The prevalence of pulmonary hypertension in COPD patients is increased at high altitudes compared with low altitudes. These and other results were described in a study published in Pulmonology.
Most of the knowledge about pulmonary hypertension in COPD is based on research done at sea level, with limited research showing the effect of high altitude. To address this issue, Colombian researchers analyzed the prevalence/severity of pulmonary hypertension in 176 patients with COPD living in Bogotá, a city with an altitude of 2640 meters. The investigators categorized patients by the severity of airflow limitation.
The prevalence of pulmonary hypertension was 56.3%, and the odds of having the condition increased according to airflow-limitation severity. Specifically, the chance of having pulmonary hypertension in those with mild airflow limitations was 31.6%; moderate airflow limitation, 54.9%; severe airflow limitation, 59.6%; and very severe airflow limitation, 77.8%. (P = .038). Pulmonary hypertension was severe in 7.3% of individuals with COPD and disproportionate in 3.4% of these individuals.
Risk factors correlated with pulmonary hypertension were arterial oxygen pressure (PaO2) and Global Initiative for Chronic Obstructive Lund Disease (GOLD) stage 4. The high prevalence of pulmonary hypertension in patients with mild to moderate airflow limitation indicated a higher risk of developing pulmonary hypertension in COPD patients living at high altitudes vs those with similar airflow limitation inhabiting lower altitudes. Severe pulmonary hypertension was also more prevalent at high altitudes compared with low altitudes.
High-altitude residents aged 40 years or more in the current study exhibited arterial and alveolar oxygen pressure (PaO2 and PAO2) of approximately 60 mmHg. The onset of hypoxic pulmonary vasoconstriction at these levels has been previously noted. Minute regional or general changes in alveolar ventilation and the ventilation/perfusion ratio could stimulate hypoxic pulmonary vasoconstriction and result in pulmonary hypertension.
The authors hypothesize that in COPD patients living at high altitudes, the early development of permanent or intermittent hypoxemia at rest or during sleep or exercise could occur. This phenomenon along with genetic factors, sleep disorders, or lung/systemic inflammation may mediate the pathogenesis of pulmonary hypertension.
One limitation of the current study is that there was a lower number of the patients in the cohort with mild airflow limitation as compared with other studies, which may impact the generalizability of the results to other populations living at similar altitudes.
The authors concluded that “the prevalence of PH [pulmonary hypertension] in patients with COPD living in Bogotá, a city located at HA [high altitude] (2640 m), is high and greater than that described at sea level, particularly in patients with less severe airflow limitation, suggesting a higher risk of developing PH for COPD patients living in HA compared to COPD patients with similar airflow limitation living at low altitudes. Likewise, the prevalence of sPH [severe pulmonary hypertension] and disproportionate PH was also higher at HA.”
Aguirre-Franco C, Torres-Duque CA, Salazar G, Casas A, Jaramillo C, Gonzalez-Garcia M. Prevalence of pulmonary hypertension in COPD patients living at high altitude. Pulmonology. Published online February 9, 2022. doi:10.1016/j.pulmoe.2021.12.006