We present a 67-year-old male with amyotrophic lateral sclerosis (ALS) who developed left lower lobe atelectasis and respiratory failure caused by a large pneumoperitoneum after gastrostomy placement. The patient was successfully managed with paracentesis, postural measures, and continued application of noninvasive positive pressure ventilation (NIPPV). There is no clear evidence that links the use of NIPPV with an increased risk of pneumoperitoneum. The evacuation of air from the peritoneal cavity may help improve the respiratory mechanics in patients with diaphragmatic weakness such as the one presented.