Undetected Respiratory Depression in People with Opioid Use Disorder.

BACKGROUND: Opioid-related deaths are increasing globally. Respiratory complications of opioid use and underlying respiratory disease in people with Opioid Use Disorder (OUD) are potential contributory factors. Individual variation in susceptibility to overdose is, however, incompletely understood. This study investigated the prevalence of respiratory depression (RD) in OUD treatment and compared this to patients with chronic obstructive pulmonary disease (COPD) of equivalent severity. We also explored the contribution of opioid agonist treatment (OAT) dosage, and type, to the prevalence of RD. METHODS: There were four groups of participants: 1) OUD plus COPD ('OUD-COPD', n = 13); 2) OUD without COPD ('OUD', n = 7); 3) opioid-naïve COPD patients ('COPD'n = 13); 4) healthy controls ('HC'n = 7). Physiological indices, including pulse oximetry (SpO2%), end-tidal CO2 (ETCO2), transcutaneous CO2 (TcCO2), respiratory airflow and second intercostal space parasternal muscle electromyography (EMGpara), were recorded continuously over 40 min whilst awake at rest. Significant RD was defined as: SpO2%< 90% for > 10 s, ETCO2 per breath > 6.6 kPa, TcCO2 overall mean > 6 kPa, respiratory pauses > 10 s RESULTS: At least one indicator was observed in every participant with OUD (n = 20). This compared to RD episode occurrence in only 2/7 HC and 2/13 COPD participants (p < 0.05,Fisher's exact test). The occurrence of RD was similar in OUD participants prescribed methadone (n = 6) compared to those prescribed buprenorphine (n = 12). CONCLUSIONS: Undetected RD is common in OUD cohorts receiving OAT and is significantly more severe than in opioid-naïve controls. RD can be assessed using simple objective measures. Further studies are required to determine the association between RD and overdose risk.

COVID-19 infection in patients with intestinal failure: UK experience.

BACKGROUND: The direct effect of the coronavirus disease 2019 (COVID-19) pandemic on patients with intestinal failure (IF) has not been described. METHODS: We conducted a nationwide study of UK IF centers to evaluate the infection rates, presentations, and outcomes in patients with types 2 and 3 IF. RESULTS: A total of 45 patients with IF contracted COVID-19 between March and August 2020; this included 26 of 2191 (1.2%) home parenteral nutrition (HPN)-dependent adults and 19 of 298 (6.4%) adults hospitalized with type 2 IF. The proportion of patients receiving nursing care for HPN administration was higher in those with community-acquired COVID-19 (66.7%) than the proportion in the entire HPN cohort (26.1%; P < .01). Two HPN-dependent and 1 hospitalized patient with type 2 IF died as a direct consequence of the virus (6.7% of 45 patients with types 2 or 3 infected). CONCLUSION: This is the first study to describe the outcomes of COVID-19 in a large cohort of patients requiring long-term PN. Methods to reduce hospital and community nosocomial spread would likely be beneficial.

Measurement of neural respiratory drive via parasternal intercostal electromyography in healthy adult subjects.

Neural respiratory drive, quantified by the parasternal intercostal muscle electromyogram (EMGpara), provides a sensitive measure of respiratory system load-capacity balance. Reference values for EMGpara-based measures are lacking and the influence of individual anthropometric characteristics is not known. EMGpara is conventionally expressed as a percentage of that obtained during a maximal inspiratory effort (EMGpara%max), leading to difficulty in applying the technique in subjects unable to reliably perform such manoeuvres. To measure EMGpara in a large, unselected cohort of healthy adult subjects in order to evaluate relevant technical and anthropometric factors. Surface second intercostal space EMGpara was measured during resting breathing and maximal inspiratory efforts in 63 healthy adult subjects, median (IQR) age 31.0 (25.0-47.0) years, 28 males. Detailed anthropometry, spirometry and respiratory muscle strength were also recorded. Median (IQR EMGpara was 4.95 (3.35-6.93) µV, EMGpara%max 4.95 (3.39-8.65)% and neural respiratory drive index (NRDI, the product of EMGpara%max and respiratory rate) was 73.62 (46.41-143.92) %.breath/min. EMGpara increased significantly to 6.28 (4.26-9.93) µV (p < 0.001) with a mouthpiece, noseclip and pneumotachograph in situ. Median (IQR) EMGpara was higher in female subjects (5.79 (4.42-7.98) µV versus 3.56 (2.81-5.35) µV, p = 0.003); after controlling for sex neither EMGpara, EMGpara%max or NRDI were significantly related to anthropometrics, age or respiratory muscle strength. In subjects undergoing repeat measurements within the same testing session (n = 48) or on a separate occasion (n = 19) similar repeatability was observed for both EMGpara and EMGpara%max. EMGpara is higher in female subjects than males, without influence of other anthropometric characteristics. Reference values are provided for EMGpara-derived measures. Expressing EMGpara as a percentage of maximum confers no advantage with respect to measurement repeatability, expanding the potential application of the technique. Raw EMGpara is a useful marker of respiratory system load-capacity balance.

Three-dimensional ultrasound fetal lung volumes and infant respiratory outcome: a prospective observational study.

OBJECTIVE: To determine if fetal lung volumes (FLVs), determined by three-dimensional rotational ultrasound and virtual organ computer-aided analysis software (vocal), correlated with neonatal respiratory outcomes in surviving infants who had a high risk [fetuses with congenital diaphragmatic hernia (CDH)], lower risk [fetuses with anterior wall defects (AWDs)] and no risk (controls) of abnormal antenatal lung growth. DESIGN: Prospective observational study. SETTING: Tertiary fetal medicine and neonatal intensive care units. POPULATION: Sixty fetuses (25 with CDH, 25 with AWDs and ten controls). METHODS: FLVs were measured and expressed as the percentage of the observed compared with the expected for gestational age. MAIN OUTCOME MEASURES: Neonatal respiratory outcome was determined by the duration of supplemental oxygen, mechanical ventilation and dependencies, and assessment of lung volume using a gas dilution technique to measure functional residual capacity (FRC). RESULTS: The infants with CDH had lower FLV results than both the infants with AWDs (P=0.05) and the controls (P<0.05). The infants with CDH had longer durations of mechanical ventilation (P<0.001) and supplementary oxygen (P<0.001) dependence, compared with infants with AWDs. The infants with CDH had a lower median FRC than both the infants with AWDs (P<0.001) and the controls (P<0.001). FLV results correlated significantly with the durations of dependency on ventilation (r= -0.744, P<0.01) and oxygen (r= -0.788, P<0.001), and with FRC results (r=0.429, P=0.001). CONCLUSIONS: These results suggest that FLVs obtained using three-dimensional rotational ultrasound might be useful in predicting neonatal respiratory outcome in surviving infants who had varying risks of abnormal lung growth. Larger and more comprehensive studies are needed to clarify the role that lung volume measurements have in assessing lung function and growth.

Diaphragm electromyogram in infants with abdominal wall defects and congenital diaphragmatic hernia.

Measurement of the diaphragm electromyogram (EMGdi) elicited by phrenic nerve stimulation could be useful to assess neonates suffering from respiratory distress due to diaphragm dysfunction, as observed in infants with abdominal wall defects (AWD) or congenital diaphragmatic hernia (CDH). The study aims were to assess the feasibility of recording EMGdi using a multipair oesophageal electrode catheter and examine whether diaphragm muscle and/or phrenic nerve function was compromised in AWD or CDH infants. Diaphragm compound muscle action potentials elicited by magnetic phrenic nerve stimulation were recorded from 18 infants with surgically repaired AWD (n = 13) or CDH (n = 5), median (range) gestational age 36.5 (34-40) weeks. Diaphragm strength was assessed as twitch transdiaphragmatic pressure (TwP(di)). One AWD patient had prolonged phrenic nerve latency (PNL) bilaterally (left 9.31 ms, right 9.49 ms) and two CDH patients had prolonged PNL on the affected side (10.1 ms and 10.08 ms). There was no difference in left and right TwP(di) in either group. PNL correlated significantly with TwP(di) in CDH (r = 0.8; p = 0.009). Oesophageal EMG and magnetic stimulation of the phrenic nerves can be useful to assess phrenic nerve function in infants. Reduced phrenic nerve conduction accompanies the reduced diaphragm force production observed in infants with CDH.

Respiratory and laryngeal symptoms secondary to gastro-oesophageal reflux.

Gastro-oesophageal reflux may cause a range of laryngeal and respiratory symptoms. Mechanisms responsible include the proximal migration of gastric refluxate beyond the upper oesophageal sphincter causing direct irritation of the larynx and lower airway. Alternatively, refluxate entering the distal oesophagus alone may stimulate oesophageal sensory nerves and indirectly activate airway reflexes such as cough and bronchospasm. Recognising reflux as a cause for these extraoesophageal symptoms can be difficult as many patients do not have typical oesophageal symptoms (eg, heartburn) and clinical findings on laryngoscopy are not very specific. Acid suppression remains an effective treatment in the majority of patients but there is growing appreciation of the need to consider and treat non-acid and volume reflux. New opinions about the role of existing medical and surgical (laparoscopic techniques) treatment are emerging and a number of novel anti-reflux treatments are under development.

What is the value of ultrasound soft tissue measurements in the prediction of abnormal fetal growth?

Abnormal fetal growth increases the complications of pregnancy not only for the baby but also for the mother. Growth abnormalities also have lifelong consequences. These babies are at increased risk of insulin resistance, diabetes and hypertension later in life. It is important to identify these babies antenatally to optimise their clinical care. Although used extensively antenatally to monitor fetal growth, ultrasound has its limitations. Despite the use of more than 50 different formulae to estimate fetal weight, their performance has been poor at the extremes of fetal weight. Over the past 20 years there has been emerging interest in studying fetal soft tissue measurements to improve detection of growth abnormalities. This review paper outlines the value of soft tissue measurements in identifying fetal growth abnormalities, in estimating fetal weight and in managing diabetes mellitus in pregnancy.

Relation of exhaled nitric oxide levels to development of bronchopulmonary dysplasia.

OBJECTIVE: To test the hypothesis that exhaled nitric oxide levels on day 28 and changes in exhaled nitric oxide levels in the neonatal period would differ according to whether infants developed bronchopulmonary dysplasia (BPD) and its severity. DESIGN: Prospective observational study. SETTING: Tertiary neonatal intensive care unit. PATIENTS: 80 infants (median gestational age 28, range 24-32 weeks), 46 of whom developed BPD. INTERVENTIONS: Exhaled nitric oxide measurements were attempted on days 3, 5, 7, 14, 21 and 28. MAIN OUTCOME MEASURES: BPD (oxygen dependency at 28 days), mild BPD (oxygen dependent at 28 days, but not 36 weeks postmenstrual age (PMA)); moderate BPD (oxygen dependent at 36 weeks PMA) and severe BPD (respiratory support dependent at 36 weeks PMA). RESULTS: On day 28, exhaled nitric oxide levels were higher in infants with BPD compared to those without BPD (p<0.001) and there was a linear trend in exhaled nitric oxide results as BPD severity increased (p = 0.006). No significances in the change in exhaled nitric oxide levels over the neonatal period were found between the four groups. CONCLUSION: Exhaled nitric oxide levels are raised in infants with established BPD, particularly in those developing moderate or severe BPD, and may reflect ongoing inflammation.

Work of breathing during SIMV with and without pressure support.

OBJECTIVE: In a randomised trial, pressure support with synchronised intermittent mandatory ventilation (SIMV) compared to SIMV alone was associated with a significant reduction in supplementary oxygen duration. The hypothesis that the addition of pressure support to SIMV compared to SIMV alone would reduce the work of breathing was examined. DESIGN: Prospective study. SETTING: Perinatal service. PATIENTS: 20 infants, with a mean gestational age of 31 weeks, being weaned from mechanical ventilation were studied. INTERVENTIONS: 1 h periods of SIMV and SIMV with pressure support at 50% of the difference between the peak inflating pressure and positive end expiratory pressures. MAIN OUTCOME MEASURES: The work of breathing was assessed by measurement of the transdiaphragmatic pressure time product (PTPdi). RESULTS: The mean PTPdi on SIMV plus pressure support was 112 cm H(2)Oxs/min, approximately 20% lower than that on SIMV alone (141 cm H(2)Oxs/min) (p<0.001). CONCLUSION: The addition of pressure support to SIMV reduces the work of breathing in infants being weaned from the ventilator.

Sleeping position, oxygenation and lung function in prematurely born infants studied post term.

OBJECTIVE: To determine the effect of sleeping position on the lung function of prematurely born infants when post term, whether any effect was similar to that before discharge from the neonatal unit, and if it differed according to bronchopulmonary (BPD) status. DESIGN: Prospective study. SETTING: Tertiary neonatal unit. PATIENTS: Twenty infants, median gestational age 30 weeks (range 25-32); 10 had BPD. INTERVENTIONS: Before neonatal unit discharge (median age 36 weeks postmenstrual age (PMA)) and when post term, infants were studied prone and supine, each position maintained for 3 h. MAIN OUTCOME MEASURES: Oxygen saturation was monitored continuously and, at the end of each 3 h period, functional residual capacity (FRC) and compliance (CRS) and resistance (RRS) of the respiratory system were measured. RESULTS: At a median of 36 weeks PMA and 6 weeks later (post term), respectively, oxygen saturation (98% vs 96%, p = 0.001; 98% vs 97%, p = 0.011), FRC (26 vs 24 ml/kg, p<0.0001; 35 vs 31 ml/kg, p = 0.001) and CRS (3.0 vs 2.4 ml/cm H(2)O, p = 0.034; 3.7 vs 2.5 ml/cm H(2)O, p = 0.015) were higher in the prone than the supine position. In the prone position, both BPD and non-BPD infants had significantly greater FRCs on both occasions and oxygen saturation at 36 weeks PMA, but oxygen saturation was significantly better post term only in non-BPD infants. Twelve infants had superior oxygen saturation and 17 superior FRCs in the prone compared with the supine position at both 36 weeks PMA and post term. CONCLUSIONS: These results suggest that lung function impairment does not explain why prematurely born infants are at increased risk of sudden infant death syndrome in the prone compared with the supine position.

Ultrasound measurement of rectus femoris cross-sectional area and the relationship with quadriceps strength in COPD.

BACKGROUND: Quadriceps weakness and loss of muscle mass predict mortality in chronic obstructive pulmonary disease (COPD). It was hypothesised that a reduced quadriceps cross-sectional area could be detected by ultrasound in patients with COPD compared with healthy subjects, and that measurements relate to strength and fat-free mass (FFM). METHODS: Rectus femoris muscle cross-sectional area (RF(CSA)) was measured by ultrasound and whole-body FFM estimated using electrical bioimpedance. Quadriceps strength was measured by maximum voluntary contraction and twitch tension (TwQ) following magnetic femoral nerve stimulation. RESULTS: 26 healthy volunteers of mean (SD) age 63 (9) years and 30 patients with COPD of mean (SD) age 67 (9) years and percentage predicted forced expiratory volume in 1 s (FEV(1)) 48.0 (20.8)% with a similar FFM (46.9 (9.3) kg vs 46.1 (7.3) kg, p = 0.193) participated in the study. Mean RF(CSA) was reduced in patients with COPD by 25% of the mean value in healthy subjects(-115 mm(2); 95% CI -177 to -54, p = 0.001) and was related to MRC dyspnoea scale score, independent of FFM or sex. Maximum voluntary contraction strength was linearly related to RF(CSA) in patients with COPD (r = 0.78, p<0.001). TwQ force per unit of RF(CSA) was similar in both healthy individuals and those with COPD (mean (SD) 17 (4) g/mm(2) vs 18 (3) g/mm(2), p = 0.657). Voluntary contraction strength per unit of RF(CSA) was dependent on central quadriceps activation and peripheral oxygen saturation in COPD. CONCLUSION: Ultrasound measurement of RF(CSA) is an effort-independent and radiation-free method of measuring quadriceps muscle cross-sectional area in patients with COPD that relates to strength.

Neural respiratory drive in healthy subjects and in COPD.

The aim of the present study was to use the diaphragm electromyogram (EMG(di)) to compare levels of neural respiratory drive (NRD) in a cohort of healthy subjects and chronic obstructive pulmonary disease (COPD) patients, and to investigate the relationship between NRD and pulmonary function in COPD. EMG(di) was recorded at rest and normalised to peak EMG(di) recorded during maximum inspiratory manoeuvres (EMG(di) % max) in 100 healthy subjects and 30 patients with COPD, using a multipair oesophageal electrode. EMG(di) was normalised to the amplitude of the diaphragm compound muscle action potential (CMAP(di,MS)) in 64 healthy subjects. The mean+/-sd EMG(di) % max was 9.0+/-3.4% in healthy subjects and 27.9+/-9.9% in COPD patients, and correlated with percentage predicted forced expiratory volume in one second, vital capacity and inspiratory capacity in patients. EMG(di) % max was higher in healthy subjects aged 51-80 yrs than in those aged 18-50 yrs (11.4+/-3.4 versus 8.2+/-2.9%, respectively). Observations in the healthy group were similar when peak EMG(di) or CMAP(di,MS) were used to normalise EMG(di). Levels of neural respiratory drive were higher in chronic obstructive pulmonary disease patients than healthy subjects, and related to disease severity. Diaphragm compound muscle action potential could be used to normalise diaphragm electromyogram if volitional inspiratory manoeuvres could not be performed, allowing translation of the technique to critically ill and ventilated patients.

Transcranial magnetic stimulation study of expiratory muscle weakness in acute ischemic stroke.

BACKGROUND: Expiratory muscle weakness due to cerebral infarction may contribute to reduced airway clearance in stroke patients. METHODS: Transcranial magnetic stimulation (TMS) at the vertex and over each hemisphere and magnetic stimulation over the T(10-11) spinal roots (Tw T(10)) and the phrenic nerves bilaterally (BAMPS) were performed in 15 acute ischemic stroke patients (age 68.9 +/- 9.8 years) and 16 matched controls. Surface electrodes recorded motor evoked potentials (MEPs) in the rectus abdominis (RA) and external oblique (EO) muscles bilaterally. Respiratory muscle function was assessed by measuring maximum static expiratory pressure (PE(max)) and changes in intragastric (P(gas)) and transdiaphragmatic (P(di)) pressure after voluntary cough, TMS, TwT(10), and BAMPS. Regression models were used to assess determinants of peak voluntary cough flow rates (PCFR). RESULTS: PCFR, cough P(gas), and vertex TMS P(gas) were decreased in stroke patients compared with controls (203.6 +/- 151.1 vs 350.8 +/- 111.7 L/min, p = 0.004; 72.7 +/- 64.5 vs 163.4 +/- 55.8 cm H(2)O, p = 0.0003 and 8.7 +/- 3.3 vs 16.7 +/- 11.5 cm H(2)O, p = 0.023, respectively). There were no differences in TwT(10) P(gas) (25.2 +/- 7.8 vs 29.4 +/- 12.4 cm H(2)O, p = 0.153) or BAMPS P(di) (21.6 +/- 7.2 vs 19.2 +/- 3.4 cm H(2)O, p = 0.163). TMS P(gas) was lower (4.1 +/- 2.8 vs 6.1 +/- 1.9 cm H(2)O, p = 0.023) following TMS of the injured compared with the uninjured hemisphere in stroke patients. Age and gender adjusted PCFR correlated with P(gas) (r = 0.51, p = 0.009) and PE(max) (r = 0.46, p = 0.024). Stroke was an independent determinant of PCFR after adjusting for P(gas) and PE(max) (p = 0.031). CONCLUSION: Ischemic cortical injury is associated with expiratory muscle weakness and may contribute to cough impairment in stroke patients.

Sleep-disordered breathing in unilateral diaphragm paralysis or severe weakness.

Few data exist concerning sleep in patients with hemidiaphragm paralysis or weakness. Traditionally, such patients are considered to sustain normal ventilation in sleep. In the present study, diaphragm strength was measured in order to identify patients with unilateral paralysis or severe weakness. Patients underwent polysomnography with additional recordings of the transoesophageal electromyogram (EMG) of the diaphragm and surface EMG of extra-diaphragmatic respiratory muscles. These data were compared with 11 normal, healthy subjects matched for sex, age and body mass index (BMI). In total, 11 patients (six males, mean+/-sd age 56.5+/-10.0 yrs, BMI 28.7+/-2.8 kg x m(-2)) with hemidiaphragm paralysis or severe weakness (unilateral twitch transdiaphragmatic pressure 3.3+/-1.7 cmH(2)O (0.33+/-0.17 kPa) were studied. They had a mean+/-sd respiratory disturbance index of 8.1+/-10.1 events x h(-1) during non-rapid eye movement (NREM) sleep and 26.0+/-17.8 events x h(-1) during rapid eye movement (REM) sleep (control groups 0.4+/-0.4 and 0.7+/-0.9 events x h(-1), respectively). The diaphragm EMG, as a percentage of maximum, was double that of the control group in NREM sleep (15.3+/-5.3 versus 8.9+/-4.9% max, respectively) and increased in REM sleep (20.0+/-6.9% max), while normal subjects sustained the same level of activation (6.2+/-3.1% max). Patients with unilateral diaphragm dysfunction are at risk of developing sleep-disordered breathing during rapid eye movement sleep. The diaphragm electromyogram, reflecting neural respiratory drive, is doubled in patients compared with normal subjects, and increases further in rapid eye movement sleep.

Peak expiratory flow in Afro-Caribbean children with and without sickle cell anaemia.

AIMS: To create a reference range of peak expiratory flow (PEF) results of Afro-Caribbean children and determine whether interpretation of PEF results in children with sickle cell anaemia (SCA) differed according to whether comparison was made of results obtained from children of similar age or height. METHODS: A prospective observational study was carried out in two specialist sickle cell disease clinics. Seventy-eight nonasthmatic African and Caribbean (AC) controls (age range 2.6-17.8 years), and 99 nonasthmatic SCA children (age range 3.4-17.3 years) were recruited. PEF was measured using a dry rolling sealed spirometer before and after bronchodilator therapy. RESULTS: PEF results in the AC controls correlated with height (r = 0.88, p< 0.0001). Comparison of similarly aged children demonstrated that pre- (p = 0.02) and post- (p = 0.04) bronchodilator PEF results were lower in the SCA children, but comparison of children of similar height revealed no statistically significant differences in PEF results between children with SCA and controls. The SCA children tended to be shorter than the controls. CONCLUSION: The results suggest PEF measurements are not a useful method of monitoring the respiratory status of children with sickle cell disease.

Diaphragm electromyograms recorded from multiple surface electrodes following magnetic stimulation.

The diaphragm compound-muscle action potential (CMAPdi), elicited by unilateral magnetic stimulation (UMS) of the phrenic nerve can be recorded using surface electrodes. However, there is no consensus on the best positioning of surface electrodes and there are no data on the reproducibility of the signal. Using 36 surface electrode pairs, in five healthy subjects, the CMAPdi elicited by UMS and electrical stimulation (ES) were compared and 12 pairs were identified as providing acceptable signals. The latency and amplitude were measured for each CMAPdi, following UMS at 60-100% of maximal stimulator output, in 12 healthy subjects, on two occasions. Latencies obtained using UMS and ES ranged between 6.1-7.33 and 6.25-7.17 ms, respectively. Optimum CMAPdi were not recorded from the same electrode pair in all subjects, or for both hemidiaphragms in each subject. However, the optimal recording site for a particular individual remained unchanged on subsequent testing. When recorded from the optimal site, latencies and amplitudes of CMAPdi elicited on the two occasions were not significantly different. The current study suggests that the use of multiple chest wall electrodes can identify an optimal electrode pair, from which it is possible to obtain reproducible compound-muscle action potential signals.

Respiratory function of very prematurely born infants at follow up: influence of sex.

OBJECTIVE: To test the hypothesis that male compared with female prematurely born infants would have worse lung function at follow up. DESIGN: Prospective follow up study. SETTING: Tertiary neonatal intensive care units PATIENTS: Seventy six infants, mean (SD) gestational age 26.4 (1.5) weeks, from the United Kingdom oscillation study. INTERVENTIONS: Lung function measurements at a corrected age of 1 year. MAIN OUTCOME MEASURES: Airways resistance (Raw) and functional residual capacity (FRC(pleth)) measured by whole body plethysmography, specific conductance (sGaw) calculated from Raw and FRC(pleth), and FRC measured by a helium gas dilution technique (FRC(He)). RESULTS: The 42 male infants differed significantly from the 34 female infants in having a lower birth weight for gestation, requiring more days of ventilation, and a greater proportion being oxygen dependent at 36 weeks postmenstrual age and discharge. Furthermore, mean Raw and FRC(pleth) were significantly higher and mean sGaw significantly lower. After adjustment for birth and current size differences, the sex differences in FRC(pleth) and sGaw were 15% and 26% respectively and remained significant. CONCLUSION: Lung function at follow up of prematurely born infants is influenced by sex.

Plethysmograph and interrupter resistance measurements in prematurely born young children.

BACKGROUND: Airways obstruction in premature infants is often assessed by plethysmography, which requires sedation. The interrupter (Rint) technique does not require sedation, but has rarely been examined in children under 2 years of age. OBJECTIVE: To compare Rint results with plethysmographic measurements of airway resistance (Raw) in prematurely born, young children. DESIGN: Prospective study. SETTING: Infant and Paediatric Lung Function Laboratories. PATIENTS: Thirty children with a median gestational age of 25-29 weeks and median postnatal age of 13 months. INTERVENTIONS AND MAIN OUTCOME MEASURES: The infants were sedated, airway resistance was measured by total body plethysmography (Raw), and Rint measurements were made using a MicroRint device. Further Raw and Rint measurements were made after salbutamol administration if the children remained asleep. RESULTS: Baseline measurements of Raw and Rint were obtained from 30 and 26 respectively of the children. Mean baseline Rint values were higher than mean baseline Raw results (3.45 v 2.84 kPa/l/s, p = 0.006). Limits of agreement for the mean difference between Rint and Raw were -1.52 to 2.74 kPa/l/s. Ten infants received salbutamol, after which the mean Rint result was 3.6 kPa/l/s and mean Raw was 3.1 kPa/l/s (limits of agreement -0.28 to 1.44 kPa/l/s). CONCLUSION: The poor agreement between Rint and Raw results suggests that Rint measurements cannot substitute for plethysmographic measurements in sedated prematurely born infants.

Diminished lung function, RSV infection, and respiratory morbidity in prematurely born infants.

BACKGROUND: Diminished lung function appears to be a risk factor for respiratory syncytial virus (RSV) infection/bronchiolitis in term born infants. AIMS: To determine if diminished lung function prior to neonatal unit discharge was associated with subsequent symptomatic RSV lower respiratory tract infection (LRTI) and respiratory morbidity in prematurely born infants. METHODS: Of 39 infants in a tertiary neonatal intensive care unit (median gestational age 28 weeks, range 23-31), 20 had bronchopulmonary dysplasia. Lung function (compliance and resistance of the respiratory system (C(rs) and R(rs)) and functional residual capacity (FRC)) was measured on the neonatal unit at 36 weeks postmenstrual age (PMA). Following neonatal unit discharge, nasopharyngeal aspirates were obtained on every occasion, at home or in hospital, an infant had an LRTI. RSV was identified by immunofluorescence and/or culture. RESULTS: The 15 infants who suffered a symptomatic RSV LRTI had a higher mean R(rs) and suffered more wheeze at follow up than the rest of the cohort. Regression analysis showed that a high R(rs) was significantly associated with a symptomatic RSV LRTI; significant factors for cough were a high R(rs) and a symptomatic RSV LRTI, and for wheeze were a high R(rs). CONCLUSION: Prematurely born infants, who had a symptomatic RSV LRTI and/or respiratory morbidity at follow up, had worse lung function prior to neonatal unit discharge.