Using Underwater Pulse Oximetry in Freediving to Extreme Depths to Study Risk of Hypoxic Blackout and Diving Response Phases

Deep freediving exposes humans to hypoxia and dramatic changes in pressure. The effect of depth on gas exchange may enhance risk of hypoxic blackout (BO) during the last part of the ascent. Our aim was to investigate arterial oxygen saturation (SpO2) and heart rate (HR) in shallow and deep freedives, central variables, which have rarely been studied underwater in deep freediving. Four male elite competitive freedivers volunteered to wear a newly developed underwater pulse oximeter for continuous monitoring of SpO2 and HR during self-initiated training in the sea. Two probes were placed on the temples, connected to a recording unit on the back of the freediver. Divers performed one “shallow” and one “deep” constant weight dive with fins. Plethysmograms were recorded at 30 Hz, and SpO2 and HR were extracted. Mean ± SD depth of shallow dives was 19 ± 3 m, and 73 ± 12 m for deep dives. Duration was 82 ± 36 s in shallow and 150 ± 27 s in deep dives. All divers desaturated more during deeper dives (nadir 55 ± 10%) compared to shallow dives (nadir 80 ± 22%) with a lowest SpO2 of 44% in one deep dive. HR showed a “diving response,” with similar lowest HR of 42 bpm in shallow and deep dives; the lowest value (28 bpm) was observed in one shallow dive. HR increased before dives, followed by a decline, and upon resurfacing a peak after which HR normalized. During deep dives, HR was influenced by the level of exertion across different diving phases; after an initial drop, a second HR decline occurred during the passive “free fall” phase. The underwater pulse oximeter allowed successful SpO2 and HR monitoring in freedives to 82 m depth – deeper than ever recorded before. Divers’ enhanced desaturation during deep dives was likely related to increased exertion and extended duration, but the rapid extreme desaturation to below 50% near surfacing could result from the diminishing pressure, in line with the hypothesis that risk of hypoxic BO may increase during ascent. Recordings also indicated that the diving response is not powerful enough to fully override the exercise-induced tachycardia during active swimming. Pulse oximetry monitoring of essential variables underwater may be an important step to increase freediving safety.

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Pulse Oximetry: An Alternative Method for the Assessment of Oxygenation in Newborn Infants

PEDIATRICS ◽

10.1542/peds.79.4.524 ◽

1987 ◽

Vol 79 (4) ◽

pp. 524-528

Author(s):

Michael S. Jennis ◽

Joyce L. Peabody

Keyword(s):

Pulse Oximetry ◽

Pulse Oximeter ◽

Arterial Oxygen Saturation ◽

Newborn Infants ◽

Fetal Hemoglobin ◽

Arterial Oxygen ◽

Skin Injury ◽

Reliable Technique ◽

Arterial Blood

Continuous monitoring of oxygenation in sick newborns is vitally important. However, transcutaneous Po2 measurements have a number of limiations. Therefore, we report the use of the pulse oximeter for arterial oxygen saturation (Sao2) determination in 26 infants (birth weights 725 to 4,000 g, gestational ages 24 to 40 weeks, and postnatal ages one to 49 days). Fetal hemoglobin determinations were made on all infants and were repeated following transfusion. Sao2, readings from the pulse oximeter were compared with the Sao2 measured in vitro on simultaneously obtained arterial blood samples. The linear regression equation for 177 paired measurements was: y = 0.7x + 27.2; r = .9. However, the differences between measured Sao2 and the pulse oximeter Sao2 were significantly greater in samples with > 50% fetal hemoglobin when compared with samples with < 25% fetal hemoglobin (P < .001). The pulse oximeter was easy to use, recorded trends in oxygenation instantaneously, and was not associated with skin injury. We conclude that pulse oximetry is a reliable technique for the continuous, noninvasive monitoring of oxygenation in newborn infants.

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Accuracy and precision of pulse oximeter at different sensor locations in patients with heart failure

Multidisciplinary Respiratory Medicine ◽

10.4081/mrm.2021.742 ◽

2021 ◽

Vol 16 ◽

Author(s):

Alaa Thabet Hassan ◽

Soher Mostafa Ahmed ◽

Azza Salah AbdelHaffeez ◽

Sherif A.A. Mohamed

Keyword(s):

Heart Failure ◽

Oxygen Saturation ◽

Pulse Oximetry ◽

Pulse Oximeter ◽

Arterial Oxygen Saturation ◽

Arterial Oxygen ◽

St Segment Elevation ◽

Accuracy And Precision ◽

St Segment ◽

Patients With Heart Failure

Background: Despite its wide use in clinical practice, few studies had assessed the role of pulse oximetry in patients with heart failure. We aimed to evaluate the accuracy and precision of the pulse oximeter in patients with heart failure and to determine this accuracy at three different sensor locations.Methods: Comparison of pulse oximetry reading (SpO2) with arterial oxygen saturation (SaO2) was reported in 3 groups of patients with heart failure (HF); those with ejection fraction (EF) >40%, those with EF <40%, and those with acute HF (AHF) with ST and non-ST segment elevation acute myocardial infarction (STEMI and non-STEMI).Results: A total of 235 patients and 90 control subjects were enrolled. There were significant differences in O2 saturation between control and patients’ groups when O2 saturation is measured at the finger and toe, but not the ear probes; p=0.029, p=0.049, and 0.051, respectively. In HF with EF>40% and AHF with O2 saturations >90%, finger oximetry is the most accurate and reliable, while in HF with EF<40% and in patients with AHF with O2 saturations <90%, ear oximetry is the most accurate.Conclusion: Pulse oximetry is a reliable tool in assessing oxygen saturation in patients with heart failure of different severity. In HF with EF>40% and in AHF with O2 saturations >90%, finger oximetry is the most accurate and reliable, while in HF with EF<40% and in patients with AHF with O2 saturations <90%, ear oximetry is the most accurate. Further studies are warranted.

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Clinical evaluation of noninvasive monitoring of oxygen saturation in critically ill patients

American Journal of Critical Care ◽

10.4037/ajcc1998.7.5.370 ◽

1998 ◽

Vol 7 (5) ◽

pp. 370-373 ◽

Cited By ~ 18

Author(s):

P Smatlak ◽

AR Knebel

Keyword(s):

Cardiac Index ◽

Oxygen Saturation ◽

Pulse Oximetry ◽

Pulse Oximeter ◽

Arterial Oxygen Saturation ◽

Arterial Oxygen ◽

Pulmonary Capillary ◽

Margin Of Error ◽

Accuracy Of Measurement ◽

Clinical Conditions

OBJECTIVE: To examine the effect of abnormal cardiac index on the accuracy of measurement of oxygen saturation by pulse oximetry. METHODS: Forty-six patients (mean age, 49 years) in a 9-bed medical ICU were studied. Measurements of oxygen saturation obtained with pulse oximeters and with a functional cooximeter were collected at baseline and 4, 8, 16, 24, 32, 40, and 48 hours later. Hemodynamic and cardiopulmonary parameters were recorded. RESULTS: The Bland-Altman technique yielded upper and lower limits of agreement of 2.53% and -7.11%. Most (95.7%) of the differences between the measurements of oxygen saturation obtained with the 2 methods were within these limits, although some of these differences may be clinically unacceptable. The bias was -2.29%, and the precision was 2.41%. The clinical conditions associated with inaccurate tracking of saturation by pulse oximetry across the range of actual arterial oxygen saturation values were abnormal cardiac index, partial pressure of carbon dioxide, heart rate, and pulmonary capillary wedge pressure. CONCLUSIONS: In patients with abnormal cardiac index, the pulse oximeter measurements exceeded the actual oxygen saturation by up to 7%. Pending prospective studies, clinicians should be aware that when certain cardiopulmonary parameters are abnormal, the margin of error in measurements of oxygen saturation obtained with a pulse oximeter may be greater than when those parameters are normal.

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Hyperoxemia in Newborn Infants: Detection by Pulse Oximetry

PEDIATRICS ◽

10.1542/peds.84.2.226 ◽

1989 ◽

Vol 84 (2) ◽

pp. 226-230

Author(s):

Hans-Ulrich Bucher ◽

Sergio Fanconi ◽

Peter Baeckert ◽

Gabriel Duc

Keyword(s):

Pulse Oximetry ◽

Pulse Oximeter ◽

Arterial Oxygen Saturation ◽

Newborn Infants ◽

Arterial Oxygen Tension ◽

Arterial Oxygen ◽

Mechanically Ventilated ◽

Arterial Blood ◽

Transcutaneous Monitoring ◽

Alarm Limit

Pulse oximetry has been proposed as a non-invasive continuous method for transcutaneous monitoring of arterial oxygen saturation of hemoglobin (tcSO2) in the newborn infant. The reliability of this technique in detecting hyperoxemia is controversial, because small changes in saturation greater than 90% are associated with relatively large changes in arterial oxygen tension (PaO2). The purpose of this study was to assess the reliability of pulse oximetry using an alarm limit of 95% tcSO2 in detecting hyperoxemia (defined as PaO2 greater than 90 mm Hg) and to examine the effect of varying the alarm limit on reliability. Two types of pulse oximeter were studied alternately in 50 newborn infants who were mechanically ventilated with indwelling arterial lines. Three arterial blood samples were drawn from every infant during routine increase of inspired oxygen before intratracheal suction, and PaO2 was compared with tcSO2. The Nellcor N-100 pulse oximeter identified all 26 hyperoxemic instances correctly (sensitivity 100%) and alarmed falsely in 25 of 49 nonhyperoxemic instances (specificity 49%). The Ohmeda Biox 3700 pulse oximeter detected 13 of 35 hyperoxemic instances (sensitivity 37%) and alarmed falsely in 7 of 40 nonhyperoxemic instances (specificity 83%). The optimal alarm limit, defined as a sensitivity of 95% or more associated with maximal specificity, was determined for Nellcor N-100 at 96% tcSO2 (specificity 38%) and for Ohmeda Biox 3700 at 89% tcSO2 (specificity 52%). It was concluded that pulse oximeters can be highly sensitive in detecting hyperoxemia provided that type-specific alarm limits are set and a low specificity is accepted.

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Association Between Arterial Oxygen Saturation and Lung Ultrasound B-Lines After Competitive Deep Breath-Hold Diving

Frontiers in Physiology ◽

10.3389/fphys.2021.711798 ◽

2021 ◽

Vol 12 ◽

Author(s):

Alexander Patrician ◽

Frank Pernett ◽

Angelica Lodin-Sundström ◽

Erika Schagatay

Keyword(s):

Pulse Oximetry ◽

Pulmonary Edema ◽

Predictive Value ◽

Lung Ultrasound ◽

Arterial Oxygen Saturation ◽

Arterial Oxygen ◽

Breath Hold ◽

Lung Water ◽

Deep Dive ◽

B Lines

Breath-hold diving (freediving) is an underwater sport that is associated with elevated hydrostatic pressure, which has a compressive effect on the lungs that can lead to the development of pulmonary edema. Pulmonary edema reduces oxygen uptake and thereby the recovery from the hypoxia developed during freediving, and increases the risk of hypoxic syncope. We aimed to examine the efficacy of SpO2, via pulse-oximetry, as a tool to detect pulmonary edema by comparing it to lung ultrasound B-line measurements after deep diving. SpO2 and B-lines were collected in 40 freedivers participating in an international deep freediving competition. SpO2 was measured within 17 ± 6 min and lung B-lines using ultrasound within 44 ± 15 min after surfacing. A specific symptoms questionnaire was used during SpO2 measurements. We found a negative correlation between B-line score and minimum SpO2 (rs = −0.491; p = 0.002) and mean SpO2 (rs = −0.335; p = 0.046). B-line scores were positively correlated with depth (rs = 0.408; p = 0.013), confirming that extra-vascular lung water is increased with deeper dives. Compared to dives that were asymptomatic, symptomatic dives had a 27% greater B-line score, and both a lower mean and minimum SpO2 (all p < 0.05). Indeed, a minimum SpO2 ≤ 95% after a deep dive has a positive predictive value of 29% and a negative predictive value of 100% regarding symptoms. We concluded that elevated B-line scores are associated with reduced SpO2 after dives, suggesting that SpO2 via pulse oximetry could be a useful screening tool to detect increased extra-vascular lung water. The practical application is not to diagnose pulmonary edema based on SpO2 – as pulse oximetry is inexact – rather, to utilize it as a tool to determine which divers require further evaluation before returning to deep freediving.

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Accuracy of Pulse Oximetry in the Presence of Fetal Hemoglobin—A Systematic Review

Children ◽

10.3390/children8050361 ◽

2021 ◽

Vol 8 (5) ◽

pp. 361

Author(s):

Ena Pritišanac ◽

Berndt Urlesberger ◽

Bernhard Schwaberger ◽

Gerhard Pichler

Keyword(s):

Pulse Oximetry ◽

Neonatal Intensive Care ◽

English Language ◽

Arterial Oxygen Saturation ◽

Fetal Hemoglobin ◽

Arterial Oxygen ◽

Cochrane Library ◽

Preterm Neonates ◽

Neonatal Blood ◽

The Impact

Continuous monitoring of arterial oxygen saturation by pulse oximetry (SpO2) is the main method to guide respiratory and oxygen support in neonates during postnatal stabilization and after admission to neonatal intensive care unit. The accuracy of these devices is therefore crucial. The presence of fetal hemoglobin (HbF) in neonatal blood might affect SpO2 readings. We performed a systematic qualitative review to investigate the impact of HbF on SpO2 accuracy in neonates. PubMed/Medline, Embase, Cumulative Index to Nursing & Allied Health database (CINAHL) and Cochrane library databases were searched from inception to January 2021 for human studies in the English language, which compared arterial oxygen saturations (SaO2) from neonatal blood with SpO2 readings and included HbF measurements in their reports. Ten observational studies were included. Eight studies reported SpO2-SaO2 bias that ranged from −3.6%, standard deviation (SD) 2.3%, to +4.2% (SD 2.4). However, it remains unclear to what extent this depends on HbF. Five studies showed that an increase in HbF changes the relation of partial oxygen pressure (paO2) to SpO2, which is physiologically explained by the leftward shift in oxygen dissociation curve. It is important to be aware of this shift when treating a neonate, especially for the lower SpO2 limits in preterm neonates to avoid undetected hypoxia.

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Accuracy of two pulse-oximetry measurements for INTELLiVENT-ASV in mechanically ventilated patients: a prospective observational study

Scientific Reports ◽

10.1038/s41598-021-88608-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Shinshu Katayama ◽

Jun Shima ◽

Ken Tonai ◽

Kansuke Koyama ◽

Shin Nunomiya

Keyword(s):

Oxygen Saturation ◽

Pulse Oximetry ◽

Prospective Observational Study ◽

Arterial Oxygen Saturation ◽

Arterial Oxygen ◽

Arterial Blood Gas ◽

Mechanically Ventilated ◽

Mechanically Ventilated Patients ◽

Arterial Blood ◽

Ventilated Patients

AbstractRecently, maintaining a certain oxygen saturation measured by pulse oximetry (SpO2) range in mechanically ventilated patients was recommended; attaching the INTELLiVENT-ASV to ventilators might be beneficial. We evaluated the SpO2 measurement accuracy of a Nihon Kohden and a Masimo monitor compared to actual arterial oxygen saturation (SaO2). SpO2 was simultaneously measured by a Nihon Kohden and Masimo monitor in patients consecutively admitted to a general intensive care unit and mechanically ventilated. Bland–Altman plots were used to compare measured SpO2 with actual SaO2. One hundred mechanically ventilated patients and 1497 arterial blood gas results were reviewed. Mean SaO2 values, Nihon Kohden SpO2 measurements, and Masimo SpO2 measurements were 95.7%, 96.4%, and 96.9%, respectively. The Nihon Kohden SpO2 measurements were less biased than Masimo measurements; their precision was not significantly different. Nihon Kohden and Masimo SpO2 measurements were not significantly different in the “SaO2 < 94%” group (P = 0.083). In the “94% ≤ SaO2 < 98%” and “SaO2 ≥ 98%” groups, there were significant differences between the Nihon Kohden and Masimo SpO2 measurements (P < 0.0001; P = 0.006; respectively). Therefore, when using automatically controlling oxygenation with INTELLiVENT-ASV in mechanically ventilated patients, the Nihon Kohden SpO2 sensor is preferable.Trial registration UMIN000027671. Registered 7 June 2017.

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Effect of prolonged exercise on arterial oxygen saturation in athletes susceptible to exercise-induced hypoxemia

Scandinavian Journal of Medicine and Science in Sports ◽

10.1111/j.1600-0838.2006.00563.x ◽

2006 ◽

Vol 0 (0) ◽

pp. 061120070736032-??? ◽

Cited By ~ 2

Author(s):

I. B. Stewart ◽

R. L. Pickering

Keyword(s):

Oxygen Saturation ◽

Prolonged Exercise ◽

Arterial Oxygen Saturation ◽

Arterial Oxygen ◽

Exercise Induced

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Nocturnal oxyhemoglobin desaturation during sleep in congestive heart failure patients

Fisioterapia em Movimento ◽

10.1590/1980-5918.029.003.ao18 ◽

2016 ◽

Vol 29 (3) ◽

pp. 597-606

Author(s):

Jéssica Julioti Urbano ◽

Lilian Nanami Uchiyama ◽

Anderson Soares Silva ◽

Roger André Oliveira Peixoto ◽

Sergio Roberto Nacif ◽

...

Keyword(s):

Heart Failure ◽

Congestive Heart Failure ◽

Sleep Apnea ◽

Pulse Oximetry ◽

Arterial Oxygen Saturation ◽

Central Sleep Apnea ◽

Arterial Oxygen ◽

Sleep Breathing Disorders ◽

Breathing Disorders ◽

Obstructive Sleep

Abstract Introduction: Sleep breathing disorders occur in 45% of patients with heart failure, with 36%-50% manifesting Cheyne-Stokes respiration with central sleep apnea and 12% exhibiting obstructive sleep apnea. Several studies have shown that sleep pathophysiology may negatively affect the cardiovascular system and that cardiac dysfunction alters sleep and respiration. Objective: The aim of this study was to examine oxyhemoglobin desaturation during sleep in patients with congestive heart failure (CHF) using overnight pulse oximetry. Methods: Overnight pulse oximetry was conducted in the patients' homes with wrist pulse oximeters and finger probes that were placed around the forefingers of 15 patients with CHF and ejection fractions less than 50%, who were classified as New York Heart Association functional classes II and III. Results: The patients were divided into two groups. The first group consisted of seven patients with oxyhemoglobin desaturation indices of over 5 events/h, and the second group contained eight patients with oxyhemoglobin desaturation indices of 5 or less events/h. Student's t-tests did not show any significant differences between the groups. The patients' body mass indices correlated positively with the total desaturation episodes and desaturation time less than 90% and correlated negatively with the arterial oxygen saturation nadir. Conclusion: Pulse oximetry monitoring during sleep can be used to detect sleep breathing disorders in stable patients with CHF.

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