PURPOSE: Exercise induced hypoxia is a characteristic feature of interstitial lung disease (ILD). Because chronic hypoxia is associated with pulmonary arterial hypertension (PAH), we postulated that PAH in ILD may be related to hypoxia induced by daily activity. This study was performed to evaluate the duration of hypoxia on daily living in patients with ILD and its relationship with PAH and desaturation during 6-minute walk test.
METHODS: Monitoring of 24-hour ambulatory pulse oximetric saturation (SpO2) and Holter were performed in 19 patients with ILD and desaturation during 6-minute walk test. Systolic pulmonary arterial pressure (SPAP) was estimated by echocardiography.
RESULTS: Twelve patients had PAH (SPAP>40mmHg). The duration of daytime hypoxia (SpO2 < 88%) was longer in patients with moderate-severe PAH (SPAP>50mmHg) than those with no or mild PAH during daily activity (11.6% vs. 5% of daytime). Six of nine patients with no or mild PAH walked more than 450m on 6-minute walk test, whereas nine of ten patients with moderate-severe PAH walked less than 450m. Total distance walked and the distance walked up to 80% SpO2 were significantly correlated with the duration of daytime hypoxia (r= -0.539, r= -0.666, p<0.05) and mean SpO2 (r= 0.657, r= 0.599 p<0.05). Cardiac arrhythmia occurred very rarely, but without any symptoms.
CONCLUSION: Exercise induced hypoxia seems to be associated with PAH in patients with ILD. Patients with moderate-severe PAH were hypoxic for significant period during daily life in spite of no resting hypoxia.
CLINICAL IMPLICATIONS: Supplemental oxygen may be helpful in patients with ILD and significant desaturation during 6 minute walk test.
DISCLOSURE: Dong Soon Kim, No Financial Disclosure Information; No Product/Research Disclosure Information