Transcutaneous PCO2 Research Articles

A Moving Target: Studying the Effect of Continuous Transcutaneous CO2 Monitoring in ELBW Infants During an Equipoise Shift.

Objectives: To assess whether continuous non-invasive pCO2 monitoring by transcutaneous pCO2 monitor (TCpCO2) among extremely low birth weight (ELBW) premature infants, during the first week of life, will decrease the rate of high-grade intraventricular hemorrhage (IVH) or periventricular leukomalacia (PVL) or the combined outcome of IVH/PVL and death. Methods: This was a prospective, observational, multicenter study. Due to ethical constraints, allocation was based on TCpCO2 monitor availability. ELBW infants were either monitored by TCpCO2 monitor (Sentec, Therwil, Switzerland) (study group), or recruited to the control group if a TCpCO2 monitor was not available. Results: A total of 132 ELBW infants participated in the study. The size of the study group (106 infants) and the control group (26 infants) differed because monitor availability increased during the study period reflecting change in standard of care. The groups had comparable gestational age and baseline characteristics. No difference was found in the rate of IVH/PVL in the study vs. control groups (10% vs. 4%; p = 0.7, respectively), or in the combined outcome of PVL/IVH and death (16% vs. 15%; p = 1.0, respectively). Conclusions: This study demonstrates the challenges in conducting a prospective controlled trial in a rapidly evolving medical field. While the study began with a clear equipoise, this balance shifted as the care team gained more experience with TCpCO2 monitoring among the study population, despite the absence of new clinical evidence to justify such a shift. Consequently, the small control group limited our ability to draw definitive conclusions regarding the study's objective. However, our findings may increase awareness of continuous non-invasive pCO2 monitoring in extremely premature infants.

Pycnogenol® + Centellicum® supplementation improves skin elasticity and microperfusion. Implication for surgical patients: a conceptual registry study.

The aim of this registry study was to evaluate the effects of Pycnogenol® and Centellicum® (PYCE) on skin perfusion and skin elasticity in healthy women over a period of 4 weeks. The supplemented women used 150 mg of Pycnogenol® and 450 mg of Centellicum® daily. The supplemented group used the combination PYCE daily for 4 weeks and followed the standard management (SM) in addition. A control group used only the SM. SM for all subjects included a healthy diet (low levels of NaCl, low sugar, low calories), vitamin supplementation (C, E, B), daily mild outdoors exercise, regular washing with neutral soap; the same non-clinical, non-specific hydrating cream (Nivea) was used once daily. Sixty-three women completed the registry study. Thirty women using the PYCE combination and 33 women in the control group. The groups were comparable at baseline. No clinical condition was observed during the registry; no drug was used. There were no side effects or tolerability problems with the supplements. After 4 weeks, ultrasound elastosonography showed that skin elasticity significantly improved with the PYCE combination (P<0.05) without significant changes in the control group. In parallel, transcutaneous skin PO<inf>2</inf> increased significantly with PYCE compared to controls and transcutaneous skin PCO<inf>2</inf> decreased significantly compared to controls (P<0.05). This showed that skin oxygenation and nutrition improved with PYCE. Skin hydration also significantly improved with PYCE (P<0.05) in comparison with controls. Skin flow, indicating skin blood perfusion (thermoregulatory flow), assessed by laser Doppler flowmetry significantly improved over 4 weeks compared to controls (P<0.05). More specifically, the most superficial part of the flow, in the most superficial layer of the skin, corresponding to the nutritional blood flow, significantly improved with the combination PYCE compared to controls (P<0.05). Skin and tissue elasticity are crucial in surgery for healing, scarring, and wound closure. Reduced elasticity can lead to irregular or delayed healing. This preliminary concept study suggests that PYCE supplementation enhances skin elasticity, perfusion, and nutrition, with visible effects seen in just 4 weeks. This preliminary, concept study indicates that skin elasticity, skin perfusion, and skin nutrition improved with the supplementation of PYCE and the effects of PYCE were visible after only 4 weeks. A longer observation period should be considered in future studies. In conclusion, this pilot concept study shows a significant activity of the combination Pycnogenol® and Centellicum® on skin elasticity over a short period of supplementation.

Contribution of Transcutaneous PCO2 in Obesity Hypoventilation Syndrome.

More and more patients have obesity-hypoventilation syndrome (OHS) because of the increasing prevalence of obesity. The accuracy of transcutaneous PCO2 (PtcCO2 ) has recently been validated. However, no study evaluated the interest of measuring systematically nocturnal PtcCO2 in the follow-up of patients with OHS and home mechanical ventilation to detect residual nocturnal hypoventilation. We aimed to evaluate the contribution of nocturnal PtcCO2 to assess nocturnal hypoventilation compared with current routine examinations, that is, daytime arterial blood gases and nocturnal pulse oximetry. A prospective monocentric pilot study was conducted from August 2018 to November 2019. Patients with stable OHS and who were treated with home noninvasive ventilation for at least 6 months were eligible to participate. After oral consent, we performed both diurnal arterial blood gases and combined home oximetry and capnography. The primary end point was the presence of residual nocturnal hypoventilation, defined as PaCO2 > 45 mm Hg or bicarbonate ≥ 27 mmol/L, SpO2 < 90% for ≥ 10% of the night, or PtcCO2 > 49 mm Hg for ≥ 10% of the night. A total of 32 subjects were included. Twenty-nine subjects with nocturnal PtcCO2 were analyzed. Eighteen of the 29 subjects showed residual nocturnal hypoventilation. The association of diurnal arterial blood gases and nocturnal pulse oximetry revealed nocturnal hypoventilation in only 9 subjects. Among the 19 subjects with both normal blood gases and normal nocturnal pulse oximetry, 11 had nocturnal hypoventilation with transcutaneous capnography. Only one subject presented with hypoventilation symptoms (asthenia). The assessment of PtcCO2 in comparison with nocturnal pulse oximetry and arterial blood gases provides important information for the diagnosis of residual nocturnal hypoventilation in the subjects with OHS who were ventilated at home.

A decrease in plant gain, namely CO2 stores, characterizes dysfunctional breathing whatever its subtype in children.

Background: Whether dysfunctional breathing (DB) subtype classification is useful remains undetermined. The hyperventilation provocation test (HVPT) is used to diagnose DB. This test begins with a 3-min phase of hyperventilation during which fractional end-tidal CO2 (FETCO2) decreases that could be an assessment of plant gain, which relies on CO2 stores. Our aim was to assess 1) whether the children suffering from different subtypes of DB exhibit decreased plant gain and 2) the relationships between HVPT characteristics and plant gain. Methods: We retrospectively selected 48 children (median age 13.5years, 36 females, 12 males) who exhibited during a cardiopulmonary exercise test either alveolar hyperventilation (transcutaneous PCO2 < 30mmHg, n = 6) or inappropriate hyperventilation (increased VE'/V'CO2 slope) without hypocapnia (n = 18) or dyspnea without hyperventilation (n = 18) compared to children exhibiting physiological breathlessness (dyspnea for sports only, n = 6). These children underwent tidal-breathing recording (ventilation and FETCO2 allowing the calculation of plant gain) and a HVPT. Results: The plant gain was significantly higher in the physiological group as compared to the dyspnea without hyperventilation group, p = 0.024 and hyperventilation without hypocapnia group, p = 0.008 (trend for the hyperventilation with hypocapnia group, p = 0.078). The slope of linear decrease in FETCO2 during hyperventilation was significantly more negative in physiological breathlessness group as compared to hyperventilation without hypocapnia group (p = 0.005) and dyspnea without hyperventilation group (p = 0.049). Conclusion: The children with DB, regardless of their subtype, deplete their CO2 stores (decreased plant gain), which may be due to intermittent alveolar hyperventilation, suggesting the futility of our subtype classification.

Fluctuations in Oxygen Saturation during Synchronized Nasal Intermittent Positive Pressure Ventilation and Nasal High-Frequency Oscillatory Ventilation in Very Low Birth Weight Infants: A Randomized Crossover Trial

Background: Very low birth weight (VLBW) infants on noninvasive ventilation (NIV) experience frequent fluctuations in oxygen saturation (SpO₂) that are associated with an increased risk for mortality and severe morbidities. Methods: In this randomized crossover trial, VLBW infants (n = 22) born 22+3 to 28+0 weeks on NIV with supplemental oxygen were allocated on two consecutive days in random order to synchronized nasal intermittent positive pressure ventilation (sNIPPV) and nasal high-frequency oscillatory ventilation (nHFOV) for 8 h. nHFOV and sNIPPV were set to equivalent mean airway pressure and transcutaneous pCO₂. Primary outcome was the time spent within the SpO₂ target (88–95%). Results: During sNIPPV, VLBW infants spent significantly more time within the SpO₂ target (59.9%) than during nHFOV (54.6%). The proportion of time spent in hypoxemia (22.3% vs. 27.1%) and the mean fraction of supplemental oxygen (FiO₂) (29.4% vs. 32.8%) were significantly reduced during sNIPPV, while the respiratory rate (50.1 vs. 42.6) was significantly higher. Mean SpO₂, SpO₂ above the target, number of prolonged (>1 min) and severe (SpO₂ <80%) hypoxemic episodes, parameters of cerebral tissue oxygenation using NIRS, number of FiO₂ adjustments, heart rate, number of bradycardias, abdominal distension and transcutaneous pCO₂ did not differ between both interventions. Conclusions: In VLBW infants with frequent fluctuations in SpO₂, sNIPPV is more efficient than nHFOV to retain the SpO₂ target and to reduce FiO₂ exposure. These results demand more detailed investigations into cumulative oxygen toxicities during different modes of NIV over the weaning period, particularly with regard to consequences for long-term outcomes.

The effect of hyperoxia on ventilation during recovery from general anesthesia: A randomized pilot study for a parallel randomized controlled trial

Study objectiveWhile supplemental O2 inhalation corrects hypoxemia, its effect on post-anesthesia ventilation remains unknown. This pilot trial tested the hypothesis that hyperoxia increases the time spent with a transcutaneous PCO2 (TcPCO2) > 45 mmHg, compared with standard O2 supplementation. DesignSingle-blinded, parallel two-arm randomized pilot trial. SettingUniversity hospital. Patients20 patients undergoing robotic-assisted laparoscopic nephrectomy. MeasurementsAfter institutional approval and informed consent, patients were randomized to receive O2 titrated to arterial saturation (SpO2): 90–94% (Conservative O2, N =10), or to SpO2 > 96% (Liberal O2, N = 10) for up to 90 min after anesthesia. Continuous TcPCO2, respiratory inductance plethysmography (RIP), and SpO2, were recorded. We calculated the percentage of time at TcPCO2 > 45 mmHg for each patient and compared the two groups using analysis of covariance, adjusting for sex, age, and body mass index. We also estimated the sample size required to detect the between-group difference observed in this pilot trial. RIP signals were used to calculate apnea/hypopnea index (AHI), which was then compared between two groups. Main resultsThe mean percentage of time with a TcPCO2 > 45 mmHg was 80.6% for the Conservative O2 (N=9) and 61.2% for the Liberal O2 (N=10) group [between-group difference of 19.4% (95% CI: −18.7% to 57.6%), P = 0.140]. With an observed effect size of 0.73, we estimated that 30 participants per group are required, to demonstrate this difference with a power of 80% at a two-sided alpha of 5%. Means SpO2 were 94.5% and 99.9% for the Conservative O2 and the Liberal O2 groups, respectively. AHI was significantly higher in the Conservative O2, compared with the Liberal O2 group (median AHI: 16 vs. 3; P = 0.0014). ConclusionsHyperoxia in the post-anesthesia period reduced the time spent at TcPCO2 > 45 mmHg and significantly decreased AHI, while mean SpO2 ranged inside the a priori defined limits. Trial registrationClinicalTrials.gov identifier: NCT04723433

IMPLEMENTING BREATH-BY-BREATH VOLUMETRIC CAPNOGRAPHY DEAD-SPACE COMPONENT CALCULATION DURING INCREMENTAL CYCLE EXERCISE

IMPLEMENTING BREATH-BY-BREATH VOLUMETRIC CAPNOGRAPHY DEAD-SPACE COMPONENT CALCULATION DURING INCREMENTAL CYCLE EXERCISE

The Impact of Non-Invasive Ventilation on Sleep Quality in COPD Patients.

Background: Non-invasive ventilation (NIV) has been shown to be the most appropriate therapy for COPD patients with chronic respiratory failure. While physiological parameters and long-term outcome frequently serve as primary outcomes, very few studies have primarily addressed the impact of NIV initiation on sleep quality in COPD. Methods: This single-center prospective cohort study comprised NIV-naïve patients with COPD. All patients underwent polysomnographic evaluation both at baseline and at 3 months follow-up, accompanied by the assessment of health-related quality of life (HRQL) using the Severe Respiratory Insufficiency Questionnaire (SRI) and the Epworth Sleepiness Scale (ESS). A subgroup evaluation was performed to address the impact of comorbid obstructive sleep apnea syndrome (OSAS). Results: Forty-six patients were enrolled and twenty-five patients completed the follow-up period (66.7 ± 7.4 years). NIV resulted in an increase in slow-wave sleep (+2% (−3.5/7.5), p = 0.465) and rapid eye movement sleep (+2.2% (−1.0/5.4), p = 0.174), although no statistical significance could be detected. ESS (−1.7(−3.6/0.1), p = 0.066) also showed a positive trend. Significant improvements in the Respiratory Disturbance Index (RDI) (−12.6(−23.7/−1.5), p = 0.027), lung function parameters, transcutaneous PCO2 and the SRI summary scale (4.5(0.9/8), p = 0.016) were observed. Conclusion: NIV therapy does not decrease sleep quality and is even capable of improving HRQL, transcutaneous PaCO2, daytime sleepiness and RDI, and the latter especially holds true for patients with comorbid OSAS.

Simultaneous measurement of DC-EEG and transcutaneous pCO2

Abstract DC potential shifts are the shifts observed in the EEG baseline which can last from seconds to minutes. The significance of these low-frequency components in healthy as well as pathological states of human physiology is getting more and more attention not only in scientific research but also in clinical applications. In this paper, we present our novel multimodal measurement setup for simultaneously investigating DC potential shifts in EEG (DC-EEG) and the changes in noninvasive transcutaneous pCO2 measurements. We present preliminary results of our measurements during hyperventilation and apnea, which are two commonly used activation methods for changes in pCO2.

Dexmedetomidine versus propofol sedation in flexible bronchoscopy: a randomized controlled trial

BackgroundDexmedetomidine (DEX), is a highly selective alpha2 adrenoceptor (α2-AR) agonist, successfully used in various procedures including flexible bronchoscopy. Randomized controlled trials (RCTs) evaluating DEX sedation during bronchoscopy report equivocal results regarding respiratory and hemodynamic outcomes.MethodsWe conducted an RCT to evaluate the efficacy and safety of dexmedetomidine compared to propofol for sedation during bronchoscopy. The primary outcome was the number of desaturation events, secondary outcomes were transcutaneous Pco2 level, hemodynamic adverse events and physician and patient satisfaction.ResultsOverall, 63 patients were included, 30 and 33 in the DEX and propofol groups, respectively. The number of desaturation events was similar between groups, median (IQR) 1 (0–1) and 1 (0–2) in the DEX and control groups, respectively (P = 0.29). Median desaturation time was 1 (0–2) and 1 (0–3) minutes in the DEX and control groups, respectively (P = 0.48). Adverse events included hypotension, 33% vs 21.1% in intervention and control groups, respectively (P = 0.04), bradycardia, cough, and delayed recovery from sedation. Total adverse events were 22 and 7 in DEX and propofol groups, respectively (P = 0.009).ConclusionDexmedetomidine sedation during bronchoscopy did not show differences in oxygen saturation and transcutaneous CO2 level in comparison to propofol. Moreover, DEX sedation required a significantly higher number of rescue boluses, due to inadequate sedation and was associated with a higher rate of adverse events.Trial registration NCT04211298, registration date: 26.12.2019.

Accuracy of a Novel Transcutaneous PCO2 and PO2 Sensor with Optical PO2 Measurement in Neonatal Intensive Care: A Single-Centre Prospective Clinical Trial

Background and Objectives: Transcutaneous PCO2 and PO2 measurement systems offer non-invasive blood gas trend monitoring. The aim of this prospective study was to assess bias and precision of a transcutaneous PCO2 and PO2 measurement system incorporating a novel pO2 sensor (Sentec OxiVenT™) in neonates ≥34 weeks of gestational age (GA) admitted to intensive care. Methods: Transcutaneous PCO2 and PO2 were compared to arterial and capillary blood gas measurements. Bias and precision were calculated by fitting linear mixed models to account for repeated measurements, and influence of clinical covariates on bias and precision was assessed. Results: We obtained 611 paired transcutaneous and blood gas measurements in 110 patients (median GA 38.3 [interquartile range 36.1–39.7] weeks; age 9 [4–15] days; weight 3,000 [2,500–3,500] g). Transcutaneous PCO2 showed significant bias to arterial PCO2 (+0.61; 95% confidence interval 0.46, 0.76 kPa), but not to capillary PCO2 (−0.23; −0.46, 0.002 kPa). Bias of transcutaneous PO2 was significant to arterial PO2 (−2.50; −2.94, −2.06 kPa), while no significant bias compared to capillary PO2 was observed (+0.17; −0.30, 0.64 kPa). Precision intervals were ±1.8/2.0 kPa for arterial versus capillary PCO2 and ±4.9/3.3 kPa for arterial versus capillary PO2 comparisons, respectively. Further, sensor operating temperature (43°C vs. 42°C), soft tissue oedema, vasoactive drugs, weight, and GA significantly altered bias (p < 0.05). Conclusions: The tested transcutaneous blood gas measurement system showed no significant bias compared to capillary PCO2 and PO2, acceptable bias to arterial PCO2, and limited agreement with arterial PO2. Precision intervals were wide for all comparisons.

Validation of a new combined transcutaneous tcPCO2 and tcPO2 sensor in children in the operating theater.

BackgroundArterial blood gas analysis is the gold standard for monitoring of PaCO2 and PaO2 during mechanical ventilation. However, continuous measurements would be preferred. Transcutaneous sensors continuously measure blood gases diffusing from the locally heated skin. These sensors have been validated in children mostly in intensive care settings. Accuracy in children during general anesthesia is largely unknown.AimsWe conducted a study in children undergoing general anesthesia to validate the use and to determine the accuracy of continuous transcutaneous measurements of the partial pressures of PCO2 (tcPCO2) and PO2 (tcPO2).MethodsA prospective observational study in a tertiary care pediatric hospital in The Netherlands, from April to October 2018, in children aged 0–18 years undergoing general anesthesia. Patients were included when endotracheally intubated and provided with an arterial catheter for regular blood sampling. Patients with a gestational age <31 weeks, burn victims, and patients with skin disease were excluded. TcPCO2 and tcPO2 measurements were performed with a SenTec OxiVenT™ sensor (SenTec AG). Accuracy was determined with an agreement analysis between arterial and transcutaneous PCO2 and PO2 values, and between arterial and endtidal PCO2 (etCO2) values, according to Bland and Altman, accounting for multiple measurements per subject.ResultsWe included 53 patients (median age 4.1 years, IQR 0.7–14.4 years) and retrieved 175 samples. TcPCO2‐PaCO2 agreement analysis provided a bias of 0.06 kPa (limits of agreement (LOA) −1.18 to 1.31), the etCO2‐PaCO2 agreement showed a bias of −0.31 kPa (LOA −1.38 to 0.76). Results of the tcPO2‐PaO2 agreement showed a bias of 3.40 to 0.86* (mean tension) kPa.ConclusionsThis study showed good agreement between PaCO2 and tcPCO2 in children of all ages during general anesthesia. Both transcutaneous and endtidal CO2 measurements showed good accuracy. TcPO2 is only accurate under 6 months of age.

Transcutaneous and End-Tidal CO₂ Measurements in Hypoxia and Hyperoxia.

BACKGROUND: Transcutaneous measurement of carbon dioxide (CO₂) has been proposed for physiological monitoring of tactical jet aircrew because in some clinical settings it mirrors arterial CO₂ partial pressure (Paco₂). End-tidal monitoring in laboratory settings is known to give high-fidelity estimates of Paco₂.METHODS: The correspondence between end-tidal (PETco₂) and transcutaneous Pco₂ (tcPco₂) was examined in healthy volunteers under laboratory conditions of hyperoxia and hypoxia. Rest and exercise, skin heating and cooling, hyperventilation, and induced CO₂ retention were employed.RESULTS: Neither measure followed all known changes in Paco₂ and tcPco₂ changed when the skin temperature near the probe changed. Bland-Altman analysis showed significant nonzero slopes under most conditions. Regression analysis indicated that oxygen partial pressure (Po₂) in tissue measured as transcutaneous Po₂ (tcPo₂) is an important explanatory variable for tcPco₂ in addition to PETco₂, and that local skin temperature also has an effect. Additionally, absorption atelectasis from breathing 100% O₂ may cause PETco₂ to deviate from Paco₂.DISCUSSION: Even as a trend indicator for Paco₂, tcPco₂ is not useful under conditions that resemble those in the highly dynamic tactical jet aircraft environment. PETco₂ is also not a good indicator of CO₂ status in pilots who breathe nearly 100% O₂.Shykoff BE, Lee LR, Gallo M, Griswold CA. Transcutaneous and end-tidal CO₂ measurements in hypoxia and hyperoxia. Aerosp Med Hum Perform. 2021; 92(11):864-872.

14 Diaphragmatic Electrical Activity in Preterm Infants on Non-Invasive High Frequency Oscillatory Ventilation (DEAP-NHFO Study)

Abstract Primary Subject area Neonatal-Perinatal Medicine Background Continuous Positive Airway Pressure (CPAP) is a common form of non-invasive respiratory support for preterm infants. Non-invasive high frequency ventilation (NHFOV) is a relatively new method of non-invasive respiratory support. NHFOV is being increasingly utilized in clinical practice in an attempt to prevent intubation and minimize ventilator-induced lung injury in preterm infants. Preliminary studies suggest superiority of NHFOV over CPAP, but little is known about its mechanism of action and its effect on respiratory control in the newborn. We hypothesize that NHFOV reduces respiratory drive and improves ventilation, resulting in decreased patient diaphragm energy expenditure, which can be assessed by measuring the electrical activity of the diaphragm (Edi). Objectives The objective of this study is to compare the effects of non-invasive respiratory support delivered by nasal CPAP versus NHFOV on respiratory pattern, as assessed by the Edi in very low birth weight (VLBW) preterm infants. Design/Methods In a prospective, randomized, crossover study, 20 preterm infants with birth weights ≤1500 g requiring CPAP were randomized to either NHFOV or CPAP for 105 min, followed by crossover to the other method for the same duration. Edi was continuously measured by a feeding catheter with miniaturized sensors embedded in its wall (Maquet, Solna). The general sequence was 15 minutes for acclimation to the mode, 75 minutes for a feed to be completed, followed by 15 minutes for breath-by-breath analyses of neural breathing pattern. Primary outcome was difference in the peak Edi between CPAP and NHFOV. Secondary outcomes included difference in other measures of respiratory drive: neural respiratory rate, neural inspiratory time, diaphragm energy expenditure, transcutaneous pCO2, number of apnea episodes on the Edi, and episodes of clinically significant apnea. Results No significant differences in Edi timing, Edi min, Edi peak, apnea, or CO2 were observed between the two modes of respiratory support. Conclusion In this cohort of VLBW preterm infants, neural respiratory pattern was not significantly different between NHFOV and CPAP. With this baseline information in stable preterm infants, it would now be important to assess whether these results hold true in infants with more severe lung disease, where NHFOV is often used as escalating support from CPAP.

Automatic oxygen titration versus constant oxygen flow rates during walking in COPD: a randomised controlled, double-blind, crossover trial

RationaleIn patients with COPD, oxygen (O2)-supplementation via a constant flow oxygen system (CFOS) can result in insufficient oxygen saturation (SpO2 <90%) during exercise. An automatically titrating O2-system (ATOS) has been...

Comparison between PtCO2 and PaCO2 and Derived Parameters in Heart Failure Patients during Exercise: A Preliminary Study.

Evaluation of arterial carbon dioxide pressure (PaCO2) and dead space to tidal volume ratio (VD/VT) during exercise is important for the identification of exercise limitation causes in heart failure (HF). However, repeated sampling of arterial or arterialized ear lobe capillary blood may be clumsy. The aim of our study was to estimate PaCO2 by means of a non-invasive technique, transcutaneous PCO2 (PtCO2), and to verify the correlation between PtCO2 and PaCO2 and between their derived parameters, such as VD/VT, during exercise in HF patients. 29 cardiopulmonary exercise tests (CPET) performed on a bike with a ramp protocol aimed at achieving maximal effort in ≈10 min were analyzed. PaCO2 and PtCO2 values were collected at rest and every 2 min during active pedaling. The uncertainty of PCO2 and VD/VT measurements were determined by analyzing the error between the two methods. The accuracy of PtCO2 measurements vs. PaCO2 decreases towards the end of exercise. Therefore, a correction to PtCO2 that keeps into account the time of the measurement was implemented with a multiple regression model. PtCO2 and VD/VT changes at 6, 8 and 10 min vs. 2 min data were evaluated before and after PtCO2 correction. PtCO2 overestimates PaCO2 for high timestamps (median error 2.45, IQR −0.635–5.405, at 10 min vs. 2 min, p-value = 0.011), while the error is negligible after correction (median error 0.50, IQR = −2.21–3.19, p-value > 0.05). The correction allows removing differences also in PCO2 and VD/VT changes. In HF patients PtCO2 is a reliable PaCO2 estimation at rest and at low exercise intensity. At high exercise intensity the overall response appears delayed but reproducible and the error can be overcome by mathematical modeling allowing an accurate estimation by PtCO2 of PaCO2 and VD/VT.

847 Rapid Improvement of Pulmonary Hypertension with Adequate Ventilatory Support in Patient with Prader-Willi Syndrome

Abstract Introduction Prader-Willi syndrome (PWS) is a genetic multi-system disorder characterized by developmental delay, hyperphagia, and often morbid obesity. Patients can have impairments in ventilatory control and are at risk for sleep disordered breathing due to craniofacial abnormalities, obesity, hypothalamic dysfunction, hypotonia and respiratory muscle weakness. This places them at higher risk for obstructive sleep apnea (OSA), hypoventilation and, if left untreated, may lead to cardiovascular complications. We present a patient with pulmonary hypertension (PH) in the setting of PWS and under supported OSA. Report of case(s) A 17-year-old female with PWS, obesity, type II diabetes mellitus, developmental delay and severe OSA, non-adherent to positive airway pressure (PAP) therapy, presented with 6 months of pedal edema, weight gain with acute shortness of breath, fatigue, and decreased appetite. Upon arrival she developed hypoxemic, hypercapnic respiratory failure requiring intubation. Echocardiogram two months prior to admission showed normal right ventricular size and function with normal septal configuration. Echocardiogram after intubation showed signs of PH with dilated and hypokinetic ventricles compared to prior exam, worsening tricuspid valve regurgitation, and septal bowing. Sleep history was notable for severe OSA in 2017 with obstructive apnea-hypopnea index (oAHI) of 22.6, oxygen nadir of 74%, peak transcutaneous pCO2 of 51 mmHg. Patient was lost to follow-up and as per our history, was non-adherent to PAP therapy. On admission she was started on aggressive diuresis and tadalafil. After successful extubation to BPAP and wean to room air while awake, a BPAP titration PSG was performed. It demonstrated low baseline oxygen saturations (93%), an oxygen nadir of 70%, transcutaneous CO2 peak of 57mmHg with obstructive events eliminated with BPAP of 24/14 cmH20 and hypoxemia treated with 4L supplemental oxygen. With adequate respiratory support with sleep combined with PH monotherapy, repeat echocardiogram prior to discharge showed improved systolic function and only mild septal flattening. Conclusion It is unclear the prevalence of PH in patients with PWS independent of OSA, however it is likely increased overall secondary to the increased prevalence of OSA. As a result, patients with PWS may benefit from routine interval echocardiogram to monitor for signs of PH. Support (if any):

Transcutaneous PCO2 -based dead space ventilation at submaximal exercise accurately discriminates healthy controls from patients with chronic obstructive pulmonary disease.

Increased physiological dead space ventilation (VD /VT ) at exercise reflects pulmonary gas exchange impairment and is a sensitive marker of cardio-respiratory disease. VD /VT is typically not measured during routine cardiopulmonary exercise testing (CPET) because its calculation requires arterial blood gas analysis for determination of PaCO2 . Instead, dead space ventilation is indirectly evaluated as a determinant of the ventilation (VE)/VCO2 relationship, which also depends on the PaCO2 set point. We hypothesized that VD /VT calculations based on non-invasive transcutaneous PCO2 (PtcCO2 ) measurement had better diagnostic characteristics than the VE/VCO2 slope for the discrimination of healthy subjects from patients with COPD, a common disease associated with impaired pulmonary gas exchange. Retrospective study of 19 healthy controls and 24 COPD patients who underwent CPET with continuous PtcCO2 monitoring. Areas under receiver operating characteristics curves (AUC) were calculated to assess diagnostic accuracy of CPET measurement for the discrimination of COPD and Controls. The AUC for PtcCO2 -based VD /VT at VT1 (0.977) was significantly higher than for the VE/VCO2 slope (0.660), SpO2 at peak exercise (0.913), decrease in inspiratory capacity (0.719), and ventilatory reserve (0.708). At a threshold of 0.24, the sensitivity and specificity of PtcCO2 -based VD /VT for the discrimination of COPD patients and healthy Controls were 100% and 84%, respectively. All Control subjects had PtcCO2 -based VD /VT ≤0.25. PtcCO2 -based VD /VT was the most accurate measurement to discriminate healthy controls from subjects with COPD, a chronic lung disease associated with altered pulmonary gas exchange. Non-invasive monitoring of PtcCO2 may be useful for routine CPET.

Oronasal versus Nasal Masks for Non-Invasive Ventilation in COPD: A Randomized Crossover Trial.

PurposeThe impact of oronasal and nasal masks on the quality of nocturnal non-invasive ventilation (NIV) needs to be clarified. This trial was designed to compare the impact of oronasal and nasal masks on the objective quality and subjective acceptance of nocturnal NIV in COPD-patients.Patients and MethodsIn a randomized crossover trial, 30 COPD-patients with well-established high-intensity NIV (mean inspiratory/expiratory positive airway pressure 26±3/5±1 cmH2O, mean respiratory back-up rate 17±1/min) were ventilated for two consecutive nights on oronasal and nasal masks, respectively.ResultsFull polysomnography, nocturnal blood gas measurements, and subjective assessments were performed. There was a tendency towards improved sleep efficiency (primary outcome) when an oronasal mask was worn (+9.9%; 95% CI:-0.2%-20.0%; P=0.054). Sleep stages 3/4 were favored by the oronasal mask (+12.7%; 95% CI: 6.0%-19.3%; P=<0.001). Subjective assessments were comparable with the exception of items related to leakage (P<0.05 in favor of nasal masks). The mean transcutaneous PCO2 value for oronasal masks (47.7±7.4 mmHg) was comparable to that of nasal masks (48.9±6.6 mmHg) (P=0.11). There was considerable diversity amongst individual patients in terms of sleep quality and gas exchange following mask exchange. Subjective mask preference was not associated with sleep quality, but with nocturnal dyspnea. Over 40% of patients subsequently switched to the mask that they were not previously accustomed to.ConclusionIn general, oronasal and nasal masks are each similarly capable of successfully delivering NIV in COPD-patients. However, the individual response to different interfaces is extremely heterogeneous, while subjective mask preference is independent from objective measures, but associated with dyspnea.Trial RegistrationGerman Clinical Trials Registry (DRKS00007741).

Nocturnal Transcutaneous Blood Gas Measurements in a Pediatric Neurologic Population: A Quality Assessment

ABSTRACT Objective: To assess the quality of SpO2 and PCO2 recordings via transcutaneous monitoring in children with neurological conditions. Methods: Overnight transcutaneous SpO2 and PCO2 were analyzed. The presence of drift and drift correction was noted, and the rate of disrupted recordings scored (0: absence, 1; presence). The quality of recordings was also scored (0, 1, 2 for poor, medium, and high). Results: A total of 228 recordings from 64 children aged 9.7 ± 6 years were analyzed of which 42 used positive pressure respiratory support. The mean quality of the recordings was scored as 1.27 (0–2). PCO2 drift, drift correction, and disrupted recordings were present in 25%, 58%, and 26% of recordings, respectively. Satisfactory clinical decisions were taken in 91% of cases. Conclusion: The quality of transcutaneous sensor recordings was acceptable and clinical findings were deemed as satisfactory in the large majority of cases. Correction of PCO2 drift was challenging.