Hypercapnic and hypoxic ventilatory responses during growth.

Abstract

Cross-sectional studies on hypercapnic and hypoxic ventilatory chemosensitivities were performed in 71 children ranging in age from 7 to 18 yrs. The subjects were classified into 6 successive 2-year age groups. CO2 ventilatory response was measured by rebreathing 5 % CO2 in Oz, a slight modification of the method originally proposed by Read. The results were evaluated when the C02-ventilation feedback control system was supposed to have attained the open-loop condition. Hypoxic ventilatory response was measured by the isocapnic progressive hypoxia test. To obtain good reproducibility in the ventilatory response, end-tidal P~oz was maintained at 5 mmHg higher than the resting condition throughout the test. Normalized ventilatory responses to CO2 by body surface area (S/BSA) progressively decreased from the 7-8 through the 11-12 yr groups, and then tended to decrease further in a more gradual manner with increasing age. This trend was very similar to the normalized CO2 output (V"oz/BSA), but did not parallel so closely the normalized Oz intake (Voz/BSA). When ventilatory and metabolic parameters were normalized by body weight (BW), or the lean body mass (LBM), qualitatively similar relationships between CO2 sensitivities and metabolic parameters were also obtained. Contrary to the hypercapnic response, hypoxic ventilatory chemosensitivities were not significantly different among the 6 different age groups. We concluded that normalized hypercapnic chemosensitivity decreased during growth and corresponded well with decreased CO2 output per unit body mass.Key words : hypercapnic ventialtory response, hypoxic ventilatory response, body weight, body surface area, lean body mass.

Short‐term cardiorespiratory adaptation to high altitude in children compared with adults

“…Results range from an increased ventilatory response to hypoxia in 5–17‐year‐old children compared with adults (Marcus et al., ) to no difference among children and adolescents from 7–18 years of age (Honda et al., ). One reason for the different results may be the different scaling factors used ranging from body weight to lean body mass, body surface area or pulmonary function (Honda et al., ; Marcus et al., ). As HVR is a ventilatory control parameter expressing V E by degree of hypoxia, it makes sense to use vital capacity as scaling factor, which adjusts for the different lung volumes that can potentially be utilized to reach V E (Rowland, ).…”

“…HVR in children even at LA has not been widely examined and results are controversial. Results range from an increased ventilatory response to hypoxia in 5–17‐year‐old children compared with adults (Marcus et al., ) to no difference among children and adolescents from 7–18 years of age (Honda et al., ). One reason for the different results may be the different scaling factors used ranging from body weight to lean body mass, body surface area or pulmonary function (Honda et al., ; Marcus et al., ).…”

Cerebrovascular and ventilatory responses to acute normobaric hypoxia in girls and women

“…Evidence that the ventilatory response to hypoxia is dependent on age is mixed. Using an isocapnic progressive hypoxic technique, no differences in the hypoxic ventilatory response was noted from 7 to 18 years of age (Honda et al 1986). In contrast, using the same isocapnic rebreathe technique, Marcus et al (1994) reported a significantly increased hypoxic ventilatory response in children compared to adults; however, the relationship with age was weak (r = 0.34).…”

“…Using an isocapnic progressive hypoxic technique, no differences in the hypoxic ventilatory response was noted from 7 to 18 years of age (Honda et al. ). In contrast, using the same isocapnic rebreathe technique, Marcus et al.…”

Ventilatory drive and the apnea-hypopnea index in six-to-twelve year old children

“…Although Marcus et al [5] corrected their subject's ventilatory responses for body surface area, the coefficient of variation of the corrected ventilatory response to hypoxia was still 50%. Similarly, Honda et al [6] reported that coefficient of variation values for body surface area-corrected hypoxic ventilatory responses ranged from 63–81% in children aged 7–12 years (see their Table 1). These data suggest strongly that body surface area may not adequately correct the ventilatory response for body size in young children.…”