Unconventional use of high-flow nasal cannula in acute exacerbation of idiopathic pulmonary fibrosis with high levels of hypercapnia

Dear Editor,
A 50-year old man, never smoker, non-allergic, suffering from chronic gastritis, dyslipidemia, and idiopathic pulmonary fibrosis (IPF), diagnosed two years ago, came to our attention with global chronic respiratory failure due to acute exacerbation of IPF with clinical conditions in decline characterized by increasing dyspnea, edema and drowsiness. A high-resolution computed tomography (CT) scan showed an accelerated IPF model (Figure 1).
The functional tests showed a severe reduction in the diffusion lung capacity of carbon monoxide (DLCO) equal to 26%. Laboratory tests show­ed neutrophil leukocytosis and high inflammatory markers (VES and acute-phase protein C [PCR]). We administered antibiotics, corticosteroids and diuretic therapy. On admission to hospital, systemic arterial blood oxygen gas with a flow of 9 L min-1 showed severe respiratory failure with hypercapnia: pH 7.32; pCO2 79 mm Hg (11 kPa); pO2 46 mm Hg (6 kPa). The patient refused non-invasive ventilation (NIV) and we administered the treatment of high-flow nasal cannula (HFNC) with a flow rate of 60 L min-1 and a fraction of inspired oxygen (FiO2) of 0.56. After four hours the level of pCO2 was reduced to 73 mm Hg (10 kPa) and pO2 increased to 55 mm Hg (7 kPa). So, we performed serial measurements of gas values in the following days and we obtained a gradual fall of hypercapnia. The monitoring of blood gas values in the following days of hospitalization showed an improvement of respiratory failure after 8 days equal to 66 mm Hg (9 kPa) pCO2 and pO2 of 60 mm Hg (8 kPa) with FiO2 of 0.33; after 12 days pCO2 was 58 mm Hg (8 kPa), pO2 59 mm Hg (8 kPa) and pH of 7.41 with FiO2 0.32. With the use of HFNC pH in arterial blood gases gradually returned to the physiological range. FiO2 was slowly reduced until it reached a value of 0.3, and stabilization of pCO2 of approximately 55 mm Hg (7 kPa) was found. The X-ray images of the chest showed a slight improvement during hospitalization (Figure 2) and laboratory tests showed a reduction in neutrophil leukocytosis and inflammatory markers.
The interest of our clinical case is essentially due to the use of a high-flow nasal cannula for the treatment of patients with acute exacerbation of idiopathic pulmonary fibrosis with higher levels of pCO2. Typically, in various studies analyzing the effect of HFNC respiratory failure CO2 values do not exceed 55 mm Hg (7 kPa). In 2000, idiopathic pulmonary fibrosis (IPF) was defined as...


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