How does posture affect vital capacity

In addition, previous studies have focused on psychological problems, such as subjective symptoms of physical problems and stress. However, to date, no study has reported on the effects of sitting posture on respiratory function while using a smartphone. The purpose of this study was to investigate the effect of different sitting postures on respiratory function and determine whether there are differences in changes between smartphone a group of smartphone users and a control group.

Our study was designed as a randomized control trial. The participants were divided into 2 groups. The control group spent time as they liked for 1 hour, and the smartphone group used a smartphone while in a sitting position for 1 hour.

The smartphone group subjects started the experiment in a comfortable position in which they held a smartphone with both hands and looked at the screen. When they started using the phone, they played a game. Four participants quit during the study control group, 3; smartphone group, 1 due to deterioration of their conditions.

Participants were excluded if they had spinal structure problems, neurological disorders, or respiratory dysfunctions e. All participants understood the purpose of the study, and informed written consent was obtained prior to enrollment. Our study was approved by the Institutional Review Board of Daegu University in accordance with the ethical guidelines established in the Declaration of Helsinki.

All participants sat on a stool and looked straight ahead. The best performance out of 3 tries was recorded as the FVC. Measurements were performed before and after the experiment. There were no differences between both groups in gender, age, height, or weight. There were initially 25 subjects in each group, but 4 participants were excluded due to deterioration of their conditions control group, 3; smartphone group, 1. In our study, we investigated the effect of using a smartphone while in different sitting postures on respiratory function.

These results suggest that a sitting posture while using a smartphone can reduce respiratory function. In the current study, the results of the smartphone group decreased significantly from 3. There are 2 possible causes of respiratory dysfunction. First, individuals using smartphones have been found to have reduced global and local muscle performance 8. It is believed that dysfunction of these muscles leads to reduced respiratory performance; this is mainly due to the common function of the sternocleidomastoid, trapezius, and scalene muscles in cervical movement and inspiration.

Additionally, weakness of the deep neck flexor and extensor muscles can lead to reduced stability of the cervical and thoracic spine, as well as changes in rib cage biomechanics These changes in rib cage biomechanics can also lead to associated changes of respiratory muscles by altering their force-length curves and force production abilities In the present study, a drop of 9.

Biomechanical alteration of postural alignment affects the ranges of motion, position, and coupling patterns of the articulations between the thoracic spinal vertebrae and ribcage, which influence lung compliance via changing articular movement available for breathing [ 19 ]. The diaphragm has several attachments to spinal vertebrae and ribcage and changes in the position of these bony structures altered the proper function of the diaphragm. Like other skeletal muscles in the body, the diaphragm contracts and relaxes in order to maintain proper breathing mechanics and also contributes significantly to spine stability and ribcage movement.

Restriction of the ribcage during slouched position limits the mobility of the diaphragm which subsequently and unconsciously induces breathing disorder [ 20 , 21 ]. In addition, slouched position contributes to impairment of other systems including reduced venous return, autonomic nervous system, and phrenic nerve excitability. Similar to our study, previous studies have reported an increased respiratory effort and reduced respiratory capacity and control in normal individuals in a slouched position compared to normal erect sitting position [ 20 , 22 , 23 ].

Facilitating a normal breathing pattern needs an effective diaphragm muscle contraction [ 21 ]. Adapting a slouched position reduces the ability of the diaphragm to generate appropriate force for contraction. This attributes to restriction imposed by the abdominal cavity. This is supported by a number of studies which demonstrated an alteration of the ribcage and the diaphragm strength force during different positions [ 1 , 21 , 24 ].

A study by Lee et al. Furthermore, Kera and Maruyama [ 24 ] and Lee et al. Moreover, using similar methods to our study, Costa et al. In the present study, the higher SNIP score in upright sitting position compared to slouched sitting position may be due the fact that in more upright position the diaphragm had a mechanical advantage and more favorable positions in the length-tension curve to create tension [ 3 ]. In addition, the length-tension relationship of all other inspiratory muscles may become altered in slouched sitting position to produce optimal muscle tension.

The present study demonstrated a little higher positive correlation between the SNIP score in upright sitting position and FEV 1 predicted values compared to the SNIP score in slouched sitting position. This is supported by a previous study that suggested better spirometry outcomes in the upright position than supine position in healthy individuals [ 25 ].

The present study demonstrated insignificant correlations among SNIP scores and the demographic variables such as age, height, weight, and BMI. However, a previous study reported that the demographic factors such as age, weight, BMI, and height influence the inspiratory muscle force in healthy individuals [ 26 ]. Several factors contributed to these differences. First, the possible reason is the different posture.

Second, in the current study, subjects were young where the effect of age on the diaphragm is unlikely. Third, the lack of correlations might be attributed to small sample size in the current study. The present study had some potential limitations. The result of the present study was limited to healthy young males.

The comparison of the lung function in different postures was not measured to document the effect of slouched position on lung volumes. In addition, the lack of comparative group limits the validity of the present study. Furthermore, quality trials investigating the effect of changing posture on respiratory muscle strength in patients with breathing disorders are recommended. Prolonged slouched position may induce breathing disorder and affect surrounding structures including the heart and phrenic nerve.

Individuals are advised to avoid slouched position and encouraged to practice upright position with proper breathing maneuvers. Future studies should look at the effect of reversing chronic slouched position on the diaphragm and lung volumes. This is an open access article distributed under the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Received 06 Nov Accepted 30 Jan Published 25 Feb Abstract Objective. Introduction Altered body position influences the respiratory muscle strength and function in both healthy adults [ 1 — 5 ] and patients with cardiopulmonary dysfunction [ 6 , 7 ].

Methods 2. Subjects A convenience sampling technique was used to recruit subjects from the College of Applied Medical Sciences. Figure 1. Figure 2. Variables Mean SD Age years Table 1. Table 2. Sniff nasal inspiratory pressure in different body positions. References R. Costa, N. Almeida, and F. Koulouris, D. Mulvey, C. Laroche, J. Goldstone, J. Moxham, and M. PEmax was higher in standing vs. RSL in patients with cystic fibrosis [ 47 ]. The differences were not clinically significant.

In healthy subjects, PImax was improved in sitting vs. However, other studies found no difference in PImax in sitting vs. In subjects with chronic SCI, no significant change was seen in PImax between sitting and supine, with the exception of a subgroup of patients with complete thoracic motor paresis where there was statistically and clinically significant improvement in sitting [ 37 ].

Seven studies evaluated the effect of body position on diffusion capacity; six included healthy subjects [ 18 , 20 , 21 , 24 , 56 , 57 ], three included patients with CHF [ 18 , 21 , 58 ], and one included COPD patients [ 57 ].

Among healthy subjects, two studies [ 24 , 56 ] found statistically and clinically significant improvement in DLCO in supine vs. One study [ 18 ] found DLCO to be higher in the sitting vs.

One study [ 21 ] reported higher DLCO in sitting vs. Three studies investigated diffusion capacity in patients with CHF [ 18 , 21 , 58 ]. One study [ 58 ] found that postural changes from the supine to sitting positions induced different responses in diffusion capacity. In some patients diffusion capacity improved in the sitting position and others showed no change or a decline. On the average no statistically significant difference was found between the two positions.

The authors attributed the difference in responses to variations in pulmonary circulation pressures. Another study [ 18 ] found no significant difference in diffusion capacity between the sitting and the supine positions.

Side-lying was reported to reduce DLCO in comparison to sitting in the third study [ 21 ]. Most studies in this systematic review of 43 papers evaluating the effect of body position on pulmonary function found that pulmonary function improved with more erect posture in both healthy subjects and those with lung disease, heart disease, neuromuscular diseases, and obesity.

In patients with SCI, the effect is more complex and depends on the severity and level of injury. In contrast, diffusion capacity, as assessed by DLCO, increases in the supine position in healthy subjects while the effect in CHF patients is thought to depend upon pulmonary circulation pressure.

Decreased FVC in more recumbent positions may reflect both increased thoracic blood volume due to gravitational facilitation of venous return, which is more important in patients with heart failure, as well as cephalic displacement of the diaphragm due to abdominal pressure in the recumbent positions, which is more important in obese subjects [ 59 ].

In side-lying positions, even though only the dependent hemi-diaphragm is displaced, the effect on FVC appears to be similar to that observed in a supine position [ 59 ]. Other factors that may contribute to lower FVC values in side-lying positions include increased airway resistance and decreased lung compliance secondary to anatomical differences between the left and right lungs, as well as shifting of the mediastinal structures [ 20 ]. FEV1 was also higher in erect positions.

Recumbent positions limit expiratory volumes and flow, which may reflect an increase in airway resistance, a decrease in elastic recoil of the lung, or decreased mechanical advantage of forced expiration, presumably affecting the large airways [ 20 ]. In asthmatic patients the increase in FVC while standing might be due to the increased diameter of the airways in this position [ 30 ].

In patients with CHF the lungs are stiff and heavy, and the heart is large and heavy, increasing the negative effects of lung-heart interdependence [ 60 ]. As cardiac dimension increases, lung volume, mechanical function, and diffusion capacity decrease [ 61 , 62 ]; thus, the heart weighs on the diaphragm while sitting and on one of the lungs while in a side-lying position.

This influences the ability of the lungs to expand laterally but allows the diaphragm to descend and the lungs to expand inferiorly. In side-lying positions, the heart weighs on one lung, compressing both the airways and lung parenchyma, leading to a reduction in FEV1 and FVC due to airway compression [ 21 ]. Both elastic reduced lung compliance and resistive loads are simultaneously increased in the supine position in CHF patients [ 63 ]. FVC is thus an important clinical tool for assessment of diaphragmatic weakness in patients with neuromuscular diseases [ 64 ].

In patients with ALS, supine FVC is a test of diaphragmatic weakness [ 65 ] that predicts orthopnea [ 25 ] and prognosis for survival [ 66 , 67 ]. The diaphragm increases its inspiratory excursion in the supine position because its muscle fibers are longer at end expiration, and they operate at a more effective point of their length-tension curve [ 69 , 70 , 71 ].

This mechanism is especially important in patients for whom the diaphragm is the main muscle for breathing, since their intercostal and abdominal muscles are inactive due to SCI.

FRC was reported to increase in upright positions in healthy subjects [ 27 , 43 , 53 ] and in patients with mild-to-moderate obesity [ 41 , 52 ].

Changing from a supine to an upright position increases FRC due to reduced pulmonary blood volume and the descent of the diaphragm.

This may change the point in which tidal breathing occurs in the volume-pressure curve, which leads to increased lung compliance, and thus an identical pressure change would produce a greater inspired volume if there is no change in respiratory drive [ 53 ]. In heart failure, reduction in lung compliance in the supine position might reduce the passive change in lung volume, but FRC may be sustained above relaxation volume by an adjustment in respiratory muscle or glottal activity [ 27 ].

Among patients with obesity the sitting FRC was less than in healthy subjects but there was no further decrease in the supine position [ 43 ]. PEF, PEmax, and PImax were found to increase in upright positions in healthy subjects [ 3 , 23 , 24 , 46 , 48 , 50 , 51 ] and in those with lung diseases [ 31 , 46 , 47 ].

This may be related to changes in lung volumes with positions. Standing and sitting have been shown to lead to the highest lung volumes [ 72 , 73 ]. At higher lung volumes the elastic recoil of the lungs and the chest wall is greater.

In addition, the expiratory muscles are at a more optimal region of the length-tension curve and thus are capable of generating higher intrathoracic pressure, potentially generating higher expiratory pressures and pushing air through narrow airways at high speed, which results in higher PEmax, PEF, and FEV1.

As lung volumes decrease, muscle length becomes less optimal, which results in lower PEmax in sitting, compared to the standing position, and even lower in more recumbent positions.

When standing, gravity pulls the mediastinal and abdominal structures down, creating more space in the thoracic cavity, which allows further expansion of the lungs and greater lung volumes [ 74 ].

This, along with the decrease in compression on the lung bases, allows alveoli to recruit and increases lung compliance. The inspiratory muscles can expand even more, which allows the diaphragm to continue contracting downwards, thus increasing lung volumes [ 46 ].

Sitting often leads to the somewhat reduced lung volumes compared with standing. This can be explained by several mechanisms. First, in sitting, abdominal organs are higher, interfering with diaphragmatic motion, thus enabling smaller inspiration. Second, the abdominal muscles are in a less optimal point in the length-tension curve, since the combination of hip flexion and higher position of the abdominal contents exert upward pressure.

Third, the back of the chair may limit thoracic expansion. Diaphragmatic strength is negatively affected by the supine position, and intrathoracic blood volume is increased.

The dependent hemi-diaphragm is stretched to a good length for tension generation, while the nondependent hemi-diaphragm is more flattened.

Changes in lung volumes may thus balance themselves out due to a better diaphragmatic contraction but decreased space in the thorax [ 46 ]. The decreased PImax observed in the supine position could be related to diaphragm overload by abdominal content displacement during maximal inspiratory effort, which could offset improved diaphragm position on the length-tension curve. In addition, the length of all other inspiratory muscles may become less optimal in supine position [ 75 ].

In patients with cervical spinal cord injury and high tetraplegia, PEF was found to be higher in the supine vs. In healthy subjects, most studies showed an increase in DLCO in supine vs. This improvement is attributed to the moderate increase in alveolar blood volume in the supine position due to recruitment of lung capillary bed on transition from upright to supine.

Age may attenuate this increase [ 76 ]. This may explain why a study that included participants with a mean age of 61 [ 21 ] found no difference in DLCO between sitting and supine.

Those effects caused reduction of diffusion capacity in the side-lying positions [ 21 ]. This might be related to reduced FVC and alveolar damage in these patients.

These effects might have negative impact on diffusion capacity, opposing the positive effect of the increase in blood volume in the alveoli [ 57 ]. The change in DLCO was probably related to the change in alveolar blood volume, most likely due to differences in pulmonary artery pressure and heart dimensions [ 58 ].

There are a few limitations to this review. First, the level of evidence of the studies is relatively low. However, in this type of research, due to the nature of the populations studied and the interventions applied, it is impossible to perform a randomized control study. Second, most studies were performed on a small number of subjects and all studies used either consecutive, convenience, or volunteer sampling. The review included only adult subjects and it is therefore not possible to generalize the results to children and adolescents.

Finally, research protocols varied between studies and detailed information about protocols were often missing. Patient cooperation during lung function testing strongly influences results. This may explain contradictory results obtained in some cases. Studies that included subjects older than 60 years did not mention the cognitive function of participants, a factor that may influence patient cooperation.

Further research in this field is needed, including studies designed to evaluate lung function in a larger number of healthy participants as well as in individuals with a variety of medical conditions.

There is also a need to use a standardized protocol including randomization of postures and times between tests e. When performing pulmonary function tests, body position plays a role in its influence over test results. As seen in this review, a change in body position may have varying implications depending on the patient populations. American Thoracic Society ATS guidelines [ 2 ] recommend performing PFTs in the sitting or standing position, but the sitting position is usually preferred.

The norms of those functions according to gender and age were established from tests performed in this position. This review suggests that for most of the subjects this is the preferred position for the test; however, clinicians should consider performing PFTs in other positions in selected patients.

In patients with SCI, testing also in the supine position may provide important information. In patients with neuromuscular disorders, performing PFTs in the supine position may help to assess diaphragmatic function. Positioning plays an important role in maximizing respiratory function when treating patients with various problems and diseases and it is important to know the implications of each position on the respiratory system of a specific patient.

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