Videomicroscopy as a tool for investigation of the microcirculation in the newborn
2016; Wiley; Volume: 4; Issue: 19 Linguagem: Inglês
10.14814/phy2.12941
ISSN2051-817X
AutoresIan Wright, Joanna Latter, Rebecca M. Dyson, Christopher Levi, Vicki L. Clifton,
Tópico(s)Neuroscience of respiration and sleep
ResumoPhysiological ReportsVolume 4, Issue 19 e12941 Original ResearchOpen Access Videomicroscopy as a tool for investigation of the microcirculation in the newborn Ian M. R. Wright, Corresponding Author Ian M. R. Wright iwright@uow.edu.au Hunter Medical Research Institute, Newcastle, New South Wales, Australia Discipline of Paediatrics and Child Health, School of Medicine and Public Health, University of Newcastle, Newcastle, New South Wales, Australia Kaleidoscope Neonatal Intensive Care Unit, John Hunter Children's Hospital, Newcastle, New South Wales, Australia Graduate School of Medicine and Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, New South Wales, Australia Correspondence Ian M. R. Wright, Graduate School of Medicine and Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW 2522, Australia; and Level 8, The Wollongong Hospital, Crown Street, Wollongong, NSW 2500, Australia. Tel: +61 2 4221 4015; Fax: +61 2 4253 4838; E-mail: iwright@uow.edu.auSearch for more papers by this authorJoanna L. Latter, Joanna L. Latter Hunter Medical Research Institute, Newcastle, New South Wales, Australia Discipline of Paediatrics and Child Health, School of Medicine and Public Health, University of Newcastle, Newcastle, New South Wales, AustraliaSearch for more papers by this authorRebecca M. Dyson, Rebecca M. Dyson Hunter Medical Research Institute, Newcastle, New South Wales, Australia Discipline of Paediatrics and Child Health, School of Medicine and Public Health, University of Newcastle, Newcastle, New South Wales, Australia Graduate School of Medicine and Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, New South Wales, AustraliaSearch for more papers by this authorChris R. Levi, Chris R. Levi Hunter Medical Research Institute, Newcastle, New South Wales, AustraliaSearch for more papers by this authorVicki L. Clifton, Vicki L. Clifton Mater Medical Research Institute, University of Queensland, Brisbane, Queensland, AustraliaSearch for more papers by this author Ian M. R. Wright, Corresponding Author Ian M. R. Wright iwright@uow.edu.au Hunter Medical Research Institute, Newcastle, New South Wales, Australia Discipline of Paediatrics and Child Health, School of Medicine and Public Health, University of Newcastle, Newcastle, New South Wales, Australia Kaleidoscope Neonatal Intensive Care Unit, John Hunter Children's Hospital, Newcastle, New South Wales, Australia Graduate School of Medicine and Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, New South Wales, Australia Correspondence Ian M. R. Wright, Graduate School of Medicine and Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW 2522, Australia; and Level 8, The Wollongong Hospital, Crown Street, Wollongong, NSW 2500, Australia. Tel: +61 2 4221 4015; Fax: +61 2 4253 4838; E-mail: iwright@uow.edu.auSearch for more papers by this authorJoanna L. Latter, Joanna L. Latter Hunter Medical Research Institute, Newcastle, New South Wales, Australia Discipline of Paediatrics and Child Health, School of Medicine and Public Health, University of Newcastle, Newcastle, New South Wales, AustraliaSearch for more papers by this authorRebecca M. Dyson, Rebecca M. Dyson Hunter Medical Research Institute, Newcastle, New South Wales, Australia Discipline of Paediatrics and Child Health, School of Medicine and Public Health, University of Newcastle, Newcastle, New South Wales, Australia Graduate School of Medicine and Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, New South Wales, AustraliaSearch for more papers by this authorChris R. Levi, Chris R. Levi Hunter Medical Research Institute, Newcastle, New South Wales, AustraliaSearch for more papers by this authorVicki L. Clifton, Vicki L. Clifton Mater Medical Research Institute, University of Queensland, Brisbane, Queensland, AustraliaSearch for more papers by this author First published: 30 September 2016 https://doi.org/10.14814/phy2.12941Citations: 7 Funding Information This study was funded by project grants from the National Health and Medical Research Council (ID#569285) and the John Hunter Hospital Charitable Trust (both awarded to IMRW). AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Abstract The perinatal period remains a time of significant risk of death or disability. Increasing evidence suggests that this depends on microcirculatory behavior. Sidestream dark-field orthogonal polarized light videomicroscopy (OPS) has emerged as a useful assessment of adult microcirculation but the values derived are not delineated for the newborn. We aimed to define these parameters in well term newborn infants. Demographic details were collected prospectively on 42 healthy term neonates (n = 20 females, n = 22 males). OPS videomicroscopy (Microscan) was used to view ear conch skin microcirculation at 6, 24, and 72 h of age. Stored video was analyzed by a masked observer using proprietary software. There were no significant differences between the sexes for any structural parameters at any time point. There was a significant increase over time in small vessel perfusion in female infants only (P = 0.009). A number of 6- and 72-h measurements were significantly correlated, but differed from the 24-h values. These observations confirm the utility of the ear conch for neonatal microvascular videomicroscopy. They provide a baseline for studies into the use of OPS videomicroscopy in infants. The changes observed are comparable with previous studies of term infants using these and other microvascular techniques. It is recommended that studies for examining the mature neonatal microvascular structure be delayed until 72 h of life, but studies of the physiology of cardiovascular transition should include the 24-h time point after delivery. Introduction The perinatal period remains a time of significant risk of death or disability. In the developed world, it is the major contributor to infant mortality with 10% of infants likely to die when born too early (Parry et al. 2003). In the developing world, this is even more pronounced (Ngoc et al. 2006). In addition, illness around this time is associated with significant long-term morbidity with the associated increase in health care costs (Doyle 2004). Most infants who die become sick in the first 72 h of life and understanding this period of rapid cardiovascular transition is crucial to modifying outcomes. There is increasing evidence that the physiology and pathophysiology in this period is dependent on the behavior of the microcirculation. In preterm infants, increased microvascular flow at 24 h of age has been closely associated with poor outcomes including both death and illness severity (Wright et al. 2012). In addition, it is known that poor outcomes in the perinatal period are strongly associated with male sex (Kent et al. 2012); there is now increasing evidence that the dysregulation of the microcirculation, associated with poor outcomes, are more evident in male infants (Stark et al. 2008b; Dyson et al. 2014a). The majority of recent studies in newborn microcirculation have utilized laser Doppler flowmetry as a noninvasive tool, suitable for use in the human newborn. This technique, however, provides no information of the circulatory structure underlying the observations of microvascular function. While it is highly likely that the described differences are due to functional changes, they may also be due to significant structural changes related to angiogenesis, apoptosis (Pladys et al. 2005; Duval et al. 2007), or differential perfusion of different components of the microcirculation. A potential way of clarifying some of these structural questions is direct noninvasive visualization of the microcirculation in vivo using sidestream dark-field orthogonal polarized light videomicroscopy (OPS). OPS has emerged as a potentially useful tool for assessment of the microcirculation in adults (Vincent and De Backer 2013; Abdo et al. 2014; Donndorf et al. 2014), but the parameters derived have not been fully delineated for the newborn age group. The aim of this study was to provide OPS data for all parameters obtained using a commonly used analysis package (AVA v3.0; MicroVision Medical, Amsterdam, The Netherlands) in the healthy term newborn infant. In order to understand the physiology and pathophysiology of the microcirculation in the perinatal period in sicker term infant, or in the preterm infant, it is first necessary to define these values in this well control population. In view of previous study findings using laser Doppler, a priori analyses of the effects of postnatal age and of sex were undertaken. Materials and Methods Expectant mothers were recruited into the "Cardiovascular Adaptation of the Newborn Study 2 (2CANS)" after informed consent following presentation to the antenatal clinic of the John Hunter Hospital, Newcastle, Australia and included if their pregnancy proceeded to term. This study was a planned substudy of a larger study, stratified by gestational age at delivery (very preterm: ≤28 weeks, preterm 29–36 weeks, term ≥37 weeks), based on the protocol of our previous study (CANS1) (Stark et al. 2008a,b). A diagnosis of hypoxic ischemic encephalopathy, congenital malformations, chromosomal disorders, or known congenital infection excluded admission to this study. All study protocols were approved by the ethics committees at the John Hunter Hospital (Hunter New England Local Health District) and the University of Newcastle. Demographic data were obtained prospectively from the medical record of mother or baby as required, both for baseline data and status at each of the time points. The infants were examined at 6 (±1), 24 (±2), and 72 (±6) h of age. The study time points were based upon our previous observations, in term and preterm infants, of microcirculatory flow changes using laser Doppler flowmetry (Stark et al. 2008a,b; Dyson et al. 2014a). Study timing also depended upon the availability of the infant, operator, and equipment. The sidestream dark-field orthogonal polarized light videomicroscope camera (Microscan; MicroVision Medical) was used to acquire images. This methodology is described in full elsewhere (De Backer et al. 2007; Trzeciak et al. 2007) but, in brief, a polarized light shone from the end of the instrument into the tissues, above which it was held, barely in contact with a thin surface film of white soft paraffin. The standard single use 5× disposable lens was used (MicroVision Medical). The image was taken on the ear conch, using the nondependent ear. Previous studies have used a variety of body sites for OPS recording, but we chose the ear conch for a number of reasons: it is derived from the same carotid circulation as the widely reported, and clinically significant, sublingual circulation used in adult studies (Vincent and De Backer 2009, 2013); it is physically easy to undertake the study (resting the hand lightly on the side of the infants head or the bed adjacent to the head); it does not involve unwrapping the infant, which is important for thermoregulatory stability and facilitates the infant settling; finally, it only requires one operator, as there is no requirement to hold the arm out of the way (Schwepcke et al. 2013) nor adjust for breathing movement. Others have recently compared this site to previous neonatal methodologies (Alba-Alejandre et al. 2013). Polarized light traveled into the tissue where it underwent decoherence. The reflected decoherent light passed through the receiving polarized filter to the CCD of the video camera to give, in effect, a deep light source behind the vessels of the microvasculature. The wavelength of light used was 530 nm (green) and so the blood columns within the vessels appeared black (Fig. 1). The image resolution of the system is 720 × 480 pixels with 1.45 μm/pixel spatial resolution, a field of view of 1044 × 758 μm, and 30 frames per second temporal resolution. A duration of 10 sec of recording was attempted for each occasion and this was repeated for a total of three to five recordings, as able. Following analog to digital conversion, the pictures were stored until data analysis was undertaken using proprietary software (AVA) and according to published consensus approaches for this technique (De Backer et al. 2007; Bezemer et al. 2011; Lehmann et al. 2014). An observer, masked to the clinical details, adjusted the image quality for maximum clarity, as per AVA software instructions. Hundred (±30) images were stacked for the structural assessments. Images of poor quality were rejected from further analysis. Semiautomated vessel identification, delineation, and flow attribution were undertaken and then specific flow velocities were established for each vessel type (small: 1–25 μm, medium: 25–50 μm, and large 50–100 μm, predefined defaults within AVA) using time velocity diagrams with 3–6 white cell tracks within the red cell column averaged for each vessel velocity. Between 1 and 5, recordings (median 3) were made for each session on each infant and these were then averaged to give the final values used for each infant at each time point, for use in subsequent statistical analyses. Figure 1Open in figure viewerPowerPoint Stacked frames (n = 100) from a single video of OPS videomicroscopy from ear conch of a term female infant on day 1 of life. Statistical analysis was performed for all infants and also for male and female infants separately, as decided a priori. Data were analyzed using SPSS Statistics v20 (IBM Corp., New York, NY). Most data were normally distributed, but if the group numbers were low, appropriate nonparametric testing was used to confirm significance. In view of the known sex differences in microcirculation previously reported (Stark et al. 2008b), correlations were undertaken using partial correlation testing with adjustment for infant sex. For ease of reporting the parameter values described for these well term infants are reported by grouping parameters into separate tables as follows. Structural (quantitative) indices Detected vessel length, vessel density, vessel surface area percentage, De Backer score, small vessel length, small vessel length percentage, small vessel perfused length, small vessel perfused length percentage, medium vessel length, medium vessel length percentage, medium vessel perfused length, medium vessel perfused length percentage, large vessel length, large vessel length percentage, large vessel perfused length, large vessel perfused length percentage. Functional indices (semiquantitative) Sluggish flow small vessels, continuous flow small vessels, sluggish flow medium vessels, continuous flow medium vessels, sluggish flow large vessels, continuous flow large vessels, small vessel total vessel density (TVD), small vessel perfused vessel density (PVD), small vessel proportion perfused vessels (PPV), small vessel microvascular flow index (MFI), other vessel TVD, other vessel PVD, other vessel PPV, other vessel MFI, all vessel TVD, all vessel PVD, all vessel PPV, all vessel MFI. Velocity/flow indices (quantitative) Small vessel average velocity, medium vessel average velocity, large vessel average velocity, all vessel average velocity, small vessel average flow, medium vessel average flow, large vessel average flow, all vessel average flow. Unless otherwise stated, values are for a stacked field of view obtained within the program (AVA), as in Figure 1. All tabled results are to two significant figures unless otherwise stated. Results Forty-two term singleton babies were recruited to this study (Table 1). All were normothermic; one female infant was managed briefly on the neonatal unit with continuous positive airway pressure with an eventual diagnosis of transient tachypnea of the newborn. No baby required resuscitation, with mean Apgar scores of 9 at 1 min (range: 6–9), 9 at 5 min (range: 9–10), and 10 at 10 min (range: 9–10). Four (9.5%) infants were small for gestational age (SGA, <10th centile) but none 24 h), one mother of a female infant received nifedipine, and four received beta-blockers. There were 22 (52%) male infants, 9.1% SGA; n = 10 delivered by cesarean section, n = 4 by assisted vaginal delivery, and n = 8 by normal vaginal delivery. Apgar scores were 9 at 1 min (range: 6–9), 9 at 5 min (range: 9–10), and 9 at 10 min (range: 9–10). Four mothers of male infants had gestational hypertension (very mild) and one a renal condition (recurrent urinary tract infections; normal renal scan and function). Two mothers of male infants had prolonged rupture of membranes (>24 h), one of which received a course of steroids greater than 1 week prior to delivery. No male infants were exposed to nifedipine perinatally, but two mothers did receive treatment with beta-blockers. Due to investigator, equipment, and infant availability, not all infants were seen at all three time points. Where a scan was attempted, pictures were recorded in 96% of occasions. The percentage of successful image acquisition was 98% at 6 h, 94% at 24 h, and 87% at 72 h. The rate of high-quality images suitable for analysis from these was thus 88%, with others rejected for a variety of reasons (sequence too short, image clarity, or evidence of pressure effects; Trzeciak et al. 2007). Overall, there were 37 at 6 h, 39 at 24 h, and 18 at 72 h after quality control measures. Five infants had one recording, 22 infants two recordings, and 15 infants had recordings at all three time points. While most parameters were normally distributed over the larger group, we have reported both means and medians to give results that will allow comparisons with future studies. These are displayed in functional parameter groups, as described above, and by age of life in Tables 2-4. For all individual parameters and all time points, there were no differences between the sexes and so these have been amalgamated to produce these tables of OPS videomicroscopy values in well newborn infants. Table 2. Videomicroscopy measures at 6 h of age in the term newborn: (a) structural; (B) functional and (C) velocity/flow Videomicroscopy parameter Mean SD Lower 95% Upper 95% Median 25th Quartile 75th Quartile (A) Structural Detected vessel length (mm) 7.0 1.2 4.8 9.1 6.9 6.1 7.6 Vessel density (mm/mm2) 18 3.1 13 24 18 16 20 Vessel surface area percentage 29 3.5 22 34 29 26 31 De Backer score (1/mm) 12 2.6 8.3 17 12 11 13 Small vessel length (mm) 5.8 1.3 3.1 8.1 5.8 5.0 6.4 Small vessel length percentage 82 7.1 70 93 82 79 88 Small vessel perfused length (mm) 5.8 1.4 3.1 8.1 5.8 5.0 6.4 Small vessel perfused length percentage 82 7.6 69 93 81 79 89 Medium vessel length (mm) 1.1 0.35 0.52 1.8 1.1 0.94 1.4 Medium vessel length percentage 17 5.9 7.0 27 17 12 20 Medium vessel perfused length (mm) 1.1 0.36 0.52 1.8 1.1 0.87 1.5 Medium vessel perfused length percentage 17 6.2 7.0 27 18 11 21 Large vessel length (mm) 0.11 0.17 0.01 0.22 0.05 0.02 0.15 Large vessel length percentage 1.8 3.4 0.05 3.8 0.59 0.19 2.2 Large vessel perfused length (mm) 0.13 0.19 0.01 0.56 0.05 0.017 0.15 Large vessel perfused length percentage 2.1 3.7 0.06 9.4 0.59 0.21 2.2 (B) Functional Small vessels sluggish flow (%) 3.6 5.2 0.0 16 1.1 0.0 5.2 Small vessels continuous flow (%) 74 20 0.0 92 78 71 84 Medium vessels sluggish flow (%) 0.24 0.90 0.0 3.2 0.0 0.0 0.0 Medium vessels continuous flow (%) 16 7.2 0.0 29 16 10 20 Large vessels sluggish flow (%) a a a a a a a Large vessels continuous flow (%) 1.2 3.1 0.0 9.9 0.01 0.0 0.93 Small vessels TVD (mm/mm2) 15 3.6 8.5 22 15 13 18 Small vessels PVD (mm/mm2) 15 3.7 8.5 22 15 13 18 Small vessels PPV (%) 82 7.8 69 93 82 78 89 Small vessels MFI 2.9 0.14 2.6 3.0 3.0 3.0 3.0 Other vessels TVD (mm/mm2) 3.1 0.93 1.5 4.8 3.1 2.4 3.8 Other vessels PVD (mm/mm2) 3.2 1.0 1.5 4.8 3.2 2.3 3.9 Other vessels PPV (%) 18 7.8 6.6 31 18 11 22 Other vessels MFI 3.0 0.12 2.6 3.0 3.0 3.0 3.0 All vessels TVD (mm/mm2) 18 3.1 13 24 18 16 20 All vessels PVD (mm/mm2) 18 3.1 13 24 18 16 20 All vessels PPV (%) 100 0 100 100 100 100 100 All vessels MFI 3.0 0.13 2.6 3.0 3.0 3.0 3.0 (C) Velocity/flow Small vessel average velocity (μm/sec) 390 135 170 730 380 310 440 Medium vessel average velocity (μm/sec) 400 160 190 680 390 290 530 Large vessel average velocity (μm/sec) a a a a a a a All vessel average velocity (μm/sec) 404 135 238 727 389 328 465 Small vessel average flow (μL/sec) 79 000 36 000 31 000 131 000 75 000 52 000 98 000 Medium vessel average flow (μL/sec) 34 0000 190 000 120 000 690 000 290 000 220 000 420 000 Large vessel average flow (μL/sec) a a a a a a a All vessel average flow (μL/sec) 150 000 98 000 39 000 390 000 110 000 76 000 190 000 a Unable to calculate due to small numbers. Table 3. Videomicroscopy measures at 24 h of age in the term newborn: (A) structural; (B) functional; and (C) velocity/flow Videomicroscopy parameter Mean SD Lower 95% Upper 95% Median 25th Quartile 75th Quartile (A) Structural Detected vessel length (mm) 6.9 1.1 5.0 8.7 6.9 6.0 7.7 Vessel density (mm/mm2) 18 3 13 22 18 15 20 Vessel surface area percentage 29 4 22 36 29 26 31 De Backer score (1/mm) 12 2.5 7.3 16 12 10 14 Small vessel length (mm) 5.6 1.3 3.2 8.0 5.5 4.7 6.6 Small vessel length percentage 81 9 63 92 83 75 89 Small vessel perfused length (mm) 5.8 1.2 4.0 8.0 5.6 4.9 6.6 Small vessel perfused length percentage 82 8 66 92 82 75 89 Medium vessel length (mm) 1.1 0.5 0.4 2.1 1.0 0.8 1.4 Medium vessel length percentage 17 8 6 34 15 11 22 Medium vessel perfused length (mm) 1.1 0.5 0.4 1.9 1.0 0.8 1.4 Medium vessel perfused length percentage 16 8 5 28 14 10 21 Large vessel length (mm) 0.23 0.32 0.01 0.82 0.09 0.02 0.33 Large vessel length percentage 3.5 5.8 0.1 16 1.1 0.2 4.0 Large vessel perfused length (mm) 0.28 0.38 0.01 1.3 0.06 0.02 0.40 Large vessel perfused length percentage 4.2 6.9 0 24 0.6 0.2 4.7 (B) Functional Small vessels sluggish flow (%) 2.9 4.6 0.0 14 0.0 0.0 4.2 Small vessels continuous flow (%) 79 9.5 62 93 77 73 88 Medium vessels sluggish flow (%) 0.6 1.5 0.0 4.3 0.0 0.0 0.0 Medium vessels continuous flow (%) 15 8.1 4.2 27 13 9.1 23 Large vessels sluggish flow (%) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Large vessels continuous flow (%) 2.3 5.5 0.0 16 0.0 0.0 0.7 Small vessels TVD (mm/mm2) 15 3.4 7.9 20 15 12 18 Small vessels PVD (mm/mm2) 15 3.3 9.8 20 15 13 18 Small vessels PPV (%) 82 8.6 66 93 83 75 90 Small vessels MFI 2.9 0.1 2.8 3.0 3.0 3.0 3.0 Other vessels TVD (mm/mm2) 3.2 1.1 1.5 5.1 3.3 2.2 4.0 Other vessels PVD (mm/mm2) 3.1 1.2 1.5 4.8 3.1 2.3 3.9 Other vessels PPV (%) 18 8.7 6.6 34 17 10 25 Other vessels MFI 3.0 0.1 2.7 3.0 3.0 3.0 3.0 All vessels TVD (mm/mm2) 18 2.8 13 22 19 16 20 All vessels PVD (mm/mm2) 18 2.5 13 22 19 16 20 All vessels PPV (%) 100 0.2 100 100 100 100 100 All vessels MFI 3.0 0.1 2.8 3.0 3.0 3.0 3.0 (C) Velocity/flow Small vessel average velocity (μm/sec) 430 110 270 640 400 370 490 Medium vessel average velocity (μm/sec) 420 140 190 740 420 340 510 Large vessel average velocity (μm/sec) a a a a a a a All vessel average velocity (μm/sec) 440 110 260 640 430 370 510 Small vessel average flow (μL/sec) 79 000 29 000 35 000 130 000 83 000 56 000 98 000 Medium vessel average flow (μL/sec) 340 000 160 000 130 000 770 000 340 000 210 000 400 000 Large vessel average flow (μL/sec) a a a a a a a All vessel average flow (μL/sec) 130 000 94 000 43 000 290 000 100 000 73 000 170 000 a Unable to calculate due to small numbers. Table 4. Videomicroscopy measures at 72 h of age in the term newborn: (A) structural; (B) functional; and (C) velocity/flow Videomicroscopy parameter Mean SD Lower 95% Upper 95% Median 25th Quartile 75th Quartile (A) Structural Detected vessel length (mm) 7.2 1.3 4.2 8.6 7.6 6.9 8.1 Vessel density (mm/mm2) 18 3.2 10 22 19 17 21 Vessel surface area percentage 29 3.0 25 34 29 26 32 De Backer score (1/mm) 12 2.1 5.9 16 13 11 14 Small vessel length (mm) 5.9 1.4 2.6 7.8 5.7 5.5 6.9 Small vessel length percentage 81 7.5 62 92 80 76 86 Small vessel perfused length (mm) 6.3 1.1 4.2 7.8 6.6 5.5 7.2 Small vessel perfused length percentage 83 6.3 74 92 82 78 89 Medium vessel length (mm) 1.2 0.39 0.67 1.8 1.2 0.91 1.6 Medium vessel length percentage 18 7.3 8.4 36 18 11 23 Medium vessel perfused length (mm) 1.2 0.40 0.67 1.8 1.1 0.88 1.6 Medium vessel perfused length percentage 16 5.9 8.4 24 16 11 22 Large vessel length (mm) 0.094 0.11 0.01 0.39 0.065 0.01 0.11 Large vessel length percentage 1.4 1.6 0.07 4.9 1.0 0.15 1.6 Large vessel perfused length (mm) 0.11 0.12 0.01 0.39 0.09 0.01 0.13 Large vessel perfused length percentage 1.5 1.8 0.07 4.9 1.2 0.15 1.9 (B) Functional Small vessels sluggish flow (%) 2.5 3.8 0.0 11 1.1 0.0 2.4 Small vessels continuous flow (%) 80 5.3 72 90 80 77 84 Medium vessels sluggish flow (%) 0.3 1.1 0.0 4.0 0.0 0.0 0.0 Medium vessels continuous flow (%) 16 6.2 7.9 25 14 11 23 Large vessels sluggish flow (%) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Large vessels continuous flow (%) 0.9 1.7 0.0 4.9 0.1 0.0 1.0 Small vessels TVD (mm/mm2) 15 3 6 20 14 13 17 Small vessels PVD (mm/mm2) 15 4 7 20 16 14 18 Small vessels PPV (%) 80 13 42 95 81 77 86 Small vessels MFI 3 0.2 2 3 3 3 3 Other vessels TVD (mm/mm2) 3 1 1 5 3 3 4 Other vessels PVD (mm/mm2) 3 1 1 5 3 2 4 Other vessels PPV (%) 16 6.7 5.5 26 18 8.9 23 Other vessels MFI 2.9 0.2 2.6 3.0 3.0 3.0 3.0 All vessels TVD (mm/mm2) 18 3.1 10 22 18 17 20 All vessels PVD (mm/mm2) 18 3.6 8.3 22 19 17 21 All vessels PPV (%) 96 13 50 100 100 100 100 All vessels MFI 2.9 0.2 2.6 3.0 3.0 2.9 3.0 (C) Velocity/flow Small vessel average velocity (μm/sec) 433 140 288 742 407 322 475 Medium vessel average velocity (μm/sec) 441 151 160 670 439 378 534 Large vessel average velocity (μm/sec) a a a a a a a All vessel average velocity (μm/sec) 437 126 289 710 412 330 557 Small vessel average flow (μL/sec) 77 000 37 000 16 000 15 0000 76 000 47 000 110 000 Medium vessel average flow (μL/sec) 40 0000 190 000 90 000 740 000 370 000 300 000 500 000 Large vessel average flow (μL/sec) a a a a a a a All vessel average flow (μL/sec) 150 000 130 000 16 000 440 000 110 000 47 000 230 000 a Unable to calculate due to small numbers. There was no evidence in the combined group of significant change over time from 6 h of age until 72 h for any of the videomicroscopy measures (Tables 2CA– and 4CA–). While the change from 6 to 24 h of large vessel length and related parameters did reach significance (mean increase from 0.11 mm, 95th centiles 0.01–0.22, to 0.23 mm, 95th centiles 0.01–0.8, P = 0.02), there were few readings with these large vessel
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