Pulmonary Functions in Obstructive Sleep Apnea Hypopnea Syndrome in a Cohort of Patients Attending the Sleep Center of a Tertiary Care Hospital
M. K. Sen, J. C. Suri
Citation Information :
Sen MK, Suri JC. Pulmonary Functions in Obstructive Sleep Apnea Hypopnea Syndrome in a Cohort of Patients Attending the Sleep Center of a Tertiary Care Hospital. Indian Sleep Med 2007; 2 (1):21-27.
Eighty-nine patients (70 male and 19 female) of obstructive sleep apnea were retrospectively studied.
Material and Methods A detailed history was obtained and general physical, systemic and ENT examination performed. Their pulmonary function test reports, which included FVC, SVC, PEFR, PIFR, FEF25-75, flow-volume loop analysis, were interpreted. An arterial blood gas analysis (at rest, with the patient breathing room air during daytime) was obtained. A whole night fully supervised, manually validated, level-I complete polysomnography was conducted on all patients. Various sleep-study parameters (which included apnea, hypopnea, flow-limitation, RDI, arousal index, minimum oxygen saturation during sleep and desaturation index) were obtained.
Results Among the 89 patients, 39 had mild obstructive sleep apnea (OSA) (RDI 5-19), 26 had moderate OSA (RDI 19-39), and 24 had severe OSA (RDI>40). The average BMI of the patient population was 29.54 +1.16. There was a mild restrictive ventilatory impairment in the study population. The mean value of PEFR / PIFR ratio was 1.47 and was found to be >1 in 92.6% patients, thus indicating significant upper airway obstructive pattern. The flow-volume loops showed flattening of the inspiratory limb in 62% of the patients and characteristic saw-tooth pattern / undulations in 35% of the patients. The mean PaO2 was 73.85 mmHg indicating significant hypoxemia. There was a decreasing trend in the PaO2 value with increase in severity of sleep-disordered breathing. No significant correlations were observed between pulmonary function test variables (SVC, FVC, FEF25-75, PEFR and FEV1/FVC) and the severity of OSA i.e. RDI, minimum O2 saturation and desaturation index. However arousal index was found to correlate positively with the FVC (p=.0783) and SVC (p=.0545) (expressed as a percentage of the predicted value) respectively. There was also a significant negative correlation between daytime arterial PaO2 and RDI (p=0.0477), arousal index (p=0.0592), minimum O2 saturation (p=0.0458) and desaturation index (p=0.0316). A significant negative correlation was also seen between the PEFR / PIFR ratio and desaturation index (p=0.0515).
Conclusion On the basis of the present study it can be concluded that in a patient who presents with history suggestive of sleep disordered breathing, the presence of daytime hypoxemia, flattening of inspiratory limb of the flow volume loop with a PEFR/PIFR ratio>1 strengthen the suspicion of OSAS.
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