Richard J Schwab

Southwestern PA Pulmonary & Sleep Medicine Ltd., Washington, Pennsylvania, United States

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Publications (107)380.98 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Sleep is an important physiologic process and lack of sleep is associated with a host of adverse outcomes. In addition, both basic and clinical research has documented the important role circadian rhythm plays in biologic function. Critical illness is a time of extreme vulnerability for patients and the important role sleep may play in recovery for ICU patients is just beginning to be explored. This concise clinical review will focus on the current state of research examining sleep in critical illness. We will discuss sleep and circadian rhythm abnormalities that occur in ICU patients and the challenges to measuring alterations in circadian rhythm in critical illness. In addition we will review methods to measure sleep in the ICU including polysomnography, actigraphy and questionnaires. We will discuss data on the impact of potentially modifiable disruptors to patient sleep, such as noise, light and patient care activities, and report on potential methods to improve sleep in the setting of critical illness. Finally we will review the latest literature on sleep disturbances that persist or develop after critical illness.
    American Journal of Respiratory and Critical Care Medicine 01/2015; · 11.04 Impact Factor
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    ABSTRACT: Sleep disordered breathing (SDB) is associated with significant cardiovascular sequelae and positive airway pressure (PAP) has been shown to improve heart failure and prevent the recurrence of atrial fibrillation in cardiac patients with sleep apnea. Patients who are hospitalized with cardiac conditions frequently have witnessed symptoms of SDB but often do not have a diagnosis of sleep apnea. We implemented a clinical paradigm to perform unattended sleep studies and initiate treatment with PAP in hospitalized cardiac patients with symptoms consistent with SDB. We hypothesized that PAP adherence in cardiac patients with SDB would reduce readmission rates 30 days after discharge.
    Journal of clinical sleep medicine: JCSM: official publication of the American Academy of Sleep Medicine 09/2014; · 2.93 Impact Factor
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    ABSTRACT: Rationale: Body habitus is a major determinant of obstructive sleep apnea (OSA). However, many individuals do not have OSA despite being overweight/obese (body mass index, BMI>25 kg/m2) for reasons that are not fully elucidated. Objectives: To determine the key physiological traits (upper-airway anatomy/collapsibility, upper-airway muscle responsiveness, chemoreflex control of ventilation, arousability from sleep) responsible for the absence of OSA in overweight/obese individuals. Methods: We compared key physiological traits in 18 overweight/obese non-apneics (apnea-hypopnea index, AHI<15 events/hr) to 25 overweight/obese matched OSA patients (AHI≥15 events/hr), and 11 normal-weight non-apneic controls. Traits were measured by repeatedly lowering continuous positive airway pressure to sub-therapeutic levels for 3 min during non-REM sleep. Measurements and Main Results: Overweight/obese non-apneics exhibited a less collapsible airway than overweight/obese apneics (Pcrit: -3.7±1.9 vs. 0.6±1.2 cmH2O, P=0.003; mean±95%CI.), but a more collapsible airway relative to normal-weight controls (-8.8±3.1 cmH2O, P<0.001). Notably, overweight/obese non-apneics exhibited a 3-fold greater upper-airway muscle responsiveness than both overweight/obese apneics (Δgenioglossus EMG/Δepiglottic pressure: -0.49[-0.22 to -0.79] vs. -0.15[-0.09 to -0.22] %/cmH2O, P=0.008; mean[95%CI]) and normal-weight controls (-0.16[-0.04 to -0.30] %/cmH2O; P=0.02). Loop gain was elevated (more-negative) in both overweight/obese groups vs. normal-weight controls (p=0.02). Model-based analysis demonstrated that overweight/obese non-apneics rely on both more favorable anatomy/collapsibility and enhanced upper-airway dilator muscle responses to avoid OSA. Conclusions: Overweight/obese non-apneics have a moderately-compromised upper-airway structure that is mitigated by highly-responsive upper-airway dilator muscles to avoid OSA. Elucidating the mechanisms underlying enhanced muscle responses in this population may provide clues for novel OSA interventions.
    American Journal of Respiratory and Critical Care Medicine 09/2014; · 11.04 Impact Factor
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    ABSTRACT: Background Elevated levels of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) may contribute to cardiovascular disease and are associated with obstructive sleep apnea (OSA) and obesity. The relationship between OSA and obesity in determining ICAM-1 and VCAM-1 levels, and the effect of treatment, is unclear.Objective Our aim was to study whether positive airway pressure (PAP) usage resulted in changes in ICAM-1 and VCAM-1 after 2 years within 309 OSA patients from the Icelandic Sleep Apnea Cohort, and determine how obesity affected such changes.Subjects/Methods The mean body mass index (BMI) was 32.4±5.1 kg/m(2); subjects had moderate-to-severe OSA (apnea-hypopnea index=45.0±20.2) and 79% were male. There were 177 full PAP users (⩾4 hours/night and ⩾20 of last 28 nights), 44 partial (<4 hours/night or <20 nights), and 88 non-users.ResultsICAM-1 (P<0.001) and VCAM-1 (P=0.012) change was significantly different among the PAP groups. The largest ICAM-1 differences were among the most obese subjects (P<0.001). At follow-up, non-users had increased ICAM-1 compared to decreased levels in full users. All groups had increased VCAM-1, but non-users had a significantly larger increase than full users.Conclusion Within moderate-to-severe OSA patients, PAP usage prevents increases in adhesion molecules observed in non-users after two years. For ICAM-1, the largest effect is in the most obese subjects. As OSA and obesity commonly coexist, the usage of PAP to limit increases in adhesion molecules may decrease the rate of progression of OSA-related cardiovascular disease.International Journal of Obesity accepted article preview online, 21 July 2014; doi:10.1038/ijo.2014.123.
    International Journal of Obesity 07/2014; · 5.39 Impact Factor
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    ABSTRACT: Body Correlations between UA Soft Tissue Structures and Pcrit
    American Thoracic Society International Conference 2014, San Diego; 05/2014
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    ABSTRACT: Body Correlations between UA Soft Tissue Structures and Pcrit
    American Thoracic Society International Conference 2014, San Diego; 05/2014
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    ABSTRACT: Obstructive sleep apnoea (OSA) is associated with cardiovascular disease. Dyslipidaemia has been implicated as a mechanism linking OSA with atherosclerosis, but no consistent associations with lipids exist for OSA or positive airway pressure treatment. We assessed the relationships between fasting lipid levels and obesity and OSA severity, and explored the impact of positive airway pressure treatment on 2-year fasting lipid level changes. Analyses included moderate-to-severe OSA patients from the Icelandic Sleep Apnoea Cohort. Fasting morning lipids were analysed in 613 untreated participants not on lipid-lowering medications at baseline. Patients were then initiated on positive airway pressure and followed for 2 years. Sub-classification using propensity score quintiles, which aimed to replicate covariate balance associated with randomised trials and, therefore, minimise selection bias and allow causal inference, was used to design the treatment group comparisons. 199 positive airway pressure adherent patients and 118 non-users were identified. At baseline, obesity was positively correlated with triglycerides and negatively correlated with total cholesterol, and low-density and high-density lipoprotein cholesterol. A small correlation was observed between the apnoea/hypopnoea index and high-density lipoprotein cholesterol. No effect of positive airway pressure adherence on 2-year fasting lipid changes was observed. Results do not support the concept of changes in fasting lipids as a primary mechanism for the increased risk of atherosclerotic cardiovascular disease in OSA.
    European Respiratory Journal 05/2014; · 7.13 Impact Factor
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    ABSTRACT: Rationale: The metabolic activity of the tongue is unknown in patients with sleep apnea. Tongue EMG activity has been shown to be increased in apneics. This increase in tongue EMG activity is thought to be related to increased neuromuscular compensation or denervation/reinnervation of the muscle fibers. Increased glucose uptake in the tongue would support increased neuromuscular compensation, whereas decreased glucose uptake in the tongue would support denervation/reinnervation of the muscle fibers. Objectives: To investigate the metabolic activity of the genioglossus and control upper airway muscles in obese apneics compared to obese controls. Methods: Subjects underwent a standard overnight sleep study to determine an apnea-hypopnea index (AHI); positron emission tomography with [18F]-2-fluoro-2-deoxy-D-glucose (FDG) and magnetic resonance imaging. We quantified glucose uptake by obtaining the standardized uptake value (SUV) within upper airway tissues. Main Results: We recruited 30 obese control subjects (AHI: 4.7±3.1 events/hour) and 72 obese apneics (AHI: 43.5±28.0 events/hour). Independent of age, BMI, gender and race, apneics had significantly reduced glucose uptake in the genioglossus (p=0.03) in comparison to controls. No differences in SUV were found in the masseter (p=0.38), pterygoid (p=0.70) or in neck (p=0.44) and submental (p=0.95) fat deposits between apneics and controls. Conclusions: There was significantly reduced glucose uptake in the genioglossus of apneics in comparison to obese controls. The reduction in glucose uptake was likely secondary to alterations in tongue muscle fiber type or to chronic denervation. The reduced glucose uptake argues against the neuromuscular compensation hypothesis explaining the increase in tongue EMG activity in apneics.
    American Journal of Respiratory and Critical Care Medicine 04/2014; · 11.04 Impact Factor
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    ABSTRACT: Accumulating evidence has shown that there is a genetic contribution to obstructive sleep apnea (OSA).The objectives were to use magnetic resonance imaging (MRI) cephalometry to (1) confirm heritability of craniofacial risk factors for OSA previously shown by cephalometrics; and (2) examine the heritability of new craniofacial structures that are measurable with MRI.
    Sleep 01/2014; 37(10). · 5.06 Impact Factor
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    ABSTRACT: The objective of this study was to determine whether tongue fat is increased in obese sleep apneics compared to obese subjects without sleep apnea. We hypothesized that excess fat is deposited in the tongue in obese patients with sleep apnea.
    Sleep 01/2014; 37(10). · 5.06 Impact Factor
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    ABSTRACT: (1) To determine whether facial phenotype, measured by quantitative photography, relates to underlying craniofacial obstructive sleep apnea (OSA) risk factors, measured with magnetic resonance imaging (MRI); (2) To assess whether these associations are independent of body size and obesity. Cross-sectional cohort. Landspitali, The National University Hospital, Iceland. One hundred forty patients (87.1% male) from the Icelandic Sleep Apnea Cohort who had both calibrated frontal and profile craniofacial photographs and upper airway MRI. Mean ± standard deviation age 56.1 ± 10.4 y, body mass index 33.5 ± 5.05 kg/m(2), with on-average severe OSA (apnea-hypopnea index 45.4 ± 19.7 h(-1)). N/A. Relationships between surface facial dimensions (photos) and facial bony dimensions and upper airway soft-tissue volumes (MRI) was assessed using canonical correlation analysis. Photo and MRI craniofacial datasets related in four significant canonical correlations, primarily driven by measurements of (1) maxillary-mandibular relationship (r = 0.8, P < 0.0001), (2) lower face height (r = 0.76, P < 0.0001), (3) mandibular length (r = 0.67, P < 0.0001), and (4) tongue volume (r = 0.52, P = 0.01). Correlations 1, 2, and 3 were unchanged when controlled for weight and neck and waist circumference. However, tongue volume was no longer significant, suggesting facial dimensions relate to tongue volume as a result of obesity. Significant associations were found between craniofacial variable sets from facial photography and MRI. This study confirms that facial photographic phenotype reflects underlying aspects of craniofacial skeletal abnormalities associated with OSA. Therefore, facial photographic phenotyping may be a useful tool to assess intermediate phenotypes for OSA, particularly in large-scale studies. Sutherland K, Schwab RJ, Maislin G, Lee RW, Benedikstdsottir B, Pack AI, Gislason T, Juliusson S, Cistulli PA. Facial phenotyping by quantitative photography reflects craniofacial morphology measured on magnetic resonance imaging in icelandic sleep apnea patients. SLEEP 2014;37(5):959-968.
    Sleep 01/2014; 37(5):959-968. · 5.06 Impact Factor
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    ABSTRACT: Obesity is the most important risk factor for obstructive sleep apnea (OSA), and the effects of obesity may be mediated by tongue fat. Our objective was to examine the effects of obesity on upper airway structures in obese (OBZ) and non-obese (NBZ) Zucker rats.
    Sleep 01/2014; 37(6):1095-102. · 5.06 Impact Factor
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    ABSTRACT: The objective of this study was to explore the mechanism of action of the oral pressure therapy (OPT) device, a new treatment for sleep apnea.
    Sleep 01/2014; 37(7):1237-47. · 5.06 Impact Factor
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    ABSTRACT: Symptoms of sleep-disordered breathing (SDB) are common among pregnant women, and several studies link SDB symptoms with gestational hypertension and preeclampsia. However, few prospective studies objectively measuring SDB during pregnancy have been performed. We performed a prospective cohort study examining risk factors for third trimester SDB in pregnant women. 105 pregnant women from the Hospital of the University of Pennsylvania obstetrics practices completed first and third trimester overnight polysomnography studies. We examined whether the number of SDB events per hour of sleep increased during pregnancy. We performed unadjusted and multivariable logistic regression analyses to estimate the effects of usual and pregnancy-specific characteristics on development of third trimester obstructive sleep apnoea (OSA). In secondary analyses, we examined the relationship between objectively measured SDB, hypertensive disorders of pregnancy, and other adverse maternal-fetal outcomes. Mean Apnoea-Hypopnoea Index increased from 2.07 (SD 3.01) events/h at baseline (first trimester) to 3.74 (SD 5.97) in the third trimester (p=0.009). 10.5% of women had OSA in the first trimester. By the third trimester, 26.7% of women had OSA. In multivariable analyses, first trimester body mass index (BMI) and maternal age were significantly associated with third trimester OSA. Third trimester OSA is common. Risk factors for third trimester OSA among women without baseline SDB include higher baseline BMI and maternal age.
    Thorax 11/2013; · 8.56 Impact Factor
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    ABSTRACT: ABSTRACT Objective: Reproductive hormone levels are associated with body size, and the association between estradiol (E2) and body size varies over the menopausal transition. This study aims to delineate these relationships using quantitative measures of visceral (Visc) and subcutaneous (SC) fat. Methods: Early follicular hormones (FSH, E2, LH, DHEAS, Testosterone) and T-1 weighted abdominal MRI images were obtained in a cross-sectional assessment of 77 women in the Penn Ovarian Aging Study. Fat volume (cm(3)) was quantified using validated software (Amira) and divided into tertiles of Visc and SC fat volume for analysis. Multivariable linear regression models compared hormone values between tertiles adjusting for race, age, and menopausal status. Results: In adjusted models, E2 was positively associated with Visc fat tertiles (geometric mean (GM) E2 pg/mL: Low 13.0, Mid 17.5, High 26.7, p=0.006) while FSH was inversely associated with Visc fat tertiles (GM FSH mIU/mL: Low 42.8, Mid 43.2 High 30.8, p=0.03). The association of E2 with Visc and SC fat tertiles varied by menopausal status (p<0.001). In the early transition, E2 was similar across tertiles of fat; postmenopause, E2 was positively associated with Visc fat. Other hormones were not associated with fat measures. Conclusions: Estradiol was associated with quantitative measures of visceral fat and varies by menopausal status. This finding suggests that visceral fat may be an important mediator in hormone changes over the menopausal transition.
    Climacteric 09/2013; · 2.24 Impact Factor
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    ABSTRACT: Background: Continuous positive airway pressure (CPAP) is considered the treatment of choice for obstructive sleep apnea (OSA), and studies have shown that there is a correlation between patient adherence and treatment outcomes. Newer CPAP machines can track adherence, hours of use, mask leak, and residual apnea-hypopnea index (AHI). Such data provide a strong platform to examine OSA outcomes in a chronic disease management model. However, there are no standards for capturing CPAP adherence data, scoring flow signals, or measuring mask leak, or for how clinicians should use these data. Methods: American Thoracic Society (ATS) committee members were invited, based on their expertise in OSA and CPAP monitoring. Their conclusions were based on both empirical evidence identified by a comprehensive literature review and clinical experience. Results: CPAP usage can be reliably determined from CPAP tracking systems, but the residual events (apnea/hypopnea) and leak data are not as easy to interpret as CPAP usage and the definitions of these parameters differ among CPAP manufacturers. Nonetheless, ends of the spectrum (very high or low values for residual events or mask leak) appear to be clinically meaningful. Conclusions: Providers need to understand how to interpret CPAP adherence tracking data. CPAP tracking systems are able to reliably track CPAP adherence. Nomenclature on the CPAP adherence tracking reports needs to be standardized between manufacturers and AHIFlow should be used to describe residual events. Studies should be performed examining the usefulness of the CPAP tracking systems and how these systems affect OSA outcomes.
    American Journal of Respiratory and Critical Care Medicine 09/2013; 188(5):613-20. · 11.04 Impact Factor
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    ABSTRACT: Background: Sleepiness may account for up to 20% of crashes on monotonous roads, especially highways. Obstructive sleep apnea (OSA) is the most common medical disorder that causes excessive daytime sleepiness, increasing the risk for drowsy driving two to three times. The purpose of these guidelines is to update the 1994 American Thoracic Society Statement that described the relationships among sleepiness, sleep apnea, and driving risk. Methods: A multidisciplinary panel was convened to develop evidence-based clinical practice guidelines for the management of sleepy driving due to OSA. Pragmatic systematic reviews were performed, and the Grading of Recommendations, Assessment, Development, and Evaluation approach was used to formulate and grade the recommendations. Critical outcomes included crash-related mortality and real crashes, whereas important outcomes included near-miss crashes and driving performance. Results: A strong recommendation was made for treatment of confirmed OSA with continuous positive airway pressure to reduce driving risk, rather than no treatment, which was supported by moderate-quality evidence. Weak recommendations were made for expeditious diagnostic evaluation and initiation of treatment and against the use of stimulant medications or empiric continuous positive airway pressure to reduce driving risk. The weak recommendations were supported by very low-quality evidence. Additional suggestions included routinely determining the driving risk, inquiring about additional causes of sleepiness, educating patients about the risks of excessive sleepiness, and encouraging clinicians to become familiar with relevant laws. Discussion: The recommendations presented in this guideline are based on the current evidence, and will require an update as new evidence and/or technologies becomes available.
    American Journal of Respiratory and Critical Care Medicine 06/2013; 187(11):1259-1266. · 11.04 Impact Factor
  • SLEEP 2013, Baltimore; 06/2013
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    ABSTRACT: BACKGROUND: Obesity and fat distribution patterns [subcutaneous vs. visceral adipose tissue (VAT)] are important predictors of future cardiometabolic risk. As accurate VAT measurement entails imaging, surrogate anthropometric measurements that would be cheaper and quicker to obtain would be highly desirable. Sagittal abdominal diameter (SAD) may be better than other VAT surrogate measures in adults, but the value of SAD to predict magnetic resonance imaging (MRI)-determined VAT in adolescents of different races, sexes, and pubertal stages has not been determined. AIM: To test the hypothesis that SAD correlates more strongly with volumetric VAT than other anthropometric measurements, independent of age, sex, race, and Tanner stage. SUBJECTS AND METHODS: Twenty-eight normal-weight and 44 obese adolescents underwent Tanner staging, anthropometric examinations, and abdominal MRI for volumetric partitioned fat calculation. RESULTS: VAT increased exponentially in the body mass index (BMI) > 97th percentile range. SAD, waist circumference (WC), BMI, and BMI Z-score correlated strongly with VAT (correlation coefficients of 0.85-0.86, all p-values < 0.0005); waist-hip ratio was less predictive of VAT (r = 0.68, p < 0.0005). On hierarchical regression, the strongest predictors of VAT in obese subjects were BMI Z-score and SAD (R(2) = 0.34 vs. 0.31, respectively, p < 0.0005); in normal-weight subjects, most anthropometric measures predicted VAT equally (R(2) = 0.16-0.18, p-values = 0.018-0.026). CONCLUSIONS: Unlike adults, in obese adolescents, SAD is not the strongest predictor of visceral adiposity. BMI Z-score is equivalently predictive and, together with BMI, provides sufficient information to assess visceral adiposity; more specialized anthropometric measurements (e.g., SAD and WC) do not add additional predictive value.
    Pediatric Diabetes 05/2013; · 2.13 Impact Factor
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    ABSTRACT: The obstructive sleep apnea syndrome (OSAS) is associated with increased visceral adipose tissue (VAT) in adults; however, few studies have evaluated VAT in relation to upper airway function in adolescents. We hypothesized that increased neck circumference (NC) and VAT would be associated with increased upper airway collapsibility. Adolescents (24 obese patients with OSAS, 22 obese control patients, and 29 lean control patients) underwent abdominal magnetic resonance imaging, and measurement of upper airway pressure-flow relationships in the activated and hypotonic upper airway states. Patients with OSAS had a greater activated slope of the pressure-flow relationship (SPF) than control groups (P < 0.001), whereas hypotonic SPF was greater in both obese groups compared with lean control patients (P = 0.01). NC and VAT were greater in obese control patients and those with OSAS than in lean control patients (P < 0.001), but did not differ between obese patients with OSAS and obese control patients. In lean control patients and those with OSAS, increased NC was associated with increased activated SPF, whereas in obese control patients it was associated with decreased activated SPF (P = 0.03). In contrast, increased NC was associated with increased hypotonic SPF in all groups (P < 0.001). There was no significant effect of VAT on either activated or hypotonic SPF for any of the three groups. Increased neck circumference was associated with increased upper airway collapsibility in adolescents in the hypotonic but not activated state. These data suggest that obese adolescents without OSAS, despite a narrowed upper airway from adipose tissue, are protected from developing OSAS by upper airway neuromotor activation. Neither neck circumference nor visceral adipose tissue is useful in predicting upper airway collapsibility in obese adolescents. Yuan H; Schwab RJ; Kim C; He J; Shults J; Bradford R; Huang J; Marcus CL. Relationship between body fat distribution and upper airway dynamic function during sleep in adolescents. SLEEP 2013;36(8):1199-1207.
    Sleep 01/2013; 36(8):1199-207. · 5.06 Impact Factor

Publication Stats

2k Citations
380.98 Total Impact Points


  • 2014
    • Southwestern PA Pulmonary & Sleep Medicine Ltd.
      Washington, Pennsylvania, United States
  • 1996–2014
    • Hospital of the University of Pennsylvania
      • • Department of Medicine
      • • Division of Pulmonary Allergy and Critical Care
      Philadelphia, Pennsylvania, United States
  • 1993–2014
    • University of Pennsylvania
      • • Center for Sleep and Circadian Neurobiology
      • • Department of Medicine
      • • Division of Gastrointestinal Surgery
      • • Division of Pulmonary, Allergy and Critical Care
      • • Division of Sleep Medicine
      • • Department of Radiology
      Philadelphia, Pennsylvania, United States
  • 2012
    • National University Hospital of Iceland
      Reikiavik, Capital Region, Iceland
  • 2010–2011
    • Royal North Shore Hospital
      Sydney, New South Wales, Australia
  • 2006
    • Brigham and Women's Hospital
      • Division of Pulmonary and Critical Care Medicine
      Boston, MA, United States
  • 2001–2002
    • The Children's Hospital of Philadelphia
      • Division of Pulmonary Medicine
      Philadelphia, PA, United States