Continuous Positive Airway Pressure Support Research Articles

Oxygen Saturation Targeting in Preterm Infants Receiving Continuous Positive Airway Pressure

The precision of oxygen saturation (SpO2) targeting in preterm infants on continuous positive airway pressure (CPAP) is incompletely characterized. We therefore evaluated SpO2 targeting in infants solely receiving CPAP, aiming to describe their SpO2 profile, to document the frequency of prolonged hyperoxia and hypoxia episodes and of fraction of inspired oxygen (FiO2) adjustments, and to explore the relationships with neonatal intensive care unit operational factors. Preterm infants <37 weeks' gestation in 2 neonatal intensive care units were studied if they were receiving CPAP and in supplemental oxygen at the beginning of each 24-hour recording. SpO2, heart rate, and FiO2 were recorded (sampling interval 1-2 seconds). We measured the proportion of time spent in predefined SpO2 ranges, the frequency of prolonged episodes (≥30 seconds) of SpO2 deviation, and the effect of operational factors including nurse-patient ratio. A total of 4034 usable hours of data were recorded from 45 infants of gestation 30 (27-32) weeks (median [IQR]). When requiring supplemental oxygen, infants were in the target SpO2 range (88%-92%) for only 31% (19%-39%) of total recording time, with 48 (6.9-90) episodes per 24 hours of severe hyperoxia (SpO2 ≥98%), and 9.0(1.6-21) episodes per 24 hours of hypoxia (SpO2 <80%). An increased frequency of prolonged hyperoxia in supplemental oxygen was noted when nurses were each caring for more patients. Adjustments to FiO2 were made 25 (16-41) times per day. SpO2 targeting is challenging in preterm infants receiving CPAP support, with a high proportion oftime spent outside the target range and frequent prolonged hypoxic and hyperoxic episodes.

Bubble CPAP: An Alternative That Is as Good as it Gets!

Source: Tagare A, Kadam S, Vaidya U, et al. Bubble CPAP versus ventilator CPAP in preterm neonates with early onset respiratory distress - a randomized controlled trial. J Trop Pediatr. 2013; 59(2): 113– 119; doi: 10.1093/tropej/fms061Researchers from India and Australia compared the safety and efficacy of bubble (B) continuous positive airway pressure (CPAP) with ventilator-derived CPAP (VCPAP) in preterm infants. They conducted a randomized controlled trial and enrolled infants at <37 weeks gestation who developed respiratory distress within 6 hours of birth. Only infants who had an oxygen requirement of >30% and who had at least moderate retractions and/or grunting as determined by a Silverman-Anderson (SA) score >4 (range of possible scores 0–10) were eligible for enrollment. At enrollment, study infants were randomized to BCPAP or VCPAP. Commercial brand equipment was used for both groups, including a bubble generator and blender for BCPAP, ventilator equipment for VCPAP, and nasal prongs. Both groups were started on 40% FiO2 and a CPAP pressure of 6 cm of water (cmW). Based on clinical assessment and a goal of maintaining an oxygen saturation of 88% to 93%, FiO2 was changed in increments of 5% and CPAP in increments of 1 cmW. After 1 hour of CPAP support, surfactant replacement was administered to infants requiring ≥40% FiO2, ≥6 cmW CPAP, and having x-ray findings consistent with respiratory distress syndrome (RDS).The primary study outcome was success of the allocated ventilation method. Success was defined as discontinuation of CPAP within 72 hours and no need for mechanical ventilation, oxygen requirement of <30%, and an SA score <3. Secondary outcomes included need for surfactant therapy, nasal injury from CPAP, and overall mortality.One hundred and fourteen infants were enrolled, with 57 in each group. The groups were comparable at baseline with respect to gestational age, birth weight, and SA score.Neonates treated with BCPAP were significantly more likely to have successful treatment than those randomized to VCPAP (82.5% and 63.2%, respectively, P = .3). Surfactant was given to more infants in the VCPAP than BCPAP group (18/57 vs 9/57, P < .05). Overall, infants who required surfactant were significantly less likely to have successful CPAP treatment, regardless of type of CPAP. VCPAP and BCPAP groups were comparable in terms of CPAP duration (30 hours and 36 hours, respectively) and mortality (8.8% and 7%, respectively). Injury to the nasal septum was more frequent in infants randomized to BCPAP (21.1%) than to those receiving VCPAP (7%) (P = .03).The authors conclude that BCPAP is safe and more effective than VCPAP when used early for preterm neonates with moderate to severe RDS.Drs Santisteban-Ponce and Bedrick have disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.CPAP emerged in 1971 as an alternative to mechanical ventilation for preterm infants with RDS, reducing the need for intubation.1 CPAP regained popularity with the increased survival of very low birth weight (VLBW) infants, decreasing the incidence of chronic lung disease through its use with many modalities, including endotracheal tube and mechanical ventilator, or the nasal route with a flow-driver CPAP or BCPAP.2BCPAP delivers a pressurized flow of humidified gas through a breathing circuit with nasal prongs. The pressure delivered is controlled by adjusting the depth of a partially submerged tube in a water bottle (depth of 1 cm equals 1 cm of H2O pressure) attached to the end of the infant’s breathing circuit.3 The bubbling of BCPAP generates a small airway pressure oscillation, which is thought to reduce the work of breathing, improve gas exchange, and facilitate alveolar recruitment. BCPAP airway pressure waveforms are similar to those produced by high frequency oscillatory ventilation.3 It is a simple, low-cost apparatus.Studies in VLBW infants treated with BCPAP in the delivery room noted decreased intubations and fewer days on mechanical ventilation. 2,4 BCPAP has been shown to enhance alveolar gas exchange in premature infants compared to VCPAP.3 BCPAP has also been effective in maintaining spontaneous breathing following extubation of newborns and in treating apnea of prematurity, addressing multiple respiratory needs of premature infants.The use of BCPAP in developing countries could be expected to decrease health care costs for the treatment of neonatal RDS, as has been described in resource-rich environments.5 Many nasal septum injuries could be prevented by using experienced nurses.6 The results of the current study support the observation that less invasive respiratory therapy strategies can be successfully used in resource-limited areas, reducing demand for ventilators and exogenous surfactant. The application of respiratory support devices that are user-friendly, inexpensive, and effective for treatment of large numbers of premature babies is as good as it gets!

Less Invasive Surfactant Administration (LISA) — Ways to deliver surfactant in spontaneously breathing infants

The idea to deliver surfactant to spontaneously breathing premature infants is not new. The spectrum of methods reported reaches from aerosol administration over pharyngeal deposition, the use of laryngeal masks, short term intubation, surfactant administration and rapid extubation (INSURE) to an approach of keeping premature neonates on spontaneous breathing with continuous positive airway pressure support and administering surfactant by laryngoscopy via a small diameter tube. This way of Less Invasive Surfactant Administration (LISA) is in increasing use in the last decade in Germany. More than 1000 babies have been included in clinical studies on LISA by now. A first prospective randomized controlled trial (AMV-trial) demonstrated a significant reduction in the use of mechanical ventilation in LISA patients compared to standard treatment with intratracheal bolus administration of surfactant. Another recent study (Take Care study) indicates, that LISA may even be superior to INSURE. The search for even more “gentle” methods (e.g. nebulization) to deliver surfactant continues.

The Effect of Flow Trigger on Rapid Shallow Breathing Index Measured Through the Ventilator

The rapid shallow breathing index (RSBI) has the best predictive value to assess readiness for weaning from mechanical ventilation. At many institutions, this index is conveniently measured without disconnecting the patient from the ventilator, but this method may be inaccurate. Because modern ventilators have a base flow in the flow trigger mode that may provide a substantial help to the patient, we hypothesized that the RSBI is significantly decreased when measured through the ventilator with flow trigger even without continuous positive airway pressure (CPAP) and pressure support (PS). The RSBI was calculated using the values of minute ventilation and respiratory rate obtained either through the digital display of the ventilator or from a digital ventilometer. The RSBI was measured using 3 different methods: method 1, CPAP and PS both 0 cm H2O with flow trigger; method 2, CPAP and PS both 0 cm H2O without flow trigger; and method 3, using digital ventilometer. A total of 165 measurements per method were obtained in 80 adult patients in the medical intensive care unit (MICU). The RSBI (breaths/min/L) values were 70.2 ± 26.5 with method 1, 85.4 ± 30.3 with method 2, and 80.1 ± 30.3 with method 3. The RSBI was significantly decreased using mechanical ventilation with flow trigger as compared with mechanical ventilation without flow trigger (P < .0001) or digital ventilometer (P < .0001). When method 1 was compared with methods 2 and 3, the RSBI decreased by 17% and 12%, respectively. The RSBI measurement is significantly decreased by the base flow delivered through modern ventilators in the flow trigger mode. If RSBI is measured through the ventilator in the flow trigger mode, the difference should be considered when using RSBI to assess readiness for weaning from mechanical ventilation.

Index of Suspicion in the Nursery

A 2,160-g term female is born to a 24-year-old G2P0010 mother. Pregnancy complications include iron-deficiency anemia; intrauterine growth restriction diagnosed by using a prenatal ultrasound during the third trimester; positive serologic result for maternal herpes simplex, with no active lesions present at delivery; and vaginal culture positive for group B Streptococcus . All other serologic test results were unremarkable. Before delivery, the mother received valacyclovir and multiple doses of penicillin. The infant was born at a community hospital via induced vaginal delivery due to intrauterine growth restriction status, without prolonged rupture of membranes. Apgar scores are 9 and 9 at 1 and 5 minutes, respectively. Physical examination at birth demonstrates the infant is small for gestational age but is otherwise within normal limits. Weight at birth is 2,160 g and length is 43.2 centimeters, both below the third percentile for gestational age and gender, and head circumference is 33.5 centimeters (15th percentile). On day 2, just before discharge, the infant is noted to be hypothermic (93°F) and hypoglycemic. She is transferred to the NICU of the community hospital and undergoes a partial sepsis evaluation, including blood, urine, and surface viral cultures. Presumptive treatment for clinical sepsis is initiated with ampicillin, gentamicin, and acyclovir. Subsequently, the infant is noted to have evidence of respiratory distress and requires continuous positive airway pressure support. An arterial blood gas sample is obtained, with the following results: pH, 7.1; Pco2, 9 mm Hg; bicarbonate, 7 mmol/L; and base excess, –25 mmol/L. She receives a 2-mEq/kg sodium bicarbonate bolus, and a repeat arterial blood gas sample shows a pH of 7.3, Pco2 of 15 mm Hg, and base excess of –20 mmol/L. Lactate levels are within normal limits, but ammonia levels are elevated to >400 μmol/L, and 3 hours later they increase …

Analysis of Routine Intensive Care Unit Admission following Fronto-Orbital Advancement for Craniosynostosis

Intensive care unit admission following fronto-orbital advancement for craniosynostosis is routine at most institutions. The authors determined the frequency of postoperative events requiring intensive care unit care that justify this practice. Infants with craniosynostosis who underwent primary fronto-orbital advancement at a single institution from 1997 to 2011 were included. Patient demographics, operative factors, and hemodynamic outcomes were recorded. Adverse postoperative events/interventions were graded as none (group I); minor (group II), easily managed on a surgical floor; or major (group III), requiring intensive care unit care. One hundred seven infants were included. Average length of hospitalization was 3.7 ± 1.6 days, with 1.3 ± 1.0 days in the intensive care unit and 2.4 ± 1.0 days on the floor. Seventy-eight patients (72.9 percent) were categorized into group I, 24 (22.4 percent) into group II, and five (4.7 percent) into group III. Major events/interventions included prolonged intubation (n = 2), reintubation (n = 2), and continuous positive airway pressure support (n = 1). Preexisting end-organ dysfunction was significantly associated with group III patients, who also had significantly higher intraoperative blood loss requiring greater resuscitation. Mean daily charges were $7652.33 (10.9 percent of total charges) for intensive care unit care and $2470.62 (6.9 percent of total charges) for floor care. In this study, 4.7 percent of patients had event/interventions requiring intensive care unit care after fronto-orbital advancement. Predictors included preexisting end-organ dysfunction and higher intraoperative blood loss requiring greater resuscitation. Financial savings from selective postoperative intensive care unit admission may not outweigh the potential cost of an emergent event on the surgical floor.

A pilot cohort analytic study of Family Integrated Care in a Canadian neonatal intensive care unit

BackgroundWe have developed a Family Integrated Care (FIC) model for use in a neonatal intensive care unit (NICU) where parents provide most of the care for their infant, while nurses teach and counsel parents. The objective of this pilot prospective cohort analytic study was to explore the feasibility, safety, and potential outcomes of implementing this model in a Canadian NICU.MethodsInfants born ≤35 weeks gestation, receiving continuous positive airway pressure or less respiratory support, with a primary caregiver willing and able to spend ≥8 hours a day with their infant were eligible. Families attended daily education sessions and were mentored at the bedside by nurses. The primary outcome was weight gain, as measured by change in z-score for weight 21 days after enrolment. For each enrolled infant, we identified two matched controls from the previous year’s clinical database. Differences in weight gain between the two groups were analyzed using a linear mixed effects multivariable regression model. We also measured parental stress levels using the Parental Stress Survey: NICU, and interviewed parents and nurses regarding their experiences with FIC.ResultsThis study included 42 mothers and their infants. Of the enrolled infants, matched control data were available for 31 who completed the study. The rate of change in weight gain was significantly higher in FIC infants compared with control infants (p < 0.05). There was also a significant increase in the incidence of breastfeeding at discharge (82.1 vs. 45.5%, p < 0.05). The mean Parental Stress Survey: NICU score for FIC mothers was 3.06 ± 0.12 at enrolment, which decreased significantly to 2.30 ± 0.13 at discharge (p < 0.05). Feedback from the parents and nurses indicated that FIC was feasible and appropriately implemented.ConclusionsThis study suggests that the FIC model is feasible and safe in a Canadian healthcare setting and results in improved weight gain among preterm infants. In addition, this innovation has the potential to improve other short and long-term infant and family outcomes. A multi-centre randomized controlled trial is needed to further evaluate the efficacy of FIC in the Canadian context.

Enhancement of Cardiac Performance by Bilevel Positive Airway Pressure Ventilation in Heart Failure

BackgroundRecent studies have reported the clinical usefulness of positive airway pressure ventilation therapy with various kinds of pressure support compared with simple continuous positive airway pressure (CPAP) for heart failure patients. However, the mechanism of the favorable effect of CPAP with pressure support can not be explained simply from the mechanical aspect and remains to be elucidated. Methods and ResultsIn 18 stable chronic heart failure patients, we performed stepwise CPAP (4, 8, 12 cm H2O) while the cardiac output and intracardiac pressures were continuously monitored, and we compared the effects of 4 cm H2O CPAP with those of 4 cm H2O CPAP plus 5 cm H2O pressure support. Stepwise CPAP decreased cardiac index significantly in patients with pulmonary arterial wedge pressure (PAWP) <12 mm Hg (n = 10), but not in those with PAWP ≥12 mm Hg (n = 8). Ventilation with CPAP plus pressure support increased cardiac index slightly but significantly from 2.2 ± 0.7 to 2.3 ± 0.7 L min−1 m−2 (P = .001) compared with CPAP alone, regardless of basal filling condition or cardiac index. ConclusionsOur results suggest that CPAP plus pressure support is more effective than simple CPAP in heart failure patients and that the enhancement might be induced by neural changes and not simply by alteration of the preload level.

Obstructive sleep apnea can be safely managed in a level 2 critical care setting after laparoscopic bariatric surgery

BackgroundIn the United Kingdom, demand for intensive care beds (level 3 critical care) often outstrips supply, leading to frequent and frustrating cancellation of complex elective surgery. It has been suggested that patients with obstructive sleep apnea who undergo bariatric surgery should be admitted to a level 3 facility for routine postoperative management. We have questioned the validity of this dogma in the era of laparoscopic bariatric surgery by using a simple easily applicable algorithm. ObjectivesThe aim of this study was to investigate the clinical outcome of patients with obstructive sleep apnea (OSA) without admission to the intensive care unit after laparoscopic bariatric surgery. MethodsFor the first 24 hours after surgery, all patients were admitted to a level 2 (high-dependency) area on a general surgical ward with experience of bariatric surgery. They received supplemental oxygen, continuous pulse oximetry, and judicious analgesic administration using a combination of small boluses of IV morphine together with IV paracetamol. Perioperative continuous positive airway pressure support was not routinely given, unless patients with OSA had oxygen saturation below their recorded preoperative level on 2 consecutive readings. ResultsA total of 1623 patients underwent laparoscopic bariatric surgery over a 12-year period. Of those, 192 had OSA with a median operative body mass index of 52 kg/m2 (range 34–78 kg/m2). The incidence of respiratory complications and the median length of stay (3 nights) were identical in patients with OSA and those without OSA. Four patients self-administered perioperative continuous positive airway pressure, but none required transfer to intensive care or mechanical ventilation. There were no in-hospital deaths. ConclusionLaparoscopic bariatric surgery in patients with OSA is well tolerated and does not require the routine use of level 3 critical care facilities.

The non-intubated, spontaneously breathing, continuous positive airway pressure (CPAP) ventilated pre-term lamb: A unique animal model

Neonatologists prefer non-invasive ventilation methods for pre-term neonates, who often require surfactant treatment. Therefore, a technology for non-invasive surfactant administration would be highly appreciated. We have developed a Continuous Powder Aerosolization (CPA) system for the generation of a humidified recombinant surfactant protein-C (rSP-C) surfactant aerosol for non-invasive administration to pre-term neonates via bi-nasal prongs. Before conducting clinical trials, safety testing in an adequate pre-clinical animal model is necessary. In contrast to existing pre-term lamb models, this model should use non-intubated animals to include upper airways for safety testing. Pre-term animals should have already a sufficient respiratory drive to breathe spontaneously on non-invasive continuous positive airway pressure (CPAP) support, but their lungs should still be pre-mature to be comparable with the clinical situation for the treatment of pre-term infants. The aim of this feasibility study was therefore to establish a CPAP-stable, non-intubated pre-term lamb model for the investigation of safety, efficacy, and pulmonary deposition of a humidified rSP-C surfactant aerosol. For this purpose, 19 pre-term lambs with a gestational age of 135–137 days (term: about 144 days) were delivered via Caesarean section. Four animals died before start of treatment, while the remaining animals were treated via customized bi-nasal prongs with rSP-C surfactant aerosol or humidified air as vehicle control. To determine pulmonary deposition, selected animals received rSP-C surfactant labelled with samarium oxide as non-radioactive tracer. Treatment was started at 30min of age and was continued for 1 or 2.5h. Investigations during the in-life phase included observation of clinical signs, haematology, blood gas analysis, and determination of minute volume. At 3h of age, animals were euthanized and organs removed for histopathology investigation or for determination of pulmonary deposition. Administration of humidified, aerosolized rSP-C surfactant was well tolerated, and histopathology investigation of upper airways and lungs revealed no aerosol-related changes. Mean body weight-corrected pulmonary deposition of rSP-C surfactant ranged from 1.7 to 7.7mg/kg depending on the duration of treatment and aerosolization parameters used. A trend towards reduced spontaneous minute volumes indicating reduced breathing efforts and towards reduced lung weights indicating less fluid in the lungs of surfactant-treated animals compared to animals of the vehicle control group could be seen. Taken together, a CPAP-stable, non-intubated pre-term lamb model was successfully established and the parameters for the investigation of safety, efficacy, and pulmonary deposition of aerosolized rSP-C surfactant for the subsequent main study were identified.

A Rational Approach to the Management of Obstructive Sleep Apnea Syndrome

Snoring & obstructive sleep apnea syndrome (OSAS) is a globally prevalent problem which is on the rise in recent times. The treatment modalities include medical appliances and surgery. It is mandatory to have a rational approach in the management of OSAS, by meticulously analyzing both anatomical and physiological parameters causing the disorder. To define a rational approach for the management of OSAS, by devising a comprehensive protocol with assessment of anatomical level of obstruction by dynamic MRI and physiological factors by Epworth sleepiness scale (ESS) and Polysomnography. A prospective study in 110 patients was conducted over a period of 2years, at our institute. All patients in the study group were evaluated with dynamic MRI and ESS and Polysomnography. As per the management protocols defined in the study, surgery was advocated in 46 patients (Group 1) with severe compromise in airway, while another group of 64 patients (Group 2) were provided continuous positive airway pressure support (CPAP). Successful outcomes among these 110 patients were analyzed at the end of the study period. A few patients required multimodal therapy which included surgery and CPAP support. Among 46 patients, surgical treatment proved successful in 41 patients in whom AHI reduced from 46.96 to 12.88 (improved by 62%) and ESS improved by almost ten points. Among 64 patients in CPAP group, AHI reduced from 54.2 to 11.3 (improved by 79%) and ESS improved by 11 points in all the patients, but six of them had poor compliance. Five patients among the surgical group had persistence of symptoms. Inferences derived from the above results proved the success of formulating a rational approach in the management of OSAS. Critical analysis of the anatomical and physiological factors inducing obstructive episodes and an appropriate treatment plan is vital, to produce successful outcomes in patients with OSAS. Failure of surgical procedures, are often due to improper case selection. A small group of patients may require multimodal therapy with surgery and CPAP.

First intention high-frequency oscillatory and conventional mechanical ventilation in premature infants without antenatal glucocorticoid prophylaxis*

Data comparing the effectiveness of high-frequency oscillatory ventilation and of conventional mechanical ventilation in the treatment of respiratory distress syndrome of very low birth weight infants are, to date, still matter of debate. We investigated the effects of first intention high-frequency oscillatory ventilation or conventional mechanical ventilation support on selected primary and secondary outcomes in very low birth weight infants complicated by respiratory distress syndrome in which antenatal glucocorticoid prophylaxis was not performed. Multicenter randomized control trial. Three tertiary centers of neonatal intensive care units from December 2004 to December 2007. Eighty-eight very low birth weight infants complicated by respiratory distress syndrome, without antenatal glucocorticoids, supported by first intention high-frequency oscillatory ventilation (n = 44) or conventional mechanical ventilation (n = 44). All newborns were monitored by standard monitoring procedure, including routine laboratory variables, neurologic patterns, and ultrasound imaging. Primary outcomes were: the length of ventilatory support, the need of reintubation, and the length of nasal continuous positive airway pressure support in the postextubation period. Secondary outcomes were: the length of stay in neonatal intensive care unit and in hospital, death before discharge, adverse short- and long-term pulmonary and neonatal outcomes, and the need for a second dose of surfactant and of postnatal glucocorticoid treatment. High-frequency oscillatory ventilation infants showed a significant lower duration (p < .001 for all) of ventilator dependency, lower need of reintubation and of duration of nasal continuous positive airway pressure support in the postextubation period. Among secondary outcomes in the high-frequency oscillatory ventilation infants, the need of a second dose of surfactant administration, and the length of stay in the neonatal intensive care unit and in hospital were significantly lower (p < .05 for all). We found that high-frequency oscillatory ventilation in very low birth weight infants without antenatal glucocorticoid prophylaxis reduced the need of ventilatory support, surfactant therapy, and reintubation, and shortened neonatal intensive care unit and hospital stay, thus reducing unit and hospital costs. These data would support the usefulness of first intention high-frequency oscillatory ventilation strategy in managing in a selected population, such as very low birth weight newborns complicated by severe respiratory distress syndrome not antenatally treated with glucocorticoids.

The Respiratory Morbidities in Late-preterm Infants Compared with the Early-preterm and Term Infants throughout the First Year of Life

Purpose: We examined the respiratory morbidities in late-preterm infants compared to those of the early-preterm infants and term infants throughout the first year of life. Methods: Data were retrospectively collected for 87 late-preterm, 72 early-preterm, and 608 term infants who were admitted to NICU and the nursery of Busan St. Mary's Medical Center from Jan 2007 to Oct 2009. Results: There were significant differences in the proportions of the out-born infants, twin pregnancy, small for gestational age, and Caesarean section in the three groups (P<0.05). Late-preterm and early-preterm infants had longer duration of hospitalization, larger proportions of respiratory distress syndrome, mechanical ventilation at birth, oxygen therapy after 48 hours of birth, oxygen dependency at 28 days, and continuous positive airway pressure support at 28 days compared to term infants during the neonatal period (P=0.000). Late-preterm infants and early-preterm infants were re-admitted more often than term infants during the first year of life (P=0.000). Also Late-preterm and early-preterm infants had increased chance of respiratory tract illness than term infants (P=0.001). Conclusion: In this study, we demonstrated that there are higher chances of respiratory morbidities in the late-preterm infants than the term infants either during the neonatal period or throughout the first year of life, although early-preterm infants showed greatest respiratory morbidities.

Influence of gender on continuous positive airway pressure requirements in patients with obstructive sleep apnea syndrome

Gender differences have been noted in key aspects of upper airway physiology and pathophysiology of obstructive sleep apnea (OSA). We postulate that these will lead to disparities in pharyngeal collapsibility and, consequently, positive airway pressure requirements of patients with OSA. A retrospective review of 95 adult patients (56 women, 39 men) with OSA was done. Patients who underwent continuous positive airway pressure (CPAP) titration were included in the study. The study groups were similar with regard to the severity of OSA (median apnea-hypopnea index of 34 in men and 24 in women, p = 0.13). The men were older and less obese than the women (mean age of 46 and 41 years, p = 0.03, BMI of 42 and 49 kg/m(2), p < 0.001, in men and women, respectively); Epworth score was similar in the two groups (12 vs.11, p = 0.91). CPAP requirement was higher in men than in women (12.7 vs. 10.2, p < 0.0001). The effect of gender on CPAP requirement was found to be significant even when confounding variables were accounted for using linear regression. Men with OSA are more likely to require higher levels of CPAP support than women. The effect of gender on CPAP requirement persisted even after correcting for the severity of OSA.

Unilateral Re-Expansion Pulmonary Edema following Treatment of Pneumothorax with Exceptionally Massive Sputum Production, followed by Circulatory Collapse

A case of a 61-year-old man who developed ipsilateral re-expansion pulmonary edema after pleural drainage for a right pneumothorax is described. The patient's chest x-ray revealed a totally collapsed right lung. After insertion of a chest drainage tube, he began to produce a moderate amount of serous, yellowish sputum. Despite continuous positive airway pressure support, his dyspnea gradually worsened and his oxygenation could not be maintained; therefore, to improve his hypoxemic state, intubation was necessary. His chest x-ray following chest tube insertion showed ipsilateral diffuse infiltrates. These radiographic and physical findings were consistent with re-expansion pulmonary edema. The present case was complicated by extreme hypotension and tachycardia due to massive fluid loss. His condition gradually improved with invasive mechanical ventilation. Re-expansion pulmonary edema is an uncommon complication of pleural drainage for pneumothorax, and therapy is supportive. In the present case, the exceptional severity of the pulmonary edema, as well as its general concept, is reviewed in accordance with other relevant literature.

Continuous Positive Airway Pressure vs. Pressure Support Ventilation in Acute Cardiogenic Pulmonary Edema: A Randomized Trial

Both non-invasive continuous positive airway pressure (nCPAP) and non-invasive pressure support ventilation (nPSV) have been shown to be effective treatment for acute cardiogenic pulmonary edema (ACPE). In patients with severe ACPE who are treated with standard medical treatment, the baseline intubation rate is approximately 24%. This study was conducted to compare the endotracheal intubation (ETI) rate using two techniques, nCPAP vs. nPSV. In addition, mortality rate, improvement in gas exchange, duration of ventilation, and hospital length of stay were also assessed. This prospective, multi-center, randomized study enrolled 80 patients with ACPE who were randomized to receive nCPAP or nPSV (40 patients in each group) via an oronasal mask. Inclusion criteria were severe dyspnea, respiratory rate > 30 breaths/min, use of respiratory accessory muscles, or PaO(2)/FiO(2) < 200. ETI was required in 0 (0%) and in 3 (7.5%) patients in the nCPAP group and in the nPSV group, respectively (p = 0.241). No significant difference was observed in in-hospital mortality: 2 (5%) vs. 7 (17.5%) in nCPAP and nPSV groups, respectively (p = 0.154). No difference in hospital length of stay was observed between the two groups, nor was there a difference observed in duration of ventilation, despite a trend for reduced time with nPSV vs. nCPAP (5.91 ± 4.01 vs. 8.46 ± 7.14 h, respectively, p = 0.052). Both nCPAP and nPSV were effective in improving gas exchange, including in the subgroup of hypercapnic patients. Both methods are effective treatment for patients with ACPE. Non-invasive CPAP should be considered as the first line of treatment because it is easier to use and less expensive than non-invasive PSV.

Letters to the Editor

11 December 2008 Dear Editor, UNILATERAL LUNG AGENESIS: COINCIDENCE OR ASSOCIATION WITH MATERNAL VALPROATE THERAPY? Management of epilepsy in pregnant women is a complex issue as use of antiepileptic medications increase the risk of congenital malformation in the foetus.1 The antiepileptic drug, sodium valproate, is a known teratogen with a constellation of recognised facial features and congenital malformations described in foetal valproate syndrome.2 Infants of mothers receiving valproate more than 1000 mg are at increased risk of congenital malformation, particularly neural tube defects.1 Exposure of foetus to valproate uncommonly results in pulmonary anomalies. Bilateral pulmonary hypoplasia with immature histology was reported in a series of three cases as a possible teratogenic effect of valproate.3 Other reported but rare pulmonary malformations in foetal valproate syndrome include tracheomalacia, abnormal lobulation of right lung, severe laryngeal hypoplasia and oligaemic right lung.4 Association of unilateral lung hypoplasia with maternal exposure to a combination of phenytoin and carbamazepine has been reported.1 A male infant was born at 38 weeks gestation with a birth weight of 2915 grams. The mother was a 32-year-old multiparous lady. During pregnancy, she continued to take sodium valproate, 1000 mg/day, to control grand mal epilepsy. This pregnancy was complicated by the detection of a possible left congenital diaphragmatic hernia on antenatal ultrasound at 18 weeks gestation. An amniocentesis performed at 19 weeks gestation demonstrated a normal male karyotpye. A foetal magnetic resonance imaging scan performed at 21 weeks gestation suggested hypoplasia of the left lung with a normal diaphragm. The infant delivered normally with Apgar scores of 6 and 6 at 1 and 5 min, respectively. There were no dysmorphic features of foetal valproate syndrome. He was managed in a neonatal intensive care unit with continuous positive airway pressure (CPAP) and received a single dose of surfactant. He was treated with phenobarbitone to manage symptoms of valproate withdrawal at approximately 24 h of age. Chest X-rays demonstrated dense opacification with loss of lung volume in the left hemithorax. The computed tomography scan showed absence of lung, bronchial tree, pulmonary artery and veins on the left side (Fig. 1). Echocardiogram showed a structurally normal heart with absence of the left pulmonary artery and left pulmonary veins. He was treated with nasal mask CPAP support for 7 weeks and was weaned successfully to room air at the age of 8 weeks. A polysomnography study showed no oxygen desaturation or hypercapnia while ventilating in room air. He was discharged home with paediatric respiratory follow-up. Computed tomography scan of chest showing absence of carina and left lung. Pulmonary agenesis is complete absence of carina, bronchial tree and lung tissue, and the trachea continues as main bronchus. In pulmonary aplasia, carina and rudimentary main bronchus are present, but lung tissue is absent.5 Pulmonary agenesis is a rare malformation. The prevalence of agenesis of lung was reported to be 0.0034% among hospital admissions.6 The aetiology of lung agenesis is not certain, but possible genetic predisposition has been described.6 Our literature review did not find any other case of unilateral lung agenesis in association with maternal valproate intake. Given the rarity of pulmonary agenesis, it is possible that the foetal exposure to valproate in this report is a chance association. However, this observation will add to previously known pulmonary pathologies seen in association with maternal valproate use and could be relevant from a prenatal counselling point of view.

Low socioeconomic status is a risk factor for CPAP acceptance among adult OSAS patients requiring treatment.

To evaluate whether socioeconomic status (SES) has a role in obstructive sleep apnea syndrome (OSAS) patients' decision to accept continuous positive airway pressure (CPAP) treatment. Cross-sectional study; patients were recruited between March 2007 and December 2007. University-affiliated sleep laboratory. 162 consecutive newly diagnosed (polysomnographically) adult OSAS patients who required CPAP underwent attendant titration and a 2-week adaptation period. 40% (n = 65) of patients who required CPAP therapy accepted this treatment. Patients accepting CPAP were older, had higher apnea-hypopnea index (AHI) and higher income level, and were more likely to sleep in a separate room than patients declining CPAP treatment. More patients who accepted treatment also reported receiving positive information about CPAP treatment from family or friends. Multiple logistic regression (after adjusting for age, body mass index, Epworth Sleepiness Scale, and AHI) revealed that CPAP purchase is determined by: each increased income level category (OR, 95% CI) (2.4; 1.2-4.6), age + 1 year (1.07; 1.01-1.1), AHI ( > or = 35 vs. < 35 events/hr) (4.2, 1.4-12.0), family and/or friends with positive experience of CPAP (2.9, 1.1-7.5), and partner sleeps separately (4.3, 1.4-13.3). In addition to the already known determinants of CPAP acceptance, patients with low SES are less receptive to CPAP treatment than groups with higher SES. CPAP support and patient education programs should be better tailored for low SES people in order to increase patient treatment initiation and adherence.

A Randomized Controlled Trial of Post-extubation Bubble Continuous Positive Airway Pressure Versus Infant Flow Driver Continuous Positive Airway Pressure in Preterm Infants with Respiratory Distress Syndrome

To compare the efficacy and safety of bubble continuous positive airway pressure (CPAP) and Infant Flow Driver (IFD) CPAP for the post-extubation management of preterm infants with respiratory distress syndrome (RDS). A total of 140 preterm infants at 24 to 29 weeks' gestation or with a birth weight of 600 to 1500 g who were ventilated at birth for RDS were randomized to receive either IFD CPAP (a variable-flow device) or bubble CPAP (a continuous-flow device). A standardized protocol was used for extubation and CPAP. No crossover was allowed. The primary outcome was successful extubation maintained for at least 72 hours. Secondary outcomes included successful extubation maintained for 7 days, total duration of CPAP support, chronic lung disease, and complications of prematurity. Seventy-one infants were randomized to bubble CPAP, and 69 were randomized to IFD CPAP. Mean gestational age and birth weight were similar in the 2 groups, as were the proportions of infants who achieved successful extubation for 72 hours and for 7 days. However, the median duration of CPAP support was 50% shorter in the infants on bubble CPAP. Moreover, in the subset of infants who were ventilated for less than 14 days, the infants on bubble CPAP had a significantly lower extubation failure rate. There was no difference in the incidence of chronic lung disease or other complications between the 2 study groups. Bubble CPAP is as effective as IFD CPAP in the post-extubation management of infants with RDS; however, in infants ventilated for < or = 14 days, bubble CPAP is associated with a significantly higher rate of successful extubation. Bubble CPAP also is associated with a significantly reduced duration of CPAP support.

The Mapleson D continuous positive airway pressure system: a novel indication for the Mapleson circuit?

The Mapleson D continuous positive airway pressure system: a novel indication for the Mapleson circuit?