Nocturnal hypoxaemia and hypercapnia in children with neuromuscular disorders

The aim of the study was to identify daytime predictors of nocturnal gas exchange anomalies in children with neuromuscular disease (NMD) and normal daytime gas exchange. Lung function tests, respiratory muscle evaluation and nocturnal gas exchange were obtained as part of routine evaluation. We included 52 consecutive children with Duchenne muscular dystrophy (n = 20), spinal muscular atrophy (n = 10) and other NMD (n = 22). 20 patients had nocturnal hypoxaemia, defined as minimal arterial oxygen saturation measured by pulse oximetry (S(p,O(2))) <90% for ≥ 2% of night time, and 22 had nocturnal hypercapnia, defined as maximal transcutaneous carbon dioxide tension (P(tc,CO(2))) >50 mmHg for ≥ 2% of night time. Forced vital capacity and helium functional residual capacity correlated with minimal nocturnal S(p,O(2)) (p = 0.009 and p = 0.01, respectively). Daytime pH correlated negatively with maximal nocturnal P(tc,CO(2)) (p=0.005) and daytime arterial carbon dioxide tension (P(a,CO(2))) correlated with the percentage of time with a P(tc,CO(2)) >50 mmHg (p = 0.02). Sniff nasal inspiratory pressure correlated with minimal nocturnal S(p,O(2)) (p = 0.02). Daytime P(a,CO(2)) was a weak predictor of nocturnal hypercapnia (sensitivity 80%; specificity 57%). Daytime lung function and respiratory muscle parameters correlate poorly with nocturnal hypoxaemia and hypercapnia in children with NMD and normal daytime gas exchange, which necessitates more systematic sleep studies in these children.     

Non-invasive positive pressure ventilation to facilitate the post-operative respiratory outcome of spine surgery in neuromuscular children

Purpose

Scoliosis surgery may be associated with a high morbidity and even mortality in children with non-idiopathic scoliosis. The aim of the study was to report our experience with a pre-operative training to non-invasive positive pressure ventilation (NPPV) and a mechanical insufflator–exsufflator (MI–E) device to improve the post-operative respiratory outcome of children scheduled for scoliosis surgery.

Methods

Consecutive patients with non-idiopathic scoliosis undergoing posterior arthrodesis were trained to NPPV and MI–E before intervention. NPPV and MI–E were performed immediately after extubation. Length of intubation and intensive care unit (ICU) stay, duration of NPPV, and respiratory complications were assessed.

Results

Thirteen patients participated in the training (mean age 13.9 ± 2.6, mean vital capacity 52.3 ± 15.4 % predicted). The patients had severe respiratory muscle weakness with a mean sniff oesophageal pressure of 35.8 ± 14.2 cmH₂O (50 % predicted) and a mean gastric pressure during a cough of 31.9 ± 7.8 cmH₂O (30 % predicted). The mean length of intubation was 19.9 ± 12.3 h with a mean length of ICU stay of 2.5 ± 2.5 days. NPPV was used during a mean of 2.7 ± 1.9 days after surgery. No respiratory complication was observed. One patient died 3 months after surgery from multi-organ failure of non-respiratory origin.

Conclusions

No respiratory complications were observed after scoliosis correction surgery in children with non-idiopathic scoliosis after pre-operative training and post-operative use of NPPV and MI–E, underlying the interest of this management in these high-risk patients.

     

Lung Function and Respiratory Health at School Age in Ventilated Very Low Birth Weight Infants

Objective

To investigate respiratory health and lung function in school-aged children without broncho-pulmonary dysplasia (BPD), who were very low birth weight (VLBWi) and randomized at birth to high frequency oscillatory ventilation (HFOV) or volume guarantee (VG) ventilation for severe respiratory distress syndrome (RDS).

Methods

In this observational study, 7-y-old ex-preterm infants with severe RDS, randomly assigned at birth to receive assisted/control ventilation?+?VG (Vt?=?5 mL/kg, PEEP?=?5 cmH₂O)(VG group; mean GA 27?±?2 wk; mean BW 1086?±?158 g) or HFOV (HFOV group; mean GA: 27?±?2; mean BW: 1090?±?139 g) (both groups were ventilated with Drager Babylog 8000 plus) were recalled. Neonatal clinical data and outcome were known. Actual outcomes were investigated with an interview; lung function was measured by whole-body plethysmography.

Results

Twenty five children were studied (VG group, n?=?13 vs. HFOV group, n?=?12). There were no differences in anthropometric data, drugs (steroids/bronchodilators and antibiotics) or hospital readmission for respiratory disorders. Compliance to the test was adequate. The authors found a similar obstructive deficit (elevated values: airway resistance (RAW), residual volume (RV), total lung capacity (TLC) with near-normal spirometry) in both groups suggesting a persistent airflow limitation even in absence of BPD.

Conclusions

VLBW infants even in absence of BPD, need long term respiratory follow-up, because they frequently show an impairment of lung function, independent from initial respiratory support, even if at birth the choice is a lung protective approach (e.g., HFOV or VG ventilation).     

Flavodiiron proteins Flv1 and Flv3 enable cyanobacterial growth and photosynthesis under fluctuating light

Cyanobacterial flavodiiron proteins (FDPs; A-type flavoprotein, Flv) comprise, besides the β-lactamase–like and flavodoxin domains typical for all FDPs, an extra NAD(P)H:flavin oxidoreductase module and thus differ from FDPs in other Bacteria and Archaea. Synechocystis sp. PCC 6803 has four genes encoding the FDPs. Flv1 and Flv3 function as an NAD(P)H:oxygen oxidoreductase, donating electrons directly to O₂ without production of reactive oxygen species. Here we show that the Flv1 and Flv3 proteins are crucial for cyanobacteria under fluctuating light, a typical light condition in aquatic environments. Under constant-light conditions, regardless of light intensity, the Flv1 and Flv3 proteins are dispensable. In contrast, under fluctuating light conditions, the growth and photosynthesis of the Δflv1(A) and/or Δflv3(A) mutants of Synechocystis sp. PCC 6803 and Anabaena sp. PCC 7120 become arrested, resulting in cell death in the most severe cases. This reaction is mainly caused by malfunction of photosystem I and oxidative damage induced by reactive oxygen species generated during abrupt short-term increases in light intensity. Unlike higher plants that lack the FDPs and use the Proton Gradient Regulation 5 to safeguard photosystem I, the cyanobacterial homolog of Proton Gradient Regulation 5 is shown not to be crucial for growth under fluctuating light. Instead, the unique Flv1/Flv3 heterodimer maintains the redox balance of the electron transfer chain in cyanobacteria and provides protection for photosystem I under fluctuating growth light. Evolution of unique cyanobacterial FDPs is discussed as a prerequisite for the development of oxygenic photosynthesis.