Arterial Blood Gases in Normal Subjects at 2240 Meters Above Sea Level: Impact of Age, Gender, and Body Mass Index

Background

The values of arterial blood gases (ABG) change with altitude above sea level; empirical verification is essential because ventilatory acclimatization varies with ethnicity and a population's adaptation.

Objective

The aim of the study was to describe ABG in a healthy population residing at 2,240 meters above sea level, to identify the mean level of alveolar ventilation (PaCO₂), and to know whether a progressive increase in PaCO₂ occurs with age and the impact of increasing body mass index (BMI).

Methods

We conducted a cross-sectional study in a referral center for respiratory diseases in Mexico City. Associations among variables with correlation coefficient and regression models of PaO₂, SaO₂, and P(A-a)O₂ as dependent variables as a function of age, BMI, minute ventilation, or breathing frequency were explored.

Results

Two hundred and seventeen healthy subjects were evaluated with a mean age of 40 ± 15 years, mean of the PaO₂ was 71 ± 6 mmHg, SaO₂ 94% ± 1.6%, PaCO₂ 30.2 ± 3.4 mmHg, HCO₃ 20 ± 2 mmol/L, BE-2.9 ± 1.9 mmol/L, and the value of pH was 7.43 ± 0.02. In a linear regression, the main results were PaO₂ = 77.5-0.16*age (p < 0.0001) and with aging P(A-a)O₂ tended to increase 0.12 mmHg/year. PaCO₂ in women increased with age by 0.075 mmHg/year (p = 0.0012, PaCO₂ =26.3 + 0.075*age). SaO₂ and PaO₂ decreased significantly in women with higher BMI 0.14% and 0.52 mmHg per kg/m², (p = 0.004 and 0.002 respectively).

Conclusion

Mean PaCO₂ was 30.7 mmHg, implying a mean alveolar ventilation of around 30% above that at sea level.

Gas Exchange Impairment During COVID-19 Recovery

BACKGROUND

Persistent impairment of pulmonary function and exercise capacity has been known to last for months or even years in the survivors who recovered from other coronavirus pneumonia. Some reports showed that subjects with coronavirus disease 2019 pneumonia after being discharged could have several sequelae, but there are few studies on gas exchange and exercise capacity complications in these subjects.

AIMS

To describe residual gas exchange abnormalities during recovery from coronavirus disease 2019 pneumonia.

METHODS

In an observational study, ∼90 d after onset of disease, we scheduled almost 200 subjects for an out-patient visit with pulmonary function testing and computed tomography of the lungs. Lung mechanics by using body plethysmography, gas exchange with diffusing lung capacity for carbon monoxide determined by the single-breath technique (D_LCOsb) and diffusing lung capacity for nitric oxide determined by the single-breath technique (D_LNOsb), and exercise ability by using the 6-min walk test (6MWT) were measured in the subjects. The results were compared between those who required invasive mechanical ventilation and those who did not.

RESULTS

A total of 171 subjects were included, the majority (96%) had signs of residual pneumonia (such as an excess of high attenuation areas) on computed tomography of the lungs. The D_LCOSB results were below the lower limit of the normal range in 29.2% of the subjects; during the 6MWT, 67% experienced oxygen desaturation ([Formula: see text]) > 4%; and, in 81 (47%), the dropped below 88%. Subjects who required invasive mechanical ventilation (49.7%) were more likely to have lower lung volumes, more gas exchange abnormality, less exercise capacity and more radiologic abnormality.

CONCLUSIONS

Subjects who recovered from severe COVID-19 pneumonia continued to have abnormal lung function and abnormal radiologic findings.

Functional Respiratory Evaluation in the COVID-19 Era: The Role of Pulmonary Function Test Laboratories

The pandemic character of coronavirus disease-19 (COVID-19) requires strategy changes designed to guarantee the safety of patients and health-care professionals. We are greatly concerned by the limitations in the operation of pulmonary function test (PFT) laboratories, since there is a high risk of disease progression in patients with chronic pulmonary diseases, and we are now faced by the influx of a new group of individuals in the recovery phase of post-COVID-19-syndrome that requires evaluation and follow-up of their respiratory function. To reestablish the operation of PFT laboratories limiting the risk of cross-contamination, we herein present the consensus reached by a group of experts in respiratory physiology, most of whom work in PFT laboratories in several Latin American countries, on the applicable recommendations for severe acute respiratory syndrome coronavirus 2 pneumonia survivors when undergoing PFT. We present the safety and hygiene measures that must be adopted in laboratories or centers where PFT is conducted in adults and/or children. These recommendations answer the following questions: which PFT is most recommended in subjects that have recovered from COVID-19; what quality control and safety measures should PFT laboratories implement during this pandemic? And how should we approach non-COVID-19 patients requiring PFT?

Quality of spirometry in 5-to-8-year-old children

INTRODUCTION

Although spirometry quality standards for children were proposed by American Thoracic Society/European Respiratory Society (ATS/ERS) in 2007, there is limited information on the percentage of children that fulfill these criteria during routine clinical testing, especially among 5-to-8-year-olds.

AIMS OF THE STUDY

to report the percentage of children that met the current 2007 ATS/ERS quality criteria; explore factors potentially associated with poor quality spirometry; and ascertain the repeatability of forced expiratory volume at 0.5 sec (FEV0.5 ), and at 1 sec (FEV1 ), as well as forced vital capacity (FVC).

METHODS

We evaluated the quality of spirometries without bronchodilator use performed at our laboratory in 2008 by 5-to-8-year-old children. FEV1 , FEV0.5 , FVC, back-extrapolated volume (BEV), forced expiratory time (FET), number of acceptable maneuvers, and repeatability, were computed and the percentage of tests that met the quality criteria standards was calculated. Based on our results, we propose a quality scoring system for spirometry for children that grades on a scale from A-to-F.

RESULTS

Three hundred seventy-six spirometries were reviewed. Mean age was 6.7 years; (53% males); 68% fulfilled the 2005 and 2007 ATS/ERS quality standards; >90% reached a repeatability ≤150 and ≤100 ml, or 10%, in FVC or FEV1 ; 87.2% reached FET ≥3 sec; 88% had a BEV ≤80 ml. The 90 percentile repeatability was 120 ml for FVC and FEV1 . Quality improved with age.

CONCLUSIONS

Our results support the proposal that a FET ≥3 sec, a BEV ≤80 ml, and repeatability in FEV1 and FVC ≤100 ml, or 10%, be taken into account as elements in quality control for spirometry in children.