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Dyspnoea

Bariatric surgery improves dyspnoea by increasing ERV

It is believed that the decrease in ERV in obese patients is primarily due to the effect of abdominal contents on diaphragm position, leading to dyspnoea by individuals with obesity

Bariatric surgery improves dyspnoea in patients with obesity by inducing weight loss and increasing expiratory reserve volume (ERV), according to researchers from Reims University Hospital, Reims, France. The study, ‘Improvement of dyspnoea after bariatric surgery is associated with increased Expiratory Reserve Volume: A prospective follow-up study of 45 patients’, was published in PlosOne.

Obesity has a negative effect on lung volumes and the abnormality most frequently associated with obesity is decreased ERV, which is exponentially correlated with increased BMI, while total lung capacity (TLC) is usually normal. Dyspnoea is a very common and crippling symptom in obesity with approximately 80% of obese people experiencing dyspnoea in their daily lives.

It is believed that the decrease in ERV in obese patients is primarily because of abdominal contents on diaphragm position, leading to dyspnoea by individuals with obesity.

However, few studies exist that have assessed the changes in dyspnoea after bariatric surgery and the association between variations in dyspnoea and lung function tests after bariatric surgery. Therefore, the researchers sought to determine if bariatric surgery is associated with an improvement of dyspnoea in daily living according to the modified Medical Research Council (mMRC) scale in patients with obesity. The mMRC scale consists of five statements that almost entirely describe the range of dyspnoea from none (grade 0) to almost complete incapacity (grade 4). The mMRC scale is the most commonly used validated scale to assess dyspnoea in daily living in chronic respiratory diseases.

In addition, they assessed the effects of bariatric surgery on lung function tests (spirometry, plethysmography, arterial blood gases and 6MWT) and the relationships between improvement of dyspnoea and changes in lung function tests (especially ERV) after bariatric surgery.

Between January 2014 and October 2015, 45 adult patients had systematic respiratory evaluation before bariatric surgery and subsequently underwent bariatric surgery were included in the study. Patients were excluded if they did not attend the postoperative evaluation or if they presented with lung or neuromuscular disease. Patients had lung function tests were performed before and six to 12 months after bariatric surgery.

Outcomes

mMRC scores before and after bariatric surgery were available for 42 of the 45 patients. The authors noted that dyspnoea was a very common symptom before surgery with 90% (n=38/42 patients) of patients experienced dyspnoea in daily living with a mMRC score ≥ 1 and 91% (n=41/44 patients) of patients experienced dyspnoea on exertion with a Borg score ≥ 1 at the end of the six-minute walk test (6MWT).

The mean mMRC score was 1.5±0.9 before bariatric surgery and was significantly improved to 0.7±0.7 after surgery (p<0.0001). According to the Borg scale at the end of the 6MWT, dyspnoea on exertion was significantly improved by 3.6±2.2 to 2.1±1.9 after surgery (p<0.0001). Among the patients who experienced dyspnoea in daily living according to the mMRC scale (mMRC ≥1) before surgery (n=38), dyspnoea was improved after surgery with 25 patients (66%) exhibiting a decrease in the mMRC score ≥1.

Pulmonary function tests (PFTs) showed a 75% increase in ERV after surgery (from 0.55±0.35L to 0.96±0.41L) (p<0.0001), a 27% increase in RV (from 1.69±0.58L to 1.89±0.56L) (p=0.04) and a 10% decrease in IC (from 3.14±0.62L to 2.80±0.58L) (p<0.001) (Figure 1).

Figure 1: Comparison of Inspiratory Capacity (IC), Expiratory Reserve Volume (ERV) and Reserve Volume (RV) before and after bariatric surgery *p<0.05; **p<0.0001

Thirty-eight patients (90%) experienced dyspnoea in daily living before bariatric surgery (mMRC ≥ 1). After bariatric surgery, dyspnoea improved in 25/38 patients (66%) but did not improve in 13/38 patients (34%). No patient experienced more severe dyspnoea after surgery according to the mMRC scale.

Regarding PFTs, ERV was more markedly improved in the group of patients in whom dyspnoea was improved after surgery than in the group of patients with no improvement of dyspnoea (respectively +0.49±0.3 L and +0.17±0.32L; p=0.01).

“This is the first study to specifically assess the relationships between dyspnoea in daily living according to the mMRC scale and lung function tests and laboratory parameters, before and after bariatric surgery in patients with obesity, the authors write. “As expected, our study shows that weight loss associated with bariatric surgery is associated with an improvement of dyspnoea in daily living and an increasing of ERV. In particular, our study highlights an association between dyspnoea improvement according to the mMRC scale and increased ERV after bariatric surgery in patients with obesity who experienced dyspnoea before surgery.”

Interestingly, the authors report that dyspnoeic patients in whom dyspnoea was improved after bariatric surgery had a more marked increase in ERV and a more marked decrease in IC and a decrease in TLC, compared to patients in whom dyspnoea was not improved, suggesting that the predominant mechanism of dyspnoea in obesity related to lung volumes is not the decrease in TLC (which is also usually normal in obesity), but the decrease in ERV (and consequently the increase in IC).

“This prospective study shows that bariatric surgery improves dyspnoea in daily living according to the mMRC scale in patients with obesity,” the researchers conclude. “It highlights an association between improvement of dyspnoea after bariatric surgery and increased ERV, suggesting that improvement of dyspnoea after weight loss associated with bariatric surgery could be partly related to increased Expiratory Reserve Volume which is the lung volume abnormality most frequently associated with obesity.”

To access this paper, please click here

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