Characteristics of Obese Patients with Acute Hypercapnia Respiratory Failure Admitted in the Department of Pneumology: An Observational Study of a North African Population

Abstract

Background. Acute hypercapnic respiratory failure (AHRF) is a common life-threatening event in patients with obesity hypoventilation syndrome (OHS). Objectives. To study the clinical pattern, noninvasive ventilatory support, as well as the short- and long-term outcomes of patients with OHS admitted in a ward because of AHRF. Methods. We conducted a retrospective cohort study including all adults with OHS $\text{aged}\ge 18-\text{year}-\text{old}$ , admitted in a 90-bed-ward for AHRF. Results. A total of 44 patients were included. Fifteen (34.1%) and 29 (65.9%) patients were diagnosed with malignant OHS (mOHS) and nonmalignant OHS (non-mOHS), respectively, while 36 (81.8%) had coexisting obstructive sleep apnea hypopnea syndrome (OSAHS). Patients with mOHS had a significantly higher rate of heart failure (100% vs. 31%; $p<0.001$ ), chronic renal insufficiency (CRI) (73.3% vs. 41.4%; $p=0.04$ ), and dyslipidemia (66.7% vs. 34.5%; $p=0.04$ ) than those with non-mOHS. The mean forced vital capacity (FVC) in our patients was of $59.5\%\pm 18.5$ of the predicted value, lower than what is usually reported in stable patients with OHS. At hospital admission, more than two-thirds ( $n=34$ , 77.3%) were misdiagnosed as having asthma exacerbation ( $n=4$ , 4.9.1%), chronic obstructive pulmonary disease (COPD) exacerbation ( $n=12$ , 27.3%) and/or heart failure ( $n=29$ , 65.9%). Acute pulmonary oedema (ACPE) ( $n=16$ , 36.4%) and acute viral bronchitis ( $n=12$ , 27.3%) were the main identified causal factors, while no cause could be determined in 5 (11.4%) patients. Noninvasive positive pressure ventilation (NIPPV) using bilevel positive airway pressure (BIPAP) was very highly effective to treat AHRF, with only 2.27% of patients failing the modality. Median overall duration of ventilation was 9 hours per day (1.3–20) and was significantly longer in patients with mOHS than in those with non-mOHS (10 [6–18] vs. 8 [1.3–20], respectively; $p=0.01$ ). Forty two of the forty-three patients discharged alive were treated with BIPAP or continuous positive airway pressure (CPAP) in 26 and 16 patients, respectively. The probability of survival was 90% at 12 months, while the probability of readmission for a new episode of AHRF was 56% at 6 months and 22% at 12 months, respectively. Conclusion. AHRF in OHS patients is a life-threatening event which can be successfully and safely treated with BIPAP, with a low long-term mortality even in patients with mOHS.