Overlap syndrome (OVS) is the concurrence of chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea (OSA), and is associated with poor outcomes.~COPD and obstructive sleep apnoea (OSA) are highly prevalent and different clinical COPD phenotypes that influence the likelihood of comorbid OSA.~The increased lung volumes and low body mass index (BMI) associated with the predominant emphysema phenotype protects against OSA whereas the peripheral oedema and higher BMI often associated with the predominant chronic bronchitis phenotype promote OSA.~The diagnosis of OSA in COPD patients requires clinical awareness and screening questionnaires which may help identify patients for overnight study.~Management of OSA-COPD overlap patients differs from COPD alone and the survival of overlap patients treated with nocturnal positive airway pressure is superior to those untreated.~high flow nasal cannula (HFNC), which delivers heated, humidified oxygen via a nasal cannula at high flow rates of up to 60 L/min, delivering a maximum of 100% oxygen, has been shown to be effective in the treatment of respiratory failure.~High velocity nasal insufflation (HVNI), a form of HFNC that utilizes a small bore nasal cannula to generate higher velocities of gas delivery than HFNC which uses large bore cannula, has the ability to accomplish complete purge of extra thoracic dead space at flow rates of 35 litres/min and may be able to provide ventilatory support in patients with respiratory failure in addition to oxygenation support in patients with obesity hypoventilation syndrome and overlap syndrome.~This study aims to evaluate the effectiveness of HVNI compared to NIMV in management of respiratory failure in patients with overlap syndrome.
High velocity nasal insufflation (HVNI), a form of HFNC that utilizes a small bore nasal cannula to generate higher velocities of gas delivery than HFNC which uses large bore cannula, has the ability to accomplish complete purge of extra thoracic dead space at flow rates of 35 litres/min and may be able to provide ventilatory support in patients with respiratory failure in addition to oxygenation support in patients with overlap syndrome.~This study aims to evaluate the effectiveness of HVNI compared to NIMV in management of respiratory failure in patients with obesity hypoventilation syndrome and overlap syndrome.