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Abstract Guidelines and instructions derived from adult randomized controlled trials are generally followed in pediatric ventilation, as there have been no large trials of this kind in children. Current treatment strategies aim at preventing ventilator-induced lung injury by avoiding too large tidal volumes, supporting patient's spontaneous breathing and preventing lung collapse with positive end-expiratory airway pressure. Neurally adjusted ventilatory assist (NAVA) is a novel ventilation mode that provides respiratory support proportional to the electrical activity of the diaphragm (Edi). The aims of this thesis were to assess daily practices in pediatric ventilation in Finland and to compare NAVA with conventional ventilation in terms of safety and quality of care. Current treatment practices were studied with a preliminary enquiry and a 3-month prospective survey that was offered to all hospital units providing ventilatory care for children <16 years of age. NAVA was compared with current standard ventilation in a crossover trial involving 18 pediatric patients and in a larger controlled trial in which 170 patients were randomized to receive either NAVA or conventional ventilation. Respiratory distress was the most common indication for invasive ventilation in neonates, and postoperative care in older children. The principles of lung-protective ventilation were generally accepted and the goals were achieved in the majority of treatment episodes. The low incidence of pediatric invasive ventilation favours centralization. NAVA proved to be a safe and feasible primary ventilation mode in pediatric intensive care. It improved patient-ventilator synchrony and led to lower peak inspiratory pressures and oxygen requirements. It also reduced the need for sedation during longer treatment periods. Information derived from the Edi-signal could be used to optimize the level of sedation and to identify patients with a potential risk of extubation failure. / Tiivistelmä Nykyisin käytössä olevat menetelmät lasten hengityskonehoidossa perustuvat suurelta osin aikuisilla tehtyihin tutkimuksiin ja totuttuihin tapoihin, sillä lasten hengityskonehoidosta on olemassa vain vähän tutkittua tietoa. Hengityskonehoidon aiheuttamaa keuhkovauriota pyritään ehkäisemään välttämällä suuria kertahengitystilavuuksia, tukemalla potilaan omia hengityksiä ja säilyttämällä ilmateissä positiivinen paine uloshengityksen aikanakin. Neuraalisesti ohjattu ventilaatio (NAVA) on uusi hengityskonehoitomuoto, joka tukee potilaan omia hengityksiä ohjaamalla koneen antamaa tukea pallealihaksen sähköisen signaalin avulla. Tämän tutkimuksen tavoitteena oli selvittää lasten hengityskonehoidon nykytilaa Suomessa sekä tutkia, voidaanko NAVAa käyttämällä parantaa hoidon laatua ja turvallisuutta. Nykyisiä hoitokäytäntöjä selvitettiin vuonna 2010 kysely- ja seurantatutkimuksella, johon kutsuttiin mukaan kaikki Suomessa lapsia ja vastasyntyneitä hoitavat tehohoito-osastot. NAVAa verrattiin nykyiseen hengityskonehoitoon 18 potilaan vaihtovuoroisessa tutkimuksessa sekä suuremmassa 170 lapsipotilaan satunnaistetussa kontrolloidussa tutkimuksessa. Eri syistä johtuvat hengitysvaikeudet ovat yleisin syy hengityskonehoitoon vastasyntyneillä ja suurten leikkausten jälkeinen hoito isommilla lapsilla. Keuhkoja säästävän hoidon periaatteet ovat Suomessa yleisesti hyväksyttyjä ja toteutuvat valtaosassa hoitojaksoja. Hengityskonehoitojaksojen määrän vähäisyys puoltaa hoidon keskittämistä suuriin sairaaloihin. NAVAa käyttämällä hengityskoneen antama tuki ajoittuu paremmin potilaan omien hengitysten mukaan ja sen avulla saavutetaan matalammat ilmatiepaineet sekä vähäisempi lisähapen tarve. Pitkissä hoitojaksoissa NAVA vähentää rauhoittavan lääkityksen tarvetta, ja pallealihaksen signaalia seuraamalla on mahdollista optimoida sedaatioaste aikaisempaa tarkemmin. Palleasignaalia voidaan myös hyödyntää arvioitaessa potilaan valmiutta hengitystuesta vieroittamiseen.

Background: General anesthesia usually requires mechanical ventilation, which is traditionally accomplished with constant tidal volumes in volume- or pressure-controlled modes. Experimental studies suggest that the use of variable tidal volumes (variable ventilation) recruits lung tissue, improves pulmonary function and reduces systemic inflammatory response. However, it is currently not known whether patients undergoing open abdominal surgery might benefit from intraoperative variable ventilation. Methods/Design: The PROtective VARiable ventilation trial ('PROVAR') is a single center, randomized controlled trial enrolling 50 patients who are planning for open abdominal surgery expected to last longer than 3 hours. PROVAR compares conventional (non-variable) lung protective ventilation (CV) with variable lung protective ventilation (VV) regarding pulmonary function and inflammatory response. The primary endpoint of the study is the forced vital capacity on the first postoperative day. Secondary endpoints include further lung function tests, plasma cytokine levels, spatial distribution of ventilation assessed by means of electrical impedance tomography and postoperative pulmonary complications. Discussion: We hypothesize that VV improves lung function and reduces systemic inflammatory response compared to CV in patients receiving mechanical ventilation during general anesthesia for open abdominal surgery longer than 3 hours. PROVAR is the first randomized controlled trial aiming at intra- and postoperative effects of VV on lung function. This study may help to define the role of VV during general anesthesia requiring mechanical ventilation.

Thoracic surgical procedures require partial or complete airway separation and the opportunity to exclude one lung from ventilation (one-lung ventilation, OLV). OLV is commonly associated with profound pathophysiological changes that may affect the postoperative outcome. It is injurious in terms of increased mechanical stress including alveolar cell stretch and overdistension, shear forces secondary to repeated tidal collapse and reopening of alveolar units and compression of alveolar vessels. Ventilation and perfusion distribution may thus be affected during and after OLV. The present studies investigated the influence of OLV on ventilation and perfusion distribution, on the gas/tissue distribution and on the lung histomorphology in a pig model of thoracic surgery. Anaesthetised and mechanically ventilated piglets were examined. The ventilation and perfusion distribution within the lungs was assessed by single photon emission computed tomography. Computed tomography was used to establish the effects of OLV on dependent lung gas/tissue distribution. The pulmonary histopathology of pigs undergoing OLV and thoracic surgery was compared with that of two-lung ventilation (TLV) and spontaneous breathing. OLV induced hyperperfusion and significant V/Q mismatch in the ventilated lung persistent in the postoperative course. It increased cyclic tidal recruitment that was associated with a persistent increase of gas content in the ventilated lung. OLV and thoracic surgery as well resulted in alveolar damage.  In the present model of OLV and thoracic surgery, alveolar recruitment manoeuvre (ARM) and protective ventilation approach using low tidal volume preserved the ventilated lung density distribution and did not aggravate cyclic recruitment of alveoli in the ventilated lung. In conclusion, the present model established significant alveolar damage in response to OLV and thoracic surgery. Lung injury could be related to the profound pathophysiological consequences of OLV including hyperperfusion, ventilation/perfusion mismatch and increased tidal recruitment of lung tissue in the dependent, ventilated lung.  These mechanisms may contribute to the increased susceptibility for respiratory complications in patients undergoing thoracic surgery. A protective approach including sufficient ARM, application of PEEP, and the use of lower tidal volumes may prevent the ventilated lung from deleterious consequences of OLV.

L’association lésionnelle d’une contusion pulmonaire et d’un état de choc hémorragique est fréquente et constitue un réel chalenge thérapeutique. La prise en charge de ce choc va nécessiter une réanimation hémodynamique dans laquelle le remplissage vasculaire tient une place centrale. Mais dans ce contexte de poumon contus, il devra être raisonné car délétère sur le plan pulmonaire, notamment en terme d'oedème et d'altération de la compliance. Ce remplissage devra donc être titré, basé sur des objectifs tensionnels clairs et un monitorage hémodynamique fiable. L'utilisation de solutés à haut pouvoir d'expansion volémique (sérum salé hypertonique, colloïdes) présente un intérêt, de même que l'introduction précoce de vasopresseurs. Le monitorage hémodynamique permettra de conduire cette réanimation sur des objectifs de pression artérielle, sur des indices de précharge dépendance et sur la mesure de l'eau pulmonaire extravasculaire. Notre travail, basé sur des études expérimentales et cliniques, a pour objectif de caractériser les modalités actuelles de prise en charge d’une contusion pulmonaire, sur les plans hémodynamiques et respiratoires. / Pulmonary contusion is often associated with hemorrhagic shock, constituting a challenge in trauma care. For patients who have sustained lung contusions, fluid resuscitation should be carefully performed, because injured lungs are particularly vulnerable to massive fluid infusions with an increased risk of pulmonary edema and compliance impairment. Fluid administration should be included in an optimized and goal directed resuscitation, based on blood pressure objectives and hemodynamical monitoring. The use of fluids with high volume-expanding capacities (hypertonic saline, colloids) is probably interesting, as well as early introduction of vasopressors. Hemodynamic monitoring will allow to conduct resuscitation on blood pressure objectives, on preload parameters and on extravascular lung water measurement.Our work, based on experimental and clinical studies, objective to characterize the current modalities of ventilatory and hemodynamical aspect of pulmonary contusion care.

Background: General anesthesia usually requires mechanical ventilation, which is traditionally accomplished with constant tidal volumes in volume- or pressure-controlled modes. Experimental studies suggest that the use of variable tidal volumes (variable ventilation) recruits lung tissue, improves pulmonary function and reduces systemic inflammatory response. However, it is currently not known whether patients undergoing open abdominal surgery might benefit from intraoperative variable ventilation. Methods/Design: The PROtective VARiable ventilation trial ('PROVAR') is a single center, randomized controlled trial enrolling 50 patients who are planning for open abdominal surgery expected to last longer than 3 hours. PROVAR compares conventional (non-variable) lung protective ventilation (CV) with variable lung protective ventilation (VV) regarding pulmonary function and inflammatory response. The primary endpoint of the study is the forced vital capacity on the first postoperative day. Secondary endpoints include further lung function tests, plasma cytokine levels, spatial distribution of ventilation assessed by means of electrical impedance tomography and postoperative pulmonary complications. Discussion: We hypothesize that VV improves lung function and reduces systemic inflammatory response compared to CV in patients receiving mechanical ventilation during general anesthesia for open abdominal surgery longer than 3 hours. PROVAR is the first randomized controlled trial aiming at intra- and postoperative effects of VV on lung function. This study may help to define the role of VV during general anesthesia requiring mechanical ventilation.