Respiratory mechanics during NCPAP and HHHFNC at equal distending pressures

Objective: To compare the effect of heated, humidified, high-flow nasal cannula (HHHFNC) and nasal continuous positive airways pressure (NCPAP) on lung function and mechanics in preterm infants with respiratory distress syndrome (RDS) at the same level of retropharyngeal pressure (Prp). Design: Randomised crossover trial. Setting: Neonatal intensive care unit, Ospedale Maggiore Policlinico, Milan, Italy. Patients: 20 preterm infants (gestational age: 31\ub11 wks) with mild-moderate RDS requiring non-invasive respiratory support within 96 h after birth. Interventions: Infants were exposed to a randomised sequence of NCPAP and HHHFNC at different settings (2, 4 and 6 cmH2O for NCPAP and 2, 4, 6 L/min for HHHFNC) to enable comparison at the same level of Prp. Main outcome measures: Tidal volume by respiratory inductance plethysmography, pleural pressure estimated by oesophageal pressure, and gas exchange were evaluated at each setting and used to compute breathing pattern parameters, lung mechanics and work of breathing (WOB). Results: A poor linear regression between flow and Prp was found during HHHFNC (Prp=0.3+0.7*flow; r2=0.37). Only in 15 out of 20 infants it was possible to compare HHHFNC and NCPAP at a Prp of 2 and 4 cmH2O. No statistically significant differences were found in breathing pattern, gas exchange, lung mechanics and total WOB. Resistive WOB in the upper airways was slightly but significantly higher during HHHFNC (0.65 (0.49;1.09) vs 1.57 (0.85;2.09) cmH2O median (IQR)). Conclusions: Despite differing mechanisms for generating positive airway pressure, when compared at the same Prp, NCPAP and HHHFNC provide similar effects on all the outcomes explored

Within-breath input impedance by impulse oscillometry in severely asthmatic horses

Impulse oscillometry system (IOS) detects pulmonary obstruction in horses measuring average total respiratory system impedance (Zrs). In humans, analysis of within-breath changes of Zrs allows identification of the presence of expiratory flow limitation. Aims of this study were to describe the inspiratory and expiratory Zrs parameters measured by IOS in asthmatic horses and to determine whether they allow the detection of residual airway obstruction in asthmatic horses in disease remission. Seven severely asthmatic horses in disease exacerbation (HE), seven asthmatic horses in clinical remission (HR) and seven control horses (HC) from a cohort of experimental age-matched animals underwent IOS testing. Only data at 3, 5 and 7 Hz with coherence >0.85 at 3 Hz and >0.9 at 5 and 7 Hz were considered in this study. Mean, inspiratory and expiratory resistance (R) and reactance (X) and the difference between inspiratory and expiratory X (\u394X) were calculated at each frequency. The three groups were compared using Kruskal-Wallis and Dunn\u2019s multiple comparison tests. HE differed from HC for all R parameters at 3 Hz and all X parameters at all frequencies (P<0.01-0.001). HE differed from HR (P<0.05) for R3, R3e, X3e, X5e. HR differed from HC for X7i (P<0.05). \u394X was higher (P<0.05) in HE than in HC (5 Hz) or HR (all frequencies, P<0.01-0.001). Results indicate that as reported in humans during tidal expiratory flow limitation, Xrs during the expiratory phase is more negative than during inspiration in HE. Difference in X7i appears to be promising to discriminate between HC and HR

Positional effects on lung mechanics of ventilated preterm infants with acute and chronic lung disease

Background: The role of prone position in preterm infants has not been completely clarified. We investigated prone versus supine posture-related changes in respiratory system resistance (Rrs) and reactance (Xrs) measured by the Forced Oscillation Technique (FOT) in mechanically ventilated preterm newborns. Methods: Patients were studied in the supine versus prone positions in random order. Oxygen saturation, transcutaneous partial pressure of oxygen (ptcO2), carbon dioxide (ptcCO2), Rrs and Xrs were measured in each position. Results: Nine patients with respiratory distress syndrome (RDS) and nine with evolving broncho-pulmonary dysplasia (BPD) were studied. Rrs was, on average, 9.8 (1.3, 18.3 as 95%CI) cmH2O*s/l lower in the prone compared to the supine position (P=0.02), while no differences in Xrs, ptcO2, ptcCO2, and breathing pattern were observed between postures. Only patients with evolving BPD showed a significant reduction of Rrs from 69.0\ub127.4 to 53.0\ub116.7 cmH2O*s/l, P=0.01. No significant correlations were found between changes in lung mechanics and ptcO2, ptcCO2, or breathing pattern. Conclusions: On short-term basis, prone positioning does not offer significant advantages in lung mechanics in mechanically ventilated infants with RDS, while it is associated with lower Rrs values in patients with evolving BPD. \ua9 2014 Wiley Periodicals, Inc

Determinants of breathing effort sensation in normoxia and hypobaric hypoxia

none13Thesensationofbreathingeffortisthoughttobetheresultofacomplexintegra- tion ofdifferentsensoryinputsincludingchemical-,mechanical- andneural-based signals.Wewishedtoexplorethedeterminants ofbreathingeffortsensation(BES) duringexhaustingexerciseinnormobaricnormoxiaandhypobarichypoxia.Eleven non-smokinghealthymalesubjects(age41[14],mean[SD]yr)werestudiedduring incrementalcycleexercise(30watt/3min)untilexhaustion(WLmax)atsealevel (SL)andafter2-3daysat4559meters(ALT).WemeasuredBES(Borgscale), ventilation(V’E),tidalvolume(Vt),respiratoryrate(RR),oxygensaturation(Sat), workofbreathing(fromdynamicesophagealpressure-volumeloops,WOB),total breathingmechanicalpoweroutput(W’=WOB*RR)andenergycostofbreathing perunitventilation(WOB/V’E). ComparedtoSL,atALTV’EandSatwerehigher(p<0.001forboth)foranywork- load.WLmaxwas15[8]%lowerthanSL(p<0.001).TheBESvsV’Erelationship wassimilaratALTcomparedtoSL.WithincreasingV’E,W’wasprogressively loweratALTthanatSL(p<0.001)asaconsequenceofaprogressivelyreduced flowresistivework.BeyondV’E>∼50 L/minBESwasprogressivelyhigherat ALTcomparedtoSLforagivenWOB/V’E.Yet,thechangesofVtandRR remainedsimilaratanylevelofventilationonbothconditions. In conclusionbreathingeffortsensationappearsuniquelyrelatedtoventilation, despitethedifferencesincostofbreathingandmetabolicrequirementsatALTand SL.noneA.Aliverti; A.LoMauro; M.Quaranta; P.Pompilio; R.Dellacà; M.Milanese; L. Pomidori ; L. Cavalleri; V. Fasano; A. Cogo; R. Pellegrino ; B. Kayser; G. MiserocchiA., Aliverti; A., Lomauro; M., Quaranta; P., Pompilio; R., Dellacà; M., Milanese; Pomidori, Luca; L., Cavalleri; V., Fasano; Cogo, Annaluisa; R., Pellegrino; B., Kayser; G., Miserocch