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PubMed2006

Additional computed tomography scans in the prone position to distinguish early interstitial lung disease from dependent density on helical computed tomography screening patient characteristics.

BACKGROUND: The purpose of this study was to evaluate the benefit of additional prone CT scanning to helical CT screening to detect early interstitial lung disease (ILD). METHODS: Helical CT screening was performed as an optional test in 1098 subjects during their annual health examination. Subjects with parenchymal abnormalities in the posterior subpleural aspect of the lung were advised to receive additional CT scans in the prone position. The CT images were assessed independently by both a radiologist and a chest specialist without reference to clinical data. RESULTS: Ninety-three subjects (8%) had parenchymal abnormalities in the posterior subpleural aspect of the lung and 75 subjects (7%) received additional CT scans. These revealed 72 dependent densities and three early ILD (0.3%). By multivariate analysis, subjects aged over 70 years, with obesity (BMI >or= 25) and currently smoking (pack years >or= 20) had a tendency to have dependent density on helical CT, the predominant distribution of which was in the middle lung fields. CONCLUSIONS: Additional CT scans were performed in 7% of subjects after abnormal CT screening and three early ILD were detected. Therefore, we recommend that additional CT scans in prone position be performed to detect early ILD after abnormal helical CT screening.

Age Factors↗
PubMed2006

Haemodynamic effects of the prone position: a comparison of propofol total intravenous and inhalation anaesthesia.

The haemodynamic changes of the prone position were investigated in 40 ASA I-II patients undergoing lumbar spine surgery. Patients were randomly assigned, following propofol intravenous induction, to receive maintenance of anaesthesia using either isoflurane 1-1.2% in air or target controlled propofol 3 microg.ml(-1) infusion. Measurements of non-invasive blood pressure, heart rate and cardiac output were made in the supine position. The patient was then turned prone onto a Montreal pattern mattress and measurements repeated. Cardiac output measurements were made using a non-invasive cardiac output monitor. We found a significant reduction in cardiac index in both groups and a significantly greater change with propofol compared to isoflurane on turning supine to prone (CI change 0.4 vs 0.7 l.min(-1).m(-2) p = 0.001 and SVRI change 89 vs 177 dyne.s(-1).cm(-5), p = 0.041). We conclude that turning healthy patients prone produces a clinically significant reduction in cardiac output, the change being greater during maintenance of anaesthesia using propofol compared to isoflurane.

Adolescent↗
PubMed2002

A protocolized approach to pulmonary failure and the role of intermittent prone positioning.

INTRODUCTION: We present a series of adult patients treated under a protocol for severe lung failure (acute respiratory distress syndrome [ARDS]) that uses positive end-expiratory pressure (PEEP) optimization and intermittent prone positioning (IPP) to reduce shunt, improve oxygen (O(2)) delivery, and reduce FiO(2). METHODS: Trauma, emergency vascular, and general surgical patients with PaO(2)/FiO)(2) (PF) ratio < 200 were entered into a protocol designed to maintain mixed venous saturation (SVO(2)) > 70% with FiO(2) < 0.50. Therapy involved a sequential algorithmic approach that included pulmonary artery oximetry, "best-PEEP" determination, optimization of cardiac function, limitation of VO(2), transfusion to hematocrit of 35%, frequent bronchoscopy, rational diuresis and, if the FiO(2) was > 0.50, a trial of IPP with every-6-hour rotations. Unstable spine fractures and pelvic external fixators were the only contraindications to IPP. We collected data prospectively and from the charts and trauma registry. RESULTS: Forty adults were treated by protocol, 29 were injured and 11 had vascular or general surgical primary problems. The patients were 46.3 +/- 3.1 years old (the trauma patients were 42.9 +/- 3.2, and the vascular/general patients were 62 +/- 7.5 years old). Average Injury Severity Score was 25.9 +/- 3.7 and the Murray lung injury score was 2.65 +/- 0.9. IPP was used in all patients including those with recent tracheostomy, open abdomens, laparotomy, thoracotomy, leg external fixators, central nervous system injury, continuous venovenous hemofiltration and extracorporeal membrane oxygenation cannulae, vasopressor therapy, recent chest wall open reduction and internal fixation, and facial fractures. With the initiation of IPP therapy, the PF ratio increased from 132.1 +/- 8.5 to 231.6 +/- 14.2 (p < 0.001), the FiO(2) was decreased from 65.9 +/- 4.0% to 47.0 +/- 1.1% (p < 0.001), and the SVO(2) increased from 75.3 +/- 1.8% to 78.6 +/- 1.6% (p = 0.023). PEEP and static compliance were unchanged. The duration of IPP was 85.6 +/- 14.9 hours (median, 55 hours; range, 12 to 490 hours). Within 48 hours, all patients were on FiO(2) < or = 50. Mortality was 20% (14% for trauma) and none died of ARDS. The only complications of IPP were one case of partial-thickness skin loss from a malpositioned nasogastric tube and a case of transient lingual edema. CONCLUSION: IPP was independently responsible for an increase in PF ratio and SVO(2). We effectively and safely used IPP in our patients with ARDS, including many with issues generally considered to be contraindications. IPP and best-PEEP therapy enabled us to wean all of our patients' Fio2 to < or = 0.50 within 48 hours of ARDS onset.

Adolescent↗
PubMed2001

Abdomen release in prone position does not improve oxygenation in an experimental model of acute lung injury.

OBJECTIVE: To analyze the effect of abdomen release in the prone position on oxygenation in an experimental model of acute lung injury. DESIGN: Experimental randomized controlled study. SETTING: Experimental laboratory of a tertiary university hospital. PARTICIPANTS: Mixed-breed adolescent pigs weighing between 25-31 kg. INTERVENTIONS: Thirty minutes after pulmonary edema was produced with oleic acid, the animals were turned prone and randomized into two groups: group I or control (n = 9), lying directly on the operating table; and group II (n = 11) with abdomen release, with positioning rolls under the upper part of the chest wall and the pelvis to allow free movement of the abdomen. MEASUREMENTS AND RESULTS: The gas exchange, respiratory mechanics, hemodynamics, intra-abdominal pressure (IAP) and the extravascular lung water (EVLW), determined by double indicator dilution method (DI), were recorded at baseline (time 0) and at 30, 60, 90, 120 and 150 min. The PaO2/FIO2 increased in both groups at 30 min after the pigs were placed in the prone position (time 60) and then decreased progressively until the end of the experimental period, with no statistical differences between the groups at any time (73.1 +/- 14.5 vs 79.5 +/- 14.9 at 150 min). Abdomen release was not associated with changes in the respiratory mechanics, EVLW or intra-abdominal pressure. CONCLUSIONS: Abdomen release in prone position does not improve oxygenation in an experimental model of acute lung injury.

Animals↗
PubMedDate not supplied

Nursing patients with ARDS in the prone position.

This article examines the main features of acute respiratory distress syndrome (ARDS), including the pathophysiology, clinical manifestations, complications and treatment. Patients with ARDS are critically ill and require close monitoring and mechanical ventilation in an intensive care unit. The benefits of prone positioning, one of the main treatment options for these patients, are discussed in detail. By understanding the physiological principles that underpin the prone position, the critical care nurse will be more effective in identifying patients who might benefit from this treatment.

Blood Gas Analysis↗
PubMed2006

Gravity-dependent signal gradients on MR images of the lung in supine and prone positions: a comparison with isogravitational signal variability.

PURPOSE: To investigate the tendency of proton MR signal intensity (SI) gradients to be steeper in the supine than in the prone body position, and to quantify the relation between gravity-related and isogravitational changes of SI on proton MR images of the lung. MATERIALS AND METHODS: In eight healthy volunteers, MR images were obtained in the supine and prone positions using a multiple inversion recovery turbo spin-echo (TSE) sequence. The variation in SI along the gravity-dependent direction and within isogravitational planes was measured on a pixel-by-pixel basis. Ratios of slopes were calculated for comparisons among volunteers. Comparisons of ratios were made using Fisher's exact test. Isogravitational variability was compared with the mean SI, the signal-to-noise ratio (SNR), and the image noise. RESULTS: The average ratios of slopes showed that the overall SI gradient was steeper in the supine than the prone position, with a substantial difference in the supine/prone ratios between inspiration (1.21) and expiration (1.72). In both the supine and prone positions, gravity-dependent gradients were steeper in expiration than in inspiration (P = 0.001). The SI variability along the gravitational direction was larger than the isogravitational variability. The isogravitational variability in turn was larger than the image noise but smaller than the mean SI of the MR images. CONCLUSION: Gravity-dependent gradients in proton MR SI are steeper in the supine than in the prone position. The magnitudes of these gradients were larger than the isogravitational signal variability, showing that MRI is sensitive to gravitationally induced effects.

Adult↗
PubMed1998

Prone positioning in acute lung injury.

More than 20 years ago, critical care workers first observed that oxygenation improved when patients with acute respiratory distress syndrome were ventilated in the prone position. In recent reports, on turning prone, from 50 to 100% of patients improve oxygenation to a degree sufficient to allow a reduction in the level of positive end-expiratory pressure or fraction of inspired oxygen. It appears that vascular conductance in lung regions previously in the dorsal position is augmented by an increase in air space volume, with the effect that prone position ventilation will reduce shunt and improve ventilation-perfusion mismatch. Factors determining which patients will respond have not yet been elucidated. Although many questions regarding the role of prone ventilation are unanswered, of greatest importance is whether this technique reduces morbidity and mortality of patients with acute respiratory failure. Only carefully conducted, randomized trials can answer this question.

Acute Disease↗
PubMed1991

The prone position for the surgical patient: a historical review of the principles and hazards.

Since the 1940s there has been an increase in the number of patients submitted for surgery of the spinal axis necessitating use of the prone position. Specifically designed operating tables were both rare and expensive, and probably only existed in a few highly specialized centres. Apparatus which could be easily made locally and used in conjunction with normal operating tables has been invented and generally used to good effect. The important historical landmarks in these developments are traced and a review of the methods and hazards is presented. Similar methods evolved almost simultaneously in differing centres. It is recommended that the Tarlov "seated prone" position should be widely used, in view of its physiological advantages and lack of adverse reports.

History, 20th Century↗
PubMed1999

Effects of prone position on alveolar recruitment and oxygenation in acute lung injury.

OBJECTIVE: To investigate the effects of prone position (PP) on alveolar recruitment and oxygenation in acute respiratory failure. DESIGN: Prospective physiologic study. SETTING: Medical ICU two in a university hospital. PATIENTS: Twelve adult patients intubated and mechanically ventilated with medical primary acute lung injury/adult respiratory distress syndrome (ALI/ARDS) in whom PP was indicated. MEASUREMENTS AND RESULTS: We constructed the static inflation volume-pressure curves (V-P) of the respiratory system in the 12 patients and differentiated between lung and chest wall in ten of them. We determined the difference between end-expiratory lung volume on positive end-expiratory pressure (PEEP) and relaxation volume of the respiratory system on zero PEEP (delta FRC). The recruited alveolar volume was computed as the delta FRC times the ratio of static elastance of the respiratory system to the lung. These measurements together with arterial blood gases determination were made in supine position (SP1), after 1 h of PP and after 1 h of supine repositioning (SP2) at the same level of PEEP. The PaO2/FIO2 ratio improved from SP1 to PP (136 +/- 17 vs 204 +/- 24 mm Hg; p < 0.01). An PP-induced alveolar recruitment was found in five patients. The change in oxygenation correlated to the recruited volume. The static elastance of the chest wall decreased from 4.62 +/- 0.99 cmH2O/l in SP1 to 6.26 +/- 0.54 cmH2O/l in PP (p < 0.05) without any correlation to the change in oxygenation. CONCLUSIONS: Alveolar recruitment may be a mechanism of oxygenation improvement in some patients with acute hypoxemic respiratory failure. No correlation was found between change in oxygenation and chest wall elastic properties.

Adult↗
PubMed2006

Reducing ventilator-induced lung injury and other organ injury by the prone position.

Mechanical ventilation can cause structural and functional disturbances in the lung, as well as other vital organ dysfunctions. Apoptosis is thought to be a histological sign of distant organ damage in ventilator-induced lung injury (VILI). Nakos and colleagues observed a protective effect of prone positioning against VILI in normal sheep. Less alteration in the lung architecture and function and in liver transaminases, and lower indices for apoptosis in the liver, the diaphragm and the lung were noted in the prone position compared with the supine position. If confirmed, these data open a new hypothesis for pathogenesis and prevention of VILI and its extrapulmonary complications.

Animals↗
PubMed2002

Sigh in supine and prone position during acute respiratory distress syndrome.

Interventions aimed at recruiting the lung of patients with acute respiratory distress syndrome (ARDS) are not uniformly effective. Because the prone position increases homogeneity of inflation of the lung, we reasoned that it might enhance its potential for recruitment. We ventilated 10 patients with early ARDS (PaO2/FIO2, 121 +/- 46 mm Hg; positive end-expiratory pressure, 14 +/- 3 cm H2O) in supine and prone, with and without the addition of three consecutive "sighs" per minute to recruit the lung. Inspired oxygen fraction, positive end-expiratory pressure, and minute ventilation were kept constant. Sighs increased PaO2 in both supine and prone (p < 0.01). The highest values of PaO2 (192 +/- 41 mm Hg) and end-expiratory lung volume (1840 +/- 790 ml) occurred with the addition of sighs in prone and remained significantly elevated 1 hour after discontinuation of the sighs. The increase in PaO2 associated with the sighs, both in supine and prone, correlated linearly with the respective increase of end-expiratory lung volume (r = 0.82, p < 0.001). We conclude that adding a recruitment maneuver such as cyclical sighs during ventilation in the prone position may provide optimal lung recruitment in the early stage of ARDS.

Aged↗
PubMed1982

[Visualization of the pancreas in the prone position with an automated water-coupled multisector scanner (Octoson)].

In a comparative study involving 300 patients the pancreas was demonstrated using the Combison 100 real-time system and the Combison 202 (compound-scanner) with the patients in supine position (without administration of methylcellulose or water) as well as with Octoson with the patient in the prone position. Both studies were performed within 1 hour in each case. Distribution of air in the abdomen is altered when the patient assumes the prone position for the Octoson study, a fact confirmed by 100 radiological examinations. This alteration in the distribution of air (in the abdomen) results in less interference when the pancreas is demonstrated. Other factors influencing visualization of the pancreas include: interposition of subcutaneous and omental fat (which cases absorption and defocussing of the ultrasonic beam) infiltrating of the pancreas by fat (lipomatosis) cutaneous scars, and hair, which disturbs contact between the transducer and the skin.

Humans↗
PubMed1985

Evaluation of the prone position in digital subtraction angiography of the kidneys.

In visualizing the kidneys and renal arteries, the digital subtraction angiography (DSA) image is degraded by peristalsis and overlying bowel gas. In 25 patients we evaluated the efficacy of the prone position to counter these technical difficulties and found that the prone position offers visualization superior to the supine, especially in obese and uncooperative patients and those with abundant bowel gas. We advocate that prone imaging be included routinely in renal DSA.

Adult↗
PubMed1989

Use of a convex mirror in indirect ophthalmoscopy for patients in a prone position.

Fundus examination with the patient in a prone position sometimes requires the observer to assume an uncomfortable position. I describe using a convex rear-view mirror with an 800-mm radius of curvature in binocular indirect ophthalmoscopy to overcome this difficulty. This device is especially helpful in pneumatic retinopexy.

Fundus Oculi↗
PubMed2001

The prone position is associated with a decrease in respiratory system compliance in healthy anaesthetized infants.

Ten healthy (ASA I or II) anaesthetized infants undergoing clubfoot surgery were studied. General anaesthesia included rocuronium, nitrous oxide and isoflurane. Volume controlled ventilation (12 ml.kg-1) was delivered via a coaxial Mapleson-D (Bain) system and a Datex AS/3 ventilator. Pulmonary mechanics were measured sequentially in the supine and prone positions using a Bicore CP-100 pulmonary function monitor. Subjects had a mean age of 6 (+/- 2) months and a mean weight of 8.3 (+/- 1.4) kg. Dynamic compliance (CDYN) and static compliance (CSTAT) were both significantly lower in the prone position than in the supine position (P < 0.0005). Mean CDYN decreased from 14.9 +/- 4.9 ml.cmH2O-1 (supine) to 11.6 +/- 3.5 ml.cmH2O-1 (prone). Mean CSTAT decreased from 10.2 +/- 2.8 ml.cmH2O-1 (supine) to 8.9 +/- 2.3 ml.cmH2O-1 (prone). No clinically significant differences in gas exchange were noted, however, on repositioning.

Anesthesia, General↗
PubMed2003

[Techniques and complementary techniques. Complementary treatments: nitric oxide, prone positioning and surfactant].

The management of hypoxic respiratory failure is based on oxygen delivery and ventilatory support with lung-protective ventilation strategies. Better understanding of acute lung injury have led to new therapeutic approaches that can modify the outcome of these patients. These adjunctive oxygenation strategies include inhaled nitric oxide and surfactant delivery, and the use of prone positioning. Nitric oxide is a selective pulmonary vasodilator that when inhaled, improves oxygenation in clinical situations such as persistent pulmonary hypertension of the newborn, pulmonary hypertension associated with congenital heart disease, and acute respiratory distress syndrome (ARDS). When applied early in ARDS, prone positioning improves distribution of ventilation and reduces the intrapulmonary shunt. The surfactant has dramatically decreased mortality caused by hyaline membrane disease in premature newborns, although the results have been less successful in ARDS. Greater experience is required to determine whether the combination of these treatments will improve the prognosis of these patients.

Adult↗
PubMed1995

Extraperitoneal laparoscopic paraaortic lymph node sampling in prone position: development of a technique.

Paraaortic lymph node sampling has been found to be efficient in the staging of genitourinary cancers. However, the complications associated with this procedure using the traditional transperitoneal or extraperitoneal approach are considerable. Developments in endoscopic technology and instrumentation have allowed an extraperitoneal approach. Presented is a porcine model for extraperitoneal endoscopic paraaortic lymph node dissection as a staging procedure for genitourinary cancers. The pig is placed in a prone position, and an extraperitoneal pneumoperitoneum is created. Using a three-port technique, we were able to remove almost 95% of all paraaortic lymph nodes laparoscopically without any complications. The prone position allows for a fast and safe procedure because it minimizes the need for extra entry ports and gives a clear view, unobstructed by the bowel, of the back wall of the abdomen.

Animals↗