Abstract
Purpose: Mechanically assisted coughing (MAC) is an airway clearance method in which the thorax/abdomen is compressed in synchronization with mechanical insufflation-exsufflation (MI-E). MAC can be performed with manual assistance at the upper thorax (MAC-UT), lower thorax (MAC-LT), and upper thorax + abdomen (MAC-UT/A). This study aimed to determine the most effective approach under different conditions (air stacking or tracheostomy) in patients with neuromuscular disorders (NMDs). Methods: The study included 34 patients with NMDs. The patients were categorized into air stacking group (n=15), no air stacking group (n=9), and tracheostomy/tracheostomy positive-pressure ventilation (TPPV) group (n=10). Results: In each group, the cough peak flow (CPF) at 75% of the forced vital capacity (V̇75), V̇50, V̇25, and V̇10 were investigated during the approaches. In the air stacking group, the CPF was higher with MAC-UT, MAC-LT, and MAC-UT/A than with MI-E (p < 0.05). Additionally, V̇75 was higher with MAC-LT and MAC-UT/A than with MI-E (p < 0.05 and p < 0.01, respectively). In the no air stacking group, V̇75 was higher with MAC-UT/A than with MI-E (p < 0.05). In the tracheotomy/TPPV group, there were no significant differences. Conclusions: MAC approaches, especially MAC-LT and MAC-UT/A, are preferred in air stacking patients. However, in tracheostomy/TPPV patients, the CPF might not increase with MAC.
Keywords: Mechanically assisted coughing, Mechanical insufflation-exsufflation, Cough peak flow, Neuromuscular disorders
Respiratory disorders in patients with neuromuscular disorders (NMDs) involve restrictive ventilatory impairment, owing to a decrease in vital capacity (VC) associated with a decrease in respiratory muscle strength and reductions in spinal column and thoracic movements1,2). Cough peak flow (CPF) reduces with decreases in respiratory muscle strength and VC. When airway secretions cannot be expectorated, atelectasis and respiratory infections can occur. These are considered major risk factors for acute respiratory failure3-5). CPF is an index of the ability to expectorate respiratory secretions. It is reported when an individual is aged ≥12 years and is expected to expectorate respiratory secretions and foreign bodies at CPF values >270 L/min with upper respiratory tract inflammation and perform effective aspiration at CPF values >160 L/min under normal circumstances6-10). When CPF values fall below these cutoff values, airway clearance is performed with manual cough assistance or mechanical insufflation-exsufflation (MI-E) to prevent respiratory infection and dyspnea7,11). Manual cough assistance involves pushing the upper abdomen or chest wall in synchrony with the individual's own coughing effort. MI-E is considered as the primary method for airway clearance12,13). MI-E simulates a cough by providing positive-pressure insufflation followed by negative-pressure exsufflation. MI-E is effective in NMDs, such as Duchenne muscular dystrophy (DMD) and amyotrophic lateral sclerosis (ALS)14-16). Some guidelines recommend MI-E for cough assistance in patients with NMDs17,18,25). Furthermore, it has been shown that MI-E results in the largest increase in CPF among all available approaches for cough assistance in patients with NMDs19). However, a study assessing the laryngeal reaction during MI-E reported laryngeal adduction at positive-pressure insufflation in ALS patients with symptomatic bulbar paralysis, which resulted in an ineffective CPF20). Patients with ALS who have symptomatic bulbar paralysis and clinically stable patients with mild respiratory dysfunction might not be appropriate candidates for cough assistance with MI-E21). Therefore, it has been suggested that the CPF with MI-E is affected by the symptoms of bulbar paralysis. MI-E with manual cough assistance (MAC) is a method to thrust the abdomen or the chest wall in synchrony with negative pressure exsufflation of MI-E. Kim et al. report that CPF was significantly higher with MAC than with MI-E22). This finding is similar to other findings in previous studies that showed an increase in CPF with the addition of manual assistance23,24). MAC can be performed with manual assistance at the upper thorax (MAC-UT), lower thorax (MAC-LT), and upper thorax plus abdomen (MAC-UT/A)25).
However, the position to manual assist the upper thorax, lower thorax, upper thorax, and abdomen to increase CPF is not clear.
The purpose of this study was to assess MI-E and the different MAC positions and determine the most effective approach under different medical management (air stacking or tracheostomy) in patients with NMDs.
Methods
Subjects
The study included 34 patients with NMD who were hospitalized in a hospital under the Akita National Hospital Organization and who routinely underwent MI-E (Table 1).
Table 1.
Characteristics in the air stacking, no air stacking, and tracheostomy/TPPV groups
| Air stacking group (n = 15) | No air stacking group (n = 9) | Tracheostomy/TPPV group (n = 10) | Total (n = 34) | |
|---|---|---|---|---|
| Median (maximum, minimum) | ||||
| Age, (years) | 38 (71, 23) | 60 (79, 49) | 64 (85, 30) | 54 (85, 23) |
| Height, (cm) | 156 (177, 140) | 164 (168, 150) | 155 (174, 150) | 158 (177, 140) |
| Weight, (kg) | 36 (62, 23) | 47 (70, 30) | 51 (72, 33) | 42 (72, 23) |
| Male/female, n | 13/2 | 7/2 | 2/8 | 21/13 |
| Period of hospital visits, (years) | 8 (30, 0) | 1 (4, 0) | 5 (13, 1) | 4 (30, 0) |
| Scoliosis, n | 6 | 0 | 1 | 7 |
| Ventilation method | ||||
| No assisted ventilation , n | 4 | 8 | 3 | 15 |
| NPPV, n | 11 | 1 | 12 | |
| TPPV, n | 7 | 7 | ||
| Respirator time, (h/day) | 10 (24, 0) | 0 (7, 0) | 24 (24, 0) | 10 (24, 0) |
| Diagnosis | ||||
| Duchenne muscular dystrophy, n | 12 | 0 | 0 | 12 |
| Amyotrophic lateral sclerosis, n | 2 | 1 | 3 | 6 |
| Myotonic dystrophy type 1, n | 1 | 6 | 1 | 8 |
| Limb-girdle muscular dystrophy, n | 0 | 0 | 1 | 1 |
| Oculopharyngeal muscular dystrophy, n | 0 | 0 | 1 | 1 |
| Polymyositis, n | 0 | 1 | 0 | 1 |
| Parkinson disease, n | 0 | 1 | 0 | 1 |
| Multiple system atrophy, n | 0 | 0 | 1 | 1 |
| Perry syndrome, n | 0 | 0 | 1 | 1 |
| Spinocerebellar degeneration, n | 0 | 0 | 1 | 1 |
| Lafora disease, n | 0 | 0 | 1 | 1 |
Patients with neuromuscular disorders of CPF <160 L/m or Assisted CPF <270 L/m were included. Patients with neuromuscular disorders that received treatment for MI-E for ≥1 year were included. The rationale for inclusion criteria is that the value of the adaptive CPF of MI-E is less than or equal to 160 L/min in normal condition and 270 L/min in upper respiratory inflammation7,11).
The exclusion criteria surmised that MI-E treatment was unnecessary, and the CPF value exceeded 270 L/min.
We explained clearly the purpose and method of the research in verbal and written form. However, patients who could not sign due to a decline in writing ability were also included. Therefore, I explained the study criteria to the patient's family clearly, both verbally and in writing, and gained consent for research.
This study was approved by the ethics committee of Akita National Hospital (IRB No. 27/2). Patients were included only after obtaining informed consent. Of the 34 patients, 12 had DMD, 6 had ALS, 8 had myotonic dystrophy type 1 (DM1), 1 had Parkinson disease, 1 had polymyositis, 1 had spinocerebellar degeneration, 1 had multiple system atrophy, 1 had Perry syndrome, 1 had oculopharyngeal muscular dystrophy, 1 had limb-girdle muscular dystrophy, and 1 had Lafora disease. Additionally, 16 patients did not receive assisted ventilation, 11 received noninvasive positive-pressure ventilation (NPPV), and 7 received tracheostomy/tracheostomy positive-pressure ventilation (TPPV).
Respiratory function assessment
VC was measured by connecting a facemask (Pacific Medico, Tokyo, Japan) to a simple spirometer for manual diagnosis (Hello Scale Light Respirometer, IMI)15,25).
Maximum insufflation capacity (MIC) is the maximum volume of air that can be accumulated in the lungs by air stacking. The measurement of the MIC sent forth the air which we saved by air stack and performed it in a simple spirometer connected to face mask. Air stacking requires closure of the glottis through laryngeal function, and if air stacking is not possible, MIC cannot be measured26,27). The definition of propriety of air stacking is based on whether MIC measurement is possible or impossible. When we were less than presence and the VC of the air leak from a simple spirometer for manual diagnosis, the findings of the MIC measurement indicated that air stacking was impossible at MIC measurement.
CPF-unassisted was measured with a peak flow meter (Philips Respironics, Murrysville, PA, USA), CPF-assisted was measured after manual cough assistance (chest and abdomen), and CPF-MIC was measured as the air stacked by a resuscitation bag28). CPF-MIC assisted was determined by assessing the air stacked by a resuscitation bag and the CPF during manual cough assistance with a peak flow meter (Table 2). Each variable was measured twice, and the maximum value was analyzed.
Table 2.
Approaches of the measurement of CPF
| CPF-unassisted | unassisted cough peak flow |
| CPF-assisted | CPF + manually-assisted coughing |
| CPF-MIC | maximum insufflation capacity + CPF |
| CPF-MIC assisted | MIC + manually-assisted coughing + CPF |
Measurement of MIC and CPF is not possible in individuals who cannot undergo air stacking. Measurement of VC and CPF is usually possible in those with tracheostomy/TPPV. However, not all participants in the present study could follow instructions. Therefore, VC and CPF could not be measured using this approach.
Measurement of the CPF by MI-E and MAC
We connected an MI-E device (Cough Assist E70, Philips Respironics) and an automatic spirometer (Autospiro AS507, Minato Medical Science Co., Osaka, Japan) for electronic diagnosis. The connection was made to analyze the effect of MI-E and MAC on the expiratory flow rate in detail. The detailed expiratory flow rate is CPF, expiratory flow rate at 75% of the forced vital capacity (V̇75), V̇50, V̇25, V̇10.
For the connection, a 1-m long tube was connected to the MI-E device, and then, the transducer of the automatic spirometer was connected. A mask was used in patients without tracheostomy, and a flex tube was used in patients with tracheostomy. Measurements were performed in the supine position by three physiotherapists (PT). The first PT applied the facemask or connected the flex tube to the tracheal cannula. The second PT performed manual cough assistance (thorax and abdomen) weakly. Position for manual assistance was as follows: MAC-UT, upper part of the sternum xiphoid prosess; MAC-LT, lower part of the sternum xiphoid process; and MAC-UT/A, upper thorax and diaphragm at the same time28). The timing of manual assistance was taken when shifting from the second positive pressure to the negative pressure, i.e., this timing is a patient's cough. It is difficult to quantify the compressive thoracic and abdominal synchronized with cough. However, it was compressed when MI-E shifted from positive pressure to negative pressure.
The third PT operated the automatic spirometer. Operation of the automatic spirometer involved activating the forced vital capacity (FVC) mode, pressing the start button at the end of the first expiration to start the measurement, and pressing the stop button after the second negative pressure to end the measurement. MI-E was set to ±40 cmH2O (1.5 s) in auto mode, and the rest time was set to 2 s in air stacking patients and tracheostomy/TPPV patients. In patients without air stacking, synchronization with positive pressure was not possible. On sensing inspiration, MI-E was initiated at ±40 cmH2O (1.5 s) in the synchronous function (cough track mode) with initial positive pressure. A pressure of 40 cmH2O has been recommended in adults and is often used in clinical settings12,13,29). The manual assistance in MAC involved MAC-UT, MAC-LT, and MAC-UT/A. Two consecutive positive and negative pressures were considered a single set.
Definition of an adequate break is that vital signs such as blood pressure and pulse are returned before intervention, and it was a break period of at least 3 minutes.
In patients who underwent tracheostomy/TPPV, the cuff pressure was adjusted within a range that prevented leakage and complications before measurement.
Statistical analysis
We considered the peak expiratory flow rate at 75% of the forced vital capacity (V̇75), V̇50, V̇25, and V̇10 from the flow-volume curve obtained with the FVC mode of the automatic spirometer and adopted the maximum value when measurements were performed twice. In addition, the displayed peak expiratory flow was CPF. A peak flow meter is widely used for the evaluation of CPF. Continual clinical evaluation of this variable is considered sufficient12). However, even though CPF is accurate at 270 L/min or more, it is overestimated at 270 L/min or less30).
On the contrary, an expiratory flow meter can identify a transient rise during the CPF process31). Thus, we adopted a flow-volume curve obtained using an automatic spirometer.
Considering the findings of the MIC measurement, the patients were categorized into an air stacking group, a no air stacking group, and a tracheotomy/TPPV group. In each group, we assessed the CPF, V̇75, V̇50, V̇25, and V̇10 during MI-E, MAC-UT, MAC-LT, and MAC-UT/A and compared the findings.
With regard to statistical analyses, the Kruskal-Wallis test was performed for non-normally distributed data, while the one-way analysis of variance was performed for normally distributed data. Regarding multiple comparisons, the Steel-Dwass method was performed for non-normally distributed data. All statistical analyses were performed using the Excel add-in software “Statcel3” (OMS Publishing Company, Tokyo, Japan). A probability value of <0.05 was considered statistically significant.
Results
Table 1 presents the characteristics of the air stacking, no air stacking, and tracheotomy/TPPV groups. The air stacking, no air stacking, and tracheotomy/TPPV groups included 15, 9, and 10 patients, respectively. There were many patients with ALS and DMD in the air stacking group, and there were many patients with adult-onset DM1 in the no air stacking group. On the contrary, in the tracheotomy/TPPV group, the types of NMDs were mixed. Patient age tended to be higher in the no air stacking group and tracheotomy/TPPV group than in the air stacking group. All patients had been hospitalized for ≥1 year, and the maximum period of hospitalization was around 10 years. VC and CPF tended to be higher in the no air stacking group than in the air stacking group.
Respiratory support, swallowing function, and activities of daily living
Table 3 presents information on respiratory support, swallowing function, and activities of daily living in the air stacking, no air stacking, and tracheotomy/TPPV groups. The Barthel index32), which was used to evaluate activities of daily living (ADL), tended to be lower in the tracheotomy/TPPV group than in the air stacking and no air stacking groups. The rate of scoliosis was high in the air stacking group, as this group included many patients with DMD. Scoliosis was considered as a Cobb angle above 10 degrees.
Table 3.
Characteristics of respiratory swallowing function, and activities of daily living in the air stacking, no air stacking, and tracheostomy/TPPV groups
| Air stacking group (n = 15) | No air stacking group (n = 9) | Tracheostomy/ TPPV group (n = 10) | Total (n = 34) | |
|---|---|---|---|---|
| CONUT: controlling nutritional status Median (maximum, minimum) | ||||
| Barthel index, score | 25 (45, 25) | 45 (50, 30) | 0 (20, 0) | 25 (50, 0) |
| VC, (mL) | 470 (1310, 150) | 1320 (2800, 340) | 0 | 370 (2800, 0) |
| MIC, (mL) | 1640 (2580, 600) | Unmeasurable | 0 | 1180 (2580, 0) |
| CPF, (L/min) | 75 (215, 0) | 120 (230, 80) | 0 | 68 (230, 0) |
| CPF-assisted, (L/min) | 120 (215, 50) | 105 (245, 0) | 0 | 83 (245, 0) |
| CPF-MIC, (L/min) | 170 (285, 100) | Unmeasurable | 0 | 130 (285, 0) |
| CPF-MIC-assisted, (L/min) | 225 (325, 115) | Unmeasurable | 0 | 155 (325, 0) |
| Albumin | 4 (4.4, 3.5) | 3.1 (3.6, 2.5) | 3.2 (4, 2.1) | 3.6 (4.4, 2.1) |
| Total cholesterol | 161 (210, 108) | 161 (207, 89) | 164 (208, 114) | 161 (210, 89) |
| Total lymphocyte count | 1808 (2518, 1129) | 1000 (2552, 661) | 1665 (4459, 770) | 1665 (4459, 661) |
| CONUT, score | 1 (0, 4) | 5 (9, 1) | 3 (9, 0) | 2 (9, 0) |
| Normal, n | 10 | 1 | 2 | 13 |
| Mild, n | 5 | 3 | 4 | 12 |
| Moderate, n | 0 | 4 | 3 | 7 |
| Severe, n | 0 | 1 | 1 | 2 |
| Swallowing function, n | ||||
| Ordinary, n | 7 | 1 | 0 | 8 |
| Dysphagic food, n | 8 | 8 | 0 | 16 |
| Tube feeding, n | 0 | 0 | 10 | 10 |
| CONUT: controlling nutritional status | ||||
| median (maximum, minimum) | ||||
We classified it by the food form that ate swallowing function every day. Food form assumes solidity in general diet; except it carved, and a blender, the soft meal did it with deglutition food, and did the subjects who could not ingest with tube feeding and a definition. Ordinary swallowing function was more common in the air stacking group than in no air stacking and tracheotomy/TPPV groups. Score the values of serum albumin, total cholesterol, total lymphocyte count. Based on the score, nutritional status was judged by controlling nutritional status(CONUT) evaluation method33). The Overall nutritional status is common among patients with a normal or mild disability. Patients who belong the no air stacking and tracheostomy/TPPV groups have many nutritional disorders of mild to moderate severity.
Comparison of respiratory function data among MI-E, MAC-UT, MAC-LT, and MAC-UT/A in the air stacking group
V̇75, V̇50, V̇25, and V̇10 values for MI-E, MAC-UT, MAC-LT, and MAC-UT/A in the air stacking group (n = 15) are presented in Table 4. The CPF was higher with MAC-UT, MAC-LT, and MAC-UT/A than with MI-E (p<0.05). Additionally, V̇75 was higher with MAC-LT and MAC-UT/A than with MI-E (p < 0.05 and < 0.01, respectively). There were no significant differences in V̇50, V̇25, and V̇10 among the approaches.
Table 4.
Comparison of respiratory function data among MI-E, MAC-UT, MAC-LT, and MAC-UT/A in the air stacking group (n = 15)
| CPF | V̇75 | V̇50 | V̇25 | V̇10 | |
|---|---|---|---|---|---|
| Median (maximum, minimum) *p<0.05, significant difference compared with MI-E **p<0.01, significant difference compared with MI-E | |||||
| MI-E, mean ± SD (L/min) | 182 (255, 97) | 115 (203, 62) | 82 (185, 36) | 80 (115, 31) | 77 (112, 41) |
| MAC-UT, mean ± SD (L/min) | 239 (311, 128)* | 202 (237, 64) | 106 (198, 55) | 86 (116, 35) | 82 (110, 29) |
| MAC-LT, mean ± SD (L/min) | 234 (298, 158)* | 194 (247, 82)* | 103 (190, 60) | 80 (106, 29) | 85 (113, 37) |
| MAC-UT/A, mean ± SD (L/min) | 248 (278, 145)* | 218 (247, 80)** | 89 (191, 48) | 77 (113, 35) | 80 (176, 27) |
Comparison of respiratory function data among MI-E, MAC-UT, MAC-LT, and MAC-UT/A in the no air stacking group
V̇75, V̇50, V̇25, and V̇10 values for MI-E, MAC-UT, MAC-LT, and MAC-UT/A in the no air stacking group (n = 9) are presented in Table 5. V̇75 was higher with MAC-UT/A than with MI-E (p < 0.05). There were no significant differences in the CPF, V̇50, V̇25, and V̇10 among the approaches. Additionally, from the point where the line graphs from CPF of MI-E to V̇75 suddenly dropped, the central airway resistance tended to increase.
Table 5.
Comparison of respiratory function data among MI-E, MAC-UT, MAC-LT, and MAC-UT/A in the no air stacking group (n = 9)
| CPF | V̇75 | V̇50 | V̇25 | V̇10 | |
|---|---|---|---|---|---|
| Median (maximum, minimum) *p<0.05, significant difference compared with MI-E | |||||
| MI-E, mean ± SD (L/min) | 198 (262, 108) | 74 (212, 51) | 66 (192, 19) | 70 (97, 37) | 56 (103, 19) |
| MAC-UT, mean ± SD (L/min) | 164 (280, 149) | 133 (215, 39) | 103 (202, 35) | 82 (112, 34) | 54 (98, 12) |
| MAC-LT, mean ± SD (L/min) | 230 (275, 151) | 106 (208, 94) | 105 (185, 40) | 68 (100, 28) | 56 (88, 20) |
| MAC-UT/A, mean ± SD (L/min) | 230 (275, 147) | 166 (247, 79)* | 99 (229, 64) | 83 (88, 34) | 59 (89, 29) |
Comparison of respiratory function data among MI-E, MAC-UT, MAC-LT, and MAC-UT/A in the tracheotomy/TPPV group
The CPF, V̇75, V̇50, V̇25, and V̇10 values for MI-E, MAC-UT, MAC-LT, and MAC-UT/A in the tracheotomy/TPPV group (n = 10) are presented in Table 6. There were no significant differences in the CPF, V̇75, V̇50, V̇25, and V̇10 among the approaches.
Table 6.
Comparison of respiratory function data among MI-E, MAC-UT, MAC-LT, and MAC-UT/A in the tracheotomy/TPPV group (n = 10)
| CPF | V̇75 | V̇50 | V̇25 | V̇10 | |
|---|---|---|---|---|---|
| Median (maximum, minimum) | |||||
| MI-E, mean ± SD (L/min) | 113 (135, 103) | 94 (113, 68) | 78 (94, 51) | 94 (104, 42) | 94 (112, 23) |
| MAC-UT, mean ± SD (L/min) | 112 (147, 90) | 82 (125, 53) | 85 (107, 45) | 94 (109, 46) | 97 (104, 44) |
| MAC-LT, mean ± SD (L/min) | 114 (134, 95) | 100 (123, 67) | 79 (115, 64) | 93 (103, 39) | 95 (109, 43) |
| MAC-UT/A, mean ± SD (L/min) | 116 (137, 96) | 107 (135, 67) | 82 (118, 54) | 92 (108, 47) | 96 (109, 6) |
Discussion
In the present study, on comparing MI-E, MAC-UT, MAC-LT, and MAC-UT/A, the air stacking group showed higher CPF and V̇75 with MAC than with MI-E, while the no air stacking group showed a higher V̇75 with MAC-UT/A than with MI-E. However, the tracheostomy/TPPV group showed no significant differences in any of the assessed variables among the approaches. We did not identify any significant differences among MAC-UT, MAC-LT, and MAC-UT/A on assessing these MAC approaches. Only the tidal volume and CPF are shown on the MI-E display. However, it is difficult to measure the exhalation flow rate with MI-E or MAC in detail. Therefore, we decided to measure the expiratory flow velocity using the flow volume curve of the automatic spirometer. In the flow volume curve, CPF and V̇75 indicate the state of airflow obstruction in the central airway, whereas V̇50, V̇25, and V̇10 indicate the state of airflow obstruction in the peripheral airway.
It is possible to visually determine the expiratory flow velocity with MI-E. Exploration of the presence or absence of synchronization and the presence or absence of airflow obstruction might be helpful. A peak flow meter is commonly used for CPF measurement. However, it is expected that there will be a measurement error between the CPF with the peak flow meter and the CPF on the MI-E display31). The findings of the present study will contribute to the development of CPF augmentation research. The CPF increased with MAC in the air stacking group. It was thought that the intrathoracic pressure increased by manual assertion of the state of high intrathoracic pressure owing to glottis closure and increased with negative pressure34,35). However, CPF did not increase in the no air stacking group. This might be because air stacking cannot be performed owing to decreased throat pharyngeal function. Thus, synchronization with the MI-E device cannot be achieved and intrathoracic pressure cannot be increased when switching to negative pressure. Therefore, it was impossible to obtain the beneficial effects of manual assistance. V̇75 indicates the state of the central airway. A significant increase in V̇75 indicates that a high expiratory flow rate was maintained for a long time. V̇75 increased significantly with MAC-LT and MAC-UT/A, and this might be associated with extensive movements of the lower thorax and abdomen. A previous study analyzed the motion of the thorax and abdomen during breathing in healthy subjects by using a three-dimensional motion analyzer and reported that movements of the lower thorax and abdomen were significant36). Thus, intrathoracic pressure and intraperitoneal pressure increased with manual assistance to the lower thorax and abdomen. Only V̇75 increased in the no air stacking group because glottal closure could not be achieved at the time when MI-E turned from positive pressure to negative pressure. In other words, an increase was noted by adding manual assistance to the optional cough at the V̇75 point over time from CPF to V̇75.
It is possible to explain this time lapse with cough acceleration, which has been a focus in recent years37,38). It is the ratio of the CPF of the flow waveform at the time of cough and the expiration rising time, reflecting vocal cord function. The expiration rising time is the time from the beginning of the expiratory phase to the CPF. Owing to the symptoms of bulbar paralysis, the expiration rising time increases, and it cannot be synchronized with the negative pressure of MI-E.
In the tracheostomy/TPPV group, MAC did not increase the CPF. This is because the intrathoracic pressure suddenly decreased because of the negative pressure of MI-E. Additionally, there was no statistically significant difference among MAC-UT, MAC-LT, and MAC-UT/A, and MAC did not show increases in V̇50, V̇25, and V̇10, which indicate the expiratory flow velocity of the peripheral airway. Thus, it was suggested that MI-E and MAC affected only the central airway. An important clinical finding of the present study is that patients with air stacking can show an increase in CPF or V̇75, which indicates the expiratory flow velocity of the central airway, regardless of the MAC position. However, CPF does not necessarily increase in patients who cannot undergo air stacking owing to spherical paralysis symptoms. However, in these patients, V̇75 might increase depending on the position of manual assistance.
In the tracheostomy/TPPV group, the effect of MAC on the expiratory flow rate was lower than that with MI-E. Training is important in patients with bulbar palsy symptoms who cannot undergo air stacking, as it can strengthen coughing. Dilatation pricked the air stack impossibility group with glottis, and the limit of this study turned out different when we entrusted negative pressure of MI-E. This resembles a method called huffing, which is a forced procedure, and it has been reported that huffing and coughing are not different with regard to airway clearance39).
Therefore, the glottis was dilated with positive pressure of MI-E in patients with no air stacking having bulbar palsy symptoms, and it might be possible to achieve CPF that is sufficient to perform huffing with negative pressure. In the present study, the setting of MI-E was ±40 cmH2O (1.5 s). However, the setting did not depend on the symptoms of the patients.
Synchronization for the negative pressure of MI-E might be difficult. There was an effect on the peripheral airway when the setting times for positive pressure and negative pressure were increased. Additionally, the compression position in MAC may be affected by the severity of scoliosis.
Conclusions
In patients with the ability for air stacking, a higher CPF was obtained with MAC approaches than with MI-E. Additionally, the CPF and peak expiratory flow associated with MAC positional differences increased with MAC-LT and MAC-UT/A. Thus, MAC approaches, especially MAC-LT and MAC-UT/A, are preferred in these patients. However, in tracheostomy/TPPV patients, the CPF might not increase with MAC approaches. The possibility of air stacking and the presence/absence of tracheotomy can affect MAC.
Conflict of Interest
The authors have no conflict of interest to disclose.
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