This document summarizes research on obesity hypoventilation syndrome (OHS). It finds that compared to other obese patient groups, patients with OHS have higher healthcare costs and risks of serious cardiovascular disease leading to early mortality. However, diagnosis and treatment of OHS is often late. Non-invasive ventilation can improve symptoms and gas exchange in OHS, but more research is needed comparing non-invasive ventilation to other treatments like CPAP. Weight loss through bariatric surgery may reverse the effects of OHS, but long-term data is limited. Overall, the document examines the morbidity, mortality and treatment options for OHS.

2. Severe obesity BMI > 30 kg/m2 and diurnal PaCO2 > 45 mmHg
In the absence of other known cause of hypoventilation
Adapted de Pépin, Borel, Tamisier, Lévy

3. OR 4.0
Adjusting for age sex BMI
Mortality is increased compared to “simple obesity” suggesting specific
cardiovascular morbidity
Nowbar. Am J Med 2004

4. 
Compared with eucapnic morbidly obese patients and
eucapnic patients with sleep-disordered breathing, patients
with OHS have increased health care expenses and are at
higher risk of developing serious cardiovascular disease
leading to early mortality.

Despite the significant morbidity and mortality associated
with this syndrome, diagnosis and institution of effective
treatment occur late in the course of the syndrome.
Mokhlesi B, Kryger MH, Grunstein RR. Assessment and management of
patients with obesity hypoventilation syndrome. Proc Am Thorac Soc. 2008

5. 
This is believed to be the ideal treatment for OHS.
 Respiratory insufficiency, pulmonary hypertension and sleep disorders
[Dixon JB 2012] can be reversed if patients achieve a normal
weight, although only a few maintain a significant weight reduction
for a long period.

Although bariatric surgery has been tested as an alternative
treatment for OSA patients with extreme obesity, there are still
some doubts about the benefit of this kind of therapy [Dixon JB
2012].

Less data are available in the case of OHS especially as regards
the long-term consequences. [Douglas C, 2012]

Moreover, bariatric surgery can be an alternative for only a
minority of OHS patients due to the morbidity and mortality
inherent in the surgical procedure itself

6. Behaviorally , diet and pharmacologically weight loss in OSA
Douglas C. OSA and Weight Loss: Review. Sleep Disord. 2012

7. Surgically induced weight loss in OSA

8. Surgical vs Conventional Therapy for Weight Loss Treatment of OSA
– BODY WEIGHT
Dixon JBM, JAMA 2012

9. Surgical vs Conventional Therapy for Weight Loss Treatment of
OSA – Apnea-Hypopnea Index
Dixon JBM, JAMA 2012

10. “I have lost that tendency to sleepiness which made me
think of the fat boy in Pickwick. My color is very much
better and my ability to work is greater.“
William H. Taft, Präsident der USA 1909-1913
Adapted from Randerath W

11. 

NIV consists of the application of intermittent
positive pressure ventilation, normally with
bilevel positive pressure, using nasal or nasooral masks.
NIV can improve nocturnal hypercapnia by:
 increasing alveolar ventilation,
 preventing obstructive events,
 improving leptin action (or preventing the
resulting central hypoventilation) and
 providing more efficient direct muscular repose.

12. 
Several series of cases and one RCT on 37
patients with mild hypercapnia [Borel 2012]
have shown improvements:
 in the clinical picture, arterial blood gases and sleep
disorders with this treatment [Massa, 2001].
 A reduction in days of hospital admission has been
observed in longitudinal studies [Berg G 2001].

NIV decreases mortality in a series of patients
treated with NIV, compared with other studies in
which patients were not treated or refused
treatment [Pepin 2012].

13. Borel et al, Chest 2012. RCT – 19 NIV (BiPAP) vs 18 Controls
Daytime PCO2
Sat mean
Sat < 90%
Respiratory
arousal

14. 
CPAP prevents obstructive events in patients
with OHS but the PaCO2 is not normalized in all
patients.

Only one RCT has evaluated the clinical, PaCO2
and polysomnographic improvements in CPAP
vs. NIV in 36 OHS patients selected for their
favorable response to an initial night of CPAP
treatment [Piper 2007].

More RCTs are need !
Piper AJ et Randomized trial of CPAP vs bi-level support in the treatment of Obesity
Hypoventilation Syndrome without severe nocturnal desaturation. Thorax 2008;63:395

15. Piper AJ, al. RCT: CPAP vs bi-level in OHS without severe nocturnal desaturation.
Thorax 2008
 This is the only RCT
comparing NIV vs CPAP in
36 OHS patients who
respond to an initial night
with CPAP treatment.
 The follow up was 3
months and there were no
differences in gas
exchange, sleepiness and
QL.
 The weakness of this
study is the selection of
patients (no severe
nocturnal desaturation)

16. Exclusion Criteria
Patients with persisting hypoventilation during initial CPAP Trial
Piper at al Thorax 63; 395-401

17. SpO2
HR
SpO2
HR
SpO2
HR

18. SpO2
HR
SpO2
HR
SpO2
HR
Hypercapnic OSA

19. SpO2
HR
SpO2
HR
SpO2
HR
Hypercapnic OSA
Hypercapnic OSA & OHS

20. SpO2
HR
SpO2
Hypercapnic OSA
Hypercapnic OSA & OHS
HR
SpO2
HR
Hypercapnic OHS

21. SpO2
HR
SpO2
Hypercapnic OSA
Hypercapnic OSA & OHS
HR
SpO2
HR
10% of Patients with OHS have no co-existent OSA1,2,3
1. Kessler et al. Chest 2001; 120:369-71
2. Perez de Llano et al . Chest 2005; 128: 587-594
3. Mohhlesi et al. Sleep Breath 2007; 11: 117-24

22. Does NIV (Bilevel) Influence Survival ?
3%
9%
20%
23%
Nowbar et al Am J Med 2004; 116: 58-9
Budweiser et al J Intern Med 2007; 261:375-383

29. Conclusão : (n=36) Este estudo
sugere uma relação entre
obesidade e restrição pulmonar
e aponta para um impacto
positivo da cirurgia bariátrica
na Função Respiratória .

30. IMC = 59,5 kg/m2
IAH = 76,8
SaO2 mínima = 67 %
SaO2 média = 83 %

31. IMC = 27,8 kg/m2
IAH = 2
SaO2 mínima = 94
SaO2 média = 95

32. 
Conclusões:
 Frequência elevada de Distúrbio Respiratório do Sono
em doentes candidatos a cirurgia de obesidade
 Limitação da predição de Distúrbio Respiratório do
Sono com base na apresentação clínica
 Face ao risco cirúrgico destes doentes o rastreio
sistemático com recurso a estudo do sono parece
mandatório
 A resolução do Distúrbio Respiratório do Sono com a
redução do peso é expectável na maioria dos doentes.

34. Hybrid Mode
Combine the advantages of pressure and
volume pre-set
 Target volume set based on ideal body weight
 Automatic adjustment of inspiratory pressure
(range setting)
 Difference between target VT and actual VT
modifies inspiratory pressure
 Changes of inspiratory pressure (1 cmH2O/min)
 Constant VT



35. *pre-post p<0.05
Follow up data
ST
AVAPS
PaCO2 (kPa)
6.1±0.9*
6.4±0.8*
PaO2 (kPa)
9.3±1.2
8.9±0.9
Weight
142±28*
139±29*
BMI
50±7
48±9*
ESS (/24)
7±5*
6±5*
58±14*
66±19*
Mean IPAP
23.2±3.1
21.5±5.0
Mean Vte
671±158
634±144
Mean Vte/kg ideal wgt
10.4±2.4
10.0±1.4
Compliance (hr/day)
5.7±1.9
4.2±2.9
SRI-SS (/100)

36. Follow up data
ST
AVAPS
PaCO2 (kPa)
6.1±0.9*
6.4±0.8*
PaO2 (kPa)
9.3±1.2
8.9±0.9
Weight
142±28*
139±29*
BMI
50±7
48±9*
ESS (/24)
7±5*
6±5*
58±14*
66±19*
Mean IPAP
23.2±3.1
21.5±5.0
Mean Vte
671±158
634±144
Mean Vte/kg ideal wgt
10.4±2.4
10.0±1.4
Compliance (hr/day)
5.7±1.9
4.2±2.9
SRI-SS (/100)
*pre-post p<0.05