Effect of pregnancy on maternal oxygen saturation values: use of reflectance pulse oximetry during pregnancy

The Misattributed and Silent Causes of Poor COVID-19 Outcomes Among Pregnant Women

Abundant evidence strongly suggests that the condition of pregnancy makes women and their fetuses highly vulnerable to severe Corona-virus 2019 (COVID-19) complications. Here, two novel hypoxia-related conditions are proposed to play a pivotal role in better understanding the relationship between COVID-19, pregnancy and poor health outcomes. The first condition, "misattributed dyspnea (shortness of breath)" refers to respiratory symptoms common to both advanced pregnancy and COVID-19, which are mistakenly perceived as related to the former rather than to the latter; as a result, pregnant women with this condition receive no medical attention until the disease is in an advanced stage. The second condition, "silent hypoxia", refers to abnormally low blood oxygen saturation levels in COVID-19 patients, which occur in the absence of typical respiratory distress symptoms, such as dyspnea, thereby also leading to delayed diagnosis and treatment. The delay in diagnosis and referral to treatment, due to either "misattributed dypsnea" or "silent hypoxia", may lead to rapid deterioration and poor health outcome to both the mothers and their fetuses. This is particularly valid among women during advanced stages of pregnancy as the altered respiratory features make the consequences of the disease more challenging to cope with. Studies have demonstrated the importance of monitoring blood oxygen saturation by pulse oximetry as a reliable predictor of disease severity and outcome among COVID-19 patients. We propose the use of home pulse oximetry during pregnancy as a diagnostic measure that, together with proper medical guidance, may allow early diagnosis of hypoxia and better health outcomes.

Evaluation of Pulmonary Function Tests Among Pregnant Women of Different Trimesters in Debre Berhan Referral Hospital, Shoa, Ethiopia

Introduction

Pregnancy is characterized by a sequence of dynamic physiological changes that impact multiple organ system functions and is associated with various changes in pulmonary anatomy and physiology. Precise knowledge of the pulmonary function test parameters helps to understand and manage the course and outcome of pregnancy leading to safe delivery. It also helps to avoid misdiagnosis and unnecessary interventions. The aim of this study was to evaluate the effect of normal pregnancy on pulmonary function tests among pregnant women in Debre Berhan Referral Hospital, Ethiopia.

Methods

A total of 176 study participants (first, second, and third trimester; and control) were involved under a comparative cross-sectional study design and convenience sampling technique. Anthropometric data, oxygen saturation of arterial blood, and pulmonary function tests were measured. Data were tabulated and statistically analyzed using SPSS version 20.0 statistical software. Means of all parameters were compared using one-way ANOVA followed by Tukey’s post hoc multiple comparison test. Statistical significance was preset at a p-value of less than 0.05.

Results

Mean of FVC for the controls, first, second, and third trimesters was 2.59 ± 0.26, 2.13 ± 0.15, 1.93 ± 0.27, and 1.90 ± 0.11 liters, respectively. Except for FEV_1%, the mean values of FVC, FEV₁, PEFR, and FEF _25–75% in the pregnant group (all the three trimesters) were significantly decreased from the controls (P<0.05). Strong negative correlation was seen between SaO₂ and RR (r= −0.865; P <0.01). As the pregnancy progressed from first to the third trimester, dynamic pulmonary function tests (FVC, FEV₁, FEF_25-75%, and PEFR) were dropped and the respiratory rate increased.

Conclusion

The results had shown the tendency of obstructive pattern while pregnancy becoming advanced. We have observed also a remarkable decline of SaO₂ in pregnant women that might be counterbalanced by raised respiratory rate.

Maternal oxygen administration and fetal cerebral oxygenation: studies on near-term fetal lambs at both low and high altitude

OBJECTIVE

We tested the hypothesis that O2 administration to the mother would increase arterial O2 tension (PaO2) and cortical tissue O2 tension (tPO2) in both the normoxic control fetus and that acclimatized to high altitude, and that this effect might be greater in the high altitude fetus than that at sea level.

STUDY DESIGN

Pregnant ewes were divided into either low-altitude group or high-altitude group (3820 m; maintained from day 30 of gestation to near-term, term = 145 days; n = 6 each). In near-term fetuses we instrumented the cerebral cortex with tissue PO2-laser Doppler flow probes, and placed arterial catheters. With the ewe breathing either air or 50% O2, we measured fetal arterial and brain tissue PO2 and cerebral blood flow (CBF).

RESULTS

In response to maternal O2 administration, in both low- and high-altitude fetuses, PaO2, O2 content, and brain tissue PO2 increased significantly. Nonetheless, the fetuses at high altitude showed significantly greater increase in both PaO2 and cerebral tPO2, than that seen in fetuses at low altitude. In neither group was there a change in CBF or cerebral metabolic rate for O2.

CONCLUSION

Maternal O2 administration significantly increased PaO2 and cerebral tPO2 of the fetus both at low altitude and at high altitude, with this increase being greater in the high altitude animals. We suggest that maternal O2 administration can have an important effect in ameliorating nonreassuring fetal status, and perhaps be of value in instances of mothers who smoke heavily or with cardiopulmonary disease.

Physiological Basis for Recommendations Regarding Exercise during Pregnancy at High Altitude

Although exercise during pregnancy has been shown to be safe and is now recommended by the American College of Obstetricians and Gynecologists and the Society of Obstetricians and Gynaecologists of Canada for all healthy women, little is known about the combined effects of high altitude and exercise during pregnancy. Due to a paucity of experimental data, recommendations regarding exercise during pregnancy at elevations >/=1600 m must be based on synthesis of available information regarding the independent effects of high altitude and exercise on uteroplacental oxygen delivery. Maternal hyperventilation and elevated blood hemoglobin concentration maintain resting arterial oxygen content at or above sea-level values. During exercise, however, arterial hemoglobin saturation falls, lowering the oxygen content. Resting uterine artery blood flow is lower in residents at 3100 m than at 1600 m, and flow is likely to decrease further during exercise, in proportion to the intensity and duration. The combined reduction in arterial oxygen content and uterine artery flow suggest that fetal oxygen delivery is compromised during exercise at altitude. Anemia, which should be defined according to altitude-adjusted criteria, will further diminish oxygen delivery. Clinicians may wish to monitor patient hemoglobin concentration more frequently and adopt a more conservative stance regarding exercise during pregnancy for both residents and visitors of altitudes >/=1600 m.

A longitudinal study of maternal oxygen saturation during short-term submaximal exercise

PURPOSE

Longitudinal prospective study before, during and after normal pregnancy of the effect of short-term submaximal exercise on maternal oxygen saturation.

METHODS

Fourteen healthy women were recruited to the study before a planned pregnancy, and were followed seven times during the pregnancy and for up to 6 month after delivery. A submaximal bicycle exercise test with a target heart rate of 85% of the predicted age-adjusted maximum was performed. Maternal oxygen saturation was continuously recorded using a pulse oximeter.

RESULTS

Maternal oxygen saturation at maximum work-load had increased significantly already at 8 weeks gestation compared with preconception levels, and remained at a significantly higher level until 29 weeks of gestation. Thereafter, the oxygen saturation continued to be higher even at 6 month postpartum. During the exercise test, the lowest saturation was found during the late recovery period, this remained unchanged before, during and after pregnancy.

CONCLUSION

A pregnant woman responds to short-term exercise by increasing the oxygen saturation until 29 weeks. After that, the saturation level decreases but remains at a higher level even 6 month after delivery compared with preconception levels.

Acute respiratory distress syndrome in pregnancy

Acute respiratory distress syndrome is a serious sequelae of many serious illnesses during pregnancy. An understanding of acute respiratory distress syndrome is central to the proper care of a patient with the disorder. Acute respiratory distress syndrome results in diminished pulmonary compliance and respiratory shunt mediated hypoxemia. Furthermore, the initial pulmonary injury in acute respiratory distress syndrome may be further worsened by therapeutic hyperoxia and barotrauma. Limitation of peak-plateau airway pressure to less than 35 to 40 cm H2O may reduce barotrauma. Inflammatory mediator therapy may hold future promise in attenuation of lung injury induced by acute respiratory distress syndrome. Aggressive care may help those pregnant patients afflicted with acute respiratory distress syndrome.