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Biomedical subjects

Robert J Pierce

Publications and source records attributed to Robert J Pierce.

15 recordsLinked to original sources
PubMed2006

Percutaneous versus surgical tracheostomy: A randomized controlled study with long-term follow-up.

OBJECTIVE: To compare the safety, availability, and long-term sequelae of percutaneous vs. surgical tracheostomy. DESIGN: Prospective, randomized, controlled study. SETTING: Combined medical/surgical intensive care unit in a tertiary referral hospital. PATIENTS: Two hundred critically ill mechanically ventilated patients who required tracheostomy. INTERVENTIONS: Tracheostomy by either percutaneous tracheostomy or surgical tracheostomy performed in the intensive care unit. MEASUREMENTS AND MAIN RESULTS: The primary outcome measure was the aggregate incidence of predefined moderate or severe complications. The secondary outcome measures were the incidence of each of the components of the primary outcome. Long-term follow-up included clinical assessment, flow volume loops, and bronchoscopy. Both groups were well matched for age, gender, admission Acute Physiology and Chronic Health Evaluation II score, period of endotracheal intubation, reason for intubation, and admission diagnosis. There was no statistical difference between groups for the primary outcome. Bleeding requiring surgical intervention occurred in three percutaneous tracheostomy patients and in no surgical tracheostomy patient (p = .2). Postoperative infection (p = .044) and cosmetic sequelae (p = .08) were more common in surgical tracheostomy patients. There was a shorter delay from randomization to percutaneous tracheostomy vs. surgical tracheostomy (p = .006). Long-term follow-up revealed no complications in either group. CONCLUSIONS: Both percutaneous tracheostomies and surgical tracheostomies can be safely performed at the bedside by experienced, skilled practitioners.

Aged↗
PubMed2005

Inhomogeneity of ventilation leads to unpredictable errors in measured D(L)CO.

We evaluated the effects of inhomogeneity of ventilation on single-breath (SB), rebreathing (RB) and open circuit (OC) D(L)CO using a mathematical model consisting of two alveolar compartments and a common dead space. Inhomogeneity in ventilation was studied by altering inspired volume, initial alveolar volume and compartment size independently. When distribution of inspired volume between alveolar compartments was inhomogeneous (9:1), D(L)CO was underestimated by 35% for SB, 25% for RB, and 16% for OC, and there was an underestimation in V(A) of 9%, 15% and 9%, respectively. With inhomogeneity in initial alveolar volume there was an overestimation in D(L)CO of 13%, 7% and 11% for SB, RB and OC techniques and an underestimation of V(A) of 7%, 12% and 9%. Finally inhomogeneity of compartment size led to an underestimation of D(L)CO of 18%, 35% and 36% with no change in measured V(A). These results suggest D(L)CO measurements are sensitive to inhomogeneity of ventilation, and importantly, all techniques were at times, significantly in error.

Algorithms↗
PubMed2005

The effect of sleep onset on upper airway muscle activity in patients with sleep apnoea versus controls.

Pharyngeal dilator muscles are important in the pathophysiology of obstructive sleep apnoea syndrome (OSA). We have previously shown that during wakefulness, the activity of both the genioglossus (GGEMG) and tensor palatini (TPEMG) is greater in patients with OSA compared with controls. Further, EMG activity decreases at sleep onset, and the decrement is greater in apnoea patients than in healthy controls. In addition, it is known that the prevalence of OSA is greater in middle-aged compared with younger men. Thus, we had two goals in this study. First we compared upper airway muscle activity between young and middle-aged healthy men compared with men with OSA. We also explored the mechanisms responsible for the decrement in muscle activity at sleep onset in these groups. We investigated muscle activity, ventilation , and upper airway resistance (UAR) during wakefulness and sleep onset (transition from alpha to EEG activity) in all three groups. Measurements were obtained during basal breathing (BB) and nasal continuous positive airway pressure (CPAP) was applied to reduce negative pressure-mediated muscle activation). We found that during wakefulness there was a gradation of GGEMG and UAR (younger < older < OSA) and that muscle activity was reduced by the application of nasal CPAP (to a greater degree in the OSA patients). Although CPAP eliminated differences in UAR during wakefulness and sleep, GGEMG remained greater in the OSA patients. During sleep onset, a greater initial fall in GGEMG was seen in the OSA patients followed by subsequent muscle recruitment in the third to fifth breaths following the alpha to transition. On the CPAP night, and GGEMG still fell further in the OSA patients compared with control subjects. CPAP prevented the rise in UAR at sleep onset along with the associated recruitment in GGEMG. Differences in TPEMG among the groups were not significant. These data suggest that the middle-aged men had upper airway function midway between that of young normal men and the abnormal airway of those with OSA. Furthermore it suggests that the initial sleep onset reduction in upper airway muscle activity is due to loss of a 'wakefulness' stimulus, rather than to loss of responsiveness to negative pressure, and that this wakefulness stimulus may be greater in the OSA patient than in healthy controls.

Adolescent↗
PubMed2005

Cerebral structural changes in severe obstructive sleep apnea.

Obstructive sleep apnea is associated with abnormalities in neuropsychologic function, and defects in respiratory control may contribute to pathogenesis. Abnormalities may be reflected in structural brain changes. Twenty-seven male untreated patients with severe sleep apnea without comorbidities, and 24 age-matched control subjects, had T1-weighted brain imaging in a high-resolution magnetic resonance scanner. Twenty-three patients with sleep apnea had repeat imaging after 6 months of continuous positive airways pressure treatment. No areas of gray matter volume change were found in patients using an optimized voxel-based morphometry technique, at p < 0.05 adjusted for multiple comparisons (despite the method being sensitive to changes in gray matter fraction of 0.17 or less in all voxels). Furthermore, no differences were seen in bilateral hippocampal, temporal lobe, or whole brain volumes, assessed by manual tracing of anatomical borders. No longitudinal changes were seen in gray matter density or regional volumes after treatment, but whole brain volume decreased slightly. We have found no gray matter volume deficits nor focal structural changes in severe obstructive sleep apnea. Whole brain volume decreases without focal changes after 6 months of continuous positive airways pressure treatment.

Adult↗
PubMed2005

A longitudinal evaluation of sleep and breathing in the first year after cervical spinal cord injury.

OBJECTIVES: To establish the incidence of sleep disordered breathing (SDB) after acute tetraplegia and to determine the relation between the Apnea-Hypopnea Index (AHI) score and the previously postulated predictors of SDB in tetraplegia. DESIGN: Inception cohort. We performed full polysomnography immediately after acute tetraplegia and at 2, 4, 13, 26, and 52 weeks postinjury. Spirometry, maximum inspiratory and expiratory pressures, medication usage, and neck and abdominal girth were also assessed. Preinjury SDB was estimated using the multivariate apnea prediction equation. SETTING: Acute care, subacute care, and community. PARTICIPANTS: Consecutive sample with acute tetraplegia. Thirty subjects (25 men) were initially included. Thirteen completed 12 months of follow-up. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: SDB (AHI score >10 events/h) and respiratory function. RESULTS: Three subjects (10%; 95% confidence interval [CI], 2%-28%) had probable SDB before injury. In the first 48 hours after injury, no subject had SDB. At 2 weeks, 60% (95% CI, 26%-88%) had SDB; at 4 weeks, 62% (95% CI, 38%-82%); at 13 weeks, 83% (95% CI, 61%-95%); at 26 weeks, 68% (95% CI, 44%-88%); and at 52 weeks, 62% (95% CI, 32%-86%). No consistent relation was found between the previously postulated predictors and SDB. CONCLUSIONS: SDB is highly prevalent within 4 weeks of acute tetraplegia.

Abdomen↗
PubMed2005

Sleep disordered breathing in chronic stroke survivors. A study of the long term follow-up of the SCOPES cohort using home based polysomnography.

Prevalence of sleep-disordered breathing (SDB) (apnea-hypopnea index [AHI] > or = 5) in acute stroke patients ranges between 44% and 95%, compared to the community prevalence, 9 to 35% for women and 8 to 57% for men [age range 30-60 years]. Limited data exists beyond 3 months following stroke. We assessed the prevalence of SDB amongst stroke survivors at 3 years and compared results to data reported in normal and elderly populations. 90/143 eligible stroke survivors from an existing cohort underwent a home based sleep study. Mean age of the 78 subjects with a valid sleep study was 64 years (SD 15). Prevalence of SDB (AHI > or = 5) was 81% (95% CI 72% to 90%) and sleep apnoea syndrome (AHI > or = 5 plus ESS score > or =11) was 20% (95% CI 11% to 29%). Important predictors for AHI > or = 15 were haemorrhagic stroke (aOR12.06 [1.42-102.74]) and stroke severity at 1 month (aOR4.15 [1.05-16.38]). Large case-control studies are needed.

Adult↗
PubMed2005

Pulmonary artery pressure and blood flow as predictors of outcome from lung cancer resection.

OBJECTIVE: Pulmonary hypertension is a putative risk factor for lung resection but catheter measurements are invasive. The aim of the present study was to assess prediction of mortality and complications from lung resection by Doppler echocardiographic estimates of pulmonary artery pressure (PAp) and soluble gas uptake estimates of effective pulmonary blood flow (Q(RB)). METHODOLOGY: In 33 lung cancer patients, resting PAp (sys) and Q(RB) were measured preoperatively. In 13 patients, supine exercise estimates of PAp (sys) were also made and in five patients catheter PAp estimates were made. RESULTS: Baseline PAp (sys) was 35 +/- 5 mmHg in four patients who died and 35 +/- 5 mmHg in 27 survivors. Post-exercise PAp (sys) was 58 +/- 11 mmHg in non-survivors and 60 +/- 11 mmHg in survivors (both not significant). Resting Q(RB) was 3.9 +/- 0.35 L/min in two non-survivors compared with 4.7 +/- 0.90 L/min in 22 survivors (P = 0.12) and was significantly lower in those experiencing complications. Regression analysis showed no significant relationship between resting or post-exercise PAp and mortality, although low Q(RB) tended towards predicting mortality (P = 0.07). There were also trends for higher PAp (sys) to predict respiratory and cardiac complications (P = 0.08) and for lower Q(RB) to predict unspecified or surgical complications. CONCLUSION: PAp and Q(RB) did not predict outcome from lung resection better than baseline respiratory function indices.

Aged↗
PubMed2004

Sleepiness, sleep-disordered breathing, and accident risk factors in commercial vehicle drivers.

Sleep-disordered breathing and excessive sleepiness may be more common in commercial vehicle drivers than in the general population. The relative importance of factors causing excessive sleepiness and accidents in this population remains unclear. We measured the prevalence of excessive sleepiness and sleep-disordered breathing and assessed accident risk factors in 2,342 respondents to a questionnaire distributed to a random sample of 3,268 Australian commercial vehicle drivers and another 161 drivers among 244 invited to undergo polysomnography. More than half (59.6%) of drivers had sleep-disordered breathing and 15.8% had obstructive sleep apnea syndrome. Twenty-four percent of drivers had excessive sleepiness. Increasing sleepiness was related to an increased accident risk. The sleepiest 5% of drivers on the Epworth Sleepiness Scale and Functional Outcomes of Sleep Questionnaire had an increased risk of an accident (odds ratio [OR] 1.91, p = 0.02 and OR 2.23, p < 0.01, respectively) and multiple accidents (OR 2.67, p < 0.01 and OR 2.39, p = 0.01), adjusted for established risk factors. There was an increased accident risk with narcotic analgesic use (OR 2.40, p < 0.01) and antihistamine use (OR 3.44, p = 0.04). Chronic excessive sleepiness and sleep-disordered breathing are common in Australian commercial vehicle drivers. Accident risk was related to increasing chronic sleepiness and antihistamine and narcotic analgesic use.

Accident Prevention↗
PubMed2004

Efficacy of positive airway pressure and oral appliance in mild to moderate obstructive sleep apnea.

The efficacy of currently recommended treatments is uncertain in patients with mild to moderate obstructive sleep apnea (apnea-hypopnea index [AHI], 5-30). A group of 114 sleep clinic patients with an AHI of 5-30 have participated in a randomized controlled crossover trial of 3 months of treatment with each of nasal continuous positive airway pressure (CPAP), a mandibular advancement splint, and a placebo tablet. Outcomes were sleep fragmentation and hypoxemia, daytime sleepiness, quality of life, neurobehavioral function, and blood pressure. Both active treatments improved sleep outcomes, but positive airway pressure had a greater effect. The quality of life, symptoms, and subjective but not objective sleepiness improved to a similar degree with both treatments; however, many of the improvements seen in neuropsychologic function and mood were not better than the placebo effect. Some aspects of nocturnal blood pressure were improved with the splint but not with CPAP. This study has shown that although both CPAP and mandibular advancement splint effectively treated sleep-disordered breathing and sleepiness, the expected response in neurobehavioral function was incomplete. This may be due to the splint having a lesser therapeutic effect and CPAP being poorly tolerated and therefore used less in this patient group.

Continuous Positive Airway Pressure↗
PubMed2004

The maintenance of wakefulness test in normal healthy subjects.

STUDY OBJECTIVES: The Maintenance of Wakefulness Test (MWT) examines an individual's ability to stay awake in an environment of decreased sensory stimulation. Only 1 previous study has systematically examined the MWT in normal healthy subjects. SETTING: Sleep disorders unit laboratory PARTICIPANTS AND DESIGN: 31 subjects (mean age 48.5 years, SD 9.6; 8 women) were randomly selected via the telephone directory within a 30-km radius of the test centers. They answered a general screen for health complaints (respiratory, cardiovascular, and psychiatric disorders) and sleep difficulties (snoring). INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Overnight polysomnography and a 40-minute MWT the following day were performed on all subjects. Mean sleep latency to the first epoch of unequivocal sleep during the 40-minute trial MWT was 36.9 +/- 5.4 (SD) minutes. The lower normal limit, defined as 2 SD below the mean, was therefore 26.1 minutes. Mean sleep latency for the first 20 minutes of the trial (with sleep latency defined as time to the first appearance of 1 epoch of stage 1 sleep or a 10-second microsleep) was 18.6 +/- 2.3 minutes, with a lower normal limit of 14.0 minutes. CONCLUSIONS: The mean results are consistent with previously published normative data. However, the SDs found in this study are smaller, and, thus, the lower normal limit suggested here is 4 to 6 minutes longer. The subjects in this study were randomly selected from the general population and may, therefore, be a truer representation of the normal population than in the previous study in which subjects were recruited via hospital advertisements and word of mouth.

Body Mass Index↗
PubMed2004

Factors associated with maintenance of wakefulness test mean sleep latency in patients with mild to moderate obstructive sleep apnoea and normal subjects.

This study investigated the possible factors related to the Maintenance of Wakefulness Test (MWT) mean sleep latency. A second analysis explored the characteristics of subjects who had discrepant Epworth Sleepiness Scale (ESS) and MWT scores. A total of 151 subjects (110 mild to moderate obstructive sleep apnoea (OSA) patients and 41 control subjects) were recruited for the study. The subjects completed an overnight Polysomnography (PSG), MWT, cognitive, performance and vigilance tasks and answered self-report questionnaires on mood and sleepiness. A forward stepwise multiple regression was performed on MWT mean sleep latency. The predictor variables age (r = 0.28), subjective sleep history for 1 week prior to MWT (sleep diary; r = 0.19) and number of >4% SaO2 Dips during the PSG (r = -0.21) best explained the MWT results, but only accounted for 12.8% of the variance in the test. It was found that 33% of subjects had discrepant ESS and MWT scores. A new variable was created to analyse these subjects (MWT/ESS discrepancy score; MED). A forward stepwise multiple regression analysis found that depression, performance errors and sleep disordered breathing explained 13.4% of the variance in MED scores. The MWT is a complex behavioural test whose scores do not seem to have a very robust relationship with potential predictors and co-correlates. Further comprehensive study is needed if the test is to be used in a diagnostically meaningful way.

Body Mass Index↗
PubMed2003

Control of upper airway muscle activity in younger versus older men during sleep onset.

Pharyngeal dilator muscles are clearly important in the pathophysiology of obstructive sleep apnoea syndrome (OSA). We have previously shown that the activity of both the genioglossus (GGEMG) and tensor palatini (TPEMG) are decreased at sleep onset, and that this decrement in muscle activity is greater in the apnoea patient than in healthy controls. We have also previously shown this decrement to be greater in older men when compared with younger ones. In order to explore the mechanisms responsible for this decrement in muscle activity nasal continuous positive airway pressure (CPAP) was applied to reduce negative pressure mediated muscle activation. We then investigated the effect of sleep onset (transition from predominantly alpha to predominantly theta EEG activity) on ventilation, upper airway muscle activation and upper airway resistance (UAR) in middle-aged and younger healthy men. We found that both GGEMG and TPEMG were reduced by the application of nasal CPAP during wakefulness, but that CPAP did not alter the decrement in activity in either muscle seen in the first two breaths following an alpha to theta transition. However, CPAP prevented both the rise in UAR at sleep onset that occurred on the control night, and the recruitment in GGEMG seen in the third to fifth breaths following the alpha to theta transition. Further, GGEMG was higher in the middle-aged men than in the younger men during wakefulness and was decreased more in the middle-aged men with the application of nasal CPAP. No differences were seen in TPEMG between the two age groups. These data suggest that the initial sleep onset reduction in upper airway muscle activity is due to loss of a 'wakefulness' stimulus, rather than to loss of responsiveness to negative pressure. In addition, it suggests that in older men, higher wakeful muscle activity is due to an anatomically more collapsible upper airway with more negative pressure driven muscle activation. Sleep onset per se does not appear to have a greater effect on upper airway muscle activity as one ages.

Adolescent↗
PubMed2003

Severe gastroesophageal reflux is associated with reduced carbon monoxide diffusing capacity.

OBJECTIVE: To assess whether severe gastroesophageal reflux (GER) is associated with abnormalities in lung function including measures of lung volume and gas diffusion. METHODS: Data from 147 patients with obesity (body mass index [BMI] range, 31.7 to 70 kg/m(2)) who presented for obesity surgery was analyzed retrospectively. A questionnaire was completed preoperatively that included a history of GER, frequency and severity of symptoms, investigations, and medications used. A history of lung disease, sleep-disordered breathing, and smoking also was obtained. A physician who was blinded to lung function graded GER severity prospectively by the results of pH monitoring and/or gastroscopy, and medication use. Spirometry, lung volumes, and gas transfer were measured preoperatively. RESULTS: Patients with severe GER had reduced levels of the diffusing capacity of the lung for carbon monoxide (DLCO) [21.1 mL/min/mm Hg; 95% confidence interval (CI), 18.9 to 23.2], as measured by CO transfer, compared with those patients without GER (26.3 mL/min/mm Hg; 95% CI, 24.4 to 28.2; p = 0.001). This remained significant after adjusting for age, gender, BMI, and smoking history. Gas transfer corrected for lung volume also was reduced in the group with severe GER (4.6 mL/min/mm Hg per L; 95% CI, 4.3 to 4.9) compared to the group without GER (5.3 mL/min/mm Hg per L; 95% CI, 5.1 to 5.5; p = 0.001). There was no significant difference in other measures of lung function. CONCLUSIONS: Severe GER is associated with an impairment of gas exchange. This may be due to microaspiration of gastric acid or fluid into the airways.

Adult↗
PubMed2002

A randomized controlled trial of continuous positive airway pressure in mild obstructive sleep apnea.

A common clinical dilemma faced by sleep physicians is in deciding the level of severity at which patients with obstructive sleep apnea (OSA) should be treated. There is particular uncertainty about the need for, and the effectiveness of, treatment in mild cases. To help define the role of nasal continuous positive airway pressure (CPAP) treatment in mild OSA we undertook a randomized controlled cross-over trial of CPAP in patients with an apnea- hypopnea index (AHI) of 5 - 30 (mean, 12.9 +/- 6.3 SD). Twenty-four-hour blood pressure and neurobehavioral function were measured at baseline, after 8 wk of treatment with CPAP, and after 8 wk of treatment with an oral placebo tablet. Twenty-eight of 42 patients enrolled in the study completed both treatment arms. Baseline characteristics were not different between those who completed the study and those who did not complete the study. Patients used CPAP for a mean (SD) of 3.53 (2.13) h per night and the mean AHI on the night of CPAP implementation was 4.24 (2.9). Nasal CPAP improved self-reported symptoms of OSA, including snoring, restless sleep, daytime sleepiness, and irritability (in-house questionnaire), more than did placebo, but did not improve objective (Multiple Sleep Latency Test) or subjective (Epworth Sleepiness Scale) measures of daytime sleepiness. We found no benefit of CPAP over placebo in any tests of neurobehavioral function, generic SF-36 (36-item Short Form Medical Outcomes Survey) or sleep-specific (Functional Outcomes of Sleep Questionnaire) quality of life questionnaires, mood score (Profile of Moods States and Beck Depression Index), or 24-h blood pressure. However, the placebo tablet resulted in a significant improvement in a wide range of functional variables compared with baseline. This placebo effect may account for some of the treatment responses to CPAP observed previously in patients with mild OSA.

Adult↗