4. Discussion
M. pneumoniaepneumonia is a pulmonary infection caused by infection with M. pneumoniae . The prevalence ofM. pneumoniae pneumoniais gradually increasing in children. Furthermore, a study involving 27,498 pediatric patients in North China reported that 37.5% of these children hadM. pneumoniae pneumonia; during the peak of this disease, an epidemic took place every 2–3 years (13). Almost 90% of casesoccur in families that experience multiple cases, and immunity is not long lasting (14). The most common symptoms at onset are fever and cough. These symptoms tend to have a long duration and are prone to re-occur, adversely affecting the respiratory system. Furthermore, M. pneumoniae infection can lead to a range of complications, including hemolysis, rash, joint pain, and swelling. In addition, the infection can exert severe effects on the nervous and cardiovascular systems, leading to aseptic meningitis or meningoencephalitis, arrhythmia, heart failure, chest pain, and other severe complications(13, 15-18).
After invading the respiratory tract,M. pneumoniae localizes between the cilia and adheres to the surface of epithelial cells via adhesive organelles, thus preventing mucociliary clearance and phagocytosis(19). This effect makes it very difficult for the body to remove sputum containing M. pneumoniae and its metabolites.Furthermore,M. pneumoniaeinfection can lead to inflammatory edema in the airways, thus causing the tracheal wall to thicken; this effect is exacerbated by the accumulation of sputum. These factors can have an adverse effect on recovery time (20). Previous research also reported that M. pneumoniae adhesion inducesthe synthesis of hydrogen peroxide; this endogenous form of reactive oxygen species (ROS) can cause oxidative stress damage(21). The accumulation of ROS,such as peroxides, in host epithelial cells can lead to damage, including vacuolar degeneration, mitochondrial swelling, cell dissolution, and necrosis(22).
The clearance of sputum is driven by a combination of rhythmic waving of the cilia and coughing; this combination of mechanismsrepresents the body’s protective respiratory reflex to remove secretions, or foreign bodies, from the respiratory tract through airflow and vibration(23). In children, M. pneumoniae pneumonia weakens ciliary movements and reduces lung function, thus making it very difficult for the body to discharge sputum(23).Therefore, when treating children with M. pneumoniae pneumonia, it is very important to provide sputum clearance assistance to promote the effective clearance of sputum containing metabolites of M. pneumoniae .This process helps to avoid the development of further complications. A previous study highlighted that the formation of sputum plugs in children with M. pneumoniaepneumonia results in significantly poorer chest imaging results and a significant increase in the time required for fever remission (24).
The HFCWO systemcan simulate the physiological process of normal coughing. This system involves anair-pulse generatorconnected toan inflatable vest, thus causing the patient’s chest wall to vibrate. In a recent review of oscillating devices for airway clearance in patients with cystic fibrosis, the HFCWO system was described as a routine form of treatment (25). In a study of patients with cystic fibrosis combined with exacerbation of chronic pyoobstructive bronchitis, the HFCWO system led to a significant improvement in lung function, as compared with a control group, both in terms of FEV1 (10.0 ± 4.6 vs 6.9 ± 3.6% for FEV1; P = 0.04) and FVC (9.5 ± 4.8 vs 5.9 ± 3.8%; P = 0.03) (26).The HFCWO system generates directional drainage forces and a vibrating airflow between the lungs and the airway, thus loosening and clearing the sputum by shear force. Furthermore, this system stimulates cilia on the wall of the airways to help move the sputum along the air passage, ultimately helping the patient to discharge the sputum (6). HFCWO is widely used for treating chronic obstructive pulmonary disease and for assisting with postoperative sputum clearance in critically ill patients. Research has shown that HFCWO is effective and helps to recover airway function (25). In a study of patients undergoing single-port video-assisted thoracoscopic surgery lobectomy, Zhu et al. found that FEV, FVC, and PaO2, were all higher in patients treated with HFCWO than in a control group (27). In a study of bronchiectasis, HFCWO significantly reduced the rate of hospitalization (from 1.3±1.0 to 0.46±0.81; P<0.0001), significantly reduced the use of antibiotics (from 2.5±0.86 to 2.1±0.92 courses/year; P<0.0001), and reduced the decline in FEV1(from 1.85 ± 0.60 to 1.89 ± 0.60 L) (28), although the latter was not significant. Although HFCWO has been widely used as a clinical treatment, little is known as to how it might help children with M. pneumoniae pneumonia.
The purpose of the present study was to evaluate whether HFCWO could improve the symptoms of children withM. pneumoniae pneumonia. HFCWO, which uses high-frequency chest wall vibration to help patients to expectorate sputum, resulted in a total effective rate that was significantly higher than that in the control group.In addition, HFCWO obviously shortened the duration of convulsive cough and fever. Furthermore,compared to the control group, patients receiving HFCWO showed a significant improvement in lung function (FEV1, FVC, and PEF, relative to predicted values). HFCWO also accelerated improvementsin chest X-rays and reduced the length and cost of hospital stays.
There are several limitations to this study that need to be considered. First, because the technology has not yet been popularized, the parents of patients were not very receptive to the technology; this inevitably led to a small sample size. Second, as this form of treatment is still being explored, this research study was only based in a single center. Future research should aim to increase sample size and involve multiple centers.