Simple Cause for a “Complex” Problem To the Editor: We read with great interest the recent CHEST article (February 2014) by DelRosso et al1 on complex sleep apnea syndrome (CompSAS). CompSAS is a relatively new terminology used to describe the appearance of central sleep apnea (CSA) in patients with OSA in whom airway patency has been restored with CPAP therapy. We agree with the authors that patients with CompSAS have both reduced upper airway tone and unstable central ventilatory control. However, central apnea also occurs when the patient’s ventilatory effort ceases due to several other possible reasons, including high loop gain (exaggerated hyperventilatory response to hypercarbia resulting in hypocapnea below the apnea threshold), low arousal threshold, or apnea threshold close to awake Pco2.2 Recently, in a study by Montesi et al3 regarding 310 patients with OSA who underwent either split-night or full-night CPAP titration, air leak during CPAP titration was associated with the development of acute CSA, particularly in subjects using a nasal mask. The authors postulated that air leak washing out anatomic dead space is a contributing factor in the development of CompSAS. The group with central apnea index , 5 had a median average leak of 45.5 L/min (interquartile range, 20.8 L/min) vs 51.0 L/min (interquartile range, 21.0 L/min) with central apnea index ⱖ 5 (P 5 .056). These findings might have mechanistic and therapeutic implications as the physicians involved in the management of CompSAS should be aware of this potential iatrogenic and avoidable cause of the emergence of CSA during CPAP titration. The finding of a reemergence of apneas on increasing CPAP should alert the astute physician to conduct a diligent search for air leak in the appropriate clinical setting. Lastly, although the best treatment of CompSAS remains controversial, most of the published data suggest that this form of central apnea resolves with ongoing CPAP therapy.4 Studies have also documented that adaptive servoventilation is more effective in patients with persistent central apneas.4,5 Sachin Kumar, MD, DM, FCCP Sandipan Chandra, MD New Delhi, India Affiliations: From the Department of Pulmonary Medicine, Institute of Liver & Biliary Sciences. Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article. Correspondence to: Sachin Kumar, MD, DM, FCCP, Department of Pulmonary Medicine, Institute of Liver & Biliary Sciences, C-15, Delhi Government Residential Complex, D-2 Pocket, Vasant Kunj, New Delhi, 110070, India; e-mail: [email protected] © 2014 American College of Chest Physicians. Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details. DOI: 10.1378/chest.14-0312
References 1. DelRosso LM, Harper MB, Hoque R. A man in his 50s develops 3-min central apneas during a titration study. Chest. 2014; 145(2):404-406. 2. Salloum A, Rowley JA, Mateika JH, Chowdhuri S, Omran Q, Badr MS. Increased propensity for central apnea in patients with obstructive sleep apnea: effect of nasal continuous posijournal.publications.chestnet.org
tive airway pressure. Am J Respir Crit Care Med. 2010;181(2): 189-193. 3. Montesi SB, Bakker JP, Macdonald M, et al. Air leak during CPAP titration as a risk factor for central apnea. J Clin Sleep Med. 2013;9(11):1187-1191. 4. Kuzniar TJ, Pusalavidyasagar S, Gay PC, Morgenthaler TI. Natural course of complex sleep apnea—a retrospective study. Sleep Breath. 2008;12(2):135-139. 5. Kuźniar TJ, Morgenthaler TI. Treatment of complex sleep apnea syndrome. Chest. 2012;142(4):1049-1057.
Response To the Editor: We thank Drs Kumar and Chandra for their interest in our article1 and comments regarding other postulated pathophysiologic mechanisms for complex sleep apnea syndrome. Our article illustrates the emergence of central apneas during positive airway pressure titration in a patient without any past medical history.1 This case presentation is not intended to be a complete review of the literature. As stated in the International Classification of Sleep Disorders, Third Edition, despite many postulated mechanisms, there are no definitive data regarding either the cause of treatmentemergent central sleep apnea or the optimal management strategy for these patients.2 Lourdes M. DelRosso, MD Romy Hoque, MD Shreveport, LA Affiliations: From the Division of Sleep Medicine and Department of Neurology, Louisiana State University School of Medicine. Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article. Correspondence to: Lourdes M. DelRosso, MD, Division of Sleep Medicine and Department of Neurology, Louisiana State University School of Medicine, Shreveport, LA 71130; e-mail: [email protected] © 2014 American College of Chest Physicians. Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details. DOI: 10.1378/chest.14-0604
References 1. DelRosso LM, Harper MB, Hoque R. A man in his 50s develops 3-min central apneas during a titration study. Chest. 2014;145(2):404-406. 2. American Academy of Sleep Medicine. International Classification of Sleep Disorders. 3rd ed. Darien, IL: American Academy of Sleep Medicine; 2014.
GI Symptoms in Patients With COPD To the Editor: In a recent issue of CHEST (February 2014),1 disturbed integrity of the GI system was reported in patients with COPD, implying that the GI system is affected and contributes to the systemic manifestations of COPD. These findings were detected in a wellcharacterized sample of 14 patients and compared with a matched CHEST / 145 / 6 / JUNE 2014
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Figure 1. Frequency of reported GI symptoms in patients with COPD. Early satiety, abdominal bloating, and flatulence were the most reported symptoms. Most symptoms were reported more often in women than in men: *P , .05; **P , .01 vs women.
control group. Hence, the question arises as to whether GI complaints are often present in the COPD population. To investigate a potential impact of the GI compartment on the systemic manifestation of COPD, we performed a retrospective analysis of 1,228 patients with COPD (58% men; mean ⫾ SD for age, 65 ⫾ 10 years; and lung function: FEV1, 45% ⫾ 18% predicted; FEV1/FVC, 40% ⫾ 12%) entering routine initial assessment in a pulmonary rehabilitation program in the Centre of expertise for chronic organ failure, Horn, The Netherlands. Food-related symptoms over the last weeks before admission were assessed by a dietician using a standardized checklist (eight GI symptoms; possible answers were “no,” “sometimes,” or “yes”). The database consisted of deidentified and preexisting data and is, therefore, institutional review board exempt. The results of this analysis revealed that only 15% of the patients reported no GI symptoms. The remaining patients (85%) reported one (28%), two (28%), three (23%), four (11%), five (6%), or more (4%) symptoms. Early satiety and abdominal bloating were the most often documented, significantly more often in women than in men (x2 test) (Fig 1). Reflux was reported in about 20% of the population, in-line with the percentage reported previously in patients with COPD.2 In that article, reports on gastroesophageal reflux were significantly lower in subjects with normal lung function. The current data analysis does not present data from healthy subjects, and, therefore, it cannot be concluded that patients with COPD report more GI symptoms than do healthy elderly people. However, a recent report showed that asthma/COPD was independently associated with the presence of GI symptoms.3 The prevalence of GI symptoms in the total cohort of . 16,000 subjects was 26%, whereas it was 85% in our COPD cohort, indicating that the reports of GI symptoms may be higher in patients with COPD. Insight into the GI complaints in COPD is relevant because it can contribute to lower appetite and less intestinal malabsorption. To conclude, the majority of patients with COPD report at least one GI symptom. Together with a recent case-control study that showed increased GI permeability in patients with COPD, these data imply that the contribution of the GI compartment to the systemic manifestation of COPD calls for further investigation.
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Erica P. A. Rutten, PhD Martijn A. Spruit, PhD Frits M. E. Franssen, MD, PhD Wim A. Buurman, PhD Emiel F. M. Wouters, MD, PhD, FCCP Horn, The Netherlands Kaatje Lenaerts, PhD Maastricht, The Netherlands Affiliations: From the Program Development Centre (Drs Rutten, Spruit, Franssen, Buurman, and Wouters), Centre of expertise for chronic organ failure; and the Department of Surgery (Dr Lenaerts), and Department of Respiratory Medicine (Dr Wouters), NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre. Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article. Correspondence to: Erica P. A. Rutten, PhD, Centre of expertise for chronic organ failure, Hornerheide 1, 6085 NM, Horn, The Netherlands; e-mail: [email protected] © 2014 American College of Chest Physicians. Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details. DOI: 10.1378/chest.14-0285
References 1. Rutten EPA, Lenaerts K, Buurman WA, Wouters EFM. Disturbed intestinal integrity in patients with COPD: effects of activities of daily living. Chest. 2014;145(2):245-252. 2. Lindberg A, Larsson LG, Rönmark E, Lundbäck B. Co-morbidity in mild-to-moderate COPD: comparison to normal and restrictive lung function. COPD. 2011;8(6):421-428. 3. Tielemans MM, Jaspers Focks J, van Rossum LG, et al. Gastrointestinal symptoms are still prevalent and negatively impact health-related quality of life: a large cross-sectional population based study in The Netherlands. PLoS ONE. 2013; 8(7):e69876.
Correspondence
References 1. DelRosso LM, Harper MB, Hoque R. A man in his 50s develops 3-min central apneas during a titration study. Chest. 2014; 145(2):404-406. 2. Salloum A, Rowley JA, Mateika JH, Chowdhuri S, Omran Q, Badr MS. Increased propensity for central apnea in patients with obstructive sleep apnea: effect of nasal continuous posijournal.publications.chestnet.org
tive airway pressure. Am J Respir Crit Care Med. 2010;181(2): 189-193. 3. Montesi SB, Bakker JP, Macdonald M, et al. Air leak during CPAP titration as a risk factor for central apnea. J Clin Sleep Med. 2013;9(11):1187-1191. 4. Kuzniar TJ, Pusalavidyasagar S, Gay PC, Morgenthaler TI. Natural course of complex sleep apnea—a retrospective study. Sleep Breath. 2008;12(2):135-139. 5. Kuźniar TJ, Morgenthaler TI. Treatment of complex sleep apnea syndrome. Chest. 2012;142(4):1049-1057.
Response To the Editor: We thank Drs Kumar and Chandra for their interest in our article1 and comments regarding other postulated pathophysiologic mechanisms for complex sleep apnea syndrome. Our article illustrates the emergence of central apneas during positive airway pressure titration in a patient without any past medical history.1 This case presentation is not intended to be a complete review of the literature. As stated in the International Classification of Sleep Disorders, Third Edition, despite many postulated mechanisms, there are no definitive data regarding either the cause of treatmentemergent central sleep apnea or the optimal management strategy for these patients.2 Lourdes M. DelRosso, MD Romy Hoque, MD Shreveport, LA Affiliations: From the Division of Sleep Medicine and Department of Neurology, Louisiana State University School of Medicine. Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article. Correspondence to: Lourdes M. DelRosso, MD, Division of Sleep Medicine and Department of Neurology, Louisiana State University School of Medicine, Shreveport, LA 71130; e-mail: [email protected] © 2014 American College of Chest Physicians. Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details. DOI: 10.1378/chest.14-0604
References 1. DelRosso LM, Harper MB, Hoque R. A man in his 50s develops 3-min central apneas during a titration study. Chest. 2014;145(2):404-406. 2. American Academy of Sleep Medicine. International Classification of Sleep Disorders. 3rd ed. Darien, IL: American Academy of Sleep Medicine; 2014.
GI Symptoms in Patients With COPD To the Editor: In a recent issue of CHEST (February 2014),1 disturbed integrity of the GI system was reported in patients with COPD, implying that the GI system is affected and contributes to the systemic manifestations of COPD. These findings were detected in a wellcharacterized sample of 14 patients and compared with a matched CHEST / 145 / 6 / JUNE 2014
1437
Figure 1. Frequency of reported GI symptoms in patients with COPD. Early satiety, abdominal bloating, and flatulence were the most reported symptoms. Most symptoms were reported more often in women than in men: *P , .05; **P , .01 vs women.
control group. Hence, the question arises as to whether GI complaints are often present in the COPD population. To investigate a potential impact of the GI compartment on the systemic manifestation of COPD, we performed a retrospective analysis of 1,228 patients with COPD (58% men; mean ⫾ SD for age, 65 ⫾ 10 years; and lung function: FEV1, 45% ⫾ 18% predicted; FEV1/FVC, 40% ⫾ 12%) entering routine initial assessment in a pulmonary rehabilitation program in the Centre of expertise for chronic organ failure, Horn, The Netherlands. Food-related symptoms over the last weeks before admission were assessed by a dietician using a standardized checklist (eight GI symptoms; possible answers were “no,” “sometimes,” or “yes”). The database consisted of deidentified and preexisting data and is, therefore, institutional review board exempt. The results of this analysis revealed that only 15% of the patients reported no GI symptoms. The remaining patients (85%) reported one (28%), two (28%), three (23%), four (11%), five (6%), or more (4%) symptoms. Early satiety and abdominal bloating were the most often documented, significantly more often in women than in men (x2 test) (Fig 1). Reflux was reported in about 20% of the population, in-line with the percentage reported previously in patients with COPD.2 In that article, reports on gastroesophageal reflux were significantly lower in subjects with normal lung function. The current data analysis does not present data from healthy subjects, and, therefore, it cannot be concluded that patients with COPD report more GI symptoms than do healthy elderly people. However, a recent report showed that asthma/COPD was independently associated with the presence of GI symptoms.3 The prevalence of GI symptoms in the total cohort of . 16,000 subjects was 26%, whereas it was 85% in our COPD cohort, indicating that the reports of GI symptoms may be higher in patients with COPD. Insight into the GI complaints in COPD is relevant because it can contribute to lower appetite and less intestinal malabsorption. To conclude, the majority of patients with COPD report at least one GI symptom. Together with a recent case-control study that showed increased GI permeability in patients with COPD, these data imply that the contribution of the GI compartment to the systemic manifestation of COPD calls for further investigation.
1438
Erica P. A. Rutten, PhD Martijn A. Spruit, PhD Frits M. E. Franssen, MD, PhD Wim A. Buurman, PhD Emiel F. M. Wouters, MD, PhD, FCCP Horn, The Netherlands Kaatje Lenaerts, PhD Maastricht, The Netherlands Affiliations: From the Program Development Centre (Drs Rutten, Spruit, Franssen, Buurman, and Wouters), Centre of expertise for chronic organ failure; and the Department of Surgery (Dr Lenaerts), and Department of Respiratory Medicine (Dr Wouters), NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre. Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article. Correspondence to: Erica P. A. Rutten, PhD, Centre of expertise for chronic organ failure, Hornerheide 1, 6085 NM, Horn, The Netherlands; e-mail: [email protected] © 2014 American College of Chest Physicians. Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details. DOI: 10.1378/chest.14-0285
References 1. Rutten EPA, Lenaerts K, Buurman WA, Wouters EFM. Disturbed intestinal integrity in patients with COPD: effects of activities of daily living. Chest. 2014;145(2):245-252. 2. Lindberg A, Larsson LG, Rönmark E, Lundbäck B. Co-morbidity in mild-to-moderate COPD: comparison to normal and restrictive lung function. COPD. 2011;8(6):421-428. 3. Tielemans MM, Jaspers Focks J, van Rossum LG, et al. Gastrointestinal symptoms are still prevalent and negatively impact health-related quality of life: a large cross-sectional population based study in The Netherlands. PLoS ONE. 2013; 8(7):e69876.
Correspondence
