The majority of climate change or air pollution/hospitalization mortality studies relied on administrative data analyzing retrospective cohorts and were inconsistent in controlling by known confounders, including demographics, holidays, cigarette-smoking habits, socioeconomic status, BMI, influenza epidemics, season of the year, ambient temperature, humidity, barometric pressure, or medication use. β-Blockers are associated with increased mortality in oxygen-dependent patients with severe COPD.3 Furthermore, COPD severity, the specific cause of hospitalization or death, and even comorbidities and conditions were not available, and the question still remains as to which specific COPD comorbidity conditions are associated with air pollution/climate changes. Indications for hospitalization in patients with COPD include bacterial or viral pneumonia, cardiac arrhythmia, congestive heart failure, renal or liver failure, inadequate response of symptoms to outpatient management, inability to eat or sleep due to symptoms, worsening hypoxemia, worsening hypercapnia, changes in mental status, inability of the patient to care for her/himself, uncertain diagnosis, inadequate home care, and marked increase in dyspnea.4 Finally, barometric pressure has not been consistently considered. A previous study found a positive correlation between barometric pressure and blood oxygen saturation in the elderly,5 suggesting that barometric pressure may produce physiologic changes, and it should be considered a relevant weather variable in daily time series studies of morbidity and mortality in susceptible populations. Currently, there is a lack of air pollution/climate change studies analyzing the effect of barometric pressure on the population of patients who hypothetically represent probably those most susceptible to changes in barometric pressure (ie, oxygen-dependent patients requiring long-term oxygen therapy secondary to COPD or any other illness causing chronic respiratory failure).