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Biomedical subjects

Patrick J Hanly

Publications and source records attributed to Patrick J Hanly.

8 recordsLinked to original sources
PubMed2007

Effects of continuous positive airway pressure on cerebral vascular response to hypoxia in patients with obstructive sleep apnea.

RATIONALE: The mechanism leading to increased risk of stroke in patients with obstructive sleep apnea (OSA) is unknown. It may occur through alteration in the regulation of cerebral blood flow, reflected in part by the response of the cerebral vasculature to hypoxia. We hypothesized that the cerebrovascular response to hypoxia is reduced in patients with OSA. OBJECTIVE: To determine the cerebral blood flow response to hypoxia in patients with OSA. METHODS: The cerebral blood flow response to 20 minutes of isocapnic hypoxia was measured in eight male patients with OSA before and after 4 to 6 weeks of continuous positive airway pressure (CPAP) therapy and in 10 matched healthy control subjects. MEASUREMENTS AND MAIN RESULTS: The cerebral blood flow response to hypoxia was significantly lower in patients with OSA compared with control subjects (0.56 +/- 0.10 vs. 0.97 +/- 0.09% [mean +/- SE] change in blood flow velocity per % desaturation; p=0.007). After CPAP therapy, the cerebral blood flow response to hypoxia was similar between patients with OSA and control subjects (1.08 +/- 0.15 vs. 0.92 +/- 0.13% change in blood flow velocity per % desaturation; p=0.4). Moderately strong correlations were found between the cerebral blood flow response to hypoxia and the apnea-hypopnea index (r=-0.57; p=0.04) and nocturnal oxyhemoglobin saturation (r=0.48; p=0.01). CONCLUSIONS: The cerebral blood flow response to hypoxia is significantly reduced in patients with OSA. Treatment of OSA with CPAP increases the cerebral blood flow response to hypoxia to normal levels. An attenuated cerebrovascular response to hypoxia in patients with OSA may contribute to their elevated risk of stroke.

Adult↗
PubMed2006

Intermittent hypoxia and vascular function: implications for obstructive sleep apnoea.

Obstructive sleep apnoea (OSA) has been implicated as a risk factor for the development of hypertension, stroke and myocardial infarction. The main cause of cardiovascular and cerebrovascular disease in OSA is thought to be exposure to intermittent hypoxia, which can lead to oxidative stress, inflammation, atherosclerosis, endothelial dysfunction and hypertension. These proposed mechanisms have been drawn from basic research in animal and human models of intermittent hypoxia in addition to clinical investigation of patients with OSA. This review outlines the association between OSA and vascular disease, describes basic mechanisms that may be responsible for this association and compares the results from studies of OSA subjects with those in experimental models of intermittent hypoxia.

Animals↗
PubMed2005

Overnight changes of chemoreflex control in obstructive sleep apnoea patients.

We hypothesized that the numerous episodes of hypoxia, hypercapnia and arousal experienced by obstructive sleep apnoea (OSA) patients induce overnight changes in respiratory chemoreflexes. A modification of the Read rebreathing technique assessed chemoreflex characteristics in the evening and the morning of patients undergoing diagnostic assessment for OSA in a clinical sleep laboratory. Two groups were studied: those with apnoea-hypopnoea indices (AHI) greater than 30 composed the OSA group (n = 12), and those with AHI indices less than 10 composed the non-OSA group (n = 12). There was a significant (approximately 30%) overnight increase in chemoreflex sensitivities, without changes in thresholds, in the OSA group. In the non-OSA group there was a significant overnight reduction in chemoreflex thresholds (approximately 5%), without changes in sensitivities. We suggest that these changes affect the stability of the chemoreflex control system in opposite ways as the night proceeds: destabilizing breathing for patients in the OSA group, and stabilising breathing for patients in the non-OSA group.

Adult↗
PubMed2003

Contribution of the intensive care unit environment to sleep disruption in mechanically ventilated patients and healthy subjects.

Recent studies have challenged the traditional hypothesis that excessive environmental noise is central to the etiology of sleep disruption in the intensive care unit (ICU). We characterized potentially disruptive ICU noise stimuli and patient-care activities and determined their relative contributions to sleep disruption. Furthermore, we studied the effect of noise in isolation by placing healthy subjects in the ICU in both normal and noise-reduced locations. Seven mechanically ventilated patients and six healthy subjects were studied by continuous 24-hour polysomnography with time-synchronized environmental monitoring. Sound elevations occurred 36.5 +/- 20.1 times per hour of sleep and were responsible for 20.9 +/- 11.3% of total arousals and awakenings. Patient-care activities occurred 7.8 +/- 4.2 times per hour of sleep and were responsible for 7.1 +/- 4.4% of total arousals and awakenings. Healthy subjects slept relatively well in the typically loud ICU environment and experienced a quantitative, but not qualitative, improvement in sleep in a noise-reduced, single-patient ICU room. Our data indicate that noise and patient-care activities account for less than 30% of arousals and awakenings and suggest that other elements of the critically ill patient's environment or treatment should be investigated in the pathogenesis of ICU sleep disruption.

Adult↗
PubMed2003

Daytime sleepiness in patients with CRF: impact of nocturnal hemodialysis.

BACKGROUND: Patients with end-stage renal disease (ESRD) have a high prevalence of sleep disorders, which are not improved by conventional hemodialysis (CHD). Although sleep disorders are commonly associated with complaints of excessive daytime sleepiness, the severity and pathogenesis of daytime sleepiness has not been evaluated objectively in patients with ESRD. Nocturnal hemodialysis (NHD) is a new technique that provides better clearance of uremic toxins than CHD and, consequently, may improve sleep quality and daytime sleepiness. The authors wished to determine the severity and pathogenesis of daytime sleepiness in patients with ESRD and evaluate the impact of NHD. METHODS: Sleep quality was monitored by overnight polysomnography, and daytime sleepiness was assessed by the multiple sleep latency test (MSLT). These measurements were performed in 24 patients (15 men and 9 women, 44 +/- 10 years) while on treatment with CHD and were repeated in 15 patients after conversion to NHD. RESULTS: The majority (54%) of patients on CHD were pathologically sleepy (somnolent group, mean sleep latency <5 minutes), and, in comparison with the remaining patients (alert group, mean sleep latency >5 minutes), their blood urea nitrogen (BUN; 77.9 +/- 9.8 v 60.2 +/- 12.0 mg/dL, P < 0.001; 27.8 +/- 3.5 v 21.5 +/- 4.3 mmol/L; P < 0.001), and periodic limb movement (PLM) index (57 +/- 47 v 6 +/- 10/hr; P = 0.002) were significantly higher. Furthermore, sleep latency was correlated with BUN (R = 0.58, P = 0.008). After conversion to NHD, there was a significant fall in BUN and the severity of sleep apnea, but the overall frequency of PLM and sleep fragmentation remained elevated. Nevertheless, there was a trend for the Somnolent group to become less sleepy on NHD, and this was associated with a modest reduction in the frequency of PLM. CONCLUSION: Excessive daytime sleepiness occurs in approximately 50% of patients with ESRD. The etiology appears to be related both to uremia and sleep fragmentation associated with PLM.

Adult↗
PubMed2003

Gender differences in sleep apnea: the role of neck circumference.

STUDY OBJECTIVES: To determine whether differences in sleep apnea severity between men and women referred to a sleep clinic are related to the differences in neck circumference (NC). STUDY DESIGN: Case series. SETTING: University hospital sleep disorders clinic. PARTICIPANTS: A total of 3,942 patients (2,753 men and 1,189 women) referred to the sleep clinic. MEASUREMENTS AND RESULTS: All patients underwent nocturnal polysomnography. NC was used as a surrogate measure of upper airway obesity. We found that sleep apnea, defined an the apnea/hypopnea index (AHI) > 10/h, was significantly more frequent (60% vs 32%, chi(2) < 0.0001) and severe (mean +/- SE, 25 +/- 26/h vs 12 +/- 19/h, p < 0.0001) in men than in women. Men had significantly larger NC than women, but the difference became much less pronounced when we normalized NC to body height (0.24 +/- 0.02 vs 0.23 +/- 0.03, p < 0.0001). Men had significantly higher AHI than women even after controlling for age, body mass index (BMI), and neck/height ratio (NHR); analysis of covariance showed that mean AHI was 24.4 +/- 0.4 in men vs 14.8 +/- 0.7 in women (p < 0.0001). This difference persisted even when we matched men and women for NHR and BMI. Finally, multiple regression analysis revealed the following: (1) NHR was the most significant predictor of AHI, accounting for 19% of the variability; and (2) the slope of AHI vs NHR was significantly higher in men than in women. CONCLUSIONS: We conclude the following: (1) the frequency and severity of sleep apnea in the sleep clinic population is greater in men than women, and (2) factors other than NC, age, and BMI must contribute to these gender differences.

Anthropometry↗
PubMedDate not supplied

Comparison of the OxyMask and Venturi mask in the delivery of supplemental oxygen: pilot study in oxygen-dependent patients.

BACKGROUND: The OxyMask (Southmedic Inc, Canada) is a new face mask for oxygen delivery that uses a small 'diffuser' to concentrate and direct oxygen toward the mouth and nose. The authors hypothesized that this unique design would enable the OxyMask to deliver oxygen more efficiently than a Venturi mask (Hudson RCI, USA) in patients with chronic hypoxemia. METHODS: Oxygen-dependent patients with chronic, stable respiratory disease were recruited to compare the OxyMask and Venturi mask in a randomized, single-blind, cross-over design. Baseline blood oxygen saturation (SaO2) was established breathing room air, followed in a random order by supplemental oxygen through the OxyMask or Venturi mask. Oxygen delivery was titrated to maintain SaO2 4% to 5% and 8% to 9% above baseline for two separate 30 min periods of stable breathing. Oxygen flow rate, partial pressure of inspired and expired oxygen (PO2) and carbon dioxide (PCO2), minute ventilation, heart rate, nasal and oral breathing, SaO2 and transcutaneous PCO2 were collected continuously. The study was repeated following alterations to the OxyMask design, which improved clearance of carbon dioxide. RESULTS: Thirteen patients, aged 28 to 79 years, were studied initially using the original OxyMask. Oxygen flow rate was lower, inspired PO2 was higher and expired PO2 was lower while using the OxyMask. Minute ventilation and inspired and expired PCO2 were significantly higher while using the OxyMask, whereas transcutaneous PCO2, heart rate and the ratio of nasal to oral breathing did not change significantly throughout the study. Following modification of the OxyMask, 13 additional patients, aged 18 to 79 years, were studied using the same protocol. The modified OxyMask provided a higher inspired PO2 at a lower flow rate, without evidence of carbon dioxide retention. CONCLUSIONS: Oxygen is delivered safely and more efficiently by the OxyMask than by the Venturi mask in stable oxygen-dependent patients.

Adolescent↗