Ventilation in Pediatric ALI / ARDS

We know that the reduction of tidal volume during mechanical ventilation in adults with acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) affects outcome.1 Although, the optimal tidal volume, airway pressures and ventilator modalities are still controversial, it is clear that 12 ml/kg tidal volume increases mortality in ALI and ARDS patients compared to 6 ml/kg tidal volume.

The optimal management of ALI and ARDS in children is even less clear. The incidence of ALI and ARDS is less in pediatrics and the associated mortality is 22% to 27%. There is a lack of primary data in children and most ALI and ARDS management is extrapolated from adult studies. Children are not merely small adults, recent laboratory studies suggest than infants2 and neonates3 are less susceptible to high tidal volume injury. We know that in adults, very low tidal volume ventilation increases the tendency to develop atelectasis and infants and children there might be a greater risk for atelectasis because of their lower FRC and more compliant chest wall. So it becomes important to verify the appropriateness of applying adult ventilator strategies in pediatric populations.

Albuali et al.4 from London Ontario, performed a retrospective study comparing ventilatory strategies of patients from 1988-1992, when protective lung strategies were less likely to be used, and from 2000-2004, when protective strategies were more likely to be used in ALI patients. The primary outcome of the study was mortality and the secondary outcome was ventilator free days. Ideally they would have preformed a prospective randomized controlled trial comparing ventilator strategies but could not because of the ethics of studying a ventilator strategy that has been found to be harmful in adults.

This retrospective study included 164 children with ALI, 79 children from 1988-1992 and 85 children from 2000-2004. In the recent group (2000-2004) 53% of the patients received a mean tidal volume of < 8 ml/kg actual body weight (ABW) and 23.5% of patients received < 7 ml/kg ABW. Patients in the past group (1988-1992) only 5.6% received a tidal volume of < 8ml/kg ABW and 1.4% received a tidal volume < 7 ml/kg ABW.

The mortality rate in the recent group was significantly lower than in the past group, 21% for the recent group vs. 35% for the past group. Despite the fact that the recent group had a lower mortality rate, they had a significantly higher oxygenation index (OI) and lower baseline PaO2/FiO2 than the past group of children. There were also more ventilator free days in the recent group compared with the past group. When further analysis of the data was performed it was found that PRISM III scores (Pediatric Risk of Mortality score), immunodeficiency, and tidal volume were all independently associated with increased mortality.

There were two main findings in this study:
1.    the approach to ventilation in children with ALI was changed over the past 15 years and has followed adult recommendations
2.    mortality decreased by 40% in this population over those years and that a higher tidal volume was associated with increased mortality and a decreased number of ventilator free days

For a number of years we know that tidal volume reduction in adults with ARDS decreases mortality but a definitive study has not been done on children. Some times clinical findings in adults are accepted for use in children without further study in children. While it would be wonderful to do a prospective randomized controlled trial it is not always possible. Albuali and his group4 from London, Ontario and their 15 year retrospective study on ventilation in children with ALI found that decreasing tidal volume was the only therapeutic intervention found to be associated with mortality. While more work needs to be done studying ALI interventions in children, this helps us to know that we are heading in the right direction when adopting certain adult recommendations for children.
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1. ARDSnet. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. The Acute Respiratory Distress Syndrome Network. N Engl J Med 2000;342(18):1301-8.
2. Kornecki A, Tsuchida S, Ondiveeran HK, et al. Lung development and susceptibility to ventilator-induced lung injury. Am J Respir Crit Care Med 2005;171(7):743-52.
3. Copland IB, Martinez F, Kavanagh BP, et al. High tidal volume ventilation causes different inflammatory responses in newborn versus adult lung. Am J Respir Crit Care Med 2004;169(6):739-48.
4. Albuali WH, Singh RN, Fraser DD, et al. Have changes in ventilation practice improved outcome in children with acute lung injury? Pediatric critical care medicine 2007;8(4):324-30.

Asthma and the Use of Household Cleaning Sprays

There has been accumulating evidence that cleaning workers are at an increased risk for asthma and that specific professional cleaning products such as bleach and sprays are associated with asthma. Many professional cleaning products are also used in private households. Recently a European based epidemiological study was published that investigated the risk of new-onset asthma in relation to the use of common household cleaners. (1)

Twenty-two centers from 10 European countries followed-up around 3500 participants that took part in this investigation.The length of the follow-up averaged 9 years. Of the study participants, two-thirds that were doing the cleaning and/or washing were women (ranging from 57 to 87% across the countries) and only 9% of the participants were full-time homemakers. Cleaning products investigated include:

  • Washing powders
  • Liquid multiuse cleaning products
  • Polishes, waxes
  • Bleach
  • Ammonia
  • Decalcifiers, acids
  • Solvents, stain removers
  • Furniture sprays
  • Glass-cleaning sprays
  • Sprays for carpets, rugs, curtains
  • Sprays for mopping the floor
  • Oven sprays
  • Ironing sprays
  • Air-refreshing sprays

A positive association with asthma was observed for cleaning sprays in general; particularly furniture, glass-cleaning and air-refreshing sprays. The use of any product in spray form and its association with asthma was then studied in further detail. The risk of using cleaning sprays at least weekly was evaluated after patients were stratified for sex, smoking and atopy. The association between spray use and asthma was similar across all groups. When the use of sprays was classified according to the frequency of use and according to the number of different types used at least weekly, a dose related response was found. When the investigators adjusted for occupational exposures to asthmagens or for socioeconomic status it did not alter the findings.

This epidemiological study, the first to look at adult asthma and the possible relationship to non-occupational use of common household products, found an association of the use of products in spray form and the incidence of asthma.

Sprays and conventional liquid cleaning products contain similar active compounds such as alcohols, ammonia, chlorine-releasing agents, glycols, acryl polmers and terpenes. The use of sprays most likely enhances the respiratory exposure to these products and probably explains why an association wasn’t found with liquid products and asthma. The association with asthma and liquid products may need to be investigate further because there are many factors, including dilution, surface to which they are used and ambient temperature that may affect inhalatory exposure.

The mechanism for asthma and its association with the use of cleaning sprays is at least partially irritant induced. From occupational settings we know that asthma can follow a one-time high-level irritant exposure, but it is also becoming acceptable that low-level exposures to respiratory irritants can a cause asthma as well. This would explain how repeated household exposures to cleaning sprays are associated with asthma.

The authors of this investigation point out the possible significance of this study.

“Findings of our study may have significant implications for public health. Relative risks of 1.3 to 1.5 in combination with an overall proportion of 42% of weekly spray users suggest a population attributable fraction of about 15%. In other words, one in seven adult asthma cases could be attributed to common spray use”

The frequent use of household cleaning sprays may be a significant risk factor for adult asthma. More studies will need to be done to confirm this and hopefully the will also focus on the chemical compositions and the mechanisms that are the cause of this risk factor.

Over the past few years I have in my household been switching to as many organic or natural cleaning products as I can. I have done this with mostly ecological concerns in mind but we must really start to think about all the chemicals around is at home, work and even in outside that we spray and apply everywhere.

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1.    Zock J, Plana E, Jarvis D, et al. The Use of Household Cleaning Sprays and Adult Asthma: An International Longitudinal Study. Am J Respir Crit Care Med 2007;176:735-40.

Ventilation with Face Mask and Bag-Valve Device Video

The New England Journal of Medicine in their Videos in Clinical Medicine section have released a video that covers performing positive pressure ventilation with bag-valve and face mask.

This video demonstrates how to perform orotracheal intubation. Specific indications are discussed, along with contraindications, troubleshooting, and complications.

Specific topics covered in the video include:

  • Overview
  • Indications
  • Contraindications
  • Equipment
  • Procedure
  • Complications

The video can be viewed and downloaded at the NEJM. The video also has a PDF summary to accompany it.

Some previous Videos in Clinical Medicine include endotracheal intubation, arterial line insertion, nasogastric tube insertion, lumbar puncture and thoracentesis.

These are great learning/teaching tools and I definitely recommend checking them out.

SpO2/FiO2 ratio vs PaO2/FiO2 ratio in ALI/ARDS patients

A PaO2/FiO2 ratio of ≤ 300 and ≤ 200 are used in the diagnosis of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) for patients in acute hypoxic respiratory failure. The requirement for arterial blood gas analysis for diagnosis of ALI/ARDS and concerns about anemia, excessive blood draws may contribute to the underdiagnosis of ALI and ARDS.

We know that in healthy subjects PaO2 correlates well with SpO2 in the range of 80 to 100%. Could a SpO2/FiO2 ratio be used to noninvasively diagnose ALI/ARDS? Rice et al. with the NIH ARDS network recently looked into using the SpO2/FiO2 ratio as a surrogate for the PaO2/FiO2 ratio in the screening for ALI/ARDS patients.

This group looked at corresponding SpO2 and PaO2 from patients that were involved in the ARDSnet 6 ml/kg vs 12 ml/kg tidal volume trial. The relationship of SpO2/FiO2 ratio vs PaO2/FiO2 ratio was then validated using similar data from patients that were enrolled in the ARDSnet ALVEOLI (lower PEEP vs higher PEEP) study. They ended up having 2673 datapoints from the ARDSnet low tidal volume trial and 2031 datapoints from the ARDSnet PEEP trial. Measurements with SpO2 values >97% were excluded from the data set because the oxyhemoglobin dissociation curve is flat above 97%.

SpO2/FiO2 and PaO2/FiO2 ratios showed a linear relationship that did not change over varying levels of FiO2 or PEEP. A SpO2/FiO2 ratio of 235 correlated with a PaO2/FiO2 ratio of 200 and a SpO2/FiO2 ratio of 315 correlated with a PaO2/FiO2 ratio of 300. The SpO2/FiO2 ratio showed excellent sensitivity and good specificity in prediction the corresponding PaO2/FiO2 ratio in the validation data set. This study shows that the SpO2/FiO2 ratios of 235 and 315 are appropriate surrogates for the PaO2/FiO2 ratios of 200 and 300.

The use of a SpO2/FiO2 ratio will allow earlier recognition of patients who likely have ALI/ARDS without yet having undergone arterial blood gas analysis. This may facilitate earlier diagnosis, earlier treatment and early enrollment into clinical trials. Further studies will still need to be done to fully validate the SpO2/FiO2 and PaO2/FiO2 ratio relationship in populations of critically ill patients other than those with ALI/ARDS.

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Rice TW, Wheeler AP, Bernard GR, Hayden DL et al. Comparison of the SpO2/FiO2 ratio and the PaO2/FiO2 ratio in Patients With Acute Lung Injury or ARDS. Chest 2007; 132:410-417.

Endotracheal Intubation Video

The New England Journal of Medicine in their Videos in Clinical Medicine section have released a video that covers performing endotracheal intubation.

This video demonstrates how to perform orotracheal intubation. Specific indications are discussed, along with contraindications, troubleshooting, and complications.

Specific topics covered in the video include:

  • Overview
  • Indications
  • Contraindications
  • Equipment
  • Preparation
  • Orotracheal Intubation
  • Confirmation
  • Securing the Tube
  • Complications

 The video can be viewed and downloaded at the NEJM. The video also has a PDF summary to accompany it.

Some previous Videos in Clinical Medicine include arterial line insertion, nasogastric tube insertion, lumbar puncture and thoracentesis.

These are great learning/teaching tools and I definately reccomend checking them out.

Oxygen Saturation in Neonates

Worldwide somewhere between 5% and 10% of all newborns require some form of resuscitation. There continues to be questions about how much oxygen should be used during neonatal resuscitation. Despite over 50 years experience of oxygen therapy in neonates, the use of oxygen in neonates, especially premature neonates is not well understood. We still don’t fully understand the effects oxygen or saturation levels on retinopathy of prematurity, growth, brain, lung and other organs in respect to gestational age, time or onset and duration of specific oxygen or saturation levels.

A meta-analysis by Davis, Tan, et al. (1) showed a reduction in mortality in neonates resuscitation was started with room air compared to 100% oxygen. Saugstad, Ramji, et al. (2) did a follow-up of survivors resuscitated with room air and 100% oxygen at 2 years of age and found no differences in neurological sequelae. We also know that oxygen supplementation can be harmful because O2 free radicals are involved in the pathogenesis of many neonatal diseases. Pulse oximetry has been advocated to be used to adjust O2 supplementation.

In the April 2007 issue of the Journal of Pediatrics, Mariani, Dik, Ezquer et al. (3) looked at the physiological changes in pre- and post-ductal SpO2 levels in healthy neonates during the first few minutes after birth. They studied 110 neonates with a gestational age > 37 weeks. As soon as possible after clamping of the neonate’s cord, oximetry sensors (with Masimo signal extraction technology) were placed on the right hand and on one foot to record the pre- and post-ductal saturation levels. Oxygen saturation levels were up to 15 minutes after birth or until the pre-ductal saturation was greater than 90%. The resident who attended each delivery was unaware of the SpO2 levels and the AAP/AHA Neonatal Resuscitation Program protocol was followed if needed.

Pre- and post-ductal O2 saturation both increased gradually after birth but the levels were significantly different during the first 15 minutes after birth. At 5 minutes of birth the median pre-ductal saturation level was 90% (84-94) and the median post-ductal saturation level was 82% (76-89). The mean time to achieve a pre-ductal SpO2 level of 90% was 5.5 minutes. None of the infants required admission to the neonatal intensive care unit.

Pre- and Post-ductal Spo2
[Figure. Pre- and post-ductal SpO2 levels during the first 15 minutes after birth (median) Post-ductal SpO2 levels were significantly lower than pre-ductal SpO2 levels at 3, 4, 5, 10, and 15 minutes.](3)

The significant difference in pre-ductal and post-ductal oxygen saturation levels during the first 15 minutes after birth is probably due to a high pulmonary artery pressure and right-to-left shunting through the ductus arterious.

As some physicians have suggested, monitoring of oxygen saturation by pulse oximetry may help in infants requiring resuscitation to avoid exposure to high oxygen concentrations by varying supplemental oxygen levels. This study helps gives some insight to what may be the desired range of oxygen saturation levels in newborn infants. More studies are still needed though to understand the physiologic adaptations of the newborn and the rational of the use of supplemental oxygen especially in the most vulnerable premature infants.

A number of NICUs in Canada will very soon be participating in the Canadian Oxygen Trial (Efficacy and safety of targeting lower arterial oxygen saturations to reduce oxygen toxicity and oxidative stress in very preterm infants: the Canadian Oxygen Trial); a multi-centre, double blind, randomized controlled trial to look at the different effects of two different oxygen saturations in extremely pre-term infants. This study plans to look at whether lowering oxygen levels to target a SpO2 of 85-89% compared with 91-95% in infants born at gestational ages of 23 to 28 weeks increases the probability of survival to a corrected age of 18 months without severe neurosensory disability. This study plans to include about 1200 patients in the next 2.5 years.

Hopefully in the near future we will continue to get a better understanding of this extremely important and urgent issue in our neonatal patients.

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(1) Davis PG, Tan A, O’Donnell CP, Schulze A. Resuscitation of newborn infants with 100% oxygen or air: a systematic review and meta-analysis. Lancet 2004;364:1329-33.

(2) Saugstad O, Ramji S, Irani S, El-Meneza S, et al. Resuscitation of newborn infants with 21% or 100% oxygen: follow-up at 18 to 24 months. Pediatrics 2003;112:296-300.

(3) Mariani G, Dik PB, Ezquer A, Aquirre A, et al. Pre-ductal and Post-ductal Oxygen Saturation in Healthy Term Neonates after Birth. J Pediatrics 2007 Apr;150(4):418-21.

The Last Day

In the latest issue (March 13, 2007) of the CMAJ (journal of the Canadian Medical Association) a pediatric intensive care nurse from Edmonton, Alberta writes about what it is like to be left with the family on the last day of their child’s life.

For those of us that work in critical care we know that sometimes the difficult decision to forgo life-sustaining treatment must be made and no one tends to have a big a role to play in end of life care as the nurses do. This is a nice article about nursing a child through the end of life care process.

You can read the article in its entirety here: http://www.cmaj.ca/cgi/content/full/176/6/817

Currently the Canadian ICU Collaborative is calling ICU Teams across Canada to take action in improving the quality of End of Life Care for critically ill patients. Check www.saferhealthcarenow.ca for more info.

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