Abnormalities of the Respiratory Function and Control of Ventilation in Patients with Anorexia nervosa

Abstract

Background: Anorexia nervosa is a good model to study the effects of malnutrition on the respiratory system, since it excludes the consequences that some chronic diseases can have on the lung. Objective: The objective of this study was to assess pulmonary function and alterations in the respiratory system in patients with anorexia nervosa. Methods: Twenty-two women, 12 with anorexia nervosa and 10 healthy volunteers, were studied. Anthropometric data were gathered for all the participants. In every case, an arterial blood gas test and functional respiratory study, that included spirometry, plethysmography, measure of maximum muscular respiratory pressure and study of the ventilatory pattern at baseline and after hypercapnic stimulation, were performed. Results: No significant differences were found in mean age and height in both groups of patients but there was a difference in body mass index (p < 0.05). In pulmonary function tests, an increase in residual volume (RV), RV/total lung capacity (TLC) ratio and functional residual capacity and a decrease in maximum respiratory pressure were found in patients with anorexia nervosa compared to the control group (p < 0.05). Differences were also found in the ventilatory pattern, with a reduction in minute ventilation and occlusion pressure as well as a decreased response of these parameters to hypercapnic stimulation (p < 0.05) in the patients with anorexia nervosa. Conclusion: In patients with anorexia nervosa, a significant elevation in RV, in the RV/TLC ratio and in functional residual capacity and a decrease in the maximum respiratory pressure were noted. In addition, they present an alteration in the central respiratory drive and a response of the respiratory system to hypercapnic stimulation. Although these alterations have no repercussion on the maintenance of gas exchange in baseline conditions, they may have in extreme situations.

Respiratory acidosis in adolescents with anorexia nervosa hospitalized for medical stabilization: A retrospective study

“…30 Our patient group also demonstrated a significant improvement in MNHR and in orthostatic heart rate changes during hospitalization as seen in other studies. 31 The respiratory acidosis found in our study could result from several physiological mechanisms that have been described in patients with AN: impairment of the respiratory muscle strength and performance, in particularly diaphragmatic function, [13][14][15][16][17][18][19] adverse effects on control of breathing, 14,20 and possible alterations of lung structure (emphysemalike changes). [21][22][23][24][25] Gonzalez-Moro et al, 14 in a study looking on respiratory function and control of ventilation in 12 women with AN, found that they had normal blood gases at baseline and presented a slower and more superficial respiratory pattern compared to a control group.…”

“…On the contrary, several investigators reported blood gases within the normal range. 11,14,17 It was suggested that the reduction in oxygen consumption and in pCO 2 production and energetic output present in subjects with AN can delay the onset of hypercapnia. 20,34 Furthermore, it has been assumed that hypercapnia does not generally appear before the respiratory muscular force reaches a value inferior to 30% of its predicted value.…”

“…11,13,14,15,17,20,25 A few were conducted on patients in the ''stable'' or chronic stage of their illness. 11,13,14,20 Some studies included a relatively small number of participants.…”

“…[1][2][3][4][5][6][7][8][9][10] However, there is a relative paucity of information regarding the effects of AN on the respiratory system in the malnourished stage of the disease, especially in adolescence. [11][12][13][14][15][16][17][18] Venous blood gases can serve as an additional metabolic marker for the assessment of patients with different types of eating disorders (metabolic alkalosis as an indicator for vomiting and volume contraction secondary to dehydration or metabolic acidosis in profound dehydration). Therefore, the clinical protocol for treating patients with eating disorders in our adolescent medicine unit includes a venous blood gas analysis.…”

“…Previous studies reported normal blood gases in patients with AN, 11,14,17 despite evidence for impairment of the respiratory muscle strength and performance (in particularly diaphragmatic function), [13][14][15][16][17][18][19] adverse effects on respiratory control, 14,20 and possible alterations of lung structure. [21][22][23][24][25] Over the years, our clinical impression was different than what was previously described as we noticed hypercapnia and mild respiratory acidosis to be a common phenomenon in patients with AN admitted for medical stabilization.…”