Comparison of computerized methods for detecting the ventilatory thresholds

Abstract

The aim of this study was to compare computerized automatic methods to detect the ventilatory threshold (VT). Thirty apparently healthy and physically active volunteers [22.5 (6.5) years; 1.72 (0.08) m; 71.9 (8.5) kg] were submitted to a progressive and maximal cycle exercise. The gas exchange was monitored breath-by-breath with a fast gas analyser. The VT and respiratory compensation (RC) were automatically detected based on the respiratory exchange ratio, the ventilatory equivalent for O2 and the ventilatory equivalent for CO2, pulmonary ventilation, end-tidal PO2 and PCO2, and v-slope. In addition, VT and RC were also determined independently by visual inspection by two experienced investigators, and the results were compared with those of the automatic procedures. The automatic VT averaged 77% of the maximal VO2 and the RC 88%. The agreement between the experienced observers was very close [mean difference: 44.4 (16.1) ml, r = 0.94, not significant]. Data were expressed as the mean value together with the standard deviation in each case. The automatic and visual inspection procedures did not present significant differences, resulting in 29.6 (29.6) ml with a reliability of r = 0.86. All methods were significantly correlated for VT and RC (r = 0.93 on average, P < 0.01). ANOVA did not show differences between either the VT methods (P = 0.131) or the RC methods (P = 0.41). In conclusion, the present study has compared several simultaneous breath-by-breath ergospirometric methods that are used to describe the anaerobic threshold, showing high confidence when compared to visual inspection. No statistical differences were found between the VT and RC techniques for physically active subjects indicating that these methods may be equally effectively employed.

Precisão da medida do limiar anaeróbio por meio do calorímetro portátil

“…Kelly 36 observed that the results obtained by the original mathematical method of Beaver et al 9 presented a major estimate standard error, when compared to MM RSS . Santos et al 35 found for this method, percentage indices of 83% of VO 2max . In our study, we observed high intensities of AT 31 by means of MM slope , indicating a possible method inaccuracy.…”

Assessment of Functional Capacity in Clinical and Research Settings

“…The 3 most common definitions of the VT are the following: (1) the point at which a systematic increase in the ventilatory equivalent for oxygen (V E/V O 2 ) occurs without an increase in the ventilatory equivalent for carbon dioxide (V E/V CO 2 ), (2) the point at which a systematic rise in end-tidal oxygen pressure (P ET O 2 ) occurs without a decrease in the end-tidal carbon dioxide pressure (P ET CO 2 ), and (3) the departure of V CO 2 from a line of identity drawn through a plot of V CO 2 versus V O, often called the V-slope method. 18 When determined visually, these methods on average result in VT values at a similar percentage of V O 2max . 19 Although modern equipment that measures metabolic parameters usually quantifies this point automatically using one of several published or empirical algorithms, it should be validated visually by an experienced reviewer.…”

Método alternativo de determinação de limiar anaeróbio em remadores

“…Verificamos uma correlação significativa entre os métodos Dmáx e R (r =0,62 p< 0,05). Resultados semelhantes foram encontrados em outros estudos, nos quais não existiam diferenças significativas entre a determinação de limiar anaeróbio por R e por outros métodos ventilatórios e lactacidêmicos 5,[14][15][16][17]23 . Estes resultados em conjunto demonstram que a determinação de limiar anaeróbio pela R pode ser utilizada como um parâmetro independente para a detecção do limiar anaeróbio.…”

“…Em razão deste acoplamento da respiração com o gesto técnico, torna-se praticamente impossível a detecção dos limiares ventilatórios nesta população 20,30 . Além disso, partindo do principio de que a mensuração do lactato é uma técnica invasiva e de alto custo financeiro, alguns autores sugerem a utilização da R como um método alternativo não-invasivo, reproduzível, de fácil aplicação e com menor custo de manutenção da técnica para a detecção do limiar anaeróbio 5,7,13,15,17,[21][22][23] . A proposta destes autores é que o limiar anaeróbio seja identificado pela R a partir do ponto de aumento desproporcional ou excedente de um valor pré-determinado.…”

“…A proposta destes autores é que o limiar anaeróbio seja identificado pela R a partir do ponto de aumento desproporcional ou excedente de um valor pré-determinado. Valores fixos de 0,95 e 1 têm sido sugeridos 5,17,19,[21][22][23] , no entanto, ainda não existe um consenso sobre o valor da R a ser aplicado. Em nosso estudo, encontramos um valor de R de 0,99 correspondente ao limiar anaeróbio determinado por Dmáx, indo ao encontro de outros estudos 5,15,21,22 .…”