Figures
- FIGURE 1
Management of patients with obesity hypoventilation syndrome (OHS) from diagnosis to integrated care to modify health trajectories. After being diagnosed with OHS, these patients are typically initiated on positive airway pressure (PAP) therapy (continuous positive airway pressure or noninvasive ventilation). Although respiratory insufficiency improves quite consistently in patients adherent to PAP therapy, pulmonary hypertension may also improve in some patients with OHS. There is no evidence that other cardiovascular and metabolic comorbidities improve with PAP treatment alone. Therefore, a multimodality therapeutic approach is necessary to combine PAP therapy with strategies aimed at weight reduction and increased physical activity. PaCO2: arterial carbon dioxide tension.
- FIGURE 2
Pathophysiology of obesity hypoventilation syndrome (OHS). The implicated mechanisms leading to daytime hypercapnia are, potentially, the obesity-related changes in the respiratory system, central hypoventilation, obstructive sleep apnoeas and hypoventilation during sleep, mainly during rapid eye movement (REM). PEEPi: intrinsic positive end-expiratory pressure; PaO2: arterial oxygen tension; FRC: functional residual capacity; ERV: expiratory reserve volume; RV: residual volume; TLC: total lung capacity.
- FIGURE 3
Obesity hypoventilation syndrome (OHS) management strategy. Continuous positive airway pressure (CPAP) could be first-line treatment for OHS patients with concomitant severe obstructive sleep apnoea (OSA). Noninvasive ventilation (NIV) should be considered as first-line therapy for OHS patients with no OSA or milder forms of OSA. If patients initially treated with CPAP have no favourable response to therapy despite objectively documented high levels of adherence to CPAP, they should be changed to NIV therapy. AHI: apnoea–hypopnoea index.
- FIGURE 4
Positive airway pressure adjustment in acute decompensated obesity-related respiratory failure. The adjustment of continuous positive airway pressure/expiratory positive airway pressure (EPAP) has the objective of eliminating obstructive events, snoring and intermittent oxygen desaturations. Adjustments in inspiratory positive airway pressure (IPAP) are aimed at eliminating hypoventilation and sustained hypoxaemia. For both EPAP and IPAP, the pressure should increase progressively until attaining the objectives (resolution of upper airway obstructive events and sleep hypoventilation) or until the maximal tolerated pressure is reached. Alternatively, EPAP/continuous positive airway pressure can be adjusted to eliminate obstructive apnoeas and IPAP can be further increased to eliminate obstructive hyponoeas, snoring and hypoventilation. With this strategy, the patient may require lower EPAP and therefore achieve higher levels of pressure support in order to improve hypoventilation [96]. Supplemental oxygen is habitually added to positive airway pressure therapy when an adequate oxygenation level is not achieved despite adequate titration of positive airway pressure therapy. NIV: noninvasive ventilation; PaO2: arterial oxygen tension; SaO2: arterial oxygen saturation.
Tables
- TABLE 1
Clinical features of patients with obesity hypoventilation syndrome based on an aggregated sample of 757 patients from 15 studies
Clinical features Mean (range) Age years 52 (42–61) Male % 60 (49–90) Body mass index kg·m−2 44 (35–56) Neck circumference cm 46.5 (45–47) pH 7.38 (7.34–7.40) Arterial PCO2 mmHg 53 (47–61) Arterial PO2 mmHg 56 (46–74) Serum bicarbonate mEq·L−1 32 (31–33) Haemoglobin g·dL−1 15 Apnoea–hypopnoea index 66 (20–100) SpO2 nadir during sleep % 65 (59–76) Per cent sleep time SpO2 <90% 50 (46–56) FVC % predicted 68 (57–102) FEV1 % predicted 64 (53–92) FEV1/FVC 0.77 (0.74–0.88) Medical Research Council
Dyspnoea class 3 or 4 %69 Epworth sleepiness scale score 14 (12–16) PCO2: carbon dioxide tension; PO2: oxygen tension; SpO2: arterial oxygen saturation measured by pulse oximetry; FVC: forced vital capacity; FEV1: forced expiratory volume in 1 s. Reproduced from [1] with permission from the publisher.
