Effect of 10 cm Loaded Inspiratory Training when Compared to 20 cm Loaded Training in Controlling Hypertension

Introduction

Hypertension is the most common non-communicable disease in India.¹ Globally, hypertension is responsible for 7.1 million deaths (12.8 percent of total deaths) and 64.3 million disability-adjusted life years (DALYs) (4.4 percent of global total DALYs), with a prevalence of 972 million in 2002 and a predicted increase of 60 percent (1.56 billion) by 2025.² In India, hypertension is to blame for 57% of all stroke deaths and 24% of all coronary heart disease deaths.³ Even in the normotensive range, there is a strong positive and persistent correlation between blood pressure and the risk of cardiovascular disease (stroke, myocardial infarction, and heart failure), renal disease, and mortality. This relationship is stronger with systolic blood pressure than with diastolic blood pressure.⁴

In all patients with chronic hypertension and a vast majority of patients with labile hypertension, nondrug therapeutic treatment is likely to be helpful. Stress reduction, dietary management, routine aerobic exercise, weight loss (if needed), and monitoring of other risk factors that contribute to the development of arteriosclerosis are among the general measures used.⁵

Whole-body exercise is often prescribed as a key factor of hypertension management. Cycling, jogging, aerobic exercise, and dance may be relevant to younger urban patients; however, for a variety of practical and cultural reasons, these activities may not be appropriate for older, poorer, and rural patients. Breathing exercises have been found to aid in the regulation of increased blood pressure. Blood pressure has also been found to be reduced by yoga training that emphasizes on gradual and regular breathing.⁶ One of the most popular commercially available devices for breathing retraining is RESPE Rate, which prioritizes the regulation of expiration.⁷

It is possible that any type of regulated slow breathing rate will be enough to lower diastolic blood pressure. Unnecessarily high sympathetic nervous outflow from the central nervous system is considered to be a key factor in the pathophysiology of acute and chronic hypertension, since it stimulates an increase in cardiac output and peripheral resistance. Desensitization of arterial and cardiopulmonary baroreceptors is frequently accompanied with increased sympathetic activity, resulting in greater BP fluctuation and persistent spikes in resting pressures.⁸

Slow breathing (less than 10 breaths per minute), particularly with prolonged exhalation, tends to decrease sympathetic nerve traffic, resulting in arteriolar dilation. Activated pulmonary mechanoreceptors, which respond to an increase in tidal volume associated with slow breathing and operate in concert with cardiac mechanoreceptors to block sympathetic outflow, are thought to begin this process. However, as seen by the wide variation in the ratio of inspiratory to expiratory periods during breathing training with RESPE Rate, this device directed breathing rate but did not necessarily control the depth of inspiration.⁷

After eight weeks of home-based loaded inspiratory training with a threshold breathing apparatus, Chulee et al.,⁹ discovered that both systolic and diastolic blood pressures were reduced. The author predicted that breathing exercise reduced resting systolic and diastolic blood pressure as well as heart rate, with one potential mechanism of action being that the training increased cardiac vagal tone and lowered sympathetic activity to the cardiac and peripheral arterioles. Sympathetic excitation has also been found to be reduced by resistive slow deep breathing at high tidal volumes. An increase in baroreflex sensitivity is another possible mechanism of action for the reduction in hypertension caused by baroreflex-cardiac sensitivity. An increase in baroreflex sensitivity is thought to mediate the effects of slow deep breathing on blood pressure. Loaded breathing has been found to enhance the aortic baroreflex as a result of higher negative intrathoracic pressures. It is possible that the greater systolic blood pressure response observed with loaded slow deep breathing is related to the load magnifying of some of the processes mentioned previously.⁹

Interestingly, the author utilized a water load of 20 cm in a previous research. However, it is uncertain if a lower water load of 10 cm will have comparable effects in these individuals. It was also hard to predict how many times patients should exercise because it was unclear how long the benefits would persist once the training was done. As a result, there is a need to establish the long-term efficacy of 10 cm load versus 20 cm load in managing hypertension. Therefore, the objective of the present study was to compare the effect of 10 cm loaded inspiratory training with that of 20 cm loaded inspiratory training in reducing hypertension.

Materials and Methods

A pre-post experimental study was performed on 30 subjects from KTG hospital, Bangalore. Subjects with essential hypertension stage I or II (systolic blood pressure 140–179, diastolic blood pressure 90–109 mm of Hg) based on guidelines of JNC-VII,¹⁰ aged 35–65 years with good comprehension and communication, independent ambulation were included. If a subject had a history of secondary hypertension, respiratory disease, diabetes mellitus, cardiac, renal, or cerebrovascular disease, dyslipidemia, or pregnancy during the previous six months, they were excluded from the study.

The subjects were included in the study after receiving ethical approval from the Ethical Committee and after considering the inclusion and exclusion criteria stated before. Subjects with essential hypertension stage I or II were recruited from the Outpatient Department. Subjects were randomly allocated to one of two groups (Group A or Group B) after an initial evaluation using the block randomization approach. Group A underwent inspiratory loaded training with a depth of 20 centimeter of water, whereas Group B received inspiratory loaded training with a depth of 10 centimeter of water.

The loaded inspiratory muscle training was introduced to the subjects one week before the study. For training, the patients used a customized simple loaded breathing device, the Water Pressure Threshold Bottle (Figure 1). A one liter plastic bottle (used mineral water bottle) with two tubes going through the lid served as the device. One shorter tube comes out through an outlet through the bottle’s top and patients inspire through this tube, while the other tube is a longer adjustable intake tube passing into the water. The inspiratory resistance was therefore defined by the displaced column of water, which was set by the length of the inlet tube below the water level in the cylinder (Figure 2). The water level in Group A was set at 20 cm, while the water level in Group B was set at 10 cm. The device is basic to use and adjust. It has the extra benefit of humidifying the inspired air, and the bubbling sound works as feedback, assisting in the establishment of a consistent breathing pattern.⁹ Subject had to inspire through shorter tube and exhale through nose as shown in figure 2.

The subjects were asked to follow a breathing pattern that included regulated flow rate of about 200 mL/ sec, a 4-second inspiratory duration, and a 10-second total respiratory time. The subjects were instructed to perform the training at home in two 30-minute sessions each day for a total of three weeks. Blood pressure (both systolic and diastolic) was monitored at three points: before the intervention, after three weeks, and a follow up after another three weeks.

SPSS (version 17) for Windows was used to analyze the data. The value of Alpha was set to 0.05. The mean, standard deviation, and range of demographic and outcome data were determined using descriptive statistics. The homogeneity of baseline data for demographic and outcome variables was determined using an unpaired t test. The Chi square test was used to see if there were any gender differences between the two groups. To find out if there were any significant differences in blood pressure within the groups, repeated measure ANOVA was used. The unpaired t test was used to see if there were any significant differences in blood pressure between the groups.

Results

Table 1 shows the baseline characteristics of 30 subjects. Prior to the study, baseline data for demographic characteristics such as age, gender, weight, height, and BMI were homogeneous, but baseline data for duration and medicines were not. At baseline, no significant difference in systolic and diastolic blood pressure was detected between the two groups (Table 2). After six weeks of loaded training, both the groups demonstrated statistically significant reductions in blood pressure. On comparing the two groups, both were equally effective in lowering blood pressure after the third and sixth week of training (table 2).

Discussion

The objective of the present study was to compare the effects of 10 centimeter compared to 20 centimeter loaded inspiratory training in reducing blood pressure. The baseline data of the demographic and outcome variables were not statistically different between patient population in both the groups except medication and duration. All the patients in both the groups were able to complete the study.

The subjects in this study used a novel basic loaded breathing apparatus, the Water Pressure Threshold Bottle, which comprises of a plastic bottle with two tubes flowing through the cap, to train their inspiratory muscles. This instrument was used in accordance with the approach suggested by Chulee et al.⁹

The result in group A showed that the mean systolic blood pressure reduced from 141.07 to 137.73 after three weeks which again further reduced to mean of 132.93 which was statistically significant. Similarly, the mean pre diastolic blood pressure of 88.93 reduced to mean post diastolic blood pressure of 87.07 after three weeks which further reduced to mean of 83.87 which was statistically significant in accordance to the study conducted by Mahtani et al.¹¹ Schein et al. found that short-term usage of device guided breathing can lower both systolic and diastolic blood pressure.¹² During two months of self-treatment by subjects at home, the device was found to be effective in lowering high blood pressure. Modification of breathing patterns appears to be a key factor in this decrease.

In group B, the mean pre systolic blood pressure of 140.53 reduced to mean post systolic blood pressure of 138.27 after three weeks which again reduced to mean of 135.73 which was statistically significant. Likewise, mean pre diastolic blood pressure of 89.60 reduced to mean post diastolic blood pressure of 87.87 after three weeks which further reduced to mean of 86.40 which was statistically significant in accordance to the study performed by Chulee U Jones et al. Patients were well tolerated with home training device and their blood pressure was reduced.⁹

The results of both groups A and B were statistically significant. This might be due to lung expansion, which increases when breathing rate reduces, further stimulating the slowly adapting pulmonary stretch receptors. This neuronal activity is transmitted into the medulla, where it is combined with information regarding blood pressure generated by arterial baroreceptors. Heart rate is reduced as an immediate reaction to BP rise and/or lung inflation, and vasodilation occurs in a variety of vascular regions, including the limbs, skin, muscles, kidney, and splanchnic vascular bed.^12,13

Results did not show any statistical significant difference between group A and group B after three weeks of training. The mean systolic blood pressure was 137.73 and 138.27 in Group A and Group B respectively, which were not statistically significant. In group A, the mean diastolic blood pressure was 87.07 and in group B, mean diastolic blood pressure was 87.87 which were not statistically significant.

Results did not show any statistical significant difference between group A and group B after six weeks of training either. The mean systolic blood pressure was 132.93 in Group A and 135.73 in Group B, which was not statistically significant. The mean diastolic blood pressure was 83.87 and 86.40 in Group A and Group B respectively, which were not statistically significant. This statistical insignificance could be due to difference in duration of medications given for both the groups as this was not homogenous between the groups before the  study.

Before the study, the onset of hypertension differed between the groups, with group A having a longer duration of hypertension than group B. Another factor for the obtained output might be the shorter training period. Six weeks of training may not be enough to produce results with high loaded training. Other factors that might have impacted the outcome include the type of drugs provided to the subjects, the psychological effects of breathing training, such as impact on relaxation, and the level of physical activity, which was not tracked in this study.

Further research can be done with a larger sample size and a longer follow-up period. Similar studies may be conducted on those who have secondary hypertension and in comparison with level of physical activity.

Conclusion

The objective of the present study was to assess how 10 cm loaded inspiratory training compares to 20 cm loaded training in terms of controlling hypertension. Both 10 centimeter and 20 centimeter loaded inspiratory training were equally efficient in controlling essential hypertension. However, six weeks of training was insufficient to distinguish between different types of loaded training in terms of hypertension control.