Skeletal Muscle Morphology and Aerobic Capacity in Patients with Obstructive Sleep Apnoea Syndrome

Abstract

Background: Despite the fact that patients with obstructive sleep apnoea syndrome (OSAS) often have symptoms at the level of skeletal muscle such as fatigue, the question of whether the structural, cellular and functional properties of limb skeletal muscles are affected has not been fully examined. Objective: The aim was to examine physiological and muscular parameters in patients with OSAS and to assess the relationship between these parameters and the clinical symptoms. Method: Eighteen patients with OSAS and 16 controls participated. Aerobic capacity was assessed using a submaximal test. Fibre type distribution and fibre area were analyzed on muscle biopsies taken from the tibialis anterior. The microvascularization was assessed using the following parameters: (1) the number of capillaries per fibre (CAF), (2) CAF per fibre area (CAFA), (3) capillary to fibre perimeter exchange (CFPE) index, which represents the interface between muscle fibre and capillaries, and (4) length of capillary/perimeter of the fibre (LC/PF) index or capillary tortuosity, which represents the percent of muscle fibre perimeter in contact with the wall of the microvessel. Results: The OSAS group had significantly lower predicted relative maximal oxygen uptake (p = 0.0047) which was inversely correlated to the apnoea/hypopnoea index (AHI; r = –0.6, p = 0.017). There was a significantly higher CFPE index for slow type I fibres (p = 0.007) and fast type II fibres (p = 0.0126) and a significantly higher LC/PF index for type I fibres (p = 0.0003) and type II fibres (p = 0.0285) in OSAS patients compared to controls. Conclusion: OSAS patients have a higher muscle microvascularization and a lower aerobic capacity than controls. Furthermore the aerobic capacity was inversely correlated to AHI.

Obstructive Sleep Apnea Is Associated with Impaired Exercise Capacity: A Cross-Sectional Study

“…14 Muscle biopsy studies have demonstrated structural and bioenergetic changes in skeletal muscle fiber in OSA subjects, 27 as well as increased microvascularization in skeletal muscle, 11 similar to changes observed in other states of chronic hypoxia. Several studies have demonstrated an abnormal cardiovascular response during exercise or recovery in OSA patients, including increased diastolic blood pressure, decreased stroke volume, attenuated heart rate during peak exercise and recovery, and global ventricular dysfunction.…”

“…[8][9][10] The impact of OSA on exercise capacity remains unclear. Prior studies examining exercise capacity in OSA patients have yielded confl icting results, with some demonstrating reduced exercise capacity [11][12][13][14][15][16] and others suggesting exercise capacity is not impaired. [8][9][10]17,18 These studies have several methodological limitations that make reconciling their fi ndings challenging.…”

“…[8][9][10]17,18 These studies have several methodological limitations that make reconciling their fi ndings challenging. In some studies, peak oxygen uptake ( O 2 ) was calculated from estimating equations rather than direct gas exchange measurements, 11,16 diminishing reliability of the assessment. 19 Others relied only on a thermister to detect respiratory events during polysomnography (PSG), 8,16 which underestimates such events compared to nasal pressure sensors 20 and likely led to enrollment of OSA subjects in the control group.…”

“…In one study, controls did not undergo PSG testing at all. Other potential confounding factors limiting interpretation of prior studies include absent reporting of duration 10,[12][13][14][15][16] and severity 13,15,16 of hypoxemia during sleep, sleep behavior in the days prior to testing, [8][9][10][11][12][13][14][15][16][17][18] and use of β-blocking medications. 8,9,11,12,[14][15][16][17] Furthermore, differences in age, gender, body mass index, and apnea-hypopnea index (AHI) make defi nitive comparison across studies challenging.…”

MRI Evaluation of the Oropharyngeal Region in Patients with Obstructive Sleep Apnea Syndrome

“…Parafaringeal kas dokusuna yönelik yapılan çalış-malarda horlayanlarda orta faringeal konstrüktör kaslarda tip 2a fiberlerinin yüzdesinin anlamlı ölçüde arttığı gösterilmiştir. Elektrofizyolojik olarakta üst havayolu kaslarında değişikler saptanmıştır (16)(17)(18) . Çalışmamızda, UAS pozitif grup ile negatif kontrol grubunu karşılaştırdığımızda parafaringeal duvar kalınlığının anlamlı ölçüde artmış olarak bulduk.…”