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

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

Method: Prospective study.

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

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

Results: 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.

Discussion: 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.