Abstract
Chronic obstructive pulmonary disease (COPD) is a slowly progressive disease characterized by inflammation that involves the airways, lung parenchyma, and pulmonary vasculature commonly associated with lung function decline and alveolar impairment of gas exchange. All these alterations can lead to hypoxaemia. In COPD hypoxaemia presenting refractory to very high concentration of inspired O2 with a drop of SpO2 (peripheral saturation) > 5% during the upright position and an improvement on recumbency (platypnea/ortodeoxya syndrome) can be suspect for righ-to-left shunt, e.g. intrapulmonary shunt or most frequently a patent foramen ovale.
Among COPD patients, several studies showed a higher prevalence of patent foramen ovale than in general population (70% versus 35%). Chest imaging and echocardiogram with bubble contrast should be the first clinical assessment to differentiate subjects with intracardiac shunt (such as in Patent foramen ovale) from those with extracardiac (or intrapulmonary) one.
Definitive treatment of right-to-left shunt involves percutaneous closure but literature provides conflicting data about indications and results, particularly regarding selection of COPD patients to be subjected to such intervention. Several key factors should be taken into account from a clinical and ethical point of view: first periprocedural complications, then echocardiographic assessment of right ventricular systolic and diastolic performance should be performed to rule out severe pulmonary hypertension and to avoid further post-procedure clinical deterioration; in addition, quality of life should be assessed.
In our experience, among 12 patients with patent foramen ovale 5 were affected by COPD GOLD III with refractory hypoxaemia. After evaluation of right ventricular performance, only 2 patients were eligible for patent foramen ovale closure with the Amplatzer device; long-term follow-up showed discontinuation of oxygen therapy and improvement in quality of life. Therefore, COPD patients with hypoxaemia refractory to high O2 supplementation must be thoroughly assessed taking into account a careful history and a targeted physical examination. The presence of patent foramen ovale should raise suspicion of a right-to-left shunt. If a patent foramen ovale is identified, evaluation of pulmonary function, right ventricular systolic reserve, and severity of pulmonary hypertension is mandatory for closure.
The development of a multidisciplinary team to conduct a multicenter study is necessary to understand if and when the right-to-left shunt in COPD can benefit from this novel therapy.