The DELUX study: development of lung volumes during extubation of preterm infants

Objective To measure changes in end-expiratory lung impedance (EELI) as a marker of functional residual capacity (FRC) during the entire extubation procedure of very preterm infants. Methods Prospective observational study in preterm infants born at 26–32 weeks gestation being extubated to non-invasive respiratory support. Changes in EELI and cardiorespiratory parameters (heart rate, oxygen saturation) were recorded at pre-specified events during the extubation procedure compared to baseline (before first handling of the infant). Results Overall, 2912 breaths were analysed in 12 infants. There was a global change in EELI during the extubation procedure (p = 0.029). EELI was lowest at the time of extubation [median (IQR) difference to baseline: −0.30 AU/kg (−0.46; −0.14), corresponding to an FRC loss of 10.2 ml/kg (4.8; 15.9), padj = 0.004]. The biggest EELI loss occurred during adhesive tape removal [median change (IQR): −0.18 AU/kg (−0.22; −0.07), padj = 0.004]. EELI changes were highly correlated with changes in the SpO2/FiO2 ratio (r = 0.48, p < 0.001). Forty per cent of FRC was re-recruited at the tenth breath after the initiation of non-invasive ventilation (p < 0.001). Conclusions The extubation procedure is associated with significant changes in FRC. This study provides novel information for determining the optimal way of extubating a preterm infant. Impact This study is the first to examine the development of lung volumes during the entire extubation procedure including the impact of associated events. The extubation procedure significantly affects functional residual capacity with a loss of approximately 10 ml/kg at the time of extubation. Removal of adhesive tape is the major contributing factor to FRC loss during the extubation procedure. Functional residual capacity is regained within the first breaths after initiation of non-invasive ventilation and is further increased after turning the infant into the prone position.

Correction of sensor crosstalk error in Exhalyzer D multiple-breath washout device significantly impacts outcomes in children with cystic fibrosis

Rationale: Nitrogen multiple-breath washout is an established technique to assess functional residual capacity and ventilation inhomogeneity in the lung. Accurate measurement of gas concentrations is essential for the appropriate calculation of clinical outcomes. Objectives: We investigated the accuracy of oxygen and carbon dioxide gas sensor measurements used for the indirect calculation of nitrogen concentration in a commercial multiple-breath washout device (Exhalyzer D, Eco Medics AG, Duernten, Switzerland) and its impact on functional residual capacity and lung clearance index. Methods: High precision calibration gas mixtures and mass spectrometry were used to evaluate sensor output. We assessed the impact of corrected signal processing on multiple-breath washout outcomes in a dataset of healthy children and children with cystic fibrosis using custom analysis software. Results: We found inadequate correction for the cross sensitivity of the oxygen and carbon dioxide sensors in the Exhalyzer D device. This results in an overestimation of expired nitrogen concentration, and consequently multiple-breath washout outcomes. Breath-by-breath correction of this error reduced the mean (SD) cumulative expired volume by 19.6 (5.0)%, functional residual capacity by 8.9 (2.2)%, and lung clearance index by 11.9 (4.0)%. It also substantially reduced the level of the tissue nitrogen signal at the end of measurements. Conclusions: Inadequate correction for cross sensitivity in the oxygen and carbon dioxide gas sensors of the Exhalyzer D device leads to an overestimation of functional residual capacity and lung clearance index. Correction of this error is possible and could be applied by re-analyzing the measurements in an updated software version.

Manajemen Pasien Dekstroskoliosis Berat dengan Kegagalan Napas yang disebabkan oleh Syok Septik dan Pneumonia

Latar belakang: Dekstroskoliosis adalah jenis skoliosis dengan deformitas kurva tulang belakang ke kanan. Dekstroskoliosis berat dengan Cobbs Angle > 70o mengakibatkan berkurangnya kapasitas paru, Functional Residual Capacity (FRC), volume tidal, dan mempunyai kondisi seperti penyakit paru restriktif. Pada kondisi berat dapat menyebabkan hipoksemia, hiperkapnia dan gagal napas. Penyebab tersering gagal napas pada pasien dekstroskoliosis berat ialah sepsis/syok septik yang disebabkan oleh pneumonia. Sampai saat ini belum ada tatalaksana khusus yang menjelaskan tentang manajemen pasien dekstroskoliosis berat dengan gagal napas yang disebabkan syok septik dan pneumonia. Kasus: Pria berusia 46 tahun dengan berat badan 40 kg dan tinggi badan 165 cm rujukan dari Rumah Sakit luar dengan riwayat sesak napas dan kehilangan kesadaran sejak satu minggu sebelumnya, masuk ke Instalasi Gawat Darurat dengan laju pernapasan 40 x/menit, dengan menggunakan Nonrebreathing Mask 15 lpm saturasi oksigen terukur hanya 90% dengan tekanan darah 60/40 mmHg dan laju nadi 120 x/menit. Pasien memiliki riwayat batuk dengan dahak kuning dan demam sekitar 1 bulan. Pasien dinilai sebagai gagal napas dengan dekstroskoliosis berat dan penyulit syok septik dan Community Acquired Pneumonia, kami lakukan tindakan intubasi dan resusitasi sesuai sepsis bundle terbaru, pasien kemudian kami rawat di Intensive Care Unit (ICU) selama 10 hari dengan bantuan ventilasi mekanik invasif dengan menggunakan prinsip Lung protective strategy dan Survival Sepsis Campaign Bundle terbaru, hari ke 11 pasien stabil bisa lepas dari ventilator dan dipindahkan ke bangsal. Kesimpulan: Lung protective strategy dan Survival Sepsis Campaign Bundle dapat digunakan untuk manajemen pasien dekstroskoliosis berat dengan gagal napas yang disebabkan syok septik dan pneumonia.

Accuracy of the end-expiratory lung volume measured by the modified nitrogen washout/washin technique: a bench study

Background The functional residual capacity (FRC) determines the oxygenating capacity of the lung and is heavily affected in the clinical context of the acute respiratory distress syndrome. Nitrogen-wash-in/wash-out methods have been used to measure FRC. These methods have rarely been validated against exactly known volumes. The aim of the study was to assess the accuracy and precision of the N2 washout/washin method in measuring FRC, by comparing it with set volumes in a lung simulator. Methods We conducted a diagnostic bench study in the Intensive Care Unit and Radiology Department of a tertiary hospital in Switzerland. Using a fully controllable high fidelity lung simulator (TestChest®), we set the functional residual capacity at 1500 ml, 2000 ml and 2500 ml and connected to the GE Carestation respirator, which includes the nitrogen washout/washin technique (INview™ tool). FRC was then set to vary by different levels of PEEP (5, 8, 12 and 15 cmH2O). The main outcome measures were bias and precision of the TestChest® when compared to the results from the washout/washin technique, according to the results of a Bland Altman Analysis. We verified our findings with volumetric computed tomography. Results One hundred and thirty-five nitrogen-wash-in/wash-out measurements were taken at three levels of FIO2 (0.4, 0.5, 0.6). The CT volumetry reproduced the set end-expiratory volumes at the Simulator with a bias of 4 ml. The nitrogen-wash-in/wash-out method had a bias of 603 ml with acceptable limits of agreement (95% CI 252 to − 953 ml). Changes were detected with a concordance rate of 97%. Conclusions We conclude that the TestChest® simulator is an accurate simulation tool, concerning the simulation of lung volumes. The nitrogen wash-in/wash out method correlated positively with FRC changes, despite a relatively large bias in absolute measurements. The reference volumes in the lung simulator verified with CT volumetry were very close to their expected values. The reason for the bias could not be determined.

Training Specificity of Inspiratory Muscle Training Methods: A Randomized Trial

IntroductionInspiratory muscle training (IMT) protocols are typically performed using pressure threshold loading with inspirations initiated from residual volume (RV). We aimed to compare effects of three different IMT protocols on maximal inspiratory pressures (PImax) and maximal inspiratory flow (V̇Imax) at three different lung volumes. We hypothesized that threshold loading performed from functional residual capacity (FRC) or tapered flow resistive loading (initiated from RV) would improve inspiratory muscle function over a larger range of lung volumes in comparison with the standard protocol.Methods48 healthy volunteers (42% male, age: 48 ± 9 years, PImax: 110 ± 28%pred, [mean ± SD]) were randomly assigned to perform three daily IMT sessions of pressure threshold loading (either initiated from RV or from FRC) or tapered flow resistive loading (initiated from RV) for 4 weeks. Sessions consisted of 30 breaths against the highest tolerable load. Before and after the training period, PImax was measured at RV, FRC, and midway between FRC and total lung capacity (1/2 IC). V̇Imax was measured at the same lung volumes against a range of external threshold loads.ResultsWhile PImax increased significantly at RV and at FRC in the group performing the standard training protocol (pressure threshold loading from RV), it increased significantly at all lung volumes in the two other training groups (all p &lt; 0.05). No significant changes in V̇Imax were observed in the group performing the standard protocol. Increases of V̇Imax were significantly larger at all lung volumes after tapered flow resistive loading, and at higher lung volumes (i.e., FRC and 1/2 IC) after pressure threshold loading from FRC in comparison with the standard protocol (all p &lt; 0.05).ConclusionOnly training with tapered flow resistive loading and pressure threshold loading from functional residual capacity resulted in consistent improvements in respiratory muscle function at higher lung volumes, whereas improvements after the standard protocol (pressure threshold loading from residual volume) were restricted to gains in PImax at lower lung volumes. Further research is warranted to investigate whether these results can be confirmed in larger samples of both healthy subjects and patients.

Respiratory physiology

Breathing and normal respiration must be understood by recovery room staff. This chapter explains how patients breathe and what is happening when patterns of respiration alter. Terms that sound complicated, like functional residual capacity, are explained and the way in which breathing is driven from the brain and by chemoreceptors in the lungs is simply described.

Comparison of inspiratory and expiratory lung and lobe volumes among supine, standing, and sitting positions using conventional and upright CT

Currently, no clinical studies have compared the inspiratory and expiratory volumes of unilateral lung or of each lobe among supine, standing, and sitting positions. In this prospective study, 100 asymptomatic volunteers underwent both low-radiation-dose conventional (supine position, with arms raised) and upright computed tomography (CT) (standing and sitting positions, with arms down) during inspiration and expiration breath-holds and pulmonary function test (PFT) on the same day. We compared the inspiratory/expiratory lung/lobe volumes on CT in the three positions. The inspiratory and expiratory bilateral upper and lower lobe and lung volumes were significantly higher in the standing/sitting positions than in the supine position (5.3–14.7% increases, all P < 0.001). However, the inspiratory right middle lobe volume remained similar in the three positions (all P > 0.15); the expiratory right middle lobe volume was significantly lower in the standing/sitting positions (16.3/14.1% decrease) than in the supine position (both P < 0.0001). The Pearson’s correlation coefficients (r) used to compare the total lung volumes on inspiratory CT in the supine/standing/sitting positions and the total lung capacity on PFT were 0.83/0.93/0.95, respectively. The r values comparing the total lung volumes on expiratory CT in the supine/standing/sitting positions and the functional residual capacity on PFT were 0.83/0.85/0.82, respectively. The r values comparing the total lung volume changes from expiration to inspiration on CT in the supine/standing/sitting positions and the inspiratory capacity on PFT were 0.53/0.62/0.65, respectively. The study results could impact preoperative CT volumetry of the lung in lung cancer patients (before lobectomy) for the prediction of postoperative residual pulmonary function, and could be used as the basis for elucidating undetermined pathological mechanisms. Furthermore, in addition to morphological evaluation of the chest, inspiratory and expiratory upright CT may be used as an alternative tool to predict lung volumes such as total lung capacity, functional residual capacity, and inspiratory capacity in situation in which PFT cannot be performed such as during an infectious disease pandemic, with relatively more accurate predictability compared with conventional supine CT.