Exertional desaturation is a common feature in patients with interstitial lung disease (ILD), even in those with only mild physiological impairments, reports a study presented at the 22nd Congress of Asian Pacific Society of Respirology (APSR 2017).

Moreover, ILD patients with worse lung function and severely impaired exercise capacity are more likely to be prescribed ambulatory oxygen therapy (AOT), according to  researchers.

The research team performed a retrospective study of 400 patients enrolled in two prospective ILD registers: the Alfred health (n=299) and Austin health (n=101) registers. Only those with baseline 6-minute walk test (6MWT) information were included.

Aside from baseline demographic data, the researchers also collected information on lung function tests, shortness of breath and respiratory questionnaire scores and oxygen therapy prescriptions.

In the total study cohort, 214 patients (mean age 67±10 years; 68 percent male) experienced a drop of ≤88 percent in the oxyhaemoglobin saturation during the 6MWT and were thus determined to have exertional desaturation, resulting in a prevalence rate of 54 percent. [APSR 2017, abstract AP285]

Nondesaturators (n=186) were significantly younger (64±13 years; p=0.02) and less likely to be male (48 percent; p=0.0014).

Exertional desaturation was more common in patients with impaired lung function. At least 80 percent of patients with <50 percent of the predicted forced vital capacity (FVC) were identified to have exertional desaturation.

In comparison, only around 30 percent of those with >75 percent of the predicted FVC had exertional desaturation. The trend reached statistical significance (p<0.001).

AOT alone was prescribed to 27 percent (n=58) of the sample, while 7 percent (n=14) were on long-term oxygen therapy. In multivariable logistic regression analysis, both 6MWT distance (odds ratio [OR], 0.993; 95 percent CI, 0.990 to 0.997; p<0.001) and FVC (OR, 0.970; 0.943 to 0.998; p=0.037) were significantly associated with the odds of being prescribed AOT.

Idiopathic pulmonary fibrosis was the most common type of ILD, diagnosed in 33.5 percent (n=134) of the patients. This was followed by chronic hypersensitivity pneumonitis (14 percent; n=57) and ILDs related to connective tissue diseases (11 percent; n=44).

Compared with nondesaturators, patients with exertional desaturation had significantly shorter 6MWT distances (450 vs 411 metres; p=0.0003) and higher scores in the shortness of breath questionnaire (29 vs 44 points; p<0.0001).