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O'Connor AR, Stephenson TJ, Johnson A, Tobin MJ, Ratib S, Moseley M, Fielder AR. Visual function in low birthweight children. Br J Ophthalmol 2004; 88:1149-53. [PMID: 15317706 PMCID: PMC1772308 DOI: 10.1136/bjo.2003.035154] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AIM To determine the visual functions, at age 10-12 years, of a geographically based cohort of children of birth weight less than 1701 g. The results were compared to a group of children born at full term. METHODS 572 low birthweight (LBW) "low birthweight cohort" children who had been examined in the neonatal period were invited for review at 10-12 years of age. 169 11 year old schoolchildren born at full term were also recruited, "school cohort." Visual acuity (at distance and near), contrast sensitivity, colour vision, and visual fields were measured. RESULTS 293 of the original 572 participants consented to a further examination. Compared to the school cohort of children born at term the low birthweight cohort showed significantly lower near and distance acuities and contrast sensitivity (p<0.001 for all uniocular and binocular measures). Retinopathy of prematurity (ROP) was a very poor predictor of outcome and multivariate analysis did not identify any key neonatal factors as predictors of long term visual outcome. CONCLUSIONS Low birthweight children have a small but statistically significant deficit in both visual acuity and contrast sensitivity. Low birth weight and ROP both impact on long term visual functions.
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O'Connor AR, Stephenson TJ, Johnson A, Wright SD, Tobin MJ, Ratib S, Fielder AR. A comparison of findings on parents' and teachers' questionnaires, and detailed ophthalmic and psychological assessments. Arch Dis Child 2004; 89:831-5. [PMID: 15321859 PMCID: PMC1763206 DOI: 10.1136/adc.2003.029470] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BACKGROUND Questionnaires are important tools used to gain information about health and level of function in different domains. AIMS AND METHODS To determine the degree of agreement between questionnaires, administered to parents and teachers, and ophthalmic and psychological examinations in a cohort of 309 low birth weight children (<1701 g) at age 10-13 years. RESULTS A total of 90.9% of cases showed agreement between the question on distance vision and clinical assessment, and agreement for the near vision question was 83%. However, the correlation on an individual basis was only fair (kappa = 0.46, distance vision) to poor (kappa = 0.2, near vision). The overall agreement for the questions on cognitive ability was better than the correlation, whereas the questions on reading and mathematical ability showed low agreement and low correlation. CONCLUSION Questionnaire assessment of vision and cognitive ability is more suitable for studying the outcome of a large population than for identifying deficits in individuals.
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Tobin MJ, Chesters MA, Chalmers JM, Rutten FJM, Fisher SE, Symonds IM, Hitchcock A, Allibone R, Dias-Gunasekara S. Infrared microscopy of epithelial cancer cells in whole tissues and in tissue culture, using synchrotron radiation. Faraday Discuss 2004; 126:27-39; discussion 77-92. [PMID: 14992398 DOI: 10.1039/b306689d] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Oral epithelial tumour tissue, and cultured cervical epithelial carcinoma cells have been studied using synchrotron infrared microspectroscopy. Mid infrared absorption spectra collected at cellular spatial resolution from within oral tumours were found to be sufficiently distinct, when analysed by principal component analysis, to distinguish between three different cell types within the tumour. The resulting data were sufficiently robust to allow correct classification of spectra from cells within subsequent tissue samples. These results go some way to demonstrate the potential of infrared spectroscopy as a tool in the post-operative screening of oral cancer patients by the examination of exfoliated epithelial cells. To gain a better understanding of the inherent variability in the infrared spectra of such epithelial cells, we have studied A431 carcinoma cells under the stimulus of the growth-stimulating hormone EGF. We have detected key changes in the infrared spectrum that relate to the activation of the growth factor signalling mechanism.
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Tobin MJ. Concluding Remarks. Faraday Discuss 2004. [DOI: 10.1039/b313379f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Atkinson SDM, Almond MJ, Hibble SJ, Hollins P, Jenkins SL, Tobin MJ, Wiltshire KS. An in situ time-dependent study of the photodimerisation of chloro-derivatives of trans-cinnamic acid using infrared microspectroscopy with a synchrotron radiation source. Phys Chem Chem Phys 2004. [DOI: 10.1039/b313306k] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Sarcina M, Murata N, Tobin MJ, Mullineaux CW. Lipid diffusion in the thylakoid membranes of the cyanobacterium Synechococcus sp.: effect of fatty acid desaturation. FEBS Lett 2003; 553:295-8. [PMID: 14572639 DOI: 10.1016/s0014-5793(03)01031-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Thylakoid membranes are crucial to photosynthesis in cyanobacteria and plants. In cyanobacteria, genetic modification of membrane lipid composition strongly influences cold tolerance and susceptibility to photoinhibition. We have used fluorescence recovery after photobleaching to measure the diffusion of a lipid-soluble fluorescent marker in cells of the cyanobacterium Synechococcus sp. PCC 7942. We have compared the wild-type strain with a transformant with an increased level of fatty acid unsaturation. The transformant showed a six-fold increase in the diffusion coefficient for the fluorescent marker at growth temperature. This is the first direct measurement of lipid diffusion in a photosynthetic membrane.
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Cattapan SE, Laghi F, Tobin MJ. Can diaphragmatic contractility be assessed by airway twitch pressure in mechanically ventilated patients? Thorax 2003; 58:58-62. [PMID: 12511723 PMCID: PMC1746444 DOI: 10.1136/thorax.58.1.58] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
BACKGROUND In critically ill patients inspiratory muscle function may be assessed by measurements of maximal inspiratory airway pressure and the response of twitch transdiaphragmatic pressure (Pdi tw) to bilateral phrenic nerve stimulation. The first is limited by its total dependence on patient cooperation. Although the second approach is independent of patient volition, it is impractical because it requires oesophageal and gastric balloons. Because airway pressure is easily and non-invasively recorded in patients with artificial airways, we hypothesised that twitch airway pressure (Paw tw) reliably predicts Pdi tw and twitch oesophageal pressure (Poes tw) in mechanically ventilated patients. METHODS Thirteen mechanically ventilated patients recovering from an episode of acute respiratory failure received phrenic nerve stimulation at end exhalation. The rapid occlusion technique was used to record respiratory system mechanics. RESULTS Stimulations were well tolerated. Mean (SE) Paw tw at end exhalation was -8.2 (1.2) cm H(2)O and Poes tw and Pdi tw were -7.3 (1.1) and 10.4 (1.8) cm H(2)O, respectively. Stimulations produced a good correlation between Paw tw and Pdi tw (p<0.001), although the limits of agreement were wide. The results were similar for Poes tw. No relationship was found between the Paw tw/Poes tw ratio and respiratory system compliance or airway resistance. Paw tw reproducibility was excellent (mean coefficient of variation 6%, range 3-9%). CONCLUSIONS Despite a good correlation between Paw tw and Poes tw, Paw tw did not reliably predict Poes tw or Pdi tw in mechanically ventilated patients. Nevertheless, the excellent reproducibility of Paw tw suggests that it may be a useful means of monitoring inspiratory muscle contractility in the routine care of mechanically ventilated patients.
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Martin-Fernandez M, Clarke DT, Tobin MJ, Jones SV, Jones GR. Preformed oligomeric epidermal growth factor receptors undergo an ectodomain structure change during signaling. Biophys J 2002; 82:2415-27. [PMID: 11964230 PMCID: PMC1302032 DOI: 10.1016/s0006-3495(02)75585-9] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Fluorescence resonance energy transfer (FRET) was used to reveal aspects of the mechanism of signal transduction by epidermal growth factor receptors (EGFR). The superpositions of epidermal growth factor (EGF), transforming growth factor-alpha (TGFalpha) and an antibody fragment (29.1) to the carbohydrate extremity of the receptor's ectodomain as measured by FRET, show that 14% of EGFRs in A431 cells are oligomerized before growth factor binding. After binding growth factor and signaling, these oligomers dissociate before releasing growth factor. Time courses of the FRET-derived distances between constitutively oligomerized EGFRs during signal transduction show a transient structural change in the extracellular domain, which occurs simultaneously with the production of intracellular Ca2+ signals. The FRET measurements also show a slow increase in oligomerization of EGFR monomers after growth factor binding. The structural change found in the extracellular domain of oligomeric EGFRs is similar to that shown by others for EPO, Neu, Fas, and tumor necrosis factor receptors, and may therefore be a common property of the transduction of the receptor-mediated signals.
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Burrow SM, Phoenix DA, Wainwright M, Tobin MJ. Intracellular localisation studies of doxorubicin and Victoria Blue BO in EMT6-S and EMT6-R cells using confocal microscopy. Cytotechnology 2002; 39:15-25. [PMID: 19003300 PMCID: PMC3449804 DOI: 10.1023/a:1022435829894] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The subcellular localisation of doxorubicin and Victoria Blue BO (VBBO) in a murine mammary tumour cell line EMT6-S, and the resistant sub-lineEMT6-R was studied, using confocal microscopy, in order to investigate their sites of action. In cells treated with doxorubicin (10 mu M) for 90 min, the pattern of intracellular drug distribution differed between the two cell lines. Doxorubicin was found to localise mainly in the nucleus of the sensitive cell line, whereas weak fluorescence was observed in the cytoplasm of the resistant cells, in a punctuate pattern, with no nuclear involvement. The drug also appeared to be effluxed more rapidly by the resistant cell line. The accumulation of doxorubicin at various time intervals over 1h in EMT6-S cells showed that the drug clearly interacted with both the plasma membrane and the nucleus. In contrast to doxorubicin, the intracellular distribution of VBBO in both EMT6-S and EMT6-R was similar, VBBO was clearly localised throughout the cytoplasm, in a punctuate pattern, which may be consistent with the widespread distribution of mitochondria. A more apical pattern of accumulation was noted in the EMT6-R cell line. No interaction with the plasma membrane was evident. These results indicate that the main modes of action for the two drugs differ markedly, suggesting involvement of both the membrane and the nucleus in the case of doxorubicin, but mitochondrial involvement for VBBO.
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Tobin MJ, Matters B, Chen L, Smith R, Stuhlmiller C. Improving clinical management for consumers with co-existing mental health and substance use disorders: an integrated approach. AUST HEALTH REV 2002; 24:118-24. [PMID: 11668911 DOI: 10.1071/ah010118] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Using Quality Improvement project methodology, complex organisational and clinical practice change was brought about to improve services for people with co-existing mental health and alcohol and drug misuse. The project describes local uptake and adaptation of national and state policy to achieve change that is sustainable within existing resources. Emphasis on engagement of staff and consumers and carers throughout the change was an essential component. The project has implications for the introduction of changes in response to other national policy directives.
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Sarcina M, Tobin MJ, Mullineaux CW. Diffusion of phycobilisomes on the thylakoid membranes of the cyanobacterium Synechococcus 7942. Effects of phycobilisome size, temperature, and membrane lipid composition. J Biol Chem 2001; 276:46830-4. [PMID: 11590154 DOI: 10.1074/jbc.m107111200] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A variant of fluorescence recovery after photobleaching allows us to observe the diffusion of photosynthetic complexes in cyanobacterial thylakoid membranes in vivo. The unicellular cyanobacterium Synechococcus sp. PCC7942 is a wonderful model organism for fluorescence recovery after photobleaching, because it has a favorable membrane geometry and is well characterized and transformable. In Synechococcus 7942 (as in other cyanobacteria) we find that photosystem II is immobile, but phycobilisomes diffuse rapidly on the membrane surface. The diffusion coefficient is 3 x 10(-10) cm(2) s(-1) at 30 degrees C. This shows that the association of phycobilisomes with reaction centers is dynamic; there are no stable phycobilisome-reaction center complexes in vivo. We report the effects of mutations that change the phycobilisome size and membrane lipid composition. 1) In a mutant with no phycobilisome rods, the phycobilisomes remain mobile with a slightly faster diffusion coefficient. This confirms that the diffusion we observe is of intact phycobilisomes rather than detached rod elements. The faster diffusion coefficient in the mutant indicates that the rate of diffusion is partly determined by the phycobilisome size. 2) The temperature dependence of the phycobilisome diffusion coefficient indicates that the phycobilisomes have no integral membrane domain. It is likely that association with the membrane is mediated by multiple weak interactions with lipid head groups. 3) Changing the lipid composition of the thylakoid membrane has a dramatic effect on phycobilisome mobility. The results cannot be explained in terms of changes in the fluidity of the membrane; they suggest that lipids play a role in controlling phycobilisome-reaction center interaction.
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Tobin MJ. Tuberculosis, lung infections, and interstitial lung disease in AJRCCM 2000. Am J Respir Crit Care Med 2001; 164:1774-88. [PMID: 11734425 DOI: 10.1164/ajrccm.164.10.2108127] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
MESH Headings
- AIDS-Related Opportunistic Infections/diagnosis
- AIDS-Related Opportunistic Infections/epidemiology
- AIDS-Related Opportunistic Infections/immunology
- AIDS-Related Opportunistic Infections/therapy
- Animals
- Biomarkers/analysis
- Bronchiectasis/diagnosis
- Bronchiectasis/therapy
- Critical Care/methods
- Critical Care/standards
- Critical Care/trends
- Disease Models, Animal
- HIV Infections/complications
- HIV Infections/diagnosis
- HIV Infections/epidemiology
- HIV Infections/immunology
- HIV Infections/therapy
- Humans
- Hypertension, Pulmonary/diagnosis
- Hypertension, Pulmonary/therapy
- Immunocompromised Host
- Infections/diagnosis
- Infections/therapy
- Lung Diseases/diagnosis
- Lung Diseases/therapy
- Lung Diseases, Interstitial/diagnosis
- Lung Diseases, Interstitial/therapy
- Mass Screening/methods
- Molecular Biology
- Periodicals as Topic
- Risk Factors
- Sarcoidosis/diagnosis
- Sarcoidosis/genetics
- Sarcoidosis/therapy
- Scleroderma, Systemic/diagnosis
- Scleroderma, Systemic/therapy
- Tuberculosis, Pulmonary/diagnosis
- Tuberculosis, Pulmonary/epidemiology
- Tuberculosis, Pulmonary/therapy
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Tobin MJ. Chronic obstructive pulmonary disease, pollution, pulmonary vascular disease, transplantation, pleural disease, and lung cancer in AJRCCM 2000. Am J Respir Crit Care Med 2001; 164:1789-804. [PMID: 11734426 DOI: 10.1164/ajrccm.164.10.2108126] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Tobin MJ. Pediatrics, surfactant, and cystic fibrosis in AJRCCM 2000. Am J Respir Crit Care Med 2001; 164:1581-94. [PMID: 11719294 DOI: 10.1164/ajrccm.164.9.2108125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Tobin MJ. Sleep-disordered breathing, control of breathing, respiratory muscles, pulmonary function testing, nitric oxide, and bronchoscopy in AJRCCM 2000. Am J Respir Crit Care Med 2001; 164:1362-75. [PMID: 11704580 DOI: 10.1164/ajrccm.164.8.2108124] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Tobin MJ, Clarke AR, Buss R, Einfeld SL, Beard J, Dudley M, Knowles M, Dietrich U. From efficacy to effectiveness: managing organisational change to improve health services for young people with deliberate self harm behaviour. AUST HEALTH REV 2001; 24:143-51. [PMID: 11496456 DOI: 10.1071/ah010143] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Repeat Deliberate Self Harm is a recognised risk factor for completed suicide and therefore reduction by effective health service response represents a valid contribution to suicide prevention. However, only a small fraction of people with deliberate self harm presentations to general health settings actually reach specialist mental health follow-up appointments. Therefore, even if responses at that point are known to be effective they do not make a significant contribution to reducing repeat self-harm overall. We describe health system organisational change strategies to improve health service engagement for the target group, and present data demonstrating the effectiveness of these strategies.
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Preas HL, Jubran A, Vandivier RW, Reda D, Godin PJ, Banks SM, Tobin MJ, Suffredini AF. Effect of endotoxin on ventilation and breath variability: role of cyclooxygenase pathway. Am J Respir Crit Care Med 2001; 164:620-6. [PMID: 11520726 DOI: 10.1164/ajrccm.164.4.2003031] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
To evaluate the effects of endotoxemia on respiratory controller function, 12 subjects were randomized to receive endotoxin or saline; six also received ibuprofen, a cyclooxygenase inhibitor, and six received placebo. Administration of endotoxin produced fever, increased respiratory frequency, decreased inspiratory time, and widened alveolar-arterial oxygen tension gradient (all p < or = 0.001); these responses were blocked by ibuprofen. Independent of ibuprofen, endotoxin produced dyspnea, and it increased fractional inspiratory time, minute ventilation, and mean inspiratory flow (all p < or = 0.025). Endotoxin altered the autocorrelative behavior of respiratory frequency by increasing its autocorrelation coefficient at a lag of one breath, the number of breath lags with significant serial correlations, and its correlated fraction (all p < 0.05); these responses were blocked by ibuprofen. Changes in correlated behavior of respiratory frequency were related to changes in arterial carbon dioxide tension (r = 0.86; p < 0.03). Endotoxin decreased the oscillatory fraction of inspiratory time in both the placebo (p < 0.05) and ibuprofen groups (p = 0.06). In conclusion, endotoxin produced increases in respiratory motor output and dyspnea independent of fever and symptoms, and it curtailed the freedom to vary respiratory timing-a response that appears to be mediated by the cyclooxygenase pathway.
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Campbell TF, Needleman HL, Riess JA, Tobin MJ. Bone lead levels and language processing performance. Dev Neuropsychol 2001; 18:171-86. [PMID: 11280963 DOI: 10.1207/s15326942dn1802_2] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
The relation between bone lead absorption and language processing abilities in 156 randomly selected 11- to 14-year-old boys who were asymptomatic for lead toxicity is examined. Tibial lead concentrations were measured by X-ray fluorescence spectroscopy. The language processing outcome variables consisted of the least and most difficult subtests from the Nonword Repetition Task, Competing Language Processing Task, and the Revised Token Test. Participants were classified by quartiles according to bone lead concentrations, and analysis of variance and analysis of covariance measured the impact on language processing scores. Results showed that children in the highest bone lead quartile displayed decreased language processing performance on the most difficult language processing tasks but not on the easier tasks.
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Topeli A, Laghi F, Tobin MJ. The voluntary drive to breathe is not decreased in hypercapnic patients with severe COPD. Eur Respir J 2001; 18:53-60. [PMID: 11510806 DOI: 10.1183/09031936.01.00014101] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
How do the respiratory centres of patients with chronic obstructive pulmonary disease (COPD) and hypercapnia respond to acute increases in inspiratory load? A depressed respiratory motor output has long been postulated, but studies on this issue have yielded inconsistent results, partly due to limitations of investigative techniques. Many of these limitations can be overcome by the twitch interpolation technique, which is capable of accurately quantifying the degree of diaphragmatic activation, termed the voluntary drive to breathe. The hypothesis that patients with COPD and hypercapnia compensate for an acute increase in mechanical load on the inspiratory muscles with a lower voluntary drive to breathe than is the case with normocapnic patients was tested. Measurements were obtained in 15 patients with COPD, six of whom displayed hypercapnia and nine normocapnia. The maximum degree of diaphragmatic activation, expressed as a voluntary activation index (mean +/- SEM), was higher in hypercapnic than in normocapnic patients (98.7 +/- 0.7 versus 94.5 +/- 0.9% (p = 0.006)), as was the mean value (94.5 +/- 0.7 versus 88.5 +/- 1.9% (p = 0.01)). Within-patient values of the index were also less variable in the hypercapnic patients (coefficients of variation, 3.4 +/- 0.3 versus 6.1 +/- 0.9%, p = 0.01). Multiple regression analysis revealed the ratio of dynamic elastance to maximum transdiaphragmatic pressure, an index of inspiratory muscle loading, and pH as the only variables that correlated with maximum voluntary activation index (r2 = 0.69, p = 0.02 for each variable). Contrary to the hypothesis, it was concluded that voluntary activation of the diaphragm was greater and less variable in hypercapnic patients than normocapnic patients with severe chronic obstructive pulmonary disease during an acute increase in inspiratory mechanical load. Whether greater diaphragmatic recruitment during episodes of a severe exacerbation of chronic obstructive pulmonary disease provides a survival advantage for hypercapnic patients with chronic obstructive pulmonary disease remains to be determined.
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Laghi F, Segal J, Choe WK, Tobin MJ. Effect of Imposed Inflation Time on Respiratory Frequency and Hyperinflation in Patients with Chronic Obstructive Pulmonary Disease. Am J Respir Crit Care Med 2001; 163:1365-70. [PMID: 11371402 DOI: 10.1164/ajrccm.163.6.2001123] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Decreases in ventilator inflation time (TI,vent) can cause tachypnea, probably as a response to lung inflation. The response may differ in chronic obstructive pulmonary disease (COPD) because time-constant inhomogeneities could foster overdistention of some lung units during early inflation, causing neural inspiratory time to be shorter than in healthy subjects. We tested the hypothesis that a decrease in TI,vent causes tachypnea, prolongation of exhalation, and a decrease in intrinsic positive end-expiratory pressure (PEEP(i)). Ten patients with stable COPD received assist-control ventilation through a mouthpiece. Decreases in TI,vent, achieved through increases in flow from 30 to 90 L/min, increased frequency, from 16.1 +/- 1.0 (SE) to 20.8 +/- 1.5 breaths/min (p < 0.001), time for exhalation, from 2.1 +/- 0.2 to 2.3 +/- 0.2 s (p < 0.025), and decreased PEEP(i), from 7.0 +/- 1.3 to 6.4 +/- 1.1 cm H(2)O (p < 0.01). Decreases in TI,vent, achieved by decreasing inspiratory pause from 2 to 0 s, increased frequency, from 12.9 +/- 0.8 to 18.1 +/- 1.6 breaths/min (p < 0.001), time for exhalation, from 2.0 +/- 0.2 to 2.6 +/- 0.3 s (p < 0.001), and decreased PEEP(i), from 6.4 +/- 1.1 to 5.5 +/- 0.9 cm H(2)O (p < 0.01). In both experiments, decreases in TI,vent reduced inspiratory effort (p < 0.01). In conclusion, strategies to reduce TI,vent in patients with COPD caused tachypnea, yet prolonged the time for exhalation with consequent decrease in PEEP(i).
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MESH Headings
- Aged
- Airway Resistance
- Blood Gas Analysis
- Forced Expiratory Volume
- Functional Residual Capacity
- Humans
- Lung Diseases, Obstructive/classification
- Lung Diseases, Obstructive/complications
- Lung Diseases, Obstructive/metabolism
- Lung Diseases, Obstructive/physiopathology
- Lung Diseases, Obstructive/therapy
- Male
- Positive-Pressure Respiration, Intrinsic/etiology
- Respiration, Artificial/adverse effects
- Respiration, Artificial/instrumentation
- Respiration, Artificial/methods
- Respiratory Mechanics
- Severity of Illness Index
- Signal Processing, Computer-Assisted
- Tidal Volume
- Time Factors
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