Effects of Vanilla on Hypoxic Intermittent Events in Premature Infants
Phase: NA
Conditions: Premature Birth, Neonatal Hypoxic Conditions
Sponsor: Université de Sherbrooke

Effect of Vanilla on Hypoxic Intermittent Events in Premature Infants 
 
 
 
NCT02630147 
 
 
 
 
 
 
Protocol version 1.0 
April 13, 2015 

 
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1. OBJECTIVES AND HYPOTHESIS 
 
1.1. Main objective 
The main objective of the study is to assess whether exposure to vanilla odor 
decreases the number of intermittent hypoxia events in preterm infants born 
between 320 and 336 weeks and reaching near term-equivalent age. A hypoxic 
event is defined as a desaturation < 90% with a decrease in oxygen saturation 
(SpO2) ≥ 5% compared to preceding SpO2, for a duration ≥ 5 seconds (Rhein et al. 
2014). 
 
1.2. Secondary objectives 
Secondary objectives are to determine the effect of vanilla odor further by 
measuring the percentage of recording time spent with a SpO2 < 80%, the 
percentage of recording time spent with a SpO2 < 90%, the bradycardia index 
(number per hour), the percentage of recording time spent in periodic breathing, 
as well as the effect on heart and respiratory rate variability. In addition, we aim 
to gather preliminary results on the effect of vanilla odor on the states of alertness. 
 
1.3. Hypothesis 
We hypothesize that vanilla odor stimulates the cardiorespiratory centers, and 
especially decreases periodic breathing and arterial oxygenation oscillations in 
preterm infants at near-term-equivalent age. 
 
 
 

 
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2. METHODS 
 
2.1. Study design 
To fulfill our main objective, a randomized, controlled, unblinded, balanced cross-
over study will be performed. 
 
2.2. Study population and patient sample 
The study population will be preterm infants born between 320 and 336 weeks 
and hospitalized in the neonatal care unit at the University of Sherbrooke Hospital 
Center, with a postnatal age of 3 to 4 weeks, i.e., close to a term-equivalent age. 
 
2.2.1. Patient sample 
 
We will study a convenience sample. Preterm infants in the neonatal care unit 
will be included in chronological order of their birth. 
The sample size has been computed with the help of Mrs Marie-Pierre Lapointe-
Garant, biostatistician at the University of Sherbrooke Hospital Research Center 
using the nQuery software. Literature data suggest that an average of 4 periodic 
breathing epochs per hour is expected in the population under study (Martin et 
al, 2011). A sample of 17 patients is therefore necessary to detect a difference of 
33% between conditions, with a power of 80% and an a error of 0.05. 
Accordingly, we aim to include 30 preterm infants to get 20 technically valid 
recordings. If necessary, we will continue patient recruitment to reach 20 valid 
recordings. We believe that the latter can be obtained within a 2-year period. 
This number is based on data from the neonatal care unit at the University of 
Sherbrooke Hospital Center showing that 51 and 59 preterm infants were born 
between 320 and 336 weeks in 2012 and 2013 respectively.  
 
2.2.1.1. 
Inclusion criteria 
 
- Birth between 32 and 336 weeks of gestational age 
 
- Postnatal age between 3 and 4 weeks 
 
- Absence of any respiratory support or supplemental oxygen 
 
- Clinically stable for a minimum of 48 hours prior to inclusion 
 
- Obtention of parental consent. 
 
2.2.1.2. 
Exclusion criteria: 
- Any respiratory condition (e.g., pneumonia or bronchopulmonary dysplasia) 
other than apnea of prematurity 
 
- Intraventricular hemorrhage grade 3 or 4, or periventricular leukomalacia; 
 
- Chromosomal anomalies 
- Congenital malformation susceptible to lead to cardiorespiratory or 
neurological complications 

 
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- Parental refusal 
 
- Significant clinical deterioration during the study period. 
 
* Note that caffeine treatment is not an exclusion criterion. 
 
2.3. Measuring instruments 
Our polysomnography equipment will allow recording electrocardiographic 
activity (ECG), SpO2 (Masimo oximeter), and thoracic and abdominal respiratory 
movements (respiratory inductance plethysmography, Respitrace). Preliminary 
observations will be collected for electroencephalographic activity and eye 
movements (states of alertness). No invasive sensor will be used for the study. 
 
2.4. Vanilla odorization 
As reported in past studies by Marlier L et al (2005), and Edraki M et al (2013), we 
will use 2 mL of a 2% vanillin solution to odorize the infant environment. The 
vanilla solution will be spread on the infant’s bib, both on the shoulders and the 
superior part of the thorax. According to results from the two past studies cited 
above, a single application at the beginning of the study will be sufficient. 
Following recordings, we will retrospectively check in the infant’s medical record 
whether any unexpected event has occurred during and within 24 hours after the 
odorization period, to detect any side-effect potentially related to vanilla odor 
exposure.  
 
 
2.5. Conduct of the study 
2.5.1. Data collection 
Following patient recruitment, medical history taking, and physical examination, 
all included preterm infants will undergo two nocturnal continuous recordings of 
ECG, SpO2 and respiratory movements between 9:00 pm and 9:00 am. The two 
12-hour recordings will be performed at 48-hour interval—i.e., with a 24-hour 
wash-out period—, one in the control condition, and the other under vanilla odor 
exposure, in a random order and in a balanced fashion. 
2.5.2. Polysomnographic recordings 
In addition, two 3-hour polysomnographic recordings will be performed on the 
morning following the 12-hour recordings above in a convenience subsample of 
10 to 15 of the infants —depending on the availability of the research personnel—. 
These additional recordings will allow gathering preliminary results on the 
potential effect of vanilla odor on sleep-wakefulness cycles. 
 
2.6. Data analysis 
2.6.1. Variables 

 
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In agreement with our main research question, we will compute the 90% and 80% 
desaturation indices per hour from the two 12-hour nocturnal recordings. We will 
also compute the percentage of the recording time spent with SpO2 < 80%, the 
percentage of the recording time spent with SpO2 < 90%, the percentage of the 
recording time spent in periodic breathing and the bradycardia index per hour. 
Finally, a corollary study will be performed by a physiology doctoral student under 
the direction of Jean-Paul Praud to assess the effect of vanilla odor on heart and 
respiratory rate variability. This assessment will be performed on the 12-hour 
recordings and will not require any additional intervention on the preterm infants. 
 
2.6.2. Definitions 
• States of alertness: the usual electrophysiological and behavioral criteria will be 
used to recognize wakefulness, NREM and REM sleep (Anders et al, 1984; Grigg-
Damberger M et al, 2007). 
• Central apneas will be defined by the absence of both nasal airflow and respiratory 
movements for at least two respiratory cycles, if a desaturation ≥ 3% or an arousal 
is present, or for 20 seconds in the absence of desaturation or arousal (Nunez J et 
al, 2011; Henderson-Smart DJ et al, 1986). 
• Periodic breathing: an epoch of periodic breathing will be defined by the presence 
of at least three central apneas with a duration ≥ 3 seconds, with a maximum of 
20 seconds of normal respiration between two apneas (Brockmann PE et al, 2013). 
• Desaturation: a desaturation will be defined as a decrease in SpO2 below 90% and 
of at least 5% compared to the preceding SpO2, for a duration > 5 seconds (Rhein 
et al, 2014). 
• Bradycardia: a bradycardia will be defined as a decrease of at least 33% in heart 
rate for ≥ 5 seconds (Poets et al, 1993). 
 
2.7. Statistical analysis 
Statistical analysis of the results has been elaborated with Mrs Marie-Pierre 
Lapointe-Garant, biostatistician at the University of Sherbrooke Hospital Research 
Center. For each continuous quantitative variable, the normality of the 
distribution will be first confirmed with the Shapiro-Wilks test. Then, a mixed 
model will be designed with the SPSS software and used under close supervision 
of Mrs Lapointe-Garant. 
 

 
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