A major cause for pulmonary complications in acute SCI patients is the inability to clear bronchial secretions. In cervical spinal cord injuries, nerves that innervate the diaphragm and associated muscles may be damaged, leading to impaired coughing ability. The failure to perform deep coughing can cause pulmonary problems in two ways. First, patients can be in immediate pulmonary distress from choking or aspiration. Second, the retention of mucus can lead to respiratory infections such as bronchitis or pneumonia. In 1 in 5 cases of acute tetraplegia, patients produce an excess of 1 L of mucous each day (Ramakrishnan Bhaskar et al. 1991), further demanding the need for effective coughing techniques. The peak cough expiratory flow necessary to clear bronchial secretions is 3.1 L/s (Bach et al. 1993), and SCI patients often test well below this number. Several mechanisms exist to improve coughing ability in patients with SCI. Manual assisted coughing is an effective option whereby a caregiver applies firm and rapid pressure to the abdomen to force air out of the lungs. Mechanical assisted coughing, most commonly by mechanical insufflation-exsufflation, stimulates coughing by having a machine fill the lungs with air and then quickly reverse the flow to create negative pressure and push out secretions (Volsko, 2013). Additionally, positive expiratory pressure therapy systems are handheld devices used to create pressure in the lungs and facilitate clearance of secretions (Volsko, 2013). If needed, more invasive procedures to remove secretions can be used, such as directly suctioning the trachea with a catheter. The comparison between these methods is a poorly researched area, with only one RCT comparing manual assisted coughing techniques to mechanical insufflation/exsufflation.
A single RCT found that mechanical insufflation/exsufflation is more effective at restoring cough than manual techniques alone (Pillastrini et al. 2006). This study did not test the efficacy of removing secretions directly, but instead tested them indirectly by measuring coughing ability through measurements such as forced vital capacity, forced expiratory volume, and peak cough expiratory flow. These measures were significantly improved with the addition of mechanical insufflation/exsufflation, demonstrating that these devices can enhance cough in acute SCI patients.
There is level 2 evidence (from one RCT; Pillastrini et al. 2006) in support of mechanical insufflation/exsufflation as an effective adjunctive therapy to the use of respiratory kinesitherapy for bronchial clearance in acute SCI patients.
Mechanical insufflation/exsufflation coupled with manual respiratory kinesitherapy may be effective for bronchial clearance during the acute phase post SCI.