Mechanical insufflation-exsufflation-related bilateral pneumothorax

Abstract

Mechanical insufflation-exsufflation (MI-E) devices are frequently used in patients with respiratory muscle weakness to increase their cough peak flow and assist them in improving cough effectiveness and clearing mucus from the airways. An 89-year-old male was admitted to our university hospital due to fever and loss of appetite. He was diagnosed with lung abscess and pulmonary nontuberculous mycobacterial disease. He was unable to independently expectorate phlegm due to frailty. Subsequently, MI-E was introduced. On day 3 after its introduction, chest X-ray examination revealed bilateral pneumothorax, and use of the MI-E device was discontinued. After conservatively observing the clinical course, pneumothorax was improved on day 12 after it occurred. Although scientific evidence regarding MI-E is currently limited, healthcare professionals often do not have an alternative in clinical practice. However, treating physicians should consider the risk of MI-E-related pneumothorax, despite its low occurrence rate.

1. Introduction

Mechanical insufflation-exsufflation (MI-E) delivers a preset positive pressure into the airways for a set duration during inspiration (insufflation), immediately followed by an abrupt change to a preset negative exsufflation pressure, thus stimulating a cough with high expiratory flow rates [1]. This approach is frequently used, especially in patients with neuromuscular diseases (NMDs) or spinal cord injuries (SCIs), because their cough peak flow declines due to respiratory muscle weakness. These patients encounter difficulty in coughing and clearing mucus from the airways and lungs, increasing their risk of repeated respiratory infections. Consequently, MI-E devices are used to assist these patients in clearing airways mucus and reduce repeated infections or episodes of respiratory failure.

However, the currently available scientific evidence supporting the use of this method, including its safety profile, is insufficient [1,2]. Nevertheless, healthcare professionals are faced with the reality and the absence of alternatives, and opt to use this approach. Thus, the clinical usage MI-E devices continues to expand in patients with obstructive lung disease [3,4] or respiratory muscle weakness [4], mechanically ventilated critically ill patients [5], and those with an artificial airway [6].

Herein, we report the case of an elderly hospitalized male with lung abscess and pulmonary nontuberculous mycobacterial disease. Use of an MI-E device was initiated because of his inability to expectorate phlegm due to severely impaired activity of daily living (ADL) and muscle weakness. He experienced bilateral pneumothorax within a few days after the introduction of the MI-E. Although the pneumothorax was improved, the complication had a negative impact on his clinical course. Aging of the population worldwide will lead to an increase in the use of MI-E in various situations. Therefore, treating physicians should be aware of this potential complication.

2. Case report

An 89-year-old male was admitted to our university hospital due to fever and loss of appetite. Chest X-ray examination revealed an infiltration with a cavity in the right lower lung field, and the patient was hospitalized based on suspicion of lung abscess. He previously suffered from pulmonary tuberculosis, and presently has Alzheimer's dementia, diabetes mellitus, and lipid metabolism abnormality. He stopped smoking in his twenties. His physical examination findings are described below. His height and weight were 160 cm and 42.3 kg, respectively. Vital signs were a heart rate of 97 beats/min, respiratory rate of 17/min, SpO₂ of 98%, and body temperature of 36.2 °C. Course crackles were heard in his right lower lung field. A hemogram showed leukocytosis of 15.51 × 10³/μL, and the levels of C-reactive protein were elevated at 9.17 mg/dL, indicating inflammatory findings.

Chest X-ray examination revealed an infiltration with a cavity in the right lower lung field (Fig. 1a). Chest computed tomography showed consolidation with a cavity in the right lower lobe and background mild pulmonary fibrosis (Fig. 1b).

Fig. 1.

(a) Chest radiograph and (b) CT images at the initial medical examination.

CT, computed tomography.

The sputum smear was positive for acid-fast bacilli, and sputum polymerase chain reaction examination was positive for Mycobacterium intracellulare. Moreover, sputum culture revealed the presence of Methicillin-susceptible Staphylococcus aureus (MSSA). Therefore, he was diagnosed with pulmonary nontuberculous mycobacterial disease and lung abscess due to infection with MSSA. After hospitalization, intravenous meropenem was administered for 2 weeks to treat the lung abscess. Although the blood inflammatory reaction improved, a cavitary shadow persisted. Therefore, additional treatment with oral erythromycin was initiated due to the presence of Mycobacterium intracellulare.

On admission, the patient encountered difficulty in independently expectorating phlegm due to his general frail condition and low ADL. Therefore, an MI-E (CoughAssist® E70; Phillips Respironics, Inc., USA) was introduced with inspiratory and expiratory pressures of +20 cmH₂O and −20 cmH₂O, respectively. Although his symptoms and vital sign remained unchanged, on day 3 after the introduction of the MI-E, chest X-ray examination revealed a bilateral pneumothorax with a collapse rate of 17% (Fig. 2). Therefore, use of the MI-E device was discontinued. The airspace of the pneumothorax was small; thus, we selected a conservative therapy and observed the clinical course. On day 12 after occurred pneumothorax was improved, as shown through chest X-ray examination (Fig. 3).

Fig. 2.

Chest radiograph on day 3 after the introduction of MI-E, showing the presence of bilateral pneumothorax.

MI-E, mechanical insufflation-exsufflation.

Fig. 3.

Chest radiograph on day 12 after the occurrence of bilateral pneumothorax, showing improvement.

However, his general condition and ADL worsened, and oral ingestion became impossible. Aspiration pneumonia occurred and, eventually, he expired on day 60 following admission.

3. Discussion

The use of MI-E devices, especially in patients with NMDs or SCIs, or in intensive care units, increases in expectation of clearing airway secretions, reducing the occurrence of repeated airway infection, preventing atelectasis, assisting extubation, and lowering the rate of emergent admission. Recently, its use has expanded to patients with respiratory muscle weakness without NMDs or SCIs, despite the currently limited scientific evidence to support this application. In this report, we present a case in which use of MI-E induced a pneumothorax in a frail elderly patient with pulmonary infection. The risk associated with this method should be considered and assessed in clinical practice.

Interestingly, two case studies [7,8] reported pneumothorax associated with MI-E in patients with tetraplegia, Duchenne muscular dystrophy, and motor neuron disease, all of which are typical targets for the use of MI-E. In addition, noninvasive ventilation prior to the introduction of MI-E was used in all cases. Therefore, it is unknown whether the use of MI-E was responsible for the development of pneumothorax.

The present patient differed from the previously reported cases in that he did not have a NMD or SCI, and had not used noninvasive ventilation before MI-E. Thus, we showed for the first time that MI-E alone can cause pneumothorax in patients without NMDs or SCIs. In an aging society, the number of pneumonia cases in elderly individuals increase. Moreover, the respiratory muscle weakness of these patients may be severe due to frailty, rendering them unable to independently expectorate phlegm. Although the current scientific evidence does not support the extensive use of MI-E, healthcare professionals may have no alternative. Therefore, physicians should be aware of the risk for pneumothorax, an important potential adverse outcome that may seriously impact the clinical course.

The presence of bullous emphysema is regarded as a relative contraindication for the use of MI-E, because of its susceptibility to pneumothorax or pneumomediastinum. In the present case, despite the absence of bullous emphysema, pneumonia or frailty of the patient may have affected the MI-E. We should be aware that MI-E loads relatively higher pressures, possibly causing pneumothorax like positive pressure ventilation without MI-E. Regarding the setting of the device, it appears that insufflation/exsufflation pressures of +40 to −40 cmH₂O are the most commonly used. This range is preferred by patients and generates effective expiratory flows and volumes [8]. In the present case, we used a lower pressure setting. In general, the pressure setting should be adjusted depending on the condition of the patient and associated risks.

In addition, we would like to highlight a pitfall in team medicine in dealing with MI-E. In our case, although respiratory physicians ordered the use of MI-E, a rehabilitation physician decided the machine setting and physiotherapists used it on the spot. Sharing of information regarding the lung status and the machine setting may have been insufficient. Increased awareness regarding the risk of pneumothorax (based on the condition of the patient) and improved communication between the members of the medical team are warranted.

In conclusion, we should be aware of the risk of pneumothorax when using MI-E. In addition to scientific evidence, further discussions on the practical application, instruction, adverse effects, and team medicine concerning the use of MI-E are warranted to increase the benefit and reduce the risk.

Funding

None. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Appendix A. Supplementary data

The following is the supplementary data to this article: