Pathophysiology of changes in absolute lung volumes

Development and validation of a score for prediction of postoperative respiratory complications in infants and children (SPORC-C)

BACKGROUND

In infants and children, postoperative respiratory complications are leading causes of perioperative morbidity, mortality, and increased healthcare utilisation. We aimed to develop a novel score for prediction of postoperative respiratory complications in paediatric patients (SPORC for children).

METHODS

We analysed data from paediatric patients (≤12 yr) undergoing surgery in New York and Boston, USA for score development and external validation. The primary outcome was postoperative respiratory complications within 30 days after surgery, defined as respiratory infection, respiratory failure, aspiration pneumonitis, pneumothorax, pleural effusion, bronchospasm, laryngospasm, and reintubation. Data from Children's Hospital at Montefiore were used to create the score by stepwise backwards elimination using multivariate logistic regression. External validation was conducted using a separate cohort of children who underwent surgery at Massachusetts General Hospital for Children.

RESULTS

The study included data from children undergoing 32,187‬ surgical procedures, where 768 (2.4%) children experienced postoperative respiratory complications. The final score consisted of 11 predictors, and showed discriminatory ability in development, internal, and external validation cohorts with areas under the receiver operating characteristic curve of 0.85 (95% confidence interval: 0.83-0.87), 0.84 (0.80-0.87), and 0.83 (0.80-0.86), respectively.

CONCLUSION

SPORC is a novel validated score for predicting the likelihood of postoperative respiratory complications in children that can be used to predict postoperative respiratory complications in infants and children.

The Modulation by Anesthetics and Analgesics of Respiratory Rhythm in the Nervous System

Rhythmic eupneic breathing in mammals depends on the coordinated activities of the neural system that sends cranial and spinal motor outputs to respiratory muscles. These outputs modulate lung ventilation and adjust respiratory airflow, which depends on the upper airway patency and ventilatory musculature. Anesthetics are widely used in clinical practice worldwide. In addition to clinically necessary pharmacological effects, respiratory depression is a critical side effect induced by most general anesthetics. Therefore, understanding how general anesthetics modulate the respiratory system is important for the development of safer general anesthetics. Currently used volatile anesthetics and most intravenous anesthetics induce inhibitory effects on respiratory outputs. Various general anesthetics produce differential effects on respiratory characteristics, including the respiratory rate, tidal volume, airway resistance, and ventilatory response. At the cellular and molecular levels, the mechanisms underlying anesthetic-induced breathing depression mainly include modulation of synaptic transmission of ligand-gated ionotropic receptors (e.g., γ-aminobutyric acid, N-methyl-D-aspartate, and nicotinic acetylcholine receptors) and ion channels (e.g., voltage-gated sodium, calcium, and potassium channels, two-pore domain potassium channels, and sodium leak channels), which affect neuronal firing in brainstem respiratory and peripheral chemoreceptor areas. The present review comprehensively summarizes the modulation of the respiratory system by clinically used general anesthetics, including the effects at the molecular, cellular, anatomic, and behavioral levels. Specifically, analgesics, such as opioids, which cause respiratory depression and the "opioid crisis", are discussed. Finally, underlying strategies of respiratory stimulation that target general anesthetics and/or analgesics are summarized.

Neonatal Airway Management

Safe and effective airway management of neonates requires unique knowledge and clinical skills. Practitioners should have an understanding of neonatal airway anatomy and respiratory physiology and their clinical implications related to airway management. It is vital to recognize the potential sequelae of prematurity. Clinicians should be familiar with the skills and techniques available for managing normal neonatal airways. This review provides stepwise considerations for managing the neonatal airway: specific considerations for neonatal airway management, assessment and preparation, induction and premedication, and techniques and strategies for airway management in patients with normal anatomy and in patients who are difficult to intubate.

Combined pulmonary fibrosis and emphysema: How does cohabitation affect respiratory functions?

PURPOSE

Combined pulmonary fibrosis and emphysema (CPFE) has emerged as a new syndrome with characteristics of both fibrosis and emphysema. We determined the impacts of radiologic emphysema severity on pulmonary function tests (PFTs), exercise capacity and mortality.

PATIENTS AND METHODS

IPF patients (n = 110) diagnosed at the Chest Diseases Clinic between September 2013 and January 2016 were enrolled in the study and followed up until June 2017. Visual and digital emphysema scores, PFTs, pulmonary artery pressure (sPAP), 6-minute walking test, composite physiologic index (CPI), and survival status were recorded. Patients with emphysema and those with pure IPF were compared.

RESULTS

The CPFE-group had a significantly greater ratio of men(p < 0.001), lower BMI (p < 0.001), lower mean PaO₂ (p = 0.005), higher mean sPAP (p = 0.014), and higher exercise desaturation (p < 0.001). The CPFE group had a significantly higher FVC(L)(p = 0.016), and lower FEV1/FVC ratio (p = 0.002), DLCO, and DLCO/VA ratio(p = 0.03 and p = 0.005, respectively). Lung volumes of the CPFE group had significantly higher VC(p = 0.017), FRC (p < 0.001), RV(p < 0.001), RV/TLC(p < 0.001), and TLC(p < 0.001). There were significant correlations between emphysema scores and FVC (L)(p = 0.01), FEV1/FVC(p = 0.001), DLCO (p = 0.003), VC(p = 0.014), FRC (L)(p < 0.001), RV(p < 0.001), TLC(p < 0.001), and RV/TLC (p < 0.001). Mortality rates were comparable between the two groups. CPI (p = 0.02) and sPAP (p = 0.01) were independent predictors of mortality in patients with CPFE.

CONCLUSIONS

The presence and severity of emphysema affects pulmonary function in IPF. Patients with CPFE have reduced diffusion capacity, more severe air trapping, worse muscle weakness, more severe exercise desaturation, and pulmonary hypertension. CPI and pulmonary hypertension are two independent risk factors for mortality in subjects with CPFE.

Reference values for pulmonary volumes by plethysmography in a Brazilian sample of white adults

OBJECTIVE

To derive reference values for healthy white Brazilian adults who have never smoked and to compare the obtained values with reference values derived by Crapo and by Neder.

METHODS

Reference equations by quantile regressions were derived in 122 men and 122 women, non-obese, living in seven cities in Brazil. Age ranged from 21 to 92 years in women and from 25 to 88 years in men. Lung function tests were performed using SensorMedics automated body plethysmographies according ATS/ERS recommendations. Lower and upper limits were derived by specific equations for 5 and 95 percentiles. The results were compared to those suggested by Crapo in 1982, and Neder in 1999.

RESULTS

Median values for total lung capacity (TLC) were influenced only by stature in men, and by stature and age in women. Residual volume was influenced by age and stature in both genders. Weight was directly related to inspiratory capacity and inversely with functional residual capacity and expiratory reserve volume in both genders. A comparison of observed TLC data with values predicted by Neder equations showed significant lower values by the present data. Mean values were similar between data from present study and those derived by Crapo.

CONCLUSION

New predicted values for lung volumes were obtained in a sample of white Brazilians. The values differ from those derived by Neder, but are similar to those derived by Crapo.

Percent Emphysema and Daily Motor Activity Levels in the General Population: Multi-Ethnic Study of Atherosclerosis

BACKGROUND

COPD is associated with reduced physical capacity. However, it is unclear whether pulmonary emphysema, which can occur without COPD, is associated with reduced physical activity in daily life, particularly among people without COPD and never smokers. We hypothesized that greater percentage of emphysema-like lung on CT scan is associated with reduced physical activity assessed by actigraphy and self-report.

METHODS

The Multi-Ethnic Study of Atherosclerosis (MESA) enrolled participants free of clinical cardiovascular disease from the general population. Percent emphysema was defined as percentage of voxels < -950 Hounsfield units on full-lung CT scans. Physical activity was measured by wrist actigraphy over 7 days and a questionnaire. Multivariable linear regression was used to adjust for age, sex, race/ethnicity, height, weight, education, smoking, pack-years, and lung function.

RESULTS

Among 1,435 participants with actigraphy and lung measures, 47% had never smoked, and 8% had COPD. Percent emphysema was associated with lower activity levels on actigraphy (P = .001), corresponding to 1.5 hour less per week of moderately paced walking for the average participant in quintile 2 vs 4 of percent emphysema. This association was significant among participants without COPD (P = .004) and among ever (P = .01) and never smokers (P = .03). It was also independent of coronary artery calcium and left ventricular ejection fraction. There was no evidence that percent emphysema was associated with self-reported activity levels.

CONCLUSIONS

Percent emphysema was associated with decreased physical activity in daily life objectively assessed by actigraphy in the general population, among participants without COPD, and nonsmokers.

Ventilation heterogeneity measured by multiple breath inert gas testing is not affected by inspired oxygen concentration in healthy humans

Multiple breath washout (MBW) and oxygen-enhanced MRI techniques use acute exposure to 100% oxygen to measure ventilation heterogeneity. Implicit is the assumption that breathing 100% oxygen does not induce changes in ventilation heterogeneity; however, this is untested. We hypothesized that ventilation heterogeneity decreases with increasing inspired oxygen concentration in healthy subjects. We performed MBW in 8 healthy subjects (4 women, 4 men; age = 43 ± 15 yr) with normal pulmonary function (FEV₁ = 98 ± 6% predicted) using 10% argon as a tracer gas and oxygen concentrations of 12.5%, 21%, or 90%. MBW was performed in accordance with ERS-ATS guidelines. Subjects initially inspired air followed by a wash-in of test gas. Tests were performed in balanced order in triplicate. Gas concentrations were measured at the mouth, and argon signals rescaled to mimic a N₂ washout, and analyzed to determine the distribution of specific ventilation (SV). Heterogeneity was characterized by the width of a log-Gaussian fit of the SV distribution and from S_acin and S_cond indexes derived from the phase III slope. There were no significant differences in the ventilation heterogeneity due to altered inspired oxygen: histogram width (hypoxia 0.57 ± 0.11, normoxia 0.60 ± 0.08, hyperoxia 0.59 ± 0.09, P = 0.51), S_cond (hypoxia 0.014 ± 0.011, normoxia 0.012 ± 0.015, hyperoxia 0.010 ± 0.011, P = 0.34), or S_acin (hypoxia 0.11 ± 0.04, normoxia 0.10 ± 0.03, hyperoxia 0.12 ± 0.03, P = 0.23). Functional residual capacity was increased in hypoxia (P = 0.04) and dead space increased in hyperoxia (P = 0.0001) compared with the other conditions. The acute use of 100% oxygen in MBW or MRI is unlikely to affect ventilation heterogeneity.NEW & NOTEWORTHY Hyperoxia is used to measure the distribution of ventilation in imaging and MBW but may alter the underlying ventilation distribution. We used MBW to evaluate the effect of inspired oxygen concentration on the ventilation distribution using 10% argon as a tracer. Short-duration exposure to hypoxia (12.5% oxygen) and hyperoxia (90% oxygen) during MBW had no significant effect on ventilation heterogeneity, suggesting that hyperoxia can be used to assess the ventilation distribution.

Effects of anaesthesia techniques and drugs on pulmonary function

The primary task of the lungs is to maintain oxygenation of the blood and eliminate carbon dioxide through the network of capillaries alongside alveoli. This is maintained by utilising ventilatory reserve capacity and by changes in lung mechanics. Induction of anaesthesia impairs pulmonary functions by the loss of consciousness, depression of reflexes, changes in rib cage and haemodynamics. All drugs used during anaesthesia, including inhalational agents, affect pulmonary functions directly by acting on respiratory system or indirectly through their actions on other systems. Volatile anaesthetic agents have more pronounced effects on pulmonary functions compared to intravenous induction agents, leading to hypercarbia and hypoxia. The posture of the patient also leads to major changes in pulmonary functions. Anticholinergics and neuromuscular blocking agents have little effect. Analgesics and sedatives in combination with volatile anaesthetics and induction agents may exacerbate their effects. Since multiple agents are used during anaesthesia, ultimate effect may be different from when used in isolation. Literature search was done using MeSH key words ‘anesthesia’, ‘pulmonary function’, ‘respiratory system’ and ‘anesthesia drugs and lungs’ in combination in PubMed, Science Direct and Google Scholar filtered by review and research articles sorted by relevance.

Long-term effects of gastrectomy in patients with spirometry-defined COPD and patients at risk of COPD: a case-control study

OBJECTIVE

Comorbidities are characteristic of COPD. However, little is known about the secondary manifestations of COPD in the gastrointestinal tract. Therefore, we aimed to explore the long-term effects of gastrectomy in patients with spirometry-defined COPD or those at risk of COPD.

PARTICIPANTS

Subjects included 87 patients either with COPD or at risk of COPD (symptomatic) who underwent gastrectomy between December 2003 and October 2013 (group A), and 174 patients either with COPD or at risk of COPD, matched by age (±5 years), sex, and forced expiratory volume in 1 second (FEV1) as percentage of predicted (FEV1% predicted) (±5%) (group B).

METHODS

All patients underwent routine blood chemistry and pulmonary function tests, arterial blood gas analysis, 6-minute walk test (6MWT), high-resolution chest computed tomography scans, and nutritional assessments.

RESULTS

The mean duration postgastrectomy was 18.3±15.4 years. The mean FEV1 and FEV1% predicted were 2.07±0.76 L and 74.6±24.5%, respectively. Univariate analysis indicated that group A patients had significantly lower body mass index, fat-free mass index, and serum hemoglobin and albumin concentration (all P=0.00), and walked a significantly shorter distance in the 6MWT (P<0.05). Multivariate linear regression analysis for the distance in the 6MWT indicated that increased residual volume (RV) to total lung capacity (TLC) as percentage of predicted (%RV/TLC) alone was an independent and significant predictor of reduced distances in the 6MWT.

CONCLUSION

We concluded that nutritional insufficiency in patients with COPD (or those at risk of COPD) who previously underwent gastrectomy might lead to hyperinflation and consequently, decreased exercise capacity.

Not all measures of hyperinflation are created equal: lung structure and clinical correlates of gas trapping and hyperexpansion in COPD: the Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study

BACKGROUND

Hyperinflation refers to a nonspecific increase in absolute lung volumes and has a poor prognosis in COPD. The relative contribution of increased airways resistance and increased parenchymal compliance to hyperinflation of each absolute lung volume is poorly understood. We hypothesized that increased residual volume (RV) and RV/total lung capacity (TLC) would be associated with reduced airway lumen dimensions, whereas increased functional residual capacity (FRC), TLC, and reduced inspiratory capacity (IC)/TLC would be associated with emphysema on CT scan. We examined whether clinical characteristics differed accordingly.

METHODS

The Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study recruited smokers aged 50 to 79 years who were free of clinical cardiovascular disease. Gas trapping was defined as RV or RV/TLC greater than the upper limit of normal and hyperexpansion as FRC or TLC greater than the upper limit of normal or IC/TLC less than the lower limit of normal. Airway lumen diameters and percent emphysema &lt; -950 Hounsfield units were quantified on CT images. Analyses were adjusted for age, sex, body size, race/ethnicity, education, and smoking.

RESULTS

Among 116 participants completing plethysmography, 15% had gas trapping, 18% has hyperexpansion, and 22% had both. Gas trapping was associated with smaller airway lumen diameters (P = .001), greater dyspnea (P = .01), and chronic bronchitis (P = .03). Hyperexpansion was associated with percent emphysema (P &lt; .001), lower BMI (P = .04), and higher hemoglobin concentration (P = .001).

CONCLUSIONS

Gas trapping and hyperexpansion on plethysmography were associated with distinct differences in lung structure and clinical characteristics. Absolute lung volumes should not be considered equivalent in their estimation of hyperinflation and provide insight into the extent of airway and parenchymal abnormalities in COPD.

DNAH5 is associated with total lung capacity in chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is characterized by expiratory flow limitation, causing air trapping and lung hyperinflation. Hyperinflation leads to reduced exercise tolerance and poor quality of life in COPD patients. Total lung capacity (TLC) is an indicator of hyperinflation particularly in subjects with moderate-to-severe airflow obstruction. The aim of our study was to identify genetic variants associated with TLC in COPD.

METHODS

We performed genome-wide association studies (GWASs) in white subjects from three cohorts: the COPDGene Study; the Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints (ECLIPSE); and GenKOLS (Bergen, Norway). All subjects were current or ex-smokers with at least moderate airflow obstruction, defined by a ratio of forced expiratory volume in 1 second to forced vital capacity (FEV1/FVC) <0.7 and FEV1 < 80% predicted on post-bronchodilator spirometry. TLC was calculated by using volumetric computed tomography scans at full inspiration (TLCCT). Genotyping in each cohort was completed, with statistical imputation of additional markers. To find genetic variants associated with TLCCT, linear regression models were used, with adjustment for age, sex, pack-years of smoking, height, and principal components for genetic ancestry. Results were summarized using fixed-effect meta-analysis.

RESULTS

Analysis of a total of 4,543 COPD subjects identified one genome-wide significant locus on chromosome 5p15.2 (rs114929486, β = 0.42L, P = 4.66 × 10-8).

CONCLUSIONS

In COPD, TLCCT was associated with a SNP in dynein, axonemal, heavy chain 5 (DNAH5), a gene in which genetic variants can cause primary ciliary dyskinesia. DNAH5 could have an effect on hyperinflation in COPD.

Adjunctive treatments in pediatric acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a devastating process that involves pulmonary inflammation, alveolar damage and hypoxemic respiratory failure. Although advances in management approaches over the past two decades have resulted in significantly improved outcomes, death from pediatric ARDS may still occur in up to 35% of patients. While invasive mechanical ventilation is an essential component of ARDS management, various adjuncts have been utilized as treatment for these patients. However, evidence-based data in infants and children in this area are lacking. In this article, the authors review the available evidence supporting (or not supporting) the use of non-ventilatory adjunctive strategies in the management of pediatric ARDS, including prone positioning, pulmonary vasodilators, β-agonists, steroids and surfactant.

A Review of Kidney Motion under Free, Deep and Forced-Shallow Breathing Conditions: Implications for Stereotactic Ablative Body Radiotherapy Treatment

Motion management strategies are important during stereotactic ablative body radiotherapy for abdominal targets. The kidney is a mobile retroperitoneal organ that moves with respiration. A review of the literature was performed to investigate the reported degree of kidney motion associated with various breathing conditions. A structured search was performed using Medline from January 1970 to May 2013 for all publications describing cranial-caudal kidney motion. Relevance to radiotherapy practice was reviewed based on any breathing instructions and/or immobilization equipment that could affect breathing pattern. Studies were categorized under three types of breathing conditions: Forced-shallow, breath-hold/deep and free. A total of 25 publications were identified describing cranial-caudal kidney motion with a combined total of 415 participants. Three publications described forced-shallow breathing using prone positioning or abdominal compression plates. Prone positioning, compared to supine positioning, did little to minimise kidney motion, however use of compression plates can result in kidney motion of less than 5 mm. Eight publications described deep breathing/breath hold techniques that showed average kidney motion ranging between 10 mm-40 mm. Fifteen publications investigated kidney motion under free breathing with the majority reporting mean motion of less than 10 mm. Kidney movement of up to 8.1 mm in the anterior posterior direction and 6.2 mm laterally were reported with no indications that breathing technique can influence the extent of this motion. In summary, kidney movement is complex and consideration should be made to ensure that motion management strategies provide the desired radiotherapy benefit. There are limited publications on the effectiveness of abdominal compression on reducing kidney motion which warrant further investigation in this area.

The lungs need to be deflated: effects of glycopyrronium on lung hyperinflation in COPD patients

Chronic obstructive pulmonary disease (COPD) is characterized by persistent airflow limitation caused by bronchial alterations, small airways disease and parenchymal destruction. In patients with COPD the structural and functional lung alterations can progress more or less rapidly from the initial small airways disease to an overt COPD where a severe expiratory flow limitation takes place. In these conditions, lung hyperinflation develops characterized by increase in functional residual capacity (FRC) and decrease in inspiratory capacity (IC). Thus, IC is an easy and reliable index to monitor lung hyperinflation and to assess the efficacy of bronchodilator drugs. When FRC increases, tidal volume (VT) is located in a more flatted upper part of the P -V curve of the respiratory system and respiratory muscles must sustain a greater elastic workload. Furthermore, due to inadequate time for expiration, there is a positive alveolar pressure at the end of expiration (PEEPi). This represents a further elastic workload for the inspiratory muscles. This impairment of ventilatory mechanics generates dyspnea that in most severely compromised patients occurs also for small efforts causing activity limitation and worst health-related quality of life (HRQoL). Due to these respiratory alterations, bronchodilators are the cornerstone of the long-term treatment of COPD in order to decrease airways resistances, lung hyperinflation and exacerbation rate, and improve patient's symptoms, exercise tolerance and health status. Long-acting antimuscarinic bronchodilators (LAMAs) have proven to be very useful in terms of lung deflation and exercise tolerance. Recently, new LAMAs with several positive characteristics have been introduced into clinical use among which glycopyrronium bromide has shown to be particularly effective. Glycopyrronium has a longer-lasting effect compared to other anticholinergic drugs, therefore it allows a single daily administration and facilitates the therapy of a disease that needs a chronic bronchodilation by decreasing the mechanic stress of the airways determined by repeated bronchoconstriction and increasing patient's adherence to treatment plan with better clinical results. Several studies demonstrated that glycopyrronium is able to positively and significantly decrease lung hyperinflation, symptoms, and improve psycho-physical status of COPD patients, with a low rate of adverse events, similar to that of placebo.

Respiratory complications in the pediatric postanesthesia care unit

This article focuses on common respiratory complications in the postanesthesia care unit (PACU). Approximately 1 in 10 children present with respiratory complications in the PACU. The article highlights risk factors and at-risk populations. The physiologic and pathophysiologic background and causes for respiratory complications in the PACU are explained and suggestions given for an optimization of the anesthesia management in the perioperative period. Furthermore, the recognition, prevention, and treatment of these complications in the PACU are discussed.

The effect of induction of anesthesia and intubation on end-expiratory lung level and regional ventilation distribution in cardiac children

BACKGROUND

During the induction of anesthesia, changes in functional residual capacity and ventilation distribution (VD) occur. Although these physiological changes are well investigated in adults, little data are available in infants and children.

AIM

To describe continuous changes in lung physiology during the induction of anesthesia in infants and children using electrical impedance tomography (EIT).

METHODS

Lung mechanics and volume changes in 38 infants and children undergoing elective cardiac surgery were assessed using EIT before, during, and after the induction of anesthesia. End-expiratory level (EEL as an equivalent to FRC) and VD were measured with EIT and referenced to a period of spontaneous breathing prior to induction.

RESULTS

EEL changed significantly during induction with the lowest during the intubation phase and normalized with the application of positive end-expiratory pressures (PEEP) after induction. Ventilation prior to induction was preferentially distributed toward the dependent lung, whereas after induction, the nondependent lung was better ventilated. PEEP during mechanical ventilation did not improve ventilation inhomogeneity.

CONCLUSION

Lung volume and mechanics deteriorate significantly during the induction of anesthesia and remain altered during mechanical ventilation.

Effects of sevoflurane and desflurane on respiratory mechanics after tracheal intubation in children

BACKGROUND

Tracheal intubation causes a reflex tracheal constriction that leads to increased airway resistance. Inhalation anesthetics can prevent or minimize this response. Therefore, this study was conducted to evaluate the effect of 1 MAC sevoflurane or desflurane on respiratory mechanics in children after anesthetic induction using propofol and tracheal intubation.

METHODS

Sixty children undergoing elective surgery with tracheal intubation were assigned into two groups at random, a 1 MAC concentration of sevoflurane (n = 30) and a desflurane (n = 30) group. Anesthesia was induced using propofol (1.5 mg/kg) and tracheal intubation was facilitated using rocuronium (0.6 mg/kg). A respiratory profile monitor was used to measure the respiratory resistance, dynamic compliance and peak inspiratory airway pressure. The measurements were made at three time points, after three inspirations from the beginning of mechanical ventilation (baseline) and at 5 and 10 min after the administration of inhalation anesthetics.

RESULTS

Sevoflurane and desflurane led to a significant decrease in respiratory resistance and increased dynamic compliance at 5 and 10 min when compared to baseline. There were no significant differences in respiratory resistance and dynamic compliance between the two groups.

CONCLUSIONS

A 1 MAC concentration of sevoflurane and desflurane has a similar bronchodilatory effect after tracheal intubation in children.

Salbutamol premedication in children with a recent respiratory tract infection

BACKGROUND

Premedication with beta-2 agonists (e.g. salbutamol) is effective in preventing increases in total respiratory resistance and in decreasing the incidence of perioperative bronchospasm in asthmatic children. Because children with recent respiratory tract infection (RTI) exhibit bronchial hyperreactivity similar to that observed in asthmatic children, the use of salbutamol in children with RTI has become popular among pediatric anesthetists for the prevention of perioperative respiratory adverse events (PRAE). In a prospective observational study, we therefore assessed the usefulness of salbutamol premedication on the occurrence of PRAE.

METHODS

Results from 600 children (0-16 years) undergoing general anesthesia were analyzed: 200 children with a recent RTI who received preoperative salbutamol 10-30 min prior to surgery, 200 children with a recent RTI without salbutamol premedication, and 200 children without a RTI during the last 4 weeks. All PRAE (laryngospasm, bronchospasm, oxygen desaturation [<95%], severe coughing) were recorded.

RESULTS

Children with a recent RTI who received salbutamol demonstrated a significantly reduced incidence of perioperative bronchospasm (5.5% vs 11%, P = 0.0270) and severe coughing (5.5% vs 11.5%, P = 0.0314) compared with children who had an RTI but did not receive salbutamol. However, healthy children presented with the lowest rate (bronchospasm 1.5%, severe coughing 4.5%) of respiratory complications compared with children with a recent RTI independent whether or not they received salbutamol preoperatively.

CONCLUSIONS

The results from this audit suggest that children with a history of a recent RTI have significantly less PRAE following a premedication with salbutamol compared with no premedication. Therefore, premedication with salbutamol might be considered in children with recent RTI.

A deeper level of ketamine anesthesia does not affect functional residual capacity and ventilation distribution in healthy preschool children

BACKGROUND

Ketamine is commonly used in children in the emergency setting and while undergoing diagnostic and therapeutic interventions because of its combination of hypnotic and analgesic properties. Although studies comparing various levels of ketamine anesthesia are lacking, previous work suggests that lung mechanics might only be minimally affected by ketamine.

METHODS

After approval from the Ethics Committee, anesthesia was induced with 2 mg.kg(-1) racemic ketamine followed by a continuous infusion of ketamine 2 mg.kg(-1) h(-1) (level I) in 26 children (2-6 years of age), and after 5 min, the first set of measurements was performed. Then, a second bolus of ketamine 2 mg.kg(-1) followed by ketamine 4 mg.kg(-1) h(-1) was administered (level II) and after 5 min, the second set of measurements was performed. Functional residual capacity (FRC) and lung clearance index (LCI) were calculated using a multibreath analysis by a blinded observer.

RESULTS

Functional residual capacity and LCI did not change between the two levels (FRC 25.6 [4.3] ml.kg(-1) vs 25.5 [4.2] ml.kg(-1), P=0.769, LCI 10.5 [1.2] vs 10.3 [1.1], P=0.403). The minute ventilation was similar between the two levels of anesthesia. The University of Michigan Sedation Scale increased from 3 (3) to 4 (3-4) at the second level of ketamine anesthesia.

CONCLUSIONS

A deeper level of anesthesia induced by ketamine does not affect FRC, ventilation distribution or minute ventilation suggesting that the depth of ketamine anesthesia has a minimal effect on pulmonary function.

Effects of glossopharyngeal pistoning for lung insufflation in elite swimmers

PURPOSE

To investigate whether sessions of glossopharyngeal pistoning (GP) to lung volumes exceeding maximum inspiratory capacity in a group of extremely well-trained elite swimmers would affect maximum lung volumes and buoyancies.

METHODS

Ten female and 16 male swimmers performed GP four times a week for 5 wk in addition to their regular swimming training program. Pulmonary function, chest expansion, hydrostatic weights (maximally inhaled and exhaled), and body composition (relative amounts of fat, bone, muscle, and fat-free tissue) were measured.

RESULTS

Training compliance was 79% for the males and 82% for the females. Chest expansion increased significantly during the training period, by 1.0 cm and by 0.8 cm at the level of the xiphiod and the fourth costae for the males, and by 0.6 cm and 0.8 cm for the females. The buoyancy lifting force increased significantly by 0.17 and 0.37 kg for the males and the females, respectively. The females also increased their vital capacity significantly by 2%. No significant changes in body composition took place in either group.

CONCLUSION

The lung volumes and buoyancies of swimmers can be increased by sessions of GP.

Prone equals prone? Impact of positioning techniques on respiratory function in anesthetized and paralyzed healthy children

OBJECTIVES

Although the prone position is effectively used to improve oxygenation, its impact on functional residual capacity is controversial. Different techniques of body positioning might be an important confounding factor. The aim of this study was to determine the impact of two different prone positioning techniques on functional residual capacity and ventilation distribution in anesthetized, preschool-aged children.

DESIGN

Functional residual capacity and lung clearance index, a measure of ventilation homogeneity, were calculated using a sulfur-hexafluoride multibreath washout technique. After intubation, measurements were taken in the supine position and, in random order, in the flat prone position and the augmented prone position (gel pads supporting the pelvis and the upper thorax).

SETTING

Pediatric anesthesia unit of university hospital.

PATIENTS AND PARTICIPANTS

Thirty preschool children without cardiopulmonary disease undergoing elective surgery.

MEASUREMENTS AND RESULTS

Mean (range) age was 48.5 (24-80) months, weight 17.2 (10.5-26.9) kg, functional residual capacity (mean +/- SD) 22.9+/- 6.2 ml.kg (-1) in the supine position and 23.3 +/- 5.6 ml.kg (-1) in the flat prone position, while lung clearance indices were 8.1 +/- 2.3 vs. 7.9 +/- 2.3, respectively. In contrast, functional residual capacity increased to 27.6 +/- 6.5 ml.kg (-1) (p< 0.001) in the augmented prone position while at the same time the lung clearance index decreased to 6.7 +/- 0.9 (p< 0.001).

CONCLUSIONS

Functional residual capacity and ventilation distribution were similar in the supine and flat prone positions, while these parameters improved significantly in the augmented prone position, suggesting that the technique of prone positioning has major implications for pulmonary function.

The Impact of Positive End-Expiratory Pressure on Functional Residual Capacity and Ventilation Homogeneity Impairment in Anesthetized Children Exposed to High Levels of Inspired Oxygen

BACKGROUND

High fractions of inspired oxygen (Fio2) result in resorption atelectasis shortly after their application. However, the impact of different levels of Fio2 and their interaction with positive end-expiratory pressure (PEEP) on functional residual capacity (FRC) and ventilation distribution is unknown in anesthetized children. We hypothesized that the use of a Fio2 of 1.0 results in a decrease of FRC and ventilation homogeneity compared with that of a Fio2 of 0.3, and that this decrease is prevented by PEEP of 6-cm H2O compared to a PEEP of 3-cm H2O.

METHODS

Forty-six children (3-6 yr) without cardiopulmonary disease were randomly allocated to receive PEEP of 6-cm H2O (PEEP 6 group) during the entire study period or PEEP of 3-cm H2O (PEEP 3 group). The order of the Fio2 (0.3 or 1.0) was also randomized. A defined recruitment maneuver was performed after tracheal intubation and 5 min later the first measurement. This procedure was then repeated with the second Fio2 level. FRC and lung clearance index (LCI) were calculated by a blinded observer.

RESULTS

While FRC (mean +/- sd) was similar at both levels of Fio2 (0.3: 25.6 +/- 2.9 mL/kg vs 1.0: 25.6 +/- 2.8 mL/kg, P = 0.189) in the PEEP 6 group, FRC decreased in the PEEP 3 group (0.3: 24.9 +/- 3.8 vs 1.0: 21.7 +/- 4.1, P < 0.0001). Furthermore, with continuous PEEP of 6-cm H2O a similar LCI was observed at both levels of Fio2 (0.3: 6.45 +/- 0.4 vs 6.43 +/- 0.4, P = 0.668) while LCI increased at the higher Fio2 in the PEEP 3 group (0.3: 6.5 +/- 0.5 vs 1.0: 7.7 +/- 1.2, P < 0.0001).

CONCLUSIONS

During the application of a very low PEEP of 3-cm H2O, FRC and ventilation distribution decreased significantly at an Fio2 of 1.0 compared with that at an Fio2 of 0.3. This decrease could be counterbalanced by the administration of PEEP of 6-cm H2O, indicating that a low level of PEEP is sufficient to maintain FRC and ventilation distribution regardless of the oxygen concentration.

Impact of Trendelenburg positioning on functional residual capacity and ventilation homogeneity in anaesthetised children

Trendelenburg positioning, a head-down tilt, is routinely used in anaesthesia when inserting a central venous catheter to increase the calibre of the jugular or subclavian veins and to prevent an air embolism. We investigated the impact of Trendelenburg positioning on functional residual capacity and ventilation homogeneity as well as the potential reversibility of these changes by repositioning and/or a recruitment manoeuvre in children with congenital heart disease. Functional residual capacity and ventilation homogeneity were assessed in 20 anaesthetised children between the ages of 3 months and 8 years who required central venous catheterisation before undergoing cardiac surgery. Functional residual capacity was measured (1) in the supine position, (2) in the Trendelenburg position, (3) after repositioning supine and (4) after a recruitment manoeuvre to total lung capacity which was performed by manually elevating the airway pressure to 40 cmH(2)O for ten consecutive breaths. Adopting the Trendelenburg position led to a significant decrease in functional residual capacity (median [range]- 12 (6-21)%) and increase in lung clearance index (12 (2-19)%). Baseline values were not reached after repositioning supine in any patient until after a standardised recruitment manoeuvre was performed.

Impact of depth of propofol anaesthesia on functional residual capacity and ventilation distribution in healthy preschool children

BACKGROUND

Propofol is commonly used in children undergoing diagnostic interventions under anaesthesia or deep sedation. Because hypoxaemia is the most common cause of critical deterioration during anaesthesia and sedation, improved understanding of the effects of anaesthetics on pulmonary function is essential. The aim of this study was to determine the effect of different levels of propofol anaesthesia on functional residual capacity (FRC) and ventilation distribution.

METHODS

In 20 children without cardiopulmonary disease mean age (SD) 49.75 (13.3) months and mean weight (SD) 17.5 (3.9) kg, anaesthesia was induced by a bolus of i.v. propofol 2 mg kg(-1) followed by an infusion of propofol 120 microg kg(-1) min(-1) (level I). Then, a bolus of propofol 1 mg kg(-1) was given followed by a propofol infusion at 240 microg kg(-1) min(-1) (level II). FRC and lung clearance index (LCI) were calculated at each level of anaesthesia using multibreath analysis.

RESULTS

The FRC mean (SD) decreased from 20.7 (3.3) ml kg(-1) at anaesthesia level I to 17.7 (3.9) ml kg(-1) at level II (P < 0.0001). At the same time, mean (SD) LCI increased from 10.4 (1.1) to 11.9 (2.2) (P = 0.0038), whereas bispectral index score values decreased from mean (SD) 57.5 (7.2) to 35.5 (5.9) (P < 0.0001).

CONCLUSIONS

Propofol elicited a deeper level of anaesthesia that led to a significant decrease of the FRC whereas at the same time the LCI, an index for ventilation distribution, increased indicating an increased vulnerability to hypoxaemia.

The effect of caudal block on functional residual capacity and ventilation homogeneity in healthy children*

Caudal block results in a motor blockade that can reduce abdominal wall tension. This could interact with the balance between chest wall and lung recoil pressure and tension of the diaphragm, which determines the static resting volume of the lung. On this rationale, we hypothesised that caudal block causes an increase in functional residual capacity and ventilation distribution in anaesthetised children. Fifty-two healthy children (15-30 kg, 3-8 years of age) undergoing elective surgery with general anaesthesia and caudal block were studied and randomly allocated to two groups: caudal block or control. Following induction of anaesthesia, the first measurement was obtained in the supine position (baseline). All children were then turned to the left lateral position and patients in the caudal block group received a caudal block with bupivacaine. No intervention took place in the control group. After 15 min in the supine position, the second assessment was performed. Functional residual capacity and parameters of ventilation distribution were calculated by a blinded reviewer. Functional residual capacity was similar at baseline in both groups. In the caudal block group, the capacity increased significantly (p < 0.0001) following caudal block, while in the control group, it remained unchanged. In both groups, parameters of ventilation distribution were consistent with the changes in functional residual capacity. Caudal block resulted in a significant increase in functional residual capacity and improvement in ventilation homogeneity in comparison with the control group. This indicates that caudal block might have a beneficial effect on gas exchange in anaesthetised, spontaneously breathing preschool-aged children with healthy lungs.

Twitch airway pressure elicited by magnetic phrenic nerve stimulation in anesthetized healthy children

Children with diaphragm dysfunction may be unable to maintain adequate ventilation. Accurate diagnosis is important, but can only be achieved using an appropriate test and reference range. The aim of this study, therefore, was to measure diaphragm contractility and examine the influence of age and maturation, using magnetic phrenic nerve stimulation in healthy children. Anterolateral magnetic stimulation (MS) of the phrenic nerves was performed using a 43-mm figure-eight coil in 23 children (14 male; mean age, 7.8 years; range, 1.8-15.7) anesthetized for minor surgery with sevoflurane gas. The airway was maintained with a cuffed laryngeal mask airway (LMA) which was briefly occluded during MS. Diaphragm contractility was assessed by measuring the airway pressure (TwPaw) elicited by MS. TwPaw responses were obtained in all subjects, with mean (SD) TwPaw 18.2 (6.8) cm H2O bilateral, 7.3 (3.2) cm H2O left unilateral, and 8.6 (3.1) cm H2O right unilateral. Subgroup analysis was performed in 17 of the children who were prepubertal. Their mean (SD) TwPaw was 17.3 (6.8) cm H2O bilateral, 7.1 (3.7) cm H2O left unilateral, and 8.3 (3.3) right unilateral. The mean (SD) intrapatient coefficients of variation for bilateral and left and right unilateral TwPaw were 8.4% (5.2), 6.7% (3.5), and 11.7% (10.3), respectively. Bilateral and left and right unilateral TwPaw were significantly related to age (P < 0.05). In healthy prepubertal children, diaphragm contractility is primarily influenced by age.

Assessment of lung volumes in children and adolescents: comparison of two plethysmographic techniques

Thoracic gas volume (Vtg) can be measured with body plethysmography by either repetitive panting or one single inspiratory effort against a shutter occluding the airways. The panting technique is preferred, but may be demanding. We aimed to assess the precision of these two methods and the degree of agreement between them. Vtg and functional residual capacity (FRC) were measured in 155 subjects with a standard, commercially available plethysmograph, acting as a variable-pressure, constant-volume device when Vtg is determined. Total lung capacity (TLC) and residual lung volume (RV) were calculated subsequent to a full vital capacity manoeuvre. For non-asthmatic healthy subjects, the standard deviations (SD) of the differences between two replicate measurements of FRC, TLC and RV were respectively 0.16, 0.13 and 0.14 litres with the panting technique, and 0.18, 0.18 and 0.23 litres with the single inspiratory effort technique. In percentage of the respective lung volumes, the corresponding 1.96 SDs were 20%, 8% and 40% with the panting technique and 23%, 12% and 67% with the single inspiratory effort technique. Between the two techniques, 95% limits of agreement were 21% for FRC, 11% for TLC and 58% for RV. The variability of Vtg and FRC accounted for most of the variability of TLC and RV. In conclusion, the panting and the single inspiratory effort technique produced results that were comparable in magnitude, however with a better precision with the panting technique. The single inspiratory effort technique can be used as an alternative if the panting technique fails.

Mechanics of Breathing after Surgical Ligation of Patent Ductus arteriosus in Newborns with Respiratory Distress Syndrome

The aim of the study was to detect changes in pulmonary function following ligation of a patent ductus arteriosus (PDA). Pulmonary function was recorded in 16 newborns (birth weight 1,081 +/- 166 g, gestational age 27.6 +/- 1.7 weeks) before and after ligation. No change in resistance of airways or mean airway pressure was observed. We found an increase in dynamic compliance (Cdyn) of 77% (p < 0.01), in tidal volume (TV) of 29% (p = 0.004), and in minute ventilation (MV) of 17% (p < 0.01) after the procedure. We demonstrated that pulmonary function improves after surgical ligation of the PDA. Because of considerable variation in intubated and spontaneously breathing premature newborns, we recommend the analysis of three main parameters: Cdyn, TV and MV for estimation of pulmonary mechanics in these infants.

Respiratory function in survivors of the United Kingdom Extracorporeal Membrane Oxygenation Trial

Extracorporeal membrane oxygenation (ECMO) improves survival in mature neonates with reversible lung disease. However, ECMO could result in survival of infants with severe respiratory dysfunction who would otherwise have died. Alternatively, infants receiving ECMO might be spared prolonged ventilation and consequent barotrauma, resulting in improved respiratory function. Our aim was to compare respiratory function at 1 yr of age in infants assigned to receive either ECMO or conventional management (CM). Seventy-eight surviving infants of the United Kingdom (UK) ECMO trial (51 in the ECMO group) were studied at 1 yr of age. Questionnaires provided details of respiratory symptoms, and laboratory measurements of respiratory function were made for respiratory rate, tidal volume, lung volume, airway conductance, specific airway conductance, and maximal expiratory flow at FRC (Vmax (FRC)). Data were exchanged on floppy disk for cross-analysis and to ensure that investigators were blinded to the status of the infants. There was a wide spectrum of respiratory function, from normal to markedly abnormal. There were few differences between the groups, but in the CM group lung volume was increased (95% confidence intervals [CIs] of the difference in ECMO versus CM subjects: -67; -4 ml), and inspiratory specific conductance was lower (95% CI: 0.03; 0.98 s(-)(1). kPa(-)(1)). There was a trend toward a lower V max(FRC) (95% CI: -2; 67 ml/s(-)(1) in the CM group. In addition to providing a survival advantage, ECMO did not worsen lung function in infants assigned to receive it. Indeed, their lung function appeared slightly better than that of infants treated conventionally.