non-standardized due to various regression models (linear, spline, median), breath characteristics (flow limited, non-flow limited) or known covariates (sleep stage, body position). We propose a GUI based PCRIT Analysis Software (PAS) to streamline PCRIT analysis and validate its reliability and accuracy compared to current analysis procedures. METHODS: Seventeen subjects underwent a physiology sleep study in which the PCRIT was determined during NREM sleep. Data analysis was performed independently using three paradigms: (1) PAS (Igor Pro; median regression), (2) non-graphic statistics application (SAS; spline regression), and (3) manual spreadsheet calculations (Excel; linear regression). The reliability and accuracy of the PAS was examined through the agreement between each approach using Bland-Altman plots of the mean difference and within-individual variation using intra-class correlation (ICC). RESULTS: There was no difference in the group mean values for PCRIT using the PAS (-1.7 ± 0.7 cm H2O) compared to spline regression (-1.6 ± 0.7 cm H2O; p=0.69) or linear regression (-2.1 ± 0.7 cm H2O; p=0.92). The Bland-Altman analysis did not demonstrate a systematic bias between the PAS and either approach. There was a mean difference of 0.39 ± 0.2 cm H2O between the PAS and linear regression approaches, with upper and lower limits of agreement of 1.81 and -1.02 cm H2O, respectively. The PAS and spline analyses demonstrated an even smaller mean difference of -0.10 ± 0.1cm H2O, with upper and lower limits of 0.90 and -1.08 cm H2O, respectively. CONCLUSION: PAS preserves the reliability and accuracy of the original PCRIT analysis methods while vastly improving their efficiency through graphic user interface and automation of analytic processes. Providing a standardized platform for physiologic data processing offers the ability to implement quality assurance and control procedures for multicenter studies as well as cost saving by improving the efficiency of complex repetitive tasks.

Polysomnography in preterm infants and children with chronic lung disease.

OBJECTIVE: To determine the utility of overnight polysomnography (PSG) in assessing pulmonary reserve in stable preterm children with chronic lung disease (CLD). STUDY DESIGN: A retrospective review and descriptive study of overnight PSGs and clinic visits of preterm infants/children less than 3 years of age who were diagnosed with bronchopulmonary dysplasia at discharge from the hospital and enrolled in the Johns Hopkins CLD patient registry between 2008 and 2010. RESULTS: Sixty-two clinically stable patients underwent at least one overnight polysomnogram for clinical indications. The majority of patients were referred for oxygen titration (71%). PSGs from first studies revealed a mean respiratory disturbance index (RDI) of 8.2 ± 10.1 events/hr and a mean O(2) saturation (SaO(2) ) nadir of 86.2 ± 5.7%. In patients who underwent more than one PSG (n = 23), a significant decrease in RDI (P < 0.001) was found between the first study (mean age: 8.0 ± 3.3 months) and second study (mean age: 13.4 ± 5.2 months). Outpatient clinical measures of mean room air SaO(2) and respiratory rate were not predictive of PSG measures of RDI and SaO(2) nadir. CONCLUSION: Mean RDI was higher in stable preterm infants/children with CLD compared to previously published controls. RDI decreased with age in stable preterm infants/children with CLD suggesting improved pulmonary reserve with age. Outpatient clinical measures (respiratory rate and room air SaO(2) ) did not correlate with RDI and SaO(2) nadir indicating that overnight PSG is more sensitive in assessing pulmonary reserve than outpatient clinical measures.

Compensatory responses to upper airway obstruction in obese apneic men and women.

Defective structural and neural upper airway properties both play a pivotal role in the pathogenesis of obstructive sleep apnea. A more favorable structural upper airway property [pharyngeal critical pressure under hypotonic conditions (passive Pcrit)] has been documented for women. However, the role of sex-related modulation in compensatory responses to upper airway obstruction (UAO), independent of the passive Pcrit, remains unclear. Obese apneic men and women underwent a standard polysomnography and physiological sleep studies to determine sleep apnea severity, passive Pcrit, and compensatory airflow and respiratory timing responses to prolonged periods of UAO. Sixty-two apneic men and women, pairwise matched by passive Pcrit, exhibited similar sleep apnea disease severity during rapid eye movement (REM) sleep, but women had markedly less severe disease during non-REM (NREM) sleep. By further matching men and women by body mass index and age (n = 24), we found that the lower NREM disease susceptibility in women was associated with an approximately twofold increase in peak inspiratory airflow (P = 0.003) and inspiratory duty cycle (P = 0.017) in response to prolonged periods of UAO and an ∼20% lower minute ventilation during baseline unobstructed breathing (ventilatory demand) (P = 0.027). Thus, during UAO, women compared with men had greater upper airway and respiratory timing responses and a lower ventilatory demand that may account for sex differences in sleep-disordered breathing severity during NREM sleep, independent of upper airway structural properties and sleep apnea severity during REM sleep.

Chronic Lung Disease of Childhood: Control of Breathing During Wake and Sleep.

Control of breathing in infants during wake and sleep is immature at birth and undergoes rapid maturation over the first year of life. Infants with chronic lung disease (CLD) have multiple control of breathing impairments leaving them particularly vulnerable to hypoxic and asphyxic events. These impairments in the control of breathing are thought to contribute significantly to increased morbidity and the increased incidence of sudden infant death in infants with CLD. This review provides an overview of factors integral to the control of breathing during wake and sleep and factors that influence the development of control of breathing with a focus on the impact of CLD.

Performance characteristics of upper airway critical collapsing pressure measurements during sleep.

OBJECTIVE: The critical pressure (P(CRIT)), a measurement of upper airway collapsibility, is a determinant of the severity of upper airway obstruction during sleep. We examined the performance characteristics of the passive and active P(CRIT) by examining both within-night and between-night variability in the measurements. METHODS: We studied 54 sleep apnea patients (39 men, 15 women) and 34 normal subjects (20 men, 14 women) on either 1 or 2 nights during sleep. The P(CRIT) was measured during relative hypotonia ("passive" state) or during periods of sustained upper airway obstruction used to recruit upper airway neuromuscular responses ("active" state) within- and between-nights. In a subgroup of 10 normal subjects, we performed repeated measurements during hypnotic-induced sleep. Bland-Altman analyses were used to determine the within-night and between-night reliability of the P(CRIT) measurements. RESULTS: There were no significant within-night or between-night differences for the mean passive P(CRIT). The active P(CRIT) was ∼1 cm H(2)O more collapsible on the second night than on the first night. The limits of agreement, which bound the passive and active P(CRIT), was ∼ ± 3 cm H(2)O and was reduced to ∼ ± 1 cm H(2)O for the passive P(CRIT) with hypnotic-induced sleep. CONCLUSION: Passive and active P(CRIT) measurements are reasonably reliable within and between nights. An approximately 3 cm H(2)O change in passive or active P(CRIT) appears to represent the minimally significant change in P(CRIT) necessary to assess the effect of an intervention (e.g., positional therapy, surgical interventions, oral appliance effects, and pharmacotherapy) on upper airway mechanical loads or neuromuscular responses.