Background: Obstetric airway guidelines recommend preoxygenation in preparation for general anaesthesia to achieve end-tidal oxygen concentrations (etO 2) of !90%, and mention the potential use of high-flow humidified nasal oxygen (HFNO). We investigated the new HFNO technique (Optiflow™) in term pregnant women. Methods: Seventy-three term participants underwent a 3 min HFNO protocol (30 L min À1 for 30 s, and then 50 L min À1 for 150 s). The etO 2 was assessed for the first four breaths after simulated preoxygenation. The primary outcome was the proportion who achieved etO 2 !90% for the first expired breath. The secondary outcomes were the proportion who achieved etO 2 !80%; fetal heart rate before and after the test; the association of body mass index (BMI) to etO 2 achieved with preoxygenation; and comfort levels of, and preference for, nasal and face mask preoxygenation. Results: The proportion with first expired breath etO 2 !90% was 60% [95% confidence interval (CI): 54e66%] and etO 2 !80% was 84% (95% CI: 80e88%). There was no change in fetal heart rate from before to after the test (P¼0.34). There was a negative association of BMI to etO 2 achieved with preoxygenation (Pearson correlation: e0.26; P¼0.027). There was no difference in comfort scores between nasal cannula and face mask (P¼0.40). Forty-one (56%; 95% CI: 35e47%) women preferred the nasal cannula to the face mask. Conclusions: HFNO using this protocol is inadequate to preoxygenate term pregnant women. Despite encouraging results in the literature reporting results in non-pregnant women, further work is required before justifying its use in pregnant women. Clinical trial registration: ACTRN 12616000531415p.

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BackgroundThe prone position is rarely used in medical settings in pregnancy. There is no published information about the prone position in women with preeclampsia. This study examined the feasibility and acceptability of the prone position in pregnant women, and the short-term effect of the prone position on blood pressure (BP) in term healthy pregnant women and in women with preeclampsia.MethodsAfter ethics approval, written consent and trial registration (ACTRN:12615000160538 registered 18/02/2015, date of first participant enrolled 03/03/2015), 50 healthy term pregnant women and 15 women with preeclampsia had BP, heart rate (HR), oxygen saturation (SpO2), respiratory rate (RR), fetal heart rate (FHR) and comfort levels measured in two positions: left lateral, and prone. Measurements were after five minutes rest in each position.ResultsMean ± SD age, gestation and body mass index for healthy pregnant women was 33 ± 4.1 years, 38 ± 1.0 weeks and 27 ± 3.2 kg.m− 2 and for women with preeclampsia was 32 ± 4.7 years, 36 ± 3.4 weeks, 31 ± 5.6 kg.m− 2 respectively. No clinically significant changes occurred in healthy pregnant women in the prone position. Systolic BP was reduced in the prone position in women with preeclampsia (P = 0.019, mean difference − 6.6 mmHg, 95% confidence interval − 11.9 to − 1.3 mmHg). 33% of women with preeclampsia experienced a 10 mmHg or greater reduction in systolic BP in the prone position. 42% of healthy pregnant women and 47% of women with preeclampsia preferred the prone position to lateral.ConclusionsThis is the first study to examine the prone position in women with preeclampsia. For short periods of time the prone position is feasible and comfortable in pregnant women including those at term. The prone position may reduce systolic BP in women with preeclampsia without obvious adverse effects. Larger studies with women lying for longer periods in the prone position are required. Pregnancy should not be a contraindication to the prone position for short periods of time.Trial registration ACTRN:12615000160538 Electronic supplementary materialThe online version of this article (10.1186/s12884-018-2073-x) contains supplementary material, which is available to authorized users.

Optimal positioning for anaesthesia in pregnant women involves balancing the need for ideal tracheal intubation conditions (achieved by the head elevated ramped position), with the prevention of reduced cardiac output from aortocaval compression (achieved by left lateral pelvic tilt). No studies have examined the effect on cardiac output of left lateral pelvic tilt in the ramped position. We studied non-labouring, non-anaesthetised healthy term pregnant women who underwent baseline (left lateral decubitus) cardiac assessment using transthoracic echocardiography. We then compared cardiac output, maternal physiological variables, fetal heart rate and comfort scores in three positions: left lateral decubitus; ramped position with wedge; and ramped position alone. Thirty women completed the study. Mean (SD) age, gestation and body mass index were 33.5 (3.93) years, 38.5 (0.94) weeks and 29.0 (4.0) kg.m , respectively. Mean ejection fraction, left ventricular internal diameter and mitral valve E/e' were 55.2 (6.8) %, 4.70 (0.43) cm and 7.50 (1.82), respectively. There were no differences in cardiac output between the positions (p = 0.503). There were no differences in systolic (p = 0.955) or diastolic (p = 0.987) blood pressure, maternal heart rate (p = 0.133), oxygen saturation, respiratory rate (p = 0.964) or fetal heart rate (p = 0.361) between ramped with wedge and ramped alone positions. Left lateral decubitus was most comfortable (p = 0.001), however, there were no differences in comfort levels between ramped with wedge and ramped alone positions. The ramped position without left lateral tilt is safe and acceptable in non-labouring, non-anaesthetised, healthy term pregnant women. Left lateral pelvic tilt may be unnecessary in the head elevated ramped position in term pregnant women.

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BACKGROUND: Cardiac disease is the leading cause of maternal death. Assessment of cardiovascular fitness is important in pregnant women because it is linked to increased risk of cardiac disease but is rarely undertaken or studied. The 6-Minute Walk Test (6MWT) is a safe exercise test but is not used in pregnancy. We determined the 95% reference interval for resting heart rate (HR) and distance walked for the 6MWT, as well as hemodynamic recovery variables, and quantified expectations and actual experiences of exertion and breathlessness with exercise in late pregnancy. METHODS: After institutional research board approval (Australian and New Zealand Clinical Trials Registry Number: 12615000964516), 300 healthy term nulliparous pregnant women performed the 6MWT at 3 tertiary referral obstetric hospitals using a standardized protocol. Each woman underwent two 6MWT with maximum 15-minute recovery period after each test. Hemodynamic variables were measured at rest and after exercise. Participants were asked 4 questions, 2 regarding expectation and 2 regarding actual experience, using the Rating of Perceived Exertion scale and Modified Borg Dyspnea scale. RESULTS: Participant characteristics and resting variables were mean (standard deviation [SD]); age, 31 years (4.2 years); body mass index, 27 kg/m2 (2.9 kg/m2); gestational age, 37 weeks (1.3 weeks); HR, 85 bpm (10.8 bpm) with 95% reference interval 64–106 bpm; systolic blood pressure, 112 mm Hg (10.2 mm Hg); diastolic blood pressure, 72 mm Hg (8.6 mm Hg); oxygen saturation, 98% (0.9%); and respiratory rate, 18 breaths/min (5.7 breaths/min). The mean (SD) average distance walked was 488 m (94.9 m) with a speed of 3.0 mph (0.64 mph) with a 95% reference interval of 302–674 m. The mean (SD) HR increase with exercise was 12 bpm (11.0 bpm) with a median [quartile] recovery time of 5.0 minutes [1–8 minutes]. A lower resting HR was associated with increased distance walked (r = −0.207; 95% confidence interval, −0.313 to −0.096; P < .001). A greater HR change with exercise was associated with increased recovery time from exercise (r = 0.736; 95% confidence interval, 0.697–0.784; P < .001). Sixty-three percent and 83% of participants, respectively, expected to be more exerted and breathless than they actually were with exercise. CONCLUSIONS: The 6MWT is feasible and applicable in term pregnant women. The reference intervals for resting HR and distance walked in the 6MWT have been generated. HR increases by approximately 12 bpm with submaximal exercise, and half of the women recovered within 5 minutes of submaximal exercise. Women expected to be more exerted and breathless than they actually were with exercise.

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(Anesth Analg. 2019;129(2):450–457) The 6-Minute Walk Test (6MWT) is a validated tool that has been used to assess cardiorespiratory reserve in the nonpregnant population. Tools to identify pregnant women who have developed or are at risk of developing cardiac disease is lacking. Early recognition of cardiac disease and its risk in the pregnant population can reduce maternal morbidity and mortality as well as complications during and after birth. The aim of this study is to establish reference intervals for resting heart rate (HR) and the 6MWT in healthy women in late pregnancy, and to determine the expected and actual ratings of perceived exertion and breathlessness during exercise.