Respiratory functions in adolescents hospitalized for anorexia nervosa: a prospective study

To examine the effects of malnourishment on the respiratory system of adolescents with anorexia nervosa (AN) hospitalized for medical stabilization.

Prospective study.

hospitalized adolescents with recent onset (<1 year) AN.

adolescents hospitalized for other diagnoses. Excluded: participants with lung disease.

Patients' characteristics (mean ± SD) for the AN (n = 16) and the control group (n = 13) on admission were: age: 15.0 ± 1.7 vs. 15.2 ± 1.4 years, p = 0.7; body mass index (BMI): 15.5 ± 2.3 vs. 19.8 ± 2.9 kg/m², p < 0.001; venous pH 7.34 ± 0.02 vs. 7.38 ± 0.03, p < 0.001; PCO₂ 53.3 ± 4.1 vs. 42.5 ± 3.1 mm Hg, p < 0.001; and HCO₃ 28.7 ± 2.0 vs. 25.3 ± 2.4 meq/L, p < 0.001, respectively. There were no significant differences in nocturnal respiratory rates, pulse-oximetry oxygen saturations, or end-tidal CO₂. Pulmonary function tests (PFTs) in adolescents with AN revealed no obstructive, restrictive, or significant pulmonary vascular disease except for lower peak expiratory flow rates (PEFRs). During hospitalization (12.3 ± 3.8 days), their weight, BMI, mean nocturnal heart rate, and respiratory rate increased significantly, while their venous PCO₂ and HCO₃ decreased significantly without significant changes in PFTs.

Adolescents with recent onset AN, admitted for medical stabilization, demonstrate hypercapnia despite normal PFTs, except for decreased PEFRs. These could result from decreased respiratory muscle strength and/or abnormal control of breathing.