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Moderate concentrations of supplemental oxygen worsen hypercapnia in obesity hypoventilation syndrome: a randomised crossover study

Introduction

In people with obesity hypoventilation syndrome (OHS), breathing 100% oxygen increases carbon dioxide (PCO2), but its effect on pH is unknown. This study investigated the effects of moderate concentrations of supplemental oxygen on PCO2, pH, minute ventilation (VE) and physiological dead space to tidal volume ratio (VD/VT) among people with stable untreated OHS, with comparison to healthy controls.

 Methods

In a double-blind randomised crossover study, participants breathed oxygen concentrations (FiO2) 0.28 and 0.50, each for 20 min, separated by a 45 min washout period. Arterialised-venous PCO2 (PavCO2) and pH, VE and VD/VT were measured at baseline, then every 5 min. Data were analysed using general linear model analysis.

 Results

28 participants were recruited (14 OHS, 14 controls). Among OHS participants (mean±SD arterial PCO2 6.7±0.5 kPa; arterial oxygen 8.9±1.4 kPa) FiO2 0.28 and 0.50 maintained oxygen saturation 98–100%. After 20 min of FiO2 0.28, PavCO2 change (PavCO2) was 0.3±0.2 kPa (p=0.013), with minimal change in VE and rises in VD/VT of 1±5% (p=0.012). FiO2 0.50 increased PavCO2 by 0.5±0.4 kPa (p=0.012), induced acidaemia and increased VD/VT by 3±3% (p=0.012). VE fell by 1.2±2.1 L/min within 5 min then recovered individually to varying degrees. A negative correlation between VE and PavCO2 (r=–0.60, p=0.024) suggested that ventilatory responses were the key determinant of PavCO2 rises. Among controls, FiO2 0.28 and 0.50 did not change PavCO2 or pH, but FiO2 0.50 significantly increased VE and VD/VT.

 Conclusion

Commonly used oxygen concentrations caused hypoventilation, PavCO2 rises and acidaemia among people with stable OHS. This highlights the potential dangers of this common intervention in this group.

Prenatal origins of bronchiolitis: protective effect of optimised asthma management during pregnancy

Objective

Maternal asthma is the most common chronic disease complicating pregnancy and is a risk factor for bronchiolitis in infancy. Recurrent episodes of bronchiolitis are strongly associated with the development of childhood asthma.

 Methods

We conducted a follow-up study of infants born to women with asthma who completed a double-blind randomised controlled trial during pregnancy. In this trial, pregnant women with asthma were assigned to treatment adjustment by an algorithm using clinical symptoms (clinical group) or the fraction of exhaled nitric oxide (FeNO group) and we showed that the FeNO group had significantly lower asthma exacerbation rates in pregnancy.

 Results

146 infants attended the 12-month follow-up visit. Infants born to mothers from the FeNO group were significantly less likely to have recurrent episodes of bronchiolitis in the first year of life (OR 0.08, 95% CI 0.01 to 0.62; p=0.016) as compared with the clinical group.

 Conclusions

Optimised management of asthma during pregnancy may reduce recurrent episodes of bronchiolitis in infancy, which could potentially modulate the risk to develop or the severity of emerging childhood asthma.

Risk factors for sleep-disordered breathing in pregnancy

Rationale

Symptoms of sleep-disordered breathing (SDB) are common among pregnant women, and several studies link SDB symptoms with gestational hypertension and preeclampsia. However, few prospective studies objectively measuring SDB during pregnancy have been performed.

 Objectives

We performed a prospective cohort study examining risk factors for third trimester SDB in pregnant women.

 Measurements and methods

105 pregnant women from the Hospital of the University of Pennsylvania obstetrics practices completed first and third trimester overnight polysomnography studies. We examined whether the number of SDB events per hour of sleep increased during pregnancy. We performed unadjusted and multivariable logistic regression analyses to estimate the effects of usual and pregnancy-specific characteristics on development of third trimester obstructive sleep apnoea (OSA). In secondary analyses, we examined the relationship between objectively measured SDB, hypertensive disorders of pregnancy, and other adverse maternal-fetal outcomes.

 Main results

Mean Apnoea-Hypopnoea Index increased from 2.07 (SD 3.01) events/h at baseline (first trimester) to 3.74 (SD 5.97) in the third trimester (p=0.009). 10.5% of women had OSA in the first trimester. By the third trimester, 26.7% of women had OSA. In multivariable analyses, first trimester body mass index (BMI) and maternal age were significantly associated with third trimester OSA.

 Conclusions

Third trimester OSA is common. Risk factors for third trimester OSA among women without baseline SDB include higher baseline BMI and maternal age.

Systemic steroids in COPD-the beauty and the beast

The recommendations regarding the use of systemic steroids in COPD differ substantially depending on the phase of the disease. In moderate and severe acute exacerbations oral steroids are advocated based on the findings of several placebo-controlled trials that have been performed in secondary-care settings: these studies showed that systemic steroids improve lung function, dyspnoea and gas exchange. In addition, steroid use resulted in fewer treatment failures, a lower relapse rate and shorter hospital stays. Importantly, giving steroids orally is non-inferior to the i.v. application and an 8-week treatment is not superior to a 2-week therapy.

Recently, it could even be shown that 5-day treatment is non-inferior to a 14-day course. In the trial with longer term therapy hyperglycemia requiring treatment was identified as considerable side effect, in the other trials no major adverse events were observed. ...

Pulmonary function and survival in idiopathic versus secondary usual interstitial pneumonia.

CONCLUSION: Despite no significant differences in changes in pulmonary function over time, patients with CTD-UIP (at least those with certain classifiable CTDs) live longer than patients with IPF-an observation that we suspect is due to an increased rate of mortal acute exacerbations in patients with IPF.

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