34 Copyright © 2022 Korean Sleep Research Society A Successful Treatment of Obesity Hypoventilation Syndrome Using Bi-level Positive Airway Pressure in a Patient With Hypoxic Brain Damage Yooha Hong, Han Beet Kim, Min Jun Song, Heejung Mo, Hee-Jin Im Department of Neurology, Dongtan Sacred Heart Hospital, Hallym University Medical Center, Hwaseong, Korea Received December 20, 2021 Revised January 25, 2022 Accepted March 14, 2022 Address for correspondence Hee-Jin Im, MD, PhD Department of Neurology, Dongtan Sacred Heart Hospital, Hallym University Medical Center, 7 Keunjaebong-gil, Hwaseong 18450, Korea Tel: +82-31-8086-3185 Fax: +82-31-8086-2317 E-mail: [email protected] We present the case of a 78-year-old female who experienced acute mental deterioration aſter vomiting. She showed severe hypercapnia without definite lung disease and hypoxic injury on brain image. Aſter the acute period, she still had excessive daytime sleepiness, and the hypercapnia aggravated during the night. Poly- somnography revealed severe obstructive sleep apnea, a sleep-related breathing disorder with a high apnea- hypopnea index of 60.2/h (mainly a hypopnea index of 59.0/h). She was diagnosed with combined obesity hypoventilation syndrome (OHS) and sleep-related breathing disorder, as the cause of daytime hypercapnia and excessive daytime sleepiness. Three months of successful bi-level positive airway pressure (BiPAP) therapy dramatically improved her daytime sleepiness and cognition. is case suggests that patients with OHS can be susceptible to hypoxic brain damage, and emphasizes the importance of the recognition and diagnosis of OHS and appropriate treatment with BiPAP therapy. J Sleep Med 2022;19(1):34-37 Keywords: Obesity hypoventilation syndrome; Bilevel positive airway pressure; Hypoxic brain damage. INTRODUCTION Obesity hypoventilation syndrome (OHS) is a sleep-relat- ed hypoventilation disorder defined as the presence of obesity (body mass index >30 kg/m 2 ) with chronic daytime hypercap- nia (PaCO2 ≥45 mm Hg) in patients without any other causes to explain alveolar hypoventilation. 1,2 e diagnosis of OHS is important, given the clinical aggravation leading to respiratory dysfunction along with the mortality rate in underdiagnosed patients. 3 Also, OHS has been rising and is now a relatively common cause of chronic respiratory failure with hypercapnia, as obesity rates continue to increase. erefore, an accurate di- agnosis and therapeutic approach for OHS are necessary. We report a case of hypoxic brain damage in a patient with OHS who was treated with bi-level positive airway pressure (BiPAP) therapy. CASE REPORT An obese 78-year-old female was admitted to the neurologi- cal department because of acute mental deterioration. A nurs- ing assistant checked whether she had slept the night before and found that she was lying in bed, with vomiting and uncon- sciousness, the following morning. She had a history of hyper- tension, diabetes, and mild cognitive impairment. She could barely walk and was assisted by a walker as she was both over- weight and aging. ere was no history of infection or intesti- nal disease. She had no respiratory problems, had never smoked, and usually did not suffer any related symptoms, such as dys- pnea. Physical examination revealed a height of 160 cm, weighed of 81.0 kg, and body mass index of 31.6 kg/m 2 , indicating obe- sity. On neurological examination at arrival in the emergency department using an oxygen mask with 15 L/min flow, her consciousness level was a semi-coma status, with a Glasgow Coma Scale (E2, M4, V1) of 7. Furthermore, her brain stem re- flexes were normal without other neurological deficits. e ini- tial arterial blood gas test under oxygenation showed severe respiratory acidosis and hypercapnia (pH 7.111, HCO3 38.8 mEq/L, PaCO2 120.5 mm Hg, PaO2 130.6 mm Hg, and SaO2 97.1%), and airway intubation and mechanical ventilation were performed. ere were no specific findings in the blood tests performed (including ammonia, infection marker, glu- cose, and thyroid hormone levels) to differentiate the various CASE REPORT pISSN 2384-2423 / eISSN 2384-2431 is is an Open Access article distributed under the terms of the Creative Com- mons Attribution Non-Commercial License (https://creativecommons.org/licens- es/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. J Sleep Med 2022;19(1):34-37 https://doi.org/10.13078/jsm.210027
A Successful Treatment of Obesity Hypoventilation Syndrome Using Bi-level Positive Airway Pressure in a Patient With Hypoxic Brain Damage
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A Successful Treatment of Obesity Hypoventilation Syndrome Using Bi-level Positive Airway Pressure in a Patient With Hypoxic Brain Damage
Yooha Hong, Han Beet Kim, Min Jun Song, Heejung Mo, Hee-Jin Im Department of Neurology, Dongtan Sacred Heart Hospital, Hallym University Medical Center, Hwaseong, Korea
Received December 20, 2021 Revised January 25, 2022 Accepted March 14, 2022
Address for correspondence Hee-Jin Im, MD, PhD Department of Neurology, Dongtan Sacred Heart Hospital, Hallym University Medical Center, 7 Keunjaebong-gil, Hwaseong 18450, Korea Tel: +82-31-8086-3185 Fax: +82-31-8086-2317 E-mail: [email protected]
We present the case of a 78-year-old female who experienced acute mental deterioration after vomiting. She showed severe hypercapnia without definite lung disease and hypoxic injury on brain image. After the acute period, she still had excessive daytime sleepiness, and the hypercapnia aggravated during the night. Poly- somnography revealed severe obstructive sleep apnea, a sleep-related breathing disorder with a high apnea- hypopnea index of 60.2/h (mainly a hypopnea index of 59.0/h). She was diagnosed with combined obesity hypoventilation syndrome (OHS) and sleep-related breathing disorder, as the cause of daytime hypercapnia and excessive daytime sleepiness. Three months of successful bi-level positive airway pressure (BiPAP) therapy dramatically improved her daytime sleepiness and cognition. This case suggests that patients with OHS can be susceptible to hypoxic brain damage, and emphasizes the importance of the recognition and diagnosis of OHS and appropriate treatment with BiPAP therapy. J Sleep Med 2022;19(1):34-37
Keywords: Obesity hypoventilation syndrome; Bilevel positive airway pressure; Hypoxic brain damage.
INTRODUCTION
Obesity hypoventilation syndrome (OHS) is a sleep-relat- ed hypoventilation disorder defined as the presence of obesity (body mass index >30 kg/m2) with chronic daytime hypercap- nia (PaCO2 ≥45 mm Hg) in patients without any other causes to explain alveolar hypoventilation.1,2 The diagnosis of OHS is important, given the clinical aggravation leading to respiratory dysfunction along with the mortality rate in underdiagnosed patients.3 Also, OHS has been rising and is now a relatively common cause of chronic respiratory failure with hypercapnia, as obesity rates continue to increase. Therefore, an accurate di- agnosis and therapeutic approach for OHS are necessary. We report a case of hypoxic brain damage in a patient with OHS who was treated with bi-level positive airway pressure (BiPAP) therapy.
CASE REPORT
An obese 78-year-old female was admitted to the neurologi-
cal department because of acute mental deterioration. A nurs- ing assistant checked whether she had slept the night before and found that she was lying in bed, with vomiting and uncon- sciousness, the following morning. She had a history of hyper- tension, diabetes, and mild cognitive impairment. She could barely walk and was assisted by a walker as she was both over- weight and aging. There was no history of infection or intesti- nal disease. She had no respiratory problems, had never smoked, and usually did not suffer any related symptoms, such as dys- pnea. Physical examination revealed a height of 160 cm, weighed of 81.0 kg, and body mass index of 31.6 kg/m2, indicating obe- sity. On neurological examination at arrival in the emergency department using an oxygen mask with 15 L/min flow, her consciousness level was a semi-coma status, with a Glasgow Coma Scale (E2, M4, V1) of 7. Furthermore, her brain stem re- flexes were normal without other neurological deficits. The ini- tial arterial blood gas test under oxygenation showed severe respiratory acidosis and hypercapnia (pH 7.111, HCO3 38.8 mEq/L, PaCO2 120.5 mm Hg, PaO2 130.6 mm Hg, and SaO2 97.1%), and airway intubation and mechanical ventilation were performed. There were no specific findings in the blood tests performed (including ammonia, infection marker, glu- cose, and thyroid hormone levels) to differentiate the various
CASE REPORT pISSN 2384-2423 / eISSN 2384-2431
This is an Open Access article distributed under the terms of the Creative Com- mons Attribution Non-Commercial License (https://creativecommons.org/licens- es/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
J Sleep Med 2022;19(1):34-37 https://doi.org/10.13078/jsm.210027
encephalopathies. Following mechanical ventilation, her hypercapnia im-
proved within three hours of arrival at the hospital, and her mental state recovered within five hours. Diffusion-weighted brain magnetic resonance imaging (MRI) performed on the fifth day after admission showed acute restricted lesions in the bilateral basal ganglia, indicating hypoxic brain damage (Fig. 1). Although the patient was clearly alert, a mechanical ventilator was applied for 12 days, because CO2 retention was not adequately resolved. There was no evidence of aspiration pneumonia on initial chest computed tomography (CT) with contrast, but prophylactic antibiotics were administered for 12 days, during ventilator application. The results of the arterial blood gas test after the ventilator removal still showed mild re- spiratory acidosis (a pH of 7.389, HCO3 29.9 mEq/L, PaCO2 49.2 mm Hg, PaO2 75.0 mm Hg, and SaO2 94.5%).
In the other exploration of respiratory failure, there were no anatomical explanations for hypoventilation or findings suggestive of heart failure, pulmonary hypertension, and pul- monary thromboembolism through various tests, such as echo- cardiography, pulmonary thromboembolism-CT, and bron- choscopy. However, the patient still showed hypercapnia upon waking in the morning (peak PaCO2 56.3 mm Hg), and this value was higher than that in her awakened state during the daytime (peak PaCO2 48 mm Hg). A pulmonary function test was performed two days after the removal of mechanical ven- tilation in a patient-cooperative state and showed a severe re-
strictive pattern: the forced expiratory volume in one second/ forced vital capacity ratio (80%) was greater than normal, and the forced vital capacity (37%) was low, but there were no clear pulmonary diseases, such as chronic obstructive pulmonary disease (COPD) or asthma. Despite preserving her alertness, the patient showed excessive daytime sleepiness and snoring. She was usually very sleepy during the day and fell asleep while speaking. Cognitive impairment was confirmed through a mini-mental state examination score of nine. We suspected not only sleep breathing disorder, but also OHS as her diagno- sis based on findings of hypercapnia, particularly during ear- ly morning and nighttime, along with a history of obesity. On day 19 following admission, a split-night polysomnography (PSG) study was performed. The PSG revealed severe obstruc- tive sleep apnea (OSA), with a high apnea-hypopnea index (AHI) of 60.2/h (mainly a hypopnea index of 59.0/h). The PSG (Fig. 2) also showed sleep-aggravated hypercapnia and noctur- nal hypoxemia during rapid eye movement sleep, with hypop- nea events. In addition, the maximum end-tidal carbon diox- ide values were 51 mm Hg during awakening and 61 mm Hg during sleep. The continuous positive airway pressure (CPAP) was adjusted by increasing the pressure from 4 to 15 cm H2O, but hypoventilation and hypercapnia still occurred, leading to BiPAP titration, even during limited night hours. During titra- tion, the optimal BiPAP pressure was determined, with an in- creased inspiratory pressure of 18 cm H2O and expiratory pres- sure of 12 cm H2O at a nadir AHI of 2/h. After three months of
Figure 1. Diffusion-weighted magnetic resonance imaging of brain shows high signal intensity on bilateral basal ganglia (white arrows) but low signal intensity on apparent diffusion coefficient map.
36
OHS and BiPAP
BiPAP use, the arterial CO2 retention in the morning was low- ered, from 55.4 mm Hg to 38 mm Hg, and the residual AHI was 4.1/h. She adhered to BiPAP therapy for an average of 7 hours and 17 minutes, with 99% usage during the prescribed days. The patient is being followed-up on an outpatient basis, with no clinical signs of dyspnea, edema, nor neurological symp- toms, including daytime sleepiness and cognitive impairment. Her family members subjectively believe that communication with the patient is smoother than before, and her cognitive de- cline improved, despite the lack of objective cognition or sleepi- ness measures. In summary, we report a case of OHS combined with OSA that presented with acute exacerbation of chronic respiratory failure and hypoxic brain damage. Furthermore, the patient’s condition improved after the BiPAP treatment. The patient provided written informed consent.
DISCUSSION
OHS is characterized by obesity and daytime hypercapnia that occurs in the absence of an explanation for hypoventila- tion.4 Previous studies have shown significant health impair- ments in these patients. They often endure prolonged periods of hospitalization and draw heavily on healthcare resources, with worsening comorbidities and high mortality.3-5
Patients with OHS suffer from OSA and exhibit severe and prolonged oxygen desaturation during sleep, which results from reduced lung volumes and increased airway resistance.6 Therefore, hypoxia in OHS is sustained, and notably worsens during sleep.
Prior studies have reported that patients with chronic respi- ratory insufficiency, such as COPD, are susceptible to hypoxic brain damage and cognitive dysfunction, including increased
inflammation and oxidative and physiological stress.7 Con- genital central hypoventilation syndrome is a disorder that af- fects hypoventilation during sleep, resulting in a shortage of oxygen and a buildup of carbon dioxide in the blood. This po- tentially leads to absent or reduced ventilatory and arousal re- sponses to sustained hypercapnia and, to a lesser extent, sus- tained hypoxia.8 Some studies have revealed that several brain regions in patients with congenital central hypoventilation syn- drome respond inappropriately to problems with ventilation or blood pressure. In prior study results, the brain lesions typ- ically appeared in the forebrain diencephalon, midbrain, and cerebellar areas.9 MRI findings of hypoxic brain damage pref- erentially indicate lesions in areas such as the cerebellar hemi- spheres, basal ganglia, or cerebral cortex.10 The patient in our presenting case exhibited hypoxia by asphyxiation from vom- iting, following accelerated aggravated hypercapnia on OHS. Given the clinical history and circumstances of the present case, hypoxic injury may be a convincing explanation for the patho- physiology of brain injury in the patient rather than other in- fectious, vascular, epileptic, genetic/congenital, metabolic, or toxic causes.
Chronic hypoventilation in patients with OHS exposes them to chronic hypoxia and daytime hypercapnia, which leads to an accumulated hypoxic burden and susceptibility to even mini- mal levels of hypoxic insult. OHS often remains underdiagnosed in clinical practice and presents with a lack of specific symp- toms or tools, such as in-lab PSG and carbon dioxide measure- ment.1 It is important for clinicians to be aware of and suspect the possibility of OHS, given that early detection and proper management are critical for improving patient quality of life and even averting mortality. Therefore, physicians must con- sider early ventilatory management to provide neuroprotec-
Figure 2. Polysomnography shows hypopnea (yellow squares), desaturation (pink squares), and hypercapnia (EtCO2 >40 mm Hg) during REM sleep.
Hong Y et al.
https://www.e-jsm.org 37
tion against delayed hypoxic brain damage during the acute phase in patients with OHS who have experienced a hypoxic event, and even in those without definite respiratory failure.
Patients with OHS combined with severe OSA should be treated with CPAP or BiPAP to manage sleep-disordered breath- ing and improve nocturnal gas exchange.6 However, high CPAP was insufficient for resolving the hypercapnia and hypopnea in this patient. Therefore, we adjusted the BiPAP to provide pres- sure support and improve hypoventilation. This case study sug- gests that patients with OHS may be susceptible to anoxic dam- age. Notably, we would like to highlight the importance of concerns surrounding OHS in obese patients and introduce successful treatment with non-invasive ventilation in order to prevent chronic respiratory failure.
Conflicts of Interest The authors have no potential conflicts of interest to disclose.
ORCID iDs Yooha Hong https://orcid.org/0000-0002-8693-2831 Han Beet Kim https://orcid.org/0000-0003-1806-7687 Min Jun Song https://orcid.org/0000-0001-7416-9149 Heejung Mo https://orcid.org/0000-0001-7810-035X Hee-Jin Im https://orcid.org/0000-0002-8979-6521
Author Contributions Conceptualization: Hee-Jin Im. Data curation: Han Beet Kim, Min Jun
Song, Heejung Mo. Formal analysis: Yooha Hong. Investigation: Yooha Hong, Heejung Mo. Methodology: Yooha Hong, Hee-Jin Im. Project ad- ministration: Hee-Jin Im. Supervision: Hee-Jin Im. Visualization: Yooha Hong. Writing—original draft: Yooha Hong. Writing—review & editing: Hee-Jin Im.
Funding Statement None
1. Masa JF, Pépin JL, Borel JC, Mokhlesi B, Murphy PB, Sánchez-Quiroga MÁ. Obesity hypoventilation syndrome. Eur Respir Rev 2019;28:180097. https://doi.org/10.1183/16000617.0097-2018.
2. Iftikhar IH, Roland J. Obesity hypoventilation syndrome. Clin Chest Med 2018;39:427-436. https://doi.org/10.1016/j.ccm.2018.01.006.
3. Mokhlesi B, Tulaimat A, Faibussowitsch I, Wang Y, Evans AT. Obesity hypoventilation syndrome: prevalence and predictors in patients with obstructive sleep apnea. Sleep Breath 2007;11:117-124. https://doi. org/10.1007/s11325-006-0092-8.
4. Lévy P, Pépin JL, Arnaud C, et al. Intermittent hypoxia and sleep-dis- ordered breathing: current concepts and perspectives. Eur Respir J 2008;32:1082-1095. https://doi.org/10.1183/09031936.00013308.
5. Mokhlesi B, Kryger MH, Grunstein RR. Assessment and management of patients with obesity hypoventilation syndrome. Proc Am Thorac Soc 2008;5:218-225. https://doi.org/10.1513/pats.200708-122MG.
6. Piper AJ, Grunstein RR. Obesity hypoventilation syndrome: mecha- nisms and management. Am J Respir Crit Care Med 2011;183:292-298. https://doi.org/10.1164/rccm.201008-1280CI.
7. Higbee DH, Dodd JW. Cognitive impairment in COPD: an often overlooked co-morbidity. Expert Rev Respir Med 2021;15:9-11. https:// doi.org/10.1080/17476348.2020.1811090.
8. Ramanantsoa N, Gallego J. Congenital central hypoventilation syndrome. Respir Physiol Neurobiol 2013;189:272-279. https://doi.org/10.1016/j. resp.2013.05.018.
9. Kumar R, Macey PM, Woo MA, Alger JR, Keens TG, Harper RM. Neu- roanatomic deficits in congenital central hypoventilation syndrome. J Comp Neurol 2005;487:361-371. https://doi.org/10.1002/cne.20565.
10. Huang BY, Castillo M. Hypoxic-ischemic brain injury: imaging find- ings from birth to adulthood. Radiographics 2008;28:417-439. https:// doi.org/10.1148/rg.282075066.
Yooha Hong, Han Beet Kim, Min Jun Song, Heejung Mo, Hee-Jin Im Department of Neurology, Dongtan Sacred Heart Hospital, Hallym University Medical Center, Hwaseong, Korea
Received December 20, 2021 Revised January 25, 2022 Accepted March 14, 2022
Address for correspondence Hee-Jin Im, MD, PhD Department of Neurology, Dongtan Sacred Heart Hospital, Hallym University Medical Center, 7 Keunjaebong-gil, Hwaseong 18450, Korea Tel: +82-31-8086-3185 Fax: +82-31-8086-2317 E-mail: [email protected]
We present the case of a 78-year-old female who experienced acute mental deterioration after vomiting. She showed severe hypercapnia without definite lung disease and hypoxic injury on brain image. After the acute period, she still had excessive daytime sleepiness, and the hypercapnia aggravated during the night. Poly- somnography revealed severe obstructive sleep apnea, a sleep-related breathing disorder with a high apnea- hypopnea index of 60.2/h (mainly a hypopnea index of 59.0/h). She was diagnosed with combined obesity hypoventilation syndrome (OHS) and sleep-related breathing disorder, as the cause of daytime hypercapnia and excessive daytime sleepiness. Three months of successful bi-level positive airway pressure (BiPAP) therapy dramatically improved her daytime sleepiness and cognition. This case suggests that patients with OHS can be susceptible to hypoxic brain damage, and emphasizes the importance of the recognition and diagnosis of OHS and appropriate treatment with BiPAP therapy. J Sleep Med 2022;19(1):34-37
Keywords: Obesity hypoventilation syndrome; Bilevel positive airway pressure; Hypoxic brain damage.
INTRODUCTION
Obesity hypoventilation syndrome (OHS) is a sleep-relat- ed hypoventilation disorder defined as the presence of obesity (body mass index >30 kg/m2) with chronic daytime hypercap- nia (PaCO2 ≥45 mm Hg) in patients without any other causes to explain alveolar hypoventilation.1,2 The diagnosis of OHS is important, given the clinical aggravation leading to respiratory dysfunction along with the mortality rate in underdiagnosed patients.3 Also, OHS has been rising and is now a relatively common cause of chronic respiratory failure with hypercapnia, as obesity rates continue to increase. Therefore, an accurate di- agnosis and therapeutic approach for OHS are necessary. We report a case of hypoxic brain damage in a patient with OHS who was treated with bi-level positive airway pressure (BiPAP) therapy.
CASE REPORT
An obese 78-year-old female was admitted to the neurologi-
cal department because of acute mental deterioration. A nurs- ing assistant checked whether she had slept the night before and found that she was lying in bed, with vomiting and uncon- sciousness, the following morning. She had a history of hyper- tension, diabetes, and mild cognitive impairment. She could barely walk and was assisted by a walker as she was both over- weight and aging. There was no history of infection or intesti- nal disease. She had no respiratory problems, had never smoked, and usually did not suffer any related symptoms, such as dys- pnea. Physical examination revealed a height of 160 cm, weighed of 81.0 kg, and body mass index of 31.6 kg/m2, indicating obe- sity. On neurological examination at arrival in the emergency department using an oxygen mask with 15 L/min flow, her consciousness level was a semi-coma status, with a Glasgow Coma Scale (E2, M4, V1) of 7. Furthermore, her brain stem re- flexes were normal without other neurological deficits. The ini- tial arterial blood gas test under oxygenation showed severe respiratory acidosis and hypercapnia (pH 7.111, HCO3 38.8 mEq/L, PaCO2 120.5 mm Hg, PaO2 130.6 mm Hg, and SaO2 97.1%), and airway intubation and mechanical ventilation were performed. There were no specific findings in the blood tests performed (including ammonia, infection marker, glu- cose, and thyroid hormone levels) to differentiate the various
CASE REPORT pISSN 2384-2423 / eISSN 2384-2431
This is an Open Access article distributed under the terms of the Creative Com- mons Attribution Non-Commercial License (https://creativecommons.org/licens- es/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
J Sleep Med 2022;19(1):34-37 https://doi.org/10.13078/jsm.210027
encephalopathies. Following mechanical ventilation, her hypercapnia im-
proved within three hours of arrival at the hospital, and her mental state recovered within five hours. Diffusion-weighted brain magnetic resonance imaging (MRI) performed on the fifth day after admission showed acute restricted lesions in the bilateral basal ganglia, indicating hypoxic brain damage (Fig. 1). Although the patient was clearly alert, a mechanical ventilator was applied for 12 days, because CO2 retention was not adequately resolved. There was no evidence of aspiration pneumonia on initial chest computed tomography (CT) with contrast, but prophylactic antibiotics were administered for 12 days, during ventilator application. The results of the arterial blood gas test after the ventilator removal still showed mild re- spiratory acidosis (a pH of 7.389, HCO3 29.9 mEq/L, PaCO2 49.2 mm Hg, PaO2 75.0 mm Hg, and SaO2 94.5%).
In the other exploration of respiratory failure, there were no anatomical explanations for hypoventilation or findings suggestive of heart failure, pulmonary hypertension, and pul- monary thromboembolism through various tests, such as echo- cardiography, pulmonary thromboembolism-CT, and bron- choscopy. However, the patient still showed hypercapnia upon waking in the morning (peak PaCO2 56.3 mm Hg), and this value was higher than that in her awakened state during the daytime (peak PaCO2 48 mm Hg). A pulmonary function test was performed two days after the removal of mechanical ven- tilation in a patient-cooperative state and showed a severe re-
strictive pattern: the forced expiratory volume in one second/ forced vital capacity ratio (80%) was greater than normal, and the forced vital capacity (37%) was low, but there were no clear pulmonary diseases, such as chronic obstructive pulmonary disease (COPD) or asthma. Despite preserving her alertness, the patient showed excessive daytime sleepiness and snoring. She was usually very sleepy during the day and fell asleep while speaking. Cognitive impairment was confirmed through a mini-mental state examination score of nine. We suspected not only sleep breathing disorder, but also OHS as her diagno- sis based on findings of hypercapnia, particularly during ear- ly morning and nighttime, along with a history of obesity. On day 19 following admission, a split-night polysomnography (PSG) study was performed. The PSG revealed severe obstruc- tive sleep apnea (OSA), with a high apnea-hypopnea index (AHI) of 60.2/h (mainly a hypopnea index of 59.0/h). The PSG (Fig. 2) also showed sleep-aggravated hypercapnia and noctur- nal hypoxemia during rapid eye movement sleep, with hypop- nea events. In addition, the maximum end-tidal carbon diox- ide values were 51 mm Hg during awakening and 61 mm Hg during sleep. The continuous positive airway pressure (CPAP) was adjusted by increasing the pressure from 4 to 15 cm H2O, but hypoventilation and hypercapnia still occurred, leading to BiPAP titration, even during limited night hours. During titra- tion, the optimal BiPAP pressure was determined, with an in- creased inspiratory pressure of 18 cm H2O and expiratory pres- sure of 12 cm H2O at a nadir AHI of 2/h. After three months of
Figure 1. Diffusion-weighted magnetic resonance imaging of brain shows high signal intensity on bilateral basal ganglia (white arrows) but low signal intensity on apparent diffusion coefficient map.
36
OHS and BiPAP
BiPAP use, the arterial CO2 retention in the morning was low- ered, from 55.4 mm Hg to 38 mm Hg, and the residual AHI was 4.1/h. She adhered to BiPAP therapy for an average of 7 hours and 17 minutes, with 99% usage during the prescribed days. The patient is being followed-up on an outpatient basis, with no clinical signs of dyspnea, edema, nor neurological symp- toms, including daytime sleepiness and cognitive impairment. Her family members subjectively believe that communication with the patient is smoother than before, and her cognitive de- cline improved, despite the lack of objective cognition or sleepi- ness measures. In summary, we report a case of OHS combined with OSA that presented with acute exacerbation of chronic respiratory failure and hypoxic brain damage. Furthermore, the patient’s condition improved after the BiPAP treatment. The patient provided written informed consent.
DISCUSSION
OHS is characterized by obesity and daytime hypercapnia that occurs in the absence of an explanation for hypoventila- tion.4 Previous studies have shown significant health impair- ments in these patients. They often endure prolonged periods of hospitalization and draw heavily on healthcare resources, with worsening comorbidities and high mortality.3-5
Patients with OHS suffer from OSA and exhibit severe and prolonged oxygen desaturation during sleep, which results from reduced lung volumes and increased airway resistance.6 Therefore, hypoxia in OHS is sustained, and notably worsens during sleep.
Prior studies have reported that patients with chronic respi- ratory insufficiency, such as COPD, are susceptible to hypoxic brain damage and cognitive dysfunction, including increased
inflammation and oxidative and physiological stress.7 Con- genital central hypoventilation syndrome is a disorder that af- fects hypoventilation during sleep, resulting in a shortage of oxygen and a buildup of carbon dioxide in the blood. This po- tentially leads to absent or reduced ventilatory and arousal re- sponses to sustained hypercapnia and, to a lesser extent, sus- tained hypoxia.8 Some studies have revealed that several brain regions in patients with congenital central hypoventilation syn- drome respond inappropriately to problems with ventilation or blood pressure. In prior study results, the brain lesions typ- ically appeared in the forebrain diencephalon, midbrain, and cerebellar areas.9 MRI findings of hypoxic brain damage pref- erentially indicate lesions in areas such as the cerebellar hemi- spheres, basal ganglia, or cerebral cortex.10 The patient in our presenting case exhibited hypoxia by asphyxiation from vom- iting, following accelerated aggravated hypercapnia on OHS. Given the clinical history and circumstances of the present case, hypoxic injury may be a convincing explanation for the patho- physiology of brain injury in the patient rather than other in- fectious, vascular, epileptic, genetic/congenital, metabolic, or toxic causes.
Chronic hypoventilation in patients with OHS exposes them to chronic hypoxia and daytime hypercapnia, which leads to an accumulated hypoxic burden and susceptibility to even mini- mal levels of hypoxic insult. OHS often remains underdiagnosed in clinical practice and presents with a lack of specific symp- toms or tools, such as in-lab PSG and carbon dioxide measure- ment.1 It is important for clinicians to be aware of and suspect the possibility of OHS, given that early detection and proper management are critical for improving patient quality of life and even averting mortality. Therefore, physicians must con- sider early ventilatory management to provide neuroprotec-
Figure 2. Polysomnography shows hypopnea (yellow squares), desaturation (pink squares), and hypercapnia (EtCO2 >40 mm Hg) during REM sleep.
Hong Y et al.
https://www.e-jsm.org 37
tion against delayed hypoxic brain damage during the acute phase in patients with OHS who have experienced a hypoxic event, and even in those without definite respiratory failure.
Patients with OHS combined with severe OSA should be treated with CPAP or BiPAP to manage sleep-disordered breath- ing and improve nocturnal gas exchange.6 However, high CPAP was insufficient for resolving the hypercapnia and hypopnea in this patient. Therefore, we adjusted the BiPAP to provide pres- sure support and improve hypoventilation. This case study sug- gests that patients with OHS may be susceptible to anoxic dam- age. Notably, we would like to highlight the importance of concerns surrounding OHS in obese patients and introduce successful treatment with non-invasive ventilation in order to prevent chronic respiratory failure.
Conflicts of Interest The authors have no potential conflicts of interest to disclose.
ORCID iDs Yooha Hong https://orcid.org/0000-0002-8693-2831 Han Beet Kim https://orcid.org/0000-0003-1806-7687 Min Jun Song https://orcid.org/0000-0001-7416-9149 Heejung Mo https://orcid.org/0000-0001-7810-035X Hee-Jin Im https://orcid.org/0000-0002-8979-6521
Author Contributions Conceptualization: Hee-Jin Im. Data curation: Han Beet Kim, Min Jun
Song, Heejung Mo. Formal analysis: Yooha Hong. Investigation: Yooha Hong, Heejung Mo. Methodology: Yooha Hong, Hee-Jin Im. Project ad- ministration: Hee-Jin Im. Supervision: Hee-Jin Im. Visualization: Yooha Hong. Writing—original draft: Yooha Hong. Writing—review & editing: Hee-Jin Im.
Funding Statement None
1. Masa JF, Pépin JL, Borel JC, Mokhlesi B, Murphy PB, Sánchez-Quiroga MÁ. Obesity hypoventilation syndrome. Eur Respir Rev 2019;28:180097. https://doi.org/10.1183/16000617.0097-2018.
2. Iftikhar IH, Roland J. Obesity hypoventilation syndrome. Clin Chest Med 2018;39:427-436. https://doi.org/10.1016/j.ccm.2018.01.006.
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