Breathing during sleep: Studies related to upper airway calibre in pregnancy
Snoring is common in pregnancy, and has been associated with an increased incidence of both maternal hypertension and preeclampsia, as well as an increased incidence of low birth weight infants and significantly poorer Apgar scores at birth. Patients with pre-eclampsia have episodes of partial upper airway (UA) obstruction during sleep. These repeated episodes are associated with further increases in blood pressure (BP). Preliminary evidence indicates that preventing episodes of airflow obstruction with continuous positive airway pressure (CPAP) therapy may reduce BP in pre-eclampsia. Snoring and apnoea-hypopnoea index (AHI) subside within a few months of delivery. However, there have been no studies measuring the effect of pregnancy or the postpartum period on UA dimension. The present study aimed to compare UA dimensions in pregnant and nonpregnant women and in patients with pre-eclampsia with a follow-up of the pregnant women post partum. Apart from snoring, excessive daytime sleepiness (EDS) is the most common complaint among pregnant women. A majority of the pregnant women including preeclamptic women have experienced EDS during pregnancy, but it is not clear whether EDS is associated with snoring. Thus, this thesis also examines whether snoring and sleepiness are linked in pregnancy and pre-eclampsia. In a cross-sectional study with a 3 way comparison, 50 pregnant, 37 pregnant women with pre-eclampsia in the third trimester of pregnancy, and 50 nonpregnant women were consecutively recruited. Control subjects were matched with pregnant women (both healthy pregnant and pre-eclamptic women) for age and pre-pregnancy BMI. UA dimensions were measured using acoustic reflection. Habitual snoring was reported by 15% of nonpregnant women, 28% of pregnant women, and 48% of pre-eclamptic women (p < 0.001). Pre-eclamptic women had narrower UAs compared to non-pregnant or healthy pregnant women in seated position (p < 0.02). Supine oropharyngeal junction area was also less in the women with pre-eclampsia than in the nonpregnant women (p = 0.01) but similar in women with pre-eclampsia and pregnant women (p > 0.3). When seated, pregnant women had wider UAs than nonpregnant women (p < 0.02). There was a non-significant trend for pregnant women to have narrower airways than non-pregnant women when supine. The data suggest that there may be pregnancy related changes in UA dimension, but this was not clear from this cross-sectional study of 3 groups, non-pregnant, pregnant and pre-eclamptic women. In a cross sectional study (with a 2 way comparison) with follow up of the pregnant women at least three months after their delivery, 100 women in the third trimester of pregnancy and 100 nonpregnant women, matched for age and BMI, were recruited. Fifty women agreed to be restudied 3 months after delivery. UA dimensions were measured using acoustic reflection. Snoring was less common in nonpregnant (17%) than pregnant women (41%) and returned to nonpregnant levels after delivery (18%). Pregnant women had significantly smaller UAs than nonpregnant women at the oropharyngeal junction when seated and smaller mean pharyngeal areas in the seated, supine and lateral postures compared with the nonpregnant females (p< 0.05). Pregnant women had smaller mean pharyngeal areas compared with post-partum in the seated, supine and lateral postures (p< 0.03). This study confirmed increased snoring and showed narrower UAs during the third trimester of pregnancy. One-hundred sixty-seven healthy and 82 pre-eclamptic women in the third trimester of pregnancy and 160 non-pregnant women completed a sleep questionnaire in a prospective questionnaire-based study. Age and height did not differ significantly between groups (P>0.2), but pre-eclamptic women were heavier than pregnant and non-pregnant women and had higher BMI than pregnant women before pregnancy (all P<0.05). Seventeen percent of control, 35% of pregnant and 59% of pre-eclamptic women snored (P<0.001), but pre-pregnancy snoring rates (both 10%) were similar to those in non-pregnant women (17%) (p>0.1). Sleepiness was reported by 12% of non-pregnant, 23% of pregnant and 15% of pre-eclamptic women (p<0.04), but non-pregnant women had lower mean Epworth Sleepiness scores than both pregnant and pre-eclamptic groups (P<0.001). Snoring was correlated with (p=0.002), but explained only <2% of the variance in sleepiness. The studies presented in this thesis indicate that UA narrowing occurs in the third trimester of pregnancy, probably due to pregnancy-related changes. It is likely that reduced UA calibre may contribute to the increased rate of snoring, breathing pauses and sleepiness in the third trimester of pregnancy, especially in patients with pre-eclampsia. However, sleepiness in pregnancy is largely due to factors other than snoring or breathing pauses.