1 Introduction
Chronic obstructive pulmonary disease (COPD) directly affects the respiratory system. As the disease progresses, there is an increase in the work of breathing, abnormal ventilation, accumulation of air trapping, and dyspnea experienced by patients with COPD.[1,2] [3,4]
Pursed-lip breathing (PLB) is commonly used to improve ventilation and alleviate dyspnea[5,6] T ) and reduces respiratory rate (RR) in patients with COPD.[7–11] [7,8] AB ) and the total chest wall end-expiratory lung volume (EELV), and an increase in end-inspiratory lung volume of the ribcage (EILVRC ) compartment and the total chest wall (EILV). In contrast, patients who did not respond to PLB increased end-expiratory lung volume of ribcage compartment (EELVRC) , EELV, EILVRC , and EILVAB . As a result, their VT was significantly lower than that of the patients with a positive response to PLB. The decrease in EELV was also related to a decreased dyspnea score in patients with a positive response to PLB.[7] [8] [12]
A forward trunk lean posture (FTLP) is also a common strategy used to relieve dyspnea,[5,9,13] [14,15] [9] [16] [17,18] [19,20]
This study aimed to identify the effects of PLB, FTLP, and combined PLB and FTLP on total and compartmental lung volumes, and ventilation in patients with COPD. This study took advantage of the recent developments in OEP technology to overcome the technical difficulties associated with the previously used respiratory inductive plethysmography. The knowledge gained from this study will provide clinicians with rationales to support the use of these strategies to improve lung volume and ventilation in patients with mild to moderate COPD.
2 Material and methods
2.1 Design
This cross-sectional study with repeated measure design was approved by The Research Ethics Review Committee for Research Involving Human Research Participants, Health Sciences Group, Chulalongkorn University (Protocol number 031.1/61), and The Research Ethics Review Committee of The Central Chest Institute of Thailand. During screening sessions, participants were recruited using a convenience sampling method at The Central Chest Institute of Thailand. Demographic data collection and testing sessions occurred at the Department of Physical Therapy, Faculty of Allied Health Sciences, Chulalongkorn University. Each patient read and signed an informed consent form prior to participating in the study.
2.2 Participants
The sample size was calculated based on our pilot study results using ten subjects with COPD with the inclusion and exclusion criteria and research protocol similar to those used in this current study. The pilot study results indicated that the tidal volume of the pulmonary ribcage (VTRCp ) was greater during PLB-UP than in other tasks. VTRCp during PLB-FTLP was also found to be higher than quiet breathing (QB-UP and QB-FTLP). With a moderate effect size (ES=.65) of VTRCp based on the pilot study, a significance criterion of 0.05, and power of 0.80, the total sample size required for this study was determined to be 16.
Patients with COPD were included in this study if they were:
(1) diagnosed as mild to moderate COPD[21]
(2) clinically stable without exacerbation for at least 4 weeks before the screening test,
(3) with a mild to moderate dyspnea score (Medical Research Council dyspnea score = I-III),
(4) with a history of smoking, and
(5) without other conditions that prevented them from completing the study protocol.
Potential patients were excluded if they met 1 of the following criteria:
(1) having pain or discomfort, or had a history of chest wall operation,
(2) unable to perform the FTLP in sitting position, or
(3) receiving ventilatory support or long-term oxygen therapy.
The exclusion criteria allowed us to complete our data collection while minimizing confounding factors such as pain limiting chest wall movements and lung volume and maximizing patients’ comfort and safety during the data collection.
2.3 Intervention
During the preparatory session, the demographic data were collected. The level of dyspnea at baseline and during physical activity were assessed using a modified Borg scale score and the modified medical research council, respectively. Physical activity level was recorded using the Baecke physical activity questionnaire.
During the testing session, an OEP system was used to measure total and compartmental lung volumes and ventilation during 2 different body postures of self-selected upright posture (UP) and FTLP in a sitting position, and 2 breathing patterns of QB, and PLB. The FTLP was defined as a 45° anterior inclination of the trunk.[9,13,22] [23,24]
The combination of 2 breathing patterns (QB and PLB) and 2 body postures (UP and FTLP) allowed 4 testing tasks:
(1) QB with UP (QB-UP),
(2) PLB with UP (PLB-UP),
(3) QB with FTLP (QB-FTLP), and
(4) PLB with FTLP (PLB-FTLP) (Fig. 1 ).
Figure 1: Flow chart of patients.
The patients were asked to perform 3 trials of each testing task without speaking or coughing. Each trial lasted 1 minute. The resting period was 1 minute between trials, and 2 minutes between tasks or until dyspnea returned to the baseline.
2.4 Measurement and outcomes
An OEP system (BTS engineering, Milan, Italy) was used to capture chest wall movement by tracking 89 reflective markers placed on the patient's chest wall.[17] p , RCa , and AB (Fig. 2 ) as well as the total lung volume using Gauss theorem.[12]
Figure 2: Chest wall compartment divided by OEP: Pulmonary rib cage (RCp), Abdominal rib cage (RCa), and Abdomen (AB).
The outcomes related to lung volume were EELV, EILV, and VT . EELV and EILV consisted of 2 compartments of ribcage (EELVRC and EILVRC ) and abdomen (EELVAB and EILVAB ). VT had 3 compartments of pulmonary ribcage (VTRCp ), abdominal ribcage (VTRCa ), and tidal volume of abdomen (VTAB ). Ventilation-related outcomes were respiratory rate (RR), inspiratory time (Ti ), expiratory time (Te ), mean inspiratory flow (VT /Ti ), and mean expiratory flow (VT /Te ).
2.5 Data analysis
Demographic characteristics and outcome measurements are presented in mean±standard deviation (SD) for continuous data, and in percentage of sample size (%N) for categorical data. Two-way repeated measured analysis of variance (2 breathing patterns x 2 postures) was used to compare the effects of breathing patterns and body postures on outcome measures. Post-hoc analysis with Bonferroni adjustment was used to control for type I error during multiple comparisons. The significance level was set at .05. All data analysis was done using SPSS software version 22 (SPSS Inc., Chicago, Illinois).
3 Results
Table 1 describes the demographic data of the sixteen subjects. The effect of breathing patterns, postures, and their combinations on total and compartmental lung volume and ventilation are represented in Tables 2–4 .
Table 1 -
Demographic characteristics of the 16 patients with COPD.
Characteristics
Mean ± SD
% (N)
Age (yr)
63.69 ± 6.34
Weight (kg)
63.05 ± 9.47
Height (m)
1.67 ± 0.06
BMI (kg/m2 )
22.73 ± 3.1
FEV1 (%)
73.13 ± 18.64
FEV1 (L)
1.88 ± 0.46
FVC (L)
3.24 ± 0.63
FEV1 /FVC (%)
60.81 ± 11.38
Stage of COPD
- Mild
31.25% (5)
- Moderate
68.75% (11)
Year of COPD (yr)
5.69 ± 5.5
Smoking (Pack-Year)
39 ± 13.52
Co-morbidity
- Cardiac disease
18.75% (3)
- Metabolic disease
56.25% (9)
- Musculoskeletal disorder
25% (4)
Dyspnea level
- MMRC score
1.19 ± 0.4
- Modified Borg scale
0 ± 0
Physical activity level (Baecke physical activity)
7.64 ± 1.34
- Sedentary
0% (0)
- Active
56.25% (9)
- Athlete
43.75% (7)
Data expressed as mean and standard deviation (SD).BMI = body mass index, COPD = chronic obstructive pulmonary disease, FEV1 % = Percentage of force expiratory volumes in 1 second, MMRC = modified medical research council dyspnea score.
Table 2 -
Main effect of breathing pattern and body posture on lung volume.
Breathing Pattern
Body Posture
Parameters
QB
PLB
Effect size
P -value
Up
FTLP
Effect size
P -value
EELVAB (L)
7.53 ± 1.87
7.31 ± 1.83
3.01
<.001∗
7.26 ± 1.86
7.58 ± 1.86
2.18
.001#
EELV (L)
22.71 ± 3.64
22.41 ± 3.55
2.19
.001∗
22.26 ± 3.63
22.86 ± 3.56
2.77
>.001#
EILVAB (L)
7.86 ± 1.91
8.22 ± 2.02
3.67
<.001∗
7.93 ± 2.04
8.15 ± 1.89
1.59
.008#
VTRCp (L)
0.16 ± 0.12
0.46 ± 0.2
4.28
<.001∗
0.33 ± 0.16
0.29 ± 0.14
1.17
.038#
VTAB (L)
0.33 ± 0.09
0.92 ± 0.26
5.37
<.001∗
0.67 ± 0.23
0.58 ± 0.12
1.13
.045#
Data expressed as mean and standard deviation. Quiet breathing (QB); Pursed-lip breathing (PLB); Tidal volume (VT); End-expiratory lung volume (EELV); End-inspiratory lung volume (EILV); Pulmonary ribcage (RCp); Abdominal ribcage (RCa); Ribcage (RC); Abdomen (AB); liter (L); Upright (UP); Forward trunk lean posture (FTLP).
∗ Significant of main effect of breathing pattern.
# Significant of main effect of body posture.
Table 3 -
Combined effects of breathing pattern and body posture on ventilation.
Upright Posture
FTLP
Parameters
QB (a)
PLB (b)
QB (c)
PLB (d)
P -value
Ti (s)
1.33 ± 0.45
2.58 ± 0.99
1.36 ± 0.48
2.49 ± 1.05
.490
Te (s)
2.11 ± 0.5
5.21 ± 4.41
2.21 ± 0.7
4.79 ± 3.69
.081
RR (bpm)
18.4 ± 3.72
9.48 ± 3.23
17.95 ± 4.11
10.11 ± 3.57
.252
VT /Ti (L/s)
0.41 ± 0.18
0.76 ± 0.26
0.26 ± 0.29
0.68 ± 0.24
.432
VT /Te (L/s)
0.31 ± 0.1
0.44 ± 0.17
0.27 ± 0.1
0.4 ± 0.16
.971
Data expressed as mean and standard deviation. Upright (Up); Forward trunk lean posture (FTLP); Quiet breathing (QB); Pursed-lip breathing (PLB); Inspiratory time (Ti); Expiratory time (Te); Second (s); Respiratory rate (RR); breath per minute (bpm); Mean inspiratory flow (VT/Ti); Mean expiratory flow (VT/Te); ratio of liters per second (L/s).
Table 4 -
Main effect of breathing pattern and posture on ventilation.
Breathing Pattern
Body Posture
Parameters
QB
PLB
Effect size
P -value
Up
FTL
Effect size
P -value
Ti (s)
1.34 ± 0.4
2.54 ± 1
2.46
<.001∗
1.96 ± 0.62
1.92 ± 0.57
0.20
.701
Te (s)
2.16 ± 0.54
5 ± 4.04
1.50
.011∗
3.66 ± 2.29
3.5 ± 1.97
0.56
.294
RR (bpm)
18.17 ± 3.62
9.8 ± 3.28
4.18
<.001∗
13.94 ± 2.76
14.03 ± 3.02
0.11
.830
VT /Ti (L/s)
0.34 ± 0.19
0.72 ± 0.24
4.04
<.001∗
0.59 ± 0.19
0.47 ± 0.23
1.42
.015#
VT /Te (L/s)
0.29 ± 0.09
0.42 ± 0.16
2.31
<.001∗
0.37 ± 0.12
0.34 ± 0.11
0.99
.073
Data expressed as mean and standard deviation. Quiet breathing (QB); Pursed-lip breathing (PLB); Inspiratory time (Ti); Expiratory time (Te); Second (s); Respiratory rate (RR); breath per minute (bpm); Mean inspiratory flow (VT/Ti); Mean expiratory flow (VT/Te); ratio of liters per second (L/s).
∗ Significant of main effect of breathing pattern.
# Significant of main effect of body posture.
EELV and EELVAB were significantly lower during PLB as compared to QB (P < .01), and during UP as compared to FTLP (P < .01) (Table 2 ). EELVRC was significantly lower during PLB-UP as compared to PLB-FTLP and QB-FTLP (P < .05, ES = 1.16) and during QB-UP as compared to QB-FTLP (P = .04) (Fig. 3 ).
Figure 3: End-expiratory lung volume and its compartment during performed breathing patterns and postures. Upright (Up); Forward trunk lean posture (FTLP); Quiet breathing (QB); Pursed-lip breathing (PLB); End-expiratory lung volume (EELV); Ribcage (RC); Abdomen (AB). ∗ significance interaction effect of breathing patterns and postures at P < .05; # significance main effect of breathing patterns at P < .05; ## significance main effect of body postures at P < .05.
EILVAB was significantly greater during PLB as compared to QB (P < .001), and during FTLP as compared to UP (P = .008) (Table 2 ). EILV and EILVRC were significantly greater during PLB-UP and PLB-FTLP than those with QB-UP and QB-FTLP (P < .01; Fig. 4 ). The effect sizes of these comparisons were large (ES = 1.55–2.51).
Figure 4: End-inspiratory lung volume and its compartment during performed breathing patterns and postures. Upright (Up); Forward trunk lean posture (FTLP); Quiet breathing (QB); Pursed-lip breathing (PLB); End-inspiratory lung volume (EILV); Ribcage (RC); Abdomen (AB). ∗ significance interaction effect of breathing patterns and postures at P < .05; # significance main effect of breathing patterns at P < .05; ## significance main effect of body postures at P < .05.
VTAB and VTRCp were significantly greater during PLB than QB (P < .001), and greater during UP than FTLP (P < .05) (Table 2 ). Additionally, VT and VTRCa were significantly greater for PLB-UP as compared to other positions (P < .05; Fig. 5 ). The effect size ranged from 1.48 to 2.36.
Figure 5: Tidal volume and its compartment during performed breathing patterns and postures. Upright (Up); Forward trunk lean posture (FTLP); Quiet breathing (QB); Pursed-lip breathing (PLB); Tidal volume (VT); Pulmonary ribcage (RCp); Abdominal ribcage (RCa); Ribcage (RC); Abdomen (AB). ∗ significance interaction effect of breathing patterns and postures at P < .05; # significance main effect of breathing patterns at P < .05; ## significance main effect of body postures at P < .05.
Ti , Te , RR, VT /Ti , and VT /Te were significantly greater during PLB than QB (P < .05; Table 4 ). Additionally, VT /Ti was significantly greater during UP as compared to FTLP (P = .01; Table 4 ). There was no significant combined effect of breathing patterns and body postures on all ventilation parameters (P >.05; Table 3 ).
4 Discussions
This study described and compared the effect of PLB, FTLP, and combined PLB-FTLP on total and compartmental lung volumes and ventilation in patients with mild to moderate COPD. Significant changes in EELVAB , EELV, EILVAB , VTRCp , VTAB , and all ventilation parameters were demonstrated with PLB compared to QB. UP significantly increased VTRCp , VTAB , and VT /Ti as compared to FTLP. However, EELVAB , EELV, and EILVAB were significantly increased during FTLP as compared to UP. The combined PLB-UP significantly lowered EELVRC as compared to QB-UP and compared to both breathing patterns with FTLP. The combined PLB-FTLP and PLB-UP each demonstrated significantly higher EILV and EILVRC than those observed during QB-FTLP and QB-UP. Additionally, PLB-UP demonstrated significantly greater VTRCa and VT as compared to other testing tasks.
Our results are consistent with previous studies where PLB-UP was found to positively impact total (VT ), 2 compartmental (VTRC , VTAB ) lung volumes and ventilation (RR, Ti , Te , VT /Ti ) as compared to QB.[7–9,11] [25,26] e results in a decrease in RR and an increase in VT /Te .[24] T , compartmental volumes, and all ventilation parameters during PLB. Additionally, our study demonstrates that, during PLB, VTAB has the largest contribution to the VT, followed by VTRCp and VTRCa . Since the changes in VTAB and VTRCp are closely related to diaphragmatic function[27] [16] [28]
The decreased EELV and EELVAB and increased EILV and EILVRC during PLB-UP observed in our results are similar to those previously reported in patients with severe COPD.[7] [7] AB were associated with a longer Te and an increase of tidal volume. As a result, the patients who responded positively to PLB had relatively lower air trapping and experienced less dyspnea with PLB.[7]
The severity of lung hyperinflation impacts the effectiveness of PLB on lung volume in patients at different stages of COPD.[7] [29] [30] 1 decreased.[29]
Positive changes in EILV and EILVRC were noted during PLB-FTLP. PLB promotes a reduction of EELV and longer Te , while FTLP has a positive effect on respiratory muscles and increased EILVRC .[9] AB , EELV, and EILVAB were observed during FTLP compared to upright posture. During FTLP, gravity pulls the abdominal wall forward, resulting in lengthening of abdominal muscles,[15] [15] [15] [15]
There was no significant impact found from either UP or FTLP on any ventilation parameters except VT /Ti . The changes in VT /Ti may have occurred due to a greater increase in VT /Ti during UP posture than during FTLP. For the other ventilation parameters, our results were consistent with previous studies.[9,15] T and ventilation during performed FTLP as compared to upright posture.[9,15]
In this study, the combined effect of PLB-UP and PLB-FTLP resulted in positive changes in the compartmental and total lung volumes of EELVRC , EILVRC , EILV, VTRCa , and VT as compared to those with QB. Our positive combined effect of PLB-UP and PLB-FTLP contradicts the non-significant interaction effect between body postures and breathing patterns on VT and RR in patients with moderate COPD previously reported.[9] T and RR were positively changed during PLB compared to QB, regardless of the body posture.[9] [9] T and positively changed lung volumes compared to all other testing tasks. The ability to detect small but significant changes in compartmental lung volumes in our study is most likely due to the advantages provided by the OEP. Based on our results, PLB-UP and PLB-FTLP should be used in pulmonary rehabilitation programs to improve total and compartmental lung volumes in patients with mild to moderate COPD.
4.1 Limitations
Firstly, our patients were mild to moderate COPD and quite active, as indicated by their activity level and self-reported non-significant dyspnea prior to and during the testing tasks. Therefore, our results apply to patients with minimal dyspnea related to COPD. Secondly, this study did not focus on the effect of interventions on the activities of the chest wall and trunk muscles. In contrast, our study infers the functions of the involved muscles based on the changes of compartmental lung volumes. Adding a direct method of electromyography (EMG) to an OEP should provide a clearer picture of these breathing patterns and body postures in patients with COPD. Lastly, our study sample size is relatively small and has a combination of patients with mild and moderate COPD. Due to this small sample size, the results of this study should be considered preliminary, and further studies will be needed to confirm its results. Additionally, this small sample size also limited our ability to perform sub-group analysis. Further studies with a larger sample size and separate groups of patients with mild and moderate COPD are needed to confirm the effect of PLB, FTLP, and combined strategies.
4.2 Clinical Implications
PLB is an effective strategy for positively changing the total and compartmental lung volumes and ventilation in patients with mild to moderate COPD. It can be used in combination with UP or FTLP since there was no significant difference observed between these 2 postures. During FTLP, PLB is be recommended over QB since it significantly and positively due to its significantly greater positive change in the total and compartmental lung volumes.
In conclusion, a combination of PLB with UP or FTLP demonstrates a positive change in the total and compartmental lung volumes in patients with mild to moderate COPD. In these patients, PLB is more beneficial than QB in improving ventilation. Further studies with subgroup analyses and a relatively larger sample size are needed to confirm these effects in patients with specific stages of COPD. Additional measurements of lung hyperinflation and muscle activity during PLB and FTLP will further elucidate the effect of these strategies in patients with different stages of COPD.
Author contributions
Conceptualization: Nutsupa Ubolnuar, Anong Tantisuwat, Premtip Thaveeratitham, Witaya Mathiyakom.
Data curation: Nutsupa Ubolnuar, Anong Tantisuwat, Chathipat Kruapanich, Jaturong Chimpalee.
Formal analysis: Nutsupa Ubolnuar, Anong Tantisuwat, Somrat Lertmaharit.
Funding acquisition: Nutsupa Ubolnuar, Anong Tantisuwat.
Investigation: Nutsupa Ubolnuar, Anong Tantisuwat.
Methodology: Nutsupa Ubolnuar, Anong Tantisuwat.
Project administration: Anong Tantisuwat.
Supervision: Anong Tantisuwat, Premtip Thaveeratitham, Somrat Lertmaharit, Witaya Mathiyakom.
Validation: Nutsupa Ubolnuar, Anong Tantisuwat, Witaya Mathiyakom.
Visualization: Witaya Mathiyakom.
Writing – original draft: Nutsupa Ubolnuar.
Writing – review & editing: Anong Tantisuwat, Premtip Thaveeratitham, Witaya Mathiyakom.
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