Impact of Impaired Inspiratory Muscle Strength onDyspnea and Walking Capacity in Sarcoidosis

Hans-Joachim Kabitz, Felix Lang, Stephan Walterspracher, Stephan Sorichter, Joachim Muller-Quernheim, and Wolfram Windsch

Chest 2006 Nov; 130 (5). Pp1496-1502 Abstract:

BACKGROUND: Dyspnea and fatigue are frequent but poorly understood symptoms in sarcoidosis patients. This study was aimed at assessing the clinical impact of inspiratory muscle impairment on dyspnea and exercise tolerance. This is the first study using nonvolitional tests that are independent of the patient's cooperation and motivation in addition to volitional tests of inspiratory muscle strength in patients with sarcoidosis.METHODS: Peak maximal inspiratory mouth pressure (Pimaxpeak), maximal inspiratory pressure sustained for 1.0 s (Pimax1.0), twitch mouth pressure (TwPmo), lung function test results, blood gas measurements, 6-min walking distance (6MWD), and Borg dyspnea scale (BDS) scores were assessed in 24 male sarcoidosis patients and 24 healthy male control subjects matched for age and body mass index.RESULTS: Mean (+/- SD) Pimaxpeak (95.2 +/- 25.3% vs 124.6 +/- 23.4% predicted, respectively; p < 0.001) and Pimax1.0 (85.6 +/- 31.4% vs 125.8 +/- 26.8% predicted, respectively; p < 0.001) were lower in sarcoidosis patients compared to control subjects. TwPmo tended to be lower in sarcoidosis patients, and there were three patients who had TwPmo values of < 1.0 kPa, which is a strong indicator of inspiratory muscle weakness. The mean 6MWD was 582 +/- 97 m in sarcoidosis patients and 638 +/- 65 in control subjects (p = 0.025). The mean BDS score was higher in sarcoidosis patients (3.3 +/- 1.7 vs 0.2 +/- 0.5, respectively; p < 0.001). Compared to maximal inspiratory pressure, lung function parameters, and blood gas levels, TwPmo was the strongest predictor for 6MWD (r = 0.663; p = 0.003) and BDS score (r = 0.575; p = 0.012) in sarcoidosis patients following multiple linear regression analysis.CONCLUSIONS: Impairment of inspiratory muscle strength occurs in sarcoidosis patients, and has been suggested to be an important factor causing dyspnea and reduced walking capacity, but this is only reliably detectable when using nonvolitional tests of inspiratory muscle strength.Key Words: Inspiratory muscle strength; maximal inspiratory pressure; muscle weakness; phrenic nerve stimulation; twitch mouth pressure

.Background/Introduction:

•Sarcoidosis is a systemic granulomatous disease of unknown etiology that is highly variable and characterized by diverse organ system manifestations •Dyspnea and fatigue are some of the most often reported symptoms, but the causes are unclear•50 to 80% are thought to experience skeletal muscle involvement; however, symptomatic muscle involvement has been suggested to be rare•Prior studies have all used volitional tests of respiratory muscle strength which are highly dependent on patient cooperation and motivation.•Non-volitional tests of inspiratory muscle strength, which are independent of patient cooperation and motivation, are more reliable in assessing inspiratory muscle involvement

Purpose:•Assess inspiratory muscle strength in sarcoidosis patients using both volitional and non-volitional tests•Verify the clinical impact of inspiratory muscle impairment on dyspnea and exercise tolerance as assessed by a 6-min walking test.

Discussion/Clinical Significance:•This is the first study in which nonvolitional tests of respiratory muscle strength have been used to quantify inspiratory muscle strength in sarcoidosis pts•The assessment of TwPmoIn showed no clear difference in sarcoidosis pts, which indicates that inspiratory muscle strength is, on average, not substantially reduced in sarcoidosis pts•Breathing frequency, tidal volume, and minute ventilation tended to be higher in sarcoidosis pts compared to control subjects•arterial oxygen saturation both at rest and after exercise were significantly lower in sarcoidosis pts compared to control subjects•Dyspnea on exertion is increased and 6MWD is decreased in pts with sarcoidosis

Conclusions:•Impairment of inspiratory muscle strength, if present, is suggested to be an important factor in causing dyspnea on exertion and reduced walking capacity•Further studies are needed in order to substantiate the impact of impaired inspiratory muscle strength on symptoms in sarcoidosis pts

Related Articles:•Article 1: Alhamad EH. The six minute walk test in patients with pulmonary sarcoidosis. Ann Thoracic Med. 2009; 4(2):60-64.•Retrospective study of 26 sarcoidosis diagnosed patients in Saudi Arabia whose functional impairments were assessed using the 6 minute walk test•Alhamad found that along with the majority of subjects having impaired 6MWDs, female gender, %, final Borg score, FVC%, CRP score and at the end of the 6MWT are associated with reduced 6MWD•Alhamad found similar results to Kabitz et al with FVC and being reduced and increased Borg scores in patients with sarcoidosis who completed the 6MWT Article 2: Alhamad EH, Shaik SA, Idrees MM, Alanezi MO, Isnani AC. Outcome measures of the 6 minute walk test: relationships with physiologic and computed tomography findings in patients with sarcoidosis. BMC Pulmonary Medicine. 2010; 10(42).•Retrospective study of 59 sarcoidosis diagnosed patients who were assessed to determine if levels during the 6MWT was as accurate of a predictor compared to other lung impairment outcome measures such as FVC,, TLC, and 6MWD.•Decreased level is a better predictor of pulmonary function when compared with pulmonary function tests (PFTs) than 6MWD alone.•Similar to the findings of Kabitz et al, reduced lung function in Sarcoidosis patients result in abnormal 6MWD; however levels could be a better predictor than inspiratory muscle strength at predicting 6MWD

SummaryIndividuals with sarcoidosis have significantly decreased exercise tolerance as has been illustrated by decreased 6MWD. Kabitz et al indicate that impaired inspiratory muscle strength is a significant predictor of exercise tolerance, whereas Alhamad et al indicate that reduced level is a significant determinant of decreased exercise tolerance. These studies provide some treatment insight for clinicians working with sarcoidosis patients who want to increase endurance and exercise tolerance. They suggest that by increasing inspiratory muscle strength and maintaining adequate, sarcoidosis patients may increase their ability to tolerate exercise.

Methods:•24 non smoking male pts with diagnosed sarcoidosis were studied and compared to a control group of 24 healthy, nonsmoking, age-matched and BMI matched men•Maximal inspiratory pressure (PIMax) was assessed as well as Peak maximal inspiratory pressure (PIMaxPEAK) and plateau PIMax was sustained for 1 s ( ).•Non-volitional tests for measuring inspiratory muscle strength consisted of twitch mouth pressure (TwPmo) during bilateral anterior magnetic phrenic nerve stimulation• 6-min walk test was performed for exercise testing w/ the following measurements: 6-min walking distance, dyspnea as assessed by Borg Dyspnea Scale (BDS), blood gas levels at rest and immediately following exercise, and a venous blood sample was drawn to provide data on neopterin, soluble interleukin-2 receptor, and angiotensin converting enzyme (ACE) levels since these serum markers are used to gauge sarcoidosis activity.Statistical Analysis:•Pearson product moment correlation was performed on sarcoidosis patients•Statistical significance was assumed with a p value <.05•Regression analysis was performed in order to calculate predictors for clinical parameters (ie, BDS and 6MWD)

Materials:•Body Plethysmography- Masterlab-Compact; Jaeger; Hochberg, Germany•Maximal inspiratory pressure-ZAN 100; ZAN GmbH; Oberthulba, Germany•Twitch mouth pressure- Magstim ; Magstim Inc; Dyfed, Wales, UK•Statistical software package- SigmaStat, version 3.1; Systat Software, Inc; Point Richmond, CA

Results:•Blood gas Parameters: arterial oxygen saturation both at rest and after exercise were significantly lower compared to control subjects•Sarcoidosis pts reported significantly higher degree of dyspnea and a significantly lower 6MWD•Volitional tests: Significantly lower values for both PIMaxPEAK and which were significantly correlated with FVC and total lung capacity•TwPmo was shown to be the strongest predictor for BDS score and 6MWD

Poster by David Pieschel, DPT Student