Hypoventilation syndromes

Brazilian Thoracic Association Consensus on Sleep-disordered Breathing

Sleep is essential for the proper functioning of all individuals. Sleep-disordered breathing can occur at any age and is a common reason for medical visits. The objective of this consensus is to update knowledge about the main causes of sleep-disordered breathing in adult and pediatric populations, with an emphasis on obstructive sleep apnea. Obstructive sleep apnea is an extremely prevalent but often underdiagnosed disease. It is often accompanied by comorbidities, notably cardiovascular, metabolic, and neurocognitive disorders, which have a significant impact on quality of life and mortality rates. Therefore, to create this consensus, the Sleep-Disordered Breathing Department of the Brazilian Thoracic Association brought together 14 experts with recognized, proven experience in sleep-disordered breathing.

A case of hypercapnic respiratory failure

A 55-year-old man was referred to the department of respiratory disease with a polycythaemia. Underlying haematological disease was already excluded. Blood results are shown in table 1.

A systematicwork-up is important in case of hypercapnia. Pay attention to the shape of the flow–volume curve and any abnormal breathing sounds. In case of stridor, vocal cord paralysis should be suspected and, if confirmed, neurological investigations are advised.https://bit.ly/34APMi8

Evaluation of sleep-disordered breathing and its relationship with respiratory parameters in children with mucopolysaccharidosis Type IVA and VI

The aims of the study were to evaluate the prevalence of sleep-disordered breathing (SDB) by using polysomnography (PSG) in children with MPS IVA and MPS VI who underwent enzyme replacement therapy (ERT) and to analyze the effect on SDB of having upper airway surgery, pulmonary functions, and exercise capacity. A retrospective cross-sectional study was conducted on patients with MPS IVA (n:17) and MPS VI (n:11) aged under 19 years who underwent polysomnography. Descriptive and nonparametric analyses were performed for demographic, PSG, pulmonary function and exercise capacity variables. The frequency of sleep apnea in the study sample was 85.7% (24/28). Four patients (14.3%) had no sleep apnea, 15 (53.6%) had mild, and nine (32.1%) had moderate-to-severe sleep apnea. Two patients (7.1%) had central sleep apnea and 22 had obstructive sleep apnea (OSA) (78.6%). Forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) were negatively correlated to apnea-hypopnea index (AHI) (r = -0.594, p = .009; r = -0.636, p = .005, respectively). Despite ERT and previous upper airway surgery, the prevalence of OSA was high in patients with MPS IVA-MPS IV, emphasizing the importance of PSG screening for sleep disorders. Pulmonary function tests may be useful for predicting sleep apnea in patients with MPS IVA and MPS VI.

Calcium Imaging Analysis of Cellular Responses to Hypercapnia and Hypoxia in the NTS of Newborn Rat Brainstem Preparation

It is supposed that the nucleus of the solitary tract (NTS) in the dorsal medulla includes gas sensor cells responsive to hypercapnia or hypoxia in the central nervous system. In the present study, we analyzed cellular responses to hypercapnia and hypoxia in the NTS region of newborn rat in vitro preparation. The brainstem and spinal cord were isolated from newborn rat (P0-P4) and were transversely cut at the level of the rostral area postrema. To detect cellular responses, calcium indicator Oregon Green was pressure-injected into the NTS just beneath the cut surface of either the caudal or rostral block of the medulla, and the preparation was superfused with artificial cerebrospinal fluid (25–26°C). We examined cellular responses initially to hypercapnic stimulation (to 8% CO₂ from 2% CO₂) and then to hypoxic stimulation (to 0% O₂ from 95% O₂ at 5% CO₂). We tested these responses in standard solution and in two different synapse blockade solutions: (1) cocktail blockers solution including bicuculline, strychnine, NBQX and MK-801 or (2) TTX solution. At the end of the experiments, the superfusate potassium concentration was lowered to 0.2 from 3 mM to classify recorded cells into neurons and astrocytes. Excitation of cells was detected as changes of fluorescence intensity with a confocal calcium imaging system. In the synaptic blockade solutions (cocktail or TTX solution), 7.6 and 8% of the NTS cells responded to hypercapnic and hypoxic stimulation, respectively, and approximately 2% of them responded to both stimulations. Some of these cells responded to low K⁺, and they were classified into astrocytes comprising 43% hypercapnia-sensitive cells, 56% hypoxia-sensitive cells and 54% of both stimulation-sensitive cells. Of note, 49% of the putative astrocytes identified by low K⁺ stimulation were sensitive to hypercapnia, hypoxia or both. In the presence of a glia preferential blocker, 5 mM fluoroacetate (plus 0.5 μM TTX), the percentage of hypoxia-sensitive cells was significantly reduced compared to those of all other conditions. This is the first study to reveal that the NTS includes hypercapnia and hypoxia dual-sensitive cells. These results suggest that astrocytes in the NTS region could act as a central gas sensor.

Prevalence of sleep apnoea and capnographic detection of nocturnal hypoventilation in amyotrophic lateral sclerosis

OBJECTIVE

This retrospective study aimed to investigate whether overnight oxymetry and early morning blood gas analysis predict nocturnal hypoventilation (NH) as reflected by night-time hypercapnia in patients with amyotrophic lateral sclerosis (ALS). In addition, prevalence and clinical determinants of sleep apnoea in ALS were evaluated.

METHODS

In 250 patients with non-ventilated ALS, transcutaneous capnometry was performed along with polysomnography or polygraphy and early morning blood gases.

RESULTS

123 patients were female, and 84 patients had bulbar-onset ALS. 40.0% showed NH, and an apnoea-hypopnoea index (AHI) >5/hour was found in 45.6%. In 22.3%, sleep apnoea and NH coincided. The obstructive apnoea index was significantly higher than the central apnoea index (p<0.0001). Both NH and sleep apnoea were significantly more common in male than in female patients. Sleep apnoea and AHI were associated with better bulbar function. Desaturation time (t_<90%) and transcutaneous CO₂ were negatively correlated with upright vital capacity. Early morning base excess (EMBE), bicarbonate and t_<90% were independent predictors of NH. However, among 100 patients with NH, 31 were missed by t_<90% >5 min and 17 were not identified when EMBE >3 mmol/L and t_<90% >5 min were combined.

CONCLUSION

In ALS, sleep apnoea is common and often accompanies NH. It is mainly obstructive, and central apnoea appears to be clinically irrelevant. Polygraphy or oxymetry alone are not sufficient to uncover NH. Combination of EMBE and t_<90% may increase sensitivity, but transcutaneous capnography is strongly recommended for reliable detection of NH in patients with ALS.

Correlation between severity of adolescent idiopathic scoliosis and pulmonary artery systolic pressure: a study of 338 patients

PURPOSE

Study of patients with adolescent idiopathic scoliosis.

OBJECTIVE

To examine the correlation between pulmonary arterial pressure and coronal Cobb angle of idiopathic scoliosis.

METHODS

A total of 338 patients (82.8 % female) with idiopathic scoliosis (average age 15.6 years; range 14-20 years) were included. Preoperatively, the coronal Cobb angle of curvature and the apex location and direction were determined from radiographic records. Tricuspid regurgitation velocity (TRV) and inferior vena cava diameter were also measured using Doppler echocardiography. Pulmonary arterial systolic pressure (sPAP) was calculated from the TRV according to the modified Bernoulli equation and correlations between sPAP and the features of scoliosis were identified by statistical analysis.

RESULTS

Among the 338 patients, there were 305 thoracic curves, 276 (90.5 %) of which were right curves, and 265 thoracolumbar/lumbar curves. sPAP varied from 5.0 to 37.6 mmHg. Pulmonary hypertension could not be excluded in the case of one patient. A mild correlation (Spearman test, correlation coefficient = 0.187, P = 0.001) between sPAP and coronal Cobb angle of the main thoracic (MT) curves was identified. Correlations between sPAP and the degree of other curves were not significant. Patients with sPAP >20 mmHg also had larger thoracic curve angles (mean MT 42.16° vs. 52.45°; U test, P = 0.002). There were no differences in sPAP levels between patients with right and left thoracic curves.

CONCLUSIONS

A mild positive correlation was identified between sPAP and the coronal Cobb angle of the MT curves. There was no relationship between sPAP and the direction of the curvature.

Positive airway pressure therapy for heart failure

Heart failure (HF) is a life-threatening disease and is a growing public health concern. Despite recent advances in pharmacological management for HF, the morbidity and mortality from HF remain high. Therefore, non-pharmacological approaches for HF are being developed. However, most non-pharmacological approaches are invasive, have limited indication and are considered only for advanced HF. Accordingly, the development of less invasive, non-pharmacological approaches that improve outcomes for patients with HF is important. One such approach may include positive airway pressure (PAP) therapy. In this review, the role of PAP therapy applied through mask interfaces in the wide spectrum of HF care is discussed.

Relationship of sleep to pulmonary function in mucopolysaccharidosis II

OBJECTIVE

To study the sleep characteristics, pulmonary function, and their relationships in an enzyme naive population of patients with mucopolysaccharidoses (MPS) II (Hunter syndrome).

STUDY DESIGN

The analyzed subjects (30 patients with MPS II with a median age of 9 years) had been enrolled in an MPS II natural history study and a phase I/II enzyme replacement clinical study in which they underwent standard polysomnography including spirometry and plethysmography, if cooperative. Descriptive statistics and nonparametric correlation were performed for demographic, sleep, and pulmonary function variables.

RESULTS

Median apnea-hypopnea index was 6.4, with obstructive sleep apnea observed in 27/30 subjects. Sleep architecture was characterized by diminished rapid-eye movement sleep duration (median 13%), and decline in sleep efficiency and slow-wave sleep duration in older individuals. Oxygen desaturation below 90% occurred in 26/30 subjects, and hypoventilation above 50 Torr occurred in 11/23 subjects with accurate end-tidal carbon dioxide recordings. Of 15 subjects with reliable spirometry, median forced expiratory volume in 1 second was below 80% predicted in 12/15 subjects. Forced expiratory volume in 1 second in percent-predicted was inversely related to apnea-hypopnea index and increase from baseline end-tidal carbon dioxide (P=.023, rs=-0.58), (P<.001, rs=-0.82).

CONCLUSION

Sleep in MPS II is characterized by obstructive sleep apnea, altered sleep architecture, and impaired gas exchange. Sleep disruption is related to daytime pulmonary function, thus both systems should be evaluated when sleep abnormalities are suspected.

Obesity in anesthesia and intensive care

Obesity is a global epidemic increasingly affecting management of anesthesia as well as intensive care medicine. Possible improvements in therapy require consideration of the specific pathophysiology of the obese, their concomitant diseases, and the complications associated with morbid obesity. Systematic assessment of perioperative risk factors is essential for an appropriate management. Paradoxically, overweight and moderately obese patients undergoing surgery have a lower risk when compared to patients with normal weight. The highest mortality and morbidity rates in this setting are reported for underweight and morbidly obese patients. The better chance of survival when compared to normal-weight individuals in the perioperative setting has been described the obesity paradox. In particular, the commitment of all involved physicians to improve all aspects of care will reduce the perioperative risk in obese patients. Physiological and pharmacological characteristics of the obese should also be considered. Furthermore, adequate technical equipment and practical skills of all members of the anesthesia team significantly contribute to risk reduction and therapeutic success in obese patients.

Neuromuscular disease and the pulmonologist

PURPOSE OF REVIEW

The heterogeneous nature of neuromuscular disorders (NMDs) continues to promote slow but steady advances in diagnosis, classification, and treatment. This review focuses on the updates in the general management and treatment of NMDs, with emphasis on key updates in muscular dystrophy, myotonic dystrophy, mitochondrial myopathy, spinal muscular atrophy, and hereditary neuropathies.

RECENT FINDINGS

Current research shows that improvements in morbidity and mortality in various NMDs may be possible. Key components include advances in identification and classification of individual NMDs; attention to anesthetic and surgical risks; aggressive pulmonary care; and implementations of a proactive, multidisciplinary, standard-of-care approach. Innovative molecular and pharmaceutical therapeutic options are being investigated in many of these disorders, but unfortunately no new intervention has borne out.

SUMMARY

Important advances were made in the last year in the field of neuromuscular disease. However, because of their heterogeneous nature and rarity, diagnosis and treatment of these disorders either as a single disorder or as a group continue to be both a clinical and a research challenge. It is of utmost importance that clinicians and researchers be aware of these disorders to aid in identification and treatment.