Conventional Positive Pressure Ventilation Research Articles

High frequency percussive ventilation: An asset to existing ventilation modi in intraoperative care?

High frequency percussive ventilation (HFPV) is a ventilation mode that combines positive pressure ventilation with some advantages of high frequency ventilation. During HFPV, a pulsatile flow is generated with high frequency and low volumes. HFPV has been used in the intensive care unit (ICU) for several decades, in case of insufficient conventional positive pressure ventilation. However, literature on its use in intraoperative care is scarce. We hypothesize that HFPV might be a better alternative to existing ventilation modi during selected operative procedures or in patients with severely compromised pulmonary and/or cardiac function. In this paper, we explain the HFPV system, we zoom in on the physiological effects of HFPV, and we describe its potential role in the intraoperative setting. Results of existing studies show that, compared to other conventional ventilation modes, HFPV improves oxygenation and ventilation without jeopardizing hemodynamics. However, because of the low quality evidence regarding physiological effects and clinical effectiveness, and due to the complicated design and set-up of the HFPV ventilator, the use of HFPV in intraoperative care is currently very limited. We conclude that HFPV could potentially be an interesting ventilation mode for procedures requiring minimal respiratory motion or low airway pressures, however larger (comparative) study trials are required to evaluate its usability in the operating room in patients with compromised pulmonary and/or cardiac function.

A Novel Negative Pressure-Flow Waveform to Ventilate Lungs for Normothermic Ex Vivo Lung Perfusion.

Ex vivo lung perfusion (EVLP) is increasingly used to treat and assess lungs before transplant. Minimizing ventilator induced lung injury (VILI) during EVLP is an important clinical need, and negative pressure ventilation (NPV) may reduce VILI compared with conventional positive pressure ventilation (PPV). However, it is not clear if NPV is intrinsically lung protective or if differences in respiratory pressure-flow waveforms are responsible for reduced VILI during NPV. In this study, we quantified lung injury using novel pressure-flow waveforms during normothermic EVLP. Rat lungs were ventilated-perfused ex vivo for 2 hours using tidal volume, positive end-expiratory pressure (PEEP), and respiratory rate matched PPV or NPV protocols. Airway pressures and flow rates were measured in real time and lungs were assessed for changes in compliance, pulmonary vascular resistance, oxygenation, edema, and cytokine secretion. Negative pressure ventilation lungs demonstrated reduced proinflammatory cytokine secretion, reduced weight gain, and reduced pulmonary vascular resistance (p < 0.05). Compliance was higher in NPV lungs (p < 0.05), and there was no difference in oxygenation between the two groups. Respiratory pressure-flow waveforms during NPV and PPV were significantly different (p < 0.05), especially during the inspiratory phase, where the NPV group exhibited rapid time-dependent changes in pressure and airflow whereas the PPV group exhibited slower changes in airflow/pressures. Lungs ventilated with PPV also had a greater transpulmonary pressure (p < 0.05). Greater improvement in lung function during NPV EVLP may be caused by favorable airflow patterns and/or pressure dynamics, which may better mimic human respiratory patterns.

Safe Use of Flammable Endotracheal Tubes During Anesthesia for Laryngeal Laser Surgery-Report of 1024 Cases and a Brief Literature Review.

One of the major concerns in laryngeal laser surgery is the risk of airway fire. The introduction ofwrapped tubes and metal tubes has reduced the fire hazards. However, these tubes are expensive and do not provide convenient access to the surgical field. There are few laboratory studies addressing the resistance of polyvinylchloride tubes against ignition in the given circumstances. Nevertheless, its safety should be approved in clinical practices. This retrospective studyevaluated the airway management on 1024 patients undergoing laryngeal laser surgery. The data collection included the information about the type of endotracheal tube (ETT), mode of ventilation, and airway hazards (e.g., tube ignition). Polyvinylchloride tubes and conventional positive pressure ventilation was applied for most of the patients (84.1%). The tube cuff was pierced with laser beam in 22 cases (2.5%). However, there was no case of ETT ignition or airway fire. Polyvinylchloride tubes can be safely used in this subset of surgeries pending meticulous attention to the safety recommendations.

Effects of Lung Protective Ventilation on the Cognitive Function Level of Patients with Esophageal Cancer

We intended to investigate the effects of lung protective ventilation on the cognitive function level of patients with esophageal cancer. Overall, 132 patients with esophageal cancer admitted to Taian Central Hospital, Taian China from January 2013 to January 2017 were enrolled in the study. According to the random number table method, they were divided into observation group and control group, 66 cases each. All patients underwent general anesthesia for thoracoscopic esophageal cancer radical operation, and lung protective ventilation and conventional positive pressure ventilation were used respectively. The levels of SOD, NSE and MDA, MMSE score and WMS memory quotient in the blood of the elbow vein were compared between the two groups at different times. The levels of SOD and MMSE in the observation group at T2 and T3 were higher than those in the control group, and the NSE and MDA levels were lower than those in the control group (P=0.013, 0.033, 0.015, 0.044, 0.034, 0.029, 0.014, 0.017). The incidence of postoperative cognitive impairment was lower in the observation group than in the control group (P=0.007). The WMS memory quotient scores of the patients in the T2, T3, and T4 observation groups were higher than those in the control group (p=0.009, 0.032, 0.040). Lung protective ventilation can reduce the oxidative stress injury for patients and improve their postoperative cognitive function and memory ability.

Automated expiratory ventilation assistance through a small endotracheal tube can improve venous return and cardiac output

BackgroundPositive pressure ventilation can decrease venous return and cardiac output. It is not known if expiratory ventilation assistance (EVA) through a small endotracheal tube can improve venous return and cardiac output.ResultsIn a porcine model, switching from conventional positive pressure ventilation to (EVA) with − 8 cmH20 expiratory pressure increased the venous return and cardiac output. The stroke volume increased by 27% when the subjects were switched from conventional ventilation to EVA [53.8 ± 7.7 (SD) vs. 68.1 ± 7.7 ml, p = 0.003]. After hemorrhage, subjects treated with EVA had higher median cardiac output, higher mean systemic arterial pressure, and lower central venous pressure at 40 and 60 min when compared with subjects treated with conventional ventilation with PEEP 0 cmH20. The median cardiac output was 41% higher in the EVA group than the control group at 60 min [2.70 vs. 1.59 L/min, p = 0.029].ConclusionEVA through a small endotracheal tube increased venous return, cardiac output, and mean arterial pressure compared with conventional positive pressure ventilation. The effects were most significant during hypovolemia from hemorrhage. EVA provided less effective ventilation than conventional positive pressure ventilation.

High-Frequency Jet Ventilation for HIFU

We read the review by Muller et al. [1] about the management of respiratory motion in high-intensity focused ultrasound with great interest. As acknowledged by the authors, the motion of abdominal organs due to ventilation is sometimes a main obstacle for interventional radiology [2]. This is a critical issue for HIFU treatment where energy deposits in tissue are small and where precise overlap of each deposit is mandatory. The authors present many solutions more or less adapted to the HIFU technique. For one solution, the authors use high-frequency jet ventilation as a potentially useful tool. However, careful evaluation of the publications quoted in their paper did not show a study with a prospective organ movement measurement in humans using this technique. We have recently published a prospective trial on HFJV for percutaneous tumor ablation in 50 patients [3]. In this series, we could demonstrate two important points that are of interest for readers. First, we demonstrated that during HFJV for hepatic and pulmonary radiofrequency ablation (RFA), the mean movement of target close to the diaphragm was 0.3 ± 0.12, 0.3 ± 0.13, and less than 3.75 mm in x, y, and z directions respectively (mean ± SD). The movement in the z direction is probably lower than 3.75 mm, but due to the slice thickness used in our protocol we were not able to give more precise measure in the z direction. Interestingly in our study, some patients could not be treated using HFJV. They were patients with small tumors highly located in the liver dome area. These lesions could not be reached, because HFJV ventilates the patient in a position near of end expiration. The lesions were then nonvisible under US guidance and a transthoracic approach would have been necessary for needle positioning under CT guidance. This also might be an issue for HIFU, because an ultrasonographic window is necessary for energy deposition in the tissue. This problem was easily solved, because we could switch from HFJV to conventional positive pressure ventilation easily. HFJV, which was claimed by some authors [4] to be a ventilation method that could not be used for long period of time due to a risk of atelectasia and hypercapnia, was actually used for long period of time in our study (mean 2 h) without treatment discontinuation due to ventilation problem. HFJV has the ability to solve all the anesthetic and ventilation issues related to HIFU: a nearly immobile organ even close to the diaphragm, a ventilation method for long procedure. The only remaining problem could be deeply located lesion close to the liver dome that may be obscured by the lung when using this ventilation method. C. Courbon (&) M. Chollet Rivier Anesthesiology Department, CHUV, Rue du Bugnon, 46 1001 Lausanne, Switzerland e-mail: Cecile.Courbon@chuv.ch

Use of high-frequency oscillatory ventilation with inhaled nitric oxide in congenital diaphragmatic hernia, omphalocele, and patent ductus arteriosus.

Use of high-frequency oscillatory ventilation with inhaled nitric oxide in congenital diaphragmatic hernia, omphalocele, and patent ductus arteriosus.

Sevoflurane Inhalation for Severe Bronchial Obstruction in Infants with Bronchiolitis

Bronchiolitis is a lower respiratory tract viral infection which may result in severe bronchial obstruction and respiratory failure despite treatment with beta-adrenergic agonists and glucocorticoids. Here we describe two otherwise healthy infants with severe bronchiolitis whose clinical course was complicated by marked bronchial obstruction and respiratory acidosis refractory to conventional medications (β-stimulants, anticholinergics and corticosteroids) and non-invasive positive pressure ventilation. Sevoflurane inhalation allowed both infants to attain a sustained, clinical improvement in ventilation and one patient to avoid mechanical ventilation. We suggest that sevoflurane inhalation may be a therapeutic option in the treatment of young infants with severe bronchiolitis who respond poorly to conventional therapy.

Anesthetic Management of Patients Undergoing Pulmonary Vein Isolation for Treatment of Atrial Fibrillation Using High-Frequency Jet Ventilation

The aim of this study was to describe anesthetic management and perioperative complications in patients undergoing pulmonary vein isolation for the treatment of atrial fibrillation under general anesthesia using high-frequency jet ventilation. The authors also identified variables associated with longer ablation times in this patient cohort. A retrospective observational study. The electrophysiology laboratory in a major university hospital. One hundred eighty-eight consecutive patients undergoing pulmonary vein isolation under general anesthesia with high-frequency jet ventilation. High-frequency jet ventilation was used as the primary mode of ventilation under general anesthesia. High-frequency jet ventilation was performed successfully throughout the ablation procedure in 175 cases of the study cohort. The remaining 13 patients had to be converted to conventional positive-pressure ventilation because of high PaCO(2) or low PaO(2) on arterial blood gas measurements. Variables associated with a shorter ablation time included a higher ejection fraction (p = 0.04) and case volume performed by each electrophysiologist in the study group (p = 0.001). High-frequency jet ventilation is generally a safe technique that can be used in catheter ablation treatment under general anesthesia.

Negative-Pressure Ventilation

Conventional positive-pressure ventilation delivers pressure to the airways; in contrast, negative pressure is delivered globally to the chest and abdomen. To test the hypothesis that ventilation with negative pressure results in better oxygenation and less injury than with positive pressure. Anesthetized, surfactant-depleted rabbits were ventilated for 2.5 hours in pairs (positive or negative). Tidal volume was 12 ml . kg(-1), normocapnia was maintained by adjusting respiratory rate, and Fi(O(2)) was 1.0. Lung injury was assessed with histologic scoring, perfusion using thermodilution (global perfusion), and injected intravascular microspheres (regional perfusion); and dynamic computed tomography was used to determine inflation patterns. Negative pressure was associated with a higher Pa(O(2)), a lower Pa-Pet(CO(2)) gradient (despite identical minute ventilation), and less lung injury. Lung perfusion (global and regional) was similar with positive and negative pressure. Positive end-expiratory pressure applied to the airway was more efficiently transmitted to the pleural space than comparable levels of negative end-expiratory pressure applied to the chest wall; however, the oxygenation associated with any level of end-expiratory lung volume was greater when achieved by negative versus positive pressure. Dynamic computed tomography suggested that lung distension achieved with negative pressure is characterized by greater proportions of normally aerated lung (with less atelectasis) during inspiration and at end-expiration. Negative-pressure ventilation results in superior oxygenation that is unrelated to lung perfusion and may be explained by more effective inflation of lung volume during both inspiration and expiration.

Open lung ventilation preserves the response to delayed surfactant treatment in surfactant-deficient newborn piglets

Delayed surfactant treatment (>2 hrs after birth) is less effective than early treatment in conventionally ventilated preterm infants with respiratory distress syndrome. The objective of this study was to evaluate if this time-dependent efficacy of surfactant treatment is also present during open lung ventilation. Prospective, randomized controlled animal study. University-affiliated research laboratory. Thirty-eight newborn piglets. Following repeated whole-lung lavage, animals were randomly allocated to conventional positive pressure ventilation (PPVCON) using a positive end-expiratory pressure (PEEP) of 5 cm H2O and a tidal volume of 7 mL/kg or open lung positive pressure ventilation (PPVOLV). During PPVOLV, collapsed alveoli were actively recruited and thereafter stabilized with sufficient PEEP. Within each ventilation group, animals received surfactant (25 mg/kg) either after 2 hrs (PPVCON-2 and PPVOLV-2) or after 4 hrs (PPVCON-4 and PPVOLV-4) of ventilation. A control group received surfactant immediately after lung lavage. Following surfactant administration, all animals were conventionally ventilated for an additional 2 hrs. Two hours after surfactant treatment, both oxygenation and lung mechanics showed a clear deterioration in the PPVCON-4 group compared with PPVCON-2 and the control group. However, this deterioration of the surfactant response over time was not observed during PPVOLV. Analysis of the bronchoalveolar lavage fluid obtained at the end of the experiment showed that the protein concentration and the conversion of large to small aggregate surfactant was significantly higher in the PPVCON-4 group compared with the PPVCON-2 group while comparable in both PPVOLV groups. In addition, interleukin-8 and myeloperoxidase levels tended to be higher in the PPVCON-4 group compared with the PPVOLV-4 group. In contrast to conventional ventilation, open lung ventilation preserves the response to delayed surfactant treatment in surfactant-deficient newborn piglets. This sustained response is accompanied by an attenuation of secondary lung injury.

Extending the limits of extracorporeal membrane oxygenation: lung rest for a child with non-specific interstitial pneumonia

Veno-venous extracorporeal membrane oxygenation (ECMO) is an established therapy for the treatment of respiratory failure. Traditionally ECMO has been used to support patients with an acute, reversible disease process, with a predictable outcome. We report the successful use of veno-venous ECMO for an unusual indication. A 10-year old girl was admitted to intensive care with severe, hypoxic respiratory failure on the background of a 2-month history of worsening respiratory symptoms. She required high levels of conventional positive pressure ventilation, and high frequency oscillation. Lung biopsy confirmed a non-specific interstitial pneumonia, and the patient was commenced on immune suppressive therapy. Her clinical course was further complicated by pulmonary haemorrhage and severe air leak. On day 20 after admission the patient was placed on veno-venous ECMO for lung rest while awaiting a response to continued medical treatment. She required ECMO for 20 days, during which time sedation was reduced, and she was able to interact with those around her. The patient's ventilatory requirements after decannulation were minimal, and she subsequently made a steady clinical recovery. ECMO was safely and successfully used to provide a period of lung rest and time for medical therapy to take effect in a child with an unusual indication for support: a rare disease with an uncertain outcome on the background of prolonged mechanical ventilation.

Indications for Noninvasive Positive Pressure Ventilation

Noninvasive positive pressure ventilation (NPPV) is not a new concept. Noninvasive intermittent positive pressure ventilation using a mouthpiece or facemask has been used since the early 1960s. With the recognition of NPPV’s advantages, NPPV has become increasingly popular over the last decade in caring for patients with acute respiratory failure (ARF). NPPV, which uses a facial or nasal mask as an interface between the patient and the mechanical ventilator, can be available within a few minutes in a well-prepared intensive care unit (ICU). NPPV can reduce the likelihood of ventilator-associated pneumonia (VAP) by avoiding endotracheal tube intubation (ETI) compared with conventional positive pressure ventilation using an endotracheal tube (invasive PPV, IPPV). The inherent disadvantages of NPPV are related to the absence of the advantages acquired by ETI. The best candidates for NPPV are those able to protect their airway, are cooperative, and are otherwise medically stable. NPPV can be applied in community hospitals. With the accumulation of positive data for the beneficial effect of NPPVon ARF, NPPV has been recommended as a first-line intervention in patients with acute hypercapnic and hypoxemic respiratory failure. However, there is concern that the efficacy of NPPV is overrated. This chapter briefly reviews the indications of NPPV, which have been broadened.

Open lung ventilation improves gas exchange and attenuates secondary lung injury in a piglet model of meconium aspiration.

Previous studies failed to show clear benefits of high-frequency ventilation compared with conventional positive pressure ventilation (PPV(CON)) in experimental meconium aspiration syndrome. However, none of these studies applied an open lung ventilation strategy (OLC), which aims to reduce intrapulmonary shunt due to alveolar collapse. We hypothesized that, if combined with an open lung strategy, both high-frequency oscillatory ventilation (HFOV(OLC)) and positive pressure ventilation (PPV(OLC)) would improve gas exchange and attenuate ventilator-induced lung injury in experimental meconium aspiration syndrome. Prospective, randomized animal study. Research laboratory of a large university. Forty-two newborn piglets. Thirty minutes after intratracheal meconium instillation, 36 newborn piglets were assigned to one of three ventilation groups-PPV(OLC), HFOV(OLC), or PPV(CON)-and ventilated for 5 hrs. In both OLC groups, collapsed alveoli were actively recruited and thereafter stabilized using the lowest possible airway pressures. During PPV(CON), ventilator settings were adjusted to prevent critical hypoxia (Pao2 <60 torr [8 kPa]). Six animals served as saline controls. Compared with the PPV(CON) group, arterial oxygenation and lung mechanics were superior in both OLC groups and the saline controls. Analysis of the bronchoalveolar lavage fluid obtained after 5 hrs of ventilation showed increased myeloperoxidase activity in the PPV(CON) group compared with both OLC groups and saline controls. Alveolar protein influx was not different between the groups. Histologic analysis revealed a higher lung injury score in the PPV(CON) group compared with the PPV(OLC) and the HFOV(OLC) groups. Application of the OLC during PPV and HFOV is feasible in experimental meconium aspiration syndrome and results in superior oxygenation and less ventilator-induced lung injury compared with PPV(CON).

Changes in mean airway pressure during HFOV influences cardiac output in neonates and infants.

Changes in mean airway pressure affect cardiac output during conventional positive pressure ventilation. The effect of high-frequency oscillation ventilation (HFOV) on cardiac output is less studied. A prospective study in a university hospital pediatric intensive care unit. Fourteen patients aged <1 year and weighing <10 kg who were on HFOV were included. All patients had been on HFOV for >12 h and were considered to be in a stable condition. In the study group (n = 9) the mean proximal airway pressure (Paw) was increased and decreased by +5 and -3 cmH2O, respectively, from baseline in each patient. Measurements were made at each level including baseline settings between each change. In a control group (n = 5) no changes in ventilatory parameters were made. Cardiac output was assessed with echocardiography and the Doppler technique at each level of Paw and at similar intervals in the control group. Cardiac output changed significantly when Paw was changed in the study group (P = 0.02), with the greatest change at the highest Paw at -11% (range: -19 to -9) compared with baseline. We found no significant changes over time in the control group. This study shows that CO is affected by changes in mean airway pressure during HFOV in concordance with the known effects of mean airway pressure during conventional positive pressure ventilation. The mean changes are smaller than expected compared with earlier studies of conventional mechanical ventilation. Further studies are needed to better understand these relationships.

Application of the Open-Lung Concept during Positive-Pressure Ventilation Reduces Pulmonary Inflammation in Newborn Piglets

It has been shown that application of the open-lung concept (OLC) during high-frequency oscillatory ventilation (HFOV) attenuates pulmonary inflammation. We hypothesized that this attenuation could also be achieved by applying the OLC during positive-pressure ventilation (PPV). After repeated whole-lung lavage, newborn piglets were assigned to one of three ventilation groups: (1) PPV_OLC; (2) HFOV_OLC, or (3) conventional PPV (PPV_CON). After a ventilation period of 5 h, analysis of bronchoalveolar lavage fluid showed a reduced influx of polymorphonuclear neutrophils, interleukin 8, and thrombin activity in both OLC groups as compared with the PPV_CON group. There were no differences in tumor necrosis factor alpha levels. We conclude that application of the OLC during PPV reduces pulmonary inflammation as compared with conventional PPV and that the magnitude of this reduction is comparable to that of HFOV.

Specific compliance and gas exchange during high-frequency oscillatory ventilation.

To evaluate the use of specific compliance (static compliance/functional residual capacity) to adjust mean airway pressure, resulting in optimal gas exchange during high-frequency oscillatory ventilation in a surfactant-deficient newborn piglet. Prospective controlled animal study. Laboratory. Eight newborn piglets at 5 days of age. High-frequency oscillatory ventilation enables the use of relatively high mean airway pressures without the lung damage associated with conventional positive pressure ventilation. Mean airway pressures can be increased, resulting in static lung expansion that approaches total lung capacity with its negative impact on venous return. Therefore, knowledge of lung volume is important for safe patient management. A simple, noninvasive technique to enable the clinician to determine the optimal mean airway pressure likely would improve patient management. The lungs were lavaged after placement of central catheters and tracheostomy to lower respiratory system compliance and worsen ventilation perfusion matching. The animals were ventilated with high-frequency oscillatory ventilation at the same mean airway pressure as before lung lavage. Mean airway pressures then were increased in a step-wise fashion up to 30 cm H2O or until clinical deterioration occurred. All other ventilator variables, Fio2, frequency, and pressure amplitude were constant throughout the experiment. Before lavage and at each level of mean airway pressure after lung lavage, respiratory system compliance and functional residual capacity were measured. Additionally, central arterial pressure, central venous pressure, heart rate, arterial blood gas, and pulse oximetric saturation were recorded. Lung lavage significantly lowered respiratory system compliance (static as well as specific compliance) and worsened ventilation perfusion matching as evidenced by an increase in Paco2 and a decreased arterial to alveolar oxygen ratio. With increasing mean airway pressures, static/specific compliance improved and then peaked before declining, functional residual capacity increased, and blood gas improved until reaching the flat portion of the pressure-volume relationship of the lung. Optimal gas exchange as reflected by the highest arterial to alveolar oxygen ratio and lowest Paco2 at constant ventilation was found at a mean airway pressure that maintained the functional residual capacity and static respiratory system compliance at the same level as the preinjury levels ("normalized" functional residual capacity and respiratory system compliance). These results suggest that specific compliance measurement that incorporates static respiratory system compliance and functional residual capacity during high-frequency oscillatory ventilation can be used to adjust mean airway pressure and achieve "normalized" functional residual capacity, static compliance, and gas exchange. These measurements may provide a simple method to optimize lung volume in a surfactant-deficient patient during high-frequency oscillatory ventilation.

Transtracheal Oxygenation: An Alternative to Endotracheal Intubation During Cardiac Arrest

Because efforts to secure adequate arterial oxygenation during cardiac resuscitation are more important than efforts to promote CO(2) elimination, we investigated whether continuous transtracheal oxygenation (TTO) could represent a potentially simpler alternative to conventional positive-pressure ventilation with 100% O(2) through an endotracheal tube. Controlled and randomized. Animal laboratory. Thirty male Sprague-Dawley rats. The technique for TTO was initially developed and tested in five rats. A model of ventricular fibrillation (VF) was then used to compare the effects of TTO (n = 5) with the effects of O(2) delivery through an endotracheal tube as part of positive-pressure ventilation (n = 5) or through a mask without additional airway intervention (n = 5). VF was induced and left untreated for 4 min, after which chest compression and one of the three oxygenation interventions was started. Defibrillation was attempted after 6 min of chest compression. In a subsequent series, defibrillation was attempted after 10 min of chest compression in rats treated with either TTO (n = 5) or endotracheal intubation (ET; n = 5). TTO and ET secured adequate arterial PO(2) during chest compression (213 +/- 77 mm Hg and 154 +/- 36 mm Hg; not significant), whereas the mask yielded an arterial PO(2) of only 49 +/- 38 mm Hg (p < 0.05). Each rat treated with TTO or ET was successfully resuscitated and survived the postresuscitation interval, but none of the rats treated with the mask survived. TTO maintained its efficacy after increased duration of chest compression. TTO was as effective as conventional positive-pressure ventilation with 100% O(2) for securing oxygenation, resuscitation, and short-term survival and more effective than O(2) delivered through a mask.

Worsening respiratory failure in the newborn: considerations and therapeutic options

Worsening of respiratory failure of the newborn is a common situation in neonatal intensive care units. Any textbook on neonatology has chapters on this topic, but there is still a surprising lack of general accepted guidelines for what to do in that situation. Although such guidelines will depend on local traditions and strategies for initial treatment, as well as the degree of centralization of the treatment of the sick newborn. This article will provide suggestions for some basic considerations to be modified for each unit. It will also focus on the important topic of how to avoid iatrogenic injury by overly aggressive treatment. Guidelines for patients treated with nasal continous positive airway pressure and patients intubated and put on any kind of conventional positive pressure ventilation are described. Guidelines for high-frequency oscillatory ventilation, negative pressure ventilation, extracorporal membrane oxygenation and more experimental approaches, such as liquid ventilation, are not part of this article. Additive treatments like surfactant, nitric oxide and prostacyclin are only mentioned briefly.

High frequency jet ventilation and gas trapping

We have compared three types of high frequency jet ventilation (HFJV) with conventional positive pressure ventilation in patients recovering from elective coronary artery bypass surgery. Twelve patients were allocated randomly to receive HFJV at ventilatory frequencies of 60, 100, 150 and 200 bpm from a standard jet ventilator at either the proximal or distal airway (HFJV.p and HFJV.d), or from a valveless high frequency jet ventilator acting as a pneumatic piston (VPP). Trapped gas volume (Vtr), cardiac index (CI) and right ventricular ejection fraction (RVEF) were measured. Vtr was related to the type of HFJV used (P < 0.05) and ventilatory frequency (P < 0.05). CI decreased with increasing rate of HFJV (P < 0.05) and there were significant differences between the three types of HFJV (P < 0.05). RVEF showed a linear relationship with ventilatory frequency (P < 0.05) decreasing most with the VPP. The decrease in RVEF was associated with an increase in right ventricular end-systolic volume (P < 0.05) suggesting that an increase in right ventricular afterload was the cause. The same three types of HFJV were compared using a lung model with variable values of compliance and resistance, to assess the impact of lung mechanics on gas trapping (Vtr, ml). Lung model compliance (C) was set at 50 or 25 ml cm H2O-1 and resistance (R) at 5 or 20 cm H2O litre-1 s, where values of 50 and 5, respectively, are normal. Vtr increased with ventilatory frequency for all types of jet ventilation (P < 0.05), varying with the type of jet ventilation used (P < 0.05).