Judith Hough

Humidified high flow nasal cannulae: Current practice in Australasian nurseries, a survey

Aim:  Humidified High Flow Nasal Cannula (HHFNC) has been increasingly adopted as a new means of respiratory support throughout the world. However, evidence to support its safety and efficacy is limited. The aim of the present survey was to determine current practices regarding the usage of HHFNC by neonatologists in Australia and New Zealand.

Physiologic effect of high-flow nasal cannula in infants with bronchiolitis

Objective: To assess the effect of delivering high-flow nasal cannula flow on end-expiratory lung volume, continuous distending pressure, and regional ventilation distribution in infants less than 12 months old with bronchiolitis. Design: Prospective observational clinical study. Setting: Nineteen bed medical and surgical PICU. Patients: Thirteen infants with bronchiolitis on high-flow nasal therapy. Interventions: The study infants were measured on a flow rate applied at 2 and 8 L/min through the high-flow nasal cannula system. Measurements and Results: Ventilation distribution was measured with regional electrical impedance amplitudes and end-expiratory lung volume using electrical impedance tomography. Changes in continuous distending pressure were measured from the esophagus via the nasogastric tube. Physiological variables were also recorded. High-flow nasal cannula delivered at 8 L/min resulted in significant increases in global and anterior end-expiratory lung volume (p < 0.01) and improvements in the physiological variables of respiratory rate, SpO2, and FIO2 when compared with flows of 2 L/min. Conclusion: In infants with bronchiolitis, high-flow nasal cannula oxygen/air delivered at 8 L/min resulted in increases in end-expiratory lung volume and improved respiratory rate, FIO2, and SpO2.

Effect of body position on ventilation distribution in preterm infants on continuous positive airway pressure

Rationale: Although continuous positive airway pressure is used extensively in neonatal intensive care units, and despite the belief that positioning is considered vital to the maintenance of good lung ventilation, no data exist on regional ventilation distribution in infants on continuous positive airway pressure ventilatory support. Objectives: To investigate the effect of body position on regional ventilation in preterm infants on continuous positive airway pressure ventilatory support using electrical impedance tomography. Design: Randomized crossover study design. Setting: Neonatal intensive care unit. Patients: Twenty-four preterm infants on continuous positive airway pressure were compared to six spontaneously breathing preterm infants. Interventions: Random assignment of the order of the positions supine, prone, and quarter prone. Measurements and Results: Changes in global and regional lung volume were measured with electrical impedance tomography. Although there were no differences between positions, regional tidal volume was increased in the posterior compared with the anterior lung (p < .01) and in the right compared with the left lung (p < .03) in both the spontaneously breathing infants and in the infants on continuous positive airway pressure. The posterior lung filled earlier than the anterior lung in the spontaneously breathing infants (p < .02), whereas in the infants on continuous positive airway pressure the right lung filled before the left lung (p < .01). There was more ventilation inhomogeneity in the infants on continuous positive airway pressure than in the healthy infants (p < .01). Conclusions: This study presents the first results on regional ventilation distribution in preterm infants on continuous positive airway pressure using electrical impedance tomography. Gravity had little impact on regional ventilation distribution in preterm infants on continuous positive airway pressure or in spontaneously breathing infants in the supine or prone position, indicating that ventilation distribution in preterm infants is not gravity-dependent but follows an anatomical pattern. Australia New Zealand Clinical Trials Registry: ACTRN12606000210572.

Effect of body position on ventilation distribution in ventilated preterm infants

Rationale: Positioning is considered vital to the maintenance of good lung ventilation by optimizing oxygen transport and gas exchange in ventilated premature infants. Previous studies suggest that the prone position is advantageous; however, no data exist on regional ventilation distribution for this age group. Objectives: To investigate the effect of body position on regional ventilation distribution in ventilated and nonventilated preterm infants using electrical impedance tomography. Design: Randomized crossover study design. Setting: Neonatal ICU. Patients: A total of 24 ventilated preterm infants were compared with six spontaneously breathing preterm infants. Interventions: Random assignment of the order of the positions supine, prone, and quarter prone. Measurements and Main Results: Ventilation distribution was measured with regional impedance amplitudes and global inhomogeneity indices using electrical impedance tomography. In the spontaneously breathing infants, regional impedance amplitudes were increased in the posterior compared with the anterior lung (p < 0.01) and in the right compared with the left lung (p = 0.03). No differences were found in the ventilated infants. Ventilation was more inhomogeneous in the ventilated compared with the healthy infants (p < 0.01). Assessment of temporal regional lung filling showed that the posterior lung filled earlier than the anterior lung in the spontaneously breathing infants (p < 0.02) whereas in the in the ventilated infants the right lung filled before the left lung (p < 0.01). Conclusions: In contrast to previous studies showing that ventilation is distributed to the nondependent lung in infants and children, this study shows that gravity has little effect on regional ventilation distribution.

Measurement of ventilation and cardiac related impedance changes with electrical impedance tomography

IntroductionElectrical impedance tomography (EIT) has been shown to be able to distinguish both ventilation and perfusion. With adequate filtering the regional distributions of both ventilation and perfusion and their relationships could be analysed. Several methods of separation have been suggested previously, including breath holding, electrocardiograph (ECG) gating and frequency filtering. Many of these methods require interventions inappropriate in a clinical setting. This study therefore aims to extend a previously reported frequency filtering technique to a spontaneously breathing cohort and assess the regional distributions of ventilation and perfusion and their relationship.MethodsTen healthy adults were measured during a breath hold and while spontaneously breathing in supine, prone, left and right lateral positions. EIT data were analysed with and without filtering at the respiratory and heart rate. Profiles of ventilation, perfusion and ventilation/perfusion related impedance change were generated and regions of ventilation and pulmonary perfusion were identified and compared.ResultsAnalysis of the filtration technique demonstrated its ability to separate the ventilation and cardiac related impedance signals without negative impact. It was, therefore, deemed suitable for use in this spontaneously breathing cohort.Regional distributions of ventilation, perfusion and the combined ΔZV/ΔZQ were calculated along the gravity axis and anatomically in each position. Along the gravity axis, gravity dependence was seen only in the lateral positions in ventilation distribution, with the dependent lung being better ventilated regardless of position. This gravity dependence was not seen in perfusion.When looking anatomically, differences were only apparent in the lateral positions. The lateral position ventilation distributions showed a difference in the left lung, with the right lung maintaining a similar distribution in both lateral positions. This is likely caused by more pronounced anatomical changes in the left lung when changing positions.ConclusionsThe modified filtration technique was demonstrated to be effective in separating the ventilation and perfusion signals in spontaneously breathing subjects. Gravity dependence was seen only in ventilation distribution in the left lung in lateral positions, suggesting gravity based shifts in anatomical structures. Gravity dependence was not seen in any perfusion distributions.

The effectiveness of quarter turn from prone in maintaining respiratory function in premature infants

The aim of this study was to determine the effectiveness of quarter turn from prone compared with supine and prone positioning in maintaining respiratory function in premature infants managed in a neonatal intensive care unit.

Lung recruitment and endotracheal suction in ventilated preterm infants measured with electrical impedance tomography.

Although suctioning is a standard airway maintenance procedure, there are significant associated risks, such as loss of lung volume due to high negative suction pressures. This study aims to assess the extent and duration of change in end‐expiratory level (EEL) resulting from endotracheal tube (ETT) suction and to examine the relationship between EEL and regional lung ventilation in ventilated preterm infants with respiratory distress syndrome.

Diagnostic thoracic ultrasound within critical care

Within critical care, the evolving role of diagnostic thoracic ultrasound (DTU) challenges the conventional assessment methods of chest x-ray and auscultation. Diagnostic thoracic ultrasound can be used to image pleural, alveolar and interstitial pathologies, and diaphragmatic movement. Validity/Reliability: For DTU, using computed tomography as the comparator, the sensitivity and specificity for the detection of pleural effusion are 93% and 96%, as compared to 65% and 81% for

Effect of time and body position on ventilation in premature infants

Background:Infants with respiratory dysfunction undergo regular position changes to improve lung function however it is not known how often a position change should occur. This study measured changes in lung function occurring over time after repositioning in preterm infants.Methods:Changes in end-expiratory level (EEL) and ventilation distribution were measured 30 mins, 2 h, and 4 h after repositioning into either prone, quarter turn from prone, or supine using Electrical Impedance Tomography (EIT). Physiological measurements were also taken.Results:Sixty preterm infants were included in the study. Infants receiving respiratory support (mechanical ventilation or continuous positive airway pressure (CPAP)) had improved ventilation homogeneity after 2 h (P < 0.01), maintained at 4 h. Spontaneously breathing infants had improved homogeneity at 2 h (P < 0.01) and improved global EEL after 4 h (P < 0.01) whereas infants receiving CPAP demonstrated an improved global EEL at 2 h (P < 0.01).Conclusion:Regional ventilation distribution is influenced by time independent of changes due to body position. Differences exist between infants on ventilatory support compared with those who are spontaneously breathing. Infants receiving ventilatory support have a physiological peak in lung function after 2 h which remains above baseline at 4 h. A change in body position facilitates an improvement in lung function in infants on ventilatory support.

Lung recruitment and endotracheal suction in ventilated preterm infants measured with electrical impedance tomography: Lung recruitment & endotracheal suction

Although suctioning is a standard airway maintenance procedure, there are significant associated risks, such as loss of lung volume due to high negative suction pressures. This study aims to assess the extent and duration of change in end‐expiratory level (EEL) resulting from endotracheal tube (ETT) suction and to examine the relationship between EEL and regional lung ventilation in ventilated preterm infants with respiratory distress syndrome.